Systems, devices, and methods for miniaturization of fiber bragg grating interrogation integrated into implantable devices

Abstract

A miniaturized fiber Bragg grating (FBG) interrogation system may include a light source, an FBG sensor, and a photodetector. The FBG sensor may be configured to receive a light signal from the light source, interact with a transmitted spectrum of the light source over a distinct spectral domain, and generate a reflected light signal representative of a change in a physical signal sensed by the FBG sensor. The discriminating spectral domain may be a region defined by at least one of a transmission spectrum of the light source and a reflection spectrum of the FBG sensor. A width of the discriminating spectral domain may be based at least in part on an operating range of the FBG sensor. In the distinct domain region, the power of the reflected light signal may monotonically vary in response to an offset in the reflection spectrum of the FBG sensor. The photodetector may convert the reflected light signal into an electrical signal. In addition, the system may include a power management unit configured to reduce power consumption in order to extend the lifetime of the system.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application No. 63 / 336,909, filed on April 29, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates generally to the field of fiber Bragg grating interrogation. In particular, the present invention relates to the miniaturization of fiber Bragg grating interrogation for integration into implantable devices. Background Art

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

[0005] Challenges associated with adopting FBG sensor technology into small form factor devices (e.g., implantable devices) are generally associated with, but not limited to, the physical size and power limitations of the FBG interrogator (e.g., battery powered devices). An FBG interrogator is an optoelectronic measurement unit that provides a light source to the FBG sensor and converts the optical signal received from the FBG sensor into an electrical signal, thereby enabling measurement of the physical signal sensed by the FBG sensor.

[0006] Some implantable medical devices are configured to monitor physiological or pathophysiological conditions, and therefore may need to measure physical signals associated with those conditions. Typically, such physical signals fall within a low measurement frequency range (e.g., less than 100 Hz). For example, the measurement of the movement of the heart during the cardiac cycle may occur at less than 5 Hz. For low measurement frequency applications, conventional FBG interrogators typically utilize Fabry-Perot interferometers, broadband light sources, and other optical components to acquire sensor data and measure physical signals. Although Fabry-Perot interferometers can provide reliable and accurate measurements of physical signals with lower measurement frequencies and a larger range of values, their size is bulky. In addition, the broadband light sources utilized by these low measurement frequency FBG interrogators may increase the physical size of the FBG interrogator and may increase power consumption.

[0007] There are some FBG interrogators for high frequency measurement applications (e.g. hydrophone and seismological applications). However, high frequency measurement FBG interrogators are specifically designed to measure physical signals having a high measurement frequency but generally having a narrow range of values. More specifically, it is generally not desirable for such FBG interrogators to measure a large range of values ​​(such as a large range of strain values). Typically, mechanical events in a biological subject or system have a low measurement frequency range and relatively large values. For example, measurement of the movement of a portion of the heart (such as the movement of the ventricular wall during the cardiac cycle) can occur at less than 5 Hz with a relatively large range of values ​​from a few millimeters to a few centimeters.

[0008] Therefore, there is a need for FBG interrogators that are physically small so that they can be integrated into implantable medical devices (e.g., battery-powered implantable medical devices). In addition, there is a need for FBG interrogators that consume low power. For these implantable medical device FBG interrogators, it would be useful to have reduced heat generation and a long life (e.g., at least 5 years or even more than ten years) after implantation. In addition, low power consumption is critical to making the physical size of the FBG interrogator small because the battery is the largest component by volume in an implantable medical device. For example, the battery can represent up to 30-40% of the volume of an implantable cardioverter / defibrillator (ICD). Summary of the invention

[0009] A fiber Bragg grating (FBG) interrogation system of small physical size ("compact") is described herein. The physical size can be reduced by excluding bulky optical filters from the system and instead using light sources and FBG sensors that are adapted in both spectral range and width within a distinguishing spectral domain. In the absence of bulky optical filters, the interrogator portion of the system, such as the light source, photodetector, optocoupler, and associated components (e.g., processor, power supply, power management unit) can then be of a size that can be implanted in a subject. For example, the FBG interrogation system can be included in various implantable devices (such as implantable cardioverters / defibrillators). A power management unit can also be included in the FBG interrogation system to control power usage in order to extend the life of the system. For example, the power management unit can be configured to operate in an event-triggered mode, where the light source and / or powered components of the system can be turned on (e.g., automatically) by a triggering event (e.g., arrhythmia).

[0010] The FBG interrogation system may include at least one light source having a transmission spectrum and at least one FBG sensor having a reflection 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 transmission spectrum and the reflection spectrum interact in a distinguishing spectral domain. In some instances, and in response to a shift in the reflection spectrum of the at least one FBG sensor, the power of the reflected optical signal may vary monotonically in the distinguishing spectral domain.

[0011] The FBG sensor may also be configured to generate a reflected light signal representing a change in a physical signal sensed by the at least one FBG sensor. In addition, the FBG interrogation system may include a photodetector optically coupled to the at least one FBG sensor, configured to convert the reflected light signal into an electrical signal. A change in the electrical signal may indicate a change in the physical signal. The physical signal may be strain, temperature, pressure, or a combination thereof.

[0012] A power management unit (PMU) for controlling activation (e.g., turning on / off) of a light source and / or other powered components may also be included in the FBG interrogation system. The PMU may be electrically coupled to at least one light source and, optionally, to at least one powered component of the system. In other words, the PMU may be electrically coupled to at least one light source, at least one powered component of the system, or both at least one light source and at least one powered component of the system. Exemplary powered components may be preamplification components, amplification components, and / or analog-to-digital conversion components. 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 request from a user. In 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 an event-triggered mode, the one or more processors may be configured to automatically turn on at least one light source in response to a detected arrhythmia.

[0013] The light source that can be included in the FBG interrogation system can have a bandwidth ranging from about 0.1 nm to about 1.5 nm, including all values ​​and sub-ranges 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.

[0014] FBG sensors that may be included in the FBG interrogation 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 the FBG sensor can be about 0.25 nm, about 0.75 nm, about 1.25 nm, 1.75 nm, about 2.25 nm, about 2.75 nm, about 3.25 nm, about 3.75 nm, about 4.25 nm, about 4.75 nm, about 5.25 nm, about 5.75 nm, about 6.25 nm, about 6.75 nm, about 7.25 nm, about 7.75 nm, about 8.25 nm, about 8.75 nm, about 9.25 nm, about 9.75 nm, about 10.25 nm, about 10.75 nm, about 11.25 nm, about 11.75 nm, about 12.25 nm, about 12.75 nm, about 13.25 nm, about 13.75 nm, about 14.25 nm, about 14.75 nm, or about 15.25 nm. In some variations, the diameter of the FBG sensor is less than about 250 μm. In another variation, the FBG sensor may be a non-uniform FBG sensor. In one variation, the FBG sensor may be a chirped FBG sensor.

[0015] As further described herein, the distinguishing spectral domain can be a region defined by at least one of a first portion of a transmission spectrum of at least one light source and a second portion of a reflection spectrum of at least one FBG sensor. When the distinguishing spectral domain is a region defined by a first portion of a transmission spectrum of at least one light source, the at least one light source can be a vertical cavity surface emitting laser.

[0016] The width of the distinguishing spectral domain can be based at least in part on the operating range of the at least one FBG sensor. The operating range of the at least one FBG sensor can be between about 0.5 nm and about 15 nm, including all values ​​and subranges therein. For example, the operating range of the 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 distinguishing spectral domain is a region defined by the second portion of the reflection spectrum, the width and monotonic gradient of the distinguishing spectral domain can be based at least in part on the arrangement of multiple Bragg gratings of at least one FBG sensor. The arrangement can include an increase in the number of Bragg gratings of the FBG sensor, a decrease in the number of Bragg gratings of the FBG sensor, or a gradual change in the periodicity of the Bragg gratings.

[0017] The FBG interrogation system described herein can be coupled to various devices suitable for implantation in a subject. For example, the FBG interrogation system can be coupled to an implantable cardioverter / defibrillator (ICD). The FBG sensor can be coupled to a leadless ICD or embedded in the leads of the ICD. In some variations, the ICD can include at least one processor configured to receive an electrocardiogram signal from at least one electrode disposed in a subject and detect an arrhythmia in the subject based on the electrocardiogram signal.

[0018] Various implantable cardiac devices including FBG interrogation systems are also described herein. In one example, the 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. At least one FBG sensor may be configured to receive an optical signal from a light source, interact with a transmission spectrum of the light source in a distinguishing spectral domain, and generate a reflected optical signal representing a change in a physical signal sensed by the FBG sensor. In addition, 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 control the function of the implantable cardiac device based on the analysis. The processor may be coupled to a power management unit (PMU). As further described herein, 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. In some variations, it may be useful for the PMU to operate in an event-triggered mode and automatically turn on a light source and / or other powered components in response to a detected arrhythmia (e.g., a ventricular tachyarrhythmia). As further described below, arrhythmias may be detected based on analysis of an electrogram and, optionally, myocardial strain sensed by at least one FBG sensor. In other words, arrhythmias may be detected based on analysis of an electrogram, myocardial strain sensed by at least one FBG sensor, or both.

[0019] In some variations, a miniaturized fiber Bragg grating (FBG) interrogation 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 transmission spectrum of the at least one light source on a distinguishing spectral domain, and generate a reflected optical signal representing a change in a physical signal sensed by the at least one FBG. The distinguishing spectral domain may be a region defined by at least one of a first portion of the transmission spectrum of the at least one light source and a second portion of the reflection spectrum of the at least one FBG. The width of the distinguishing spectral domain may be based at least in part on an operating range of the at least one FBG. In response to a shift in the reflection spectrum of the at least one FBG, the power of the reflected optical signal may vary monotonically on the distinguishing spectral domain. 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.

[0020] In some variations, the distinguishing spectral domain may be defined by a second portion of the reflection spectrum of at least one FBG. The width and monotonic gradient of the distinguishing spectral domain may be based at least in part on the arrangement of the Bragg gratings of at least one FBG. In some variations, the arrangement may include increasing the number of first periodic Bragg gratings to increase the power of the reflected optical signal of the first wavelength, and reducing the number of second periodic Bragg gratings to reduce the power of the reflected optical signal of the second wavelength, thereby expanding the width of the distinguishing spectral domain of the reflection spectrum of at least one FBG.

[0021] In some variations, the distinguishing spectral domain may be defined by a second portion of a reflection spectrum of at least one FBG. The periodicity of the Bragg grating of at least one FBG may be gradually varied. In some variations, the distinguishing spectral domain may be defined by a first portion of a transmission spectrum of at least one light source. At least one light source may be a vertical cavity surface emitting laser.

[0022] In some variations, the physical signal may be at least one of strain, temperature, and pressure. In some variations, the miniaturized FBG interrogation system may be configured for low frequency measurements. In some variations, the length of at least one light source may be less than 10 mm, and the diameter of at least one light source may be less than 6 mm. In some variations, the size of at least one FBG may be less than 250 μm. In some variations, the life of the miniaturized FBG interrogation system may be at least 5 years or at least 10 years.

[0023] In some variations, the miniaturized FBG interrogation system may be coupled to a processor configured to automatically turn on the at least one light source in response to the physical condition satisfying at least one threshold criterion. In some variations, the miniaturized FBG interrogation system may be coupled to a processor configured to automatically turn on the at least one light source at predetermined intervals. In some variations, the miniaturized FBG interrogation system may be coupled to a processor configured to turn on the at least one light source in response to a request from a user.

[0024] In some variations, the miniaturized FBG interrogation system may be coupled to an implantable cardioverter / defibrillator (ICD). For example, the miniaturized interrogation system may be coupled to a leadless ICD. At least one FBG may be embedded in the leads of the ICD. In some variations, the ICD may include at least one processor for: receiving an electrocardiogram signal from at least one electrode disposed in a subject, and detecting an arrhythmia in the subject based on the electrocardiogram signal. In response to detecting a rapid arrhythmia in the subject, the at least one processor may also be configured to send an instruction 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 a measurement of the subject's lung water content and pressure in a blood vessel, and detecting the possibility of heart failure based on the impedance signal. In response to detecting the possibility of heart failure, the at least one processor may also be configured to send an instruction to turn on at least one light source.

[0025] In some variations, at least one FBG may be a first FBG, and the miniaturized FBG interrogation system may further include: a second FBG optically coupled to at least one light source. The second FBG may be configured to adjust at least one light source so that the transmission spectrum includes a plurality of spectral segments. In some variations, at least one FBG may include a plurality of FBGs. In some variations, a plurality of FBGs may be formed on a single optical fiber. In some variations, the transmission spectrum of at least one light source may include a plurality of spectral segments. In some variations, each of the plurality of spectral segments may include a corresponding first end having a first decreasing slope and a corresponding second end having a second decreasing slope. In some variations, each of the plurality of spectral segments may be configured to interact with a corresponding reflection spectrum of each FBG in the plurality of FBGs on a corresponding distinguishing spectral domain. In some variations, at least one light source may include a plurality of light sources. In some variations, each of the plurality of FBGs may receive a corresponding optical signal from a corresponding light source in the plurality of light sources.

[0026] 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. The narrowband laser diode may be a distributed feedback diode. The 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.

[0027] In some variations, the miniaturized FBG interrogation system may be coupled to a processor configured to operate the miniaturized FBG interrogation 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 (one or more) powered components may be continuous. In the second power management mode, the processor may be configured to automatically turn on at least one light source and, optionally, turn on (one or more) powered components at predetermined intervals, or in response to a request from a user, in response to a physical condition that satisfies at least one threshold criterion. In the third power management mode, at least one light source and optionally (one or more) powered components may be configured to turn on and off based at least in part on recurring physical events. In the fourth power management mode, the power transmitted to the light source and optionally (one or more) powered components may be in the form of discrete pulses. In the fifth power management mode, the amount of power transmitted to the light source and optionally (one or more) powered components may be adaptively adjusted to optimize power consumption.

[0028] In some variations, an implantable cardiac device may include: a lead for cardioversion, defibrillation or pacing and for sensing cardiac electrical (EGM) signals, a pulse generator, and a lead-generator interface unit coupled to the lead and the pulse generator. The lead may be embedded with 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 a transmission spectrum of the light source on a distinguishing spectral domain, and generate a reflected optical signal representing a change in a physical signal sensed by the FBG sensor. The lead-generator interface unit may include: an optocoupler, the 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 function of the implantable cardiac device based on the analysis.

[0029] In some embodiments, the distinctive spectral domain can be a region defined by at least one of a first portion of a transmission spectrum of at least one light source and a second portion of a reflection spectrum of at least one FBG, the width of the distinctive spectral domain can be based at least in part on an operating range of the FBG, and in response to a shift in the reflection spectrum of the FBG, the power of the reflected optical signal can vary monotonically over the distinctive spectral domain.

[0030] In some variations, the implantable cardiac device may further include a pulse generator coupled to the interface unit and the leads to deliver current or energy for cardioversion, defibrillation, and / or pacing. In some variations, at least a portion of the optocoupler may be disposed in the pulse generator. In some variations, the processor may be disposed in the pulse generator. In some variations, the interface unit may be integrated into the pulse generator.

[0031] In some variations, the processor may be configured to: assess the hemodynamic state of the subject based on the electrical signal from the photodetector, and in response to determining that the state is stable, prevent electrical energy from being discharged from a capacitor included in the generator through the lead to the subject. In some variations, the processor may be configured to: assess the hemodynamic state of the subject based on the electrical signal from the 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.

[0032] In some variations, the processor may be configured to automatically turn on a 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 state based on electrical signals from a photodetector. In some variations, the processor may be configured to receive an electrocardiogram signal from an electrode disposed within the subject, and to automatically turn on a light source based at least in part on the electrocardiogram signal. In some variations, the processor may be configured to automatically turn on a light source in response to a physical condition satisfying at least one threshold criterion. In some variations, the processor may be configured to automatically turn on a light source at predetermined time intervals. In some variations, the processor may be configured to automatically turn on a light source in response to a request from a user.

[0033] Also described herein is a method for employing an FBG interrogation system. In general, the method may include selecting a light source and an FBG sensor so that a first portion of the transmission spectrum of the light source is configured to interact with a second portion of the reflection spectrum of the FBG sensor on a distinguishing spectral domain, transmitting an optical signal via the light source, receiving a reflected optical signal representing a change in a physical signal sensed by the FBG sensor from the FBG sensor, and converting the reflected optical signal 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 distinguishing spectral domain may be based at least in part on an operating range of the FBG. In response to a shift in the reflection spectrum of the FBG, the power of the reflected optical signal may vary monotonically on the distinguishing spectral domain. The method may also include reducing the power consumption of the FBG interrogation system using a power management unit (PMU).

[0034] In some variations, the method may include: selecting at least one of a light source and a fiber Bragg grating (FBG) so that a first portion of the transmission spectrum of the light source is configured to interact with a second portion of the reflection spectrum of the FBG on a distinguishing spectral domain, transmitting 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. The measurement of the electrical signal may indicate a change in the physical signal. The distinguishing spectral domain may be a region defined by at least one of a first portion of the transmission spectrum of at least one light source and a second portion of the reflection spectrum of at least one FBG. The width of the distinguishing spectral domain may be based at least in part on an operating range of the FBG. In response to a shift in the reflection spectrum of the FBG, the power of the reflected optical signal may vary monotonically on the distinguishing spectral domain. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 An exemplary variation of a miniaturized FBG interrogation system is shown.

[0036] Figure 2A Exemplary variations of the transmission spectra of a light source having a single spectral segment are shown.

[0037] Figure 2B Exemplary variations of the transmission spectrum of a light source having a plurality of continuous spectral segments are shown.

[0038] Figure 2C Exemplary variations of the transmission spectra of a light source having a plurality of non-contiguous spectral segments are shown.

[0039] Figure 3A An exemplary variation of the reflection spectrum of a FBG sensor with a single spectral segment is shown.

[0040] Figure 3B An exemplary variation of the reflection spectrum of a FBG sensor with a plurality of consecutive spectral segments is shown.

[0041] Figure 4 An exemplary variation of distinguishing spectral domains is shown.

[0042] Figure 5A Exemplary variations of the transmission spectrum of the light source and the reflection spectrum of the FBG sensor are shown, which are configured to interact with each other over a distinct spectral domain defined by the transmission spectrum of the light source.

[0043] Figure 5B Exemplary variations of a transmission spectrum of a light source and a reflection spectrum of a FBG sensor are shown, which are configured to interact with each other over a distinct spectral domain defined by the reflection spectrum of the FBG sensor.

[0044] Figure 6A-6EThe interaction between an exemplary transmission spectrum of a light source and an exemplary reflection spectrum of a FBG sensor in a distinct spectral domain is shown.

[0045] Figure 7 is a flow chart illustrating an exemplary method of miniaturizing a FBG interrogation system.

[0046] Figure 8 An exemplary integration of a miniaturized FBG interrogation system into an implantable medical device is shown.

[0047] Fig. 9 Exemplary duty cycles of power delivered to the light source(s) and / or powered components are shown when the FBG interrogation system is operated in a pulse width modulation mode of power management to minimize power consumption.

[0048] Fig.10 An exemplary interaction between the reflection spectrum of a FBG sensor and the transmission spectra of two light sources is shown.

[0049] Figure 11A-11C An exemplary integration of a miniaturized FBG interrogation system into a leadless implantable medical device is shown.

[0050] Figure 12A-12E The operation of an exemplary power management unit of a miniaturized FBG interrogation system is shown. DETAILED DESCRIPTION

[0051] Non-limiting examples of various aspects and variations of the present invention are described herein and shown in the accompanying drawings. A "subject" or "subjects" as disclosed herein may include a human subject or patient in which an implantable medical device has been implanted or indicated for implantation. An "implantable medical device" as disclosed herein may be a small-sized device that can be introduced in whole or in part 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) interrogation system" as disclosed herein may be collectively referred to as an FBG sensor and an associated miniaturized FBG interrogator.

[0052] Described herein are systems, devices, and methods for miniaturization of fiber Bragg grating (FBG) interrogators. The technology disclosed herein can be used in any suitable application, particularly where available space is limited. For example, the technology disclosed herein can be used in implantable medical devices (IMDs) (such as implantable pacemakers (IPMs), implantable cardioverters / 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 interrogation system is integrated into an implantable medical device (such as a lead-based ICD or a leadless ICD). In some variations, the miniaturized FBG interrogation system is integrated into an implantable medical device (such as a lead-based IPM or a leadless IPM).

[0053] FBG sensors can be used to sense physical signals representing parameters such as temperature, pressure, strain, etc. FBG sensors can be formed within an optical fiber by introducing periodic changes (i.e., gratings) in the refractive index of the core of the optical fiber. When light is transmitted to the optical fiber, the grating reflects light of a specific wavelength. Light of the remaining wavelengths can be transmitted through the optical fiber unimpeded. When the optical fiber is exposed to a change in a physical parameter (e.g., a change in a physical signal), the 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 a "sensed physical signal").

[0054] As discussed above, conventional FBG interrogators for low measurement frequencies and large ranges of values ​​of physical signals may include (one or more) broadband light sources, optical filters, (one or more) interferometers, and the like, which make conventional FBG interrogators bulky. In addition, conventional FBG interrogators consume a large amount of power (e.g., at least in part due to the inclusion of (one or more) broadband light sources). As a result, FBG sensors have not been integrated into implantable medical devices (such as ICDs), which are typically small in size and have limited power sources (e.g., provided by batteries).

[0055] Disclosed herein is a miniaturized FBG interrogation system that can be integrated into a small size device. For example, the miniaturized FBG interrogation system can be integrated into an implantable medical device, as further described herein. For example, the miniaturized FBG interrogation system can be integrated into an ICD to determine the hemodynamic state of a subject during an arrhythmia, 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 hemodynamic state in the subject. An inappropriate ICD shock can refer to an ICD discharge caused by an electrocardiographic signal of a non-lethal arrhythmia or electrical / electromagnetic noise that mimics a lethal or potentially lethal arrhythmia (such as ventricular tachycardia and ventricular fibrillation). A premature ICD shock can refer to an ICD discharge during ventricular tachycardia when the subject is hemodynamically stable, in which case an alternative therapy such as anti-tachycardia pacing (ATP) may be a more appropriate treatment than an ICD shock. The miniaturized FBG interrogation system described herein can be energy efficient. In particular, the miniaturized FBG interrogation system may be configured to consume less power. Additionally or alternatively, the miniaturized FBG interrogation system may be configured to generate minimal heat, and thus may be suitable for implantation in a subject.

[0056] The miniaturized FBG interrogation system can include a light source for transmitting an optical signal, a FBG sensor for generating a reflected optical signal representing a change in a physical signal, and a photodetector for converting the reflected optical signal into an electrical signal indicating the change in the physical signal. The size of the light source can be designed for integration into an implantable medical device, as further described herein. At a high level, the light source and / or the FBG sensor of the miniaturized FBG interrogation system can be configured to interact with each other so that the miniaturized FBG interrogation system is sensitive to changes in the physical signal sensed by the FBG sensor within the operating range of the FBG sensor.

[0057] For example, the light source and / or the FBG sensor may be designed so that the transmission spectrum of the light source may interact with the reflection spectrum of the FBG sensor in a distinguishing spectral domain, as further described herein. For example, the transmission spectrum of the light source may be configured to overlap and interact with the reflection spectrum of the FBG sensor in a distinguishing spectral domain. The distinguishing spectral domain may be a region defined by a portion of the transmission spectrum of the light source and / or a portion of the reflection spectrum of the FBG sensor. For example, the distinguishing spectral domain may be a region within the transmission spectrum of the light source and / or within the reflection spectrum of the FBG sensor. In the distinguishing spectral domain, the power of the reflected light signal from the FBG sensor may vary monotonically in response to a shift in the reflection spectrum of the FBG sensor (such as in response to a change in a physical signal sensed by the FBG sensor). Simply put, the distinguishing spectral domain may be a region in the transmission spectrum of the light source and / or in the reflection spectrum of the FBG sensor, which may be highly sensitive to changes in the physical signal sensed by the FBG sensor.

[0058] The width of the distinguishing spectral domain may be determined based on the operating range of the FBG sensor. In some variations, the width of the distinguishing spectral domain may conform to the operating range of the FBG sensor. For example, the minimum width of the distinguishing spectral domain may be based on the operating range of the FBG sensor. In some variations, the operating range of the FBG sensor may in turn be determined based on the range of the physical signal that the FBG sensor is configured to sense. For example, as a non-limiting example, if the miniaturized FBG interrogation system is configured to measure strain in the heart of a subject, the myocardial strain at the end of diastole and the myocardial strain at the end of systole generated by the mechanical motion (i.e., contraction and relaxation) that the heart may experience during the cardiac cycle may 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 may be the response of the FBG sensor within the range of the physical signal that the FBG sensor is configured to sense. For example, the operating range of the FBG sensor may cover the response of the FBG sensor to the myocardial strain at the end of diastole and the response of the FBG sensor to the myocardial strain at the end of systole. Thus, the transmission spectrum of the light source can be configured to interact with the reflection spectrum of the FBG sensor over the operating range of the FBG, making the miniaturized FBG interrogation system highly sensitive to changes in physical signals within the operating range.The terms "myocardial strain" and "myocardial wall strain" are used interchangeably herein.

[0059] Example System

[0060] Figure 1An exemplary variation of a miniaturized FBG interrogation system 100 is shown. Miniaturized FBG interrogation 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 optional conditioning FBGs 110, one or more optical routers 108, and a power management unit (PMU) 109. It should be readily understood that an optical router (e.g., optical router(s) 108) may relay or direct optical signals between different components in FBG interrogation system 100, and may include components such as optical couplers, optical splitters, optical circulators, optical switches, combinations thereof, and the like. Light source(s) 102 may be optically coupled to FBG sensor(s) 106. Light source(s) 102 may transmit optical signals to FBG sensor(s) 106. FBG sensor(s) 106 may receive optical signals from light source(s) 102, and may generate reflected optical signals representative of changes in physical signals (e.g., changes in physical parameters such as strain, vibration, pressure, temperature, and the like). The reflected light signal may be received at a photodetector 104 optically coupled to a FBG sensor 106. The photodetector 104 may convert the reflected light signal into an electrical signal. The electrical signal may indicate a change in a physical signal. In this manner, the miniaturized FBG interrogation system 100 may measure changes in a physical signal.

[0061] In some variations, the miniaturized FBG interrogation system 100 may also include a power management unit (PMU) 109, which may be designed to minimize and / or reduce the power consumption of the FBG interrogation system 100. The PMU 109 may be coupled to the (one or more) light sources 102 and / or the (one or more) photodetectors 104. In some variations, the PMU 109 may be coupled to one or more powered components ( Figure 1104), such as, for example, pre-amplification component(s) (e.g., associated with photodetector(s) 104), amplification component(s) (e.g., associated with photodetector(s) 104), analog-to-digital conversion component(s) (e.g., associated with photodetector(s) 104), filtering circuit(s) (e.g., associated with photodetector(s) 104), etc. In some variations, the miniaturized FBG interrogation system 100 may include one or more conditioning FBGs 110 to adjust the transmission spectrum of the light source 102, as further described herein. In some variations, the miniaturized FBG interrogation system 100 may include one or more optical routers 108 that direct or relay optical signals between different components of the system 100 (e.g., light source(s) 102, FBG sensor(s) 106, photodetector(s) 104, and conditioning FBG(s) 110). The miniaturized FBG interrogation system 100 may be communicatively and / or operably coupled to a processor 112. For example, the processor 112 can be coupled to the (one or more) light sources 102, the photodetector 104, and the PMU 109 to control (one or more) operations, including turning on or off the power supply to one or more of the electrical components of the miniaturized FBG interrogation system 100. For example, the processor 112 can control the power supply to the light source 102 and the photodetector (104) via the power management unit (109), as further described herein. Additionally or alternatively, the processor 112 can be configured to tune the wavelength spectrum of the (one or more) light sources 102, as further described herein. Additionally or alternatively, the processor 112 can be coupled to the photodetector 104 to analyze changes in the physical signal measured by the miniaturized FBG interrogation system 100.

[0062] light source

[0063] The light source(s) 102 may be configured to generate optical signals that may be transmitted to the FBG sensor(s) 106. Some non-limiting examples of the light source(s) 102 may include vertical cavity surface emitting lasers, doped light emitting diodes (LEDs) (e.g., infrared emitters with varying arsenic and / or phosphorus doping compositions, blue / green emitters with varying indium doping compositions, etc.), LEDs coated with wavelength filters (e.g., LEDs coated with phosphors or phosphor plates, etc.), distributed feedback diodes, distributed Bragg reflector diodes, quantum dots, etc.

[0064] The optical signal generated by the (one or more) light sources 102 may be located within the transmission spectrum of the (one or more) light sources 102. The transmission spectrum of the (one or more) light sources 102 may include one or more spectral segments. These spectral segments may be continuous or discrete. Each spectral segment may include a peak and two slopes, one slope on each side of the peak. The first slope may be an upward slope on the first side of the peak, so that the intensity of the optical signal may increase with increasing wavelength. The second slope may be a downward slope on the second side opposite to the first side of the peak, so that the intensity of the optical signal may decrease with increasing wavelength. The peak may be a point on the spectral segment. Additionally or alternatively, the peak may be an aggregation of two of more continuous points that are continuous with each other to form a plateau of the spectral segment. In some variations, the first upward slope and the second downward slope may define the boundaries of the spectral segment on two opposite sides of the spectral segment. In some variations, the upward slope and the downward slope of the spectral segment may be symmetrical around the peak. In some variations, the upward slope and the downward slope may be asymmetrical around the peak.

[0065] Figure 2A A light source having a single spectral segment 240a is shown (e.g. Figure 1 232 of the light source 102). Figure 2A As seen in FIG. 1 , the transmission spectrum of the light source includes only one spectral segment 240a. The spectral segment 240a may include a peak 240a'" and an upward slope 240a' on a first side of the peak 240a'" and a downward slope 240a'" on a second side opposite to the first side of the peak 240a'" As discussed above, the peak 240a'" may be a point on the spectral segment 240a, or may be an aggregation of two or more consecutive points that are continuous with each other to form a plateau portion of the spectral segment 240a. In some variations, the slopes 240a' and 240a'" may define the boundaries of the spectral segment 240a on two opposite sides of the peak 240a'"

[0066] Figure 2B A light source having multiple spectral segments is shown (e.g. Figure 1 102 in FIG. 10A . In some embodiments, the intensity of the optical signal from the light source may be zero between two adjacent spectral segments. Additionally or alternatively, the intensity of the optical signal from the light source may not be 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 transmission spectrum 234 of the light source into a plurality of spectral segments. As a non-limiting example, Figure 2B The transmission spectrum 234 of the light source in includes three spectral segments 240b, 240c, and 240d. Each spectral segment includes a peak and two slopes on each side of the peak (e.g., one upward slope and one downward slope). For example, spectral segment 240b includes a peak 240b'' and an upward slope 240b' and a downward slope 240b' on opposite sides of the peak 240b''. Similarly, spectral segment 240c includes a peak 240c'' and an upward slope 240c' and a downward slope 240c' on opposite sides of the peak 240c''. In a similar manner, the spectral segment 240d includes a peak 240d'" and an upward slope 240d' and a downward slope 240'" on opposite sides of the peak 240d'" As discussed above, the peaks 240b'", 240c'" and 240d'" may be discrete points on the spectral segments 240b, 240c and 240d, respectively. Alternatively, the peaks 240b'", 240c'" and 240d'" may be aggregations of two or more consecutive points that are continuous with each other to form the plateau portions of the spectral segments 240b, 240c and 240d, respectively.

[0067] Figure 2C An exemplary variation of a transmission spectrum 236 having multiple spectral segments is shown. As discussed above, the optical signal intensity between two adjacent spectral segments may be zero or non-zero. For example, Figure 2C , spectral segments 240e and 240f may be continuous spectral segments or may be non-continuous spectral segments. For example, the miniaturized FBG interrogation system 100 may include more than one light source (e.g., Figure 1 102 in the light source). For example, the system 100 may include a first light source having a transmission spectrum 240e and a second light source having a transmission spectrum 240f. The combined transmission spectrum of the two light sources may be the transmission spectrum 236. As a non-limiting example, Figure 2CThe transmission spectrum 236 of the light source in includes two spectral segments 240e and 240f. Each spectral segment includes a peak and an upward slope and a downward slope on each side of the peak of the spectral segment. For example, spectral segment 240e includes a peak 240e'" and an upward slope 240e' and a downward slope 240e'" on opposite sides of the peak 240e'" of the spectral segment 240e. Similarly, spectral segment 240f includes a peak 240f'" and an upward slope 240f' and a downward slope 240f'" on opposite sides of the peak 240f'" of the spectral segment 240f. As discussed above, the peaks 240e'" and 240f'" can be discrete points on the spectral segments 240e and 240f, respectively. Alternatively, the peaks 240e'" and 240f'" can be aggregations of two or more continuous points that are continuous with each other to form plateaus of the spectral segments 240e and 240f, respectively.

[0068] Return to reference Figure 1 , the transmission spectrum of the light source(s) 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 in ).

[0069] In some variations, the FBG interrogation system 100 may include a single light source 102. In other variations, the FBG interrogation system 100 may include more than one light source 102. The (one or more) light sources 102 may be configured for integration into a small size device such as an implantable medical device. For example, the (one or more) light sources 102 described herein may have a small volume. Additionally or alternatively, the (one or more) light sources described herein may be small in size. For example, the (one or more) light sources 102 may have a small diameter and / or a small length.

[0070] In some variations, the (one or more) light sources 102 may be laser diodes. For example, the (one or more) light sources 102 may be semiconductor laser diodes (e.g., vertical cavity surface emitting lasers or VCSELs, edge emitting lasers). In some variations, the (one or more) light sources 102 may be doped light emitting diodes (LEDs). The LEDs may be configured to interact with the FBG sensors 106 in a distinct spectral domain (described in detail below) by customizing the dopants in the LEDs. Some example dopants may include arsenic, phosphorus, germanium, indium, etc. In some variations, the (one or more) light sources 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 (one or more) FBG sensors 106 in a distinct spectral domain by coating the light source with (one or more) wavelength conversion materials. Some example wavelength conversion materials may include phosphors, etc. In some variations, the (one or more) light sources 102 may be laser diodes (such as distributed feedback diodes, distributed Bragg reflector diodes, etc.). In some variations, the (one or more) light sources 102 may be electrically driven quantum dots.

[0071] FBG Sensor

[0072] The light source(s) 102 may be optically coupled to the FBG sensor(s) 106. The FBG sensor(s) 106 may be formed within an optical fiber. For example, the core of the optical fiber may be exposed to ultraviolet light to write grating planes and introduce periodic variations in the refractive index of the core. The distance or spacing between two adjacent grating planes may define the grating period.

[0073] When light is transmitted to the FBG sensor(s) 106, the FBG sensor(s) 106 reflects light of a specific wavelength within the reflection spectrum of the FBG sensor(s) 106. Changes in the physical signal sensed by the FBG sensor(s) 106 may cause changes in the grating period of the FBG sensor(s) 106. This in turn may result in a shift in the wavelength of the reflected light, thereby resulting in a shift in the reflection spectrum.

[0074] Similar to the transmission spectrum of the light source(s) 102, the reflection spectrum of the FBG sensor(s) 106 may include one or more spectral segments. For example, the reflection spectrum may include: Figure 3AA single reflectance spectrum segment is shown. Spectral segment 340a may include a peak 340a'" and two slopes 340a' and 340a", with peak 340a'" corresponding to the central Bragg wavelength where the reflectance may be at its maximum, and one slope on each side of peak 340a'". The first slope 340a' may be an upward slope on a first side whose reflectivity increases with increasing wavelength, and the second slope 340" may be a downward slope on a second side of the peak (e.g., opposite the first side) whose reflectivity decreases with increasing wavelength. In some embodiments, the upward slope and the downward slope may be symmetrical around the peak. In some embodiments, the upward slope and the downward slope may be asymmetrical around the peak. The peak of a reflectance spectrum segment may be a point. Alternatively, the peak may be an aggregation of two of more consecutive points that are continuous with each other to form a plateau of the reflectance spectrum segment. In some embodiments, such a plateau may be non-smooth or irregular. For example, a reflectance spectrum of a chirped FBG sensor may include a peak with an irregular plateau. In some embodiments, the reflectance spectrum may include a peak having an irregular plateau. Figure 3B . As a non-limiting example, the reflectance spectrum 343 of (one or more) FBG sensors 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 slope on each side of the peak. Each peak 340b'", 340c' or 340d'" of the corresponding reflectance spectrum segment 340b, 340c or 340d may be a point. Alternatively, each of the peaks may be an aggregation of two or more consecutive points that are continuous with each other to form a plateau of the corresponding reflectance spectrum segment. Similar to the Figure 2C The spectral segments in the transmission spectrum of the light source depicted in FIG. 1 and the reflection spectral segments in the reflection spectrum of the FBG sensor may be continuous spectral segments or may be non-continuous spectral segments.

[0075] Return to reference Figure 1In some variations, the FBG sensor(s) 106 of the FBG interrogation system 100 may be designed to optimize the width of the upward slope and / or downward slope of the reflectance spectrum fragment within the operating range of the FBG sensor(s) 106. The operating range may be determined based on the range of possible values ​​of the physical signal that the FBG sensor(s) 106 are configured to sense. For example, the operating range may be determined by determining the upper bound / maximum and lower bound / minimum of the physical signal that the FBG sensor(s) 106 are configured to sense. The response of the FBG sensor(s) 106 to the upper bound / maximum and lower bound / minimum may determine the operating range of the FBG sensor(s) 106.

[0076] The FBG sensor(s) 106 may be designed such that the reflectance spectrum of the FBG sensor(s) 106 may be conformed to optimize the upward-sloping and / or downward-sloping gradient of the reflectance spectrum segments within the operating range of the FBG sensor(s) 106. By adapting the reflectance spectrum of the FBG sensor(s) 106, the reflectance spectrum of the FBG sensor(s) 106 and the transmission spectrum of the light source(s) 102 may be configured to interact with each other such that the FBG interrogation system 100 may be sufficiently sensitive to changes in the sensed physical signal within its range of values.

[0077] In particular, the FBG sensor(s) 106 may be designed such that the width / gradient of a distinct spectral domain in the reflectance spectrum of the FBG sensor(s) 106 (described in detail below) may be modified to increase the sensitivity of the FBG interrogation system 100. More specifically, the gratings on the FBG sensor(s) 106 may be arranged in a manner to modify the distinct spectral domain as described herein. That is, the gratings may be formed or written on the optical fiber (e.g., with a laser) to modify the distinct spectral domain, such as by increasing the number of gratings for certain wavelengths on the FBG sensor(s) 106 in a particular manner and decreasing the number of gratings for certain other wavelengths on the FBG sensor(s) 106 and / or by increasing the spacing between gratings on the FBG sensor(s) 106 in a particular manner and decreasing the spacing between gratings. This is described in further detail below.

[0078] In some variations, the sensitivity of the FBG interrogation system 100 may be further increased by designing a distinct spectral domain in the transmission spectrum fragment of the (one or more) light sources 102 (described in detail below) and another distinct spectral domain in the reflection spectrum of the FBG sensor (one or more) 106 (described in detail below) so that the distinct spectral domain of the transmission spectrum fragment of the (one or more) light sources 102 interacts with the distinct spectral domain of the reflection spectrum of the (one or more) FBG sensor 106 over the operating range of the FBG sensor 106 in response to changes in the physical signal sensed by the (one or more) FBG sensor 106. This Figure 6C and explained in further detail below.

[0079] In some variations, the FBG sensor(s) 106 may be chirped FBG sensors. The chirped FBG sensor may be formed to have a gradually varying periodicity in the Bragg grating. This gradually varying periodicity (e.g., grating period) may produce a wide reflection spectrum. The chirped FBG sensor may be designed to increase the width of the distinct spectral domain in the reflection spectrum of the FBG sensor(s) 106.

[0080] The FBG sensor(s) 106 may be configured for integration into small size devices. For example, the FBG sensor(s) 106 may have a small diameter and / or a small length. For example, the diameter of the FBG sensor(s) 106 may 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(s) 106 may 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.

[0081] The FBG interrogation system 100 may include one or more FBG sensors 106. In variations with 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 variations with 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 two or more gratings in combination may form a separate FBG sensor 106). In some variations, the FBG interrogation system 100 may include multiple optical fibers. Each optical fiber may be designed to include a single or multiple FBG sensors 106. More than one FBG sensor 106 may allow multi-position and / or multi-point sensing. For example, the FBG interrogation system 100 (e.g., a miniaturized FBG interrogation 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 of a heart chamber (e.g., right atrium, right ventricle, coronary sinus, left ventricle, etc.) and / or more than one location at each of the different locations of a heart chamber (e.g., different locations in the coronary sinus) can allow the FBG interrogation system 100 to detect asynchrony between different locations and / or locations of the heart (e.g., synergy and / or lack of synchronization between locations or locations of the heart). In addition, detecting asynchrony can help effectively detect ventricular tachycardia and associated hemodynamic states. If two or more FBG sensors are on a single optical fiber, the photodetector 104 can apply wavelength division multiplexing to acquire and measure a response from each FBG sensor to a change in one or more sensed physical signals, as further described below. For example, a first FBG sensor can be positioned in the right ventricle and a second FBG sensor can be positioned in the coronary sinus (e.g., when the miniaturized FBG interrogation 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.

[0082] Photodetector

[0083] One or more photodetectors 104 may be optically coupled to (one or more) FBG sensors 106. (One or more) photodetectors 104 may be configured to measure changes in a physical signal sensed by (one or more) FBG sensors 106. For example, (one or more) FBG sensors 106 may receive an optical signal transmitted from a light source 102. In response to sensing a change in the physical signal, (one or more) FBG sensors 106 may generate a reflected light signal by interaction between one or more transmission spectra of (one or more) light sources and one or more reflection spectra of (one or more) FBG sensors in a distinguishing spectral domain, as further described below. The power of the reflected light signal may indicate a quantitative change in the physical signal. (One or more) photodetectors 104 may convert the reflected light signal into an electrical signal. The measurement of the electrical signal may indicate a change in the physical signal. For example, (one or more) photodetectors 104 may receive a reflected light signal from (one or more) FBG sensors 106, and may convert photons in the reflected light into an electric current. The measurement of the electric current may indicate a change in the sensed physical signal. (One or more) photodetectors 104 may be any suitable photodetector. For example, the photodetector(s) 104 may be semiconductor-based photodetectors (such as photodiodes, phototransistors, etc.). In some variations, the current may be converted into a voltage. The measurement of the voltage may indicate a change in the sensed physical signal sensed by the FBG sensor(s) 106.

[0084] In some variations, the miniaturized interrogation system 100 may include more than one photodetector 104. Each photodetector 104 may be coupled to a corresponding FBG sensor(s) 106. The FBG sensor(s) 106 may be positioned at different locations on a single optical fiber. Wavelength division multiplexing (WDM) may be applied to couple the photodetector(s) 104 to the FBG sensor(s) 106 so that the photodetector(s) 104 may receive a reflection spectrum from each of the FBG sensors 106 on a single optical fiber in response to changes in the physical signal(s) sensed by the FBG sensors 106 at their respective locations.

[0085] Power Management Unit

[0086] The light source(s) 102 and / or the photodetector(s) 104 may be electrically coupled to a power management unit (PMU) 109. In some variations, one or more powered components of the FBG interrogation system 100 (such as, for example, a pre-amplification component associated with the photodetector(s) 104, an amplification component associated with the photodetector(s) 104, an analog-to-digital conversion component associated with the photodetector(s) 104, a filtering circuit associated with the photodetector(s) 104, etc.) may be electrically coupled to the PMU 109. The term “powered component” may collectively refer to electrically powered components of the FBG interrogation system 100 other than the light source(s) 102, such as, but not limited to, a pre-amplification component associated with the photodetector(s) 104, an amplification component associated with the photodetector(s) 104, an analog-to-digital conversion component associated with the photodetector(s) 104, a filtering circuit associated with the photodetector(s) 104, etc.

[0087] In some variations, the PMU 109 may be configured to enable continuous operation of the FBG interrogation system 100. In some variations, the PMU 109 may be configured to minimize and / or optimize the power consumption of the FBG interrogation system 100. More specifically, the PMU 109 may be configured to switch the FBG interrogation system 100 from an operational state to a sleep state in order to minimize and / or reduce power consumption. For example, in some variations, when the (one or more) light sources 102 are turned on, the FBG interrogation system 100 may be in an operational state. In the operational state, the FBG interrogation system 100 may be configured to acquire and measure one or more physical signals (e.g., sensed physical signals) that the (one or more) FBG sensors 106 are configured to sense. When the (one or more) light sources 102 are turned off, the FBG interrogation system 100 may not measure the physical signals that the FBG sensors 106 are configured to sense, and may be in a sleep state, thereby saving power. In some variations, the (one or more) light sources 102 and / or powered components can be intermittently powered on and off via the PMU 109, thereby transitioning the FBG interrogation system 100 from an operating state to a sleep state, and vice versa, in order to minimize and / or reduce power consumption. In some variations, the amount of power (e.g., electrical power) supplied to the (one or more) light sources and / or powered components can be adjusted (e.g., adaptively adjusted) via the PMU 109 to achieve an optimal balance between the power consumed by the FBG interrogation system 100 and the sensitivity and / or accuracy with which the FBG interrogation system 100 senses physical signals.

[0088] In some variations, the FBG interrogation system 100 described herein may be configured to operate in one or more modes (referred to as "power-managed modes") that minimize power consumption. In some variations, the light source(s) 102 and / or powered components may be turned on via the PMU 109 based on the power-management mode of the FBG interrogation system 100, as further described herein.

[0089] In some variations, the PMU 109 may include one or more switches (such as ultrafast switches), and one or more power conditioning circuits, which may be coupled to the (one or more) light sources 102, and optionally to powered components. In some variations, the (one or more) light sources 102 and / or powered components may be powered for a determined period of time (e.g., an operating period) before being powered off via the one or more switches in a power management-based mode. For example, the miniaturized FBG interrogation system may be integrated into an implantable medical device (e.g., an ICD). The miniaturized FBG interrogation system 100 integrated into an ICD may have an operating period of about or less than about a fraction of a microsecond, about or less than about 10 microseconds, about or less than about 100 microseconds, about or less than about 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 less than 10 minutes, about or less than a fraction of an hour, or about or less than 30 hours. Based on the mode of power management, the light source(s) and / or powered components may be powered via one or more switches during an operating period and may be turned off via one or more switches after the duration of the operating period.

[0090] In some variations, the PMU 109 may include one or more power regulating circuits to regulate the amount of electrical power delivered to the (one or more) light sources 102 and / or powered components. For example, the miniaturized FBG interrogation system 100 may be integrated into an implantable medical device (e.g., an ICD) for a heart to sense myocardial strain of (one or more) ventricles. The amount of electrical power delivered to the light source 102 may be reduced via the power regulating circuit so that the intensity of the transmission spectrum / multiple transmission spectra of the (one or more) light sources 102 may be reduced while the one or more myocardial strain signals of the ventricles are adequately sensed by the miniaturized FBG interrogation system 100 to accurately determine the hemodynamic stability of the subject with minimal power consumption. In a similar manner, in some variations, the amount of electrical power delivered to the powered components may be reduced via the power regulating circuit so that the gain and / or sampling frequency of the FBG interrogation system 100 may be reduced while the one or more myocardial strain signals of the ventricles are more adequately sensed by the miniaturized FBG interrogation system 100 to accurately determine the hemodynamic stability of the subject with minimal power consumption.

[0091] It should be understood that the physical arrangement or order between the switch(es) and the power conditioning circuit may vary. In some variations, the switch may be disposed before the power conditioning circuit for one light source or for one powered component. In some variations, the power conditioning circuit may be disposed before the switch for another light source or for another powered component.

[0092] In some variations, the PMU 109 may include one or more processors to control at least some components of the PMU 109 (e.g., switches, power regulation circuits, etc.). In some variations, the PMU 109 may be coupled to one or more processors (e.g., Figure 1 100) to control at least some components of the PMU 109 (e.g., switches, power regulation circuits, etc.). In some variations, the (one or more) processors may automatically control one or more components of the PMU 109. For example, the (one or more) processors may control one or more components of the PMU 109 based on a preprogrammed algorithm. Additionally or alternatively, the (one or more) processors may control one or more components of the PMU 109 based on machine learning techniques. In variations in which the FBG interrogation system 100 is integrated into an implantable medical device, the (one or more) processors may control one or more components of the PMU 109 based on historical data and / or real-time data collected by the implantable medical device. In some variations, a user may wirelessly control one or more components of the PMU 109 via the processor.

[0093] The FBG interrogation system 100 can be configured to operate in at least five power management modes via the PMU 109 in order to minimize power consumption. For example, the FBG interrogation system 100 can be configured to operate in a continuous mode, an event-triggered mode, an event-gated mode, a pulse width modulation mode (pulse mode), and / or an adaptive power mode via the PMU 109, as further described herein. In the continuous mode, (one or more) light sources 102 and / or powered components can be turned on continuously. It should be understood that the terms continuous and continuously as used herein to describe the continuous mode of power management do not explicitly or implicitly indicate that the FBG interrogation system is powered on or turned on without interruption. In some variations, such interruptions may occur when the continuous mode is combined with other modes (such as event-gated mode and / or pulse mode), as described below.

[0094] In the event-triggered mode, the light source(s) 102 and / or powered components may be turned on (e.g., automatically) by a triggering event, including, but not limited to, (1) a physical event as described herein, (2) a preprogrammed interval, and / or (3) a request from a user. For example, the miniaturized FBG interrogation system 100 may be integrated into an ICD, as described herein. In some variations, the light source(s) 102 and / or powered components may be turned on (e.g., automatically) by a triggering event, such as a physical event including a demand event(s), such as tachycardia, heart failure, ischemia, etc. In some variations, the light source(s) 102 and / or powered components may be turned on (e.g., automatically) at preprogrammed interrogation intervals. Such preprogrammed interrogation intervals may be daily, weekly, monthly, quarterly, or yearly, or fractions thereof. In some variations, the light source(s) 102 and / or powered components may be turned on (e.g., automatically) by a triggering event, such as a request from a user. Such a user may be a physician, nurse practitioner, physician assistant, medical technician, etc., who has the training and professional qualifications to perform such a request. For example, a user may send a request to the FBG interrogation system 100 via a wireless interface or other type of I / O device to turn on the light source(s) 102 and / or powered components.

[0095] In some variations, (one or more) light sources 102 and / or powered components may remain powered for a period of time (e.g., an operating period) before being automatically turned off or powered off. During the operating period, the miniaturized FBG interrogation system 100 may acquire and measure one or more physical signals (e.g., sensed physical signals) that (one or more) FBG sensors 106 are configured to sense. In some instances, the length or duration of the operating period may be fixed or predetermined. In some variations, the length of the operating 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 interrogation system 100) and the amount of power consumed by the FBG interrogation system 100. In some instances, the length or duration of the operating period may be dynamically determined based at least in part on an analysis of physical signals sensed by (one or more) FBG sensors by the FBG interrogation system 100 during the current operating period and / or during the previous operating period. In some variations, the length of the operating period may be dynamically determined based at least in part on analysis of physical signals detectable by non-FBG sensor(s), such as electrocardiograms detected by electrodes disposed in the heart and / or by separate and additional FBG sensors. For example, the duration of the operating period may be the entire duration of the arrhythmia, ischemia, or heart failure exacerbation, or a fraction thereof or exceeding such duration.

[0096] In some variations, some physical events may occur at recurring intervals (e.g., cardiac cycles, respiratory cycles, etc.). Such recurring physical events may have a periodicity that may vary over time. For example, the cardiac cycle and the respiratory cycle are recurring events whose periodicity is generally stable. However, there may be times when the periodicity of the cardiac cycle and the respiratory cycle varies. In variations in which the FBG interrogation system 100 is integrated into an implantable medical device, recurring physical events that occur at recurring intervals may be detected by the implantable medical device, as further described herein. As a non-limiting example, the cardiac cycle as a recurring event may be detected by analyzing the cardiac electrogram signal through the electrodes in the implantable medical device. As yet another non-limiting example, the respiratory cycle as a recurring event may be detected by analyzing the transthoracic impedance via an impedance sensor in the implantable medical device.

[0097] In response to a recurring physical event, the FBG interrogation system 100 can be configured to operate in an event-gated mode via the PMU 109. In the event-gated mode, a processor (e.g., a processor within the PMU 109 and / or a processor coupled to the PMU 109) can actuate (one or more) switches (e.g., (one or more) ultra-fast switches) in the PMU 109 so that (one or more) light sources 102 and / or powered components can be quickly turned on and off at (one or more) specific moments and / or (one or more) time points (i.e., (one or more) gating time points) during (one or more) recurring cycles of (one or more) recurring events. These gating time points can be predetermined. Additionally or alternatively, these gating time points can be dynamically determined, for example, before, at, or after the recurring physical event occurs. For example, (one or more) light sources 102 can be turned on (e.g., automatically turned on) at specific gating time points (e.g., predetermined and / or dynamically determined) during (one or more) recurring events. After a certain period of time (e.g., an operating period) from turning on (one or more) light sources 102 and / or (one or more) powered components, the (one or more) light sources and / or (one or more) powered components may be turned off (e.g., automatically turned off). During the operating period when (one or more) light sources 102 are turned on, the FBG interrogation 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. As discussed above and similar to the event-triggered mode, for the event-gated mode, the length of the operating period from turning on (one or more) light sources to turning off (one or more) light sources 102 may be hours or fractions of hours, minutes or fractions of minutes, seconds or fractions of seconds, milliseconds or fractions of milliseconds, microseconds or fractions of microseconds, etc. In some variations, the length of the operating period of the event-gated mode may be fixed or predetermined. In some variations, the length of the operation period of the event-gated mode 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 interrogation system 100) and the amount of power consumed by the FBG interrogation system 100. In some variations, the length of the operation period of the event-triggered mode and / or event-gated mode may be dynamically determined based at least in part on an analysis of sensed physical signals sensed by the FBG interrogation system 100 via FBG sensors during a current operation period and / or that have been recorded during a previous operation period. In some variations, the length of the operation period of the event-triggered mode and / or event-gated mode may be dynamically determined based at least in part on an analysis of physical signals that may be detected by (one or more) non-FBG sensors and / or by separate and additional FBG sensors.In some variations, the length of the operating period of the event-triggered mode and / or the event-gated mode may be dynamically determined based at least in part on analysis of changes in recurring physical events in the time or frequency domain that may be detected by FBG interrogation system 100 .

[0098] In some variations, (one or more) recurring events may, for example, recur at (one or more) recurring intervals. In some variations, the operating period of the event trigger mode may not exceed the recurrence interval of the recurring event. For example, (one or more) light sources 102 and / or powered components may be turned on (e.g., automatically turned on) at the end of systole of the cardiac cycle and may be disconnected (e.g., automatically disconnected) after a preset operating period of 50 or 100 milliseconds. In a similar manner, (one or more) light sources 102 and / or powered components may be turned on (e.g., automatically turned on) at the end of diastole of the cardiac cycle and may be disconnected (e.g., automatically disconnected) after a preset operating period of 50 or 100 milliseconds. In some variations, the operating period of the event trigger mode may exceed the recurrence interval of the recurring event. In some variations, the (one or more) light sources 102 and / or powered components may be turned on (e.g., automatically) at the end of inspiration of the respiratory cycle and may be turned off after a dynamically determined operating period, for example, an operating period dynamically determined to be equal to 2 or 3 cardiac cycles based on analysis of motion measurements of portions of the heart (such as motion of the (one or more) ventricular walls sensed by the FBG interrogation system 100 through the FBG sensors) and / or based on analysis of cardiac electrogram signals through electrodes (non-FBG sensors). In a similar manner, the (one or more) light sources 102 may be turned on (e.g., automatically) at the end of expiration of the respiratory cycle and may be turned off (e.g., automatically) after a dynamically determined operating period, for example, an operating period dynamically determined to be equal to 2 or 3 cardiac cycles based on analysis of motion measurements of portions of the heart (such as motion of the (one or more) ventricular walls sensed by the FBG interrogation system 100 through the FBG sensors) and / or based on analysis of cardiac electrogram signals through electrodes (non-FBG sensors).

[0099] In some variations, the FBG interrogation system 100 can be configured to operate in a pulse width modulation mode or a pulse mode via the PMU 109. In the pulse mode, the power delivered to the (one or more) light sources 102 and / or powered components can be in the form of discrete pulses. These discrete pulses can turn on and / or off the (one or more) light sources 102 and / or powered components in a discrete manner. The discrete manner in which the (one or more) light sources 102 and / or powered components can be turned on and off can be based on the duty cycle and / or (one or more) voltage / current signals of the clock that controls the power delivered to the (one or more) light sources 102 and / or powered components. For example, the power delivered to the (one or more) light sources 102 and / or powered components can be expressed in the form of a duty cycle, which can indicate the ratio of the time that the (one or more) light sources 102 and / or powered components can be turned on to the time that the (one or more) light sources 102 can be turned off. Fig. 9 An example duty cycle of power delivered to (one or more) light sources 102 and / or powered components when the FBG interrogation system 100 is operated in a pulse width modulation mode of power management is shown. For example, duty cycle 992 has a pulse time interval of 50%. In other words, the power delivered to (one or more) light sources 102 and / or powered components can turn on (one or more) light sources 102 and / or powered components 50% of the time and turn off (one or more) light sources 102 and / or powered components 50% of the time. Similarly, duty cycle 994 has a pulse time interval of 75%, so that the power delivered to (one or more) light sources 102 and / or powered components turns on (one or more) light sources 102 and / or powered components 75% of the time and turns off (one or more) light sources 102 and / or powered components 25% of the time. In a similar manner, the duty cycle 996 has a 25% pulse time interval, so that the power delivered to the (one or more) light sources 102 and / or powered components turns on the (one or more) light sources 102 and / or powered components for 25% of the time, and turns off the (one or more) light sources 102 and / or associated powered components for 75% of the time. In some variations, the duty cycle can be pre-programmed, or alternatively, dynamically determined based on an 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 appreciated that the amplitude of the physical signal sensed by the FBG sensor 106 and the output amplitude of the photodetector 104 are highly correlated to each other.

[0100] In some variations, the discrete form of the pulsed power delivered to the light source 102 and / or powered components may be a rectangular morphology. In some variations, the discrete form of the pulsed power delivered to the light source 102 and / or powered components may be modulated to other non-rectangular morphologies (such as sinusoidal or near-sinusoidal). In some variations, the morphology of the pulsed power, the frequency of the pulses, and the percentage of duty cycle may be optimized to minimize power consumption while allowing adequate acquisition of the (one or more) physical signals and reducing or eliminating (one or more) low-frequency artifacts that may be introduced in the output signal of the miniaturized FBG interrogation system 100, which may overlap with (one or more) frequency components in the (one or more) physical signals sensed by the (one or more) FBG sensors.

[0101] In some variations, the FBG interrogation system 100 may be configured to operate in an adaptive power mode via the PMU 109. In the adaptive power mode, the power delivered to the optical source(s) 102 and / or powered components may 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(s) 106. For example, if it is determined that the amplitude of the physical signal sensed by the FBG sensor(s) 106 is greater than a detection threshold, the power delivered to the optical source(s) 102 and / or powered components may be adaptively reduced via one or more power regulation circuits included in the PMU 109. The detection threshold may 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(s) 106. Thus, when the amplitude of the physical signal sensed by (one or more) FBG sensors 106 is greater than the detection threshold, adaptively reducing the power transmitted to (one or more) light sources 102 and / or (one or more) powered components can minimize and / or reduce the power consumed by the FBG interrogation system 100.

[0102] In a similar manner, if it is determined that the amplitude of the physical signal sensed by the FBG sensor(s) 106 is below a sensitivity threshold, the power transmitted to the light source(s) 102 and / or the powered component(s) may be adaptively increased via one or more power regulation circuits included in the PMU 109. The sensitivity threshold may 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 the FBG sensor(s) 106. Thus, when the amplitude of the physical signal sensed by the FBG sensor(s) 106 is less than the sensitivity threshold, adaptively increasing the power transmitted to the light source(s) 102 and / or the powered component(s) may increase the accuracy and sensitivity of the FBG interrogation system 100.

[0103] In some variations, the detection threshold of the (one or more) light sources may be the same as the detection threshold of the (one or more) powered components. In some variations, the detection threshold of the (one or more) light sources may be different from the detection threshold of the (one or more) powered components. In some variations, the sensitivity threshold of the (one or more) light sources may be the same as the sensitivity threshold of the (one or more) powered components. In some variations, the sensitivity threshold of the (one or more) light sources may be different from the sensitivity threshold of the (one or more) powered components. In some variations, the detection threshold may be the same as the sensitivity threshold. In some variations, the detection threshold may be different from the sensitivity threshold.

[0104] In some variations, the amount of power delivered to the light source(s) 102 and / or powered component(s), alone or in any combination thereof, may be adaptively adjusted based on an 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, such adaptive adjustment of power may be in the form of adaptively adjusting (e.g., increasing or decreasing) the current, voltage, and / or duty cycle of a clock and / or voltage / current signal that controls the power delivered to the light source(s) 102 and / or powered component(s), as described above.

[0105] 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 determined dynamically (e.g., based on historical and / or real-time data from the FBG interrogation system 100). In some variations, the detection threshold and / or sensitivity threshold may be determined based on input and / or feedback from a user. In some variations, the adaptive adjustment of the power of (one or more) light sources 102 and / or (one or more) powered components may be in the form of an adjustment of the current and / or voltage of (one or more) light sources 102 and / or (one or more) powered components. In some variations, the adaptive adjustment of power may be the same between (one or more) light sources 102 and / or powered components. In some variations, the adaptive adjustment of power may be different between (one or more) light sources 102 and / or powered components. As an example, the miniaturized FBG interrogation system 100 may be integrated into an implantable medical device to sense ventricular myocardial strain, thereby determining hemodynamic status during events such as arrhythmias, heart failure, and / or ischemia. In some variations, the baseline magnitude of myocardial strain (e.g., as determined during normal heart rate and / or baseline conditions) may vary from subject to subject, as well as from moment to moment in the same subject, depending on a number of factors, including, but not limited to, left ventricular ejection fraction, adequacy of coronary blood supply, metabolic state, ventricular preload and / or afterload, etc. If the baseline magnitude of myocardial strain is reliably and excessively greater than a detection threshold, one or more power regulation circuits in the PMU 109 may adaptively reduce the amount of electrical power to the (one or more) light sources 102 and / or (one or more) powered components to minimize power consumption. Conversely, if it can be determined that the baseline magnitude of myocardial strain sensed by the (one or more) FBG sensor 106 is below a sensitivity threshold, one or more power regulation circuits in the PMU 109 may adaptively increase the amount of electrical power to the (one or more) light sources 102 and / or (one or more) powered components to improve the sensitivity and accuracy of the FBG interrogation system 100.

[0106] In some variations, the various power management modes described herein for minimizing or optimizing power consumption may be performed separately and / or simultaneously with one or more other modes as further described herein. However, in some variations, the continuous mode and the event-triggered mode may be formed sequentially rather than simultaneously. The power management unit and power management modes described herein in the context of a miniaturized FBG interrogation system may be independent of the specific system, device, and / or method for miniaturizing the FBG interrogator. In some cases, the power management unit (PMU) and associated power management modes described herein may adjust the power consumption of the light source and other powered components rather than directly adjusting the power consumption of the optical sensor itself. In these instances, the PMU and the power management modes described herein may be used to minimize and optimize the power consumption of other sensing systems or devices that employ other optical sensors.

[0107] Optional adjustable FBG

[0108] In some variations, the FBG interrogation system 100 may optionally include one or more regulating FBGs 110 to split the transmission spectrum of (one or more) light sources 102 into multiple spectral segments. The (one or more) regulating FBGs 110 may be formed on an optical fiber by writing segments having a periodically varying refractive index on the core of the optical fiber. However, unlike the FBG sensor 106, the regulating FBG 110 may be configured to split the transmission spectrum into multiple spectral segments. For example, when the transmission spectrum from (one or more) light sources 102 is transmitted to the (one or more) regulating FBGs 110, the (one or more) regulating FBGs 110 may generate notches in the transmission spectrum, thereby splitting the transmission spectrum into multiple spectral segments. The (one or more) regulating FBGs 110 may be optically coupled to the light source 102. If the transmission spectrum of the (one or more) light sources 102 has a value such as Figure 2A If the single spectral fragment is shown, the (one or more) adjustment FBG 110 can be optically coupled to the (one or more) light source 102 to split the single spectral fragment into Figure 2B In some variations, the tuning FBG(s) 110 may be used as a filter (eg, to optimize the width and / or slope of distinct spectral domains in a transmission spectrum or multiple transmission spectra of the light source(s) 102).

[0109] Optical Router

[0110] In some variations, the FBG interrogation system 100 may include one or more optical routers 108 to direct or relay optical signals between two or more components of the FBG interrogation system 100 and / or distribute optical signals from one component of the FBG interrogation system 100 to two or more components. For example, the optical router(s) 108 may optically couple the optical source(s) 102 and the photodetector 104 to the FBG sensor(s) 106. The optical router(s) 108 may be a single optical fiber including two separate optical fiber portions (e.g., a first optical fiber portion and a second optical fiber portion). The optical router(s) 108 may receive an optical signal through a single optical fiber, which may be split into two separate output optical signals (e.g., a first optical signal and a second optical signal) transmitted through two separate optical fiber portions. For example, the first optical fiber portion may optically couple the FBG sensor(s) 106 to the optical source(s) 102. The second optical fiber portion may optically couple the FBG sensor(s) 106 to the photodetector(s) 104. This may be advantageous in making the FBG interrogation system 100 compact and reducing the form factor of the FBG interrogation system 100. More specifically, in order to transmit the optical signal from the optical source(s) 102 to the FBG sensor(s) 106, an optical fiber may be required to optically couple the optical source(s) 102 and the FBG sensor(s) 106. Similarly, in order to receive the reflected optical signal from the FBG sensor(s) 106 at the photodetector 104, an optical fiber may be required to optically couple the photodetector(s) 104 and the FBG sensor(s) 106. Instead of using two separate optical fibers, which may contribute to making the FBG interrogation system 100 bulky, an optical router 108 having a single optical fiber may be used. As non-limiting examples, the optical router(s) 108 as described herein may include an optical coupler, an optical splitter, an optical circulator, or an optical switch.

[0111] Exemplary Variations of FBG Interrogation System Components

[0112] Distinguishing spectral domains

[0113] The FBG sensor(s) 106 and / or the light source(s) 102 may be designed such that the transmission spectrum of the light source(s) 102 and the reflection spectrum of the FBG sensor(s) 106 are configured to interact on a distinct spectral domain. The distinct spectral domain may be a region in the transmission spectrum of the light source(s) 102 and / or a region in the reflection spectrum of the FBG sensor(s) 106.

[0114] Figure 4Exemplary variations of distinguishing spectral domains 440a* and 440a** are shown. The distinguishing spectral domains may be regions 440a* and / or regions 440a** in spectral segment 440a. Spectral segment 440a may include a peak 440a'' and an upward slope 440a' and a downward slope 440a'' on each side of peak 440a''. The distinguishing spectral domain 440a* may be the region below the upward slope 440a'. For example, the distinguishing spectral domain 440a* may be a slanted portion of spectral segment 440a (e.g., the region below slope 440a'). Additionally or alternatively, the distinguishing spectral domain 440a** may be the region below the downward slope 440a". Spectral segment 440a may be a light source (e.g., Figure 1 spectral fragments of the transmission spectrum of the (one or more) light sources 102) and / or FBG sensors (e.g., Figure 1 Thus, the distinguishing spectral domains 440a* and 440a** may each be defined by a portion of the transmission spectrum of the light source and / or a portion of the reflection spectrum of the FBG sensor. Figure 4 It represents the relationship between the intensity and wavelength of a light source when the distinguishing spectral domain is defined by the transmission spectrum of the light source. In other words, Figure 4 The y-axis in represents the intensity of the light source when the distinguishing spectral domain is defined by the transmission spectrum of the light source. In a similar manner, when the distinguishing spectral domain is defined by the reflection spectrum of the FBG sensor, Figure 4 The y-axis in represents the relationship between the reflectivity of the FBG sensor and the wavelength. In other words, Figure 4 The y-axis in represents the reflectivity of the FBG sensor when the distinguishing spectral domain is defined by the reflectance spectrum of the FBG sensor.

[0115] In the distinguishing spectral domain (e.g., 440a* or 440a**), the power of the reflected light signal from the FBG sensor can vary monotonically (e.g., linearly) in response to a shift in the reflection spectrum of the FBG sensor. As discussed herein, the reflection spectrum of the FBG sensor can shift in response to a change in a physical signal sensed by the FBG sensor. The shift in the reflection spectrum of the FBG sensor can appear as a monotonic function of the change in the physical signal sensed by the FBG sensor within the operating range of the FBG sensor. Therefore, in the distinguishing spectral domain (e.g., 440a* or 440a**), the power of the reflected light signal can vary monotonically (e.g., linearly) in response to a change in the physical signal sensed by the FBG sensor. Therefore, when the distinguishing spectral domain (e.g., 440a* or 440a**) is wide enough to cover the entire operating range of the FBG sensor, it may be feasible to indirectly detect the reflection spectrum of the FBG sensor for a low measurement frequency physical signal that shifts on the distinguishing spectral domain (e.g., 440a* or 440a**). Thus, bulky Fabry-Perot interferometers currently used for physical signals with low measurement frequencies (e.g., <100 Hz) having a relatively large range of values ​​can be eliminated. In contrast, some variations of the FBG interrogation system 100 described herein can represent the simplest FBG interrogation system, having a minimal number of components, including a FBG sensor 106, at least one light source 102, and a photodetector.

[0116] As discussed above, in some variations, the distinguishing spectral domain 440a** can be defined by a downward slope 440" of the spectral segment 440a. The downward slope 440a" can represent a monotonically decreasing function. For example, the downward slope 440" can represent a function such that for a shift in wavelength, where can represent the power of the reflected light signal. Therefore, with the shift in the reflected spectrum (and the shift in wavelength), the power of the reflected light signal can change monotonically. Therefore, 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 illustrative purposes, Figure 4The upward slope 440a' and the downward slope 440a" in 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 may negatively impact the accuracy, resolution, or sensitivity of the miniaturized FBG interrogation system. In some embodiments, these small irregularities or ripples may be minimized by the manufacturing process of the light source and / or FBG sensor. Additionally or alternatively, the effects of these small irregularities or ripples may be minimized during operation of the miniaturized FBG interrogation system by applying a signal processing algorithm. In some embodiments, the gradient of the upward slope 440a' or the downward slope 440a" may be optimized to allow for increased sensitivity without compromising the width of the distinguishing spectral domain. This may make a miniaturized FBG interrogation system (e.g., FBG interrogation system 100) more sensitive to small changes in the physical signal, thereby increasing the sensitivity of the miniaturized FBG interrogation system 100.

[0117] The distinguishing spectral domain (e.g., 440a* or 440a**) can be at least wide enough to cover the operating range of the FBG sensor. More specifically, the minimum width of the distinguishing spectral domain can cause the power of the reflected light signal to vary monotonically over the entire operating range of the FBG sensor. If the width of the distinguishing spectral domain (e.g., 440a* or 440a**) is less than the minimum width, the FBG sensor and / or light source can be designed to extend the width of the distinguishing spectral domain, as further described below.

[0118] light source

[0119] In some variations, a light source (e.g., Figure 1 The (one or more) light sources 102 in the embodiment of the present invention can be designed so that a portion of the transmission spectrum of the light source can define a distinct spectral domain (e.g., 440a* or 440a**). For example, the distinct spectral domain (e.g., 440a* or 440a**) can be a region in the transmission spectrum of the light source. As an example, consider that the spectral segment 440a is in the transmission spectrum of the light source. Figure 4 The y-axis represents the intensity of the light source. In some variations, the distinguishing spectral domain 440* can be the area below the upward slope 440a'. Additionally or alternatively, the distinguishing spectral domain 440** can be the area below the downward slope 440a". In some variations, the spectral segment 440a can represent the entire transmission spectrum of the light source as described herein. In other variations, the spectral segment 440a can be a spectral segment in the transmission spectrum that includes multiple spectral segments (e.g., such as in Figure 2B and Figure 2CIn such a scenario, the transmission spectrum may include multiple distinct spectral domains. For example, any number of spectral segments of the transmission spectrum may include at least one distinct spectral domain. For example, if the transmission spectrum of the light source includes three spectral segments, one spectral segment, any two spectral segments, or all three spectral segments may each include at least one corresponding distinct spectral domain, such as Figure 4 The difference in spectral domain 440a* or 440a**.

[0120] In some embodiments, the light source may be designed so that the distinguishing spectral domain 440a** has at least a minimum width that can cover the operating range of the FBG sensor. For example, the LED light source may be designed so that the width of the downward slope 440a" in the transmission spectrum may be wide enough to cover the operating range of the FBG sensor. More specifically, the minimum width of the downward slope 440a" in the transmission spectrum may be determined based on the operating range of the FBG sensor. The light source may be designed so that the downward slope 440a" of the transmission spectrum has at least a minimum width.

[0121] In some embodiments, the width of the upward slope 440a' and / or the downward slope 440a" of the transmission spectrum segment of the light source 102 can be optimized. For example, the width and gradient of the upward slope 440a' and / or the downward slope 440a" of (one or more) transmission spectrum segments can be optimized during the manufacturing process of the light source ("pre-launch manufacturing"). Additionally or alternatively, the width and gradient of the upward slope 440a' and / or the downward slope 440a" of (one or more) transmission spectrum segments can be optimized after the light source has been manufactured ("post-launch modification").

[0122] In some variations, as a non-limiting example, the pre-emission manufacturing process can include changing the dopant of the light source (e.g., changing the doping concentration). For example, the doping concentration and / or dopant can be changed in the quantum well (such as the arsenic and / or phosphorus composition can be changed for an infrared emitter). In a similar manner, the indium doping composition can be changed according to a blue emitter and / or a green emitter. Changing the concentration or composition of the dopant can change the transmission spectrum of the light source. The concentration or composition can be changed so that the width and gradient of the upward slope 440a' and / or the downward slope 440a" of (one or more) transmission spectrum segments can be optimized.

[0123] 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 a phosphor and / or quantum dots). For example, the physical size and / or composition of the dye or pigment or wavelength conversion material may be changed. Changing the physical size and / or composition of the dye or pigment or wavelength conversion material may change the transmission spectrum of the light source. Thus, the light source may be coated with a dye or pigment or a wavelength conversion material such that the width and gradient of the upward slope 440a' and / or the downward slope 440a" of (one or more) transmission spectrum segments may be optimized. In some variations, the post-emission modification process may include modifying the transmission spectrum of the light source using one or more optical filters (such as adjusting the FBG) such that the width and gradient of the upward slope 440a' and / or the downward slope 440a" of (one or more) transmission spectrum segments may be optimized.

[0124] In some variations, the light source can be designed to include multiple light sources, each with a different transmission spectrum. These multiple light sources can be packaged together in a manner such that the combined transmission spectrum can include a distinct spectral domain (e.g., 440a* or 440a**) with a desired minimum width (e.g., a minimum width that can be determined as described above). As another example, the light source can be designed to include multiple LEDs, each with a different transmission spectrum. These multiple LEDs can be packaged together in a manner such that the combined transmission spectrum can include a distinct spectral domain (e.g., 440a* or 440a**) with a desired or desired minimum width.

[0125] Figure 5A 5. Light sources (eg, Figure 1 The transmission spectrum 540 of the light source(s) 102 and the FBG sensor (e.g., Figure 1 540 . For example, the transmission spectrum 540 of the light source and the reflection spectrum 550 of the FBG sensor can be made to interact with each other on a different spectral domain 540* in the transmission spectrum 540. Since the reflected light signal (e.g., Figure 5A The power of the reflected light signal (e.g., 552) varies monotonically in the distinguishing spectral domain 540*, and the distinguishing spectral domain has a minimum width covering the entire operating range of the FBG sensor, so the FBG interrogation system can be sensitive to changes in the physical signal within the operating range of the FBG sensor. The sensitivity of the FBG interrogation system can be increased by increasing the gradient of the downward slope 540" defining the distinguishing spectral domain 540*. The operating range of the FBG sensor can be increased by increasing the width of the distinguishing spectral domain 540*. In some variations, the reflected light signal (e.g., Figure 5AThe power of 552) in can be defined by the following formula: where L(wl) represents the intensity of the transmission spectrum 540 of the light source, and W(wl) represents the reflectivity of the reflection spectrum 550 of the FBG sensor at wavelength wl.

[0126] In some variations, the light source may be designed to interact with multiple reflectance spectra of a FBG sensor. For example, a FBG interrogation system may include multiple FBG sensors, each with a different central wavelength and corresponding operating range. The collective reflectance spectrum of the multiple FBG sensors may include multiple reflectance spectrum segments (e.g., such as Figure 3B In some embodiments, the light source can be designed so that a single transmission spectrum of the light source can be adjusted to interact with each reflection spectrum of the corresponding FBG sensor in a corresponding distinguishing spectral domain. For example, the light source can be designed so that a single transmission spectrum can be adjusted by adjusting the FBG (e.g., Figure 1 The FBG 110 in the adjustment is segmented so that each segmented spectral fragment can interact with each reflection spectrum of the corresponding FBG sensor on the corresponding distinguishing spectral domain. In other variations, the light source may include multiple light sources, each of which is designed to interact with each single reflection spectrum of the corresponding FBG sensor on the corresponding distinguishing spectral domain.

[0127] FBG Sensor

[0128] Return to reference Figure 4 In some embodiments, a FBG sensor (e.g., Figure 1 The FBG sensor(s) 106 in the embodiment may be designed such that a portion of the reflection spectrum of the FBG sensor may define a distinct spectral domain (eg, 440a* or 440a**). Figure 4 The y-axis of 440a may represent the reflectivity of the FBG sensor. For example, the distinct spectral domain (e.g., 440a* or 440a**) may be a region in the reflectance spectrum of the FBG sensor. As an example, consider spectral segment 440a in the reflectance spectrum of the FBG sensor. In some variations, spectral segment 440a may represent the entire reflectance spectrum of the FBG sensor (e.g., such as in Figure 3A In such a scenario, the reflection spectrum may include at least one distinct spectral domain (such as 440a* and / or 440a** described herein). In other variations, spectral segment 440a may be a spectral segment in a reflection spectrum that includes multiple spectral segments (e.g., such as Figure 3BIn this scenario, the reflection spectrum may include multiple distinct spectral domains. For example, each of the spectral segments of the reflection spectrum may include a corresponding distinct spectral domain 440a*, 440a**, or both.

[0129] In some embodiments, the FBG sensor may be designed such that a distinguishing spectral domain (e.g., 440a* or 440a**) has at least a minimum width that can cover the operating range of the FBG sensor. For example, the FBG sensor may be designed such that the width of the downward slope 440a" in the reflection spectrum may be wide enough to cover the operating range of the FBG sensor. More specifically, the minimum width of the downward slope 440a" in the reflection spectrum may be determined based on the operating range of the FBG sensor. The FBG sensor may be designed such that the downward slope 440a" of the reflection spectrum has at least a minimum width.

[0130] In some embodiments, the width of the distinct spectral domain (e.g., 440a* or 440a**) can be optimized by changing the grating period of the FBG sensor, changing the number of gratings of a given grating period of the FBG sensor, changing the pattern of distribution of gratings of different grating periods along the core of the optical fiber of the FBG sensor, changing the tilt or angle of the grating plane, changing the time of exposure to UV light during writing of the grating on the optical fiber, changing the chemical composition of the core of the optical fiber so as to change the refractive index, introducing a gradient in the refractive index of the core of the optical fiber (e.g., by changing the tilt or angle of the grating plane and / or changing the time of exposure to UV light), combinations thereof, and the like.

[0131] For example, the FBG sensor can be designed such that for a reflected light signal at a wavelength where a higher power is desired, the number of gratings can be increased, while for a reflected light signal at a wavelength where a lower power is desired, the number of gratings can be reduced. Figure 4, for reflected light signals at wavelengths closer to the peak 440a, the number of gratings of the FBG sensor can be increased. The power of the reflected light signal of the FBG sensor can be proportional to the number of gratings. Therefore, for reflected light signals at wavelengths closer to the peak 440a, a greater number of gratings can increase the power of the reflected light signals at these wavelengths. Conversely, the number of gratings of the FBG sensor can be reduced as the wavelength of the reflected light signal begins to move away from the peak 440a. For example, for reflected light signals at wavelengths farthest from the peak 440a, the number of gratings of the FBG sensor can be the least. A smaller number of gratings can reduce the power of these reflected light signals. This increased power closer to the peak 440a and decreased power away from the peak 440a can, in turn, increase the gradient of the downward slope 440a", thereby adjusting the sensitivity of the FBG interrogation system as desired. Additionally, this can increase the width of the slope (e.g., downward slope 440a"), thereby increasing the width of the distinction spectral domain (e.g., 440a**) so as to adapt the distinction spectral domain to the desired operating range of the FBG sensor, thereby enabling the FBG sensor to sense physical signals having a low measurement frequency but a larger range of values.

[0132] Additionally or alternatively, the FBG sensor can be designed such that the grating period (e.g., the spacing between the gratings) can be changed so that the distinguishing spectral domain (e.g., 440a* or 440a**) has at least a minimum width. For example, the FBG sensor can be designed such that the grating period can be increased for reflected light signals at wavelengths where higher power is desired, while the grating period can be reduced 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 changed to expand the width of the distinguishing spectral domain (e.g., 440a* or 440a**) without having to increase the total width of the transmission spectrum of the light source or the reflection spectrum of the FBG sensor. Increasing the transmission spectrum of the light source may increase the power consumption of the FBG interrogation system and the physical size of the FBG interrogation system.

[0133] In some variations, the FBG sensor may be a chirped FBG sensor, which may be formed with a gradually varying grating period. The grating period of the chirped FBG sensor may vary in such a way that the width of the distinct spectral domain 440* may cover at least the operating range of the FBG sensor.

[0134] Figure 5B A light source (e.g., Figure 1 The transmission spectrum 540 of the light source(s) 102 and the FBG sensor (e.g., Figure 150 ″ in the reflection spectrum 550 of the FBG sensor 106), which is configured to interact with each other on a distinct spectral domain 550* defined by a downward slope 550″ in the reflection spectrum 550 of the FBG sensor. For example, the transmission spectrum 540 of the light source and the reflection spectrum 550 of the FBG sensor can be made to interact with each other on a distinct spectral domain 550* in the reflection spectrum 550. Due to the reflected light signal (e.g., Figure 5B The power of the reflected light signal (e.g., 552) in the distinguishing spectral domain 550* varies monotonically in the distinguishing spectral domain 550*, and the distinguishing spectral domain has a minimum width covering the entire operating range of the FBG sensor, so the FBG interrogation system can be sensitive to changes in the physical signal within the operating range of the FBG sensor. The sensitivity of the FBG interrogation system can be increased by increasing the gradient of the downward slope defining the distinguishing spectral domain 550*. In addition, by increasing the width of the distinguishing spectral domain 550*, the reflected light spectrum 550 of the FBG sensor can be adapted to the operating range of the FBG sensor. In some variations, the reflected light signal (such as, for example, Figure 5B The power of 552) in can be defined by the following formula: where L(wl) represents the intensity of the transmission spectrum 540 of the light source, and F(wl) represents the reflectivity of the reflection spectrum 550 of the FBG sensor at wavelength wl.

[0135] In some variations, the FBG interrogation system may include multiple FBG sensors. For example, a single optical fiber may include more than one FBG sensor. Alternatively, the FBG interrogation system may include multiple optical fibers, thereby including multiple FBG sensors.

[0136] Example of interaction between FBG sensor and light source

[0137] In order to sense and obtain all possible values ​​of the physical signal that the FBG sensor can be configured to sense, the transmission spectrum of the light source and the reflection spectrum of the FBG sensor can be configured to interact in a distinguishing spectral domain. For example, the transmission spectrum of the light source and the reflection spectrum of the FBG sensor can be overlapped in the distinguishing spectral domain. The distinguishing spectral domain can be defined by a portion of the transmission spectrum of the light source and / or a portion of the reflection spectrum of the FBG sensor. The minimum width of the distinguishing 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. Changes in the physical signal sensed by the FBG sensor can cause a shift in the reflection spectrum of the FBG sensor. In response to the wavelength shift in the reflection spectrum, the power of the reflected light signal (reflected by the FBG sensor) can be monotonically changed in the distinguishing spectral domain, so that (one or more) Fabry-Perot interferometers can be eliminated. This in turn realizes the miniaturization of the FBG interrogation system for lower measurement frequencies of sensing physical signals with a relatively large range of values.

[0138] The FBG sensor and / or the light source can be designed so that the distinguishing spectral domain can have a minimum width covering the entire operating range of the FBG sensor. Additionally, the FBG sensor and / or the light source can be designed so that the slope (upward slope or downward slope) in the transmission spectrum of the light source or in the reflection spectrum of the FBG sensor defining the distinguishing spectral domain can have an increased gradient, thereby increasing the sensitivity of the FBG interrogation system.

[0139] In some variations, the FBG interrogation system may include a single light source having a transmission spectrum. The transmission spectrum may have a single spectral segment. In some variations, in order to sense physical signals using a single light source, the FBG interrogation system may adjust the single light source so that the transmission spectrum includes multiple spectral segments. For example, the FBG interrogation system may include a single light source so that the transmission spectrum of the light source can be adjusted (e.g., using one or more adjustment FBGs) to split it into multiple spectral segments. Alternatively, the FBG interrogation system may include multiple light sources, each having a corresponding transmission spectrum. In such a scenario, when the transmission spectrum includes multiple spectral segments and the reflection spectrum includes a single spectral segment, the FBG sensor may be designed so that the corresponding reflection spectrum of each FBG sensor can be configured to interact with one of the multiple spectral segments of the transmission spectrum of the light source on a corresponding distinguishing spectral domain.

[0140] In some variations, the FBG interrogation system may include multiple FBG sensors. Each FBG sensor may have a corresponding reflection spectrum. Therefore, the collective reflection spectrum of the FBG sensors may include multiple reflection spectrum fragments. In this scenario, the light source of the FBG interrogation system may be designed to include multiple transmission spectrum fragments, and the multiple transmission spectrum fragments may interact with each of the multiple reflection spectrum fragments of the FBG sensor on the corresponding distinguishing spectral domain.

[0141] Fig.10 FBG sensors (e.g., Figure 1 The reflectance spectra of the FBG sensor(s) 106 in FIG. 1 and two light sources (eg, Figure 11060 . The light source may be any suitable light source, such as, for example, a light source having a narrow bandwidth. Reflection spectrum 1050a may represent a reflection spectrum at one end of the operating range of the FBG sensor. When the FBG sensor is exposed to a change in the physical signal (e.g., strain), the reflection spectrum 1050a of the FBG sensor may shift. For example, reflection spectrum 1050a' may represent a shift of reflection spectrum 1050a when the FBG sensor is exposed to a change in the physical signal. Therefore, as an example, reflection spectrum 1050a' may represent a reflection spectrum at the other end of the operating range of the FBG sensor. The operating range of the FBG sensor is shown as 1060.

[0142] The transmission spectrum 1040a may represent the transmission spectrum of the first light source. Fig.10 As shown, the transmission spectrum 1040a of the first light source may be outside the operating range of the FBG sensor 1060. The output or power of the reflected light signal from the interaction between the transmission spectrum 1040a and the reflection spectrum 1050a is represented as 1070a. Fig.10 As shown, since the transmission spectrum 1040a is outside the operating range 1060 of the reflection spectrum 1050a, a change in the physical signal may not be detected from the output or power of the reflected optical signal 1070a of the FBG interrogation system.

[0143] In contrast, transmission spectrum 1040b may represent a transmission spectrum of a second light source that is different from the first light source. Fig.10 As shown, the transmission spectrum 1040b of the second light source is within the operating range 1060 of the FBG sensor. In addition, the transmission spectrum 1040b of the second light source interacts with the reflection spectrum 1050a' of the FBG sensor on a portion of the different spectral domain of the reflection spectrum 1050a' of the FBG sensor. For example, the transmission spectrum 1040b of the second light source interacts with the reflection spectrum 1050a' of the FBG sensor so that the power of the reflected light signal changes monotonically in response to the wavelength shift in the reflection spectrum 1050a'. Therefore, the output or power of the reflected light signal 1070b of this interaction may be sensitive to changes in the physical signal.

[0144] Fig.10 The representative data in are from a typical in vivo experiment in pigs, where the FBG sensor was incorporated into an ICD lead inserted into the right ventricle. The output or power of the reflected light signal indicates contraction and relaxation at low measurement frequencies and relatively large strain changes during the cardiac cycle.

[0145] Figures 6A-6E Showing a light source (e.g., Figure 1 102) and an exemplary transmission spectrum of a FBG sensor (e.g., Figure 1 Interaction between exemplary reflectance spectra of (one or more) FBG sensors 106) in the distinguishing spectral domain. Fig. 6A In the embodiment of the present invention, the reflection spectrum of the FBG sensor is narrow. For example, the FBG sensor can be a standard FBG sensor with a standard grating (e.g., type IA) and a narrow-band reflection spectrum. The operating range of the FBG sensor can be determined based on the possible values ​​of the physical signal that the FBG sensor is configured to sense (e.g., possible values ​​of strain in the heart, possible values ​​of mechanical movement of the heart, etc.). Fig. 6A In the embodiment, the light source can be an LED light source. The LED light source and the standard FBG sensor can be designed to interact in different spectral domains. For example, in Fig. 6A In the embodiment of the present invention, the difference spectral domain can be defined by the downward slope of the transmission spectrum of the LED light source. The transmission spectrum of the LED light source and the reflection spectrum of the FBG sensor can be configured to interact on the difference spectral domain. Since a portion of the downward slope of the transmission spectrum defining the difference spectral domain is monotonic as a whole, the change of the physical signal sensed by the FBG sensor can be quantitatively reflected by the corresponding change of the power of the reflected light signal.

[0146] exist Figure 6B In the embodiment, the reflection spectrum of the FBG sensor is wide. For example, the FBG sensor can be a modified chirped FBG sensor. The light source can be a narrowband light source (such as a distributed feedback diode (DFB)). The DFB and / or chirped FBG sensor can be designed to interact in a distinct spectral domain. Figure 6B In the embodiment of the present invention, the distinguishing spectral domain can be defined by the downward slope of the reflectance spectrum of the modified chirped FBG. Since the portion of the downward slope of the reflectance spectrum defining the distinguishing spectral domain is monotonic overall, the change of the physical signal sensed by the FBG sensor can be quantitatively reflected by the corresponding change of the power of the reflected optical signal.

[0147] exist Figure 6C In the embodiment of FIG. 1 , the reflection spectrum of the FBG sensor is broad. For example, the FBG sensor can be a modified chirped FBG sensor. However, Figure 6B different, Figure 6C The light source in can be a light source such as an LED having a broad transmission spectrum. Figure 6C In the embodiment, the distinction spectral domain can exist in both the upward or downward slope of the reflection spectrum of the FBG sensor and the transmission spectrum segment of the light source, so that the wavelength shift in the reflection spectrum of the FBG sensor can cause the interaction between the transmission spectrum of the light source and the reflection spectrum of the FBG sensor in the two distinction domains, thereby increasing the total distinction spectral domain width and the sensitivity of the EBG interrogation system in response to the change of the physical signal sensed by the FBG sensor.

[0148] As discussed herein, an FBG interrogation system may include multiple FBG sensors. These multiple FBG sensors may be formed on a single optical fiber. This may save space and make the FBG interrogation system less bulky, thereby miniaturizing the FBG interrogation system for integration into an implantable medical device while maintaining the ability to sense multiple physical signals and / or the ability to sense physical signals at multiple locations. The transmission spectrum of the light source may be configured to interact with each individual reflection spectrum of the multiple FBG sensors. Fig.6D The collective reflectance spectra of multiple FBG sensors multiplexed on a single optical fiber are shown. The light source can be a narrowband light source. The transmission spectrum of the light source can be configured to interact with the reflectance spectrum of a specific FBG sensor on a distinguishing spectral domain. In some variations, the FBG interrogation system can include multiple such light sources, each interacting with a different FBG sensor. In some variations, a small fiber optic switch can be included in the FBG interrogation system to switch between / among the light sources so that only one light source can be active at a time.

[0149] Fig. 6E The transmission spectrum of a light source split into multiple spectral segments is shown. Each spectral segment can be configured to interact with a corresponding reflection spectrum of a FBG sensor. In some variations, a light source having a single spectral segment in its transmission spectrum can be coupled to a tuning FBG to generate multiple spectral segments. The light source can be optically coupled to at least one tuning FBG to split the transmission spectrum of the light source into at least two spectral segments, each spectral segment being designed to interact with a corresponding FBG sensor.

[0150] Photodetector

[0151] In the miniaturized FBG interrogation system 100, more than one FBG sensor (e.g., Figure 1 In a variation of the (one or more) FBG sensors 106 in the optical fiber, the photodetector (e.g., (one or more) photodetector 104) can be designed so as to acquire and measure changes in the physical signal sensed by each FBG sensor on a single optical fiber. For example, the photodetector can be designed so that there can be more than one photodetector, each of which is coupled to a corresponding FBG sensor. In order to receive the reflection 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 can allow each of the photodetectors to receive a reflected light signal from its corresponding FBG sensor in response to the physical signal sensed by the corresponding FBG sensor.

[0152] Power Management Unit

[0153] 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 discussed above, the power supply may be controlled via the switch(es) (e.g., Fig. 12A 1208) enables and / or disables the supply of power to the light source and / or powered components, and may be controlled via a power regulation circuit (e.g., Fig. 12A 1206) regulates (e.g., increases or decreases) the amount of power delivered to the light source and / or powered component. In some variations, the (one or more) power regulating circuits and (one or more) switches may be packaged together as a single unit and may be integrated into the FBG interrogation system 100. Additionally or alternatively, at least one or more power regulating circuits and at least one or more switches may be separately integrated into the FBG interrogation system 100 as a single unit. In some variations, one or more switches may be coupled to one or more light sources and / or powered components and structurally or physically integrated into the FBG interrogation system 100 with the light and / or powered components to which the one or more switches are coupled. In a similar manner, at least one or more power regulating circuits may be coupled to one or more light sources and / or powered components and structurally or physically integrated into the FBG interrogation system 100 with the light sources and / or powered components to which the one or more power regulating circuits are coupled. In some variations, the switch(es) and the power conditioning circuit(s) may be designed in other structures or physical arrangements such that the physical size of the FBG interrogation system 100 is reduced, the power consumed by the FBG interrogation system 100 is minimized, and / or the heat generated from the FBG interrogation system 100 is reduced.

[0154] In some variations, the switch(es) in the PMU 109 may include at least one or more ultrafast power switches to enable and disable power delivered to the light source(s) 102 and / or powered components(s) in the FBG interrogation system 100. In some variations, the switch(es) may include off-chip off-the-shelf circuit components, such as, for example, Analog ADG901, ADG918 of the company. In some variations, (one or more) switches may include custom designed on-board switching circuits, which are composed of one or more packaged transistors (such as, for example, complementary metal oxide semiconductor (CMOS) transistors, bipolar junction transistors (BJTs), and gallium nitride (GaN) transistors). In some variations, (one or more) switches may include custom designed on-chip circuits based on CMOS, BJT, and GaN on-chip technologies, etc. The design of the on-chip switch may include one or more transistors, one or more on-chip resistors, and / or other logic circuits to achieve improved switching performance. In some variations, each power management mode described herein may have a dedicated power switch respectively. In some other variations, one or more switches may be used for more than one power management mode.

[0155] It should be understood that the physical arrangement or order between the switch(es) 1208 and the power conditioning circuit 1206 may vary. In some variations, the switch may be disposed before the power conditioning circuit for one light source or for one powered component. In some variations, the power conditioning circuit may be disposed before the switch for another light source or for another powered component.

[0156] In some variations, the PMU 109 may include at least one or more clock generation circuits to control the timing of the switch(es) individually or collectively. In some variations, the clock generation circuit may be used to control the switch(es) in the pulse mode. In some variations, the clock generation circuit may also be used to control the sampling rate or frequency of one or more powered components in the FBG interrogation system 100 for one or more modes of the power management mode (e.g., for the adaptive power mode). The clock generation circuit may be implemented with various circuit components such as a phase-locked loop (PLL) and a voltage-controlled oscillator (VCO) and a delay-locked loop (DLL), etc. In some variations, it may be necessary to change the clock frequency in one or more modes of the power management mode (e.g., for the pulse power mode or the adaptive power mode). In some variations, the clock frequency may be the same or different for the modes among the power management modes (e.g., for the pulse power mode or the adaptive power mode). The frequency may 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 change the phase and / or duty cycle of the (one or more) clock outputs. In some variations, (one or more) processors (e.g., Figure 1 (one or more) clock circuits in the processor 112).

[0157] In some variations, the PMU 109 may include at least one or more programmable power regulation circuits to regulate the amount of power delivered to the light source and / or one or more powered components in the FBG interrogation system 100 in an adaptive power management mode as described herein. As non-limiting examples, it may include on-chip / off-chip AC (alternating current)-DC (direct current) converters, DC (direct current)-DC (direct current) converters, or linear and low dropout (LDO) regulators. In some variations, the voltage and / or current may be controlled by an associated on-chip / off-chip programmable voltage or current converter, a digital-to-analog converter (DAC), which may include, as non-limiting examples, an on-chip / off-chip switched resistor DAC, a switched capacitor DAC, and / or an array of (one or more) switched current sources.

[0158] In some variations, the PMU 109 may include one or more processors to actuate switch(es) and power regulation circuit(s). In some variations, the PMU 109 may be coupled to one or more processors (e.g., Figure 1 The processor 112 in the processor 112) to actuate (one or more) switches and (one or more) power regulation circuits.

[0159] processor

[0160] Return to reference Figure 1 , the miniaturized FBG interrogation system 100 can be communicatively and / or operably coupled to a processor 112. The processor 112 (e.g., a central processing unit CPU or a microprocessor unit MPU) described herein can process data and / or other signals to control one or more components of the miniaturized FBG interrogation system 100. The processor 112 can be configured to receive, process, compile, calculate, 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 (one or more) FBG sensors 106 and / or photodetectors 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 interrogation system 100.

[0161] In some variations, the processor 112 may be communicatively coupled (e.g., wired or wirelessly) to a user interface. For example, the user interface may be a display on the processor 112 itself. In some variations, the user interface may be a display on any suitable computing device (e.g., a computer, a smart phone, a tablet, etc.) communicatively coupled to the processor 112. The user interface may include an input device (e.g., a touch screen, a keyboard, or a voice-activated input device) and an output device (e.g., a display device), and is configured to receive input from a user. In some variations, the input device may include a touch surface for a user to provide input to the miniaturized FBG interrogation system 100 (e.g., a finger contacting the touch surface).

[0162] In a variation in which the miniaturized FBG interrogation system 100 is integrated into an implantable medical device, the processor 112 may be inside and / or outside the implantable medical device. The processor may include instructions to automatically switch the miniaturized FBG interrogation system 100 from a power-off state to a power-on state via the power management unit 109. In the power-off state, the FBG interrogation system 100 may be dormant. For example, the (one or more) light sources 102 and / or powered components in the FBG interrogation system 100 may be disconnected. Additionally or alternatively, the FBG interrogation system 100 may not acquire, measure, and / or sense physical signals in the power-off state. In the power-on state, the FBG interrogation system may be operable. For example, the light sources 102 and / or powered components in the FBG interrogation system 100 may be turned on. Additionally, the FBG interrogation system 100 may be configured to sense, measure, and / or acquire physical signals in the power-on state.

[0163] The processor 112 may be configured to switch the FBG interrogation system 100 from a power-off state to a power-on state and then back to a power-off state based on the power management mode of the FBG interrogation system 100 via the PMU 109. For example, the power management mode may enable the power consumption of the FBG interrogation system 100 to be minimized. That is, the processor 112 may be configured to manage the power of the FBG interrogation system 100 via the PMU 109 based on the power management mode. In some variations, the processor 112 may be configured to operate the FBG interrogation system 100 continuously (i.e., continuous mode). In some variations, when the FBG interrogation system 100 is in the power-off state, the (one or more) light sources 102 and / or powered components of the FBG interrogation system 100 may be disconnected (e.g., disconnected by the processor 112 via the PMU 109). The FBG interrogation system 100 may not acquire or measure the physical signals that the (one or more) FBG sensors 106 are configured to sense in the power-off state. That is, in the power-off state, the FBG interrogation system 100 may be in a dormant state. In the powered-on state, the (one or more) light sources 102 and / or powered components of the FBG interrogation system 100 may be turned on (e.g., by the processor 112 via the PMU 109). The FBG interrogation system may acquire and measure the physical signals that the FBG sensor 106 is configured to sense in the powered-on state. That is, the FBG interrogation system 100 may be in an active state in the powered-on state. In some variations, the processor 112 may be configured to operate the FBG interrogation system 100 via the PMU 109 in at least five modes to minimize and / or manage power consumption, such as a continuous mode, an event-triggered mode, an event-gated mode, a pulse width modulation mode, and an adaptive power mode of power management. In the continuous mode, the processor 112 may be configured to continuously operate the FBG interrogation system 100.

[0164] In the event-triggered mode, the processor 112 can be configured to trigger the power-on state upon detection of a physical event, at preprogrammed intervals, and / or upon request from a user. For example, in the event-triggered mode of power management, the processor 112 can be configured to automatically trigger the power-on state in response to a triggering physical event in the subject (e.g., detection of a tachyarrhythmia, heart failure, ischemia, etc.). The triggering physical event can be detected by an implantable medical device (e.g., using electrodes and / or other sensors in an implantable medical device that monitors the subject) and / or by other devices that can be 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, the processor 112 can receive electrocardiogram (ECG) signals from the subject (e.g., from one or more electrodes disposed within the subject). The processor 112 can analyze these ECG signals. If processor 112 identifies an arrhythmia (such as a tachyarrhythmia) based on the analysis, the processor can automatically trigger a power-on state for miniaturized FBG interrogation system 100 via PMU 109 to enable the hemodynamic state of the subject to be assessed through data recorded from the miniaturized FBG interrogation system. For example, when analysis of the ECG signal (e.g., performed by processor 112) indicates the possibility of an abnormally increased heart rate (tachyarrhythmia), the miniaturized FBG interrogation system can be powered on and analysis of FBG parameters indicative of mechanical motion of the heart (such as myocardial strain of the ventricles) is performed to assess the hemodynamic state of the subject. If analysis of such parameters indicates that one or more values ​​of the FBG parameters may reach a threshold and / or threshold range, the hemodynamic state may be considered unstable. In response to detecting an unstable hemodynamic state, the processor 112 may automatically command the implantable medical device to perform further diagnostic tasks and / or therapeutic interventions (such as cardiac pacing and cardioversion / defibrillation), or additionally or alternatively, the processor 112 may alert the subject via an audible warning and / or vibration and via telemetry to summon professional help, including help from emergency medical services. Additionally or alternatively, the processor 112 may include instructions to automatically turn on or off one or more other components (e.g., powered components associated with the photodetector) in a similar manner via the PMU 109 in the miniaturized FBG interrogation system 100 to reduce power consumption.

[0165] In some variations, the processor 112 may be configured to analyze intrathoracic or pulmonary impedance measurements received from the subject. Intrathoracic or pulmonary impedance measurements that reach a threshold and / or a threshold range may indicate a worsening heart condition (e.g., heart failure). In response to detecting worsening heart failure, the processor 112 may automatically trigger a power-on mode of the miniaturized FBG interrogation system 100 via the PMU 109. Additionally or alternatively, the processor 112 may be configured to analyze the pulmonary artery pressure reflecting the left atrium. In response to detecting that the pulmonary artery pressure is above a threshold and / or a threshold range that may indicate a worsening heart condition (e.g., heart failure), the processor 112 may automatically trigger a power-on state for the miniaturized FBG interrogation system 100 via the PMU 109. In some variations, the 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 processor 112 (e.g., via a user interface) that FBG interrogation system 100 is to be activated (e.g., when the subject experiences chest pain or shortness of breath or syncope or when the user determines that such activation is indicated as well). In response to such notification, processor 112 may trigger a power-on state for miniaturized FBG interrogation system 100 via PMU 109.

[0166] In some variations, in the event-triggered mode, the processor 112 may automatically trigger the power-on state for the miniaturized FBG interrogation system 100 via the PMU 109 at a preprogrammed interrogation interval. For example, the processor 112 may include instructions to automatically trigger the power-on state via the PMU 109 at a specific interrogation interval. As a non-limiting example, the power-on state may be automatically triggered once or more times per day or per week to monitor the hemodynamic state of the subject. As another non-limiting example, the power-on state may be automatically triggered once or more times per month or several months to monitor the hemodynamic state of the subject and / or monitor the functional state of the miniaturized FBG interrogation system. In some variations, the processor 112 may be configured to trigger the power-on state via the PMU 109 based on a request from a user (e.g., as a non-limiting example, via a user interface that may be operated wirelessly via telemetry or Bluetooth).

[0167] In some variations, some physical events may occur at recurring intervals. The processor 112 may detect recurring physical events that occur at recurring intervals by analyzing (one or more) additional physical signals (e.g., triggering physical signals). For example, the processor 112 may be configured to adjust the power-on and power-off states of the miniaturized FBG interrogation system by analyzing an electrocardiogram signal representing cardiac electrical activity, a signal representing transthoracic and / or intrathoracic / pulmonary impedance measurements, a signal representing pulmonary or systemic arterial pulse measurements, a combination thereof, and the like. In response to detecting a recurring event, the processor 112 may operate the miniaturized FBG interrogation system 100 in an event-gated mode of power management via the PMU 109. In the event-gated mode, the processor 112 may quickly switch the miniaturized FBG interrogation system 100 from a power-off state to a power-on state at a specific moment (e.g., a gate point) during a cycle of a recurring event, and return to a power-off state after a short period of time or operating period that may be preset or dynamically determined via the PMU 109. The operation period can be hours or fractions of hours, minutes or fractions of minutes, seconds or fractions of seconds, milliseconds or fractions of milliseconds, microseconds or fractions of microseconds, etc. For example, the processor 112 can analyze the signal (e.g., trigger physical signal) representing the physiological condition of the subject (e.g., ECG signal, transthoracic impedance signal and / or intrathoracic impedance signal, etc.) and detect the cardiac cycle and / or respiratory cycle. In some variations, the processor 112 can convert the miniaturized FBG interrogation system 100 from the power-off state to the power-on state via the PMU 109 at the end of the systole and / or the end of the diastole of the cardiac cycle. Then, the processor 112 can convert the miniaturized FBG interrogation system 100 from the power-on state back to the power-off state via the PMU after the preset or dynamically determined operation period as described above. In a similar manner, the processor can convert the miniaturized FBG interrogation system 100 from the power-off state to the power-on state at the end of the inspiration and / or the end of the expiration of the respiratory cycle. The processor 112 may then transition the miniaturized FBG interrogation system 100 from the powered-on state back to the powered-off state after a preset or dynamically determined period of operation (eg, 3 cardiac cycles).

[0168] In some variations, the miniaturized FBG interrogation system 100 may be configured to operate in a pulse width modulation mode. In the pulse width modulation mode, the processor 112 may be configured to enable and disable power to the (one or more) light sources 102 and / or powered components (e.g., powered components associated with (one or more) photodetectors 104, etc.) of the miniaturized FBG interrogation system 100 via the PMU 109 in discrete pulses at an ultra-high frequency, so that the power consumption of the FBG interrogation system may be further minimized. For example, the (one or more) light sources 102 in the miniaturized interrogation system 100 may be pulsed light sources. The power delivered to the light sources may enable the processor 112 to transition the (one or more) light sources 102 from a powered-off state to a powered-on state in a discrete manner at an ultra-high frequency via the PMU 109. For example, the discrete power pulses may be transmitted at a duty cycle (e.g., Fig. 9 The duty cycle is represented in the form of a 50% duty cycle 992, a 75% duty cycle 994, and a 25% duty cycle 996), which indicates the proportion or percentage of time that the (one or more) light sources 102 will be turned on during the duration of the duty cycle, and the duration of the duty cycle is the sum of the time that the (one or more) light sources 102 will be turned on and the time that the (one or more) light sources 102 will be turned off during the duty cycle.

[0169] In some variations, the miniaturized FBG interrogation system 100 may be configured to operate in an adaptive power mode. In the adaptive power mode, the processor 112 may be configured to analyze the output amplitude of the photodetector 104 (which is highly correlated to the amplitude of the physical signal sensed by the (one or more) FBG sensor 106) and adjust or regulate the amount of power transmitted to the light source 102 and / or powered components via the PMU 109 to optimize the power consumption of the FBG interrogation system. For example, the processor 112 may be configured to reduce the amount of power transmitted to the light source 102 and / or powered components via the PMU 109 if the analysis of the output amplitude from the photodetector 104 exceeds a detection threshold. Conversely, the processor 112 may be configured to increase the amount of power transmitted to the light source 102 and / or powered components via the PMU 109 if the analysis of the output amplitude from the photodetector falls below a sensitivity threshold.

[0170] It should be readily understood that the miniaturized FBG interrogation system 100 can be configured to operate in an event-triggered mode, an event-gated mode, a pulse width modulation mode, or an adaptive power mode, independently or simultaneously. For example, the processor 112 can be configured to transition the miniaturized FBG interrogation system 100 from a power-off state to a power-on state (e.g., by turning on (one or more) light sources 102) in response to detecting a tachycardia. For example, in response to determining that the subject's heart rate has exceeded 150 beats per minute, the processor can detect a tachycardia. The processor 112 can then transition the miniaturized FBG interrogation system 100 from a power-off state to a power-on state. The miniaturized FBG interrogation system 100 can therefore operate in an event-triggered mode. Additionally, the processor 112 can cause the transition to last for a short gating period (e.g., approximately 50 milliseconds or approximately 100 milliseconds) only during the end-systolic and end-diastolic phases of a regular cardiac cycle, because the cardiac cycle is a recurring event. Thus, as a non-limiting example, once the processor 112 detects tachycardia, the processor 112 may transition the miniaturized FBG interrogation system 100 from the powered-off state to the powered-on state for a short operating period of approximately 50 milliseconds during the end-systolic and end-diastolic phases of the subject's cardiac cycle. Thus, the miniaturized FBG interrogation system 100 may be operated in both the event-triggered mode and the event-gated mode simultaneously. Additionally, during the powered-on state of the FBG interrogation system 100, the processor 112 may deliver power to the light source 102 in the form of discrete pulses with a duty cycle of 75%. Additionally, the amount of power delivered to the (one or more) light sources 102 and / or powered components of the FBG interrogation system (e.g., in the form of current to the light source) may be adaptively adjusted to balance power consumption with the sensitivity / accuracy of the FBG interrogation system, as described above. Thus, the miniaturized FBG interrogation system 100 may be operated in the event-triggered mode, the event-gated mode, the pulse width modulation mode, and the adaptive power mode simultaneously. Similarly, the miniaturized FBG interrogation system 100 can be configured to operate simultaneously in continuous mode, event-gated mode, pulse width modulation mode, and adaptive power mode or a combination of modes thereof. In some variations, only the continuous mode and the event-triggered mode may be mutually exclusive and may not operate simultaneously. In some variations, the continuous mode and the event-triggered mode may operate sequentially. Utilizing these power management modes can effectively and significantly reduce the power consumption of the miniaturized FBG interrogation system.

[0171] The modes of power management described herein for managing, minimizing, or optimizing power consumption are non-limiting examples. The miniaturized FBG interrogation system 100 may be configured to operate in other suitable modes. Additionally or alternatively, the power management modes described herein may also be implemented to control the power of various components (not just light sources) of the miniaturized FBG interrogation system 100. In addition, it should be understood that the power management modes described above may be used to manage, minimize, or optimize the power consumption of (one or more) systems or (one or more) devices having optical sensors (FBG sensors or non-FBG optical sensors) other than the miniaturized FBG interrogation systems described herein.

[0172] In some variations, the temperature variation 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 utilization of narrow-band light sources, the FBG interrogation system 100 described herein can generate minimal heat, thereby preventing a significant increase in temperature around the FBG interrogation system 100.

[0173] In this way, the miniaturized FBG interrogation system 100 can be operable and turned on only in response to physical events, during preprogrammed interrogation intervals, in response to requests from a user, and / or can be gated to recurring events. Thus, the (one or more) light sources 102 and / or powered components of the FBG interrogation system are turned on only when necessary. Additionally, with adaptive power modes, power consumption can be further optimized. This can reduce power consumption and extend the life of implantable medical devices that are typically battery-powered. The power management mode for managing, minimizing or optimizing power consumption can increase the durability or life of the implantable medical device into which the miniaturized FBG interrogation system 100 can be integrated. In some variations, such an implantable medical device (e.g., a battery-powered implantable medical device) can have a lifespan of at least 5 years or at least 10 years. Additionally, with power consumption minimized, the heat generated by the (one or more) light sources 102 (because they are only turned on when necessary) can be reduced to avoid adversely affecting the surrounding tissues and organs implanted with the miniaturized FBG interrogation system or causing discomfort to the subject or adversely affecting the implanted medical device itself.

[0174] method

[0175] Also described herein are methods employing or relating to the FBG interrogation system. Figure 7 , showing a miniaturized FBG interrogation system (e.g., similar in structure and / or function to Figure 1700 of an exemplary method 700 of the FBG interrogation system 100 in FIG. 700 may include selecting a light source (e.g., a light source that is structurally and / or functionally similar to a light source) at 702. Figure 1 (one or more) light sources 102 in the embodiment of the present invention) and / or FBG sensors (e.g., similar in structure and / or function to Figure 1 In some embodiments, selecting a light source and / or a FBG sensor may include determining an operating range of the FBG sensor. Selecting a light source and / or a FBG sensor may include identifying a distinct spectral domain defined in a transmission spectrum of the light source and / or a reflection spectrum of the FBG sensor (e.g., Figure 4 In some embodiments, the light source and / or the FBG sensor may include configuring the transmission spectrum of the light source and the reflection spectrum of the FBG sensor to interact in the distinguishing spectral domain, wherein the power of the reflected light signal from the FBG sensor is a monotonic function of the shift of its wavelength spectrum.

[0176] In some variations, selecting the light source can include optimizing the light source during pre-emission manufacturing (e.g., by changing the composition of the dopants, such as changing the arsenic and / or phosphorus composition for infrared emitters, by changing the composition of indium for blue / green emitters) 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 (one or more) FBGs) such that the transmission spectrum of the light source and the reflection spectrum of the FBG sensor interact in distinct spectral domains.

[0177] In some variations, selecting a FBG sensor may include changing the grating period of the FBG sensor, changing the number of gratings of a given grating period of the FBG sensor, changing the pattern of the distribution of gratings with different grating periods along the core of the optical fiber of the FBG sensor, changing the tilt or angle of the grating plane, changing the exposure time to ultraviolet light during writing of the grating on the optical fiber, changing the chemical composition of the core of the optical fiber so as to change the refractive index, introducing a gradient in the refractive index of the core of the optical fiber (e.g., by changing the tilt or angle of the grating plane and / or changing the exposure time to ultraviolet light), combinations thereof, etc., so that the distinguishing spectral domain has at least a width that can cover or adapt to the entire operating range of the FBG sensor. In some variations, selecting a FBG sensor may include selecting a non-uniform FBG sensor. In some variations, selecting a FBG sensor may include selecting a chirped FBG sensor.

[0178] In some variations, the method may further include: dividing the transmission spectrum of the light source into a plurality of spectral segments. For example, one or more FBGs (e.g., Figure 1The coupling of the FBG 110 to the light source can result in the transmission spectrum of the light source being split into a plurality of spectral segments. One or more spectral segments of the plurality of spectral segments can each be adapted to interact with the FBG sensor within the operating range of the corresponding FBG sensor.

[0179] In some variations, method 700 may include operating the miniaturized FBG interrogation system continuously. In some variations, method 700 may include automatically triggering a power-on state based on a mode of operation for power management (e.g., to minimize and / or manage power consumption) of the miniaturized FBG interrogation system. For example, in an event-triggered mode, method 700 may include automatically triggering a power-on state based on a physical event. A physical event may be determined based at least in part on a physical signal (e.g., a triggered physical signal) representing a physical condition. For example, the FBG interrogation system may be integrated into an implantable device. The method may include receiving an ECG signal from a subject at an implantable device and evaluating the presence of a tachyarrhythmia (physical event). In response to detecting a tachyarrhythmia, the method may include automatically turning on a light source and / or powered component of the miniaturized FBG interrogation system to evaluate the hemodynamic state of the subject. In some variations, in an event-triggered mode, method 700 may include automatically triggering a power-on state at preprogrammed intervals. In some variations, in an event-triggered mode, the method 700 may include automatically triggering a power-on state in response to a request from a user (e.g., an inquiry request). In some variations, in an event-gated mode, the method 700 may include automatically triggering a power-on state at a specific time point or time period during a recurring physical event. In addition, the method 700 may include switching the power-on state to a power-off state after a certain period of time. In some variations, the method 700 may include transmitting pulsed power to a light source and / or powered component of a miniaturized FBG interrogation system. In some variations, the method 700 may include adaptively adjusting the amount of power transmitted to (one or more) light sources and / or (one or more) powered components via a PMU to optimize the power consumption of the FBG interrogation system 100.

[0180] Powering on and / or turning on the light source may cause the light source to transmit an optical signal to the FBG sensor. At 704, the method may include receiving a reflected optical signal from the FBG sensor, the reflected optical signal 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. The measurement of the electrical signal may indicate a change in the physical signal. In some variations, when the miniaturized FBG interrogation system may be integrated into an implantable medical device (such as an ICD), method 700 may include issuing commands or instructions to inhibit and / or adjust the response of the implantable medical device to perform diagnostic and / or therapeutic functions (such as pacing and cardioversion / defibrillation).

[0181] Integrating miniaturized FBG interrogation systems into implantable medical devices

[0182] Since the FBG interrogation system described herein (e.g., Figure 1 The FBG interrogation system 100 in the embodiment can sense and measure physical signals of lower measurement frequencies without the need for bulky optical components such as optical Fabry-Perot interferometers, so the size of the FBG interrogation system can be significantly reduced. In addition, using optoelectronic co-packaging technology, the size and volume of the light source and / or FBG sensor can be very small. Therefore, the miniaturized FBG interrogation system can be integrated into a small-sized device. A non-limiting example described herein is to integrate the miniaturized FBG interrogation system into an implantable medical device (such as an implantable pacemaker (IPM), a cardioverter / defibrillator (ICD), an implantable cardiac monitor (ICM), etc.). In the implantable medical device, the miniaturized FBG interrogation system can be configured to evaluate physical signals (such as strain, pressure, temperature, etc.). The physical signal can indicate the physiological and / or pathophysiological state of the subject. For example, the physical signal can indicate the hemodynamic state of the subject. For example, the end-diastolic strain of the ventricle can indicate the end-diastolic volume of the ventricle. Similarly, the end-systolic strain of the ventricle can indicate the end-systolic volume of the ventricle. In some variations, the difference between end-diastolic strain and end-systolic strain may be indicative of stroke volume ( Fig.12E ). In some variations, the rate of change of strain during contraction can indicate the contraction rate or contractile 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 state of the subject can be determined during various conditions such as rest, sleep, walking, exercise, arrhythmia, heart failure (e.g., contraction, diastole), myocardial ischemia, etc. In addition, the miniaturized FBG interrogation system can be configured to reduce and / or minimize power consumption. This is important due to the limited supply of power in implantable medical devices. In addition, the miniaturized FBG interrogation system can be configured to minimize the heat generated from the implantable medical device (e.g., with reduced power consumption and a narrowband light source). Heat above a certain threshold may have an adverse effect on the subject (e.g., damage or discomfort to adjacent tissues and muscles) and / or on the implantable medical device.

[0183] Determining the physiological and / or pathophysiological state of a subject using an FBG interrogation system can help elicit and / or modulate a response from an implantable medical device, alert medical professionals involved in the subject's care, prompt timely medical diagnosis and treatment, etc.

[0184] Figure 8 A miniaturized FBG interrogation system (e.g., similar in structure and / or function to Figure 1The FBG interrogation system 100 in the embodiment of the present invention 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, memories, analog circuits, digital circuits, hybrid circuits, etc.), a battery, and if the implantable device is designed to release high-energy electric shocks (e.g., ICDs), it may include a capacitive element (e.g., a capacitor) for storing charge before delivering the electric shock and / or other hardware components (e.g., signal processing components) for detecting arrhythmias and delivering electric shocks or pacing stimulation. The pulse generator 815 may be implanted in any suitable area of ​​the subject's body. For example, the generator 815 may be subcutaneously implanted in the left pectoral area or the right pectoral area. In some variations, the pulse generator 815 may be substantially similar to the generator described in U.S. Publication No. US20200037895 (referred to as '895), entitled "Non-barometric Determination of Hemodynamic Effects of Cardiac Arrhythmias Using Signals Sensed by an Implantable Device," published on February 6, 2020. It should be readily understood that the terms generator and pulse generator may be used interchangeably herein.

[0185] One or more leads 817 may be connected to the pulse generator 815 at the head portion 815b. In some variations, the lead(s) 817 may be directly connected to the head portion 815b at a first end. Alternatively, in some variations, the first end of the lead 817 may be connected via a lead-generator interface unit 820 and then coupled to the pulse generator 815. The second end opposite the first end of the lead 817 may be inserted into one of the heart chambers, the coronary sinus, and / or the pericardial cavity surrounding the heart. The lead 817 may include one or more electrodes for delivering electrical current, such as one or more shock coils for delivering low-energy electrical stimulation to excite tissue (e.g., myocardium similar to a pacemaker) or for terminating or resetting arrhythmias with high electrical energy (i.e., cardioversion and defibrillation or ICD shocks). At least some of the electrodes on the lead(s) 817 may be used to sense the electrical activity of the heart (e.g., an electrocardiogram). In some variations, the electrodes configured to sense electrical activity may be the same electrodes / shock coils that may be used to deliver low / high current / energy for pacing or for cardioversion / defibrillation. In other variations, the electrodes configured to sense electrical activity may be different from the electrodes / shock coils configured to deliver low / high current / energy for pacing or for cardioversion / defibrillation.

[0186] In some variations, the implantable medical device can detect arrhythmias based on abnormal electrical activity sensed from one or more of these electrodes based on existing technology (e.g., electrocardiogram-based technology). In some variations, lead 817 can be substantially similar to the leads described in the '895 publication, which is incorporated herein by reference in its entirety. In some variations, lead 817 can be any suitable lead (e.g., an existing lead) for an implantable medical device. In addition, the implantable medical device can include any suitable number of leads 817. For example, a single-chamber ICD may include one lead in the right ventricle. A dual-chamber ICD may include two leads, one in the right atrium and the other in the right ventricle. A biventricular ICD may include three leads, one in the right atrium, one in the right ventricle, and one in the coronary sinus.

[0187] FBG sensor 806 (e.g., similar in structure and / or function to Figure 1The FBG sensor 106 in the implantable medical device can be embedded in one or more leads 817 of the implantable medical device. For example, the lead 817 may include an optical fiber on which the FBG sensor 806 can be formed. That is, the optical fiber can be part of the lead 817. Additionally or alternatively, the lead 817 can be attached to, integrated with, and / or coupled to an optical fiber on which a FBG sensor can 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 a single-chamber ICD and a dual-chamber ICD, the FBG sensor 806 can be embedded in (one or more) leads, which can be positioned in the right ventricle and / or both the right atrium and the right ventricle. Similarly, in a dual-chamber ICD, the FBG sensor 806 can be embedded in a lead positioned in the coronary sinus, the right atrium, and / or the right ventricle. In some variations, a lead 817 (e.g., a lead 817 having an FBG sensor 806 embedded in the lead 817) may include a high-energy shock coil. Alternatively, a lead 817 (e.g., a lead 817 having an FBG sensor 806 embedded in the lead 817) may not include a shock coil. For example, a lead in the coronary sinus, the pulmonary artery system, the right atrium, or the pericardial cavity may include an FBG sensor 806 but may not include a shock coil. In some variations, there may be one or more FBG sensors 806 embedded in one lead 817. Additionally, there may be one or more FBG sensors 806 embedded in more than one lead 817. In some variations, there may be one or more optical fibers embedded in each of the one or more leads 817, each having one or more FBG sensors.

[0188] The lead 817 with the embedded FBG sensor 806 may be coupled to the generator 815 via a lead-generator interface unit 820. The lead-generator interface unit may include an optocoupler 822, a power management unit 826 (e.g., similar in structure and / or function to a power management unit 826). Figure 1 ) and a processor 824 (e.g., similar in structure and / or function to the power management unit 109 in FIG. Figure 1 112 in the processor). The optocoupler (OEC) 822 may include a light source 802 (e.g., similar in structure and / or function to Figure 1 , a light source 102 in FIG. 1 ), a photodetector 804 (e.g., similar in structure and / or function to Figure 1 ) and an optical router 808 (e.g., similar in structure and / or function to Figure 1The lead-generator interface unit 820 may include a power management unit 825 (further detailed in FIG. 12 ) that may be electrically coupled to the optocoupler 822 and optionally to the power assembly. The lead-generator interface unit may also include a processor 824 (e.g., similar in structure and / or function to a processor 824) communicatively coupled to the optocoupler 822 and the power management unit 825. Figure 1 112 in the embodiment of the present invention). The lead-generator interface unit may also include a power source 826 communicatively coupled to the processor and / or electrically coupled to the light source 802. In some variations, the lead-generator interface unit may alternatively draw its power supply from the pulse generator 815. In other variations, the lead-generator interface unit has its own dedicated power supply or battery 826. Additionally or alternatively, the lead-generator interface unit may include an integrated circuit (such as a memory, an analog circuit, a digital circuit, a hybrid circuit, an analog-to-digital converter, a digital-to-analog converter).

[0189] The optical signal from the light source 802 may be transmitted to the FBG sensor 806 embedded in the lead 817 through the optical router 808. The photodetector 804 may convert the reflected optical signal from the FBG sensor 806 into an electrical signal through the optical router 808. The processor 824 (e.g., similar in structure and / or function to Figure 1 The processor 112 in the apparatus 824 may receive an electrical signal from the photodetector 804 and analyze the electrical signal. Based on the analysis, the processor 824 may control the function of the implantable medical device. The power supply or battery 826 may power the light source 802 via a power management unit (PMU) 825 so that the light source 802 may transmit an optical signal to the FBG sensor 806. The power supply or battery 826 may also power powered components associated with the photodetector 804 via the PMU 825, such as a preamplifier component associated with (one or more) photodetectors 104, an amplifier component associated with (one or more) photodetectors 104, an analog-to-digital conversion component associated with (one or more) photodetectors 104, a filter circuit associated with (one or more) photodetectors 104, and the like. It should be readily understood that the power supply or battery 826 may also power 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 may be disposed inside the lead-generator interface unit 820.

[0190] The various components of the lead-generator interface unit or LGIU 820 (e.g., optocoupler 822, light source 802, photodetector 804, optical router 808, processor 824, high energy switch 828, and PMU 825) may be disposed at any suitable location in the implantable medical device. For example, in some variations, the various components of the LGIU 820 may be disposed on, attached to, integrated with, or otherwise coupled to the lead 817. In some variations, the various components of the LGIU 820 may be disposed on, attached to, integrated with, or otherwise coupled to the head portion 815b of the generator 815. In some variations, the various 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 some elements of its components, may be positioned at a first location within the implantable medical device, while the remaining 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 various components of the LGIU 820 (e.g., an optocoupler, a light source, an optical router, or a photodetector or a PMU) or the various elements that the components of the LGIU 820 may comprise. For example, the light source 804 can be disposed on, attached to, integrated with, or otherwise coupled to the lead 817, and the photodetector can be disposed on, attached to, integrated with, or otherwise coupled to the head portion 815b of the pulse generator 815.

[0191] In some variations, the power management unit 825 of the lead-generator interface unit 820 may be disposed on, attached to, integrated with, or otherwise coupled to the lead 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, 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, some portion of the power management unit 825 may be positioned at a first location within the implantable medical device, while the remainder of the portion of the power management unit 825 is positioned at a second location within the implantable medical device. For example, the light source 802 may be coupled to, attached to, and / or otherwise integrated with one or more switches and / or power regulation circuits (e.g., switch(es) and / or power regulation circuit(s) of the power management unit). The light source 802, along with the coupled switch(es) and / or power regulation circuit(s), may be positioned within a head portion 815b or housing portion 815a of a generator 815 of the implantable medical device. In a similar manner, the powered components of the photodetector 804 may be coupled to, attached to, and / or otherwise integrated with one or more switches and / or power regulation circuit(s) of the power management unit. The photodetector 804, along with coupled switch(es) and / or power regulation circuit(s), may be positioned within a head portion 815b or housing portion 815a of a generator of an implantable medical device.

[0192] In some variations, the processor 824 of the lead-generator interface unit 820 may be disposed on, attached to, integrated with, or otherwise coupled to the lead 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, the power supply to the lead-generator interface unit may be provided from a battery or a set of batteries disposed inside the generator 815 (e.g., inside the housing 815a or the head 815b). Additionally or alternatively, the lead-generator interface may be powered by a battery or a set of batteries disposed external to the generator 815.

[0193] In some variations, the processor 824 of the lead-generator interface unit 820 can be configured to assess the hemodynamic state of the subject. For example, the processor can assess the hemodynamic state of the subject based on an analysis of one or more signals received from the optocoupler that can indicate a change in (one or more) physical signals. In response to determining that the hemodynamic state of the subject is stable, the processor can be configured to prevent the discharge of electrical energy from the capacitor included in the pulse generator 815 during a non-lethal cardiac tachyarrhythmia (such as sinus tachycardia or atrial fibrillation) or during a normal heart rhythm with electrical noise or electromagnetic noise or device oversensing. For example, this blocking can prevent the erroneous delivery of charge from the capacitor to the lead 817 (e.g., by disconnecting the high energy switch 828). In some variations, the high energy switch 828 can be provided in the generator housing 815a, the generator head 815b, or the lead 817 alone or together with other components of the lead-generator interface unit. Additionally or alternatively, in response to determining that the subject's hemodynamic state is stable, the processor can be configured to prevent charging of a capacitor included in generator 815 during a non-lethal cardiac tachyarrhythmia, such as sinus tachycardia or atrial fibrillation, or during a normal heart rhythm with electrical or electromagnetic noise or device oversensing. In this manner, the processor prevents the implantable medical device from erroneously delivering a shock.

[0194] Figure 12A-12E The power management unit 1200 ( Figure 12B-12E ) (structurally and / or functionally similar to Figure 8 PMU 825 and Figure 1The components of the PMU 109 ( Fig. 12A ) and operates to automatically turn on and off the power supply 1270 to the light source and / or other powered components and adjust the amount of power delivered to the light source and / or powered components 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 PMU 1200 may be performed by a processor 1202 (similar in structure and / or function to the Figure 8 The processor 824 and Figure 1 The processor 112 in the subject is controlled based on a preprogrammed algorithm or instructions stored in the processor 1202, and additionally or alternatively based on an analysis of physiological signals received from sensors disposed in the subject, the analysis of physiological signals may include but is not limited to the analysis of physiological signals received by sensors disposed in the lead ( Figure 8 817), transthoracic and / or intrathoracic impedance measurements that can indicate respiration and / or lung water content in the lungs as an index of heart failure, myocardial strain signals from the miniaturized FBG interrogation system itself (e.g., Figure 8 In some embodiments, Fig. 12A The processor 1202 in can be configured to open the switch 1208 to enable the power supply 1270 to the light source and powered components to evaluate the hemodynamic state of the subject and / or the mechanical function of the heart in a continuous mode, as described above. In some variations, when operating in a continuous mode simultaneously with an event-gated mode and / or a pulsed mode, an interruption of the power delivered to the light source and powered components can occur, as described below.

[0195] In some variations, Fig. 12A Processor 1202 in the embodiment may be configured to open switch 1208 to enable power supply to light source and powered component 1270 via PMU 1200 to assess the hemodynamic state and / or mechanical function of the heart in the subject when the need arises, i.e., PMU 1200 may be configured to operate in event-triggered mode ( Fig. 12B 1210) operates based on the information from the processor (e.g., Fig. 12A The processor 1202 in Figure 8 Processor 824 or Figure 1 For example, the processor 1202 may analyze signals from one or more electrodes (e.g., Figure 8The processor 1202 may sense the electrogram(s) of the subject's heart (those electrodes in leads 817 in the heart), and sense the ventricular electrogram (ventricular EGM), and optionally, from electrodes disposed in the atria (atrial EGM). If the processor 1202 detects a possible tachycardia or tachyarrhythmia based on this analysis that may indicate that the heart rate or ventricular rate has reached a certain rate threshold, the processor may automatically enable power supply 1270 to the light source and powered assembly 1270 via the PMU 1200 in order to assess the subject's hemodynamic state and / or mechanical function of the heart ( Fig. 12B ). For example, switch 1208 is closed until a ventricular tachyarrhythmia (VT) 1212 is detected through such analysis, thereby triggering processor 1202 to open switch 1208 via PMU 1200 to enable power supply 1270 to light sources and powered components 1270 to assess the hemodynamic state of the subject and / or mechanical function of the heart during VT, such as Fig. 12B , marked by the solid horizontal arrow starting at 1212 in . In some variations, the rate threshold may be preset by a user, or additionally or alternatively determined based on stored data on the output signal of the optocoupler collected during prior episode(s) of normal sinus rhythm, sinus tachycardia (e.g., during exercise), and / or prior episode(s) of non-lethal tachyarrhythmia, optionally in combination with further analysis of the ventricular EGM during the current tachycardia episode (with or without analysis of concurrent atrial EGM). In some variations, the analysis of the EGM may include, but is not limited to, analysis of ventricular EGM morphology, sudden or gradual onset of tachycardia, and association or dissociation between atrial and ventricular EGMs, and may affect the determination of the above 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, the stored data at the output of the optocoupler may be collected during a normal heart rate, a previous episode of sinus tachycardia (e.g., during exercise), and / or a previous episode of a non-lethal tachyarrhythmia and may include certain features (e.g., Fig.12E The output amplitude of the electromechanical delay 1252 in the embodiment of the present invention or the optocoupler at certain time events (e.g., end-diastole and end-systole), as described below, and their timing or their phase ( Fig.12E Once switch 1208 is turned on, the miniaturized FBG interrogation system integrated in the implantable medical device (e.g., ICD) can enter an operation period to detect the presence of an FBG sensor ( Figure 1 106 and Figure 8806 in ) to acquire or measure ventricular myocardial strain in order to assess the hemodynamic state of the subject and / or the mechanical function of the heart. As discussed above, the operating period can refer to a time period during which power supply to the light source and / or powered components can be enabled. At the end of the operating period, the switch can automatically close, and the miniaturized FBG interrogation system integrated in the implantable medical device (such as an ICD) can no longer acquire or measure the photocoupler ( Figure 8 822) or photodetector ( Figure 1 108 and Figure 8 The duration of the operation period can be pre-programmed (e.g., seconds, minutes, or hours) or determined by the processor 1202 based on the ventricular EMG (with or without the additional atrial EGM) and the optocoupler ( Figure 8 822) or photodetector ( Figure 1 108 and Figure 8804 in ). In some variations, such analysis may also include analysis of other inputs to the PMU 1200, such as transthoracic and / or intrathoracic impedance measurements. The operation period may end when the processor determines that VT has terminated based on analysis of the ventricular EGM and optionally additional atrial EGM. Additionally or alternatively, if the processor's analysis of the output of the photodetector (optionally combined with further EMG analysis) indicates a normal or stable hemodynamic state consistent with a normal or abnormal but non-fatal cardiac rhythm that may be misdiagnosed as a potentially fatal VT, the operation period may end before the termination of the detected possible VT. In some variations, such misdiagnosis may occur due to electrical noise or EGM oversensing. In some variations, such electrical noise may include, but is not limited to, electrical noise caused by lead breakage or electromagnetic interference. In some variations, such EGM oversensing may include T wave oversensing. In some variations, such abnormal non-fatal cardiac rhythms may include, but are not limited to, sinus tachycardia, supraventricular tachycardia, and atrial fibrillation with rapid ventricular response. In some variations, such abnormal non-lethal heart 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 the processor's analysis of the output of the optocoupler or photodetector indicates a significantly compromised hemodynamic state (such as an acute new onset or acute exacerbation of heart failure), the operating period may be extended beyond the termination of the detected VT to provide continued hemodynamic monitoring of the subject after the VT is spontaneously or successfully terminated by tachycardia therapy, which may include anti-tachycardia pacing, synchronized cardioversion, and / or defibrillation. The duration of this extended operating 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, such anti-tachycardia therapy may be delivered by an ICD or by an external device (such as an external defibrillator).

[0196] In some variations, the processor ( Fig. 12A 1202 of Figure 8 824 and / or Figure 1112) can control the function of an implantable medical device (e.g., an ICD) based on analysis of an output of an optocoupler that is measured or acquired during an operating period that is triggered by a detected possible tachycardia, as described above. For example, if analysis of the output of the optocoupler measured or acquired during the operating period indicates the presence of a stable hemodynamic state, and optionally combined with analysis of the ventricular EGM, indicates that an arrhythmia detected by the EGM analysis represents a misdiagnosis caused by electrical noise or EGM oversensing, the processor can signal or instruct the ICD to prevent or terminate anti-tachycardia therapy. In some variations, preventing anti-tachycardia therapy can include preventing anti-tachycardia pacing (ATP) and / or charging (one or more) capacitors in the ICD when a high-energy shock is expected. In some variations, terminating anti-tachycardia therapy can be accomplished by disconnecting a high-energy switch ( Figure 8 828 in ) to prevent the already charged (one or more) capacitors from releasing high energy to the subject (i.e., aborted ICD discharge). As yet another example, if analysis of the output of the photocoupler measured or acquired during the operational period indicates the presence of a stable hemodynamic state, and optionally combined with analysis of the ventricular EGM, indicates that the arrhythmia detected by the EGM analysis represents a true ventricular tachycardia (VT), the processor may signal or instruct the ICD to perform ATP but avoid high-energy ICD shocks. In some variations, based on analysis of the output of the photocoupler during a detected VT, the processor may signal or instruct the ICD to continue ATP without the need for (one or more) high-energy ICD shocks as long as the hemodynamic state remains stable. It should be readily understood that the output of the photodetector and the output of the photocoupler are two terms that may be used interchangeably herein.

[0197] In a similar manner, the processor 1202 may analyze the water content or impedance or left atrial pressure across the lung / thorax of the subject. If, based on the analysis, the processor detects possible worsening heart failure, the processor 1202 may automatically open the switch 1208 of the PMU 1200 to enable power supply to the light source and / or powered component 1270 to assess the subject's hemodynamic state and / or the mechanical function of the heart. In a similar manner, the processor may detect evidence of ischemia in response to being notified of an onset of chest pain in the subject. The processor 1202 may automatically open the switch 1208 of the PMU 1200 to enable power supply to the light source and / or powered component 1270 to assess the subject's hemodynamic state and / or the mechanical function of the heart. In addition, the processor 1202 may automatically open the switch 1208 of the PMU 1200 to enable power supply to the light source and / or other powered component 1270 at regularly scheduled intervals to monitor the subject's hemodynamic state and / or the mechanical function of the heart. In addition, the processor 1202 can automatically open the switch 1208 of the PMU 1200 to enable power supply to the light source and / or other powered components 1270 when recommended or requested by the user through a wireless user interface (e.g., Bluetooth or telemetry as non-limiting examples) to assess the hemodynamic state of the subject and / or the mechanical function of the heart. It should be readily understood that the mechanical function of the heart includes the systolic and diastolic function of the heart. In some variations, based on the assessment of the hemodynamic state of the subject and / or the mechanical function of the heart based on analysis of the output of the optocoupler, the processor can communicate with the implantable medical device or instruct the implantable medical device to alert the subject through an audible warning and / or vibration and / or through telemetry to summon professional help, including help from emergency medical services.

[0198] In some variations, processor 1202 may be configured to turn on PMU 1200. Fig. 12A 1208 in the embodiment of the present invention to enable power supply to the light source and / or powered component 1270 to evaluate the hemodynamic state of the subject and / or the mechanical function of the heart during certain portions of one or more recurring events, i.e., PMU 1200 can be operated in event-gated mode ( Fig. 12C 1220) to reduce power consumption. Thus, a single operating period may be gated to one or more recurring events. In some variations, such recurring events may include, but are not limited to, cardiac cycles and respiratory cycles. For example, the processor 1202 may be configured to open the switch 1208 of the PMU 1200 to enable power supply to the light source and / or power supply component 1270 after the end of inspiration 1222a marked by the horizontal long dashed arrow 1229. Fig. 12C1224, 1226, and 1228 of the first three cardiac cycles, as marked by the horizontal shorter solid arrows. In some variations, the duration of the operating period for each of the first three cardiac cycles can be the same or different. In some variations, such duration of the operating period can be preprogrammed to be approximately 0 milliseconds (msec), 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 the ventricular EGM. Additionally or alternatively, such duration of the operating period can be dynamically determined based on analysis of the output of the optocoupler or photodetector and gated to a specific time interval during a single cardiac cycle, as further described herein below. In some variations, such a certain time interval can be controlled by an electromechanical delay ( Fig.12E In some variations, such a specific time interval may start a few milliseconds or tens of milliseconds before the beginning of end diastole, at the beginning of end diastole, or a few milliseconds or tens of milliseconds after the beginning of end diastole (e.g., Fig.12E S ED 1254). In some variations, such a specific time interval may end a few milliseconds or tens of milliseconds before the onset of end systole, at the onset of end systole, or a few milliseconds or tens of milliseconds after the onset of end systole (e.g., Fig.12E S ES 1255). In some variations, such a specific time interval may start a few milliseconds or tens of milliseconds before the onset of ventricular EGM end-diastole, at the onset of ventricular EGM end-diastole, or a few milliseconds or tens of milliseconds after the onset of ventricular EGM end-diastole, and end a few milliseconds or tens of milliseconds before the onset of the T wave, at the onset of the T wave, or a few milliseconds or tens of milliseconds after the onset of the T wave (as represented by Fig.12E It should be readily appreciated that such a particular time interval may start or end based on any combination of these time markers derived by analyzing the output of the cardiac EGM and / or the optocoupler or photodetector, depending on the specific application.

[0199] In some variations, processor 1202 may be configured to modulate power to light source and / or powered component 1270 in a pulsed manner via PMU 1200 during an operating period to assess hemodynamic status and / or mechanical function of the heart in a subject during a portion of one or more recurring one or more events, i.e., PMU 1200 may modulate power to light source and / or powered component 1270 in a pulsed manner .... Fig.12D1230) 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 822 in is adaptively adjusted, as described below, to further optimize power consumption ( Fig.12E ).

[0200] In some variations, the processor 1202 may be configured to be based on an optocoupler ( Figure 8 822) to adaptively adjust the amount of power delivered to the light source and / or powered component 1270 via the PMU 1200 to assess the hemodynamic state of the subject and / or the mechanical function of the heart during certain portions of one or more recurring events, i.e., the PMU 1200 may be in an adaptive power mode ( Fig.12E 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 Fig.12E S max 1256 and S min 1257) or the difference between the end-diastolic value and the end-systolic value (respectively Fig.12E S ED 1254 and S ES 1255) or the end-diastolic value and the minimum value (respectively Fig.12E S ED 1254 and S min 1257). In some variations, S ES 1255 and Smin 1257 may be identical in timing and value. In some variations, S ED 1254 and S max 1256 can generally differ in timing and value. In some variations, S ED 1254 can be at a certain delay ( Fig.12E The electromechanical delay or EMD 1252 in the heart may occur after about 10, 20, 50, 100, or 120 milliseconds after the onset of ventricular electrical activation (marked by the upward pointing solid arrow). In some variations, the EMD 1252 may be determined based on analysis of ventricular myocardial strain data extracted from the output of the optocoupler during normal heart rhythm and / or during a previous arrhythmia episode. In some variations, S ES1255 may occur at the beginning of a T wave (as indicated by the upward pointing hollow arrow). In some variations, the processor 1202 may be configured to reduce the amount of power delivered to the light source and / or powered component 1270 via the PMU 1200 if the output amplitude of the optocoupler exceeds a certain detection threshold, which is present when the output amplitude of the optocoupler exceeds a certain detection threshold. Fig. 12A in the form of a reduced voltage from the voltage source 1211, or in the form of a Fig. 12A In some embodiments, the detection threshold may be defined as an output amplitude above which an adequate hemodynamic state (e.g., adequate stroke volume) may be accurately and reliably assessed. In some embodiments, the processor 1202 may be configured to increase the amount of power transmitted to the light source and / or powered component 1270 via the PMU 1200 in the form of an increased voltage through the voltage source 1211, or in the form of an increased current through the current source 1213, or in the form of an increased duty cycle, or in any combination thereof as described above, if the output amplitude of the optocoupler approaches or falls below a particular sensitivity threshold. The sensitivity threshold may be defined as an output amplitude of the optocoupler below which an adequate hemodynamic state (e.g., adequate stroke volume) may not be accurately and reliably assessed. In some embodiments, the detection threshold may be greater than or equal to the sensitivity threshold. In some variations, the detection threshold and sensitivity threshold may be pre-programmed or dynamically determined based on analysis of data of the output amplitude of the optocoupler during normal heart rhythm and / or during previously recorded abnormal heart rate episodes. In some variations, such analysis may be performed using pre-programmed algorithms and / or machine learning based on data from the same subject or from a similar population of subjects with an implantable medical device (such as an ICD). It should be understood that the light source described herein may include at least one light source or a plurality of light sources.

[0201] As discussed above, the lead-generator interface unit 820 may include a power management unit (e.g., similar in structure and / or function to the power management unit 820). Figure 1 A power management unit (PMU) 109 in the embodiment of the present invention can be used to reduce and / or minimize power consumption and heat generation. In some embodiments, the PMU can include Fig. 12A The processor 1202 in the PMU can actuate one or more switches and / or one or more power regulation circuits included in the PMU. Alternatively or additionally, the PMU can be connected to Figure 8 Processor 824 or Figure 1The processor 102 in the PMU is coupled to actuate one or more switches and / or one or more power regulation circuits in the PMU. In some variations, the processor can be configured via the PMU to turn on the light source and / or the powered component in response to a physical condition (e.g., tachycardia, heart failure, ischemia) that meets a threshold standard or is triggered by a physical condition that meets a threshold standard. In some variations, the processor can be configured to automatically turn on the light source and / or the powered component at predetermined time intervals via the PMU. In some variations, the 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 can be configured to automatically enable the power supply to the light source and / or the powered component via the PMU in response to a request from the user. In some variations, the light source and / or the powered component can be gated to a recurring physical event (e.g., a cardiac cycle). Additionally or alternatively, the processor can be configured to quickly enable and disable the power supply to the light source and the powered component based on a specific duty cycle via the PMU. Additionally or alternatively, the processor may 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 sensitivity and accuracy of a miniaturized FBG interrogation system incorporated into an implantable medical device.

[0202] Although Figure 8 The implantable medical device is described as including leads 817, but it should be readily appreciated that the miniaturized FBG interrogation system described herein may be integrated into a leadless implantable medical device. Fig.11A A leadless implantable medical device having splines (such as, for example, 1154a, 1154b, 1154c, 1154d, collectively referred to as splines 1154) is shown. Splines 1154 can be configured to maintain the implantable medical device in place (i.e., passively fix the device) within a subject's body (e.g., as a non-limiting example, in the right ventricle). In some variations, one or more splines 1154 of the implantable medical device configured to maintain the device in place can be embedded with one or more FBG sensors (e.g., similar in structure and function to a FBG sensor). Figure 1(One or more) FBG sensors 106 in the leadless implantable medical device). In some variations, one or more separate releasable splines 1154 can be attached to, coupled to and / or accommodated in one or more grooves or recesses on the body of the leadless implantable medical device and released only after implantation into the subject to make close contact with the surrounding tissue, as further described below. Such separate splines can be embedded with one or more optical fibers, each having one or more FBG sensors. Thus, some or all of the splines of the implantable medical device can be embedded with (one or more) FBG sensors and can hold the device in place, or sense physical signals, or perform both functions.

[0203] Additionally or alternatively, some leadless implantable medical devices may include one or more grooves and / or recesses on the body of the implantable medical device to accommodate (one or more) releasable splines coupled to the device. Fig. 11B and 11C In the embodiment of the present invention, the leadless implantable medical device 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 spiral 1158 to maintain the leadless device (i.e., active fixation device) in place within the subject's body (e.g., as a non-limiting example, in the right ventricle). The grooves may include a spline (such as a spiral) for attaching the spline to the implantable medical device. Fig. 11C 1154a and 1154b in the leadless implantable medical device) are coupled to a releasable mechanism (e.g., a spring, etc.) in the grooves 1156a and 1156b, respectively. As a non-limiting example, during implantation of the leadless implantable medical device into the subject and / or shortly thereafter (e.g., minutes, hours, or days thereafter), the releasable mechanism in the grooves can release the splines so that the splines 1154a and 1154b are released to engage surrounding tissue (such as the endocardial myocardial tissue of the right ventricle), such as Fig. 11C As shown. These splines can be embedded with FBG sensors to sense physical signals. Additionally or alternatively, the splines can be releasably retained in grooves on the body of the leadless implantable device via a biodegradable material, so that the splines are fully embedded in the body of the leadless implantable medical device prior to implantation and are released only after a desired exposure or contact time with body fluids (such as blood) during and / or after implantation. In some variations, the remaining components of the miniaturized FBG interrogation system (e.g., light sources, photodetectors, powered components, PMUs, etc.) can be disposed in the body of the leadless implantable system. In some variations, the miniaturized FBG interrogation system can communicate wirelessly or by telemetry with another implantable medical device within the subject and / or a medical device outside the subject's body.

[0204] For the purpose of explanation, the foregoing description uses specific terms to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that specific details are not required in order to implement the present invention. Therefore, the foregoing descriptions of specific embodiments of the present invention are presented for the purpose of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise form disclosed; obviously, many modifications and variations are possible in view of the above teachings. The embodiments are selected and described in order to explain the principles of the present invention and its practical application, so that other persons skilled in the art can utilize the present invention and various embodiments with various modifications suitable for the intended specific use. The following claims and their equivalents are intended to define the scope of the present invention.

Claims

1. A miniaturized fiber Bragg grating (FBG) interrogation system comprising: at least one light source, the at least one light source having a transmission spectrum; at least one FBG sensor, the at least one FBG sensor comprising a plurality of Bragg gratings, wherein the at least one FBG sensor has a reflection spectrum and is configured to receive an optical signal from the at least one light source, the at least one FBG sensor further configured to generate a reflected optical signal representing a change in a physical signal sensed by the at least one FBG sensor; as well as a photodetector optically coupled to the at least one FBG sensor and configured to convert the reflected light signal into an electrical signal, Therein, the at least one light source and the at least one FBG sensor are configured such that the transmission spectrum and the reflection spectrum interact with each other in distinct spectral domains.

2. The system according to claim 1 further includes a power management unit (PMU), which is electrically coupled to the at least one light source, or optionally, the power management unit (PMU) is electrically coupled to at least one powered component of the system.

3. The system according to claim 2, 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.

4. The system according to claim 3, wherein: The one or more processors are configured to automatically turn on the at least one light source in response to a cardiac arrhythmia detected in the event triggered mode.

5. The system according to claim 3, wherein: The one or more processors are configured to turn on the at least one light source in response to a request from a user.

6. The system according to claim 1, wherein: The life of the system is at least 5 years.

7. The system according to claim 1, wherein: The at least one light source has a bandwidth ranging from about 0.1 nm to about 1.5 nm.

8. The system according to claim 1, wherein: The at least one light source is a doped semiconductor, a narrow-band laser diode, a quantum dot, or a vertical cavity surface emitting laser.

9. The system according to claim 1, wherein: The at least one FBG sensor has a bandwidth between about 0.25 nm and about 15.25 nm.

10. The system according to claim 1, wherein: At least one FBG has a diameter less than about 250 μm.

11. The system according to claim 1, wherein: A change in the electrical signal indicates a change in the physical signal.

12. The system of claim 1, wherein: The physical signal is at least one of strain, temperature and pressure.

13. The system of claim 1, wherein: The distinctive spectral domain is a region defined by at least one of a first portion of the transmission spectrum of the at least one light source and a second portion of the reflection spectrum of the at least one FBG sensor.

14. The system according to claim 13, wherein: The width of the distinct spectral domain is based at least in part on an operating range of the at least one FBG sensor.

15. The system of claim 14, wherein: The operating range of the at least one FBG sensor is between about 0.5 nm and about 15 nm.

16. The system of claim 13, wherein: The distinctive spectral domain is a region defined by the second portion of the reflection spectrum, and wherein a width and a monotonic gradient of the distinctive spectral domain are based at least in part on an arrangement of the plurality of Bragg gratings of the at least one FBG sensor.

17. The system of claim 16, wherein: The arrangement comprises an increase in the number of the plurality of Bragg gratings, a decrease in the number of the plurality of Bragg gratings, or a gradual change in the periodicity of the plurality of Bragg gratings.

18. The system of claim 1, wherein: In response to a shift in the reflection spectrum of the at least one FBG sensor, the power of the reflected optical signal varies monotonically over the distinctive spectral domain.

19. The system of claim 1, wherein: The system is coupled to an implantable medical device.

20. The system of claim 19, wherein: The implantable medical device is an implantable cardioverter / defibrillator (ICD).

21. The system of claim 20, wherein: The at least one FBG is embedded in a lead of the ICD.

22. The system of claim 21, wherein: The ICD includes at least one ICD processor configured to: receiving an electrocardiogram signal from at least one electrode disposed in the subject; and Arrhythmia is detected in the subject based on the electrocardiogram signal.

23. An implantable cardiac device comprising: a lead configured for cardioversion / defibrillation, pacing, and / or sensing, wherein the lead 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 a transmission spectrum of the light source over a distinct spectral domain, and generate a reflected optical signal representative of a change in a physical signal sensed by the FBG sensor; an interface unit coupled to the lead; A photoelectric coupler, the photoelectric coupler is arranged in the interface unit, and the photoelectric coupler comprises: the light source; a photodetector for converting the reflected light signal into an electrical signal; and A processor, the processor being configured to: analyzing the electrical signal received from the photodetector; and A function of the implantable cardiac device is controlled based on the analysis.

24. The implantable cardiac device of claim 23, wherein: The processor is coupled to a power management unit (PMU).

25. The implantable cardiac device of claim 24, 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.

26. The implantable cardiac device of claim 25, wherein: The processor is configured to automatically turn on the light source in response to a cardiac arrhythmia detected in the event triggered mode.

27. The implantable cardiac device of claim 26, wherein: The arrhythmia is detected based on analysis of the electrogram and, optionally, myocardial strain sensed by the at least one FBG sensor.

28. A method comprising: selecting at least one of a light source and a fiber Bragg grating (FBG) sensor for use in a FBG interrogation system such that a first portion of a transmission spectrum of the light source is configured to interact with a second portion of a reflection spectrum of the FBG sensor in a distinct spectral domain; transmitting an optical signal via the light source; receiving a reflected light signal from the FBG sensor, the reflected light signal representing a change in a physical signal sensed by the FBG sensor; as well as The reflected light signal is converted into an electrical signal at a photodetector, wherein a measurement of the electrical signal is indicative of a change in the physical signal.

29. The method of claim 28, further comprising reducing power consumption of the FBG interrogation system using a power management unit (PMU).

30. A power management unit, comprising: a processor coupled to the one or more switches; as well as one or more power regulation circuits coupled to the one or more switches, the one or more power regulation circuits configured to transition the FBG interrogation system from a dormant state to an operational state, Wherein the processor is configured to operate in a continuous mode, an event-triggered mode, an event-gated mode, a pulse width modulation mode, an adaptive power mode, or a combination thereof.

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