Systems, apparatus, and methods for temperature compensation in fiber Bragg grating sensing systems that can be implanted in devices.

Abstract

This article describes a method for determining changes in myocardial strain in a subject. The method may include receiving a first signal representing changes in myocardial strain and body temperature sensed by an FBG sensor, receiving a temperature signal representing changes in body temperature sensed by a temperature sensor, and determining changes in myocardial strain based on the first signal and the temperature signal.

Description

[0001] Government support

[0002] This invention was developed with government support from the National Institutes of Health (NIH), license number 1R41HL156482-01A1. The government owns certain rights to this invention. Technical Field

[0003] This invention generally relates to the field of fiber Bragg grating sensing systems for implantable devices. Specifically, this invention relates to temperature compensation in fiber Bragg grating sensing systems. Background Technology

[0004] Fiber Bragg Grating (FBG) sensors are widely used to measure physical signals representing parameters such as temperature, pressure, and strain, and are applicable to a wide range of industries, from civil engineering to aerospace engineering. However, despite the ubiquity and compactness of FBG sensor technology, its adoption in small devices has been challenging, especially its integration into such devices to measure physical signals with lower measurement frequencies and a wider range of values.

[0005] The challenges associated with incorporating FBG sensor technology into small devices (e.g., implantable devices) are typically related to, but not limited to, the physical size and power limitations of FBG demodulators (e.g., in battery-powered devices). An FBG demodulator is a photoelectric measurement unit that provides a light source to an FBG sensor and converts the optical signals received from the FBG sensor into electrical signals, thereby enabling the measurement of the physical signals sensed by the FBG sensor.

[0006] Some implantable medical devices are configured to monitor physiological or pathophysiological conditions and therefore may require the measurement of physical signals associated with those conditions. Typically, these physical signals fall within a low measurement frequency range (e.g., less than 100 Hz). For example, cardiac motion measurements during a cardiac cycle can occur at less than 5 Hz. For low measurement frequency applications, conventional FBG demodulators typically utilize Fabry-Perot interferometers, broadband light sources, and other optical components to acquire sensor data and measure physical signals. While Fabry-Perot interferometers can provide reliable and accurate measurements of physical signals at lower measurement frequencies and over a wide range of values, they are bulky. Furthermore, the broadband light sources utilized by these low-measurement-frequency FBG demodulators can increase the physical size of the FBG demodulator and potentially increase power consumption.

[0007] Several FBG demodulators exist for high-frequency measurement applications, such as hydrophones and seismological applications. However, high-frequency measurement FBG demodulators are specifically designed to measure physical signals with high measurement frequencies but typically narrow ranges of values. More specifically, such FBG demodulators are generally not expected to measure a wide range of values, such as a wide range of strain values. Typically, mechanical events in biological subjects or systems have low measurement frequency ranges and relatively large values. For example, motion measurements of a part of the heart (such as the motion of the ventricular walls during the cardiac cycle) may occur at frequencies less than 5 Hz and have relatively large values ​​within a few millimeters to a few centimeters.

[0008] Therefore, small-sized FBG demodulators are needed to allow for integration into implantable medical devices (e.g., battery-powered implantable medical devices). Furthermore, low-power FBG demodulators are required. Reduced heat generation and long lifespan (e.g., at least 5 years or even more than 10 years) after implantation will be beneficial for these implantable medical device FBG demodulators. Additionally, low power consumption is essential for minimizing the physical size of the FBG demodulator, as the battery is the largest component in an implantable medical device. For example, the battery can account for up to 30-40% of the volume of an implantable cardioverter-defibrillator (ICD).

[0009] Furthermore, FBG demodulators incorporated into implantable medical devices may need to account for and correct for temperature variations. More specifically, implantable medical devices inserted into a subject may be exposed to significant temperature changes due to variations in the subject's body temperature. As mentioned above, FBG sensors are capable of measuring more than one type of physical signal (e.g., temperature, pressure, strain, etc.). In other words, the same FBG sensor can simultaneously sense changes in temperature and strain. That is, the light signal received from the same FBG sensor can represent changes in both temperature and strain. Therefore, FBG demodulators incorporated into implantable medical devices may need to compensate for temperature variations in order to accurately measure changes in strain. Summary of the Invention

[0010] This document describes a physically small (“small”) fiber Bragg grating (FBG) demodulation system. The physical size can be reduced by eliminating bulky optical filters from the system and instead using a light source and FBG sensor that match the spectral range and width within the discrimination spectral domain. Without bulky optical filters, the demodulator portion of the system, such as the light source, photodetector, optocoupler, and related components (e.g., processor, power supply, power management unit), can be implantable in a subject. For example, the FBG demodulation system can be included in various implantable devices such as implantable cardioverter-defibrillators. A power management unit can also be included in the FBG demodulation system to control power usage in order to extend the system's lifespan. For example, the power management unit can be configured to operate in an event-triggered mode, where the system's light source and / or powered components can be turned on (e.g., automatically) upon triggering an event (e.g., cardiac arrhythmia).

[0011] An FBG demodulation system may include at least one light source having an emitted spectrum and at least one FBG sensor having a reflected spectrum, the FBG sensor being configured to receive an optical signal from the at least one light source. The at least one light source and the at least one FBG sensor may be configured such that the emitted spectrum and the reflected spectrum interact in a discrimination spectral domain. In some cases, and in response to a shift in the reflected spectrum of the at least one FBG sensor, the power of the reflected optical signal may monotonically vary in the discrimination spectral domain.

[0012] The FBG sensor can also be configured to generate a reflected light signal representing a change in a physical signal sensed by at least one FBG sensor. Additionally, the FBG demodulation system may include a photodetector optically coupled to at least one FBG sensor, configured to convert the reflected light signal into an electrical signal. Changes in the electrical signal can indicate changes in the physical signal. The physical signal can be strain, temperature, pressure, or a combination thereof.

[0013] A power management unit (PMU) for controlling the activation (e.g., on / off) of a light source and / or other powered components may also be included in the FBG demodulation system. The PMU may be electrically coupled to at least one light source and, optionally, electrically coupled to at least one powered component of the system. In other words, the PMU may be electrically coupled to the at least one light source, at least one powered component of the system, or both the at least one light source and at least one powered component of the system. Exemplary powered components may be preamplifiers, amplifiers, and / or analog-to-digital converters. In one variation, the PMU may be configured to automatically control the light source and / or other powered components. In another variation, the PMU may be manually controlled and configured to turn on at least one light source in response to a user request. In yet another variation, the PMU may be configured for both automatic and manual control. In some variations, the PMU may include one or more processors configured to operate in an event-triggered mode, an event-gated mode, a pulse-width modulation mode, an adaptive power mode, or a combination thereof. When in event-triggered mode, one or more processors can be configured to automatically turn on at least one light source in response to a detected event (e.g., arrhythmia).

[0014] The light source that can be included in the FBG demodulation system can have a bandwidth ranging from about 0.1 nm to about 1.5 nm, including all values ​​and subranges therein. For example, the bandwidth of the light source can be about 0.1 nm, about 0.2 nm, about 0.25 nm, about 0.50 nm, about 0.75 nm, about 1.0 nm, about 1.25 nm, or about 1.5 nm. In some variations, the length of the light source can be less than about 10 mm, and the diameter of the light source can be less than about 6 mm. Various light sources can be used. For example, the light source can be a doped semiconductor, a narrowband laser diode, a quantum dot, or a vertical-cavity surface-emitting laser. The narrowband laser diode can be a distributed feedback diode or a distributed Bragg reflector laser diode.

[0015] The FBG sensor that can be included in the FBG demodulation system may have a bandwidth between about 0.1 nm and about 15.25 nm, including all values ​​and subranges therein. For example, the bandwidth of an FBG sensor can be approximately 0.25 nm, approximately 0.75 nm, approximately 1.25 nm, 1.75 nm, approximately 2.25 nm, approximately 2.75 nm, approximately 3.25 nm, approximately 3.75 nm, approximately 4.25 nm, approximately 4.75 nm, approximately 5.25 nm, approximately 5.75 nm, approximately 6.25 nm, approximately 6.75 nm, approximately 7.25 nm, approximately 7.75 nm, approximately 8.25 nm, approximately 8.75 nm, approximately 9.25 nm, approximately 9.75 nm, approximately 10.25 nm, approximately 10.75 nm, approximately 11.25 nm, approximately 11.75 nm, approximately 12.25 nm, approximately 12.75 nm, approximately 13.25 nm, approximately 13.75 nm, approximately 14.25 nm, approximately 14.75 nm, or approximately 15.25 nm. In some variations, the diameter of the FBG sensor is less than approximately 250 μm. In another variation, the FBG sensor can be a non-uniform FBG sensor. In one variation, the FBG sensor can be a chirped FBG sensor.

[0016] As further described herein, the discrimination spectral domain can be a region defined by at least one of a first portion of the emission spectrum from at least one light source and a second portion of the reflection spectrum from at least one FBG sensor. When the discrimination spectral domain is defined by the first portion of the emission spectrum from at least one light source, the at least one light source can be a vertical-cavity surface-emitting laser.

[0017] The width of the discrimination spectral domain can be based at least in part on the operating range of at least one FBG sensor. The operating range of at least one FBG sensor can be between about 0.5 nm and about 15 nm, including all values ​​and sub-ranges therein. For example, the operating range of at least one FBG sensor can be about 0.5 nm, about 1.0 nm, about 1.5 nm, about 2.0 nm, about 2.5 nm, about 3.0 nm, about 3.5 nm, about 4.0 nm, about 4.5 nm, about 5.0 nm, about 5.5 nm, about 6.0 nm, about 6.5 nm, about 7.0 nm, about 7.5 nm, about 8.0 nm, about 8.5 nm, about 9.0 nm, about 9.5 nm, about 10 nm, about 10.5 nm, about 11 nm, about 11.5 nm, about 12 nm, about 12.5 nm, about 13 nm, about 13.5 nm, about 14 nm, about 14.5 nm, or about 15 nm. When the discrimination spectral domain is a region defined by a second portion of the reflected spectrum, the width and monotonic gradient of the discrimination spectral domain can be based at least in part on the arrangement of multiple Bragg gratings of at least one FBG sensor. This arrangement may include increasing the number of Bragg gratings of the FBG sensor, decreasing the number of Bragg gratings of the FBG sensor, or a gradual, periodic variation of the Bragg gratings.

[0018] The FBG demodulation system described herein can be coupled to a variety of devices suitable for implantation in subjects. For example, the FBG demodulation system can be coupled to an implantable cardioverter-defibrillator (ICD). The FBG sensor can be coupled to a leadless ICD or embedded in a lead within the ICD. In some variations, the ICD may include at least one processor configured to receive electrocardiogram (ECG) signals from at least one electrode disposed in the subject and to detect cardiac arrhythmias in the subject based on the ECG signals.

[0019] This document also describes various implantable cardiac devices including FBG demodulation systems. In one example, an implantable cardiac device may include a lead configured for cardioversion, defibrillation, or pacing, wherein the lead is embedded with at least one fiber Bragg grating (FBG) sensor. The at least one FBG sensor may be configured to receive an optical signal from a light source, interact with the spectrum emitted by the light source in the discrimination spectral domain, and generate a reflected optical signal representing a change in the physical signal sensed by the FBG sensor. Additionally, the implantable cardiac device may include an interface unit coupled to the lead and an optocoupler disposed within the interface unit. The optocoupler may include a light source, a photodetector for converting the reflected optical signal into an electrical signal, and a processor configured to analyze the electrical signal received from the photodetector and, based on the analysis, control the functionality of the implantable cardiac device. The processor may be coupled to a power management unit (PMU). The PMU may be configured to operate in an event-triggered mode, an event-gated mode, a pulse-width modulation mode, an adaptive power mode, or a combination thereof, as further described herein. In some variants, it may be useful for the PMU to operate in event-triggered mode and automatically turn on the light source and / or other power supply components in response to a detected arrhythmia (e.g., ventricular tachycardia). Arrhythmias can be detected based on analysis of electrograms and optionally on myocardial strain sensed by at least one FBG sensor, as further described below. In other words, arrhythmias can be detected based on analysis of electrograms, on myocardial strain sensed by at least one FBG sensor, or both.

[0020] In some variations, a miniaturized fiber Bragg grating (FBG) demodulation system may include: at least one light source, at least one FBG, and a photodetector. The at least one FBG may be configured to: receive an optical signal from the at least one light source, interact with the emitted spectrum of the at least one light source in a discrimination spectral domain, and generate a reflected optical signal representing a change in the physical signal sensed by the at least one FBG. The discrimination spectral domain may be a region defined by at least one of a first portion of the emitted spectrum of the at least one light source and a second portion of the reflected spectrum of the at least one FBG. The width of the discrimination spectral domain may be at least partially based on the operating range of the at least one FBG. The power of the reflected optical signal may monotonically vary in the discrimination spectral domain in response to a shift in the reflected spectrum of the at least one FBG. The photodetector may be optically coupled to the at least one FBG to convert the reflected optical signal into an electrical signal. Measurement of the electrical signal may indicate a change in the physical signal.

[0021] In some variations, the discrimination spectral domain may be defined by a second portion of the spectrum reflected by at least one FBG. The width and monotonic gradient of the discrimination spectral domain may be based at least in part on the arrangement of the Bragg gratings of the at least one FBG. In some variations, this arrangement may include increasing the number of Bragg gratings in the first period to increase the power of the reflected optical signal at the first wavelength, and decreasing the number of Bragg gratings in the second period to decrease the power of the reflected optical signal at the second wavelength, thereby widening the discrimination spectral domain of the spectrum reflected by the at least one FBG.

[0022] In some variations, the discrimination spectral domain may be defined by a second portion of the spectrum reflected by at least one FBG. The period of the Bragg grating of the at least one FBG may be gradually varied. In some variations, the discrimination spectral domain may be defined by a first portion of the spectrum emitted by at least one light source. The at least one light source may be a vertical-cavity surface-emitting laser.

[0023] In some variations, the physical signal can be at least one of strain, temperature, and pressure. In some variations, a miniaturized FBG demodulation system can be configured for low-frequency measurements. In some variations, the length of at least one light source can be less than 10 mm, and the diameter of at least one light source can be less than 6 mm. In some variations, the size of at least one FBG can be less than 250 μm. In some variations, the lifetime of the miniaturized FBG demodulation system can be at least 5 years or at least 10 years.

[0024] In some variations, the miniaturized FBG demodulation system can be coupled to a processor configured to automatically turn on at least one light source in response to a physical condition that meets at least one threshold criterion. In some variations, the miniaturized FBG demodulation system can be coupled to a processor configured to automatically turn on at least one light source at predetermined intervals. In some variations, the miniaturized FBG demodulation system can be coupled to a processor configured to turn on at least one light source in response to a request from a user.

[0025] In some variations, the miniaturized FBG demodulation system can be coupled to an implantable cardioverter-defibrillator (ICD). For example, the miniaturized demodulation system can be coupled to a leadless ICD. At least one FBG can be embedded in the lead of the ICD. In some variations, the ICD may include at least one processor for: receiving electrocardiogram (ECG) signals from at least one electrode disposed in the subject, and detecting arrhythmias in the subject based on the ECG signals. In response to the detection of tachycardia arrhythmias in the subject, the at least one processor may be further configured to send a command to turn on at least one light source. In some variations, the ICD may include at least one processor for: receiving an impedance signal representing at least one of measurements of pulmonary water content and vascular pressure in the subject, and detecting the likelihood of heart failure based on the impedance signal. In response to the detection of the likelihood of heart failure, the at least one processor may also be configured to send a command to turn on at least one light source.

[0026] In some variations, at least one FBG may be a first FBG, and the miniaturized FBG demodulation system may further include a second FBG optically coupled to at least one light source. The second FBG may be configured to modulate the at least one light source such that the emitted spectrum comprises multiple spectral segments. In some variations, at least one FBG may comprise multiple FBGs. In some variations, multiple FBGs may be formed on a single optical fiber. In some variations, the emitted spectrum of at least one light source may comprise multiple spectral segments. In some variations, each of the multiple spectral segments may include a corresponding first end with a first descent slope and a corresponding second end with a second descent slope. In some variations, each of the multiple spectral segments may be configured to interact with the corresponding reflected spectrum of each of the multiple FBGs in a corresponding discriminative spectral domain. In some variations, the at least one light source may comprise multiple light sources. In some variations, each of the multiple FBGs may receive a corresponding optical signal from a corresponding light source among the multiple light sources.

[0027] In some variations, at least one light source may be a doped semiconductor. In some variations, at least one light source may include a wavelength filter. In some variations, at least one light source may be a narrowband laser diode. A narrowband laser diode may be a distributed feedback diode. A narrowband laser diode may be a distributed Bragg reflector laser diode. In some variations, at least one light source may be a quantum dot. In some variations, at least one light source may be a vertical-cavity surface-emitting laser.

[0028] In some variations, the miniaturized FBG demodulation system can be coupled to a processor configured to operate the miniaturized FBG demodulation system in at least a first power management mode, a second power management mode, a third power management mode, a fourth power management mode, and a fifth power management mode. In the first power management mode, the power delivered to the light source and optionally powered components can be continuous. In the second power management mode, the processor can be configured to automatically turn on at least one light source and optionally powered components at predetermined intervals in response to a physical condition meeting at least one threshold criterion, or in response to a request from a user. In the third power management mode, at least one light source and optionally powered components can be configured to turn on and off at least partially based on repetitive physical events. In the fourth power management mode, the power transmitted to the light source and optionally powered components can be in the form of discrete pulses. In the fifth power management mode, the amount of power transmitted to the light source and optionally powered components can be adaptively adjusted to optimize power consumption.

[0029] In some variations, the implantable cardiac device may include: a lead for cardioversion, defibrillation, or pacing and for sensing electrical heart signals (EGM); a pulse generator; and a lead-generator interface unit coupled to the lead and the pulse generator. The lead may embed at least one fiber Bragg grating (FBG) sensor. The FBG sensor may be configured to receive an optical signal from a light source, interact with the spectrum emitted by the light source in the discrimination spectral domain, and generate a reflected optical signal representing a change in the physical signal sensed by the FBG sensor. The lead-generator interface unit may include: an optocoupler including a light source; a photodetector for converting the reflected optical signal into an electrical signal; and a processor for analyzing the electrical signal received from the photodetector, reducing and / or optimizing power consumption via a power management unit (PMU) according to at least five power management modes described above, and controlling the functionality of the implantable cardiac device based on the analysis.

[0030] In some variations, the discrimination spectral domain may be a region defined by at least one of a first portion of the emission spectrum of at least one light source and a second portion of the reflection spectrum of at least one FBG, the width of the discrimination spectral domain may be at least partially based on the operating range of the FBG, and the power of the reflected light signal may monotonically vary in the discrimination spectral domain in response to a shift in the reflected spectrum of the FBG.

[0031] In some variations, the implantable cardiac device may also include a pulse generator coupled to an interface unit and leads to deliver current or energy for cardioversion, defibrillation, and / or pacing. In some variations, at least a portion of an optocoupler may be disposed within the pulse generator. In some variations, a processor may be disposed within the pulse generator. In some variations, the interface unit may be integrated into the pulse generator.

[0032] In some variations, the processor can be configured to: assess the subject's hemodynamic state based on electrical signals from a photodetector, and in response to determining that the state is stable, prevent electrical energy from discharging from a capacitor included in the generator to the subject through wires. In some variations, the processor can be configured to: assess the subject's hemodynamic state based on electrical signals from a photodetector, and in response to determining that the state is stable, prevent electrical energy from being transferred from a battery included in the generator to the capacitor.

[0033] In some variations, the processor can be configured to automatically turn on the light source in response to detecting at least one of a rapid arrhythmia, the possibility of heart failure, and ischemia in the subject, and to assess the subject's hemodynamic status based on electrical signals from a photodetector. In some variations, the processor can be configured to receive electrocardiogram (ECG) signals from electrodes placed in the subject, and to automatically turn on the light source at least partially based on the ECG signals. In some variations, the processor can be configured to automatically turn on the light source in response to a physical condition that meets at least one threshold criterion. In some variations, the processor can be configured to automatically turn on the light source at predetermined time intervals. In some variations, the processor can be configured to automatically turn on the light source in response to a request from a user.

[0034] This paper also describes a method for using an FBG demodulation system. Typically, this method may include selecting a light source and an FBG sensor such that a first portion of the emitted spectrum of the light source interacts with a second portion of the reflected spectrum of the FBG sensor in a discrimination spectral domain. An optical signal is emitted via the light source; a reflected optical signal representing a change in the physical signal sensed by the FBG sensor is received from the FBG sensor; and the reflected optical signal is converted into an electrical signal at a photodetector, wherein the measurement of the electrical signal indicates a change in the physical signal. The width of the discrimination spectral domain may be at least partially based on the operating range of the FBG. The power of the reflected optical signal may monotonically vary in the discrimination spectral domain in response to a shift in the reflected spectrum of the FBG. The method may also include using a power management unit (PMU) to reduce the power consumption of the FBG demodulation system.

[0035] In some variations, the method may include: selecting at least one of a light source and a fiber Bragg grating (FBG), such that a first portion of the emission spectrum of the light source is configured to interact with a second portion of the reflected spectrum of the FBG in a discriminative spectral domain; emitting an optical signal via the light source; receiving a reflected optical signal representing a change in a physical signal sensed by the FBG from the FBG optically coupled to the light source; and converting the reflected optical signal into an electrical signal at a photodetector. Measurement of the electrical signal can indicate a change in the physical signal. The discriminative spectral domain may be a region defined by at least one of the first portion of the emission spectrum of at least one light source and the second portion of the reflected spectrum of at least one FBG. The width of the discriminative spectral domain may be at least partially based on the operating range of the FBG. The power of the reflected optical signal may monotonically vary in the discriminative spectral domain in response to a shift in the reflected spectrum of the FBG.

[0036] In some variations, the implantable cardiac device may include a lead. The lead may embed at least one fiber Bragg grating (FBG) sensor. The FBG sensor may be configured to generate a reflected light signal in response to a received light signal. The reflected light signal may represent a strain change sensed by the FBG sensor and a temperature change sensed by the FBG sensor. The implantable cardiac device may also include a temperature sensor configured to generate a first signal representing a temperature change sensed by the temperature sensor. The implantable cardiac device may also include a processor configured to: determine a strain change based on the reflected light signal generated by the FBG sensor and the first signal generated by the temperature sensor; analyze the strain change; and control the functions of the implantable cardiac device based on the analysis.

[0037] In some variations, the first signal generated by the temperature sensor is a first electrical signal, and the implantable cardiac device may also include a photodetector to convert the reflected light signal into a second electrical signal. The processor can be configured to determine strain changes based on the first and second electrical signals.

[0038] In some variations, the first signal generated by the temperature sensor is a first optical signal. The implantable cardiac device may also include a photodetector to: convert the first optical signal into a first electrical signal, and to convert the reflected optical signal into a second electrical signal. The processor can be configured to determine strain changes based on the first and second electrical signals.

[0039] In some variations, an implantable medical device is inserted into the subject's body, and the strain changes represent changes in the subject's myocardial strain. In some variations, changes in myocardial strain can indicate the subject's hemodynamic status.

[0040] In some variations, the temperature sensor may include a temperature-sensing FBG sensor. In some variations, at least a portion of the temperature sensor may be disposed within a rigid body.

[0041] In some variations, the rigid body can be at least one of a rigid pipe, a rigid cylinder, a rigid hose, a rigid conduit, or a rigid tube. The rigid body may include titanium. The rigid body can be configured to isolate the temperature sensor from strain changes.

[0042] In some variations, a temperature sensor is embedded in the wire. In some variations, the wire may have a temperature sensor embedded at a first location and an FBG sensor embedded at a second location, with the first location adjacent to the second location. In some variations, the first and second locations are spaced apart such that the physical conditions exposed to the sensors (e.g., myocardial strain and / or body temperature) are substantially the same in both locations. In some variations, the first and second locations may be substantially adjacent to each other.

[0043] In some variations, a temperature sensor is embedded in the lead wire. In some variations, the lead wire may embed an FBG sensor at a first location and a temperature sensor at a second location, with the first location adjacent to the second location, and vice versa. In some variations, the first and second locations may be substantially adjacent to each other, such that the temperature exposed to the sensors is substantially the same in both locations. In some variations, the first and second locations are spaced apart from each other, such that the sensors are exposed to substantially the same temperature (e.g., since both the FBG sensor and the temperature sensor are located deep within the subject's body or within blood vessels, and may be exposed to the same core body temperature).

[0044] In some variations, the processor can be configured to access calibration features of the temperature sensor. These calibration features can be generated during the manufacture of the implantable cardiac device or at least prior to implantation of the device, and the temperature sensor is calibrated based on these calibration features generated by the temperature sensor for known temperature variations.

[0045] In some variations, the processor can be configured to access calibration features of the temperature sensor. These calibration features can be generated during the manufacturing process of the implantable cardiac device, or at or immediately before implantation of the implantable cardiac device, and the temperature sensor is calibrated based on calibration features generated by the temperature sensor for known variations in temperature or a set of known variations.

[0046] In some variations, the processor can retrieve calibration features from the memory of the implantable cardiac device. The memory may be included in a temperature compensation unit that includes a temperature sensor. The calibration features can be generated by identifying the output signals of the temperature sensor against known temperature variations. The calibration features may include multiple output signals of the temperature sensor associated with corresponding temperature variations. In some variations, the calibration features may be in the form of a lookup table accessible to the processor. In some variations, the calibration features may be equations and / or a set of equations that associate the output data (e.g., one or more output signals) of the temperature sensor and / or temperature compensation unit with a known set of temperature variations. The equations and / or a set of equations may be derived from the analysis of a known set of temperature variations (e.g., input data) and the output data. In some variations, such analysis may include curve fitting, regression analysis, and / or machine learning techniques and / or artificial intelligence techniques (e.g., neural networks, etc.).

[0047] In some variations, the processor may also be configured to recalibrate the temperature sensor after the implantable cardiac device has been implanted in the subject. Recalibration may be based at least in part on the subject's circadian rhythm of body temperature. In some variations, recalibration may be based at least in part on the subject's core body temperature circadian rhythm of body temperature. As a non-limiting example, core body temperature measurement may be performed invasively (e.g., in the pulmonary artery) and / or non-invasively (e.g., in the rectum) to perform recalibration.

[0048] In some variations, the processor can be configured to determine strain changes based on the occurrence of a physical event. In some variations, the processor can be configured to determine strain changes at a first time point or a first time interval during a physical event. In some variations, the physical event can be a periodic event. A periodic event can be at least one of a cardiac cycle, a respiratory cycle, or a circadian rhythm cycle. In some variations, the processor can be configured to receive signals indicating a physical event.

[0049] In some variations, the processor may be configured to perform temperature compensation based on the occurrence of a physical event. In some variations, the processor may be configured to perform temperature compensation at a first time point during the physical event or within a first time period during the physical event. In some variations, the physical event may be a periodic event. A periodic event may be at least one of a cardiac cycle, a respiratory cycle, or a circadian rhythm cycle of core body temperature. In some variations, the processor may be configured to receive signals indicating a physical event, including but not limited to an electrocardiogram signal indicating a cardiac cycle, a signal derived from a thoracic impedance measurement indicating a respiratory cycle, and / or a signal derived from a measurement of core body temperature in a circadian rhythm cycle indicating core body temperature. As a non-limiting example, such a measurement of core body temperature may be performed invasively (e.g., in the pulmonary artery) and / or non-invasively (e.g., in the rectum).

[0050] In some variations, a method may include receiving a first signal representing changes in myocardial strain and body temperature sensed by an FBG sensor, receiving a second signal representing changes in body temperature sensed by a temperature sensor, and determining changes in myocardial strain based on the first and second signals via a processor.

[0051] In some variations, the implantable cardiac device may include a lead. The lead may embed at least one fiber Bragg grating (FBG) sensor. The FBG sensor may be configured to generate a first reflected light signal in response to changes in myocardial strain and / or temperature. The first reflected light signal may represent a change in myocardial strain sensed by the FBG sensor and / or a change in temperature sensed by the FBG sensor. The implantable cardiac device may also include a first photodetector that converts the first reflected light signal into a first electrical signal. The implantable cardiac device may also include a temperature sensor configured to generate a second electrical signal representing a temperature change sensed by the temperature sensor. The implantable cardiac device may also include a processor configured to: determine a change in myocardial strain based on the first electrical signal generated by the FBG sensor via the first photodetector and the second electrical signal generated by the temperature sensor; analyze the change in myocardial strain; and control the functions of the implantable cardiac device based on the analysis.

[0052] In some variations, the temperature sensor of the implantable cardiac device (e.g., a temperature-sensing FBG sensor) can be configured to generate a second reflected light signal instead of a second electrical signal. The implantable cardiac device may also include a second photodetector to convert the second reflected light signal into a third electrical signal. The processor can be configured to determine changes in myocardial strain based on a first electrical signal generated by the FBG sensor via a first photodetector and a third electrical signal generated by the temperature-sensing FBG sensor via a second photodetector. Attached Figure Description

[0053] Figures 1A-1D An exemplary variant of a miniaturized FBG demodulation system, including an example temperature compensation unit, is shown.

[0054] Figure 2A An exemplary variation of the spectrum emitted by a light source having a single spectral segment is shown.

[0055] Figure 2B An exemplary variation of the spectrum emitted by a light source having multiple consecutive spectral segments is shown.

[0056] Figure 2C An exemplary variation of the emission spectrum of a light source having multiple discontinuous spectral segments is shown.

[0057] Figure 3A An exemplary variation of the spectrum of reflection from an FBG sensor with a single spectral segment is shown.

[0058] Figure 3B An exemplary variation of the spectrum of reflection from an FBG sensor with multiple consecutive spectral segments is shown.

[0059] Figure 4 An exemplary variant of the discriminating spectral domain is shown.

[0060] Figure 5A An exemplary variant of the emission spectrum of a light source and the reflection spectrum of an FBG sensor is shown, wherein the emission spectrum of the light source and the reflection spectrum of the FBG sensor are configured to interact with each other in a discriminative spectral domain defined by the emission spectrum of the light source.

[0061] Figure 5B An exemplary variation of the emission spectrum of the light source and the reflection spectrum of the FBG sensor is shown, wherein the emission spectrum of the light source and the reflection spectrum of the FBG sensor are configured to interact with each other in a discriminative spectral domain defined by the reflection spectrum of the FBG sensor.

[0062] Figures 6A-6E The interaction between the spectrum of an exemplary emission from a light source and the spectrum of an exemplary reflection from an FBG sensor in the discrimination spectral domain is shown.

[0063] Figure 7 This is a flowchart illustrating an exemplary method for miniaturizing an FBG demodulation system.

[0064] Figure 8 An exemplary integration of a miniaturized FBG demodulation system into an implantable medical device is shown.

[0065] Figure 9An exemplary duty cycle of power delivered to the light source and / or powered components is shown when the FBG demodulation system operates in a power-managed pulse width modulation mode to minimize power consumption.

[0066] Figure 10 An exemplary interaction between the spectrum of reflection from the FBG sensor and the spectrum of emission from the two light sources is shown.

[0067] Figures 11A-11C An exemplary integration of a miniaturized FBG demodulation system into a wireless implantable medical device is shown.

[0068] Figures 12A-12E The operation of an exemplary power management unit for a miniaturized FBG demodulation system is shown.

[0069] Figure 13 An exemplary variation of the temperature sensor included in the temperature compensation unit of a miniaturized FBG demodulation system is shown.

[0070] Figures 14A-14C The operation of an exemplary temperature compensation unit in a miniaturized FBG demodulation system is shown, which performs temperature compensation at specific points in time and / or within specific time periods during a physical event in gated temperature compensation mode.

[0071] Figure 15 This is a flowchart illustrating an exemplary method for performing temperature compensation in a miniaturized FBG demodulation system.

[0072] Figure 16 Example frequency domain characteristics of signals representing temperature changes and signals representing strain changes are shown. Detailed Implementation

[0073] This document describes and illustrates, in conjunction with the accompanying drawings, non-limiting examples of various aspects and variations of the invention. The term "subject" or "subjects" as disclosed herein may include human subjects or patients who have been or have been instructed to have an implantable medical device implanted. An "implantable medical device" as disclosed herein may be a small device that can be introduced wholly or partially into a biological subject (e.g., a human subject). An "implantable medical device" as described herein may be used for diagnostic and / or monitoring and / or therapeutic purposes. A "miniaturized fiber Bragg grating (FBG) demodulation system" as disclosed herein may be collectively referred to as an FBG sensor and an associated miniaturized FBG demodulator.

[0074] This document describes systems, devices, and methods for miniaturizing fiber Bragg grating (FBG) demodulators. The techniques disclosed herein can be used in any suitable application, particularly where space is limited. For example, the techniques disclosed herein can be used in implantable medical devices (IMDs), such as implantable pacemakers (IPMs), implantable cardioverter defibrillators (ICDs), implantable cardiac monitors (ICMs), implantable drug pumps, implantable pressure monitors, implantable strain monitors, implantable temperature monitors, etc. In some variations, the miniaturized FBG demodulation system is integrated into the implantable medical device, such as a leaded ICD or a leadless ICD.

[0075] FBG sensors can be used to sense physical signals representing parameters such as temperature, pressure, and strain. An FBG sensor can be formed within an optical fiber by introducing a periodic variation (i.e., a grating) in the refractive index of the fiber core. When light travels through the fiber, the grating reflects light of a specific wavelength. Light of other wavelengths can travel through the fiber unimpeded. When the fiber is exposed to a change in a physical parameter (e.g., a change in a physical signal), this change causes a shift in the wavelength of the reflected light. This shift can be used to measure and / or quantify the amount of change in the physical signal sensed by the FBG sensor (e.g., also referred to as the "sensed physical signal").

[0076] As described above, conventional FBG demodulators used for low measurement frequencies and wide ranges of physical signals can include broadband light sources, filters, interferometers, etc., which make conventional FBG demodulators bulky. Furthermore, conventional FBG demodulators consume significant power (e.g., at least in part due to the inclusion of broadband light sources). Therefore, FBG sensors have not yet been integrated into implantable medical devices such as ICDs, which are typically small and have limited power supplies (e.g., powered by batteries).

[0077] This paper discloses a miniaturized FBG demodulation system that can be integrated into small devices. For example, the miniaturized FBG demodulation system can be integrated into implantable medical devices, as further described herein. For example, the miniaturized FBG demodulation system can be integrated into an ICD to determine the hemodynamic status of a subject during arrhythmias, to provide a reliable way to eliminate and / or reduce the incidence of inappropriate and / or premature ICD shocks in the subject, and to guide medical treatment based on long-term dynamic monitoring of the subject's hemodynamic status. Inappropriate ICD shocks can refer to ICD discharges caused by misinterpreting electrocardiogram signals of non-fatal arrhythmias or by electrical / electromagnetic noise that mimics fatal or potentially fatal arrhythmias such as ventricular tachycardia and ventricular fibrillation. Premature ICD shocks can refer to ICD discharges during ventricular tachycardia when the subject's hemodynamics are stable, in which case alternative therapies such as antitachycardia pacing (ATP) may be more appropriate than ICD shocks. The miniaturized FBG demodulation system described herein can be energy-efficient. In particular, the miniaturized FBG demodulation system can be configured to consume less power. Additionally or alternatively, the miniaturized FBG demodulation system can be configured to generate minimal heat, and therefore can be suitable for implantation in subjects.

[0078] Furthermore, miniaturized FBG demodulation systems can be configured to compensate for temperature variations within the subject's body. For example, monitoring a subject's hemodynamic status can include precisely determining changes in myocardial strain during cardiac mechanical activity (i.e., contraction and relaxation). In some cases, this can include determining instantaneous myocardial strain measurements, such as the difference between end-diastolic ventricular myocardial strain and end-systolic ventricular myocardial strain, which in turn reflects stroke volume within a single cardiac cycle. Such instantaneous myocardial strain measurements typically occur over a period of fractions of a second. A subject's body temperature typically does not change within such a short timeframe. However, in other cases, monitoring a subject's hemodynamic status can include determining and comparing myocardial strain measurements, such as end-diastolic ventricular myocardial strain, over a day, several days, a week, several months, and / or several years. Over such long periods, a subject's body temperature may vary significantly based on physiological and pathophysiological conditions. Alternatively or additionally, a subject's body temperature may vary due to other conditions, such as hyperthermia, fever, hypothermia, and / or during rapid intravenous infusion of fluids (e.g., saline). In order to determine the precise changes in myocardial strain in these conditions, it may be necessary to take into account and compensate for these temperature changes.

[0079] A miniaturized FBG demodulation system may include a light source for emitting an optical signal, an FBG sensor for generating a reflected optical signal representing a change in a physical signal (e.g., temperature, strain, pressure, etc.), and a photodetector for converting the reflected optical signal into an electrical signal indicating the change in the physical signal. As described above, a miniaturized FBG demodulation system integrated into a small device, such as an implantable medical device, can be configured to measure precise changes in strain (e.g., myocardial strain). However, there may be situations where the subject's body temperature may vary significantly. In this case, the reflected optical signal generated by the FBG sensor can represent both changes in myocardial strain and changes in temperature. To compensate for temperature changes and accurately measure changes in myocardial strain, in some variations, the miniaturized FBG demodulation system may include a temperature compensation unit as further described herein.

[0080] In some variations, the size of the light source in the miniaturized FBG demodulation system can be designed for integration into implantable medical devices, as further described herein. At a higher level, the light source and / or FBG sensor of the miniaturized FBG demodulation system can be configured to interact such that the miniaturized FBG demodulation system is sensitive to changes in the physical signal sensed by the FBG sensor within the operating range of the FBG sensor.

[0081] For example, the light source and / or FBG sensor can be designed such that the spectrum emitted by the light source can interact with the spectrum reflected by the FBG sensor in the discrimination spectral domain, as further described herein. For example, the spectrum emitted by the light source can be configured to overlap and interact with the spectrum reflected by the FBG sensor in the discrimination spectral domain. The discrimination spectral domain can be a region defined by a portion of the spectrum emitted by the light source and / or a portion of the spectrum reflected by the FBG sensor. For example, the discrimination spectral domain can be a region within the spectrum emitted by the light source and / or the spectrum reflected by the FBG sensor. In the discrimination spectral domain, the power of the light signal reflected from the FBG sensor can change monotonically in response to a shift in the spectrum reflected by the FBG sensor (e.g., in response to a change in the physical signal sensed by the FBG sensor). In short, the discrimination spectral domain can be a region in the spectrum emitted by the light source and / or the spectrum reflected by the FBG sensor that may be highly sensitive to changes in the physical signal sensed by the FBG sensor.

[0082] The width of the discrimination spectral domain can be determined based on the operating range of the FBG sensor. In some variations, the width of the discrimination spectral domain can conform to the operating range of the FBG sensor. For example, the minimum width of the discrimination spectral domain can be based on the operating range of the FBG sensor. In some variations, the operating range of the FBG sensor can be determined based on the range of physical signals that the FBG sensor is configured to sense. For example, as a non-limiting example, if a miniaturized FBG demodulation system is configured to measure strain in the heart of a subject, the end-diastolic and end-systolic myocardial strain generated by the mechanical movements (i.e., contraction and relaxation) that the heart may undergo during the cardiac cycle can indicate the boundaries of the range of values ​​of the physical signal (myocardial strain) that the FBG sensor is configured to sense. The operating range of the FBG sensor can be the response of the FBG sensor within the range of that physical signal that the FBG sensor is configured to sense. For example, the operating range of the FBG sensor can include the response of the FBG sensor to end-diastolic myocardial strain and the response of the FBG sensor to end-systolic myocardial strain. Therefore, the emission spectrum of the light source can be configured to interact with the reflected spectrum of the FBG sensor within the operating range of the FBG, enabling the miniaturized FBG demodulation system to be highly sensitive to changes in physical signals within the operating range. The terms "myocardial strain" and "myocardial wall strain" are used interchangeably herein.

[0083] Example System

[0084] Figures 1A-1DAn exemplary variant of a miniaturized FBG demodulation system 100 is shown. The miniaturized FBG demodulation system 100 may include one or more light sources 102, one or more FBG sensors 106, one or more photodetectors 104, optionally one or more adjustable FBGs 110, one or more optical routers 108, a power management unit (PMU) 109, and a temperature compensation unit 115. It should be readily understood that the optical router (e.g., optical router 108) can relay or direct optical signals between different components in the FBG demodulation system 100 and may include components such as optical couplers, optical splitters, optical circulators, optical switches, combinations thereof, etc. The light source 102 may be optically coupled to the FBG sensor 106. The light source 102 can transmit optical signals to the FBG sensor 106. The FBG sensor 106 can receive optical signals from the light source 102 and can generate reflected optical signals representing changes in physical signals (e.g., changes in physical parameters such as strain, vibration, pressure, temperature, etc.). The reflected light signal can be received at the photodetector 104, which is optically coupled to the FBG sensor 106. The photodetector 104 can convert the reflected light signal into an electrical signal. This electrical signal can indicate changes in the physical signal. In this way, the miniaturized FBG demodulation system 100 can measure changes in the physical signal.

[0085] In some variations, the miniaturized FBG demodulation system 100 may include a temperature compensation unit 115 to compensate for changes in temperature (e.g., the subject's body temperature). The temperature compensation unit 115 may include one or more temperature sensors ( Figures 1A-1D (Not shown in the diagram). In some variations, the temperature sensor may include an FBG sensor (e.g., similar to FBG sensor 106). A temperature sensor including an FBG sensor (also referred to herein as a "temperature-sensing FBG sensor") may be configured to be strain-isolated. More specifically, a temperature sensor including a temperature-sensing FBG sensor may be configured to sense temperature changes without sensing strain changes. This will be described in further detail below. Additionally or alternatively, the temperature sensor may include any suitable temperature sensor that is not a temperature-sensing FBG sensor, such as a thermocouple, a resistance temperature detector, a thermistor, a digital temperature sensor, an infrared thermometer, etc.

[0086] Temperature compensation unit 115 can be coupled to processor 112. For example, in variations where the temperature sensor may include non-FBG sensors such as thermocouples, resistance temperature detectors, thermistors, digital temperature sensors, infrared thermometers, etc., temperature compensation unit 115 can be directly coupled (e.g., electrically coupled and / or electronically coupled) to processor 112 (e.g., as shown in the image). Figure 1D(As shown). In a variation where the temperature sensor may include a temperature sensing FBG sensor, the temperature compensation unit 115 may be optically coupled to a photodetector (e.g., Figure 1A-Figure 1B The photodetector 104 and / or Figure 1C The photodetector 104' is in the processor 112, and the photodetector can be electrically and / or electronically coupled to the processor 112.

[0087] In variations of the temperature sensor, including a temperature sensing FBG sensor, the temperature compensation unit 115 can be coupled to the same light source 102 and / or the same photodetector 104, such as... Figure 1A and Figure 1B As shown. For example, in Figure 1A In this embodiment, temperature compensation unit 115 can be coupled to photodetector 104 (and optionally to optical router 108) via optical switch 160. In this example, FBG sensor 106 can also be coupled to photodetector 104 (and optionally to optical router 108) via optical switch 160. Optical switch 160 can be coupled to processor 112. Processor 112 can be configured to control optical switch 160. For example, processor 112 can control optical switch 160 to switch between temperature compensation unit 115 and FBG sensor 106, such that photodetector 104 receives signals (e.g., optical signals) from temperature compensation unit 115 or from FBG sensor 106, respectively. As an example, processor 112 can first control optical switch 160 so that photodetector 104 receives signals (e.g., optical signals) from FBG sensor 106. Then, processor 112 can control the optical switch to perform a switching so that photodetector 104 receives signals (e.g., optical signals) from temperature compensation unit 115. In this way, photodetector 104 can receive optical signals from both FBG sensor 106 and temperature compensation unit 115. Optical switch 106 can be configured to quickly switch between FBG sensor 106 and temperature compensation unit 115.

[0088] In some examples, such as Figure 1B As shown, the temperature compensation unit 115 and the FBG sensor 106 can be coupled to each other (e.g., optically coupled). For example, the temperature-sensing FBG sensor and FBG sensor 106 in the temperature compensation unit can be formed on a single optical fiber, as further described herein. In such an example, the optical signal emitted by the light source 102 can be received by the FBG sensor 106 and the temperature sensor. The FBG sensor 106 and the temperature sensor can generate reflected optical signals received by the photodetector 104. The photodetector 104 can apply wavelength division multiplexing (WDM) to convert the reflected optical signals from the temperature sensor and the reflected optical signals from the FBG sensor 106 into electrical signals.

[0089] In some variations, the temperature compensation unit 115 and the FBG sensor 106 can be coupled to different light sources and photodetectors. For example, such as Figure 1C As shown, temperature compensation unit 115 can be coupled to light source 102', while FBG sensor 106 can be coupled to light source 102. Similarly, temperature compensation unit 115 can be coupled to photodetector 104' (and optionally optical router 108'), while FBG sensor 106 can be coupled to photodetector 104 (and optionally optical router 108). Processor 112 can be configured to receive electrical signals from photodetector 104 and photodetector 104'.

[0090] In some variations, the miniaturized FBG demodulation system 100 may also include a power management unit (PMU) 109, which can be designed to minimize and / or reduce the power consumption of the FBG demodulation system 100. The PMU 109 may be coupled to a light source 102 and / or a photodetector 104. In some variations, the PMU 109 may be coupled to one or more powered components (…). Figures 1A to 1D (not shown in the diagram), such as a preamplifier (e.g., associated with photodetector 104), an amplification component (e.g., associated with photodetector 104), an analog-to-digital converter (e.g., associated with photodetector 104), a filter circuit (e.g., associated with photodetector 104), a temperature compensation unit 115, etc.

[0091] In some variations, one or more components of the temperature compensation unit 115 may be powered on and / or powered off together with the rest of the miniaturized FBG demodulation system 100. In other variations, one or more components of the temperature compensation unit 115 may be powered on and / or powered off independently of the rest of the miniaturized FBG demodulation system 100.

[0092] In some variations, the miniaturized FBG demodulation system 100 may include one or more conditioning FBGs 110 to condition the spectrum emitted by the light source 102, as further described herein. In some variations, the miniaturized FBG demodulation system 100 may include one or more optical routers 108 that guide or relay optical signals between different components of the system 100, such as the light source 102, FBG sensor 106, photodetector 104, and conditioning FBG 110. The miniaturized FBG demodulation system 100 may be communicatively and / or operatively coupled to a processor 112. For example, the processor 112 may be coupled to the light source 102, photodetector 104, temperature compensation unit 115, and PMU 109 to control operation, including turning power on or off one or more electrical components of the miniaturized FBG demodulation system 100. For example, the processor 112 may control power to the light source 102 and photodetector 104 via a power management unit (109), as further described herein. Alternatively or additionally, processor 112 may be configured to tune the wavelength spectrum of light source 102, as further described herein. Alternatively or additionally, processor 112 may be coupled to photodetector 104 to analyze changes in the physical signal measured by miniaturized FBG demodulation system 100.

[0093] light source

[0094] The light source 102 can be configured to generate an optical signal that can be emitted to the FBG sensor 106. Some non-limiting examples of the light source 102 may include a vertical-cavity surface-emitting laser, a doped light-emitting diode (LED) (e.g., an infrared emitter with different arsenic and / or phosphorus doping, a blue / green emitter with different indium doping, etc.), an LED coated with a wavelength filter (e.g., an LED coated with a phosphor or phosphor plate, etc.), a distributed feedback diode, a distributed Bragg reflector diode, a quantum dot, etc.

[0095] The optical signal generated by light source 102 can lie within the emission spectrum of light source 102. The emission spectrum of light source 102 can include one or more spectral segments. These spectral segments can be continuous or discrete. Each spectral segment can include a peak and two slopes, with a slope on each side of the peak. The first slope can be an upward slope on a first side of the peak, such that the intensity of the optical signal can increase with increasing wavelength. The second slope can be a downward slope on a second side opposite to the first side of the peak, such that the intensity of the optical signal can decrease with increasing wavelength. The peak can be a point on the spectral segment. Alternatively or additionally, the peak can be a set of two or more consecutive points, which are continuous with each other to form a plateau region of the spectral segment. In some variations, the first upward slope and the second downward slope can define the boundary of the spectral segment on two opposite sides. In some variations, the upward and downward slopes of the spectral segment can be symmetrical about the peak. In some variations, the upward and downward slopes can be asymmetrical about the peak.

[0096] Figure 2A A light source with a single spectral segment 240a is shown (e.g., Figures 1A to 1D An exemplary variation of the spectrum 232 emitted by the light source 102 in the image. Figure 2A As seen, the emission spectrum of the light source comprises only one spectral segment 240a. Spectral segment 240a may include a peak 240a''', a rising edge 240a' on a first side of the peak 240''', and a falling edge 240a'' on a second side opposite to the first side of the peak 240a'''. As described above, the peak 240a''' may be a point on the spectral segment 240a, or a set of two or more consecutive points that are continuous with each other to form a plateau region of the spectral segment 240a. In some variations, slopes 240a' and 240a'' may define the boundaries of the spectral segment 240a on two opposite sides of the peak 240a'''.

[0097] Figure 2B A light source with multiple spectral segments is shown (e.g., Figures 1A to 1DAn exemplary variation of the emission spectrum 234 of the light source 102 is described. In some variations, the intensity of the light signal from the light source may be zero between two adjacent spectral segments. Additionally or alternatively, the intensity of the light signal from the light source may be non-zero between two adjacent spectral segments. For example, spectral segments 240b, 240c, and 240d may be continuous or discrete with each other. For example, the light source may be optically coupled to one or more regulating FBGs 110 (described in further detail below). One or more regulating FBGs 110 may divide the emission spectrum 234 of the light source into multiple spectral segments. As a non-limiting example, Figure 2B The emission spectrum 234 of the light source comprises three spectral segments 240b, 240c, and 240d. Each spectral segment includes a peak and two slopes (e.g., a rising edge and a falling edge) on each side of the peak. For example, spectral segment 240b includes a peak 240b''' and a rising edge 240b' and a falling edge 240b'' located on the opposite side of peak 240b'''. Similarly, spectral segment 240c includes a peak 240c''' and a rising edge 240c' and a falling edge 240c'' located on the opposite side of peak 240c'''. In a similar manner, spectral segment 240d includes a peak 240d''' and a rising edge 240d' and a falling edge 240d'' located on the opposite side of peak 240d'''. As described above, peaks 240b''', 240c''', and 240d''' can be discrete points on spectral segments 240b, 240c, and 240d, respectively. Alternatively, peaks 240b''', 240c''', and 240d''' can be sets of two or more consecutive points that are continuous with each other to form plateau regions of spectral segments 240b, 240c, and 240d, respectively.

[0098] Figure 2C An exemplary variant of spectrum 236 of emission having multiple spectral segments is shown. As described above, the intensity of the optical signal between two adjacent spectral segments can be zero or non-zero. For example, in Figure 2C In this context, spectral fragments 240e and 240f can be either continuous or discontinuous spectral fragments. For example, a miniaturized FBG demodulation system 100 may include more than one light source (e.g., Figures 1A-1D (Light source 102 in the system). For example, system 100 may include a first light source having an emission spectrum 240e and a second light source having an emission spectrum 240f. The emission spectrum of the combination of the two light sources may be emission spectrum 236. As a non-limiting example, Figure 2CThe emission spectrum 236 of the light source comprises two spectral segments 240e and 240f. Each spectral segment includes a peak and a rising edge and a falling edge on each side of the peak. For example, spectral segment 240e includes a peak 240e''' and a rising edge 240e' and a falling edge 240e'' located on the opposite side of the peak 240e'''. Similarly, spectral segment 240f includes a peak 240f''' and a rising edge 240f' and a falling edge 240f'' located on the opposite side of the peak 240f'''. As described above, peaks 240e''' and 240f''' can be discrete points on spectral segments 240e and 240f, respectively. Alternatively, peaks 240e''' and 240f''' can be a set of two or more consecutive points that are continuous with each other to form plateau regions of spectral segments 240e and 240f, respectively.

[0099] Return to reference Figures 1A to 1D The spectrum emitted by the light source 102 may include a single spectral segment (e.g., Figure 2A Spectral fragment 204a) or multiple spectral fragments (e.g., Figure 2B and Figure 2C (spectral fragments).

[0100] In some variations, the FBG demodulation system 100 may include a single light source 102. In other variations, the FBG demodulation system 100 may include more than one light source 102. The light source 102 may be configured for integration into a small device such as an implantable medical device. For example, the light source 102 described herein may have a small volume. Additionally or alternatively, the light source described herein may be small. For example, the light source 102 may have a small diameter and / or a small length.

[0101] In some variations, the light source 102 may be a laser diode. For example, the light source 102 may be a semiconductor laser diode (e.g., a vertical-cavity surface-emitting laser or a VCSEL, an edge-emitting laser). In some variations, the light source 102 may be a doped light-emitting diode (LED). The LED may be configured to interact with the FBG sensor 106 in the discrimination spectral domain (described in detail below) by means of dopants in the customized LED. Some example dopants may include arsenic, phosphorus, germanium, indium, etc. In some variations, the light source 102 may include a light source coated with one or more wavelength conversion materials, such as an LED coated with a wavelength filter. The light source may be configured to interact with the FBG sensor 106 in the discrimination spectral domain by coating the light source with a wavelength conversion material. Some example wavelength conversion materials may include phosphors, etc. In some variations, the light source 102 may be a laser diode, such as a distributed feedback diode, a distributed Bragg reflector diode, etc. In some variations, the light source 102 may be an electrically driven quantum dot.

[0102] It should be easy to understand. Figure 1C The light source 102' in the middle can be structurally and / or functionally similar to Figures 1A-1D The light source 102 in the middle.

[0103] FBG sensor

[0104] The light source 102 can be optically coupled to the FBG sensor 106. The FBG sensor 106 can be formed within an optical fiber. For example, the core of the optical fiber can be exposed to ultraviolet light to inscribe the grating planes and introduce periodic variations in the refractive index of the core. The distance or spacing between two adjacent grating planes can define the grating period.

[0105] When light is emitted to the FBG sensor 106, the FBG sensor 106 reflects light at specific wavelengths within its reflected spectrum. Changes in the physical signal sensed by the FBG sensor 106 can cause changes in the grating period of the FBG sensor 106. This, in turn, can cause a shift in the wavelength of the reflected light, resulting in a shift in the reflected spectrum. In some variations, the same FBG sensor 106 can sense changes in more than one type of physical signal. For example, the same FBG sensor 106 can sense changes in strain and temperature. Therefore, when the FBG sensor 106 is exposed to changes in strain and significant changes in temperature, a shift in the reflected spectrum can indicate these changes in strain and temperature.

[0106] Similar to the emission spectrum of light source 102, the reflected spectrum of FBG sensor 106 may include one or more spectral segments. For example, the reflected spectrum may include... Figure 3AThe spectral segment of a single reflection is shown. Spectral segment 340a may include a peak 340a''', corresponding to the central Bragg wavelength where reflectance may be at its maximum, and two slopes 340a' and 340a'', one on each side of peak 340a'''. The first slope 340a' can be the rising edge of the first side, where reflectivity increases with increasing wavelength, while the second slope 340" can be the falling edge of the second side of the peak (e.g., opposite to the first side), where reflectivity decreases with increasing wavelength. In some variations, the rising and falling edges can be symmetrical about the peak. In some variations, the rising and falling edges can be asymmetrical about the peak. The peak of the reflected spectral segment can be a single point. Alternatively, the peak can be a set of two or more consecutive points that are continuous with each other, thus forming a plateau region of the reflected spectral segment. In some variations, such a plateau region can be non-smooth or irregular. For example, the reflected spectrum of a chirped FBG sensor can include peaks with irregular plateau regions. In some variations, the reflected spectrum can include multiple reflected spectral segments, such as... Figure 3B As shown. As a non-limiting example, the reflected spectrum 343 of the FBG sensor 106 may include three spectral segments 340b, 340c, and 340d. Each spectral segment (e.g., 340b, 340c, and 340d) includes a peak (e.g., 340b''', 340c''', and 340d''') and two slopes (e.g., 340b' and 340b'', 340c' and 340c'', and 340d' and 340d''), one on each side of the peak. Each peak 340b'', 340c'', or 340d'' of the corresponding reflected spectral segment 340b, 340c'', or 340d'' may be a point. Alternatively, each peak may be a set of two or more consecutive points that are continuous with each other to form a plateau region of the corresponding reflected spectral segment. Similar to... Figure 2C The spectral segments in the emission spectrum of the light source depicted, and the spectral segments in the reflection spectrum of the FBG sensor, can be continuous or discontinuous spectral segments.

[0107] Return to reference Figures 1A-1D In some variations, the FBG sensor 106 of the FBG demodulation system 100 can be designed to optimize the width of the rising and / or falling edges of the reflected spectral segment within the operating range of the FBG sensor 106. The operating range can be determined based on the range of possible values ​​of the physical signal that the FBG sensor 106 is configured to sense. For example, the operating range can be determined by determining the upper boundary / maximum value and the lower boundary / minimum value of the physical signal that the FBG sensor 106 is configured to sense. The response of the FBG sensor 106 to the upper boundary / maximum value and the lower boundary / minimum value can determine the operating range of the FBG sensor 106.

[0108] The FBG sensor 106 can be designed such that the spectrum of its reflection matches the gradient of the rising and / or falling edges of the reflected spectral segment within the operating range of the FBG sensor 106. By matching the spectrum of the FBG sensor 106's reflection, the spectrum of the FBG sensor 106's reflection and the spectrum of the light source 102's emission can be configured to interact, making the FBG demodulation system 100 sufficiently sensitive to changes in the sensed physical signal within its value range.

[0109] Specifically, the FBG sensor 106 can be designed such that the width / gradient of the discriminant spectral domain in the reflected spectrum of the FBG sensor 106 can be modified (described in detail below) to increase the sensitivity of the FBG demodulation system 100. More specifically, the gratings on the FBG sensor 106 can be arranged in a manner that modifies the discriminant spectral domain as described herein. That is, gratings can be formed or inscribed on the optical fiber (e.g., using a laser) to modify the discriminant spectral domain, for example by increasing the number of gratings for certain wavelengths and decreasing the number of gratings for certain other wavelengths on the FBG sensor 106 in a specific manner and / or by increasing and decreasing the space between the gratings on the FBG sensor 106 in a specific manner. This will be described in further detail below.

[0110] In some variations, the sensitivity of the FBG demodulation system 100 can be further improved by designing a discriminant spectral domain (described in detail below) in the spectral segment emitted by the light source 102 and another discriminant spectral domain (described in detail below) in the spectrum reflected by the FBG sensor 106, such that the discriminant spectral domain of the emitted spectral segment of the light source 102 interacts with the discriminant spectral domain of the reflected spectrum of the FBG sensor 106 within the operating range of the FBG sensor 106, in response to changes in the physical signal sensed by the FBG sensor 106. This... Figure 6C It is shown in the figure and explained in further detail below.

[0111] In some variations, the FBG sensor 106 can be a chirped FBG sensor. A chirped FBG sensor can be formed in a Bragg grating with a gradually changing periodicity. This gradually changing periodicity (e.g., grating period) can result in a broad reflectance spectrum. The chirped FBG sensor can be designed to increase the width of the discriminative spectral domain in the reflectance spectrum of the FBG sensor 106.

[0112] The FBG sensor 106 can be configured for integration into small devices. For example, the FBG sensor 106 can have a small diameter and / or a small length. For example, the diameter of the FBG sensor 106 can be about or less than about 250 μm, about or less than about 225 μm, about or less than about 200 μm, about or less than about 175 μm, or about or less than about 150 μm. The length of the FBG sensor 106 can be about or less than about 15 mm, about or less than about 12 mm, about or less than about 10 mm, about or less than about 8 mm, about or less than about 5 mm, or about or less than about 3 mm.

[0113] The FBG demodulation system 100 may include one or more FBG sensors 106. In a variant having more than one FBG sensor 106, each FBG sensor 106 may be configured to independently sense the same physical signal at different locations. Alternatively, in a variant having more than one FBG sensor 106, at least one or more FBG sensors 106 may be configured to sense different physical signals from other FBG sensors 106. For example, a single optical fiber may include multiple FBG sensors 106 (e.g., each grating or a combination of two or more gratings may form a separate FBG sensor 106). In some variants, the FBG demodulation system 100 may include multiple optical fibers. Each optical fiber may be designed to include one or more FBG sensors 106. More than one FBG sensor 106 may allow multi-location and / or multi-point sensing. For example, the FBG demodulation system 100 (e.g., a miniaturized FBG demodulation system integrated into an ICD) may include a first FBG sensor for sensing a physical signal at a first location and a second FBG sensor for sensing a physical signal at a second location. Positioning two or more FBG sensors at different locations within the heart chambers (e.g., right atrium, right ventricle, coronary sinus, left ventricle, etc.) and / or at more than one site within each of the different locations within the heart chambers (e.g., different sites within the coronary sinus) allows the FBG demodulation system 100 to detect asynchrony between different sites and / or locations within the heart (e.g., synergy and / or lack of synchrony between sites or locations within the heart). Additionally, detecting asynchrony can help efficiently detect ventricular tachycardia and associated hemodynamic states. If two or more FBG sensors are located on a single optical fiber, the photodetector 104 can apply wavelength division multiplexing to acquire and measure the response of each FBG sensor to a sensed physical signal or a change in that signal, as further described below. For example, a first FBG sensor may be positioned in the right ventricle, and a second FBG sensor may be positioned in the coronary sinus (e.g., when the miniaturized FBG demodulation system 100 is integrated into an ICD). The first FBG sensor may be configured to sense changes in myocardial strain in the right ventricle, and the second FBG sensor may be configured to sense changes in myocardial strain in the left ventricle.

[0114] Photodetector

[0115] One or more photodetectors 104 may be optically coupled to the FBG sensor 106. The photodetector 104 may be configured to measure changes in a physical signal sensed by the FBG sensor 106. For example, the FBG sensor 106 may receive a light signal emitted from the light source 102. In response to a sensed change in the physical signal, the FBG sensor 106 may generate a reflected light signal in a discrimination spectral domain through the interaction between the emission spectrum of the light source and the reflected spectrum of the FBG sensor, as further described below. The power of the reflected light signal may indicate a quantitative change in the physical signal. The photodetector 104 may convert the reflected light signal into an electrical signal. Measurement of the electrical signal may indicate a change in the physical signal. For example, the photodetector 104 may receive the reflected light signal from the FBG sensor 106 and may convert photons in the reflected light into an electric current. Measurement of the current may indicate a change in the sensed physical signal. The photodetector 104 may be any suitable photodetector. For example, the photodetector 104 may be a semiconductor-based photodetector, such as a photodiode, phototransistor, etc. In some variations, the current may be converted into a voltage. Voltage measurement can indicate changes in the sensed physical signal detected by FBG sensor 106. In a variant of temperature compensation unit 115 that includes a temperature sensor as an FBG sensor (e.g., a temperature-sensing FBG sensor), photodetector 104 can receive reflected light signals from the temperature sensor and convert the reflected light signals into current and / or voltage. The voltage measurement can indicate the temperature change sensed by the temperature sensor.

[0116] In some variations, the miniaturized demodulation system 100 may include more than one photodetector 104. Each photodetector 104 may be coupled to a corresponding FBG sensor 106. The FBG sensor 106 may be positioned at different locations on a single optical fiber. Wavelength division multiplexing (WDM) can be applied to couple the photodetector 104 to the FBG sensor 106, such that the photodetector 104 can receive the reflected spectrum from each FBG sensor 106 on the single optical fiber in response to changes in the physical signal sensed by the FBG sensor 106 at its respective location.

[0117] It should be easy to understand. Figure 1C The photodetector 104' in the middle can be structurally and / or functionally similar to Figures 1A-1D The photodetector 104 in the middle.

[0118] Power Management Unit

[0119] The light source 102 and / or photodetector 104 may be electrically coupled to the power management unit (PMU) 109. In some variations, one or more powered components of the FBG demodulation system 100 (e.g., a preamplifier associated with photodetector 104, an amplifier associated with photodetector 104, an analog-to-digital converter associated with photodetector 104, a filter circuit associated with photodetector 104, etc.) may be electrically coupled to the PMU 109. The term "powered component" may be used collectively to refer to electrically powered components of the FBG demodulation system 100 other than the light source 102, such as, but not limited to, the preamplifier associated with photodetector 104, the amplifier associated with photodetector 104, the analog-to-digital converter associated with photodetector 104, the filter circuit associated with photodetector 104, etc.

[0120] In some variations, PMU 109 can be configured to enable continuous operation of FBG demodulation system 100. In some variations, PMU 109 can be configured to minimize and / or optimize the power consumption of FBG demodulation system 100. More specifically, PMU 109 can be configured to switch FBG demodulation system 100 from an operational state to a sleep state to minimize and / or reduce power consumption. For example, in some variations, FBG demodulation system 100 can be in an operational state when light source 102 is on. In the operational state, FBG demodulation system 100 can be configured to acquire and measure one or more physical signals (e.g., sensed physical signals) that FBG sensor 106 is configured to sense. When light source 102 is off, FBG demodulation system 100 may not measure the physical signals that FBG sensor 106 is configured to sense and may be in a sleep state, thereby saving power. In some variations, the light source 102 and / or the powered components can be intermittently powered on and off via PMU 109, thereby switching the FBG demodulation system 100 from an operational state to a sleep state and vice versa, to minimize and / or reduce power consumption. In some variations, the amount of power (e.g., electrical power) supplied to the light source and / or the powered components can be adjusted (e.g., adaptively adjusted) via PMU 109 to achieve an optimal balance between the power consumed by the FBG demodulation system 100 and the sensitivity and / or accuracy of the FBG demodulation system 100 in sensing physical signals.

[0121] In some variations, the FBG demodulation system 100 described herein can be configured to operate in one or more modes (referred to as "power management modes") that minimize power consumption. In some variations, the light source 102 and / or the powered components can be turned on via PMU 109 based on the power management mode of the FBG demodulation system 100, as further described herein.

[0122] In some variations, PMU 109 may include one or more switches (such as overspeed switches) and one or more power regulation circuits that may be coupled to light source 102 and optionally to powered components. In some variations, light source 102 and / or powered components may be powered on for a defined period of time (e.g., operating period) before being powered off via one or more switches based on a power management mode. For example, a miniaturized FBG demodulation system may be integrated into an implantable medical device (e.g., an ICD). The miniaturized FBG demodulation system 100 integrated into the ICD may have an operating period of about or less than a fraction of a microsecond, about or less than about 10 microseconds, about or less than about 100 microseconds, about or less than a fraction of a millisecond, about or less than about 10 milliseconds, about or less than about 100 milliseconds, about or less than a fraction of a second, about or less than 10 seconds, about or less than 100 seconds, about or less than a fraction of a minute, about or less than 10 minutes, about or less than a fraction of an hour, or about or less than 30 hours. According to the power management mode, the light source and / or the powered component can be powered on via one or more switches during the operation period and can be turned off via one or more switches after the operation period ends.

[0123] In some variations, PMU 109 may include one or more power regulation circuits to regulate the amount of electrical power transmitted to light source 102 and / or powered components. For example, a miniaturized FBG demodulation system 100 may be integrated into an implantable medical device (e.g., an ICD) for the heart to sense myocardial strain in the ventricles. The amount of electrical power transmitted to light source 102 can be reduced via the power regulation circuits, thereby reducing the intensity of the spectrum emitted by light source 102 while the miniaturized FBG demodulation system 100 adequately senses one or more myocardial strain signals in the ventricles, thus accurately determining the hemodynamic stability of the subject with minimal power consumption. Similarly, in some variations, the amount of electrical power transmitted to powered components can be reduced via the power regulation circuits, thereby reducing the gain and / or sampling frequency of FBG demodulation system 100 while the miniaturized FBG demodulation system 100 adequately senses one or more myocardial strain signals in the ventricles, thus accurately determining the hemodynamic stability of the subject with minimal power consumption.

[0124] It should be understood that the physical arrangement or sequence between the switch and the power conditioning circuit can vary. In some variations, the switch may be positioned before the power conditioning circuit for a light source or a powered component. In other variations, the power conditioning circuit may be positioned before the switch for another light source or another powered component.

[0125] In some variations, PMU 109 may include one or more processors to control at least some components of PMU 109 (e.g., switches, power regulation circuitry, etc.). In some variations, PMU 109 may be coupled to one or more processors (e.g., Figures 1A to 1D The processor 112 controls at least some components of the PMU 109 (e.g., switches, power regulation circuitry, etc.). In some variations, the processor can automatically control one or more components of the PMU 109. For example, the processor can control one or more components of the PMU 109 based on a pre-programmed algorithm. Alternatively, the processor can control one or more components of the PMU 109 based on machine learning techniques. In a variation where the FBG demodulation system 100 is integrated into an implantable medical device, the processor can control one or more components of the PMU 109 based on historical and / or real-time data collected by the implantable medical device. In some variations, a user can wirelessly control one or more components of the PMU 109 via the processor.

[0126] The FBG demodulation system 100 can be configured to operate via PMU 109 in at least five power management modes to minimize power consumption. For example, the FBG demodulation system 100 can be configured via PMU 109 to operate in the following modes: continuous mode, event-triggered mode, event-gated mode, pulse width modulation mode (pulse mode), and / or adaptive power mode, as further described herein. In continuous mode, the light source 102 and / or the powered components can be continuously turned on. It should be understood that the terms "continuous" and "continuously" used herein to describe the continuous mode of power management do not explicitly or implicitly indicate that the FBG demodulation system is powered on or turned on without interruption. In some variations, such interruptions may occur when continuous mode is combined with other modes, such as event-gated mode and / or pulse mode as described below.

[0127] In event-triggered mode, the light source 102 and / or the powered component can be turned on (e.g., automatically) by triggering an event, including but not limited to (1) physical events as described herein, (2) pre-programmed intervals, and / or (3) requests from a user. For example, a miniaturized FBG demodulation system 100 can be integrated into an ICD as described herein. In some variations, the light source 102 and / or the powered component can be turned on (e.g., automatically) by triggering an event, such as a physical event including demand events such as tachycardia, heart failure, ischemia, etc. In some variations, the light source 102 and / or the powered component can be turned on (e.g., automatically) at pre-programmed demodulation intervals. Such pre-programmed demodulation intervals can be daily, weekly, monthly, quarterly, or annually, or a portion thereof. In some variations, the light source 102 and / or the powered component can be turned on (e.g., automatically) by triggering an event such as a request from a user. Such a user can be a physician, nurse practitioner, physician assistant, medical technician, etc., with training and professional qualifications to perform such requests. For example, a user can send a request to the FBG demodulation system 100 via a wireless interface or other types of I / O devices to turn on the light source 102 and / or the powered components.

[0128] In some variations, the light source 102 and / or the powered components may remain powered on for a period of time (e.g., an operation period) before automatically shutting off or powering down. During the operation period, the miniaturized FBG demodulation system 100 may acquire and measure one or more physical signals (e.g., sensed physical signals) that the FBG sensor 106 is configured to sense. In some cases, the length or duration of the operation period may be fixed or predetermined. In some variations, the length of the operation period may be dynamically determined based on historical and / or real-time data (e.g., sensed physical signals acquired, sensed, and / or measured by the FBG demodulation system 100) and the amount of power consumed by the FBG demodulation system 100. In some cases, the length or duration of the operation period may be dynamically determined at least in part based on the analysis of physical signals sensed by the FBG sensor by the FBG demodulation system 100 during the current operation period and / or during previous operation periods. In some variations, the length of the operation period can be dynamically determined, at least in part, based on analysis of physical signals detectable by non-FBG sensors, such as electrocardiograms detected by electrodes placed in the heart and / or by separate and additional FBG sensors. For example, the duration of the operation period can be the entire duration of arrhythmia, ischemia, or worsening heart failure, or a portion thereof, or longer than such a duration.

[0129] In some variations, physical events may occur at repetitive intervals (e.g., cardiac cycles, respiratory cycles, etc.). These repetitive physical events may exhibit periodicity that can vary over time. For example, cardiac and respiratory cycles are repetitive events whose periodicity is generally stable. However, there may be time variations in the periodicity of cardiac and respiratory cycles. In a variation where the FBG demodulation system 100 is integrated into an implantable medical device, repetitive physical events occurring at repetitive intervals can be detected by the implantable medical device, as further described herein. As a non-limiting example, cardiac cycles as recurring events can be detected by analyzing electrocardiogram signals transmitted through electrodes in the implantable medical device. As yet another non-limiting example, respiratory cycles as recurring events can be detected by analyzing transthoracic impedance via an impedance sensor in the implantable medical device.

[0130] In response to a recurring physical event, the FBG demodulation system 100 can be configured via PMU 109 to operate in event-gated mode. In event-gated mode, a processor (e.g., a processor within PMU 109 and / or a processor coupled to PMU 109) can actuate a switch (e.g., an overspeed switch) in PMU 109, causing the light source 102 and / or the powered component to be rapidly switched on and off at specific time instances and / or points in time (i.e., gating points) during the recurrence cycle of the recurring event. These gating points can be predetermined. Alternatively, these gating points can be dynamically determined, for example, before, during, or after the recurring physical event. For example, the light source 102 can be switched on (e.g., automatically switched on) at a specific gating point (e.g., predetermined and / or dynamically determined) during the recurring event. After a certain period of time (e.g., an operating period) following the switching on of the light source 102 and / or the powered component, the light source and / or the powered component can be switched off (e.g., automatically switched off). During the operation period when the light source 102 is on, the FBG demodulation system 100 can acquire and measure one or more physical signals (e.g., sensed physical signals) that the FBG sensor 106 is configured to sense. As described above, similar to the event-triggered mode, for the event-gated mode, the length of the operation period from turning the light source on to turning off the light source 102 can be several hours or fractions of an hour, several minutes or fractions of a minute, several seconds or fractions of a second, several milliseconds or fractions of a millisecond, several microseconds or fractions of a microsecond, etc. In some variations, the length of the operation period in the event-gated mode can be fixed or predetermined. In some variations, the length of the operation period in the event-gated mode can be dynamically determined based on historical and / or real-time data (e.g., sensed physical signals acquired, sensed, and / or measured by the FBG demodulation system 100) and the amount of power consumed by the FBG demodulation system 100. In some variations, the length of the operation period for the event-triggered mode and / or event-gated mode can be dynamically determined, at least in part, based on the analysis of sensed physical signals sensed by the FBG demodulation system 100 via FBG sensors during the current operation period and / or recorded during previous operation periods. In some variations, the length of the operation period for the event-triggered mode and / or event-gated mode can be dynamically determined, at least in part, based on the analysis of physical signals detectable by non-FBG sensors and / or by separate and additional FBG sensors. In some variations, the length of the operation period for the event-triggered mode and / or event-gated mode can be dynamically determined, at least in part, based on the analysis of variations in recurring physical events detectable by the FBG demodulation system 100 in the time or frequency domain.

[0131] In some variations, repetitive events may occur repeatedly, for example, at repetition intervals. In some variations, the operating period of the event-triggered mode may not exceed the repetition interval of the repetitive events. For example, the light source 102 and / or the powered component may be switched on at the end of systole of the cardiac cycle (e.g., automatically switched on) and may be switched off after a preset operating period of 50 or 100 milliseconds (e.g., automatically switched off). Similarly, the light source 102 and / or the powered component may be switched on at the end of diastole of the cardiac cycle (e.g., automatically switched on) and may be switched off after a preset operating period of 50 or 100 milliseconds (e.g., automatically switched off). In some variations, the operating period of the event-triggered mode may exceed the repetition interval of the repetitive events. In some variations, the light source 102 and / or the powered components can be switched on at the end of inspiration in the respiratory cycle (e.g., automatically switched on) and switched off after a dynamically determined operating period, such as an operating period equal to two or three cardiac cycles, based on analysis of motion measurements of a portion of the heart, such as ventricular wall motion sensed by the FBG demodulation system 100 via an FBG sensor, and / or analysis of electrocardiogram signals transmitted through electrodes (non-FBG sensors). Similarly, the light source 102 can be switched on at the end of expiration in the respiratory cycle (e.g., automatically switched on) and switched off after a dynamically determined operating period, such as an operating period equal to two or three cardiac cycles, based on analysis of motion measurements of a portion of the heart, such as ventricular wall motion sensed by the FBG demodulation system 100 via an FBG sensor, and / or analysis of electrocardiogram signals transmitted through electrodes (non-FBG sensors).

[0132] In some variations, the FBG demodulation system 100 can be configured via PMU 109 to operate in pulse width modulation mode or pulse mode. In pulse mode, the power delivered to the light source 102 and / or the powered component can be in the form of discrete pulses. These discrete pulses can turn the light source 102 and / or the powered component on and off in a discrete manner. The discrete manner in which the light source 102 and / or the powered component can be turned on and off can be based on the duty cycle of the voltage / current signal and / or clock that controls the power delivered to the light source 102 and / or the powered component. For example, the power delivered to the light source 102 and / or the powered component can be expressed in the form of a duty cycle, which can indicate the ratio of the time the light source 102 and / or the powered component can be turned on to the time the light source 102 can be turned off. Figure 9An example duty cycle is shown for the power delivered to the light source 102 and / or the powered component when the FBG demodulation system 100 operates in a power-managed pulse width modulation mode. For example, duty cycle 992 has a pulse time interval of 50%. In other words, the power delivered to the light source 102 and / or the powered component may cause the light source 102 and / or the powered component to be turned on for 50% of the time and off for 50% of the time. Similarly, duty cycle 994 has a pulse time interval of 75%, such that the power delivered to the light source 102 and / or the powered component turns on the light source 102 and / or the powered component for 75% of the time and turns off the light source 102 and / or the powered component for 25% of the time. Similarly, the duty cycle 996 has a 25% pulse time interval, causing the power delivered to the light source 102 and / or the powered component to turn on the light source 102 and / or the powered component for 25% of the time and turn off the light source 102 and / or the associated powered component for 75% of the time. In some variations, the duty cycle can be pre-programmed, or optionally, dynamically determined based on the analysis of the amplitude of the physical signal sensed by the FBG sensor 106 or the output amplitude of the photodetector 104, as described below. It should be readily understood that the amplitude of the physical signal sensed by the FBG sensor 106 and the output amplitude of the photodetector 104 are highly correlated with each other.

[0133] In some variations, the discrete form of the pulsed power delivered to the light source 102 and / or the powered component can be rectangular. In some variations, the discrete form of the pulsed power delivered to the light source 102 and / or the powered component can be modulated into other non-rectangular forms, such as sinusoidal or near-sinusoidal. In some variations, the shape of the pulsed power, the pulse frequency, and the percentage of the duty cycle can be optimized to minimize power consumption while allowing sufficient acquisition of the physical signal and reducing or eliminating low-frequency artifacts that may be introduced into the output signal of the miniaturized FBG demodulation system 100, which may overlap with frequency components in the physical signal sensed by the FBG sensor.

[0134] In some variations, the FBG demodulation system 100 can be configured to operate in an adaptive power mode via the PMU 109. In adaptive power mode, the power transmitted to the light source 102 and / or the powered components can be adaptively increased or decreased (i.e., adaptively adjusted) via the PMU 109 based on the amplitude of the physical signal sensed by the FBG sensor 106. For example, if it is determined that the amplitude of the physical signal sensed by the FBG sensor 106 is greater than a detection threshold, the power transmitted to the light source 102 and / or the powered components can be adaptively decreased via one or more power regulation circuits included in the PMU 109. The detection threshold can be an amplitude above which accurate data (e.g., accurate changes in parameters such as temperature, pressure, strain, etc.) can be reliably extracted from the physical signal sensed by the FBG sensor 106. Therefore, adaptively reducing the power transmitted to the light source 102 and / or the powered components when the amplitude of the physical signal sensed by the FBG sensor 106 is greater than the detection threshold can minimize and / or reduce the power consumed by the FBG demodulation system 100.

[0135] Similarly, if the amplitude of the physical signal sensed by FBG sensor 106 is determined to be below a sensitivity threshold, the power transmitted to the light source 102 and / or the powered components can be adaptively increased via one or more power regulation circuits included in PMU 109. The sensitivity threshold can be an amplitude below which accurate data (e.g., accurate changes in parameters such as temperature, pressure, strain, etc.) cannot be reliably extracted from the physical signal sensed by FBG sensor 106. Therefore, adaptively increasing the power transmitted to the light source 102 and / or the powered components when the amplitude of the physical signal sensed by FBG sensor 106 is less than the sensitivity threshold can increase the accuracy and sensitivity of the FBG demodulation system 100.

[0136] In some variations, the detection threshold of the light source can be the same as the detection threshold of the powered component. In some variations, the detection threshold of the light source can be different from the detection threshold of the powered component. In some variations, the sensitivity threshold of the light source can be the same as the sensitivity threshold of the powered component. In some variations, the sensitivity threshold of the light source can be different from the sensitivity threshold of the powered component. In some variations, the detection threshold can be the same as the sensitivity threshold. In some variations, the detection threshold can be different from the sensitivity threshold.

[0137] In some variations, the amount of power transmitted individually or in any combination thereof to the light source 102 and / or the powered components can be adaptively adjusted based on analysis of the amplitude of the physical signal sensed by the FBG sensor 106 or the output amplitude of the photodetector 104 as described above. In some variations, this adaptive power adjustment can take the form of adaptively adjusting (e.g., increasing or decreasing) the duty cycle of a clock, voltage and / or current and / or voltage / current signals, which controls the power transmitted to the light source 102 and / or the powered components, as described above.

[0138] In some variations, the detection threshold and / or sensitivity threshold may be predetermined. In some variations, the detection threshold and / or sensitivity threshold may be dynamically determined (e.g., based on historical and / or real-time data from the FBG demodulation system 100). In some variations, the detection threshold and / or sensitivity threshold may be determined based on user input and / or feedback. In some variations, adaptive adjustment of the power to the light source 102 and / or the powered component may take the form of adjustment of the current and / or voltage to the light source 102 and / or the powered component. In some variations, the adaptive adjustment of power may be the same between the light source 102 and / or the powered component. In some variations, the adaptive adjustment of power may be different between the light source 102 and / or the powered component. As an example, a miniaturized FBG demodulation system 100 may be integrated into an implantable medical device to sense ventricular myocardial strain, thereby determining the hemodynamic state during events such as arrhythmias, heart failure, and / or ischemia. In some variations, the baseline amplitude of myocardial strain (e.g., determined during normal rhythm and / or baseline conditions) may vary from subject to subject and from time to time within the same subject, depending on a number of factors, including but not limited to left ventricular ejection fraction, coronary blood supply adequacy, metabolic state, ventricular preload and / or afterload, etc. If the baseline amplitude of myocardial strain reliably and excessively exceeds the detection threshold, one or more power regulation circuits in PMU 109 may adaptively reduce the amount of electrical power to the light source 102 and / or the powered components to minimize power consumption. Conversely, if the baseline amplitude of myocardial strain sensed by FBG sensor 106 can be determined to be below the sensitivity threshold, one or more power regulation circuits in PMU 109 may adaptively increase the amount of electrical power to the light source 102 and / or the powered components to improve the sensitivity and accuracy of FBG demodulation system 100.

[0139] In some variations, the various power management modes described herein for minimizing or optimizing power consumption can be executed separately and / or simultaneously with one or more other modes as further described herein. However, in some variations, continuous modes and event-triggered modes can be formed sequentially rather than simultaneously. The power management unit and power management modes described herein in the context of a miniaturized FBG demodulation system can be independent of the specific system, device, and / or method that miniaturizes the FBG demodulator. In some cases, the power management unit (PMU) and associated power management modes described herein regulate the power consumption of the light source and other powered components, rather than directly regulating the power consumption of the optical sensor itself. In these cases, the PMU and power management modes described herein can be used to minimize and optimize the power consumption of other sensing systems or devices employing other optical sensors.

[0140] It should be easy to understand. Figure 1C The PMU 109' in the middle can be structurally and / or functionally similar to Figures 1A-1D PMU 109 in the middle.

[0141] Temperature compensation unit

[0142] The FBG demodulation system 100, integrated into a small device such as an implantable medical device, may include a temperature compensation unit 115. The temperature compensation unit 115 may include one or more temperature sensors configured to sense changes in temperature (e.g., body temperature).

[0143] In some variations, the temperature sensor in the temperature compensation unit 115 may include a temperature-sensing FBG sensor (e.g., similar to FBG sensor 106). For example, the temperature sensor may be formed within an optical fiber. However, unlike FBG sensor 106, the optical fiber of the temperature sensor may be strain-isolated at the grating plane. For example, the optical fiber of the temperature sensor may be at least partially disposed in, contained in, surrounded by, and / or enclosed by a rigid body. More specifically, the grating plane on the optical fiber may be wholly and / or partially disposed in, contained in, surrounded by, and / or enclosed by a rigid body. For example, the optical fiber of the temperature sensor may be at least partially disposed in, surrounded by, and / or enclosed by a rigid tubular structure (e.g., rigid tube, rigid cylinder, rigid hose, rigid conduit, rigid pipe, etc.), surrounded by, and / or enclosed by a rigid tubular structure.

[0144] Figure 13 An exemplary variant of a temperature sensor 120 formed within an optical fiber 123 and included in a temperature compensation unit 115 is shown. Figure 13As shown, the core of the optical fiber 123 may include a grating plane 125 to introduce a change in the refractive index of the core. The optical fiber 123 is partially disposed within, contained within, surrounded by, and / or enclosed by the rigid tubular structure 121. For example, the grating plane 125 may be completely disposed within, contained within, surrounded by, and / or enclosed by the rigid tubular structure 121. The rigid tubular structure prevents the optical fiber 123 from responding to changes in strain. More specifically, when light is emitted to the temperature sensor 120, the optical fiber 123 may reflect light of a specific wavelength. Temperature changes may cause changes in the grating period of the optical fiber 123. This, in turn, may cause a shift in the wavelength of the reflected light, resulting in a shift in the reflected spectrum. Because the grating plane 125 is entirely within the rigid tubular structure, strain changes may not cause changes in the grating period of the optical fiber. Therefore, the temperature sensor 120 can sense temperature changes but can be strain-isolated.

[0145] In some variations, for example in Figure 1B In the illustrated variant, the temperature sensor and FBG sensor 106 of the temperature compensation unit 115 can be optically coupled. More specifically, the temperature sensor (e.g., a temperature-sensing FBG sensor) and FBG sensor 106 can be formed on the same optical fiber. For example, the core of the optical fiber can have a grating plane to introduce changes in the refractive index of the core. A portion of the grating plane can be entirely disposed within, contained within, surrounded by, and / or enclosed by a rigid tubular structure. This portion of the optical fiber can form the temperature-sensing FBG sensor. Another portion of the grating plane may not be within the rigid tubular structure. This other portion of the optical fiber can form the FBG sensor 106. Thus, the portion of the grating plane within the rigid tubular structure (e.g., the temperature-sensing FBG sensor) can be strain-isolated. Such a portion can sense temperature changes but not strain changes. However, the portion of the grating plane not within the rigid tubular structure (e.g., the FBG sensor 106) can sense both temperature and strain changes. Therefore, when the optical fiber receives the spectrum emitted from the light source 102, the temperature sensing FBG sensor portion of the optical fiber can generate a first optical signal in response to the sensed temperature change, while the FBG sensor 106 of the optical fiber can generate a second signal in response to the sensed temperature change and strain change.

[0146] In other variations, the temperature sensor in the temperature compensation unit 115 can be any other suitable type of temperature sensor, such as a thermocouple, a resistance temperature detector, a thermistor, a digital temperature sensor, an infrared thermometer, etc.

[0147] In some variations, the temperature compensation unit 115 may include one or more processors to determine and / or compensate for temperature variations. In some variations, the temperature compensation unit 115 may be coupled to one or more processors (e.g., Figures 1A-1D The processor 112 in the middle determines and / or compensates for temperature changes.

[0148] One or more processors can be configured to compensate for temperature variations. More specifically, one or more processors can be configured to determine the precise changes in strain by compensating for temperature variations.

[0149] In some variations, one or more processors can compensate for temperature variations based on a calibration signature of the temperature sensor. The calibration signature can be retrieved and / or accessed by one or more processors. The calibration signature of the temperature sensor can be generated during the manufacturing process of the FBG demodulator system 100 and / or immediately before or during the implantation of the implantable medical device into a subject. For example, the calibration signature can be generated based on the output signal generated by the temperature sensor for a known temperature variation. In some variations, the calibration signature can include a lookup table. For example, a lookup table can correlate multiple output signals of the temperature sensor with multiple corresponding temperature variations. The lookup table can be generated based on the output signal from the temperature sensor for a known temperature variation. Additionally or alternatively, the calibration signature can include one or more equations that can be determined based on curve fitting, regression analysis, machine learning techniques and / or through an implementation of a neural network. More specifically, the calibration signature can include an equation or a set of equations that correlates output data (e.g., output signal) from the temperature sensor (e.g., the output wavelength from the temperature-sensing FBG sensor) with a known temperature variation (e.g., input data). Such a calibration signature can be generated and / or derived from the analysis of the known temperature variation and the output signal. In some variations, this analysis may include curve fitting, regression analysis, machine learning techniques and / or artificial intelligence techniques (e.g., implementations of neural networks).

[0150] In a temperature sensor variant of a temperature-sensing FBG sensor, calibration features can be generated based on the linear relationship between wavelength change and temperature change. For example, the output signal of the temperature-sensing FBG sensor can be a change in wavelength. The change in wavelength generated by the temperature-sensing FBG sensor for a known temperature change can be determined. Based on the linear relationship between wavelength change and temperature change, and based on the wavelength change generated for a known temperature change, calibration features of the temperature sensor (e.g., the temperature-sensing FBG sensor) can be generated. Calibration features may include multiple wavelengths for possible corresponding temperature changes (e.g., in the form of a lookup table and / or one or more equations as described above).

[0151] In some variations, one or more processors can recalibrate a temperature sensor after implantation of an implantable medical device (in vivo). For example, after implantation, the temperature sensor can be recalibrated using circadian rhythm variations of body temperature (e.g., circadian rhythm variations of core body temperature). For example, circadian rhythm variations of a subject with an implantable medical device can be identified at different time points. The temperature sensor can be recalibrated based on these circadian rhythm variations (e.g., a temperature-sensing FBG sensor can be recalibrated by taking into account the linear relationship between temperature changes and the corresponding wavelength shift). In some variations, core body temperature can be measured invasively (e.g., in the pulmonary artery) and / or non-invasively (e.g., in the rectum) to perform recalibration. In some variations, recalibration of the temperature sensor can include updating the calibration characteristics of the temperature sensor. For example, calibration characteristics can be updated based on circadian rhythm variations of core body temperature.

[0152] In some variations, the processor can retrieve calibration features from the memory of a small device, such as an implantable medical device like a cardiac implantable device. In some variations, the temperature compensation unit 115 may include memory for storing calibration features.

[0153] One or more processors can compensate for temperature changes based on calibration features. To compensate for temperature changes, one or more processors can receive a first signal from photodetector 104, which can indicate strain and temperature changes sensed by the FBG sensor. For example, a first reflected light signal representing strain and temperature changes generated by FBG sensor 106 can be converted into an electrical signal (e.g., the first signal) via photodetector 104. One or more processors can receive this first signal.

[0154] Additionally, one or more processors can receive a second signal representing a temperature change from the temperature sensor. In a variant where the temperature sensor is not a temperature-sensing FBG sensor (e.g., a thermocouple, resistance temperature detector, thermistor, digital temperature sensor, infrared thermometer, etc.), one or more processors can receive the second signal from the temperature sensor. The second signal can be an electrical signal (e.g., voltage, impedance, current, etc.). In a variant where the temperature sensor is a temperature-sensing FBG sensor, the second signal can be a reflected light signal. In other words, the temperature-sensing FBG sensor can generate a second reflected light signal. In such a variant, the second reflected light signal can be converted into an electrical signal (e.g., a second electrical signal) via a photodetector (e.g., photodetector 104 or photodetector 104'). One or more processors can receive this converted second electrical signal.

[0155] One or more processors can perform temperature compensation based on a first signal and a second signal. For example, one or more processors can determine the difference between the first signal and the second signal to determine the precise change in strain. In some variations, one or more processors can retrieve and / or access the calibration characteristics of a temperature sensor to perform temperature compensation. For example, one or more processors can correlate temperature changes with a second signal based on the calibration characteristics of a temperature sensor. In this way, one or more processors can determine the precise change in strain based on the first signal and the second signal.

[0156] In some variations, one or more processors (e.g., processors within and / or coupled to temperature compensation unit 115) may perform temperature compensation before, during, or after a physical event occurs. In some variations, one or more processors may be configured to receive signals indicating a physical event (e.g., from non-FBG sensors and / or from additional FBG sensors). In some variations, one or more processors may identify a physical event based at least in part on the analysis of physical signals detectable by non-FBG sensors, such as electrocardiogram and / or chest impedance signals detected by electrodes placed within the subject's body.

[0157] In some variations, physical events may occur at repetitive intervals (e.g., cardiac cycles, respiratory cycles, etc.). These repetitive physical events may have a periodicity that can vary over time. For example, cardiac and respiratory cycles are repetitive events whose periodicity is generally stable. However, there may be time variations in the periodicity of cardiac and respiratory cycles. In a variation where the FBG demodulation system 100 is integrated into an implantable medical device, repetitive physical events occurring at repetitive intervals can be detected by the implantable medical device, as further described herein. As a non-limiting example, cardiac cycles as repetitive events can be detected by analyzing electrocardiogram signals transmitted through electrodes in the implantable medical device. As yet another non-limiting example, respiratory cycles as repetitive events can be detected by analyzing transthoracic impedance via an impedance sensor in the implantable medical device. As yet another non-limiting example, the diurnal rhythm variation of core body temperature is another repetitive event. The diurnal rhythm variation of core body temperature can be detected invasively (e.g., in the pulmonary artery) and / or non-invasively (e.g., in the rectum).

[0158] One or more processors can perform temperature compensation at specific points in time and / or within specific time periods during periodic and / or periodic physical events. Figures 14A-14C An example temperature compensation is shown that is performed at a predetermined time point or within a predetermined time period during a physical event in gated temperature compensation mode.

[0159] For example, such as Figure 14AAs shown, the processor can, during the cardiac cycle (e.g., at the start or end of the QRS or immediately following the start or end of the QRS), at a specific time point (e.g., at...). Figure 14A (1451 locations) and / or within a specific time period (e.g., in Figure 14A Temperature compensation is performed within 1451a. For example... Figure 14B As shown, the processor can be activated at a specific point (e.g., at the start of a non-breathing or exhalation) during the respiratory cycle (e.g., at the beginning of exhalation or immediately afterward). Figure 14B (at position 1452 in the text) and / or within a specific time period (e.g., in Figure 14B Temperature compensation is performed within 1452a. For example... Figure 14C As shown, the processor can operate at specific points during the daily circadian rhythm of core body temperature (e.g., at...). Figure 14C (1453 in the text) and / or a specific time period (e.g., in Figure 14C Temperature compensation is performed within 1453a. In a variant where temperature compensation can be performed over a specific time period, one or more processors may perform temperature compensation based on the maximum, minimum, and / or average temperature over that specific time period. In some variants, the specific time and / or specific time period may be a predetermined point in time and / or a predetermined time interval.

[0160] In some variations, temperature compensation can be facilitated by using one or more signal processing techniques (e.g., signal averaging, filtering, etc.). These signal processing techniques can be based on the time-domain and / or frequency-domain characteristics of signals representing temperature changes and signals representing strain changes. For example, Figure 16 Example frequency domain characteristics of signals representing temperature changes (e.g., generated by a temperature-sensing FBG sensor) and signals representing strain changes (e.g., generated by FBG sensor 106) are shown. Figure 16 In the diagram, 1601 represents the power spectrum of the diurnal variability of core body temperature (e.g., generated via fast Fourier transform). Figure 16In this diagram, 1602 represents the power spectrum of ventricular myocardial strain changes. As seen in 1601, there is almost no power in the diurnal rhythm variation of core body temperature exceeding 0.2–0.3 Hz. Conversely, as seen in 1602, there are dominant frequency components in ventricular myocardial strain extending beyond 0.2–0.3 Hz up to approximately 25 Hz. Therefore, one or more processors can implement signal processing techniques (e.g., implementing a high-pass filter) to filter out extremely low-frequency components in the first signal generated by the FBG sensor 106 via the photodetector 104. In this variant, extremely low-frequency components attributable to core body temperature changes can be filtered out or eliminated from the first signal generated by the FBG sensor 106, while retaining higher-frequency components attributable to ventricular myocardial strain changes. In this variant, a temperature sensor may no longer be needed to perform temperature compensation.

[0161] Optional adjustment of FBG

[0162] In some variations, the FBG demodulation system 100 may optionally include one or more adjustable FBGs 110 to split the emitted spectrum of the light source 102 into multiple spectral segments. The adjustable FBG 110 can be formed on an optical fiber by etching segments onto the core of an optical fiber having a periodically varying refractive index. However, unlike the FBG sensor 106, the adjustable FBG 110 can be configured to split the emitted spectrum into multiple spectral segments. For example, when the emitted spectrum from the light source 102 is transmitted to the adjustable FBG 110, the adjustable FBG 110 can generate notches in the emitted spectrum, thereby splitting the emitted spectrum into multiple spectral segments. The adjustable FBG 110 can be optically coupled to the light source 102. If the emitted spectrum of the light source 102 has such... Figure 2A As shown in the diagram, adjusting FBG 110 can optically couple to light source 102 to split the single spectral segment into segments such as... Figure 2B Multiple spectral segments are shown. In some variations, adjusting FBG 110 can be used as a filter (e.g., to optimize the width and / or slope of the discriminative spectral domain in the emission spectrum of light source 102).

[0163] It should be easy to understand. Figure 1C The adjustment FBG 110' in the middle can be structurally and / or functionally similar to Figures 1A-1D Adjust FBG 110 in the middle.

[0164] optical router

[0165] In some variations, the FBG demodulation system 100 may include one or more optical routers 108 to direct or relay optical signals between two or more components of the FBG demodulation system 100 and / or distribute optical signals from one component to two or more components of the FBG demodulation system 100. For example, the optical router 108 may optically couple the light source 102 and the photodetector 104 to the FBG sensor 106. The optical router 108 may be a single optical fiber comprising two separate fiber sections (e.g., a first fiber section and a second fiber section). The optical router 108 may receive an optical signal through the single fiber, which may be split into two separate output optical signals (e.g., a first optical signal and a second optical signal) transmitted through the two separate fiber sections. For example, the first fiber section may optically couple the FBG sensor 106 to the light source 102. The second fiber section may optically couple the FBG sensor 106 to the photodetector 104. This may be advantageous for making the FBG demodulation system 100 compact and reducing its form factor. More specifically, in order to transmit an optical signal from light source 102 to FBG sensor 106, an optical fiber may be needed to optically couple light source 102 and FBG sensor 106. Similarly, in order to receive the reflected optical signal from FBG sensor 106 at photodetector 104, an optical fiber may be needed to optically couple photodetector 104 and FBG sensor 106. Instead of using two separate optical fibers, which might contribute to the bulkiness of the FBG demodulation system 100, an optical router 108 with a single optical fiber can be used. As a non-limiting example, the optical router 108 as described herein may include an optical coupler, optical splitter, optical circulator, or optical switch.

[0166] It should be easy to understand. Figure 1C The optical router 108' in the middle can be similar in structure and / or function to Figures 1A-1D The optical router 108 in the middle.

[0167] Exemplary variations of FBG demodulation system components

[0168] Discriminant spectral domain

[0169] The FBG sensor 106 and / or the light source 102 can be designed such that the emission spectrum of the light source 102 and the reflection spectrum of the FBG sensor 106 are configured to interact in a discrimination spectral domain. The discrimination spectral domain can be a region in the emission spectrum of the light source 102 and / or a region in the reflection spectrum of the FBG sensor 106.

[0170] Figure 4 The discrimination spectral domain 440a is shown. and 440a An exemplary variant. The discriminative spectral domain can be region 440a in spectral segment 440a. and / or area 440a Spectral fragment 440a may include a peak 440a''' and a rising edge 440a'' and a falling edge 440a'' on either side of the peak 440a'''. Discrimination spectral domain 440a This could be the region below the rising edge 440a'. For example, the discriminant spectral domain 440a. This could be a tilted portion of spectral segment 440a (e.g., the region below slope 440a'). Additionally or alternatively, the spectral domain 440a is discriminated. This could be the region below the descending edge 440a''. Spectral segment 440a could be a light source (e.g., Figures 1A-1D The spectral fragment of the emission spectrum of the light source 102) and / or the FBG sensor (e.g., Figures 1A-1D The spectral segment of the reflected spectrum of the FBG sensor 106 in the image. Therefore, the discrimination spectral domain 440a. and 440a It can be defined by a portion of the emission spectrum of each free light source and / or a portion of the reflection spectrum of the FBG sensor. Figure 4 This represents the relationship between the intensity and wavelength of a light source when the discrimination spectral domain is defined by the emission spectrum of the light source. In other words, Figure 4 The y-axis in the diagram represents the intensity of the light source when the discrimination spectral domain is defined by the emission spectrum of the light source. Similarly, Figure 4 The y-axis in the diagram represents the relationship between the reflectance of the FBG sensor and the wavelength when the discrimination spectral domain is defined by the spectrum of reflection from the FBG sensor. In other words, Figure 4 The y-axis in the figure represents the reflectance of the FBG sensor when the discrimination spectral domain is defined by the spectrum of reflection from the FBG sensor.

[0171] In the discrimination spectral domain (e.g., 440a) Or 440a In the FBG sensor, the power of the reflected light signal can vary monotonically (e.g., linearly) in response to a shift in the reflected spectrum. As discussed herein, the reflected spectrum of the FBG sensor can shift in response to changes in the physical signal sensed by the FBG sensor. Within the operating range of the FBG sensor, the shift in the reflected spectrum can be expressed as a monotonic function of the changes in the physical signal sensed by the FBG sensor. Therefore, in the discrimination spectral domain (e.g., 440a)... Or 440a In the FBG sensor, the power of the reflected light signal can change monotonically (e.g., linearly) in response to changes in the physical signal sensed by the FBG sensor. Therefore, when discriminating the spectral domain (e.g., 440a...), Or 440a When the range is sufficiently wide to cover the entire operating range of the FBG sensor, the shift in the spectrum of the reflected light from the FBG sensor is indirectly detected for the discrimination spectral domain (e.g., 440a). Or 440a It is feasible to use low-measurement-frequency physical signals on the FBG. Therefore, the bulky Fabry-Perot interferometers currently used for physical signals with relatively large value ranges of low measurement frequencies (e.g., <100Hz) can be eliminated. In contrast, some variations of the FBG demodulation system 100 described herein can represent the simplest FBG demodulation system with a minimal number of components, including an FBG sensor 106, at least one light source 102, and a photodetector.

[0172] As mentioned above, in some variations, the discrimination spectral domain 440a This can be defined by the falling edge 440'' of the spectral segment 440a. The falling edge 440a'' can represent a monotonically decreasing function. For example, the falling edge 440'' can represent a function such that with a shift in wavelength, the power of the reflected light signal can be represented. Therefore, with a shift in the reflected spectrum (and a shift in wavelength), the power of the reflected light signal can change monotonically. Thus, a change in the physical signal sensed by the FBG sensor (e.g., a decrease in strain) can produce a corresponding change in the power of the reflected light signal (e.g., an increase in the power of the reflected light signal). Although for ease of illustration, Figure 4 The rising edge 440a' and falling edge 440a'' are depicted as smooth curves, but it should be readily understood that these slopes may have small irregularities or ripples. These small irregularities or ripples can negatively impact the accuracy, resolution, or sensitivity of a miniaturized FBG demodulation system. In some variations, these small irregularities or ripples can be minimized through the manufacturing process of the light source and / or the FBG sensor. Additionally or alternatively, the effects of these small irregularities or ripples can be minimized during the operation of a miniaturized FBG demodulation system by applying signal processing algorithms. In some variations, the gradient of the rising edge 440a' or falling edge 440a' can be optimized to allow increased sensitivity without compromising the width of the discrimination spectral domain. This can make a miniaturized FBG demodulation system (e.g., FBG demodulation system 100) more sensitive to small changes in the physical signal, thereby increasing the sensitivity of the miniaturized FBG demodulation system 100.

[0173] Discrimination spectral domain (e.g., 440a) Or 440a The spectral range should be at least wide enough to cover the operating range of the FBG sensor. More specifically, the minimum width of the discrimination spectral range should allow the power of the reflected light signal to vary monotonically across the entire operating range of the FBG sensor. If the spectral range (e.g., 440a) is significantly wider, the power of the reflected light signal will vary monotonically across the entire operating range of the FBG sensor. Or 440a If the width of the FBG sensor and / or light source is less than the minimum width, the FBG sensor and / or light source can be designed to extend the width of the discrimination spectral domain, as further described below.

[0174] light source

[0175] In some variations, the light source (e.g., Figures 1A-1D The light source 102 can be designed such that a portion of the spectrum emitted by the light source can define the discriminative spectral domain (e.g., 440a). Or 440a For example, discriminative spectral domain (e.g., 440a) Or 440a This can be a region in the emission spectrum of the light source. As an example, consider spectral segment 440a in the emission spectrum of the light source. Figure 4 The y-axis represents the intensity of the light source. In some variations, the discrimination spectral domain is 440. This could be the region below the rising edge 440a'. Additionally or alternatively, the discriminant spectral domain 440... It can be the region below the falling edge 440a''. In some variations, spectral segment 440a can represent the entire emission spectrum of the light source as described herein. In other variations, spectral segment 440a can be a spectral segment of the emission spectrum that includes multiple spectral segments (e.g., in...). Figure 2B and Figure 2C (In this case, the emitted spectrum may include multiple discriminative spectral domains. For example, any number of spectral segments of the emitted spectrum may include at least one discriminative spectral domain. For example, if the emitted spectrum of the light source includes three spectral segments, then one spectral segment, any two spectral segments, or all three spectral segments may each include at least one corresponding discriminative spectral domain, such as...) Figure 4 The discriminant spectral domain 440a Or 440a .

[0176] In some variations, the light source can be designed to discriminate the spectral domain 440a. It must have at least a minimum width sufficient to cover the operating range of the FBG sensor. For example, the LED light source can be designed such that the width of the falling edge 440a'' in the emitted spectrum is wide enough to cover the operating range of the FBG sensor. More specifically, the minimum width of the falling edge 440a'' in the emitted spectrum can be determined based on the operating range of the FBG sensor. The light source can be designed such that the falling edge 440a'' of the emitted spectrum has at least a minimum width.

[0177] In some variations, the width of the rising edge 440a' and / or falling edge 440a'' of the emitted spectral segment of the light source 102 can be optimized. For example, the width and gradient of the rising edge 440a' and / or falling edge 440a'' of the emitted spectral segment can be optimized during the manufacturing process of the light source (“pre-emission manufacturing”). Alternatively, the width and gradient of the rising edge 440a' and / or falling edge 440a'' of the emitted spectral segment can be optimized after the light source is manufactured (“post-emission modification”).

[0178] In some variations, as a non-limiting example, the pre-emission fabrication process may include changing the dopants in the light source (e.g., changing the doping concentration). For example, the doping concentration and / or the dopant may be varied in the quantum well; for instance, an arsenic and / or phosphorus composition may be varied for an infrared emitter. In a similar manner, the indium doping composition may be varied from a blue emitter to a green emitter. Changing the concentration or composition of the dopant can alter the emission spectrum of the light source. The concentration or composition can be changed such that the width and gradient of the rising edge 440a' and / or falling edge 440a'' of the emitted spectral segment can be optimized.

[0179] In some variations, the post-emission modification process may include coating the light source with a dye or pigment or a wavelength conversion material (such as phosphors and / or quantum dots). For example, the physical dimensions and / or composition of the dye or pigment or wavelength conversion material may be altered. Changing the physical dimensions and / or composition of the dye or pigment or wavelength conversion material can alter the emission spectrum of the light source. Therefore, the light source may be coated with a dye or pigment or wavelength conversion material such that the width and gradient of the rising edge 440a' and / or falling edge 440a'' of the emitted spectral segment can be optimized. In some variations, the post-emission modification process may include using one or more optical filters (e.g., adjusted FBG) to modify the emission spectrum of the light source such that the width and gradient of the rising edge 440a' and / or falling edge 440a'' of the emitted spectral segment can be optimized.

[0180] In some variations, the light source can be designed to include multiple light sources, each with a different emission spectrum. These multiple light sources can be packaged together in such a way that the combined emission spectrum can include a discriminative spectral domain (e.g., 440a) with a desired minimum width (e.g., a minimum width that can be determined as described above). Or 440a As another example, a light source can be designed to include multiple LEDs, each with a different emission spectrum. These multiple LEDs can be packaged together in such a way that the combined emission spectrum can include a discriminative spectral domain of the desired or required minimum width (e.g., 440a). Or 440a ).

[0181] Figure 5A The light source is shown (e.g., Figures 1A-1D The emission spectrum 540 of the light source 102) and the FBG sensor (e.g., Figures 1A-1D An exemplary variant of the reflected spectrum 550 of the FBG sensor 106 in the light source, wherein the spectrum 540 and the spectrum 550 are configured to define a discrimination spectral domain 540 within the emitted spectrum 540 of the light source. They interact with each other. For example, the emission spectrum 540 of the light source and the reflection spectrum 550 of the FBG sensor can be separated into the discrimination spectral domain 540 of the emission spectrum 540. The two interact. Due to the reflected light signal (e.g., Figure 5A The power of 552 in the discrimination spectral domain is 540. The FBG demodulation system is susceptible to variations in the physical signal within the FBG sensor's operating range, as the discrimination spectral domain has a minimum width to cover the entire operating range. This sensitivity can be mitigated by increasing the limiting of the discrimination spectral domain to 540. The sensitivity of the FBG demodulation system can be increased by adding a gradient along the falling edge of the 540° gradient. This can be achieved by increasing the discrimination spectral domain of 540°. The width is increased to expand the operating range of the FBG sensor. In some variations, the reflected light signal (e.g., Figure 5A The power of 552 in the figure can be defined as follows: where L(wl) represents the intensity of the emission spectrum 540 of the light source, and F(wl) represents the reflectivity of the reflection spectrum 550 of the FBG sensor at wavelength wl.

[0182] In some variations, the light source can be designed to interact with the spectra of multiple reflections from the FBG sensors. For example, an FBG demodulation system may include multiple FBG sensors, each with a different center wavelength and corresponding operating range. The spectrum of the collective reflections from the multiple FBG sensors may include multiple spectral segments of reflections (e.g., Figure 3B The light source can be configured to transmit multiple spectral segments of reflected light, where each spectral segment corresponds to the spectrum of reflected light from a specific FBG sensor. In some variations, the light source can be designed such that the spectrum of a single emission from the light source can be tuned to interact with the spectrum of each reflected light from the corresponding FBG sensor in the respective discrimination spectral domain. For example, the light source can be designed such that the spectrum of a single emission from the FBG (e.g., ...) can be tuned to the spectrum of reflected light from the FBG (e.g., ...) Figures 1A-1D The FBG (110) is separated such that each separated spectral fragment can interact with the spectrum reflected by each individual FBG sensor in the corresponding discriminant spectral domain. In other variations, the light source may include multiple light sources, wherein the spectrum emitted by each individual light source is designed to interact with the spectrum reflected by each individual FBG sensor in the corresponding discriminant spectral domain.

[0183] FBG sensor

[0184] Return to reference Figure 4 In some variations, FBG sensors (e.g.) Figures 1A-1D The FBG sensor 106 in the image can be designed such that a portion of the spectrum reflected by the FBG sensor can define the discrimination spectral domain (e.g., 440a). Or 440a ). Figure 4 The y-axis can represent the reflectivity of the FBG sensor. For example, the discrimination spectral domain (e.g., 440a) Or 440a The region can be a region in the spectrum of reflection from the FBG sensor. As an example, consider spectral segment 440a in the spectrum of reflection from the FBG sensor. In some variations, spectral segment 440a can represent the entire spectrum of reflection from the FBG sensor (e.g., Figure 3A (in the middle). In this case, the reflected spectrum may include at least one discriminative spectral domain, such as the 440a described herein. and / or 440a In other variations, spectral fragment 440a may be a spectral fragment in the reflection spectrum that includes multiple spectral fragments (e.g., in...). Figure 3B(In this case, the reflected spectrum may include multiple discriminant spectral domains. For example, each spectral segment of the reflected spectrum may include a corresponding discriminant spectral domain 440a.) 440a Or both.

[0185] In some variations, the FBG sensor can be designed to discriminate the spectral range (e.g., 440a). Or 440a The FBG sensor can be designed to have at least a minimum width that covers the operating range of the FBG sensor. For example, the FBG sensor can be designed such that the width of the falling edge 440a'' in the reflected spectrum is wide enough to cover the operating range of the FBG sensor. More specifically, the minimum width of the falling edge 440a'' in the reflected spectrum can be determined based on the operating range of the FBG sensor. The FBG sensor can be designed such that the falling edge 440a'' of the reflected spectrum has at least a minimum width.

[0186] In some variations, the discrimination spectral domain (e.g., 440a) can be optimized by changing the grating period of the FBG sensor, changing the number of gratings with a given grating period of the FBG sensor, changing the distribution pattern of gratings with different grating periods along the fiber core of the FBG sensor, changing the tilt or angle of the grating plane, changing the exposure time to ultraviolet light during grating writing on the fiber, changing the chemical composition of the fiber core to change the refractive index, introducing a gradient in the refractive index of the fiber core (e.g., by changing the tilt or angle of the grating plane and / or changing the exposure time to ultraviolet light), and combinations thereof. Or 440a The width of ).

[0187] For example, FBG sensors can be designed such that the number of gratings can be increased for reflected light signals at wavelengths requiring higher power, and the number of gratings can be decreased for reflected light signals at wavelengths requiring lower power. For example, in Figure 4In this approach, for reflected light signals with wavelengths closer to the peak 440a, the number of gratings in the FBG sensor can be increased. The power of the reflected light signal from the FBG sensor can be proportional to the number of gratings. Therefore, a larger number of gratings for reflected light signals at wavelengths closer to the peak 440a can increase the power of the reflected light signals at those wavelengths. Conversely, as the wavelengths of the reflected light signals begin to move away from the peak 440a, the number of gratings in the FBG sensor can be reduced. For example, for reflected light signals at wavelengths furthest from the peak 440a, the number of gratings in the FBG sensor can be minimal. A smaller number of gratings can reduce the power of these reflected light signals. The increased power near the peak 440a and the decreased power away from the peak 440a, in turn, can increase the gradient at the falling edge 440a'', thereby adjusting the sensitivity of the FBG demodulation system as needed. Furthermore, this can increase the width of the slope (e.g., at the falling edge 440a''), thereby increasing the discrimination spectral domain (e.g., 440a). The width of the spectrum is adjusted to make the discrimination spectral domain conform to the desired operating range of the FBG sensor, thereby enabling the FBG sensor to sense physical signals with low measurement frequencies but a larger value range.

[0188] Alternatively or additionally, the FBG sensor can be designed such that the grating period (e.g., the space between gratings) can be varied, allowing for a different discrimination spectral domain (e.g., 440a). Or 440a It must have at least a minimum width. For example, an FBG sensor can be designed such that the grating period can be increased for reflected light signals at wavelengths where higher power is desired, and decreased for reflected light signals at wavelengths where lower power is desired. In this way, the number of gratings and / or the grating period of the FBG sensor can be varied to expand the discrimination spectral domain (e.g., 440a). Or 440a The width of the FBG demodulation system can be increased without increasing the total width of the emitted spectrum of the light source or the reflected spectrum of the FBG sensor. Increasing the emitted spectrum of the light source may increase the power consumption and physical size of the FBG demodulation system.

[0189] In some variations, the FBG sensor can be a chirped FBG sensor, which can form a grating period with gradual changes. The grating period of the chirped FBG sensor can be changed in such a way that the discrimination spectral domain 440 The width can at least cover the operating range of the FBG sensor.

[0190] Figure 5B The light source is shown (e.g., Figures 1A-1DThe emission spectrum 540 of the light source 102) and the FBG sensor (e.g., Figures 1A-1D An exemplary variant of the reflected spectrum 550 of the FBG sensor 106 in the image, wherein the spectrum 540 and the spectrum 550 are configured to define a discrimination spectral domain 550 defined by the falling edge 550'' in the reflected spectrum 550 of the FBG sensor. The two interact. For example, the emission spectrum 540 of the light source and the reflection spectrum 550 of the FBG sensor can be placed in the discrimination spectral domain 550 of the reflection spectrum 550. The two interact. Due to the reflected light signal (e.g., Figure 5B The power of 552 in the discrimination spectral domain is 550. The FBG demodulation system may be sensitive to changes in the physical signal within the FBG sensor's operating range, as the discrimination spectral domain has a minimum width covering the entire operating range of the FBG sensor. This can be addressed by increasing the limiting of the discrimination spectral domain to 550. The sensitivity of the FBG demodulation system is increased by adjusting the gradient of the falling edge. Furthermore, the discrimination spectral domain of 550 nm is increased. The width of the reflected spectrum of the FBG sensor (550) can conform to the operating range of the FBG sensor. In some variations, the reflected light signal (e.g., Figure 5B The power of 552 in the figure can be defined as follows: where L(wl) represents the intensity of the emission spectrum 540 of the light source, and F(wl) represents the reflectivity of the reflection spectrum 550 of the FBG sensor at wavelength wl.

[0191] In some variations, the FBG demodulation system may include multiple FBG sensors. For example, a single optical fiber may include more than one FBG sensor. Alternatively, the FBG demodulation system may include multiple optical fibers, thereby including multiple FBG sensors.

[0192] Example of the interaction between the FBG sensor and the light source

[0193] To sense and acquire all possible values ​​of the physical signal that the FBG sensor can be configured to sense, the emission spectrum of the light source and the reflected spectrum of the FBG sensor can be configured to interact in the discrimination spectral domain. For example, the emission spectrum of the light source and the reflected spectrum of the FBG sensor can be made to overlap in the discrimination spectral domain. The discrimination spectral domain can be defined by a portion of the emission spectrum of the light source and / or a portion of the reflected spectrum of the FBG sensor. The minimum width of the discrimination spectral domain can be determined based on the operating range of the FBG sensor, which is further defined by the range of possible values ​​of the physical signal that the FBG sensor can be configured to sense. Variations in the physical signal sensed by the FBG sensor can cause a shift in the reflected spectrum of the FBG sensor. The power of the reflected light signal (reflected by the FBG sensor) can monotonically vary in the discrimination spectral domain in response to wavelength shifts in the reflected spectrum, thus excluding Fabry-Perot interferometers. This, in turn, allows the FBG demodulation system to be miniaturized for lower measurement frequencies of sensed physical signals with a relatively large range of values.

[0194] The FBG sensor and / or light source can be designed such that the discrimination spectral domain has a minimum width to cover the entire operating range of the FBG sensor. Additionally, the FBG sensor and / or light source can be designed such that the slope (rising or falling edge) in the emission spectrum of the light source or in the reflection spectrum of the FBG sensor defining the discrimination spectral domain can have an increased gradient, thereby increasing the sensitivity of the FBG demodulation system.

[0195] In some variations, an FBG demodulation system may include a single light source having an emitted spectrum. The emitted spectrum may have a single spectral segment. In some variations, to sense a physical signal using a single light source, the FBG demodulation system may modulate the single light source such that the emitted spectrum comprises multiple spectral segments. For example, the FBG demodulation system may include a single light source such that the emitted spectrum of the light source can be modulated (e.g., using one or more modulated FBGs) to be divided into multiple spectral segments. Alternatively, the FBG demodulation system may include multiple light sources, each with its own emitted spectrum. In this case, when the emitted spectrum comprises multiple spectral segments and the reflected spectrum comprises a single spectral segment, the FBG sensor can be designed such that the corresponding reflected spectrum of each FBG sensor can be configured to interact with one of the multiple spectral segments of the emitted spectrum of the light source in its respective discrimination spectral domain.

[0196] In some variations, the FBG demodulation system may include multiple FBG sensors. Each FBG sensor may have a corresponding reflectance spectrum. Therefore, the collective reflectance spectrum of the FBG sensors may include multiple reflectance spectral segments. In this case, the light source of the FBG demodulation system may be designed to include multiple emission spectral segments, which can interact with each of the multiple reflectance spectral segments of the FBG sensors in their respective discrimination spectral domains.

[0197] Figure 10 An FBG sensor (e.g.) is shown. Figures 1A-1D The spectrum of reflection from the FBG sensor 106 in the image is compared with that from two light sources (e.g., Figures 1A-1D An example interaction between the emitted spectra of the light source 102 in the diagram. The light source can be any suitable light source, such as one with a narrow bandwidth. The reflected spectrum 1050a can represent the reflected spectrum at one end of the operating range of the FBG sensor. When the FBG sensor is exposed to a change in a physical signal (e.g., strain), the reflected spectrum 1050a of the FBG sensor can shift. For example, the reflected spectrum 1050a' can represent the shift in the reflected spectrum 1050a when the FBG sensor is exposed to a change in a physical signal. Thus, as an example, the reflected spectrum 1050a' can represent the reflected spectrum at the other end of the operating range of the FBG sensor. The operating range of the FBG sensor is shown as 1060.

[0198] The emission spectrum 1040a can represent the emission spectrum of the first light source. For example... Figure 10 As shown, the emitted spectrum 1040a of the first light source is outside the operating range of the FBG sensor 1060. The output or power of the reflected light signal, resulting from the interaction between the emitted spectrum 1040a and the reflected spectrum 1050a, is represented by 1070a. Figure 10 As shown, since the emitted spectrum 1040a is outside the operating range 1060 of the reflected spectrum 1050a, it may be impossible to detect changes in the physical signal from the output or power of the reflected optical signal 1070a of the FBG demodulation system.

[0199] Conversely, the emitted spectrum 1040b can represent the emitted spectrum of a second light source that is different from the first light source. For example... Figure 10As seen, the emission spectrum 1040b of the second light source is within the operating range 1060 of the FBG sensor. Furthermore, the emission spectrum 1040b of the second light source interacts with the reflected spectrum 1050a' of the FBG sensor on a portion of the discrimination spectral domain of the reflected spectrum 1050a'. For example, the interaction between the emission spectrum 1040b of the second light source and the reflected spectrum 1050a' of the FBG sensor causes the power of the reflected light signal to change monotonically in response to wavelength shifts in the reflected spectrum 1050a'. Therefore, the output or power of this interacting reflected light signal 1070b may be sensitive to changes in the physical signal.

[0200] Figure 10 Representative data are derived from typical in vivo experiments in pigs, where the FBG sensor is integrated into an ICD lead inserted into the right ventricle. The output or power of the reflected light signal indicates systole and diastole during the cardiac cycle at low measurement frequencies and relatively large strain variations.

[0201] Figures 6A-6E The light source is shown (e.g., Figures 1A-1D The exemplary emission spectrum of light source 102) and FBG sensor (e.g., Figures 1A-1D The interaction between the exemplary reflected spectra of the FBG sensor 106 in the discriminative spectral domain. Figure 6A In this context, the FBG sensor exhibits a narrow spectral reflectance. For example, the FBG sensor can be a standard FBG sensor with a standard grating (e.g., type IA) and a narrow-band reflectance spectrum. The operating range of the FBG sensor can be determined based on the possible values ​​of the physical signal it is configured to sense (e.g., possible values ​​of strain in the heart, possible values ​​of mechanical motion of the heart, etc.). Figure 6A In this context, the light source can be an LED light source. The LED light source and the standard FBG sensor can be designed to interact in the discrimination spectral domain. For example, in... Figure 6A In this system, the discrimination spectral domain can be defined by the falling edge of the emission spectrum from the LED light source. The emission spectrum of the LED light source and the reflected spectrum of the FBG sensor can be configured to interact in the discrimination spectral domain. Since the portion of the emission spectrum that defines the discrimination spectral domain is monotonic overall, changes in the physical signal sensed by the FBG sensor can be quantitatively reflected by the corresponding changes in the power of the reflected light signal.

[0202] exist Figure 6B In this context, the reflected light from the FBG sensor has a broad spectrum. For example, the FBG sensor could be an improved chirped FBG sensor. The light source can be a narrowband source, such as a distributed feedback diode (DFB). DFB and / or chirped FBG sensors can be designed to interact in the discrimination spectral domain. Figure 6B In this design, the discrimination spectral domain can be defined by the falling edge of the reflected spectrum of the modified chirped FBG. Since a portion of the falling edge of the reflected spectrum that defines the discrimination spectral domain is monotonic overall, changes in the physical signal sensed by the FBG sensor can be quantitatively reflected by the corresponding changes in the power of the reflected light signal.

[0203] exist Figure 6C In this context, the reflected spectrum of the FBG sensor is broad. For example, the FBG sensor could be an improved chirped FBG sensor. However, compared to... Figure 6B different, Figure 6C The light source can be, for example, an LED with a wider emission spectrum. Figure 6C In this system, the discrimination spectral domain can exist in the rising or falling edge of the spectrum reflected by the FBG sensor and in the spectral range of the emitted light source. This allows wavelength shifts in the spectrum reflected by the FBG sensor to cause interaction between the emitted spectrum of the light source and the reflected spectrum of the FBG sensor in the two discrimination domains, thereby increasing the overall discrimination spectral domain width and the sensitivity of the EBG demodulation system to changes in the physical signal sensed by the FBG sensor.

[0204] As discussed herein, an FBG demodulation system may include multiple FBG sensors. These multiple FBG sensors may be formed on a single optical fiber. This saves space and makes the FBG demodulation system smaller, enabling miniaturization for integration into implantable medical devices while retaining the ability to sense multiple physical signals and / or sense physical signals at multiple locations. The emission spectrum of the light source can be configured to interact with the spectrum of each individual reflection from the multiple FBG sensors. Figure 6D The spectrum of collective reflections from multiple FBG sensors multiplexed over a single optical fiber is shown. The light source can be a narrowband source. The emission spectrum of the light source can be configured to interact with the reflected spectrum of a specific FBG sensor in the discrimination spectral domain. In some variations, the FBG demodulation system may include multiple such light sources, each interacting with a different FBG sensor. In some variations, small fiber optic switches may be included in the FBG demodulation system to switch between / among the light sources, such that only one light source can be active at a time.

[0205] Figure 6EThe emission spectrum of a light source divided into multiple spectral segments is shown. Each spectral segment can be configured to interact with the corresponding reflected spectrum of an FBG sensor. In some variations, a light source having a single spectral segment in its emitted spectrum can be coupled to an regulated FBG to generate multiple spectral segments. The light source can be optically coupled to at least one regulated FBG to divide the emitted spectrum of the light source into at least two spectral segments, each designed to interact with a corresponding FBG sensor.

[0206] Photodetector

[0207] In this miniaturized FBG demodulation system 100, more than one FBG sensor is included on a single optical fiber (e.g., Figures 1A-1D In a variation of the FBG sensor 106, a photodetector (e.g., photodetector 104) can be designed such that changes in the physical signal sensed by each FBG sensor on a single optical fiber are acquired and measured. For example, the photodetector can be designed such that more than one photodetector can exist, with each photodetector coupled to a corresponding FBG sensor. To receive the reflected spectrum from each FBG sensor, wavelength division multiplexing (WDM) can be applied to the photodetector. Applying WDM to couple the photodetector to the FBG sensor allows each photodetector to receive the reflected optical signal from its respective FBG sensor in response to the physical signal sensed by its respective FBG sensor.

[0208] Power Management Unit

[0209] In some variations, the power management unit (PMU) 109 may include at least one or more switches (e.g., ultrafast switches) and at least one or more power regulation circuits. As described above, this can be achieved via switches (e.g., Figure 12A 1208) enables and / or disables power to the light source and / or the powered components, and can be done via a power regulation circuit (e.g., Figure 12A(1206) Adjusts (e.g., increases or decreases) the amount of power transmitted to the light source and / or powered component. In some variations, the power conditioning circuit and the switch may be packaged together as a single unit and may be integrated into the FBG demodulation system 100. Additionally or alternatively, at least one or more power conditioning circuits and at least one or more switches may be integrated separately into the FBG demodulation system 100 as separate units. In some variations, one or more switches may be coupled to one or more light sources and / or powered components and are structurally or physically integrated into the FBG demodulation system 100 together with the light sources and / or powered components to which the one or more switches are coupled. Similarly, at least one or more power conditioning circuits may be coupled to one or more light sources and / or powered components and are structurally or physically integrated into the FBG demodulation system 100 together with the light sources and / or powered components to which the one or more power conditioning circuits are coupled. In some variations, the switching and power conditioning circuitry can be designed with different structures or physical arrangements to reduce the physical size of the FBG demodulation system 100, minimize the power consumed by the FBG demodulation system 100, and / or reduce the heat generated from the FBG demodulation system 100.

[0210] In some variations, the switch in PMU 109 may include at least one or more ultrafast power switches to enable and disable power delivered to the powered components and / or light source 102 in FBG demodulation system 100. In some variations, the switch may include off-chip, readily available circuitry components, such as Analog Devices® ADG901 or ADG918. In some variations, the switch may include custom-designed on-board switching circuitry consisting of one or more packaged transistors, such as complementary metal-oxide-semiconductor (CMOS) transistors, bipolar junction transistors (BJTs), and gallium nitride (GaN) transistors. In some variations, the switch may include custom-designed on-chip circuitry based on CMOS, BJT, and GaN on-chip technologies. The design of the on-chip switch may include one or more transistors, one or more on-chip resistors, and / or other logic circuitry to achieve improved switching performance. In some variations, each power management mode described herein may have a dedicated power switch. In some other variations, one or more switches may be used for more than one power management mode.

[0211] It should be understood that the physical arrangement or sequence between switch 1208 and power regulation circuit 1206 can vary. In some variations, the switch may be positioned before the power regulation circuit for a light source or a powered component. In some variations, the power regulation circuit may be positioned before the switch for another light source or another powered component.

[0212] In some variations, PMU 109 may include at least one or more clock generation circuits to control the timing of switches individually or collectively. In some variations, the clock generation circuits may be used to control the switching for pulse mode. In some variations, the clock generation circuits may also be used to control the sampling rate or frequency of one or more powered components in the FBG demodulation system 100 for one or more power management modes (e.g., for adaptive power mode). The clock generation circuits may be implemented using various circuit components such as phase-locked loops (PLLs), voltage-controlled oscillators (VCOs), and delay-locked loops (DLLs). In some variations, the clock frequency may need to be changed in one or more power management modes (e.g., for pulse or adaptive power mode). In some variations, the clock frequency may be the same or different for different power management modes (e.g., for pulse or adaptive power mode). The frequency can be changed by tuning circuit parameters, including but not limited to voltage, current, inductance, and capacitance. In some variations, the clock generation circuit may also include one or more other associated circuits, such as a Johnson counter and a phase interpolator, to modify the phase and / or duty cycle of the clock output. In some variations, a processor coupled to the PMU 109 may be used alternatively (e.g., Figures 1A to 1D The clock circuit in the processor 112.

[0213] In some variations, PMU 109 may include at least one or more programmable power conditioning circuitry to regulate the amount of power delivered to one or more powered components and / or light sources in the adaptive power management mode described herein. As a non-limiting example, it may include an on-chip / off-chip AC-DC-DC converter, DC-DC-DC converter, or linear and low-dropout (LDO) regulator. In some variations, voltage and / or current may be controlled by associated on-chip / off-chip programmable voltage or current converters, digital-to-analog converters (DACs), which, as a non-limiting example, may include an on-chip / off-chip switched resistor DAC, switched capacitor DAC, and / or an array of switched current sources.

[0214] In some variations, PMU 109 may include one or more processors to actuate switching and power regulation circuitry. In some variations, PMU 109 may be coupled to one or more processors (e.g., Figures 1A to 1D The processor 112 in the middle actuates the switching and power regulation circuit.

[0215] Temperature compensation unit

[0216] In some variations, the temperature compensation unit 115 may include one or more temperature sensors, such as a temperature-sensing FBG sensor, a thermocouple, a resistance temperature detector, a thermistor, a digital temperature sensor, or an infrared thermometer. In variations where the temperature sensor includes a temperature-sensing FBG sensor, the temperature-sensing FBG sensor may be at least partially disposed within, surrounded by, and / or enclosed by a rigid tubular structure (e.g., a rigid tube, a rigid cylinder, a rigid hose, a rigid conduit, etc.). In some variations, the rigid tubular structure may include titanium. The diameter of the temperature-sensing FBG sensor may be about or less than about one-third millimeters, about or less than about one-quarter millimeters, about or less than about one-fifth millimeters, about or less than about one-sixth millimeters, about or less than about one-seventh millimeters, about or less than about one-eighth millimeters, about or less than about one-ninth millimeters, or about or less than about one-tenth millimeters. The length of the temperature-sensing FBG sensor may be about or less than about one-hundredth of a millimeter, about or less than about one-tenth of a millimeter, or about or less than about one millimeter.

[0217] In variations of temperature sensors, including thermocouples, resistance temperature detectors, and / or thermistors, the diameter of the temperature sensor may be about or less than about one-hundredth of a millimeter, about or less than one-tenth of a millimeter, about or less than 1 millimeter, or about or less than about 10 millimeters.

[0218] In variations where the diameter of the temperature sensor is about or less than about one-hundredth of a millimeter, or about or less than about one-tenth of a millimeter, or about or less than about 1 millimeter, the temperature sensor may be disposed on, coupled to, attached to, and / or integrated with the wires of the implantable medical device (e.g., as further described below).

[0219] In variations of the temperature sensor, including digital temperature sensors and / or infrared thermometers, the temperature compensation unit 115 may include one or more integrated circuits to measure temperature changes.

[0220] In some variations, the temperature compensation unit 115 may include one or more processors to perform temperature compensation. In some variations, the temperature compensation unit 115 may be coupled to one or more processors (e.g., Figures 1A-1D The processor 112 in the middle performs temperature compensation.

[0221] processor

[0222] Return to reference Figures 1A-1DThe miniaturized FBG demodulation system 100 can be communicatively and / or operatively coupled to a processor 112. The processor 112 described herein (e.g., a central processing unit, CPU, or microprocessor unit, MPU) can process data and / or other signals to control one or more components of the miniaturized FBG demodulation system 100. The processor 112 can be configured to receive, process, compile, compute, store, access, read, write, and / or transmit data and / or other signals. In some variations, the processor 112 can be configured to access or receive data and / or other signals from the FBG sensor 106 and / or photodetector 104 and storage media (e.g., memory, flash drive, memory card). The processor 112 can be configured to run and / or execute application processes and / or other modules, processes, and / or functions associated with the miniaturized FBG demodulation system 100.

[0223] In some variations, processor 112 may be communicatively coupled (e.g., wired or wireless) to a user interface. For example, the user interface may be a display on processor 112 itself. In some variations, the user interface may be a display on any suitable computing device (e.g., computer, smartphone, tablet, etc.) communicatively coupled to processor 112. The user interface may include input devices (e.g., touchscreen, keyboard, or voice-activated input devices) and output devices (e.g., display devices), and is configured to receive input from the user. In some variations, the input device may include a touch surface for the user to provide input to the miniaturized FBG demodulation system 100 (e.g., finger contact with a touch surface).

[0224] In a variant where the miniaturized FBG demodulation system 100 is integrated into an implantable medical device, the processor 112 may be located inside or outside the implantable medical device. The processor may include instructions to automatically switch the miniaturized FBG demodulation system 100 from a power-down state to a power-on state via a power management unit 109. In the power-down state, the FBG demodulation system 100 may be in a dormant state. For example, the light source 102 and / or powered components in the FBG demodulation system 100 may be disconnected. Additionally or alternatively, the FBG demodulation system 100 may not acquire, measure, and / or sense physical signals in the power-down state. In the power-on state, the FBG demodulation system may be operable. For example, the light source 102 and / or powered components in the FBG demodulation system 100 may be turned on. Furthermore, the FBG demodulation system 100 may be configured to sense, measure, and / or acquire physical signals in the power-on state.

[0225] Processor 112 can be configured to switch the FBG demodulation system 100 from a power-down state to a power-on state and then back to a power-down state based on a power management mode of the FBG demodulation system 100 via PMU 109. For example, the power management mode can minimize the power consumption of the FBG demodulation system 100. That is, processor 112 can be configured to manage the power of the FBG demodulation system 100 via PMU 109 based on the power management mode. In some variations, processor 112 can be configured to operate the FBG demodulation system 100 continuously (i.e., continuous mode). In some variations, when the FBG demodulation system 100 is in a power-down state, the powered components and / or light source 102 of the FBG demodulation system 100 can be disconnected (e.g., by processor 112 via PMU 109). The FBG demodulation system 100 can not acquire or measure the physical signal that the FBG sensor 106 is configured to sense in the power-down state. That is, the FBG demodulation system 100 can be in a sleep state in the power-down state. In the power-on state, the powered components and / or light source 102 of the FBG demodulation system 100 can be turned on (e.g., by the processor 112 via the PMU 109). The FBG demodulation system can acquire and measure the physical signal that the FBG sensor 106 is configured to sense in the power-on state. That is, the FBG demodulation system 100 can be active in the power-on state. In some variations, the processor 112 can be configured to operate the FBG demodulation system 100 via the PMU 109 in at least five modes to minimize and / or manage power consumption, such as continuous power management mode, event-triggered mode, event-gated mode, pulse width modulation mode, and adaptive power mode. In continuous mode, the processor 112 can be configured to continuously operate the FBG demodulation system 100.

[0226] In event-triggered mode, processor 112 can be configured to trigger a power-on state upon detection of a physical event, at pre-programmed intervals, and / or upon request from a user. For example, in a power-managed event-triggered mode, processor 112 can be configured to automatically trigger a power-on state in response to a triggering physical event in the subject (e.g., detection of tachycardia, heart failure, ischemia, etc.). The triggering physical event can be detected by an implantable medical device (e.g., utilizing electrodes and / or other sensors in an implantable medical device monitoring the subject) and / or by other devices communicatively coupled to the implantable medical device (e.g., a remote monitoring platform for remotely monitoring pulmonary artery pressure, a wearable device, etc.). For example, processor 112 can receive electrocardiogram (ECG) signals from the subject (e.g., from one or more electrodes disposed in the subject). Processor 112 can analyze these ECG signals. If processor 112 identifies an arrhythmia (e.g., tachycardia) based on analysis, the processor can automatically trigger the power-on state of the miniaturized FBG demodulation system 100 via PMU 109 to assess the subject's hemodynamic status using data recorded from the miniaturized FBG demodulation system. For example, the miniaturized FBG demodulation system can be powered on and perform analysis of FBG parameters indicative of the mechanical motion of the heart (such as myocardial strain of the ventricles) when analysis of such parameters indicates the possibility of an abnormally increased heart rate (tachycardia), to assess the subject's hemodynamic status. If the analysis of such parameters indicates that one or more values ​​of the FBG parameters may reach a threshold and / or threshold range, the hemodynamic status can be considered unstable. In response to the detection of hemodynamic instability, processor 112 can automatically command an implantable medical device to perform further diagnostic tasks and / or therapeutic interventions, such as cardiac pacing and cardioversion / defibrillation, or alternatively, processor 112 can alert the subject to call for professional assistance, including emergency medical services, via audible warnings and / or vibrations and via telemetry. Additionally or alternatively, the processor 112 may include instructions to automatically turn one or more other components (e.g., powered components associated with a photodetector) on or off via a PMU 109 in a similar manner in the miniaturized FBG demodulation system 100 to reduce power consumption.

[0227] In some variations, processor 112 may be configured to analyze intrathoracic or pulmonary impedance measurements received from a subject. Intrathoracic or pulmonary impedance measurements reaching a threshold and / or threshold range may indicate a deteriorating cardiac condition (e.g., heart failure). In response to the detection of deteriorating heart failure, processor 112 may automatically trigger the power-on mode of miniaturized FBG demodulation system 100 via PMU 109. Additionally or alternatively, processor 112 may be configured to analyze pulmonary artery pressure reflecting the left atrium. In response to the detection of pulmonary artery pressure exceeding a threshold and / or threshold range that may indicate a deteriorating cardiac condition (e.g., heart failure), processor 112 may automatically trigger the power-on state of miniaturized FBG demodulation system 100 via PMU 109. In some variations, processor 112 may be configured to detect ischemia, which may be reflected in abnormalities in strain parameters during diastole and / or systole. In other variations, the subject or user may notify the processor 112 (e.g., via a user interface) that the FBG demodulation system 100 will be activated (e.g., when the subject is experiencing chest pain, shortness of breath, or fainting, or when the user determines that such activation is indicated). In response to such notification, the processor 112 may trigger the power-on state of the miniaturized FBG demodulation system 100 via the PMU 109.

[0228] In some variations, in event-triggered mode, processor 112 can automatically trigger the power-on state of the miniaturized FBG demodulation system 100 via PMU 109 at pre-programmed demodulation intervals. For example, processor 112 may include instructions to automatically trigger the power-on state via PMU 109 at specific demodulation intervals. As a non-limiting example, the power-on state may be automatically triggered once or multiple times a day or week to monitor the hemodynamic status in a subject. As yet another non-limiting example, the power-on state may be automatically triggered once or multiple times a month or several months to monitor the hemodynamic status of a subject and / or monitor the functional status of the miniaturized FBG demodulation system. In some variations, processor 112 may be configured to trigger the power-on state via PMU 109 based on a request from a user (e.g., via a user interface, which, as a non-limiting example, may be telemetry- or Bluetooth wirelessly operable).

[0229] In some variations, physical events may occur at repetitive intervals. Processor 112 can detect repetitive physical events occurring at repetitive intervals by analyzing additional physical signals (e.g., trigger physical signals). For example, processor 112 can be configured to regulate the power-on and power-off states of the miniaturized FBG demodulation system by analyzing electrocardiogram signals representing cardiac electrical activity, signals representing transthoracic and / or intrathoracic / pulmonary impedance measurements, signals representing pulmonary or systemic arterial pulse measurements, combinations thereof, and / or the like. In response to the detection of a repetitive event, processor 112 can operate the miniaturized FBG demodulation system 100 in a power-managed event-gated mode via PMU 109. In event-gated mode, processor 112 can rapidly switch the miniaturized FBG demodulation system 100 from a power-off state to a power-on state at specific time instances (e.g., gating points) within the period of the repetitive event, and switch it back to a power-off state after a short time or operating period that can be preset or dynamically determined via PMU 109. The operation period can be an hour or a fraction of an hour, a minute or a fraction of a minute, a second or a fraction of a second, a millisecond or a fraction of a millisecond, a microsecond or a fraction of a microsecond, etc. For example, processor 112 can analyze signals representing the subject's physiological condition (e.g., trigger physical signals) (e.g., ECG signals, transthoracic and / or intrathoracic impedance signals, etc.) and detect cardiac and / or respiratory cycles. In some variations, processor 112 can switch the miniaturized FBG demodulation system 100 from a powered-off state to a powered-on state via PMU 109 at the end of systole and / or end of diastole of the cardiac cycle. Then, processor 112 can switch the miniaturized FBG demodulation system 100 from a powered-on state back to a powered-off state via PMU after the preset or dynamically determined operation period as described above. In a similar manner, processor can switch the miniaturized FBG demodulation system 100 from a powered-off state to a powered-on state at the end of inspiration and / or end of expiration of the respiratory cycle. Then, the processor 112 can switch the miniaturized FBG demodulation system 100 from the power-on state back to the power-off state after a preset or dynamically determined operating period (e.g., 3 cardiac cycles).

[0230] In some variations, the miniaturized FBG demodulation system 100 can be configured to operate in pulse width modulation (PWM) mode. In PWM mode, the processor 112 can be configured to enable and disable power delivered at ultra-high frequency discrete pulses via PMU 109 to the light source 102 and / or powered components (e.g., powered components associated with photodetector 104, etc.) of the miniaturized FBG demodulation system 100, thereby further minimizing the power consumption of the FBG demodulation system. For example, the light source 102 in the miniaturized demodulation system 100 can be a pulsed light source. The power delivered to the light source allows the processor 112 to discretely switch the light source 102 from a power-off state to a power-on state at ultra-high frequency via PMU 109. For example, the discrete power pulses can have a duty cycle (e.g., ... Figure 9 The duty cycle (50% duty cycle 992, 75% duty cycle 994, and 25% duty cycle 996) indicates the proportion or percentage of time during which the light source 102 is to be turned on within the duration of the duty cycle, which is the sum of the time during which the light source 102 is to be turned on and the time during which the light source 102 is to be turned off during the duty cycle.

[0231] In some variations, the miniaturized FBG demodulation system 100 can be configured to operate in an adaptive power mode. In adaptive power mode, the processor 112 can be configured to analyze the output amplitude of the photodetector 104 (which is highly correlated with the amplitude of the physical signal sensed by the FBG sensor 106) and adjust or regulate the amount of power transmitted via the PMU 109 to the light source 102 and / or the powered components to optimize the power consumption of the FBG demodulation system. For example, the processor 112 can be configured to reduce the amount of power transmitted via the PMU 109 to the light source 102 and / or the powered components if the analysis of the output amplitude from the photodetector 104 exceeds a detection threshold. Conversely, if the analysis of the output amplitude of the photodetector is below a sensitivity threshold, the processor 112 can be configured to increase the amount of power transmitted via the PMU 109 to the light source 102 and / or the powered components.

[0232] It should be readily understood that the miniaturized FBG demodulation system 100 can be configured to operate independently or simultaneously in an event-triggered mode, an event-gated mode, a pulse width modulation mode, or an adaptive power mode. For example, the processor 112 can be configured to switch the miniaturized FBG demodulation system 100 from a power-off state to a power-on state (e.g., by turning on the light source 102) in response to the detection of tachycardia. For example, in response to determining that a subject's heart rate has exceeded 150 beats per minute, the processor can detect tachycardia. The processor 112 can then switch the miniaturized FBG demodulation system 100 from a power-off state to a power-on state. Thus, the miniaturized FBG demodulation system 100 can operate in an event-triggered mode. Additionally, the processor 112 can induce this switch only during the end-systolic and end-diastolic phases of a regular cardiac cycle for a short gating period (e.g., about 50 milliseconds or about 100 milliseconds), since the cardiac cycle is a repetitive event. Therefore, once the processor 112 detects tachycardia, it can switch the miniaturized FBG demodulation system 100 from a power-off state to a power-on state during the end-systolic and end-diastolic phases of the subject's cardiac cycle for a short operating period of approximately 50 milliseconds (as a non-limiting example). Thus, the miniaturized FBG demodulation system 100 can operate simultaneously in event-triggered and event-gated modes. Additionally, during the power-on state of the FBG demodulation system 100, the processor 112 can deliver power to the light source 102 in the form of discrete pulses with a 75% duty cycle. Furthermore, the amount of power delivered to the powered components and / or the light source 102 of the FBG demodulation system (e.g., in the form of current flowing to the light source) can be adaptively adjusted to balance the sensitivity / accuracy and power consumption of the FBG demodulation system, as described above. Therefore, the miniaturized FBG demodulation system 100 can operate simultaneously in event-triggered mode, event-gated mode, pulse width modulation mode, and adaptive power mode. Similarly, the miniaturized FBG demodulation system 100 can be configured to operate simultaneously in continuous mode, event-gated mode, pulse width modulation mode, and adaptive power mode, or combinations thereof. In some variations, only the continuous mode and the event-triggered mode can be mutually exclusive and can not operate simultaneously. In some variations, the continuous mode and the event-triggered mode can operate sequentially. Utilizing these power management modes can effectively and significantly reduce the power consumption of the miniaturized FBG demodulation system.

[0233] The power management modes described herein for managing, minimizing, or optimizing power consumption are non-limiting examples. The miniaturized FBG demodulation system 100 can be configured to operate in other suitable modes. Additionally or alternatively, the power management modes described herein can also be implemented to control the power to various components (not just the light source) of the miniaturized FBG demodulation system 100. Furthermore, it should be understood that, in addition to the miniaturized FBG demodulation system described herein, the power management modes described above can be used to manage, minimize, or optimize the power consumption of systems or devices with optical sensors (FBG sensors or non-FBG optical sensors).

[0234] In some variations, the temperature variations associated with the operation of the implantable medical device should be below a certain threshold (e.g., less than 0.02-0.03 degrees Celsius) to eliminate not only damage to biological tissue and / or the implantable medical device, but also subjective discomfort to the subject. Due to the power management mode and the optional use of a narrowband light source, the FBG demodulation system 100 described herein can generate minimal heat, thereby preventing a significant increase in temperature around the FBG demodulation system 100.

[0235] In this way, the miniaturized FBG demodulation system 100 can operate and be switched on only in response to physical events, during pre-programmed demodulation intervals, in response to user requests, and / or can be gated to recurring events. Therefore, the powered components of the FBG demodulation system and / or the light source 102 are switched on only when necessary. Furthermore, power consumption can be further optimized using adaptive power modes. This can reduce power consumption and extend the lifespan of implantable medical devices that are typically battery-powered. Power management modes that manage, minimize, or optimize power consumption can increase the durability or lifespan of implantable medical devices into which the miniaturized FBG demodulation system 100 can be integrated. In some variations, such implantable medical devices (e.g., battery-powered implantable medical devices) can have a lifespan of at least 5 years or at least 10 years. Additionally, by minimizing power consumption, the heat generated by the light source 102 (because it is switched on only when necessary) can be reduced to avoid adverse effects on surrounding tissues and organs implanted with the miniaturized FBG demodulation system, or discomfort to the subject, or adverse effects on the implanted medical device itself.

[0236] In a variant where the demodulation system is integrated into an implantable medical device, processor 112 may be configured to perform temperature compensation. In some variants, processor 112 may perform temperature compensation based at least in part on calibration features of a temperature sensor included in temperature compensation unit 115. Calibration features may be generated during the manufacturing process. Alternatively or additionally, calibration features may be generated when or immediately before implantation of the implantable medical device into a subject. As described above, calibration features may include lookup tables and / or one or more equations. In some variants, calibration features may be updated after implantation (e.g., in vivo) of the implantable medical device into the subject. For example, calibration features may be updated based on the circadian rhythm of the subject's core body temperature, which may be measured invasively (e.g., in the pulmonary artery) or non-invasively (e.g., in the rectum).

[0237] Processor 112 can perform temperature compensation based on a first signal generated by FBG sensor 106 and a second signal generated by a temperature sensor included in temperature compensation unit 115. As discussed herein, FBG sensor 106 can generate a first reflected light signal (e.g., a first signal) that can represent strain changes and temperature changes. Photodetector 104 can convert the first reflected light signal into an electrical signal (e.g., a first electrical signal). In a variant where the temperature sensor is a temperature-sensing FBG sensor, the temperature sensor can generate a second reflected light signal (e.g., a second signal) that can represent temperature changes. Photodetector (e.g., photodetector 104 and / or photodetector 104') can convert the second reflected light signal into a second electrical signal (e.g., a second electrical signal). Processor 112 can perform temperature compensation based on the first and second electrical signals. For example, processor 112 can perform temperature compensation based on the difference between the first and second electrical signals.

[0238] In a variant where the temperature sensor is not a temperature-sensing FBG sensor, the temperature sensor can generate a second signal as an electrical signal. Therefore, the processor can perform temperature compensation based on the second electrical signal from the temperature sensor and a first electrical signal (e.g., a light signal received from photodetector 104 and representing the first reflected light signal generated by FBG sensor 106).

[0239] In some variations, the processor can operate the temperature compensation unit in a gated temperature compensation mode. That is, the processor 112 can perform temperature compensation (e.g., such as...) at a predetermined time point before, during, or after a physical event, or within a predetermined time period after such a time point. Figures 14A-14C(Non-limiting examples depicted). In some variations, physical events may include the onset of ventricular activity or QRS based on cardiac electrogram analysis, end-diastolic or end-systolic phase based on cardiac mechanical motion (contraction and relaxation), end-inspiratory or end-expiratory phase based on respiratory cycle analysis, and specific time points based on body temperature-based circadian rhythm cycle analysis. In such variations, processor 112 may receive signals indicating physical events from non-FBG sensors and / or from other additional FBG sensors.

[0240] method

[0241] This article also describes methods that employ or involve FBG demodulation systems. References Figure 7 This illustrates a miniaturized FBG demodulation system (e.g., structurally and / or functionally similar to...). Figures 1A-1D A flowchart of an exemplary method 700 for an FBG demodulation system 100 in [the system]. Method 700 may include selecting a light source at 702 (e.g., structurally and / or functionally similar to [the source]). Figures 1A-1D The light source 102) and / or FBG sensor (e.g., structurally and / or functionally similar to) Figures 1A-1D (FBG sensor 106 in the example). In some variations, selecting the light source and / or FBG sensor may include determining the operating range of the FBG sensor. Selecting the light source and / or FBG sensor may include identifying a discrimination spectral domain defined in the spectrum of emission from the light source and / or the spectrum of reflection from the FBG sensor (e.g., Figure 4 The discriminant spectral domain 440a It has at least a width that can cover or conform to the operating range of the FBG sensor. In some variations, selecting the light source and / or FBG sensor may include configuring the emitted spectrum of the light source and the reflected spectrum of the FBG sensor to interact in the discrimination spectral domain, wherein the power of the reflected light signal from the FBG sensor is a monotonic function of its wavelength spectral shift.

[0242] In some variations, the selection of the light source may include optimizing the light source by means of: during pre-emission fabrication (e.g., by changing the composition of the dopants, such as changing the arsenic and / or phosphorus composition of the infrared emitter, or by changing the indium composition of the blue / green emitter) or by post-emission modification of the light source (e.g., by including wavelength filters, such as dyes, pigments, or wavelength conversion materials, such as phosphors, or by adjusting the FBG), such that the emission spectrum of the light source and the reflected spectrum of the FBG sensor interact in the discrimination spectral domain.

[0243] In some variations, selecting an FBG sensor may include changing the grating period of the FBG sensor, changing the number of gratings with a given grating period of the FBG sensor, changing the distribution pattern of gratings with different grating periods along the fiber core of the FBG sensor, changing the tilt or angle of the grating plane, changing the exposure time to ultraviolet light during grating inscription on the fiber, changing the chemical composition of the fiber core to change the refractive index, introducing a gradient in the refractive index of the fiber core (e.g., by changing the tilt or angle of the grating plane and / or changing the exposure time to ultraviolet light), combinations of these and / or similar operations, such that the discrimination spectral domain has a width that at least covers or conforms to the entire operating range of the FBG sensor. In some variations, selecting an FBG sensor may include selecting a non-uniform FBG sensor. In some variations, selecting an FBG sensor may include selecting a chirped FBG sensor.

[0244] In some variations, the method may further include dividing the spectrum of the light source's emission into multiple spectral segments. For example, one or more modulated FBGs (e.g., Figures 1A-1D The adjustment of the FBG 110 in the light source can cause the emission spectrum of the light source to be divided into multiple spectral segments. One or more of these spectral segments can each interact with the corresponding FBG sensor within the operating range of the FBG sensor.

[0245] In some variations, method 700 may include continuously operating a miniaturized FBG demodulation system. In some variations, method 700 may include automatically triggering a power-on state based on an operating mode for power management (e.g., minimizing and / or managing power consumption) of the miniaturized FBG demodulation system. For example, in event-triggered mode, method 700 may include automatically triggering a power-on state based on a physical event. The physical event may be determined at least in part based on a physical signal representing a physical condition (e.g., a triggered physical signal). For example, the FBG demodulation system may be integrated into an implantable device. The method may include receiving an ECG signal from a subject at the implantable device and estimating the occurrence of tachycardia (the physical event). In response to detecting tachycardia, the method may include automatically switching on the light source and / or powered components of the miniaturized FBG demodulation system to assess the subject's hemodynamic status. In some variations, in event-triggered mode, method 700 may include automatically triggering a power-on state at pre-programmed intervals. In some variations, in event-triggered mode, method 700 may include automatically triggering a power-on state in response to a request from a user (e.g., a demodulation request). In some variations, in event-gated mode, method 700 may include automatically triggering a power-on state at specific points in time or during periods of recurring physical events. Additionally, method 700 may include switching from a power-on state to a power-off state after a certain period of time. In some variations, method 700 may include transmitting pulsed power to the powered components and / or light source of the miniaturized FBG demodulation system. In some variations, method 700 may include adaptively adjusting the amount of power transmitted to the light source and / or powered components via a PMU to optimize the power consumption of the FBG demodulation system 100.

[0246] Powering on and / or turning on the light source allows the light source to emit an optical signal to the FBG sensor. At 704, the method may include receiving a reflected optical signal from the FBG sensor representing a change in a physical signal sensed by the FBG sensor. At 706, the method may include converting the reflected optical signal into an electrical signal. Measurement of the electrical signal can indicate a change in the physical signal. In some variations, when the miniaturized FBG demodulation system can be integrated into an implantable medical device such as an ICD, method 700 may include issuing commands or instructions to disable and / or modulate the response of the implantable medical device to perform diagnostic and / or therapeutic functions, such as pacing and cardioversion / defibrillation.

[0247] Figure 15A flowchart illustrating a method 1500 for performing temperature compensation in a miniaturized FBG demodulation system (e.g., structurally and / or functionally similar to FBG demodulation system 100). The FBG demodulation system can be integrated into an implantable medical device. Method 1500 may include performing temperature compensation to compensate for significant changes in the body temperature of a subject. At 1502, the method includes receiving a first signal representing changes in strain (e.g., myocardial strain) and / or temperature (e.g., body temperature). The first signal may be an electrical signal. The first electrical signal can be generated by converting a first reflected light signal generated by an FBG sensor (e.g., structurally and / or functionally similar to FBG sensor 106) via a photodetector (e.g., structurally and / or functionally similar to photodetector 104).

[0248] At 1506, method 1500 may include receiving a second signal representing a temperature change. The second signal may be an electrical signal. In some variations, method 1500 may include receiving the second signal from a temperature sensor included in a temperature compensation unit (e.g., structurally and / or functionally similar to temperature compensation unit 115). These temperature sensors may not be temperature-sensing FBG sensors. In some variations, method 1500 may include receiving the second signal from a photodetector. In such a variation, the method may include converting a second reflected light signal into a second signal via a photodetector. The second reflected light signal may be generated by a temperature-sensing FBG sensor included in the temperature compensation unit.

[0249] At 1508, method 1500 may include performing temperature compensation based on a first signal received at 1502 and a second signal received at 1506. In some variations, the method may include determining the difference between the first and second signals.

[0250] Integrating a miniaturized FBG demodulation system into an implantable medical device

[0251] Due to the FBG demodulation system described in this article (e.g., Figures 1A-1CThe FBG demodulation system 100 described herein can sense and measure physical signals at lower measurement frequencies without requiring bulky optical components such as optical Fabry-Perot interferometers, thus significantly reducing the size of the FBG demodulation system. Furthermore, through optoelectronic co-packaging technology, the size and volume of the light source and / or FBG sensor can be very small. Therefore, the miniaturized FBG demodulation system can be integrated into small devices. This document describes, by way of non-limiting example, the integration of the miniaturized FBG demodulation system into implantable medical devices, such as implantable pacemakers (IPMs), cardioverter defibrillators (ICDs), implantable cardiac monitors (ICMs), etc. In implantable medical devices, the miniaturized FBG demodulation system can be configured to evaluate physical signals, such as strain, pressure, temperature, etc. Physical signals can indicate the physiological and / or pathophysiological state of a subject. For example, physical signals can indicate the hemodynamic state of a subject. For example, ventricular end-diastolic strain can indicate ventricular end-diastolic volume. Similarly, ventricular end-systolic strain can indicate ventricular end-systolic volume. In some variations, the difference between end-diastolic strain and end-systolic strain can indicate stroke volume ( Figure 12E In some variations, the rate of change of strain during systole can indicate the systolic rate or systolic function of the ventricle. Similarly, the rate of change of strain during diastole can indicate the relaxation rate or diastolic function of the ventricle. The hemodynamic status of a subject can be determined during various conditions such as rest, sleep, walking, exercise, arrhythmias, heart failure (e.g., systolic, diastolic), and myocardial ischemia. Additionally, the miniaturized FBG demodulation system can be configured to reduce and / or minimize power consumption. This is important because the power supply in implantable medical devices is limited. Furthermore, the miniaturized FBG demodulation system can be configured to minimize heat generated from the implantable medical device (e.g., with reduced power consumption and a narrowband light source). Heat exceeding a certain threshold may have adverse effects on the subject (e.g., damage or discomfort to adjacent tissues and muscles) and / or on the implantable medical device.

[0252] Using an FBG demodulation system to determine the physiological and / or pathophysiological state of a subject can help induce and / or modulate the response of implantable medical devices, alert medical professionals involved in the subject's care, and prompt timely medical diagnosis and treatment.

[0253] Figure 8 A miniaturized FBG demodulation system is shown (e.g., structurally and / or functionally similar to...). Figures 1A-1CThe FBG demodulation system 100 in the image is integrated into an implantable medical device. As a non-limiting example, the implantable medical device may include a pulse generator 815 and one or more leads 817. The pulse generator 815 may include a housing portion 815a and a head portion 815b. The housing portion 815a of the pulse generator 815 may include an integrated circuit (IC) (e.g., one or more processors, memory, analog circuitry, digital circuitry, hybrid circuitry, etc.), a battery, and, if the implantable device is designed to deliver a high-energy electric shock (e.g., an ICD), a capacitive element (e.g., a capacitor) for storing charge before delivering the shock and / or other hardware components (e.g., signal processing components) for detecting arrhythmias and delivering the shock or pacing stimulation. The pulse generator 815 may be implanted in any suitable area within the subject's body. For example, the generator 815 may be subcutaneously implanted in the left or right chest region. In some variations, the pulse generator 815 can be substantially similar to the generator described in U.S. Publication No. US20200037895 (referred to as “895”), published on February 6, 2020, entitled “Non-barometric Determination of Hemodynamic Effects of Cardiac Arrhythmias Using SignalsSensed by an Implantable Device”. It should be readily understood that the terms generator and pulse generator are used interchangeably herein.

[0254] One or more leads 817 may be connected to the pulse generator 815 at the head portion 815b. In some variations, the leads 817 may be directly connected to the head portion 815b at the first end. Alternatively, in some variations, the first end of the leads 817 may be connected via a lead-generator interface unit 820 and then coupled to the pulse generator 815. The second end of the lead 817, opposite the first end, may be inserted into one of the heart chambers, the coronary sinus, and / or the pericardial cavity surrounding the heart. The leads 817 may include one or more electrodes to deliver current, such as, or to deliver low-energy electrical stimulation to stimulate tissue (e.g., myocardium similar to a pacemaker) or one or more shock coils to terminate or reset arrhythmias with high energy (i.e., cardioversion and defibrillation or ICD shock). At least some of the electrodes on one or more leads 817 may be used to sense the electrical activity of the heart (e.g., electrocardiogram). In some variations, the electrodes configured to sense electrical activity may be the same electrode / shock coil, which may be used to deliver low / high current / energy for pacing or for cardioversion / defibrillation. In other variations, electrodes configured to sense electrical activity may differ from electrodes / shock coils configured to deliver low / high current / energy for pacing or cardioversion / defibrillation.

[0255] In some variations, the implantable medical device can detect arrhythmias based on existing technologies (e.g., electrocardiogram-based technologies) from abnormal electrical activity sensed from one or more of these electrodes. In some variations, the lead 817 can be substantially similar to the lead described in the '895 disclosure, which is incorporated herein by reference in its entirety. In some variations, the lead 817 can be any suitable lead (e.g., existing lead) for the implantable medical device. Additionally, the implantable medical device can include any suitable number of leads 817. For example, a single-chamber ICD can include one lead in the right ventricle. A dual-chamber ICD can include two leads, one in the right atrium and the other in the right ventricle. A biventricular ICD can include three leads, one in the right atrium, one in the right ventricle, and one in the coronary sinus.

[0256] FBG sensor 806 (e.g., structurally and / or functionally similar to) Figures 1A-1CThe FBG sensor 806 can be embedded in one or more leads 817 of an implantable medical device. For example, lead 817 may include an optical fiber, on which the FBG sensor 806 may be formed. That is, the optical fiber may be part of lead 817. Additionally or alternatively, lead 817 may be attached to, integrated with, and / or coupled to an optical fiber, on which the FBG sensor may be formed. The FBG sensor 806 can be embedded in any existing suitable lead 817 that can be used in an implantable medical device. For example, in single-chamber and dual-chamber ICDs, the FBG sensor 806 can be embedded in a lead that can be positioned in both the right ventricle and / or the right atrium and the right ventricle. Similarly, in a biventricular ICD, the FBG sensor 806 can be embedded in a lead positioned in the coronary sinus, right atrium, and / or right ventricle. In some variations, lead 817 (e.g., lead 817 having the FBG sensor 806 embedded therein) may include a high-energy shock coil. Alternatively, the lead 817 (e.g., a lead 817 having an FBG sensor 806 embedded therein) may not include a shock coil. For example, a lead in the coronary sinus, pulmonary artery system, right atrium, or pericardial cavity may include an FBG sensor 806, but may not include a shock coil. In some variations, one or more FBG sensors 806 may be embedded in a single lead 817. Additionally, one or more FBG sensors 806 may be embedded in more than one lead 817. In some variations, one or more optical fibers may be present, each having one or more FBG sensors embedded in each of one or more leads 817.

[0257] A wire 817 embedded with an FBG sensor 806 can be coupled to a generator 815 via a wire-generator interface unit 820. The wire-generator interface unit may include an optocoupler 822 and a power management unit 825 (e.g., structurally and / or functionally similar to...). Figures 1A-1D The power management unit 109 and temperature compensation unit 840 (e.g., structurally and / or functionally similar to) Figures 1A-1D The temperature compensation unit 115 and the processor 824 (e.g., structurally and / or functionally similar to) Figures 1A-1D The processor 112 in the middle). The optocoupler (OEC) 822 may include a light source 802 (e.g., structurally and / or functionally similar to the processor 112 in the middle). Figures 1A-1D The light source 102 and photodetector 804 (e.g., structurally and / or functionally similar to) Figure 1A-1D The photodetector 104 and the optical router 808 (e.g., structurally and / or functionally similar to) Figures 1A-1DThe optical router 108 in the example. The wire-generator interface unit 820 may include a power management unit 825 (further detailed in FIG. 12), which may be electrically coupled to the optocoupler 822 and optionally other powered components. The wire-generator interface unit 820 may also include a temperature compensation unit 840. The wire-generator interface unit may also include a processor 824 communicatively coupled to the optocoupler 822 and the power management unit 825 (e.g., structurally and / or functionally similar to...). Figures 1A-1D The wire-generator interface unit may also include a power supply 826 communicatively coupled to the processor and / or electrically coupled to the light source 802. In some variations, the wire-generator interface unit may alternatively draw power from the pulse generator 815. In other variations, the wire-generator interface unit has its own dedicated power supply or battery 826. Additionally or alternatively, the wire-generator interface unit may include integrated circuits such as memory, analog circuitry, digital circuitry, mixed-signal circuitry, analog-to-digital converters, and digital-to-analog converters.

[0258] The optical signal from light source 802 can be transmitted via optical router 808 to FBG sensor 806 embedded in wire 817. Photodetector 804 can convert the reflected optical signal from FBG sensor 806 into an electrical signal via optical router 808. Processor 824 (e.g., structurally and / or functionally similar to...) Figure 1A-Figure 1B The processor 824 (112) can receive and analyze electrical signals from the photodetector 804. Based on this analysis, the processor 824 can control the functions of the implantable medical device. A power supply or battery 826 can power the light source 802 via a power management unit (PMU) 825, enabling the light source 802 to transmit light signals to the FBG sensor 806. The power supply or battery 826 can also power the powered components associated with the photodetector 804 via the PMU 825, such as the preamplifier associated with the photodetector 104, the amplifier associated with the photodetector 104, the analog-to-digital converter associated with the photodetector 104, and the filter circuit associated with the photodetector 104. It should be readily understood that the power supply or battery 826 can also power the powered components in the optocoupler 822 that are not associated with the photodetector 804 via the PMU 825. In some variations, the power supply or battery 826 can be located inside the wire-generator interface unit 820.

[0259] The lead-generator interface unit or various components of the LGIU 820 (e.g., optocoupler 822, light source 802, photodetector 804, optical router 808, processor 824, high-energy switch 828, and PMU 825) can be located at any suitable location within the implantable medical device. For example, in some variations, the various components of the LGIU 820 can be located on, attached to, integrated with, or otherwise coupled to the lead-in 817. In some variations, the various components of the LGIU 820 can be located on, attached to, integrated with, or otherwise coupled to the head portion 815b of the generator 815. In some variations, the components of the LGIU 820 may be disposed on, attached to, integrated with, enclosed within, or otherwise coupled to the housing 815a of the pulse generator 815. In some variations, some components of the LGIU 820, or elements thereof, may be positioned at a first location within the implantable medical device, while other components or elements thereof may be positioned at a second, third, or fourth location, etc. It should be readily understood that the LGIU 820 may refer to the individual components of the LGIU 820 (e.g., optocouplers, light sources, optical routers, or photodetectors or PMUs) or the individual elements that may constitute the components of the LGIU 820. For example, the light source 804 may be disposed on, attached to, integrated with, or otherwise coupled to the wire 817, while the photodetector may be disposed on, attached to, integrated with, or otherwise coupled to the head portion 815b of the pulse generator 815.

[0260] In some variations, the power management unit 825 of the wire-generator interface unit 820 may be disposed on, attached to, integrated with, or otherwise coupled to the wire 817. In some variations, the power management unit 825 may be disposed on, attached to, integrated with, or otherwise coupled to the head portion 815b of the generator 815. In some variations, the power management unit 825 may be disposed on, attached to, integrated with, enclosed within, or otherwise coupled to the housing 815a of the generator 815. In some variations, certain portions of the power management unit 825 may be located at a first position within an implantable medical device, while the remaining portions may be located at a second position within the implantable medical device. For example, the light source 802 may be coupled to, attached to, and / or otherwise integrated into one or more switching and / or power regulation circuits (e.g., the switching and / or power regulation circuitry of the power management unit). The light source 802 and coupled switching and / or power regulation circuitry can be located within the head portion 815b or housing portion 815a of the generator 815 of the implantable medical device. Similarly, the powered component of the photodetector 804 can be coupled to, attached to, and / or otherwise integrated with one or more switching and / or power regulation circuitry (e.g., the switching and / or power regulation circuitry of a power management unit). The photodetector 804 and coupled switching and / or power regulation circuitry can be located within the head portion 815b or housing portion 815a of the generator of the implantable medical device.

[0261] In some variations, the processor 824 of the wire-generator interface unit 820 may be disposed on, attached to, integrated with, or otherwise coupled to the wire 817. In some variations, the processor may be disposed on, attached to, integrated with, or otherwise coupled to the head portion 815b of the generator 815. In some variations, the processor may be disposed on, attached to, integrated with, or otherwise coupled to the head portion 815b of the generator 815. In some variations, the processor may be disposed on, attached to, integrated with, enclosed within, or otherwise coupled to the housing 815a of the generator 815. In some variations, power to the wire-generator interface unit may be supplied from a battery or a battery bank disposed inside the generator 815 (e.g., inside the housing 815a or the head 815b). Alternatively or concurrently, the wire-generator interface may be powered by a battery or a battery bank disposed outside the generator 815.

[0262] In some variations, the processor 824 of the lead-generator interface unit 820 can be configured to assess the hemodynamic status of a subject. For example, the processor can assess the subject's hemodynamic status based on analysis of one or more signals received from the optocoupler that can indicate changes in physical signals. In response to determining that the subject's hemodynamic status is stable, the processor can be configured to prevent the capacitor included in the pulse generator 815 from releasing electrical energy during non-fatal tachycardias (e.g., sinus tachycardia or atrial fibrillation) or during normal heart rhythms with electrical or electromagnetic noise or device oversensing. For example, this prevention can prevent charge from being mistakenly transferred from the capacitor to the lead 817 (e.g., by turning off the high-energy switch 828). In some variations, the high-energy switch 828 may be disposed alone or together with other components of the lead-generator interface unit in the generator housing 815a, generator head 815b, or lead 817. Alternatively, in response to determining that the subject's hemodynamic state is stable, the processor can be configured to prevent charging of the capacitor included in generator 815 during non-fatal tachycardias (such as sinus tachycardia or atrial fibrillation) or during normal heart rhythms with electrical or electromagnetic noise or device oversensing. In this way, the processor prevents implantable medical devices from erroneously delivering electric shocks.

[0263] Figures 12A-12E The power management unit 1200 is shown. Figures 12B-12E (structurally and / or functionally similar) Figure 8 The components of PMU 825 in Figure 1 and PMU 109 in Figure 1 ( Figure 12A The PMU1200 is configured to automatically turn on and off the power supply 1270 to the light source and / or other powered components, and to regulate the amount of power transmitted to the light source and / or powered components in order to achieve accurate and reliable assessment of hemodynamic status with minimal power consumption (i.e., optimized power consumption). In some variations, the operation of the PMU1200 may be controlled by a processor 1202 (structurally and / or functionally similar to...). Figure 8 The processor 824 and Figures 1A-1C The processor 112 in the processor 1202 is controlled based on a pre-programmed algorithm or instructions stored in the processor 1202 and additionally or alternatively based on the analysis of physiological signals received from sensors disposed in the subject, which may include, but are not limited to, signals disposed on a lead wire ( Figure 8 Electrocardiograms sensed by electrodes on the 817 (in the model), which can indicate respiration and / or pulmonary water content in the lungs as indicators of heart failure, transthoracic and / or intrathoracic impedance measurements, and myocardial strain signals from the miniaturized FBG demodulation system itself (e.g., Figure 8 The output of the optocoupler 822 in the middle). In some variations, Figure 12AThe processor 1202 can be configured to turn on switch 1208 to enable power supply 1270 to the light source and powered components for assessing the subject's cardiac hemodynamic status and / or mechanical function in the continuous mode as described above. In some variations, when the continuous mode operates simultaneously with event-gated mode and / or pulse mode, an interruption in power delivery to the light source and powered components may occur, as described below.

[0264] In some variations, Figure 12A The processor 1202 can be configured to turn on switch 1208 to enable power supply to the light source and the powered component 1270 via PMU 1200 to assess the hemodynamic status and / or mechanical function of the heart in the subject when needed; that is, PMU 1200 can be in event-triggered mode ( Figure 12B Operation under 1210) is based on data from the processor (e.g., Figure 12A The processor 1202 in Figure 8 The processor 824 or Figures 1A-1C The processor 1202 can communicate and / or instruct the processor 112 in order to reduce power consumption. For example, the processor 1202 can analyze communication and / or instructions from one or more electrodes located in the ventricle, epicardial cavity, or coronary sinus (e.g., Figure 8 Electrographs of the electrodes in the lead wire 817 are obtained, and ventricular electrographs (ventricular EGM) are sensed (optionally from electrodes in the atria (atrial EGM)). If the processor 1202 detects possible tachycardia or rapid arrhythmia based on this analysis which may indicate that the heart rate or ventricular rate has reached a certain rate threshold, the processor may automatically enable the power supply 1270 to the light source and the powered component 1270 via the PMU 1200 to assess the hemodynamic status and / or mechanical function of the heart in the subject. Figure 12B For example, switch 1208 is turned off until ventricular tachyarrhythmia (VT) 1212 is detected by such analysis, thereby triggering processor 1202 to turn switch 1208 on via PMU 1200 to enable power supply 1270 to the light source and powered components 1270 in order to assess the hemodynamic status and / or mechanical function of the heart in the subject during VT, such as by Figure 12BThe solid horizontal arrow starting at 1212 marks this. In some variations, this rate threshold may be user-preset, or additionally or alternatively determined based on stored data of the optocoupler output signal collected during a previous episode of normal sinus rhythm, sinus tachycardia (e.g., during exercise), and / or a previous episode of non-fatal tachycardia, optionally in conjunction with further analysis of the ventricular EGM during the current tachycardia episode (with or without analysis of concurrent atrial EGM). In some variations, EGM analysis may include, but is not limited to, analysis of ventricular EGM morphology, the sudden or gradual onset of tachycardia, and the association or dissociation between atrial and ventricular EGM, and may influence the determination of the aforementioned rate threshold and aid in the differential diagnosis of VT. Such VT may include monomorphic or polymorphic ventricular tachycardia and ventricular fibrillation. In some variations, stored data about the output of the optocoupler can be collected during a normal rhythm, during a preceding episode of sinus tachycardia (e.g., during exercise), and / or during a preceding episode of a non-fatal tachyarrhythmia. This data may include certain features (e.g., Figure 12E The electromechanical delay 1252) or the output amplitude of the optocoupler at certain time events (e.g., end-diastolic and end-systolic), as described below and its timing or phase ( Figure 12E 1250 in the middle). Once switch 1208 is turned on, the miniaturized FBG demodulation system integrated into implantable medical devices (such as ICDs) can enter the operating period to transmit signals via the FBG sensor ( Figures 1A-1C 106 and Figure 8 (806) Acquires or measures ventricular myocardial strain to assess the hemodynamic status and / or mechanical function of the subject's heart. As mentioned above, the operating period can refer to the time period during which power can be turned on to the light source and / or the powered components. At the end of the operating period, the switch can be automatically turned off, and the miniaturized FBG demodulation system integrated into an implantable medical device such as an ICD can no longer acquire or measure the changes in ventricular myocardial strain represented by the optocoupler ( ). Figure 8 822) or photodetector ( Figures 1A-1C 108 and Figure 8 The output of 804 in the middle. The duration of the operation period can be pre-programmed (e.g., seconds, minutes, or hours) or determined by processor 1202 based on the ventricular EMM (with or without an additional atrial EGM) and optocoupler ( Figure 8 822) or photodetector ( Figures 1A-1C 108 and Figure 8The process is dynamically determined by real-time analysis of the output of the PMU 1200 (804). In some variants, such analysis may also include analysis of other inputs of the PMU 1200, such as transthoracic and / or intrathoracic impedance measurements. The operation period may end when the processor determines VT termination based on analysis of the ventricular EGM and optionally additional atrial EGM. Additionally or alternatively, the operation period may end before the detected possible VT termination if the processor's analysis of the photodetector output (optionally combined with further EGM analysis) indicates a normal or stable hemodynamic state consistent with a normal or abnormal but non-fatal rhythm that might be misdiagnosed as potentially fatal VT. In some variants, such misdiagnosis may occur due to electrical noise or EGM oversensitization. In some variants, such electrical noise may include, but is not limited to, electrical noise caused by wire breakage or electromagnetic interference. In some variants, such EGM oversensitization may include T-wave oversensitization. In some variants, such abnormal non-fatal rhythm may include, but is not limited to, sinus tachycardia, supraventricular tachycardia, and atrial fibrillation with rapid ventricular response. In some variations, this abnormal non-fatal rhythm may have a ventricular rate equal to or greater than 110, 120, 150, 180, 200, 220, or 250 beats per minute. Additionally and alternatively, if analysis of the processor's output to the optocoupler or photodetector indicates a significantly impaired hemodynamic state (e.g., an acute new onset or exacerbation of heart failure), the operation period can be extended after the detected VT terminates to allow for continuous hemodynamic monitoring of the subject after VT termination, whether spontaneously terminated or successfully terminated by tachycardia therapy, which may include antitachycardia pacing, synchronized cardioversion, and / or defibrillation. The duration of this extended operation period may be pre-programmed (e.g., seconds, minutes, or hours) or dynamically determined based on the processor 1202's analysis of the input to the PMU 1200. In some variations, this antitachycardia therapy may be delivered via an ICD or via an external device such as an external defibrillator.

[0265] In some variants, the processor ( Figure 12A 1202 in Figure 8 824 and / or Figures 1A-1C(112) can control the functionality of an implantable medical device (e.g., an ICD) based on analysis of the output of the optocoupler measured or acquired during an operation period triggered by a detected possible tachycardia, as described above. For example, if analysis of the output of the optocoupler measured or acquired during the operation period indicates the presence of a stable hemodynamic state, and optionally in conjunction with analysis of ventricular EGM, by which arrhythmias detected by EGM analysis indicate a misdiagnosis caused by electrical noise or EGM oversensing, the processor can communicate with the ICD or instruct the ICD to prevent or terminate antitachycardia therapy. In some variations, preventing antitachycardia therapy may include preventing antitachycardia pacing (ATP) and / or charging of capacitors in the ICD in the event of a anticipated high-energy shock. In some variations, termination of antitachycardia therapy may be achieved by turning off a high-energy switch ( Figure 8 (828) to prevent the already charged capacitor from releasing high energy to the subject (i.e., terminating ICD discharge). As another example, if analysis of the optocoupler output measured or acquired during the operation period indicates the presence of a stable hemodynamic state, and optionally combined with analysis of ventricular EGM, by which arrhythmias detected by EGM analysis represent true ventricular tachycardia (VT), the processor can communicate or instruct the ICD to perform ATP but avoid a high-energy ICD shock. In some variations, as long as the hemodynamic state remains stable based on analysis of the optocoupler output during the detected VT, the processor can communicate or instruct the ICD to continue ATP without a high-energy ICD shock. It should be readily understood that the output of the photodetector and the output of the optocoupler are two terms that can be used interchangeably herein.

[0266] In a similar manner, processor 1202 can analyze the water content, impedance, or left atrial pressure in the subject's lungs / pleural cavity. If, based on this analysis, the processor detects potentially worsening heart failure, processor 1202 can automatically activate switch 1208 of PMU 1200 to enable power to the light source and / or powered component 1270, thereby assessing the subject's cardiac hemodynamic status and / or mechanical function. Similarly, processor 1202 can detect evidence of ischemia in response to notification of chest pain from the subject. Processor 1202 can automatically activate switch 1208 of PMU 1200 to enable power to the light source and / or powered component 1270, thereby assessing the subject's cardiac hemodynamic status and / or mechanical function. Furthermore, processor 1202 can automatically activate switch 1208 of PMU 1200 to enable power to the light source and / or other powered component 1270 at regularly scheduled intervals, thereby monitoring the subject's cardiac hemodynamic status and / or mechanical function. Furthermore, the processor 1202 can automatically turn on the switch 1208 of the PMU 1200 to enable power to the light source and / or other powered components 1270 based on a user command or request via a wireless user interface (e.g., Bluetooth or telemetry as a non-limiting example), thereby assessing the subject's hemodynamic status and / or mechanical function. It should be readily understood that the mechanical function of the heart includes its systolic and diastolic functions. In some variations, the processor can communicate with or instruct the implantable medical device to alert the subject via audible warnings and / or vibrations and / or telemetry to invoke professional assistance, including emergency medical services, based on an assessment of the subject's hemodynamic status and / or mechanical function using analysis of the optocoupler output.

[0267] In some variants, processor 1202 can be configured to turn on PMU 1200. Figure 12A The switch 1208 in the PMU 1200 enables power to the light source and / or the powered component 1270 to assess the subject's cardiac hemodynamic status and / or mechanical function during a specific portion of one or more repetitive events; that is, the PMU 1200 can be in event-gated mode. Figure 12C To reduce power consumption, the processor 1202 operates under the condition of 1220. Therefore, a single operation period can be gated to one or more repetitive events. In some variations, such repetitive events may include, but are not limited to, cardiac and respiratory cycles. For example, the processor 1202 can be configured to operate on the first three cardiac cycles following the end of inspiration 1222a, as marked by the horizontally elongated dashed arrow 1229. Figure 12CDuring a specific operating period (marked by a shorter horizontal solid arrow) of each of 1224, 1226, and 1228 in the above, switch 1208 of PMU1200 is turned on to enable power to the light source and / or the powered component 1270. In some variations, the duration of the operating period for each of the first three cardiac cycles may be the same or different. In some variations, this duration of the operating period may be pre-programmed to be approximately 0 milliseconds, at least 20 milliseconds, at least 50 milliseconds, at least 100 milliseconds, at least 150 milliseconds, or at least 200 milliseconds from the start of ventricular EGM. Alternatively or additionally, this duration of the operating period may be dynamically determined based on analysis of the output of the optocoupler or photodetector and gated to a time interval during a single cardiac cycle, as further described below. In some variations, such a specific time interval may be determined by an electromechanical delay ( Figure 12E (1252 in the text) is determined or used as a function of electromechanical delay. In some variations, such a specific time interval can be at the end of diastole (e.g., Figure 12E S in ED 1254) begins a few milliseconds or tens of milliseconds before, at the beginning of end-diastole, or a few milliseconds or tens of milliseconds after the beginning of end-diastole. In some variations, such a specific time interval may occur at end-systole (e.g., Figure 12E S in ES (1255) begins a few milliseconds or tens of milliseconds before, at the beginning of end-systole, or a few milliseconds or tens of milliseconds after the beginning of end-systole. In some variations, such a specific time interval may begin a few milliseconds or tens of milliseconds before, at, or after the beginning of end-diastole of the ventricular EGM, and end a few milliseconds or tens of milliseconds before, at, or after the beginning of the T wave (e.g., ...). Figure 12E (These are marked by vertically upward arrows). It should be readily understood that such specific time intervals can begin or end based on any combination of these time markers derived by analyzing the cardiac EGM and / or the output of an optocoupler or photodetector, depending on the specific application.

[0268] In some variations, processor 1202 may be configured to pulse-mode supply power to the light source and / or powered component 1270 via PMU 1200 during an operation period to assess the subject’s cardiac hemodynamic status and / or mechanical function during a portion of one or more repetitive events; that is, PMU 1200 may be configured to pulse in a pulsed mode. Figure 12D(1230 in the text) operates under conditions to reduce power consumption. As a non-limiting example, the duty cycle of the pulse power can be 25%, 50%, or 75%. The frequency of the pulse power can be at least several hundred Hz, at least several kHz, at least several hundred kHz, at least several MHz, at least tens of MHz, at least several hundred MHz, at least several GHz, or tens of GHz. The duty cycle and its frequency can be pre-programmed or based on the optocoupler ( Figure 8 The output of the 822 (in the text) is adaptively adjusted, as described below, to further optimize power consumption. Figure 12E ).

[0269] In some variations, processor 1202 can be configured to be based on an optocoupler ( Figure 8 The output amplitude of (822) is adaptively adjusted by PMU 1200 to transmit the amount of power to the light source and / or the powered component 1270 to assess the hemodynamic status and / or mechanical function of the subject's heart during a portion of one or more repetitive events; that is, PMU 1200 can operate in adaptive power mode ( Figure 12E The 1250 (in the example) operates at a lower power consumption. In some variations, the output amplitude of the optocoupler can be determined by the maximum and minimum values ​​of the optocoupler during a given cardiac cycle (respectively...). Figure 12E S in max 1256 and S min The difference between 1257) or the end-diastolic and end-systolic values ​​(respectively) Figure 12E S in ED 1254 and S ES The difference between 1255 and the end-diastolic and minimum values ​​(respectively) Figure 12E S in ED 1254 and S min The difference between 1257) is limited. In some variations, S ES 1255 and S min 1257 can be identical in both timing and value. In some variations, S ED 1254 and S max 1256 can typically differ in timing and value. In some variations, S ED 1254 can be delayed by a certain amount of time ( Figure 12E The electromechanical delay (or EMD 1252) occurs after the onset of ventricular electrical excitation, which can be approximately 10, 20, 50, 100, or 120 milliseconds (marked by upward-pointing solid arrows). In some variants, the EMD 1252 can be determined based on analysis of ventricular myocardial strain data extracted from the output of the optocoupler during normal rhythm and / or during a prior episode of arrhythmia. In some variants, S... ES1255 can occur at the start of the T-wave (as indicated by the upward-pointing hollow arrow). In some variations, the processor 1202 can be configured to: if the output amplitude of the optocoupler exceeds a specific detection threshold, then... Figure 12A The voltage source 1211 in the middle is in the form of a reduced voltage, or in the form of a reduced voltage. Figure 12A The power transmitted to the light source and / or powered component 1270 is reduced via PMU 1200 in the form of a reduced current from current source 1213, a reduced duty cycle, or any combination thereof as described above. In some variations, a detection threshold can be defined as the output amplitude above which sufficient hemodynamic status (e.g., sufficient stroke volume) can be accurately and reliably assessed. In some variations, processor 1202 can be configured to increase the power transmitted to the light source and / or powered component 1270 via PMU 1200 in the form of an increased voltage from voltage source 1211, an increased current from current source 1213, an increased duty cycle, or any combination thereof if the output amplitude of the optocoupler is close to or below a certain sensitivity threshold. The sensitivity threshold can be defined as the output amplitude of the optocoupler below which sufficient hemodynamic status (e.g., sufficient stroke volume) may not be accurately and reliably assessed. In some variations, the detection threshold can be greater than or equal to the sensitivity threshold. In some variations, the detection threshold and sensitivity threshold can be pre-programmed or dynamically determined based on analysis of the output amplitude data of the optocoupler during normal heart rhythms and / or previously recorded episodes of abnormal heart rhythms. In some variations, such analysis can be performed using pre-programmed algorithms and / or machine learning, based on data from the same subjects or from a similar group of subjects with implantable medical devices (e.g., ICDs). It should be understood that the light source described herein may include at least one or more light sources.

[0270] As described above, the wire-generator interface unit 820 may include a power management unit (e.g., structurally and / or functionally similar to...). Figures 1A-1C The power management unit (PMU) 109 is included to reduce and / or minimize power consumption and heat generation. In some variations, the PMU may include... Figure 12A The processor 1202 in the PMU actuates one or more switches and / or one or more power regulation circuits included in the PMU. Alternatively or otherwise, the PMU may be connected to... Figure 8 The processor 824 or Figures 1A to 1CThe processor 102 is coupled to actuate one or more switches and / or one or more power regulation circuits in the PMU. In some variations, the processor may be configured to turn on the light source and / or powered component via the PMU in response to a physical condition that meets a threshold criterion (e.g., tachycardia, heart failure, ischemia) or triggered by a physical condition that meets a threshold criterion. In some variations, the processor may be configured to automatically turn on the light source and / or powered component via the PMU at predetermined time intervals. In some variations, a user can interact with the processor via a suitable wireless user interface device (e.g., a telemetry or Bluetooth device as a non-limiting example). The processor may be configured to automatically enable power to the light source and / or powered component via the PMU in response to a request from a user. In some variations, the light source and / or powered component may be gated to repetitive physical events (e.g., cardiac cycles). In addition or alternatively, the processor may be configured to rapidly enable and disable power to the light source and powered component via the PMU based on a specific duty cycle. Additionally or alternatively, the processor can be configured to adaptively adjust the amount of power delivered to the light source and powered components via the PMU to minimize and / or optimize power consumption, while ensuring the sensitivity and accuracy of the miniaturized FBG demodulation system incorporated into implantable medical devices.

[0271] In some variations, the temperature compensation unit 840 of the lead-generator interface unit 820 may be disposed on, attached to, integrated with, or otherwise coupled to the lead 817. For example, in a variation where the temperature compensation unit 840 includes one or more temperature-sensing FBG sensors as temperature sensors, the temperature sensors may be disposed on, attached to, integrated with, or otherwise coupled to the lead 817. For example, the temperature sensors may be embedded in one or more leads 817 of an implantable medical device. In this variation, the temperature sensors may be located proximally to the lead 817, and due to the distance between the temperature sensors and / or the anatomical features of the tissue surrounding the proximal end of the lead 817, the temperature sensors may be anatomically isolated from myocardial strain sensed by the FBG sensors. For example, the proximal end of the lead may be surrounded by rigid body structures or dense fibrous tissue. If the temperature-sensing FBG sensor is positioned proximally to the lead wire, it may not be exposed to myocardial strain even if it is not located within a rigid body (e.g., the generator and / or rigid tubular structure) because the surrounding tissues and body structures are rigid (e.g., rigid bone). Additionally or alternatively, the temperature sensor may be positioned more distally at a location similar to and / or the same as the FBG sensor 806. In such variations, the temperature sensor may include a temperature-sensing FBG sensor, which must be strain-isolated, for example, by being positioned within a rigid body. In some variations, one or more temperature sensors may be embedded in one or more locations within the same lead wire 817 and / or one or more leads 817 of the implantable device in which the FBG sensor 806 is embedded.

[0272] In some variations, the FBG sensor may be embedded in a first location, and the temperature sensor may be embedded in a second location of the wire. In some variations, the first and second locations may be substantially adjacent to each other, such that the temperature exposed to the sensors is substantially the same in both locations. In some variations, the first and second locations are spaced apart from each other, such that the sensors are exposed to substantially the same temperature (e.g., because both the FBG sensor and the temperature sensor are located deep within the subject's body and exposed to the same core body temperature).

[0273] Additionally or alternatively, in variations where the temperature compensation unit includes a temperature sensor (including a thermocouple, a resistance temperature detector, and / or a thermistor), the temperature sensor may be disposed on, attached to, integrated with, or otherwise coupled to the miniaturized FBG demodulation system, rather than the wire 817. For example, the temperature sensor may be embedded in the wire-generator interface unit 820 and / or generator 815 of an implantable device, as further described below. In such variations, the temperature sensor need not be isolated from strain measurements.

[0274] In some variations, the temperature compensation unit 840 of the wire-generator interface unit 820 may be disposed on, attached to, integrated with, or otherwise coupled to the head portion 815 of the generator 815. For example, in a variation where the temperature compensation unit 840 includes an FBG sensor as a temperature sensor, the temperature sensor may be disposed on, attached to, integrated with, or otherwise coupled to the head portion 815 of the generator 815. Alternatively or in a variation of the temperature compensation unit that includes a temperature sensor (including a thermocouple, a resistance temperature detector, a thermistor, a digital temperature sensor, and / or an infrared thermometer), the temperature sensor may be disposed on the head portion 815b of the generator 815, attached to the head portion 815b of the generator 815, integrated with the head portion 815b of the generator 815, or otherwise coupled to the head portion 815b of the generator 815.

[0275] In some variations, the temperature compensation unit 840 of the wire-generator interface unit 820 may be disposed on, attached to, integrated with, or otherwise coupled to the housing 815a of the generator 815. For example, in a variation where the temperature compensation unit 840 includes an FBG sensor as a temperature sensor, the temperature compensation unit 840 may be disposed on, attached to, integrated with, enclosed within, or otherwise coupled to the housing 815a of the generator 815. In a variation of the temperature compensation unit that includes a temperature sensor (including a thermocouple, a resistance temperature detector, a thermistor, a digital temperature sensor, and / or an infrared thermometer), the temperature sensor may be disposed on the housing 815a of the generator 815, attached to the housing 815a of the generator 815, integrated with the housing 815a of the generator 815, or otherwise coupled to the housing 815a of the generator 815.

[0276] although Figure 8 The implantable medical device is described as including the lead wire 817, but it should be readily understood that the miniaturized FBG demodulation system described herein can be integrated into a leadless implantable medical device. Figure 11A A leadless implantable medical device with splines (such as, for example, 1154a, 1154b, 1154c, 1154d, collectively referred to as spline 1154) is shown. Spline 1154 can be configured to hold the implantable medical device in the appropriate location within a subject (e.g., in the right ventricle, as a non-limiting example) (i.e., passively immobilizing the device). In some variations, one or more splines 1154 of the implantable medical device configured to hold the device in place may embed one or more FBG sensors (e.g., structurally and functionally similar to...). Figures 1A-1C (FBG sensor 106 in the image). In some variations, one or more individual releasable spline 1154 may be attached, coupled to, and / or housed in one or more recesses or notches on the body of a wireless implantable medical device, and released only after implantation into the subject to make close contact with surrounding tissue, as further described below. Such individual spline may embed one or more optical fibers, each with one or more FBG sensors. Thus, some or all of the spline of an implantable medical device may embed FBG sensors and may hold the device in place, or sense physical signals, or perform both functions.

[0277] Alternatively or concurrently, some wireless implantable medical devices may include one or more grooves and / or notches on the body of the implantable medical device to accommodate one or more releasable splines coupled to the device. For example, in Figure 11B and Figure 11C In this context, leadless implantable medical devices may include grooves and / or notches along the length or a portion of the length of the body of the implantable medical device, such as, for example, 1156a and 1156b. This variation is particularly suitable for leadless implantable medical devices with active fixation, typically having a helix 1158 to hold the leadless device in the appropriate position within a subject (e.g., in the right ventricle, as a non-limiting example) (i.e., an actively fixed device). The groove may include a releasable mechanism (e.g., a spring, etc.) for inserting, for example,... Figure 11C Splines 1154a and 1154b are coupled to recesses 1156a and 1156b, respectively. During and / or shortly thereafter (e.g., minutes, hours, or days after implantation of the leadless implantable medical device into a subject), a releasable mechanism within the recess can release the splines, such that splines 1154a and 1154b are released to engage surrounding tissue, such as endocardial myocardial tissue of the right ventricle, as a non-limiting example, such as Figure 11CAs shown in the diagram. These splines can be embedded with FBG sensors to sense physical signals. Additionally or alternatively, the splines can be releasably held in grooves on the body of the wireless implantable device via a biodegradable material, such that the splines are fully embedded in the body of the wireless implantable medical device before implantation and are released only after the time required for exposure to or contact with bodily fluids (e.g., blood) during and / or after implantation. In some variations, the remaining components of the miniaturized FBG demodulation system (e.g., light source, photodetector, powered component, PMU, temperature compensation unit, etc.) can be housed within the body of the wireless implantable system. In some variations, the miniaturized FBG demodulation system can communicate wirelessly or telemetry with another implantable medical device in the subject and / or a medical device external to the subject.

[0278] Listed Examples

[0279] Example A1. A miniaturized fiber Bragg grating (FBG) demodulation system, comprising:

[0280] At least one light source having an emitted spectrum;

[0281] At least one FBG sensor, comprising a plurality of Bragg gratings, wherein the at least one FBG sensor has a reflected spectrum and is configured to receive an optical signal from the at least one light source, and the at least one FBG sensor is further configured to generate a reflected optical signal representing a change in a physical signal sensed by the at least one FBG sensor; and

[0282] A photodetector, optically coupled to the at least one FBG sensor and configured to convert reflected light signals into electrical signals.

[0283] The at least one light source and the at least one FBG sensor are configured such that the emitted spectrum and the reflected spectrum interact in the discrimination spectral domain.

[0284] Example A2. The system according to Example A1 further includes a power management unit (PMU) electrically coupled to the at least one light source, or optionally at least one powered component of the system.

[0285] Example A3. The system according to Example A2, wherein the PMU includes one or more processors configured to operate in an event-triggered mode, an event-gated mode, a pulse width modulation mode, an adaptive power mode, or a combination thereof.

[0286] Example A4. According to the system of Example A3, one or more processors are configured to automatically turn on at least one light source in response to a heart arrhythmia detected in an event-triggered mode.

[0287] Example A5. The system according to Example A3, wherein one or more processors are configured to turn on at least one light source in response to a request from a user.

[0288] Example A6. The system according to Example A1, wherein the lifespan of the system is at least 5 years.

[0289] Example A7. The system according to Example A1, wherein the at least one light source has a bandwidth in the range of about 0.1 nm to about 1.5 nm.

[0290] Example A8. The system according to Example A1, wherein the at least one light source is a doped semiconductor, a narrowband laser diode, a quantum dot, or a vertical cavity surface-emitting laser.

[0291] Example A9. The system according to Example A1, wherein the at least one FBG sensor has a bandwidth between about 0.25 nm and about 15.25 nm.

[0292] Example A10. The system according to Example A1, wherein the diameter of the at least one FBG is less than about 250 μm.

[0293] Example A11. The system according to Example A1, wherein the change in the electrical signal indicates the change in the physical signal.

[0294] Example A12. The system according to Example A1, wherein the physical signal is at least one of strain, temperature and pressure.

[0295] Example A13. The system according to Example A1, wherein the discrimination spectral domain is a region defined by at least one of a first portion of the spectrum emitted by at least one light source and a second portion of the spectrum reflected by at least one FBG sensor.

[0296] Example A14. The system according to Example A13, wherein the width of the discrimination spectral domain is at least partially based on the operating range of at least one FBG sensor.

[0297] Example A15. The system according to Example A14, wherein the operating range of the at least one FBG sensor is between about 0.5 nm and about 15 nm.

[0298] Example A16. The system according to Example A13, wherein the discrimination spectral domain is a region defined by a second portion of the reflected spectrum, and wherein the width and monotonic gradient of the discrimination spectral domain are based at least in part on the arrangement of a plurality of Bragg gratings of at least one FBG sensor.

[0299] Example A17. The system according to Example A16, wherein the arrangement includes increasing the number of the plurality of Bragg gratings, decreasing the number of the plurality of Bragg gratings, or periodically varying the plurality of Bragg gratings.

[0300] Example A18. The system according to Example A1, wherein the power of the reflected light signal changes monotonically in the discrimination spectral domain in response to a shift in the spectrum of the reflection of the at least one FBG sensor.

[0301] Example A19. The system according to Example A1, wherein the system is coupled to an implantable medical device.

[0302] Example A20. The system according to Example A19, wherein the implantable medical device is an implantable cardioverter defibrillator (ICD).

[0303] Example A21. The system according to Example A20, wherein the at least one FBG is embedded in the wires of the ICD.

[0304] Example A22. The system according to Example A21, wherein the ICD includes at least one ICD processor, the at least one ICD processor being configured to:

[0305] Receive electrocardiogram signals from at least one electrode placed in the subject; and

[0306] The subject's arrhythmia is detected based on the electrocardiogram signal.

[0307] Example B1. An implantable cardiac device, comprising:

[0308] A lead wire configured for cardioversion / defibrillation, pacing, and / or sensing, wherein the lead wire is embedded with at least one fiber Bragg grating (FBG) sensor, wherein the FBG sensor is configured to receive an optical signal from a light source, interact with the spectrum emitted by the light source in a discrimination spectral domain, and generate a reflected optical signal representing a change in the physical signal sensed by the FBG sensor.

[0309] An interface unit, the interface unit being coupled to the wire;

[0310] An optocoupler, wherein the optocoupler is disposed within the interface unit, the optocoupler comprising:

[0311] The light source;

[0312] A photodetector is used to convert reflected light signals into electrical signals; and

[0313] Processor, the processor being configured to:

[0314] Analyze the electrical signal received from the photodetector; and

[0315] The function of the implantable cardiac device is controlled based on the analysis.

[0316] Example B2. The implantable cardiac device according to Example B1, wherein the processor is coupled to the power management unit (PMU).

[0317] Example B3. An implantable cardiac device according to Example B2, wherein the PMU is configured to operate in an event-triggered mode, an event-gated mode, a pulse width modulation mode, an adaptive power mode, or a combination thereof.

[0318] Example B4. An implantable cardiac device according to Example B3, wherein the processor is configured to automatically turn on the light source in response to a detected arrhythmia in an event-triggered mode.

[0319] Example B5. An implantable cardiac device according to Example B4, wherein arrhythmias are detected based on analysis of electrograms and, optionally, myocardial strain sensed by at least one FBG sensor.

[0320] Example C1. A method comprising:

[0321] At least one of an FBG sensor and a light source is selected for the fiber Bragg grating (FBG) demodulation system, such that a first portion of the spectrum emitted by the light source is configured to interact with a second portion of the spectrum reflected by the FBG sensor in the discrimination spectral domain.

[0322] Light signals are transmitted via the light source;

[0323] Receive reflected light signals representing changes in physical signals sensed by the FBG sensor from the FBG sensor; and

[0324] The reflected light signal is converted into an electrical signal at a photodetector, wherein the measurement of the electrical signal indicates a change in the physical signal.

[0325] Example C2. The method according to Example C1 further includes using a power management unit (PMU) to reduce the power consumption of the FBG demodulation system.

[0326] Example D1. A power management unit, comprising:

[0327] A processor coupled to one or more switches; and

[0328] One or more power conditioning circuits, coupled to one or more switches, are configured to transition the FBG demodulation system from a dormant state to an operational state.

[0329] The processor is configured to operate in continuous mode, event-triggered mode, event-gated mode, pulse width modulation mode, adaptive power mode, or a combination thereof.

[0330] For purposes of explanation, the foregoing description uses specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that specific details are not necessary for practicing the invention. Therefore, for purposes of illustration and description, the foregoing description of specific embodiments of the invention is presented. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed; obviously, many modifications and variations are possible in light of the foregoing teachings. The embodiments were chosen and described to explain the principles of the invention and its practical application, and thus enable others skilled in the art to utilize the invention and various embodiments with various modifications suitable for the intended particular use. The following claims and their equivalents are intended to define the scope of the invention.

Claims

1. An implantable cardiac device, comprising: A wire, wherein the wire is embedded with at least one fiber Bragg grating (FBG) sensor, wherein the FBG sensor is configured to generate a reflected light signal in response to a received light signal, the reflected light signal representing a strain change sensed by the FBG sensor and a temperature change sensed by the FBG sensor; A temperature sensor configured to generate a first signal representing a temperature change sensed by the temperature sensor; as well as Processor, the processor being configured to: The strain change is determined based on the reflected light signal generated by the FBG sensor and the first signal generated by the temperature sensor; Analyze the strain changes; and The function of the implantable cardiac device is controlled based on the analysis.

2. The implantable cardiac device according to claim 1, wherein, The first signal generated by the temperature sensor is a first electrical signal, and the implantable cardiac device further includes: A photodetector is used to convert the reflected light signal into a second electrical signal, wherein the processor is configured to determine the strain change based on the first electrical signal and the second electrical signal.

3. The implantable cardiac device according to claim 1, wherein, The first signal generated by the temperature sensor is a first optical signal, and the implantable cardiac device further includes: Photodetectors are used for: Convert the first optical signal into a first electrical signal, and The reflected light signal is converted into a second electrical signal. The processor is configured to determine the strain change based on the first electrical signal and the second electrical signal.

4. The implantable cardiac device according to claim 1, 2 or 3, wherein, The implantable medical device is implanted into the subject's body, and the strain change represents a change in the subject's myocardial strain.

5. The implantable cardiac device according to claim 4, wherein, The changes in myocardial strain indicate the hemodynamic status of the subject.

6. The implantable cardiac device according to any one of the preceding claims, wherein, The temperature sensor includes a temperature sensing FBG sensor.

7. The implantable cardiac device according to any one of the preceding claims, wherein, At least a portion of the temperature sensor is disposed within a rigid body.

8. The implantable medical device according to any one of the preceding claims, wherein, The temperature sensor is embedded in the wire.

9. The implantable cardiac device according to claim 8, wherein, The wire has the temperature sensor embedded at a first position and the FBG sensor embedded at a second position, the first position being adjacent to the second position.

10. The implantable cardiac device according to any one of the preceding claims, wherein, The processor is configured to access the calibration features of the temperature sensor. The calibration features of the temperature sensor are generated during at least one of the manufacturing process of the implantable cardiac device or prior to implantation of the implantable cardiac device, and the temperature sensor is calibrated based on a calibration signal generated by the temperature sensor for known temperature variations.

11. The implantable cardiac device according to claim 10, wherein, The processor is also configured to recalibrate the temperature sensor after the implantable cardiac device has been implanted in a subject, the recalibration being at least in part based on the subject’s circadian rhythm of body temperature.

12. The implantable cardiac device according to any one of the preceding claims, wherein, The processor is configured to determine the strain change based on the occurrence of physical events.

13. The implantable cardiac device according to claim 12, wherein, The processor is configured to determine the strain change at a first time point during the physical event or at a first time period during the physical event.

14. The implantable cardiac device according to claim 12 or 13, wherein, The physical event is a periodic event, and the periodic event is at least one of a cardiac cycle, a respiratory cycle, or a circadian rhythm cycle.

15. A method comprising: Receive the first signal representing changes in myocardial strain and body temperature sensed by the FBG sensor; Receive a second signal representing changes in body temperature sensed by a temperature sensor; as well as The processor determines the change in myocardial strain based on the first signal and the second signal.

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