Fiber optic sensor system for ultrasonic sensing and imaging

Abstract

The invention relates to a fiber optic sensor system for ultrasonic sensing and imaging. An optical fiber based acoustic sensor is provided herein. An optical fiber-based acoustic sensor described herein includes an acoustically responsive optical structure configured to detect and receive acoustic signals, including ultrasonic signals, and provide associated optical signals to the system for processing and interpretation to implement tracking, positioning, and imaging capabilities. Optical fiber-based sensors provided herein may be disposed at the end of an optical fiber or along the length of the optical fiber. The fiber-based sensors may be included within various devices, including, for example, medical devices.

Description

[0001] Related Applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 510,079, entitled “FIBER-OPTICAL SENSOR SYSTEM FOR ULTRASOUND SENSING AND IMAGING” and filed on June 23, 2023, which is incorporated herein by reference. This application is further related to U.S. Provisional Application No. 63 / 522,793, entitled “OPTICAL FIBER WITH AN ACOUSTICALLY SENSITIVE FIBER BRAGG GRATING AND ULTRASOUND SENSOR INCLUDING THE SAME” and filed on June 23, 2023, which is incorporated herein by reference. This application is further related to U.S. Provisional Application No. 63 / 522,994, entitled “TRANSPONDER TRACKING AND ULTRASOUND IMAGE ENHANCEMENT” and filed on June 23, 2023, which is incorporated herein by reference. This application is further related to U.S. Patent Application No. 63 / 522,994, entitled “TRANSPONDER TRACKING AND ULTRASOUND IMAGE ENHANCEMENT”, filed in parallel on October 23, 2023, which is incorporated herein by reference. This application further incorporates by reference the U.S. Provisional Patent Application entitled “Miniature Mixed Array Imaging Probe,” filed on October 23, 2023, and having Attorney Docket No. 109835-1386207, which is incorporated herein by reference. Technical Field

[0003] The present invention relates generally to the field of ultrasound sensing and imaging. Background Art

[0004] Acoustic imaging is used in various industries including medical imaging. Acoustic imaging technology can be used to visualize and provide internal imaging of the patient's body. In addition, acoustic imaging technology can be used to visualize and track objects (e.g., needles, catheters, guide wires, endoscopes, etc.) for medical applications such as diagnostic or therapeutic clinical procedures, including but not limited to biopsy, liquid aspiration, delivery of therapeutic agents such as drugs, nerve blocks / anesthesia or biological agents, catheter insertion, needle guidance, needle placement, deep vein cannulation, injection, IV, PIC line placement, device implantation, minimally invasive surgery, etc. Acoustic imaging is used for medical applications to provide several advantages. For example, acoustic imaging such as ultrasound imaging is a non-invasive imaging form. In addition, ultrasound imaging uses ultrasound signals known to have significant penetration depth.

[0005] In non-medical applications, ultrasound is used in industrial applications such as flaw detection, non-destructive testing, structural testing, and microparticle particle sorting; in geological applications including mining and drilling operations; and in underwater marine applications.

[0006] Some existing imaging technologies use acoustic energy generation (AEG) materials for transducers to visualize and track medical objects and generate images during diagnosis or treatment of medical procedures. Commonly used AEG materials include piezoelectric materials, such as lead zirconate titanate (PZT), ceramics, piezoelectric single crystals (such as PIN-PT, PIN-PMN-PT) and polyvinylidene fluoride (PVDF) and many other materials known to those skilled in the art. AEG transducers have limitations. The echoes of the object to be tracked and / or the anatomical structure being visualized can affect the image quality of the object being tracked and the tissue being imaged. In some medical procedures, a small form factor is required, and a small AEG transducer generally has a low to minimum signal output. Therefore, due to size limitations (e.g., physical size), it may be challenging to use AEG transducers for medical applications that require a small form factor.

[0007] Therefore, especially in medical applications, new and improved compact technologies with high sensitivity are needed to visualize and track objects and provide anatomical imaging. Summary of the invention

[0008] Systems, devices, and methods for ultrasound sensing and imaging are presented herein. In particular, the systems, devices, and methods described herein may include fiber optic microsensor devices and systems and methods of use.

[0009] In an embodiment, an apparatus is provided, comprising a sensor optical fiber. The sensor optical fiber may include: an optical waveguide including a core and a cladding structure; an optical sensor structure coupled to a first end of the optical waveguide and including at least one of an optical resonator, an optical interferometer, and a polarization-sensitive structure, the optical sensor structure configured to: detect an acoustic signal, and provide an optical signal corresponding to the acoustic signal to the optical waveguide. The sensor optical fiber may further include an encapsulation structure, the encapsulation structure configured with a first portion surrounding the optical waveguide and a second portion at least partially surrounding the optical sensor structure.

[0010] In some aspects, the devices described herein relate to an apparatus comprising: a sensor optical fiber comprising: an optical waveguide comprising a core and a cladding structure; an optical sensor structure coupled to a first end of the optical waveguide and comprising at least one of an optical resonator, an optical interferometer, a facet end microstructure, and a polarization-sensitive structure, the optical sensor structure being configured to: detect an acoustic signal and provide an optical signal corresponding to the acoustic signal to the optical waveguide. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The drawings incorporated herein form part of the specification and illustrate embodiments of systems, methods, and devices for ultrasonic sensing and imaging. Together with the specification, the drawings further explain the principles of the methods, systems, and devices described herein and enable those skilled in the relevant art to make and use the methods, systems, and devices described herein. The drawings are provided to illustrate various features of the embodiments described herein and are not necessarily drawn to scale. In the drawings, similar reference numerals represent identical or functionally similar elements.

[0012] Figure 1 An optical sensor system for use with a fiber optic sensor according to an embodiment of the present invention is shown.

[0013] Figure 2 An optical sensor system for use with a fiber optic sensor according to an embodiment of the present invention is shown.

[0014] Figure 3A A sensor fiber including a fiber optic sensor and associated optical fibers is shown.

[0015] Figure 3B A sensor fiber comprising an optical waveguide and an optical resonator structure having a Fabry-Perot resonator as an optical sensor is shown.

[0016] Figure 4A-4E Several variations of optical resonator structures according to embodiments of the invention are shown.

[0017] Figure 5A and 5B Examples of an optical sensor system and a fiber optic sensor according to an embodiment of the present invention are shown.

[0018] Figure 5C and 5D Examples of an optical sensor system and a fiber optic sensor according to an embodiment of the present invention are shown.

[0019] Figure 5E and 5F An example of a microfacet structure according to an embodiment of the present invention is shown.

[0020] Figures 6A-6E Examples of an optical sensor system and a fiber optic sensor according to an embodiment of the present invention are shown.

[0021] Fig. 6F and 6G Examples of an optical sensor system and a fiber optic sensor according to an embodiment of the present invention are shown.

[0022] Figure 6H and 6I Examples of an optical sensor system and a fiber optic sensor according to an embodiment of the present invention are shown.

[0023] Figure 7A-7D Examples of manufacturing techniques that may be used to shape or process the ends of optical waveguides are provided.

[0024] Figure 8A-8D Examples of fabrication techniques that may be used to fabricate optical resonator structures at the ends of optical waveguides are provided.

[0025] Figures 9A-9B A method of thermal tuning applied to a sensor fiber is shown.

[0026] Fig.10 An embodiment of a sensor optical fiber comprising a multi-core optical waveguide is shown.

[0027] Fig.11A and Fig. 11B A comparison between sensor fibers arranged with a forward optical sensor and a side optical sensor is shown.

[0028] Fig.12 An embodiment of a sensor fiber providing rear-view acoustic detection capability in accordance with an embodiment of the present invention is shown.

[0029] Fig.13 An embodiment of a sensor fiber providing enhanced rear-view acoustic detection capabilities in accordance with an embodiment of the present invention is shown.

[0030] Fig.14The directional range of the optical resonant structure according to an embodiment of the present invention is shown.

[0031] Fig.15 An optical resonator structure including a fiber Bragg grating according to an embodiment of the present invention is shown.

[0032] Fig.16 A method of operating a fiber-optic based optical sensor according to an embodiment of the present invention is shown.

[0033] Figures 17A-17B A needle configured with a sensor optical fiber according to embodiments herein is shown.

[0034] Figures 18A-18D A needle configured with a sensor optical fiber according to embodiments herein is shown.

[0035] Fig.19 An acoustic signal incident on the sensor fiber from a sideways direction is shown.

[0036] Figures 20A-20B A close-up view of a needle with an integrated sensor fiber is provided in accordance with an embodiment of the present invention.

[0037] Figures 20C-20D A needle is shown having a sensor optical fiber incorporated therein according to an embodiment of the present invention.

[0038] Fig.21 The distal end of a medical device is shown with a needle for transcatheter delivery in accordance with an embodiment of the present invention.

[0039] Fig. 22 The use of fiber-optic based optical sensors in needle guidance or positioning is shown.

[0040] Figures 23A-23B A needle for transcatheter delivery is shown with a fiber-optic based optical sensor. DETAILED DESCRIPTION

[0041] Non-limiting examples of various aspects and variations of the present invention are described herein and shown in the accompanying drawings. The following detailed description is illustrative in nature and is not intended to limit the present invention or the application and use of the present invention. Although the description of the present invention is carried out in the context of fiber optic microsensor systems, methods and devices for ultrasonic imaging and sensing, the present disclosure should not be considered to be limited thereto. For example, although the method may be discussed in this article about various medical procedures, embodiments of the present invention may be suitable for other medical procedures, as well as other procedures or methods in other industries that can benefit from the sensing and imaging technology described herein. In addition, various systems and devices incorporating fiber optic microsensors are described. It should be understood that, as described herein, fiber optic microsensors can be integrated into various systems and devices not described herein and / or used with them. Without departing from the spirit and scope of the present invention, the embodiments described herein may be modified. Therefore, the following detailed description is not intended to be limiting. In addition, it is not intended to be constrained by any express or implied theory presented in the aforementioned technical field, background technology, content of the invention or the following detailed description.

[0042] Various structures are described herein in terms of their geometrical properties. As discussed herein, all structures so described may vary from the described shapes in accordance with the tolerances of known manufacturing techniques. Unless otherwise specified, features described with the term "substantially" should be understood to be within a 5% accuracy range. For example, features described as "substantially parallel" may deviate from true parallelism by 5%.

[0043] Disclosed are systems, devices, and methods for ultrasonic sensing and imaging using fiber optic microsensors or fiber optic sensor devices. In particular, the technology described herein can track, visualize, and monitor (e.g., sense) an object during a medical procedure, as well as generate an ultrasonic image. The fiber optic microsensor device described herein incorporates an optical device that is disposed at the end of an optical fiber or at a specified position along its length and is configured to detect acoustic signals, including ultrasonic signals. As described herein, the sensor fiber includes an optical waveguide (e.g., an optical fiber) having a fiber optic microsensor device coupled at its end. As used herein, the term optical waveguide may refer to an optical fiber, a fiber core, a photonic integrated waveguide, a planar waveguide, and the like, based on a material system such as molten glass, a polymer, a semiconductor / dielectric wafer, a nanoimprint / 3D printed polymer on a different substrate, or any other optical signal channel.

[0044] The technology described herein is compact in size and has high sensitivity, making it suitable for a variety of industrial applications as well as therapeutic and diagnostic medical applications. In non-medical applications, ultrasound is used for industrial applications such as defect detection, non-destructive testing, structural testing, and microparticle particle sorting, geological applications including mining and drilling operations, and underwater marine applications. Such applications are consistent with the embodiments described herein. Therapeutic and diagnostic medical applications include ultrasound imaging and sensing (tracking, visualization, guidance, and monitoring) of objects (e.g., needles, catheters, guidewires, etc.) during guided needle entry, biopsy, aspiration, delivery of drugs, biologics, anesthesia or other therapeutic agents, catheter insertion, minimally invasive surgery, ablation, cauterization, object placement or movement, tissue, cutting and / or slicing, and other medical procedures. Procedures and applications in the following disciplines are examples of diagnostic and therapeutic procedures that are widely used and require precise guidance and imaging: anesthesia, cardiology, critical care, dermatology, emergency medicine, endocrinology, gastroenterology, obstetrics and gynecology, hepatology, infectious diseases, interventional radiology, musculoskeletal medicine, nephrology, neurology, oncology, orthopedics, pain management, pediatrics, plastic and reconstructive surgery, urology, and vascular access.

[0045] Visualization, tracking, guidance, and location determination of objects in medical applications may be important aspects of performing medical procedures in a safe and reliable manner. Objects for tracking, visualization, and location determination may include any type of medical device that travels or is positioned in the subject's body. For example, a doctor visualizes and tracks the needle tip when performing a biopsy to ensure safety. In this case, accurate needle tip visualization or tracking can help prevent or reduce unintentional damage to blood vessels, nerves, tissues, or internal organs. Similarly, when performing medical procedures, it may be helpful to visualize, track, or locate needles, endoscopes, cannulas, laparoscopic tools, or other medical device tools, such as but not limited to: fluid aspiration; injection of joints, tendons, and nerves with drugs or biological agents; biopsy of fluid or soft tissue masses; aspiration and lavage of calcifications; removal of tissue, organs, or foreign bodies, placement of stents, filters, valves, permanent, temporary, or biodegradable implants, shunts, or drainage tubes, anesthesia injections, insertion of vascular access devices for infusion therapy, ablation procedures, performing Seldinger techniques or catheterization to access blood vessels and / or other organs in a safe manner. Visualization and tracking are advantageous in laparoscopic, minimally invasive, and open surgical procedures, especially when areas are difficult to visualize due to limited access, intervening tissues or organs, blood, or other fluids.

[0046] Some existing technologies use ultrasound imaging for guidance during medical procedures to visualize anatomical structures of interest, as well as to visualize, locate and track inserted medical devices, especially the distal and / or working parts of the devices. However, there are several disadvantages associated with traditional ultrasound imaging techniques for medical applications. Traditional techniques use imaging probes that transmit ultrasound waves. Since needles and other inserted medical devices have smooth surfaces, incident ultrasound waves reflected from the surface can be directed away from the receiving direction. This may make the reflected waves too weak to be easily detected, making it difficult to determine the position of the device during surgery. In some technologies, the medical device may have a rough surface, such as a recessed, etched or coated surface, to increase visibility in ultrasound by increasing the echo of the medical device. However, even with these efforts, there are still limitations. Ultrasound-guided tools may also be limited by their dependence on specific incident angles, which limits their ability to provide accurate visualization, especially for deeply placed devices. Due to this limitation, ultrasound-guided tools may be placed in surface locations, which limits their practicality, adoption and cost-effectiveness as deployable solutions.

[0047] Compared to the proposed optical sensing technology, there are at least two key acoustic performance limitations in prior art AEG transducers (such as but not limited to lead zirconate titanate (PZT), ceramics, piezoelectric single crystals (such as PIN-PT, PIN-PMN-PT), and polyvinylidene fluoride (PVDF)). First, achieving very high sensitivity requires transducers made of specific AEG materials or specific acoustic designs, but such transducers may only provide relatively narrow acoustic response bandwidths. Second, when the size of the electrical component becomes small relative to its resonant frequency, the acoustic response of the AEG transducer may be limited due to electrical impedance mismatch. Therefore, for applications that require a small form factor (such as intravascular or intracardiac ultrasound, endoscopy, needle tracking, lung biopsy, sensing and monitoring, etc.), the signal-to-noise ratio (SNR) and bandwidth of small AEG transducers are reduced. And a highly directional response may also be presented in some applications. In addition, some AEG transducers and systems may be affected by electromagnetic interference, such as electromagnetic interference caused by ablation tools, cauterization tools, or any other procedures or techniques for applying electrical energy to tissue. Furthermore, the use of an electromechanical transducer at the distal end would involve conductive wires and associated components requiring additional design and safety requirements and challenges.

[0048] In contrast, the fiber optic sensor according to the present disclosure can provide an ultrasound receiver with high sensitivity, wide bandwidth and wide acceptance angle, and does not require the electrical components required by the electromechanical transducer. With these characteristics, the fiber optic sensor will be able to sense harmonics or scattered signals that cannot be sensed by the prior art. In addition, the fiber optic sensor consistent with the present disclosure can be compact, low-cost, and can contribute to a scalable sensor system. An embodiment of the present invention includes a fiber optic sensor configured to detect an acoustic signal. Such a fiber optic sensor can be placed at the end of an optical fiber, near the end of an optical fiber, or at a diagnostic or treatment-related position on a medical device to produce a sensor optical fiber. The fiber optic sensor includes a resonant structure, including but not limited to a Fabry-Perot (FP) resonator, an optical cavity resonator, a whispering gallery mode resonator, and a photonic crystal resonator; an optical interferometer, including but not limited to an MZI, a phase-shifted coherence interferometer, a self-mixing interferometer; an acoustically responsive fiber end face; and an acoustically induced birefringence polarization sensor.

[0049] The acoustically responsive fiber end face may include a substrate suitable for adding various microstructures to enhance the response of the fiber sensor to the acoustic signal. Such microstructures may be: acoustically responsive structures, such as metasurfaces containing patterns of small elements (e.g., having a size less than approximately one wavelength of the optical signal) arranged to change the wavefront shape of the acoustic signal and maximize the detection of the acoustic signal; acoustically responsive low-dimensional materials with special optomechanical features that are more easily deformed; and plasma structures patterned to amplify light-matter interactions. In addition to operating as an optical sensor, the fiber end face structure may also be added to other optical fiber sensors described herein to further enhance the acoustic response. For example, a metasurface may contain patterns of small elements that are arranged to change the wavefront shape of the acoustic signal and maximize the collection of acoustic signals collected by other types of optical fiber sensors discussed herein to improve the sensitivity of the optical fiber sensor. Adding low-dimensional materials to the fiber end face may also increase sensitivity because such materials are more susceptible to deformation caused by acoustic waves, which can translate into greater changes in the optical signal. By writing a plasma pattern on the fiber end face, the optical response to the acoustic wave can be enhanced. This enhancement can be achieved by exploiting the hot spots and resonances generated by these plasmon patterns to amplify the light-matter interaction. As used herein, "low-dimensional" or "two-dimensional" features may refer to features having a thickness of less than 1 micron.

[0050] The above-mentioned optical structures are configured to respond to acoustic signals (e.g., ultrasonic signals). Therefore, these optical structures may include acoustically responsive materials and / or acoustically responsive structures. As used herein, acoustic response refers to a structure or material that is configured to respond to an incident acoustic signal (e.g., an ultrasonic acoustic signal) in a manner that adjusts the optical properties of the material or structure. The response to the acoustic signal in such a resonant, interferometer, or acoustically responsive optical fiber end face structure may be due to the photoelastic effect and / or physical deformation of the structure. When affected by an acoustic signal, the resonant, interferometer, or acoustically responsive optical fiber end face structure is subjected to mechanical stress and / or strain from the alternating pressure of the acoustic signal sound wave. Such mechanical stress and / or strain may change the optical properties of the optical sensor structure due to the photoelastic effect, and may also cause changes or deformations in the physical structure of the resonator. For polarization-based sensors, when the medium through which the light passes is subjected to an acoustic signal, the polarization of the optical signal changes. When coupled to a light source (e.g., a laser source, a broadband light source (e.g., a lamp or LED), or other suitable light source) via an optical waveguide (e.g., an optical fiber), the effect of the acoustic signal on the optical sensor structure can be measured due to the change in the light returned by the optical sensor structure via the optical waveguide. In the present disclosure, the optical signal and the light can be referred to as a response to the acoustic signal. It is understood that this response is due to the interaction between the acoustic signal and the medium through which the light passes. Therefore, as discussed herein, a so-called acoustically responsive material or structure can respond to a typical acoustic signal of an ultrasound environment in a manner measured by an optical signal according to embodiments of the present invention through the techniques described herein.

[0051] Embodiments of the present invention include systems configured for use with fiber optic sensors. For example, a system according to the present disclosure may include a light source (e.g., a laser source, a broadband light source (e.g., a lamp or LED) or other suitable light source), a light receiving device (e.g., a photodetector, etc.), an optical device (splitter, combiner, circulator, polarization sensitive coupler, polarization analyzer, polarization controller, frequency shifter, etc.), a control device, a computer processing unit, and other devices to facilitate the function of the fiber optic sensor. In addition, such a system according to the present disclosure may include acoustic devices, such as transducers, probes, and hardware / software for their control. A system according to the present disclosure may further include medical systems and devices, including all devices, systems, hardware, and software necessary to perform any medical procedure that the fiber optic sensor is used to facilitate.

[0052] Figure 1An optical sensor system for use with a fiber optic sensor is shown. As used herein, the term "fiber optic sensor" and the term "optical sensor based on optical fiber" refer to an optical sensor adapted and / or configured to detect an acoustic signal, as described in further detail below. The optical sensor system 100A includes a light source 104, such as a laser, a light receiving device 103, such as a photodetector, one or more optical waveguides 105, an optical circulator 102, and a fiber optic sensor 101. In operation, the light source 104 supplies an initial optical signal 111 to the fiber optic sensor 101 via the optical waveguide 105 and through the optical circulator 102. The supplied initial optical signal 111 returns through the fiber optic sensor 101 along the optical waveguide 105. The returned optical signal 112 travels through the optical circulator 102 via the optical waveguide 105 and is received at the light receiving device 103. As discussed above, the acoustic signal incident on the fiber optic sensor 101 changes the optical properties of the fiber optic sensor 101 (which may include physical structure as well as optical material properties). Such optical property changes may be measured based on changes in the returned optical signal 112, as discussed in more detail below.

[0053] Figure 2 2. The photoacoustic sensor system 200 is shown for use with a fiber optic sensor. The photoacoustic sensor system 200 includes a method for facilitating the use of a fiber optic sensor 101 or a fiber optic sensor array 201 (comprising a plurality of fiber optic sensors 101, such as Figure 2 Components, devices, hardware and software used in the description). Further reference Figure 2 The use of a single fiber optic sensor 101 may be specifically referred to; however, it should be understood that in additional embodiments, a fiber optic sensor array 201 may be incorporated into a photoacoustic sensor system 200 in conjunction with any of the features discussed below, and any functions attributed to the fiber optic sensor 101 may further be performed by the fiber optic sensor array 201. In an embodiment, for example Figure 2 As shown, the photoacoustic sensor system 200 may include hardware and components for facilitating the use of an ultrasonic transducer and / or an ultrasonic probe. The ultrasonic transducer may be used to generate and receive acoustic signals, or only to generate acoustic signals. The photoacoustic sensor system 200 may include a processing system 250, an optical subsystem 215, and an output device 208.

[0054] The processing system 250 may include a processing unit 209 and an image reconstruction unit 206. The processing unit 209 may include at least one computer processor, at least one non-transitory computer-readable storage medium, and appropriate software instructions. The processing unit 209 is configured to provide control signals to and receive information signals from the light source control unit 207, the light receiving device 203, and the acoustic control unit 222. The processing unit 209 may communicate with the light source control unit 207 (via control signals and information signals), thereby providing control of the light signal provided to the optical fiber sensor 101. The processing unit 209 may communicate with the acoustic control unit 222 (via control signals and information signals), thereby providing control and reception of the acoustic signal via the acoustic probe 245. The processing unit 209 is further configured to communicate with the light receiving device 203 to receive an information signal associated with the light signal received by the light receiving device 203. Therefore, the processing unit 209 is used to provide the required control signals and receive the acquired information signals in the photoacoustic sensor system 200.

[0055] The processing unit 209 also communicates with an image reconstruction unit 206, which is used to generate an image based on the data and / or information acquired by the processing unit 209. The image reconstruction unit 206 can generate an image based on data related to a medium such as a human body captured by the fiber optic sensor 101 and the acoustic probe 245. The medical device distal end 231 may include one or more of a needle, a catheter, a guidewire, a delivery device, and / or any other device or equipment configured to be used in a patient's body. The image reconstruction unit 206 can be integrated into a system containing the processing unit 209, and / or can be a separate system including at least one computer processor, at least one non-transitory computer-readable storage medium, and appropriate software instructions. The processing system 250 can provide a control signal to the output device 208 to provide a data output. The output device 208 can include, for example, a display or a device including a display.

[0056] In some embodiments, the output device 208 may further include additional systems, such as medical procedure systems configured to use the data as output. For example, the output device 208 may include an endoscopic system, a laparoscopic system, a robotic surgery system, a neurosurgical system, and may additionally include an interoperable ultrasound imaging system. The output data may include information about the location of the distal end or working portion 231 of the medical device, and images of media acquired in the area where the distal end 231 of the medical device is used / deployed, such as patient anatomy, tissue, other medical tools / devices, etc.

[0057] The optical subsystem 215 includes a light source control unit 207, a light source 204, optical devices 202A, 202B, 202C and 202D, and a light receiving device 203. The light source control unit is configured to interface with the light source 204 and control the light source 204 to control the generation of the initial light signal 211. The light source can generate continuous wave (CW) or pulsed light emission (stimulated emission, spontaneous emission, etc.). The initial light signal 211 may include coherent light provided at one or more frequencies in one or more modes, such as a laser. The initial light signal 211 may have a single frequency / wavelength, a series of frequencies / wavelengths, and / or a broadband light source. Therefore, the light source 204 may include a laser array configured to generate laser light at one or more frequencies in one or more modes. In addition, the polarization of the supplied light can be controlled according to the application requirements to optimize the detected signal level. The polarization state of the light can be controlled to be linearly polarized or circularly polarized at a specific angle. Linearly polarized light will respond best to a specific input ultrasound direction, while circularly polarized light will respond to ultrasound in all directions. The polarization of the light can be defined based on the laser source output, and the output polarization state can be controlled by an in-line fiber polarizer, a paddle fiber polarization controller, an in-line fiber polarization controller, or other types of polarization controllers. The optical devices 202A, 202B, and 202C can be configured to manipulate or influence the initial optical signal 211 received at the fiber sensor 101. The initial optical signal 211 can be provided at multiple wavelengths or across a wavelength spectrum. The optical device 202A can include, for example, a wavelength division multiplexing (WDM) device configured to multiplex multiple frequencies of the initial optical signal 211 provided by the light source 204 for simultaneous transmission through the optical waveguide 205, which guides the initial optical signal 211 to the optical fiber end optical sensor 101. The optical device 202B can be a circulator having first, second, and third ports, wherein the first port is in optical communication with the light source through the wavelength division multiplexing device (WDM) 202A. The initial optical signal 211 may pass through the second optical device 202B, which may be, for example, an optical circulator, and is configured to direct the initial optical signal 211 to the optical device 202C. The optical device 202C may include a WDM device configured to demultiplex the initial optical signal 211 provided to the optical fiber sensor 101, which may be part of the array 201, so that each of the plurality of optical fiber sensors 101 receives and subsequently outputs light of a different wavelength. The optical device 202C is in optical communication with the second port of the second optical device 202B to split the initial optical signal into optical signals each having one of the wavelengths associated therewith, and to combine the optical signals returned from the optical fiber sensors 101, which are then directed to the optical receiving device 203 through the third port and the optical device 202D, which may include a WDM device.

[0058] The initial optical signal 211 is received by the fiber optic sensor 101 (or the optical sensor 101 of the fiber optic sensor array 201 in some embodiments) and is returned to the optical device 202C through one or more optical waveguides 205, which may be further configured to multiplex the returned optical signal 212 (if necessary) for transmission to the optical receiving device 203. The returned optical signal 212 is guided by the optical device 202C through the optical device 202B and toward the optical device 202D, which may be a WDM device configured to demultiplex the returned optical signal 212 for reception by the optical receiving device 203.

[0059] The optical device 202D may be in optical communication with the third port of the optical device 202B to receive the returned optical signal and separate it into individual wavelength components. For example, the optical receiving device 203, which may be a photodetector array, may be in optical communication with the optical device 202D to receive the individual wavelength components of the returned optical signal, so that the phase shift or other changes in the detected individual wavelength components indicate the sensed acoustic signal.

[0060] It should be understood that in embodiments where the initial optical signal 211 and the returned optical signal 212 do not require frequency multiplexing / demultiplexing, the optical devices 202A and 202C may not be required. The optical receiving device 203 may include any suitable device configured to detect incident light, including, for example, a photodetector. The optical receiving device 203 may further include, but is not limited to, a photodiode. The optical receiving device 203 may be in optical communication with the optical device 202D (e.g., a wavelength division multiplexing beam splitter) to receive the individual wavelength components of the returned optical signal 212, so that the phase shift, polarization change, or other change of the detected individual wavelength components indicates the sensed acoustic signal. The change in the returned optical signal 212 can be converted (e.g., by the processing unit 209 and / or by additional optical components, such as a polarization sensitive coupler and / or a frequency shifter) into data representing the sensed acoustic signal (e.g., which can be further used to generate a tissue / anatomical structure representing the medium in which the distal end 231 of the medical device is inserted in the area of ​​the diagnostic or therapeutic surgery and / or for identifying the position of the distal end 231 of the medical device in the medium). In an embodiment, these signals (initial optical signal 211 and returned optical signal 212) may be subjected to pre-processing, beamforming, and post-processing as described in the following documents.The following applications disclose various methods for ultrasonic beamforming and image processing: US application 18 / 032,953, filed on April 20, 2023, entitled “Image Compounding for Mixed Ultrasound Sensor Array”; US application 18 / 205,081, filed on March 7, 2023, entitled “Synthetic Aperture Imaging Systems and Methods Using Mixed Arrays”; US application 18 / 901,073, filed on December 29, 2022, entitled “Acousto-Optic Harmonic Imaging with Optical Sensors”; PCT application PCT / US2022 / 077762, filed on October 7, 2022, entitled “Ultrasound Beacon Visualization with Optical Sensors”. Sensors); PCT application PCT / US2022 / 041250, filed on August 23, 2022, entitled “Multi-Dimensional Signal Detection with Optical Sensor”; and PCT application PCT / US2022 / 018515, filed on March 2, 2022, entitled “Acoustic Imaging and Measurements Using Windowed Nonlinear Frequency Modulation Chirp”, each of which is incorporated herein by reference. The image and / or data representing the distal end 231 of the medical device (or the fiber optic sensor 101) can then be displayed to the user on the output device 208, which may include a computer display, etc. The image and / or data representing the distal end of the medical device may further include the distal portion of the medical device in the acoustic transmission area.

[0061] As discussed above, the light receiving device 203 is in communication with the processing unit 209. The processing unit 209 receives from the light receiving device 203 an information signal representing the returned light signal 212 received at the light receiving device 203. The processing unit 209 may also receive from the light control unit 207 an information signal representing the initial light signal 211 output by the light source 204. The processing unit 209 is used to process the information signal associated with the returned light signal 212 (optionally compared to the information signal associated with the initial light signal 211) to determine the acoustic environment at the fiber optic sensor 101, as further discussed below. The acoustic environment determination may include the detection, identification and interpretation of acoustic signals incident to one or more fiber optic sensors 101 of the fiber optic sensor array 201. The processing unit 209 may determine the presence and nature of the acoustic signal incident to the one or more fiber optic sensors 101.

[0062] Thus, the fiber optic sensor 101 can be used to detect and / or receive an acoustic signal (e.g., an ultrasound signal), and provide an optical signal representing the acoustic signal and consistent with the acoustic signal to the optical receiving device 203 through an optical receiving chain (e.g., optical devices 202C, 202B, 202D), and the optical receiving device is configured to detect and / or receive the optical signal and provide an electrical signal representing the optical signal and consistent with the optical signal to the processing unit 209 for processing and interpretation. Thus, the processing unit 209 can be configured to receive an electrical signal representing the received acoustic signal and consistent with the received acoustic signal, and process and interpret the electrical signal to reconstruct an image from the acoustic signal. For example, an ultrasound image can be reconstructed using the delay-and-sum beamforming principle (a common way to reconstruct ultrasound images). In delay-and-sum beamforming, the spatial distribution of the ultrasound field amplitude in the volume of interest (image area) is reshaped according to the delay between transmission, image pixels and receivers, and thus the received ultrasound signal is recombined for the purpose of generating an image. In delay-and-sum beamforming, the signals are coherently added at each image pixel location according to the delay.

[0063] The processing unit 209 may further communicate with an acoustic control unit 222. The acoustic control unit 222 may be configured to provide control data to and receive signal data from the acoustic probe 245 and / or the acoustic transducer 221. The acoustic probe 245 may be configured for use in vitro or in vivo, and may include an AEG transducer or an AEG transducer array (or any other suitable acoustic transducer) configured to generate and / or receive an acoustic signal, such as an ultrasonic signal. The acoustic probe 245 may also include a hybrid array of both an AEG transducer (or any other suitable acoustic transducer) configured to generate and / or receive an acoustic signal and an optical sensor configured to receive an optical sensor, such as disclosed in U.S. Patent Publications US2022 / 0365036, US2023 / 0097639; US2022 / 0350022 and US2023 / 0148869, each of which is incorporated herein by reference. One or more array elements of a first type (e.g., AEG transducers) may be used to form a first image. In parallel, one or more array elements of a second type (e.g., optical sensors) are used to detect acoustic echoes that may be used to form a second image. The second image generated by the highly sensitive, broadband optical sensor may be used alone or combined with the first image to form a further improved image. Due to the high sensitivity and wide bandwidth of the optical sensor, the image produced by the optical sensor may have improved spatial resolution, improved penetration depth, improved signal-to-noise ratio (SNR), improved tissue harmonic imaging, and / or improved Doppler sensitivity.

[0064] The acoustic transducer 221 can be a component of a medical device system configured to be deployed in vivo within a medium in which a diagnostic or therapeutic procedure is being or will be performed. The acoustic transducer 221 can include an intracavitary or intracavitary transducer located on a catheter, cannula, etc., or can be an intraoperative transducer that allows transducer positioning during minimally invasive surgery, such as on a laparoscopic tool, positioned on the end of a robotic arm, or held by a surgeon, assistant, or any other medical personnel for selective positioning. In an embodiment, the acoustic transducer 221 can be placed on the same medical device as the medical device distal end 231, such as together with the fiber optic sensor 101. In an embodiment, the acoustic transducer 221 can be placed on one or more devices separate from the device at the medical device distal end 231.

[0065] In-vivo transducer 221 can be positioned on catheter / endoscope / cannula, and transmits sound waves that can penetrate the region of interest in the medium outward, and can be called forward-looking probe, as known in the art. Alternatively, acoustic transducer 221 can emit sound waves to the side. For example, transducer 221 can be part of a side-emitting phased array used in IVUS applications. In another example, transducer 221 can be used in a guide catheter with two side-by-side lumens, one lumen captures the guidewire, and the other working lumen does not extend distally like the guidewire lumen. In addition, transducer 221 can transmit sound waves radially. For example, transducer 221 can be included in an echo endoscope with radial (or fan-shaped), linear, curved (convex array), trapezoidal or any other image format used in ultrasound imaging. And linear (convex array) acoustic mode. A radial echo endoscope can provide a circumferential view at right angles to the axis in the echo endoscope, or in other words, provide an image perpendicular to the insertion tube. Different ultrasound frequencies can be used to provide ultrasound imaging of distal and proximal structures. A radial echoendoscope can provide a 360-degree image of the anatomical structure, which can be used for screening but may be limited to therapeutic applications, such as obtaining tissue samples. Curvilinear, linear, or other appropriate arrays can be used for therapeutic applications, such as tissue sample collection, cyst drainage, biopsy of lesions / lymph nodes, and injections for pain management. In an embodiment, the transducer 221 can be incorporated into a curved echoendoscope that visualizes within a range dependent on the radius of the curve and allows real-time insertion of a needle / therapeutic device. In such embodiments, the ultrasound view can be in the same line or plane as the axis of the mirror. In other embodiments, the transducer 221 can be incorporated into a lateral array and provide an image in a plane perpendicular to the axis of the mirror.

[0066] In other procedures, a removable intraoperative transducer may be positioned on the end of a robotic arm or other tool (e.g., bkMedical Rob12C4), or simply held by a medical professional during surgery. Additionally, certain cannulas and endoscopes may have a forward-firing transducer 221 for insonifying the area in front of the cannula, catheter, or scope, such as a craniotomy transducer.

[0067] A typical off-body transducer 221 or probe 245 may be positioned on the skin surface of a patient, such as is typically used for general imaging or for specific procedures such as needle guidance, needle positioning, or needle placement.

[0068] The processing unit 209 is configured to use the information signal received by the fiber optic sensor 101 from the acoustic probe 245 or the acoustic transducer 221 (and any other acoustic signal generator that can be connected or communicated with the photoacoustic sensor system 200) to sense, track and monitor the distal end 231 of the medical device and generate an ultrasonic image of the anatomical structure in the surgical area. In an embodiment, the fiber optic sensor 101 or the sensor array 201 is used to receive / detect the acoustic signal generated by the acoustic probe 245 and / or the acoustic transducer 221, as well as the scattered signal and tissue harmonics. The imaging of the medium can be achieved by the processing unit 209 based on the difference between the acoustic signal output or transmitted by the acoustic probe 245 and / or the acoustic transducer 221 and the corresponding acoustic signal received and / or detected by the acoustic probe 245 and / or the acoustic transducer 221 and the fiber optic sensor 101. The detected signal may include the detected scattered signal and tissue harmonics. The portion of the medium through which the acoustic signal generated by the acoustic probe 245 and / or the acoustic transducer 221 travels can be imaged based on the detected acoustic signal.

[0069] The fiber optic sensor 101 (or sensor array 201) receives acoustic signals transmitted from the acoustic probe 245 and / or the acoustic transducer 221. Based on the signals received from the fiber optic sensor 101, the position of the fiber optic sensor 101 (and therefore the position of the distal end 231 of the medical device) can be calculated by triangulation (e.g., based on receiving one or more acoustic signals transmitted from a known source) and / or by coherent image formation. More details can be found in: co-pending U.S. Provisional Application No. 63 / 522,994, entitled “Transponder Tracking and Ultrasound Image Enhancement” and filed on June 23, 2023; and US Application entitled “Transponder Tracking and Ultrasound Image Enhancement”, having Attorney Docket No. 109835-1394978 and filed on October 23, 2023 concurrently with the present application. The position of the fiber optic sensor 101 can be overlaid on the ultrasound image of the anatomical structure to determine the relative position of the fiber optic sensor 101 relative to the known position of the acoustic probe 245 and / or the acoustic transducer 221. In addition, the ultrasound image of the surrounding anatomical structure can be coherently reconstructed based on the combination of acoustic signals received by the fiber optic sensor 101 and received by one or more of the acoustic probe 245 and / or the acoustic transducer 221. Such a combination can produce better image quality than an image formed using the acoustic probe 245 and / or the acoustic transducer 221 alone.

[0070] In an embodiment of tracking, sensing and monitoring the distal end 231 of a medical device, the photoacoustic sensor system 200 may include a plurality of acoustic probes 245 that are fixed in place or have their positions tracked. For example, tracking, sensing, determining and monitoring the position and movement of the distal end 231 of the medical device may be achieved by identifying the timing and / or direction differences between the plurality of acoustic signals detected by the optical fiber sensor 101 and the acoustic transducer 221.

[0071] It should be understood that, as an example, Figure 2 The configuration of the photoacoustic sensor system 200 shown. Different configurations may be used without departing from the scope of the present disclosure. For example, different arrangements of optical devices 202A / B / C / D, different numbers and arrangements of optical fiber sensors 101 and optical fiber sensor arrays 201 may be used. In an embodiment, the light source control unit 207 and the acoustic control unit 222 may be incorporated into or integrated into the processing system 250. Additional combinations of components of the photoacoustic sensor system 200 may be selected as desired to achieve the functions described herein.

[0072] Figure 3A A sensor fiber including a fiber optic sensor and associated optical fibers is shown. Figure 3AThe device shown may include a sensor optical fiber 301. The sensor optical fiber 301 may be an optical fiber configured with an optical fiber sensor disposed on its end. The sensor optical fiber 301 includes an optical waveguide 311 including a core 312 and a cladding structure 313. The optical waveguide 311 is configured to transmit or carry light therein, for example, within the core 312. The core 312 is surrounded and protected by the cladding structure 313. The optical waveguide 311 may be substantially cylindrical along its length, and / or may have another suitable shape. The core 312 may be substantially in the center of the cladding structure 313. In an embodiment, the optical waveguide 311 may be an optical fiber and may include any material common to optical fibers. For example, the core 312 may include silica glass, a polymer, or other suitable material. For example, the material of the cladding structure 313 may be selected to respond to changes in pressure or strain caused by ultrasound. The pressure or strain caused by ultrasound will introduce deformation or refractive index changes, resulting in changes in the optical signal passing through the optical fiber. For example, when used as an ultrasound sensor, the greater the change, the higher the sensitivity and the better the detection limit. The cladding material may have at least one material property associated therewith, wherein the at least one material property may be a refractive index (RI) lower than the refractive index of the core 312. Material properties, such as Young's modulus and photoelastic coefficient of the core, cladding material, and encapsulation structure, which may be the same or different materials, may be customized depending on the application. A smaller Young's modulus and a larger photoelastic coefficient may be preferred for improving ultrasonic sensitivity and acoustic responsiveness. As used herein, a material that is sensitive or responsive to an acoustic signal may refer to, for example, a material having a relatively small Young's modulus (E), a relatively high photoelastic coefficient, and / or a relatively large refractive index (n) compared to a silica material. As used herein, a relatively small Young's modulus may refer to a Young's modulus less than 3.0 GPa, less than 2.0 GPa, less than 1.2 GPa, or within a range between 1.2 and 0.8 GPa. A relatively high photoelastic coefficient C (i.e., |C1-C2|) may refer to a Young's modulus greater than C=2*10 -121 / Pa photoelastic coefficient value. A relatively large refractive index can refer to a refractive index greater than approximately 1.46 for an optical signal in the range of approximately 300nm-2000nm. Such materials can be selected to increase, improve or optimize the ability of the optical structures discussed herein to detect acoustic signals. Because the optical structures described herein are configured to detect acoustic signals (e.g., ultrasonic signals), the materials from which they are constructed can be selected to maximize or increase the sensitivity of the optical properties of the structure to the incident acoustic signal. For example, a material with a lower Young's modulus requires less stress to deform. In some applications, increased deformation may be undesirable. However, increased deformation in response to an incident acoustic signal can amplify or increase detectable changes in an optical signal through an optical structure that undergoes a larger deformation. Similarly, an increase in the photoelastic effect is desirable in the optical structures described herein, but may be undesirable in different structures configured for different purposes.

[0073] It should be understood that the core 312 can be any suitable type of core, such as those made of silica, silicon, optically transparent polymers, etc. As a non-limiting example, if the core 312 is made of silica (SiO2), the cladding material can be MY-133, a low refractive index optical coating manufactured by MY Polymers Ltd. of Israel, or BIO-133, a low refractive index optical coating also manufactured by MY Polymers Ltd. of Israel. As another non-limiting example, if the core is silicon, which has a higher RI than silica, the cladding structure 313 can be polyvinylidene fluoride (PVDF), polystyrene (PS), parylene, benzocyclobutene (BCB), MY-133, or BIO-133.

[0074] The optical waveguide 311 can be configured for single-mode (SM) transmission or multi-mode (MM) transmission, depending on the form factor and laser and sensor wavelength tuning requirements, as the size of the SM fiber will be smaller. For example, a single-mode fiber configured to operate in the 1550nm band may have a cladding structure diameter of 50um and a core D=>4.2um. Such an optical fiber may be a polarization-maintaining fiber. A multi-mode optical fiber configured to operate in the 1550nm band may have a core D=50um-60.5um and a cladding diameter of 125um. In an embodiment, a polymer optical fiber (e.g., PMMA, polystyrene) may be used. Such an optical fiber may have a larger diameter and a larger minimum bending radius than a typical glass optical fiber. In other embodiments, a photonic crystal fiber (having a hollow structure / periodic pattern) may be used.

[0075] Disposed at the end of the sensor optical fiber 301 is an optical resonator structure 321. The optical resonator structure 321 is coupled to the end of the optical waveguide 311 and may include an optical resonator, such as a Fabry-Perot (FP) resonator, a whispering gallery mode resonator, a microring, a microtoroid, a spiral resonator, or a photonic crystal resonator integrated therein. In addition to the optical resonator, the optical resonator structure 321 and other optical resonator structures described herein may also include additional structures and components configured to facilitate the function of the optical resonator, as described below. The optical resonator is configured to receive a first optical signal (e.g., light) supplied to it via an optical waveguide and return a second optical signal along the optical waveguide. The second optical signal may correspond to and represent an acoustic signal incident to the optical resonator structure 321. As discussed above, the incident acoustic signal may cause physical deformation and / or material property changes of the optical resonator structure 321. Thus, the optical signal provided by the optical resonator structure along the optical waveguide 311 may be altered by, affected by, or otherwise indicative of or representative of the acoustic signal, and may therefore be used to characterize the incident acoustic signal.

[0076] The sensor optical fiber 301 may further include an encapsulation structure 314, which may include, for example, an outer coating, a shield, a protective outer layer, and / or an optical fiber jacket. The encapsulation structure 314 is configured with a first portion 314A surrounding the optical waveguide 311 and a second portion 314B at least partially surrounding the optical resonator structure 321. The encapsulation structure 314 may include a polymer, such as parylene, MY-133, BIO-133, or other suitable polymers that are sensitive or responsive to acoustic signals, as discussed above. The acoustic impedance of the encapsulation structure 314 may be selected to match the impedance of the optical resonator structure 321 in order to enhance the detection sensitivity of the acoustic signal. As used herein, "matching impedance" may refer to selecting materials and / or structures with matched acoustic impedances, as is generally known to those skilled in the art of medical ultrasound, where acoustic impedances that are within 20% of each other provide an acceptable match. A closer match in acoustic impedance results in better transmission of the acoustic signal (e.g., a smaller portion of the acoustic signal is reflected), resulting in higher sensitivity. In an embodiment, the first portion 314A surrounding the optical waveguide 311 and the second portion 314B at least partially surrounding the optical resonator structure 321 may include different materials selected for different purposes. For example, the first portion 314A may include an acoustically transparent material, for example, having an acoustic impedance selected to increase matching and thereby minimize reflections of acoustic signals. The second portion 314B may include an acoustically responsive / sensitive material, as discussed above, to increase the response to incident acoustic signals in the region of the optical resonator structure 321. Unless otherwise explicitly stated, all encapsulation structures discussed herein may include properties similar to those of the encapsulation structure 314, including first and second portions including different materials selected for different purposes.

[0077] The optical resonator structure 321 is disposed at the end of the optical waveguide 311 and may therefore be referred to as a fiber end sensor. The cladding structure 313 may have a first diameter and the optical resonator structure 321 may have a second diameter. The first diameter and the second diameter may or may not be substantially the same. Depending on the application, it may be advantageous to have the optical fibers have substantially the same dimensions or to have the sensor be significantly larger than the optical fibers, such as a bulb-like structure that may or may not be asymmetric. The increased size may further enhance the acoustically sensitive surface area of ​​the sensor, thereby increasing the overall sensitivity. As discussed above, given that certain medical applications require a small form factor, the sensor fiber 301 may be compact, in some examples, with the first diameter and / or the second diameter being less than 200 microns, less than 175 microns, less than 150 microns, less than 130 microns, less than 100 microns, or less than 85 microns.

[0078] Figure 3B A sensor fiber including an optical waveguide and an optical resonator structure having a Fabry-Perot type resonator as an optical sensor is shown. The sensor fiber 351 is an example of the sensor fiber 301 and may include any of the features of the sensor fiber 301 described above. The sensor fiber 351 includes an optical waveguide 371 having a core 352 and a cladding structure 353. The core 352 may have a diameter in a range between 7 and 12 microns, or a diameter of approximately 9 microns. These dimensions are provided as examples only and do not limit the dimensions and diameters covered by the embodiments of the present disclosure. The sensor fiber 351 may include an encapsulation structure 354 encapsulating the optical waveguide 371 and the optical resonator structure 361 disposed at the end of the optical waveguide 371, and the encapsulation structure may, for example, include an outer coating, a protective outer layer and / or an optical fiber jacket. The encapsulation structure 354 may be a multilayer structure, including, for example, an inner layer 355 and an outer layer 356. The inner layer 355 may include a layer of gold or any suitable reflective material for light waves, while the outer layer 356 may include polyparaxylene, MY-133, BIO-133 or other suitable protective layer that may be acoustically transparent. The encapsulation structure 354 may include a first portion 354A that encapsulates or surrounds the optical waveguide 371 and a second portion 354B that encapsulates or surrounds the optical resonator structure 361. The encapsulation structure 354 may have features similar to those of the encapsulation structure 314, including a first portion and a second portion having different materials. The optical resonator structure 361 may be configured with a Fabry-Perot resonator as the optical resonator 362. The optical resonator 362 includes a distal reflective surface 364 and a proximal reflective surface 363 arranged on both sides of the optical cavity 365. The distal reflective surface 364 and the proximal reflective surface 363 may be constructed of any suitable reflective material. As Figure 3BAs shown, the distal reflective surface 364 and the proximal reflective surface 363 are formed by and integral with the inner layer 355 of the encapsulation structure 354 and are therefore formed of gold or other suitable reflective material. Figure 3B As shown in , the distal reflective surface 364 can be curved and the proximal reflective surface 363 can be substantially flat. This arrangement is by way of example only, and the distal and proximal reflective surfaces 364 / 363 can be arranged in different shapes and / or configurations. Figures 4A-4E Some additional examples are provided in . In other embodiments, the distal reflective surface 364 and the proximal reflective surface 363 can be formed of different materials and / or can be a structure separate from the encapsulation structure 354. The optical cavity 365 is disposed between the distal reflective surface 364 and the proximal reflective surface 363. As used herein, the term "optical cavity" refers to a volume occupied by a material that provides minimal attenuation (e.g., having a high Q factor, typically above 1000) to light passing therethrough. The quality (Q) factor is a dimensionless parameter that describes the amount of damping within a resonator. A higher Q factor corresponds to a more sensitive resonator.

[0079] In optics, the Q factor of a resonant cavity is given by:

[0080]

[0081] where f0 is the resonant frequency, E is the energy stored in the cavity, and is the power dissipated. The optical Q factor is equal to the ratio of the resonant frequency to the cavity resonant bandwidth. The average lifetime of a resonant photon in a cavity is proportional to the cavity Q factor. Therefore, a high Q factor indicates low damping and a high lifetime of photons in the cavity.

[0082] The Q factor, as well as any other measure of sensitivity and responsiveness, is ultimately limited by the choice of material used for the core. Conventional Fabry-Perot interferometers may be formed uniformly from a single material, such as silica throughout the structure. For example, while silica has excellent light transmission capabilities, it does not have equally excellent acoustic sensitivity. While many materials are known that have excellent acoustic sensitivity, these materials themselves may not be suitable substitutes for silica, etc., for the core. The present invention employs resonant actuators to exploit acoustic sensitivities found in other materials.

[0083] The optical cavity 365 can be composed of a suitable material, such as a polymer. Polymer materials with high acoustic transmittance, such as MY-133 or BIO-133, can be used to enhance the sensitivity of the optical resonator structure, as discussed above. The optical resonator structure 361 can be configured to detect an acoustic signal. Acoustic signals incident on the optical resonator structure, such as incident on the distal reflective surface 364, the proximal reflective surface 363 and / or the optical cavity 365, can cause these structures to vibrate and / or otherwise physically deform, which may change or affect their optical properties. In addition, due to the photoelastic effect, the material properties of these structures can be changed, and thus further change the optical properties. Therefore, the return optical signal provided by the optical resonator structure 361 to the optical waveguide 371 (for example, in response to the optical signal supplied via the optical waveguide 371) can indicate or represent the acoustic signal incident on the optical resonator structure 361. More specifically, the phase shift of the light in the detected sensor beam indicates the sensed acoustic signal. With a polarization based sensor, a polarization analyzer will interpret the phase shift / delay between the different polarization components in order to generate a signal indicative of the sensed acoustic signal.

[0084] Figure 4A-4E Several variations of optical resonator structures 361 according to embodiments of the invention are shown. Figure 4A An optical resonator structure 361 is shown having a proximal reflective surface 363 and a distal reflective surface 364 that are substantially flat and substantially parallel at either end of a substantially cylindrical optical cavity 365 . Figure 4B An optical resonator structure 361 is shown having a proximal reflective surface 363 that is substantially flat and substantially square relative to the optical waveguide 371 and a distal reflective surface 364 that is concave relative to the optical cavity 365 . Figure 4C An optical resonator structure 361 is shown having a proximal reflective surface 363 that is convex relative to an optical cavity 365 and a distal reflective surface 364 that is concave relative to the optical cavity. Figure 4D An optical resonator structure 361 is shown having a proximal reflective surface 363 that is concave relative to an optical cavity 365 and a distal reflective surface 364 that is substantially flat and substantially square relative to an optical waveguide 371 . Figure 4E An optical resonator structure 361 is shown having a proximal reflective surface 363 and a distal reflective surface 364 that are both concave relative to an optical cavity 365 .

[0085] Figure 5A An optical sensor system for use with a fiber optic sensor according to embodiments herein is shown. Figure 5B An interferometer-based optical sensor according to embodiments herein is shown. Figure 5A The optical sensor system 100B is configured for use with an interferometer-based fiber optic sensor 101B, such as Figure 5B shown.

[0086] The optical fiber sensor 101B may include an optical fiber end sensor having an interferometer-based acoustic sensor. The optical fiber sensor 101B may include a sensor optical fiber 301A having an interferometer-based optical fiber end sensor structure 321A disposed at its end, such as disposed at the end of an optical waveguide 311A. Except as mentioned, the sensor optical fiber 301A may include features and structures consistent with the features and structures of the sensor optical fiber 301. The interferometer-based optical fiber end sensor structure 321A may include, for example, a Mach-Zehnder (MZ) type interferometer. The interferometer-based optical fiber end sensor structure 321A is coupled to the end of the optical waveguide 311A. The interferometer-based optical fiber end sensor structure 321A may include additional structures and components configured to facilitate the function of the interferometer-based optical fiber end sensor, as described below. The interferometer-based optical fiber end sensor is configured to receive a first optical signal (e.g., light) supplied to it via the optical waveguide 311A ​​and return a second optical signal along the optical waveguide 311A. The second optical signal may correspond to and represent an acoustic signal incident to the interferometer-based fiber end sensor structure 321A. The incident acoustic signal may cause the interferometer-based fiber end sensor structure 321A to undergo physical deformation and / or material property changes. Thus, the optical signal provided by the interferometer-based fiber end sensor structure 321A along the optical waveguide 311A ​​may be altered by, affected by, or otherwise indicate or represent the acoustic signal, and may therefore be used to characterize the incident acoustic signal.

[0087] The interferometer-based fiber end sensor structure 321A may include an acoustically responsive polymer portion 317A that includes polyparaxylene or other suitable polymer that is sensitive to acoustic signals. The acoustic impedance of the polymer portion 317A may be selected to match the acoustic impedance of the encapsulation structure of the sensor fiber 301A (e.g., within 1%, 5%, 10%, or 20%) to enhance the sensitivity of the fiber end sensor structure 321A, as described above. The distal reflective surface 364A is disposed at the distal end of the fiber end sensor structure 321A and may be constructed of any suitable material, such as gold. Figure 5B As shown, the distal reflective surface 364A is formed of gold and is integral with the polymer portion 317A.

[0088] The fiber end sensor structure 321A is disposed at the end of the optical waveguide 311A, and thus may be referred to as a fiber end sensor. The optical waveguide 311A ​​may have a first diameter, and the fiber end sensor structure 321A may have a second diameter. The first diameter and the second diameter may be substantially the same, and / or may have a ratio in a range between 1.05 and 0.95, a ratio in a range between 1.02 and 0.98, or a ratio in a range between 1.01 and 0.99. As discussed above, the sensor fiber 301A may be compact, for example, with the first diameter and / or the second diameter being less than 200 microns, less than 175 microns, less than 150 microns, less than 130 microns, less than 100 microns, or less than 85 microns.

[0089] The optical sensor system 100B is configured for use with an interferometer-based fiber optic sensor 101B. The optical sensor system 100B may include a light source 104, such as a laser, a light receiving device 103, such as a photodetector, one or more optical waveguides 105, an optical circulator 102, one or more frequency shifters 106, and one or more couplers 107. In operation, the light source 104 supplies an initial optical signal 111A to the fiber optic sensor 101 via the optical waveguide 105, through the coupler / decoupler 107A, and through the optical circulator 102. The supplied initial optical signal 111A returns along the optical waveguide 105 through the fiber optic sensor 101. The returned optical signal 112 travels via the optical waveguide 105 through the optical circulator 102 and the coupler / decoupler 107B, and is received at the light receiving device 103. The coupler / decoupler 107A is used to direct a portion of the initial optical signal 111A as a reference optical signal 111B through the frequency shifter 106 to the coupler / decoupler 107B, where it can be combined with the returned optical signal 112 for detection and comparison at the optical receiving device 103. As discussed above, the acoustic signal incident on the optical fiber sensor 101 changes the optical properties (including physical structure and optical material properties) of the optical fiber sensor 101. Such optical property changes can be measured based on changes in the returned optical signal 112 compared to the reference optical signal 111B.

[0090] Figure 5C and 5DAn embodiment of an optical fiber sensor is shown, which includes an optical fiber end face configured to provide or enhance acoustic detection capabilities. The optical fiber sensor 101C and the optical fiber sensor 101D each include at least an optical waveguide 311, a core 312, a cladding structure 313, and an encapsulation structure 314. The optical fiber sensor 101C includes an optical sensor structure 329C, which includes an acoustically responsive polymer portion 397 and a face substrate 398A located at its distal end. The optical fiber sensor 101D includes an optical sensor structure 329D, which includes an acoustically responsive polymer portion 397, a face substrate 398B disposed between the polymer portion 397 and the core 312 and the cladding structure 313, and a distal end reflective surface 394 disposed at the distal end of the polymer portion 397.

[0091] In the optical fiber sensor 101C, the face substrate 398A is disposed at the distal end of the optical fiber sensor 101C. The optical sensor structure 329C is formed by a polymer portion 397 and a face substrate 398A. The face substrate 398A includes one or more face structures 399A, as shown in the cross-sectional view. The face structure 399A may include: an acoustically responsive microstructure, such as a metasurface containing a pattern of small elements, which are arranged to change the wavefront shape of the acoustic signal and maximize the detection of the acoustic signal; an acoustically responsive low-dimensional material having an optomechanical feature selected to optimize the acoustic response, such as a feature that is more easily deformed when receiving an acoustic signal and exhibits a greater material response to the acoustic signal; and a plasma structure, which is patterned to amplify light-matter interactions, as described herein. The plasma structure can locally amplify the incident light due to its plasma resonance. The face structure 399A operates as an optical sensor as described herein. During operation, the supplied optical signal 1111 is reflected from the face substrate 398A and returned to the system as a return optical signal 1121. Because the face structure 399A is acoustically responsive, the returned optical signal 1121 is modified by the changes in the face structure 399A caused by the incident acoustic signal. In an embodiment, the plasmon resonance induced in the plasmonic metasurface acting as the face structure 399A or the Mie resonance induced in the dielectric metasurface acting as the face structure 399A can be altered (e.g., shifted) by the incident acoustic signal, making the modification of the returned optical signal 1121 detectable. The returned optical signal 1121 can then be interpreted by any of the systems described herein.

[0092] In the optical fiber sensor 101D, the face substrate 398B is disposed between the polymer portion 397 and the core 312 and the cladding structure 313. The optical sensor structure 329D is formed by the polymer portion 397, the face substrate 398B and the distal reflective surface 394. The face substrate 398B includes one or more face structures 399B, as shown in the cross-sectional view. The face structure 399B may include acoustically responsive microstructures, similar to those described above with respect to the face structure 399A. The face structure 399B is used to enhance, improve or otherwise modify the acoustic response of the optical sensor structure 329D. During operation, the supplied optical signal 1111 is reflected from the distal reflective surface 394 and returned to the system as a returned optical signal 1121. The polymer portion 397 and the distal reflective surface 394 are acoustically responsive, and the returned optical signal 1121 is modified according to the acoustic signal incident on these structures. Because the face structure 399B is acoustically responsive and both the supplied optical signal 1111 and the returned optical signal 1121 pass through the face substrate 398B, the returned optical signal 1121 is further modified by the changes in the face structure 399B caused by the incident acoustic signal. In an embodiment, the face structure 399B can be designed and / or selected to optimize coupling (e.g., reduce signal loss) and / or achieve critical coupling (e.g., eliminate signal loss) for the optical sensor structure 329D. The improved coupling in the optical sensor structure 329D is used to increase the amplitude of the optical signal in response to the incident acoustic signal. Therefore, the returned optical signal 1121 can exhibit a higher signal-to-noise ratio. In addition, the incident acoustic signal that deforms the face structure 399B can also be used to change the degree to which the face structure 399B modifies the coupling in the optical sensor structure 329D, thereby providing another aspect of the returned optical signal 1121 modified by the incident acoustic signal for interpretation. Then, the returned optical signal 1121 can be interpreted by any system described herein. Thus, the face substrate 399B may be used to enhance, improve, or otherwise modify the acoustic response of the optical sensor structure 329D.

[0093] Surface structures 399A and 399B Figure 5C and 5D 101C and 101D. Such a planar substrate is not limited to use with optical sensors having the interferometer-based structure and operation of fiber optic sensors 101C and 101D, and may be incorporated into any of the fiber optic sensors discussed herein.

[0094] Figure 5E shows an example of a plasmonic metasurface, and Fig. 5F An example of a dielectric metasurface is shown in FIG. Figure 5EAs shown in , the optical fiber 500 may include a plasma metasurface 511, which is disposed at the end of an optical waveguide 502 having a core 501. The plasma metasurface 511 can be disposed in a region defined by the core 501 on the end of the optical fiber 500. As shown, for example, the plasma metasurface 511 can be disposed in a square pattern, or can also be disposed in any other suitable pattern. The plasma metasurface 511 can exhibit plasma resonance when hit by an optical signal from the core 501. The deformation caused by the incident acoustic signal changes the plasma resonance and allows detection and decoding of the acoustic signal, as discussed herein. The plasma metasurface 511 may include various metals, and in particular may include precious metals, such as gold. In addition, the plasma metasurface 511 may be a thin film surface having a height of less than 50 microns, less than 40 microns, less than 30 microns, less than 20 microns, or less than 10 microns. In other embodiments, the plasma metasurface 511 may be a low-dimensional or two-dimensional surface having a height of less than 1 micron. In the lateral dimension, the features of the plasmonic metasurface 511 can be small, having a lateral dimension D (e.g., width and / or length) that is less than the wavelength of the optical signal used by the sensor (e.g., less than 600 nanometers, less than 400 nanometers, less than 200 nanometers, etc.). The lateral dimension of the features of the plasmonic metasurface 511 can also refer to the spacing between the features. Fig. 5F 5 shows a dielectric metasurface 512, which can be arranged in a similar manner in the region of the core 501 at the end of the optical waveguide 502 of the optical fiber 550. The dielectric metasurface 512 can be arranged in a strip or rectangle, such as Fig. 5F , or arranged in any other suitable shape. The dielectric metasurface 512 can be configured to exhibit Mie resonances when struck by an optical signal. The Mie resonances can be altered by incident acoustic signals, thereby permitting detection and decoding of acoustic signals. In embodiments, the dielectric metasurface 512 can include dielectric materials such as silicon, titanium oxide, etc. In embodiments, the dielectric metasurface 512 can be dimensioned in a manner similar to the plasma metasurface 512, as discussed above.

[0095] Fig. 6A An optical sensor system for use with a fiber optic sensor according to embodiments herein is shown. Figure 6BA polarization-based optical sensor according to an embodiment herein is shown. An optical sensor system 100B is configured for use with a polarization-based optical fiber sensor 101C. The optical fiber sensor 101C may include an optical fiber end sensor having a polarization-based acoustic sensor. The optical fiber sensor 101C may include a sensor optical fiber 301B having a polarization-based optical fiber end sensor structure 321B disposed at its end, for example, at the end of an optical waveguide 311B. In other embodiments, as discussed below, the polarization-based optical fiber end sensor structure 321B may be disposed at any position along the sensor optical fiber 301B. In addition to what is mentioned, the sensor optical fiber 301B may include features and structures consistent with the features and structures of the sensor optical fiber 301. The sensor optical fiber 301B includes an encapsulation structure 314C, which may include, for example, an outer coating, a protective outer layer, and / or an optical fiber jacket. The encapsulation structure 314C may include a material selected to have a relatively high acoustic impedance mismatch with the cladding structure of the sensor optical fiber 301B. Thus, the incident acoustic signal may be reflected at the location where the sensor optical fiber 301B is covered by the encapsulation structure 314C. The polarization-based optical fiber end sensor structure 321B may be exposed through the window 320B defined by the lack of the encapsulation structure 314C, and may include a polymer portion 317B including an acoustically responsive polymer and a distal reflective surface 364B configured to reflect the initial optical signal 111 as a reflected optical signal 112. The polarization-based optical fiber end sensor structure 321B is configured to receive a first optical signal (e.g., light) supplied to it via the optical waveguide 311B and return a second optical signal along the optical waveguide 311B. The second optical signal may correspond to and represent the acoustic signal incident to the polarization-based optical fiber end sensor structure 321B. The incident acoustic signal may cause the polarization-based optical fiber end sensor structure 321B to undergo physical deformation and / or material property changes. Thus, the optical signal provided by the polarization-based fiber end sensor structure 321B along the optical waveguide 311B can be altered by, affected by, or otherwise indicate or represent the acoustic signal, and can therefore be used to characterize the incident acoustic signal. In the polarization-based fiber end sensor structure 321B, the incident acoustic signal induces stress in the polymer portion 317B, which causes one or more of birefringence and rotation of the polarization of the light passing through the polymer portion 317B, thereby changing the polarization of the light carried by the optical waveguide 311B, which can be detected and analyzed by the optical sensor system 100B discussed below.

[0096] The optical sensor system 100B includes a light source 104, such as a laser, a light receiving device 103, such as a photodetector, one or more optical waveguides 105, an optical circulator 102, and an optical fiber sensor 101B. In operation, the light source 104 supplies an initial optical signal 111 to the optical fiber sensor 101B via the optical waveguide 105 and through the optical circulator 102. The supplied initial optical signal 111 returns along the optical waveguide 105 through the optical fiber sensor 101B. The returned optical signal 112 travels through the optical circulator 102 via the optical waveguide 105, passes through the polarization analyzer 108, and is received at the optical receiving device 103. The use of the polarization analyzer 108 allows the polarization difference between the initial optical signal 111 and the returned optical signal 112 to be determined. As discussed above, the acoustic signal incident on the optical fiber sensor 101B changes the optical characteristics (including the physical structure and optical material properties) of the optical fiber sensor 101B and causes a change in the polarization of the returned optical signal 112. Such a polarization change may be measured from the difference between the returned optical signal 112 and the initial optical signal 111 as determined by the photodetector.

[0097] In an embodiment, the angular sensitivity of the polarization-based fiber end sensor structure 321B may be affected by differences in the polarization of the initial optical signal 111. Depending on the polarization of the initial optical signal 111, the angle of the incident acoustic signal to which the polarization-based fiber end sensor structure 321B is most sensitive may be altered, such as Figure 6C Thus, in an embodiment, a control system associated with the optical sensor system 100B can be configured to adjust or optimize the polarization of the initial optical signal 111, for example, from input polarization state 1 to input polarization state 2 to increase acoustic sensitivity. These polarization states are provided as examples only and can be changed or configured according to operational needs, as discussed below. Figure 6CThe directions in which input polarization state 1 and input polarization state 2 are most sensitive to the incoming acoustic signal are shown. The solid arrow corresponds to the direction in which input polarization state 1 is most sensitive, and the dashed arrow corresponds to input polarization state 2. Therefore, the lobes of polarization states provide the highest acoustic sensitivity. Therefore, the input polarization state can be selected and implemented to be aligned with the expected direction of the acoustic signal or the direction in which the acoustic sensitivity requirement is the highest. This can enable the optical sensor system 100B to optimize the performance of the fiber end sensor structure 321B according to the incoming direction of the acoustic signal. The angular sensitivity of the fiber end sensor structure 321B based on polarization does not depend on the structure of the fiber end sensor structure 321B. In an embodiment, a polarization-maintaining fiber can be used. After the polarization state is selected and implemented, it is maintained by the optical signal. In an embodiment, an adjustable fiber component can be used to provide an adjustable polarization state. In an embodiment, the polarization state can be adjusted during use to take into account changes in conditions (e.g., movement of the acoustic transducer 221 generating the acoustic signal and / or movement, rotation, etc. of the fiber end sensor structure 321B). Other benefits of the polarization-based fiber end sensor structure 321B may include a simplified sensor structure and no wavelength locking requirements.

[0098] Fig.6D Another embodiment of an optical fiber-based optical sensor according to an embodiment of the present invention is shown. The sensor fiber 301C may be an optical fiber configured in a manner similar to the sensor fiber 301, including an optical waveguide including a core and a cladding structure, as described herein. The sensor fiber 301C may have a fiber end sensor structure 321C disposed on its end. The fiber end sensor structure 321C may include any of the fiber end sensor structures discussed herein, including an optical resonator structure, an interferometer structure, an acoustically responsive fiber end face structure, and a polarization-based structure. The sensor fiber 301C may further include an encapsulation structure 314C configured to reflect an incident acoustic signal and a window 320C representing a gap or exposed area without the encapsulation structure 314C. The window 320C may expose a polarization-based optical sensor structure 322C, for example with respect to Figure 6BAs discussed. In an embodiment, the polarization-based optical sensor structure 322C is formed by the cladding structure and core of the optical fiber and is a part of the optical fiber. That is, the polarization-based optical sensor structure 322C can be defined by exposure to an incident acoustic signal generated by the lack of an acoustic shield at the window 320C, rather than any additional structure within the optical fiber. The sensor optical fiber 301C may include any number of windows 320C and polarization-based optical sensor structures 322C disposed along its length. Therefore, the sensor optical fiber 301C may include a plurality of optical-based acoustic sensor structures, including both the optical fiber end sensor structure 321C and the polarization-based optical sensor structure 322C configured for the middle optical fiber position. In other embodiments, the window 320C may have sufficient dimensions along the length of the optical fiber so that it will operate as a line sensor rather than a point sensor, as will be discussed in more detail below. The line sensor may be a straight line sensor or a curved receiver. In other embodiments, the sensor optical fiber 301C may be configured with one or more polarization-based optical sensor structures 322C disposed along its length, but does not include any optical fiber end sensor structure 321C.

[0099] Each of the fiber end sensor structure 321C and the polarization-based optical sensor structure 322C can be used to facilitate both imaging and tracking, as described herein. In an embodiment, for example, the polarization-based optical sensor 322C can be configured in size / shape to facilitate imaging, tracking, or both. For example, a longer polarization-based optical sensor structure 322C can act as a line sensor to increase image quality, and the line can be straight or curved. In another example, multiple polarization-based optical sensor structures 322C can be used to facilitate tracking methods (e.g., multiple sensors along a device can help with orientation determination).

[0100] In some embodiments, the polarization window portion may also act as a fiber optic sensor for detecting scattered acoustic signals and / or tissue harmonics. When the fiber optic sensor is positioned within the imaging region of interest, it may receive weak harmonics or scattered acoustic signals that cannot propagate very far. The optical fiber may transmit an optical signal corresponding to the received acoustic signal to a system processor (e.g., processing unit 209). The system processor may use the received optical signal to reconstruct an ultrasound image of the anatomical structure surrounding the sensor by a delay-addition beamforming method or other suitable image reconstruction method, as discussed in more detail in the corresponding U.S. Provisional Application No. 63 / 522,994, entitled “Transponder Tracking and Ultrasound Image Enhancement” and filed on June 23, 2023, and the US Application entitled “Transponder Tracking and Ultrasound Image Enhancement”, having attorney case number 109835-1394978 and filed in parallel on October 23, 2023. With this data, the system processor can generate an image of better quality than an image generated based solely on pulses transmitted and received by an acoustic probe. In an embodiment, the system processor can construct an image based solely on optical signals received from one or more fiber optic sensors. In an embodiment, the optical signals received from one or more fiber optic sensors can be used in conjunction with acoustic signals received by a conventional ultrasound probe.

[0101] This principle is Fig. 6E As shown in more detail in Fig. 6E As shown, an acoustic probe 601 can be used to transmit an acoustic signal 620 into an area of ​​interest. For imaging purposes, the acoustic probe 601 can be used as a conventional acoustic probe to detect reflections of the acoustic signal 620. These images can be enhanced by additional information obtained by one or more fiber optic sensors. The fiber optic sensor 612 of the sensor fiber 602 can correspond to any of the fiber end optical sensor structures discussed herein and can receive the acoustic signal 622. The acoustic signal 622 can be generated by reflection, scattering, and / or tissue harmonics. As shown in FIG. Fig. 6E As shown, acoustic signal 622 is generated from point 621 within the region of interest. Fiber optic sensor 612 can be configured to receive acoustic signal 622 from any direction, as discussed herein. Sensor fiber 603 can be configured to act as a polarization-based optical sensor, as discussed herein, and can receive acoustic signal 622 from directions lateral to the axis of sensor fiber 603. As used herein, "lateral" refers to all directions that are not parallel to the axis of sensor fiber 603. Fig. 6EAs shown, the acoustic signal 622 can be received by the sensor optical fiber 602 from any direction at any exposed portion along its length, such as with respect to Fig.6D In addition, as discussed in Figure 6C As discussed and Figure 6C As shown, the polarization of the sensor optical fiber 602 may be selected or adjusted to accommodate an expected or desired radial angle of incidence of the acoustic signal 622 . Fig. 6E Further shown is a sensor fiber 604 that can be bent within the imaging region of interest. Similar to the sensor fiber 603, the sensor fiber 604 can detect incident acoustic signals 622 that are lateral to, substantially lateral to, or from any direction along the axis of the sensor fiber 604. When the sensor fiber 604 is positioned within a medium (e.g., within a human body during a medical procedure), detecting lateral signals at multiple points along the length of the sensor fiber 604 can enhance the ability to track and / or locate the sensor fiber 604. For example, as Fig. 6E As shown in (b) of FIG. 6 , multiple signals incident along the length of the sensor fiber 604 can enhance the ability to determine the position of different portions of the sensor fiber 604 along its length and thus identify the position of the entire sensor fiber 604 rather than just the tip region. For example, Fig. 6E As shown in (c), multiple signals incident along the length of the sensor optical fiber 604 can enhance the ability to determine the position of different portions of the sensor optical fiber 604 with greater accuracy and thereby identify the curvature of the sensor optical fiber 604.

[0102] Fig. 6F and 6G An optical sensor system for use with a fiber optic sensor according to embodiments herein is shown. Figure 6G An optical resonator-based optical sensor configured for use with a multi-core optical fiber according to embodiments herein is shown. Fig. 6F The optical sensor system 100D is configured for use with a multi-core fiber optic sensor 101D based on an optical resonator, such as Figure 6G In other embodiments, other optical sensors discussed herein, including, for example, interferometer-based sensors, may be employed in multi-core fiber-based systems.

[0103] The optical fiber sensor 101D may include an optical fiber end sensor having an optical resonator-based acoustic sensor, as described herein. The optical fiber sensor 101D may include a sensor fiber 301D having an optical resonator-based optical fiber end sensor structure 321D disposed at its end, for example, at the end of an optical waveguide 311D. Except as noted, the sensor fiber 301D may include features and structures consistent with the features and structures of the sensor fibers 301 and 351. The optical resonator-based optical fiber end sensor structure 321D is coupled to the end of the optical waveguide 311D. The optical resonator-based optical fiber end sensor structure 321D may include an optical resonator sensor 322D, and may also include additional structures and components configured to facilitate the functionality of the optical resonator sensor 322D, as described below. In Figure 6G The optical resonator-based fiber end sensor 322D schematically shown in the figure can be waveguide coupled so that it is configured to receive an initial optical signal 111 (e.g., light) supplied to it via a first optical core 313D of the sensor optical fiber 301D, and provide a return optical signal 112 back along a second optical core 312D of the sensor optical fiber 301D. The second optical signal can correspond to and represent an acoustic signal incident to the optical resonator-based fiber end sensor structure 321D. The incident acoustic signal can cause the optical resonator-based fiber end sensor structure 321D to undergo physical deformation and / or change in material properties. Therefore, the optical signal provided by the optical resonator-based fiber end sensor structure 321D along the second optical core 312D can be changed by the acoustic signal, affected by the acoustic signal, or otherwise indicate or represent the acoustic signal, and can therefore be used to characterize the incident acoustic signal.

[0104] The optical resonator-based fiber end sensor structure 321D may include an acoustically responsive polymer portion 317D including polyparaxylene or other suitable polymers that are sensitive to acoustic signals. The acoustic impedance of the polymer portion 317D may be selected to match the acoustic impedance of the encapsulation structure or cladding structure 314D of the sensor fiber 301D (e.g., within 1%, 5%, 10%, or 20%) to enhance the sensitivity of the optical resonator-based fiber end sensor structure 321D, as described above.

[0105] The fiber end sensor structure 321D is disposed at the end of the optical waveguide 311D and may therefore be referred to as a fiber end sensor. The encapsulation or cladding structure 314D may have a first diameter and the fiber end sensor structure 321D may have a second diameter. The first diameter and the second diameter may be substantially the same and / or may have a ratio in a range between 1.05 and 0.95, a ratio in a range between 1.02 and 0.98, or a ratio in a range between 1.01 and 0.99. As discussed above, the sensor fiber 301D may be compact, for example, wherein the first diameter and / or the second diameter is less than 200 microns, less than 175 microns, less than 150 microns, less than 130 microns, less than 100 microns, or less than 85 microns. If the fiber diameter is extremely small, increasing the diameter of the fiber sensor end may further enhance the acoustic sensitivity.

[0106] The optical sensor system 100D is configured for use with a resonator-based fiber sensor 101D. The optical sensor system 100D may include a light source 104, such as a laser, a light receiving device 103, such as a photodetector, one or more optical waveguides 105, and a multi-core fiber fan-out coupler 109. In operation, the light source 104 supplies an initial optical signal 111 to the fiber sensor 101D via the optical waveguide 105 and through the multi-core fiber fan-out coupler 109. The supplied initial optical signal 111 travels to the optical resonator-based fiber end sensor structure 321D via the first optical core 313D, where it may be affected by the incident acoustic signal, and then returned by the second optical core 312D as a returned optical signal 112. The returned optical signal 112 travels through the fan-out coupler 109 via the optical waveguide 105 to be received at the light receiving device 103. As discussed above, the acoustic signal incident on the fiber sensor 101D changes the optical characteristics (including physical structure and optical material properties) of the fiber sensor 101D. Such optical property changes can be measured based on the returned optical signal 112 to measure the properties and characteristics of the incident acoustic signal. Fig. 6F In the embodiment of the present invention, for example, it is not necessary to provide the initial optical signal 111 to the optical receiving device 103 to measure the optical characteristic change, because the parameters of the initial optical signal 111 are known to the system.

[0107] The multi-core fiber fan-out coupler 109 is used to couple the single-core optical waveguide 105 to the multi-core optical waveguide 311D. Therefore, the initial optical signal 111 and the returned optical signal 112 can travel in separate optical cores in the multi-core optical waveguide 311D. Compared to the optical sensor system 100B, the use of the multi-core fiber fan-out coupler 109 and the multi-core optical waveguide 311D in the optical sensor system 100D may not require an optical circulator. Such a design may be advantageous for some reasons. For example, compared to an optical circulator, the multi-core fiber fan-out coupler 109 of the optical sensor system 100D may be smaller, lighter and / or cheaper, which may enable greater flexibility when incorporating the optical fiber sensor 101D into a device or equipment. In an embodiment, other suitable optical couplers configured to couple a single-core optical fiber to a multi-core optical fiber may replace the multi-core fiber fan-out coupler 109.

[0108] Figure 6H and 6I An optical sensor system for use with a fiber optic sensor according to embodiments herein is shown. Fig.6I An optical resonator-based optical sensor configured for use with a pair of single-core optical fibers according to embodiments herein is shown. Figure 6H The optical sensor system 100E is configured for use with a dual-fiber optical resonator-based sensor 101E, such as Fig.6I In other embodiments, other optical sensors discussed herein may be employed in dual fiber based systems, including, for example, interferometer based sensors.

[0109] The optical fiber sensor 101E may include an optical fiber end sensor having an optical resonator-based acoustic sensor, as described herein. The optical fiber sensor 101E may include a sensor fiber 301E having an optical resonator-based optical fiber end sensor structure 321D disposed at its end. Except as noted, the sensor fiber 301E may include features and structures consistent with those of the sensor fibers 301 and 351.

[0110] The optical fiber sensor 101E may include a dual optical fiber structure. The optical fiber sensor 101E may include a first optical waveguide 311E having a first optical fiber core 313E and a second optical waveguide 315E having a second optical fiber core 312E. Each of the first optical waveguide 311E and the second optical waveguide 315E may be a separate optical fiber and may each have a separate cladding structure 314E. The first optical waveguide 311E and the second optical waveguide 315E may be coupled together. For example, the first optical waveguide 311E and the second optical waveguide 315E may be coupled via a glue or other adhesive.

[0111] The optical resonator-based fiber end sensor structure 321E is coupled to the ends of both the first optical waveguide 311E and the second optical waveguide 315E. The optical resonator-based fiber end sensor structure 321E may include an optical resonator sensor 322E, as well as additional structures and components configured to facilitate the functionality of the optical resonator sensor 322E, as described below. Fig.6I The optical resonator-based fiber end sensor 322E schematically shown in the figure can be waveguide coupled such that it is configured to receive an initial optical signal 111 (e.g., light) supplied to it via a first optical core 313E of a first optical waveguide 311E, and to provide a returned optical signal 112 back along a second optical core 312E of a second optical waveguide 315E. The returned optical signal 112 can correspond to and represent an acoustic signal incident to the optical resonator-based fiber end sensor structure 321E. The incident acoustic signal can cause the optical resonator-based fiber end sensor structure 321E to undergo physical deformation and / or change in material properties. Therefore, the optical signal provided by the optical resonator-based fiber end sensor structure 321E along the second optical core 312E can be changed by the acoustic signal, affected by the acoustic signal, or otherwise indicate or represent the acoustic signal, and can therefore be used to characterize the incident acoustic signal. Figure 6H In the embodiment of the present invention, for example, it is not necessary to provide the initial optical signal 111 to the optical receiving device 103 to measure the optical characteristic change, because the parameters of the initial optical signal 111 are known to the system.

[0112] The optical resonator-based fiber end sensor structure 321E may include an acoustically responsive polymer portion 317E including polyparaxylene or other suitable polymers that are sensitive to acoustic signals. The acoustic impedance of the polymer portion 317E may be selected to match the acoustic impedance of the encapsulation structure (or cladding structure) of the sensor fiber 301E (e.g., within 1%, 5%, 10%, or 20%) to enhance the sensitivity of the optical resonator-based fiber end sensor structure 321E, as described above.

[0113] The optical sensor system 100E is configured for use with a resonator-based fiber sensor 101E. The optical sensor system 100D may include a light source 104, such as a laser, a light receiving device 103, such as a photodetector, and one or more optical waveguides 105. The one or more optical waveguides 105 may be structurally bound to each other to form a first optical waveguide 311E and a second optical waveguide 315E of the sensor optical fiber 301E, and may be separated to couple with the light source 104 and the light receiving device 103. In an embodiment, a coupler or another device may be used to facilitate this coupling. In operation, the light source 104 supplies an initial optical signal 111 to the fiber sensor 101E via the optical waveguide 105. The supplied initial optical signal 111 travels via the first optical waveguide 311E to the optical resonator-based fiber end sensor structure 321E, where it may be affected by an incident acoustic signal, and then returned by the second optical waveguide 315E as a returned optical signal 112. The returned optical signal 112 travels through the optical waveguide 105 to be received at the optical receiving device 103. As discussed above, the acoustic signal incident on the optical fiber sensor 101E changes the optical characteristics (including physical structure and optical material properties) of the optical fiber sensor 101E. Such optical characteristic changes can be measured based on the returned optical signal 112.

[0114] The dual fiber design of the sensor fiber 301E eliminates the need for a circulator or a multi-core fan-out coupler. Such a design may be advantageous for a number of reasons. For example, eliminating a multi-core fiber fan-out coupler and an optical circulator may provide a smaller, lighter and / or cheaper system, which may enable greater flexibility when incorporating the fiber optic sensor 101E into a device or apparatus.

[0115] Figure 7A-7D Examples of manufacturing techniques that may be used to shape or process the ends of optical waveguides are provided. Fig. 7A A method of CO2 laser machining the end of an optical waveguide to achieve a concave proximal reflective surface, for example to accommodate a proximal reflective surface that is concave relative to an optical cavity, is shown. Figure 7B A method of wet etching the end of an optical waveguide to achieve a concave proximal reflective surface is shown, for example to accommodate a proximal reflective surface that is concave relative to an optical cavity. Figure 7C A method of mechanically polishing the end of an optical waveguide to achieve a concave proximal reflective surface, for example to accommodate a proximal reflective surface that is concave relative to an optical cavity, is shown. Fig.7D A method of CO2 laser machining the end of an optical waveguide to achieve a concave proximal reflective surface, for example to accommodate a proximal reflective surface that is concave relative to an optical cavity, is shown.

[0116] Figure 8A-8D Examples of fabrication techniques that may be used to fabricate optical resonator structures at the ends of optical waveguides are provided. Fig. 8AA micromolding method that can be used to form an optical resonator structure is shown. Figure 8B A dip coating method that can be used to form an optical resonator structure is shown. Figure 8C A conformal coating method that can be used to form an optical resonator structure is shown. Fig.8D A dip coating method that can be used to form an optical resonator structure is shown.

[0117] Fig. 9A A method of thermal tuning applied to a sensor fiber is shown. An interferometer-based fiber sensor (or other optical sensor structure according to embodiments of the present invention) may benefit from a wavelength tuning mechanism to maintain the interferometer-based fiber sensor at an optimal operating point. The optimal operating point may be based on the resonance of the optical sensor structure. In embodiments, the resonant wavelength of the optical sensor structure and the operating wavelength of the laser providing the optical signal may be selected, adjusted or determined together to optimize or maximize the optical reading. The resonant wavelength of the optical sensor structure and the operating wavelength of the laser may be selected, adjusted or determined so that the operating wavelength of the laser matches the slope of the resonance peak of the optical sensor structure. The specific position on the slope of the resonance peak may vary depending on sensor design and application-specific requirements. The specific operating position on the slope of the resonance peak affects the dynamic range and sensitivity of the optical sensor structure. In embodiments, the operating position (e.g., wavelength) may be selected so as to have a response amplitude within the range of 10%-90% of the resonance depth, within the range of 10%-30% of the resonance depth, within the range of 30%-50% of the resonance depth, within the range of 50%-70% of the resonance depth, or within the range of 70%-90% of the resonance depth. Therefore, wavelength tuning according to embodiments of the present invention may include tuning the operating wavelength of a laser or the resonant wavelength of an optical sensor to achieve this.

[0118] The wavelength tuning mechanism according to embodiments of the present invention may include, for example, a heating or tuning laser or an external tuner configured for tuning by applying mechanical stress and / or electrothermal heating. Although tunable lasers in the back-end system can provide tunability, individual tunability (local tuning) at the sensing front end is also desirable because it can enable (1) cheaper lasers without wavelength tunability and (2) scalable sensor arrays with shared lasers. Fig. 9AA method of local tuning using photothermal tuning is shown, which does not require additional wiring. In an embodiment, light from a working laser and a heating laser (at different wavelengths) are guided together by an optical fiber. The working laser wavelength can be selected to optimize sensing performance, and at least one structure on the end of the optical fiber (e.g., an optical resonator structure 321, a portion of the encapsulation structure 314, etc.) is absorptive at the heating wavelength. By tuning the power of the heating laser, the local temperature in the optical resonator structure 321 changes, and thus the temperature-sensitive optical transmittance of the fiber sensor is tuned to better match the wavelength of the working laser. Therefore, the heating laser is operated to adjust the temperature of the optical resonator structure 321 according to the wavelength of the working laser. The heating laser can be continuous wave or pulse width modulated. In an embodiment, the sensor fiber 301C can have a double cladding structure. Any of the sensor fibers 301 / 301A / 301B can incorporate the features of the sensor fiber 301C. The sensor fiber 301C can include an inner cladding structure 313A and an outer cladding structure 313B. If the heating wavelength is longer than the cut-off wavelength of the core, then an outer cladding structure 313B can be introduced, which is optimized for operating light transmission.

[0119] exist Fig. 9B In another local tuning approach shown, an external tuner 902 may be provided in place of the heating laser for tuning the sensor transmission by applying, for example, mechanical stress or electrothermal heating. Fig. 9B A sensor fiber 301 is shown, for example, with an optical resonator structure 321. Any suitable sensor fiber and fiber sensor may be used with an external tuner 902. The external tuner 902 may include, for example, piezoelectric and / or electrothermal elements external to the optical cavity that may be configured to apply pressure (i.e., compression) or heat to the optical resonator structure 321. This may require additional cabling, wires, traces, and / or micro-heater printed flex circuits along the length of the fiber sensor to enable the external tuner. As long as the sensor optical path (within the dashed box 368) in the optical resonator structure 321 is not interrupted, the additional structure will not affect the optical properties of the sensor.

[0120] In another example, the optical resonator structure 361 may have an operating wavelength that is adjusted to be more closely aligned with the wavelength of the light source (e.g., a source laser). When multiple fiber optic sensors are arranged in an array, the ability to individually calibrate and fine-tune each fiber optic sensor within the array provides the potential to drive and synchronize the operation of each sensor in the array. This synchronization can also enable a user to drive multiple (≥2) fiber optic sensors with one source laser and capture signals from multiple sensors simultaneously. Such a feature is advantageous when constructing a sensor array for imaging. In this process, a feedback loop can be used to monitor and adjust heat sources or stresses to fine-tune the operating wavelength of the sensor to ensure that it is aligned with the source laser. The synchronized operation of the sensor array ensures robust data interpretation by capturing multiple data points simultaneously or collaboratively analyzing complex imaging patterns.

[0121] Fig.10 An embodiment of a sensor fiber comprising a multi-core optical waveguide is shown. Sensor fiber 801 may include any or all of the features of sensor fibers 301 and 351, as described above. Sensor fiber 801 may include an optical waveguide 811 and an optical resonator structure 321. Optical waveguide 811 includes a plurality of cores 312 within a cladding structure 313, for example, 2, 3, 4, 5, 6, 7, 8, 9, etc.

[0122] Fig.11A and Fig. 11B A comparison between sensor fibers arranged with forward-pointing optical sensors and side-pointing optical sensors is shown. Considering the environment in which the sensor will be used and the direction of the transmitted acoustic beam is an important consideration when incorporating the sensor into a device. For example, some use cases of the optical sensors disclosed herein may benefit from a forward-pointing arrangement, while other use cases may benefit from a side-pointing arrangement.

[0123] Fig.11A Show according to Figure 3A The sensor fiber 351 shown has a Fabry-Perot resonator acting as an optical resonator as part of an optical resonator structure. The optical resonator structure 361 is arranged in a forward configuration. In the forward configuration, the face or surface of the optical resonator structure 361 configured to receive and detect acoustic signals (in the optical resonator 362, this face can be the distal reflective surface 364 or the proximal reflective surface 363) is arranged so that the acoustic response face or surface is oriented in the same direction as the direction in which the sensor fiber 351 extends. The sensor fiber 351 and the acoustic response surface or face can share an axis.

[0124] Fig. 11BA sensor fiber 1001 is shown with a Fabry-Perot resonator acting as an optical resonator as part of an optical resonator structure 1021, which is arranged to capture incident acoustic signals laterally. The sensor fiber 1001 may include all of the features of the sensor fibers 301, 351, 701, and 801 (even though not shown). The sensor fiber 1001 may include one or more cores 1012, one or more cladding structures 1013, an encapsulation structure 1014, and an optical resonant structure 1021. The optical resonant structure 1021 may include a Fabry-Perot resonator, such as Fig. 11B , and / or any other type of optical resonator discussed herein. The optical resonant structure 1021 may include a distal reflective surface 1064 and a proximal reflective surface 1063 arranged on either side of the optical cavity 1065. In an embodiment, the optical resonant structure 1021 is configured in a sideways configuration. In the sideways configuration, an acoustic response surface or surface of the optical resonator structure 1021 configured to receive and detect acoustic signals (in the optical resonator 362, this surface may be the distal reflective surface 364 or the proximal reflective surface) is arranged so that the acoustic response surface or surface is oriented in the same direction as the direction in which the sensor optical fiber 351 extends. The sensor optical fiber 351 and the acoustic response surface or surface may have an axis that is substantially perpendicular to the axis of the sensor optical fiber 1001. In other embodiments, the angle between the axis of the acoustic response surface or surface and the axis of the sensor optical fiber 1001 may be between 0° and 90°, depending on the desired angle of acoustic sensitivity.

[0125] Fig.12 An embodiment of a sensor fiber providing acoustic detection capability from a direction behind the distal end of the sensor or proximal detection capability according to an embodiment of the present invention is shown. The sensor fibers described herein, such as sensor fiber 301, sensor fiber 351, sensor fiber 701, sensor fiber 801, can be provided with improved proximal detection capability. Fig.12A sensor fiber 351 is shown having an optical resonator structure 361 having a proximal reflective surface 363 and a distal reflective surface 364 arranged to share an axis with an optical waveguide 371. The proximal reflective surface 363 and the distal reflective surface 364 both serve as acoustic response surfaces. To improve rear-view capability, the cladding structure 353 may include a material selected to minimize the acoustic impedance mismatch with the intended medium in which the sensor fiber 351 will be used. By minimizing the acoustic impedance mismatch, the critical angle of the boundary between the sensor fiber 351 and the medium in which it is disposed is increased, thereby enabling the optical resonator structure 361 to receive acoustic signals over a greater range of angles. For example, a sensor fiber 351 intended for use within the human body may include a cladding structure 353 that includes a polymer selected to optimize detection sensitivity by minimizing any acoustic impedance mismatch. In an embodiment, the cladding structure 353 may be selected to have at least one of a Young's modulus (E) less than that of the core 352, a photoelastic coefficient greater than that of the core 352, and a refractive index (n) less than that of the core 352. In an embodiment, the cladding structure 353 may include benzocyclobutene (BCB) or polydimethylsiloxane (PDMS), each of which has a small Young's modulus (E), a high photoelastic coefficient, and a small refractive index (n). Reducing the acoustic impedance mismatch can increase the acoustic signal that passes through the cladding structure 353 and strikes the proximal reflective surface 363. A smaller Young's modulus can increase the stress-related deformation of the cladding structure 353, which can increase the sensitivity to the incident acoustic signal. A higher photoelastic coefficient can also produce a greater sensitivity to the acoustic signal because the optical properties of such materials exhibit a larger strain-related change. Other suitable materials for the cladding structure 353 may include ultrasonic enhancement materials, such as polyvinylidene fluoride, polyparaxylene, polystyrene, and the like.

[0126] Fig.13 An embodiment of a sensor fiber providing improved rearward acoustic detection capability according to an embodiment of the present invention is shown. The sensor fibers described herein, such as sensor fiber 301, sensor fiber 351, sensor fiber 701, and sensor fiber 801, can be provided with improved rearward detection capability, such as Fig.13 shown. Fig.13A sensor optical fiber 1251 is shown with an optical resonator structure 1261. The optical resonator structure 1261 includes an optical resonator defined by a proximal reflective surface 363 and a distal reflective surface 364, which are arranged to share an axis with an optical waveguide 371 (e.g., the optical resonator is arranged in the same manner as the forward configuration described above). An optical cavity 365 is arranged between the proximal reflective surface 363 and the distal reflective surface 364. The proximal reflective surface 363 and the distal reflective surface 364 both serve as acoustic response surfaces. The optical resonator structure 1261 may further include any of the features of the optical resonators and optical resonator structures discussed herein in any suitable combination. To increase rear-view capability, the optical resonator structure 1261 may include a distal portion of the optical waveguide 371 that is specifically configured to increase acoustic sensitivity at the proximal reflective surface 363. The optical resonator structure 1261 may include a cladding structure of the distal end of the optical waveguide 371, which may include a proximal cladding structure portion 353A and a distal cladding structure portion 353B. The distal cladding structure portion 353B is disposed closer to the optical resonator. The distal cladding structure portion 353B may be selected to have a material that reduces or minimizes the acoustic impedance mismatch with the intended medium in which the sensor optical fiber 1251 will be used. For example, the distal cladding structure 353B may include a polymer, as discussed above. In an embodiment, the distal cladding structure 353B may include benzocyclobutene (BCB) or polydimethylsiloxane (PDMS), each of which has a small Young's modulus (E), a high photoelastic coefficient, and a small refractive index (n). The distal cladding structure 353B may have a length dimension sufficient to allow acoustic signals from various back-viewing angles to reach the proximal reflective surface 363 of the optical resonator. The proximal cladding structure portion 353A may include any suitable material for optical waveguides, including, for example, silicon dioxide.

[0127] Fig.14 1261 is a diagram showing the directional range of an optical resonant structure according to an embodiment of the present invention. As discussed above, the optical resonator structure 1261 can be configured to detect acoustic signals over a wide range of incidence. In an embodiment, the optical resonator structure 1261 can be configured to detect acoustic signals across a directional range of at least 180 degrees, at least 270 degrees, at least 300 degrees, or at least 330 degrees. In some embodiments, the optical resonator structure 1261 can be configured to detect acoustic signals in an omnidirectional manner, such as across a range of 360 degrees. Fig.14A side view of an optical resonator structure 361 according to an embodiment of the present invention is shown. Circle 1305 represents a range 360 ​​around the optical resonator structure 1261 and has an axis 1306 that is substantially perpendicular to an axis 1307 of the optical resonator structure 1261. Circle 1305 represents a range 360 ​​from which an acoustic signal can be incident on the optical resonator structure 1261. The optical resonator structure 1261 can be configured to detect acoustic signals in an acoustically responsive portion 1303 of circle 1305, and can have reduced sensitivity or detection capabilities in a portion of reduced acoustic sensitivity including a lateral portion 1301 and a core portion 1302. In the lateral portion 1301, the incident acoustic signal may be less detectable due to the oblique incident angle on the reflective surface of the optical resonator. In the core portion 1302, the acoustic signal may be less detectable due to obstruction from the core of the optical waveguide. The sum of the ranges of the acoustically responsive portion 1303 can represent the range over which the optical resonator structure 1261 detects the acoustic signal. Different arrangements of optical resonator structures (eg, lateral optical resonator structures 1021) may have different arrangements of acoustically responsive portions 1303 and portions of reduced acoustic sensitivity.

[0128] In an embodiment, the optical resonator structure 361 is radially symmetric. Therefore, the acoustic response range defined by the two-dimensional circle 1305 can be rotated about the axis 1307 to define the three-dimensional acoustic response range of the optical resonator structure 1261. It should be understood that further influences on the acoustic response range can be caused by structures surrounding the optical resonator structure 1261, including, for example, the distal end 231 of the medical device.

[0129] Fig.15An optical resonator structure including an in-fiber Bragg grating according to an embodiment of the present invention is shown. An optical resonator structure 1421 may be provided, as well as any of the sensor fibers discussed herein. The optical resonator structure 1421 includes a distal reflective surface 1464, an elongated optical cavity 1465 including a distal cladding structure 1453A and a proximal cladding structure 1453B, and a Bragg grating 1470. As in the optical resonator structure 1261, the distal cladding structure 1453A may include a polymer (e.g., benzocyclobutene (BCB) or polydimethylsiloxane (PDMS)), while the proximal cladding structure 1453B may include, for example, silica glass. The length of the proximal cladding structure 1453B may be greater than the distal cladding structure 1453A, for example, more than 2x, more than 5x, more than 10x, etc. In an embodiment, the proximal cladding structure 1453B may be approximately 10 times the length of the distal cladding structure 1453A, for example, the length of the distal cladding structure may be approximately 10 microns, while the length of the proximal cladding structure is approximately 100 microns. In an embodiment, the proximal cladding structure 1453B may have a Young's modulus in the range of 60-80 GPa, while the distal cladding structure 1453A has a Young's modulus in the range of 0.8-1.2 GPa. In an embodiment, the proximal cladding structure 1453B may have a photoelastic coefficient C1=-6*10 -13 1 / Pa and C2 = -4.2*10 -12 1 / Pa, while the far cladding structure 1453A has a photoelastic coefficient C1 = -4.8*10 -11 1 / Pa and C2 = -2.9*10 -111 / Pa. Although these numbers are provided, such photoelastic coefficients are relative numbers that depend on the selected material. For the distal end, materials with larger C1 or C2 values ​​are preferred to optimize acoustic sensitivity. The Bragg grating 1470 is integrated into the structure of the core 1412 and defines a change in the refractive index of the core 1412, thereby creating a structure that can reflect light of a specific wavelength. The optical resonator structure 1421 operates as a hybrid Fabry-Perot resonator. In this configuration, the distal cladding structure 1453A (e.g., a polymer structure) provides the primary response to the acoustic signal. The distal cladding structure 1453A can be manufactured directly on top of an optical fiber with an in-fiber Bragg grating reflector via two-photon polymerization (TPP) 3D printing. One advantage of the hybrid optical resonator structure 1421 is the combination of wide bandwidth and high sensitivity. In some designs, there is a tradeoff between wide bandwidth and high sensitivity. In this hybrid configuration, the total length of the elongated optical cavity 1465 is longer because it is the sum of the distal cladding structure 1453A and the proximal cladding structure 1453B. For a longer cavity length, the frequency bandwidth response may be narrower in a conventional design. However, in this hybrid configuration, since the main response of the FPI sensor comes from the polymer region, the effective sensor thickness is still very small and provides a broadband response.

[0130] Fig.16 Steps of a method for generating position and imaging information by a fiber-based optical sensor are shown. More details can be found in co-pending U.S. Provisional Application No. 63 / 522,994, entitled “Transponder Tracking and Ultrasound Image Enhancement,” filed on June 23, 2023, and U.S. Patent Application No. 63 / 522,994, entitled “Transponder Tracking and Ultrasound Image Enhancement,” filed on October 23, 2023, with attorney docket number 109835-1394978.

[0131] Method 2000 may include block 2010, wherein a transponder, such as Figure 2 The acoustic probe 245 is shown transmitting acoustic pulses into the medium. The transponder may transmit these pulses using various known methods or as described above.

[0132] At block 2020, the fiber optic sensor 101 receives the ultrasound pulses and / or scattered signals or tissue harmonics transmitted from the probe 245. The fiber optic sensor 101 then converts the ultrasound pulses, scattered signals and / or tissue harmonics into signals that are then transmitted to the processing unit 209.

[0133] At block 2030, processing unit 209 determines the position of the fiber optic sensor based at least in part on the signals received from probe 245. For example, processing unit 209 may determine the position of the distal end of the medical device based on multiple signals received from probe 100 and fiber optic sensor 101 using triangulation or coherent imaging.

[0134] At block 2040, the processing unit 209 and the image reconstruction unit 206 generate an ultrasound image based on the signal returned to the probe 245 and / or the scattered signal and tissue harmonics sensed by the fiber optic sensor. The ultrasound image may be transmitted to and displayed on a display.

[0135] At block 2050, the processing system modifies the ultrasound image based on the ultrasound pulses received from the fiber optic sensor 101. In an embodiment, the processing system may also generate and display ultrasound images based on the ultrasound pulses received by the fiber optic sensor without requiring information from the ultrasound pulses received by the probe 245.

[0136] At block 2060, the processing system 200 overlays the location of the fiber optic sensor 101 on the ultrasound image. Thus, when viewed by a user such as an ultrasound technician, a physician, other medical personnel, or a patient, the fiber optic sensor 101 on the distal end of the medical device is displayed on the same display as the ultrasound image, indicating the location of the fiber optic sensor 101 on the distal end of the medical device in the medium.

[0137] Fig.17A and 17B A needle configured with a sensor fiber according to an embodiment herein is shown. Needle 1500A can be an example of a distal end 231 of a medical device, and can include one or more sensor fibers 1501 integrated therewith. Sensor fiber 1501 can include any sensor fiber described herein (having any of the optical resonator structures), and / or can include any combination of features of sensor fibers described herein. Needle 1500A can be any type of needle having any appropriate size or function. Needle 1500A includes a needle body 1505 having a needle shaft portion 1510 and a needle tip portion 1511. The needle tip portion 1511 can be characterized by a needle polishing angle 1523. In addition, needle 1500A includes at least one sensor channel 1512 extending on the needle body 1505 for at least a portion of the length of the needle shaft portion 1510 and the needle tip portion 1511.

[0138] In an embodiment, the sensor channel 1512 may include a groove, depression, or recess in the needle body 1505. The sensor channel 1512 may be sized and configured to receive a sensor fiber 1501 according to an embodiment of the present invention. For example, in an embodiment, the width of the sensor channel 1512 may be approximately 125 to 250 microns to accommodate a sensor fiber 1501 having a diameter of 80 microns. The needle 1500A may include a plurality of sensor channels 1512 to accommodate a plurality of sensor fibers 1501. For example, the needle 1500A may include 2, 3, 4, or more sensor channels 1512 to accommodate a plurality of sensor fibers 1501 arranged around the perimeter of the needle 1500A. The sensor fibers 1501 are arranged within the sensor channels 1512 such that the distal end of the loaded optical resonator structure is positioned at or adjacent to the distal end. The sensor channels 1512 may be configured with a depth such that the sensor fibers 1501 do not extend beyond the outer surface of the needle body 1505.

[0139] In other embodiments, the sensor channel can be created by adding material to the outer surface to form the channel, for example as a guide. In an example, material can be layered on the outside of the needle to form the channel 1512 as a raised continuous or intermittent structure. In another example, the adhesive material or tape can be wrapped in a spiral configuration with spaces within the spiral to form the sensor channel, or can be selectively positioned along the length of the needle to form the sensor channel and guide the sensor fiber along the length. In yet another example, the extruded needle can include a tubular sensor channel in the form of a lumen extending therethrough.

[0140] The sensor channel 1512 allows the sensor fiber 1501 to be located within a protected area of ​​the needle body 1505. This serves to protect the sensor fiber 1501 and to create a smooth needle surface for insertion. The sensor channel 1512 may be disposed on an outer surface of the needle body 1505 (e.g., Fig. 17B as shown) or disposed on the inner surface of the needle body 1505.

[0141] The sensor fiber 1501 may be fixed to the needle 1505. In an embodiment, the sensor fiber 1501 may be fixed in the sensor channel 1512 by a potting compound, such as Norland-65 glue, Norland 81 glue, MY-132A polymer, MY-133, BIO-133, DC-133, or any other suitable potting compound. The potting compound may be selected based on its acoustic and mechanical properties, such as acoustic velocity, acoustic impedance, thermal conductivity, water resistance, etc. In addition to mechanical fixation and protection of the sensor, the potting compound may also provide modification of the acoustic impedance match with the surrounding medium. The potting compound may be used on all or a portion of the sensor channel 1512. In an embodiment, the sensor fiber 1501 may be fixed in the sensor channel 1512 by a sheath 1520. The sheath 1520 is configured to wrap around the needle 1505. The sheath 1520 may mechanically fix the sensor fiber 1501 to the needle 1505. The sheath can wrap around the needle, with the optical fiber in the groove, so that the optical fiber can float freely in the groove / groove. This can allow the needle to bend / have flexibility. In an embodiment, the sensor optical fiber 1501 can be fixed at least in part by both the sheath 1520 and the potting compound. Such an arrangement can allow relative movement between the sensor optical fiber 1501 and the needle body 1505, thereby providing potential strain relief in the event of needle bending. The needle 1500A can be made of any suitable material, including, for example, medical grade materials, including metals such as stainless steel or polymers such as PEEK (polyetherketone). In an embodiment, the needle 1500 can be manufactured by additive manufacturing techniques, such as 3D printing, injection molding, or extrusion.

[0142] exist Fig.18A and 18B 1500B and having an optical sensor based on a fiber optic cable. The needle 1500B may further include one or more windows 1513. The window 1513 is an opening in the needle body 1505 disposed at the end of the sensor channel 1512. The needle 1500B may include multiple sensor channels 1512 and a corresponding plurality of windows 1513 to accommodate multiple sensor fibers 1501. The sensor fibers 1501 may be arranged within the sensor channels 1512 such that the distal ends of the loaded optical sensors extend into the windows 1513. In this embodiment, the distal ends of the sensor fibers 1501 may be secured within the windows 1513 by a potting compound, while the proximal portions of the sensor fibers 1501 may be secured to the needle body 1505 by a sheath 1520. This will allow relative movement between the sensor fibers 1501 and the needle body, thereby providing strain relief in the event of needle bending.

[0143] The window 1513 allows the acoustic signal to reach the fiber optic sensor of the sensor fiber 1501 without being blocked by the needle body 1505. The edge of the window 1513 can create a boundary for the diffraction of the acoustic signal and allow the acoustic signal to bend and propagate around the window edge to reach the fiber optic sensor at the end of the sensor fiber 1501. The diffraction effect has the following function: increasing the circular range of acoustic signal detection of the sensor fiber 1501. In addition, the edge of the channel on the needle surface can also have a diffraction effect that helps detect the needle axis.

[0144] In an embodiment, an optical ultrasound sensor according to an embodiment of the present invention may be integrated with a medical device (e.g., at the distal end 231 of the medical device), and may work with an ultrasound source (array) configured at an ex vivo location to provide location information of the distal end 231 of the medical device and / or provide real-time acoustic monitoring at a target / anatomical region of surgery. In different application scenarios, the direction of the incoming acoustic signal can be roughly divided into two categories, namely (1) lateral emission (fire); and (2) axial emission, e.g. Fig. 18C and 18D shown.

[0145] Fig. 18C and 18D An acoustic signal is shown incident on a sensor fiber disposed within needle window 1513. For clarity, the sensor fiber is not shown in these figures. Fig. 18C shows a lateral acoustic signal 1600, while Fig.18D The axial acoustic signal is shown.

[0146] Fig. 18C The lateral acoustic signal 1600 is typical of what may occur when using a side view endoscopic ultrasound transducer or an external transducer. The location of the window 1513 near the needle tip portion 1511 allows the ultrasound field to reach the window (and the fiber tip sensor structure located therein) from either side without being blocked by the opposing wall of the needle. The fiber tip sensor structure itself can be arranged in a sideways or forward manner, and can also be a polarization-based sensor configured to receive sideways (lateral) signals, depending on the requirements of the application.

[0147] Fig.18D The axial acoustic signal 1601 is a typical case for a front view endoscopic ultrasound transducer. Due to the small footprint of the endoscopic device, the typical incident angle may be small relative to the needle body. Fig.18D As shown, when the incident angle is less than the needle polishing angle 1523 (as shown in Fig.18D1501 ), at least a portion of the acoustic signal 1601 may be blocked by the needle body (shown as thicker cross-hatching). To address this issue, in an embodiment, an additional window 1513 opposite the sensor window may be included in the needle body 1505 to allow the axial acoustic signal 1601 to pass through and reach the optical resonator structure. In another embodiment, the orientation of the needle 1500A / B may be manipulated to ensure that the low-angle axial acoustic signal arrives from the portion of the needle where the optical resonator structure is not located. In another embodiment, the polishing angle 1523 may be selected based on the desired acoustic incidence angle.

[0148] exist Fig.19 1 and having an optical sensor based on a fiber optic cable. Similar to needles 1500A and 1500B, needle 1500C includes a needle body 1505 having a needle shaft portion 1510 and a needle tip portion 1511. The needle tip portion 1511 may be characterized by a needle polishing angle. In addition, needle 1500C includes at least one sensor channel 1512 extending through at least a portion of the length of the needle shaft portion 1510 and the needle tip portion 1511 in the needle body 1505. Needle 1500C may include one or more sensor optical fibers 1501C disposed in one or more sensor channels 1512 thereof. Sensor optical fiber 1501C may be similar to sensor optical fiber 301C and, therefore, may include a fiber end sensor structure 1521 disposed at an end thereof and one or more polarization-based sensor structures 1522 disposed along its length. The polarization-based sensor structures 1522 positioned along the length of the needle 1500C can provide enhanced visualization of the needle 1500C when an acoustic signal used to track or visualize the needle 1500C strikes the polarization-based sensor structures 1522. Information gleaned from the optical signal indicative of the incident acoustic signal can be employed alone and / or in conjunction with conventional acoustic ultrasound images to provide improved visualization of the needle 1500C. The polarization-based sensor structures 1522 can be used in accordance with the above description of the polarization-based sensor structures 322C and the above description of the polarization-based sensor structures 322C. Fig.6D and 6E Operate according to the principles discussed.

[0149] Fig. 20A and Fig. 20B Another close up view of needle 1500 with integrated sensor fiber 1501 is provided. Fig. 20A shows a perspective view from a first side of needle 1500 where channel 1512 is located, and Fig. 20B15. A perspective view from a second side of the needle 1500 opposite the first side is shown. The second side of the needle 1500 includes an interior view of the needle 1500 at the needle tip portion 1511. As shown, the sensor fiber 1501 is disposed within a sensor channel 1512 of the needle 1500, extending from the needle shaft portion 1510 and into the needle tip portion 1511. A window 1513 is disposed within the needle tip portion 1511, thereby ensuring that both sides of the window 1513 (and the sensor fiber 1501 disposed therein) are exposed to incoming acoustic signals. In addition, Figures 20A-20B Potting compound 1525 is shown securing sensor fiber 1501 within window 1513 .

[0150] exist Fig. 20C In another embodiment shown, the sensor optical fiber 1501D can be fixed to a surface of the needle body 1505D of the needle 1500D that does not have a channel or other fiber receiving structure. The optical fiber 1501D can be fixed to the needle 1500D using a suitable polymer or compound 1527 selected based on its acoustic and mechanical properties. The suitable polymer or compound 1527 can be selected based on its acoustic and mechanical properties, such as sound velocity, acoustic impedance, thermal conductivity, water resistance, etc. In addition to the mechanical fixation and protection of the sensor on its surface, the suitable polymer or compound 1527 can also provide modification of the acoustic impedance matching with the surrounding medium. Similarly, as Fig.20D As shown, a sheath 1520D can be used to secure the sensor optical fiber to the needle body 1505D. The sheath 1520D is configured to wrap around the needle body 1505D. The sheath 1520D can mechanically secure the sensor optical fiber 1501D to the needle body 1505D. The sheath can wrap around the needle in a manner that allows the optical fiber to move within the sheath. This can allow the needle to bend / have flexibility. In an embodiment, the sensor optical fiber 1501D can be at least partially secured by both the sheath 1520D and the polymer or compound 1527. Such an arrangement can allow relative movement between the sensor optical fiber 1501D and the needle body 1505D, thereby providing potential strain relief in the event of needle bending. This embodiment can further include a window in the manner in which other embodiments have a window. A potting compound or polymer can be used to further secure the optical fiber located within the window in the manner of the previous embodiments.

[0151] Fig.21The distal end of a medical device with an optical fiber tip sensor according to an embodiment of the present invention is shown. The distal end 1901 of the medical device includes a catheter 1902 and a medical tool, such as a needle 1903. The catheter 1902 is configured to carry the needle 1903 (e.g., providing a passage through the lumen from which the needle can be delivered) to the treatment and / or diagnosis site via a lumen 1904. The catheter 1902 may further include a guidewire lumen 1905, which is configured to guide the catheter 1902 to the treatment and / or diagnosis site along the guidewire. The needle 1903 is configured to extend from the lumen 1904 of the catheter 1902 when it reaches the treatment and / or diagnosis site (e.g., by an operator, a person, or a robot). In an embodiment, the needle 1903 can be configured in a manner similar to the needle 1500, including one or more sensor optical fibers 1501 disposed thereon or integrated therewith. In an embodiment, the catheter 1902 may include one or more sensor optical fibers and one or more acoustic transducers disposed thereon or integrated therewith. In embodiments, one or more sensor fibers 1501 may be used to sense, monitor, and / or track the position of the needle 1903 (e.g., based on acoustic signals generated by an acoustic transducer / probe that is located outside of the medium in which the catheter 1902 is used). The one or more sensor fibers 1501 and one or more acoustic transducers disposed on the catheter 1902 may be used to generate an image, such as detection of acoustic echoes by the one or more sensor fibers. The one or more acoustic transducers may generate an acoustic signal, while the one or more sensor fibers receive echoes or reflections of the acoustic signal based on their interaction with the surrounding medium. The acoustic transducers will also receive reflected or scattered acoustic signals and / or tissue harmonics, which may then be used to create an image of the surrounding area to which tracking information will be added.

[0152] Fig. 22 An example use of a fiber-based optical sensor incorporated into a needle is shown. The use shown may be incorporated with needle 1500A, needle 1500B, 1500C, 1500D, or any suitable needle incorporating a fiber-based optical sensor. Fig. 22 As shown, an external acoustic probe 2245 having a needle 1500A / B / C / D and a fiber-based optical sensor can be employed. As discussed herein, in the positioning / guidance embodiments, the fiber-based optical sensor can receive the acoustic signals generated by the external acoustic probe 2245. These acoustic signals can then be used alone or in combination with reflected acoustic signals captured by the acoustic probe to determine the location of the needle within a medium 2260 (e.g., a patient's body).

[0153] Figures 23A-23BAn embodiment of a fiber-based optical sensor incorporated into a catheter-delivered needle is shown. For example, the catheter-delivered needle can be used in a biopsy procedure. The needle 2515 can be delivered to the surgical site via the catheter 2503. The needle 2515 can incorporate a fiber-based optical sensor 2501, as described in various embodiments herein. After being delivered to the surgical site via the catheter 2503, the needle 2515 can extend from a lumen in the catheter 2503 to perform the surgery. The needle 2515 can be monitored, guided and or positioned by using one or more external acoustic transducers that provide acoustic signals received by the fiber-based optical sensor 2501. For example, the acoustic transducer can be associated with an optical sensor system. The optical sensor system, which can be an example of the various optical sensor systems described herein, can provide the processing and signal generation / reception requirements required to perform the photoacoustic signal sensing methods described herein. In other embodiments, such as Fig. 23B As shown in , the catheter 2503 may include one or more additional transducers. For example, the catheter may include a hybrid acoustic array 2507, which includes one or more of an AEG (or other suitable acoustic transducer array) array and a photonic integrated circuit (PIC) optical sensor array. US application publication 20230148869, filed on November 18, 2022, entitled "Mixed Ultrasound Transducer Arrays" and incorporated herein by reference, and US application publication US20220350022, filed on April 29, 2021, entitled "Modularized Acoustic Probe" and incorporated herein by reference, disclose various optical sensors that can be used in hybrid transducer arrays. PIC arrays can be used to detect acoustic signals. Similar to the optical fiber end sensors discussed herein, PIC arrays can be used to detect acoustic signals by measuring or detecting changes in the optical properties of the PIC array caused by the incidence of acoustic signals. In an embodiment, acoustic signal data captured in various ways by the fiber-based optical sensor 2501, PIC array, AEG array, and external acoustic transducer can be used by the optical sensor system in any combination to monitor, guide, and locate the needle 2515 (and the catheter 2503 for delivering the needle) and to generate images of the medium (e.g., the surgical site) in which the catheter 2503 is deployed.

[0154] In other embodiments, the optical sensors based on fiber according to the embodiments herein can be used for various additional purposes. For example, the optical sensors based on fiber can be used to track a cannula configured with an optical camera and a movable ultrasonic transducer used in vivo during minimally invasive surgery. In another embodiment, an implantable (transcutaneous) or percutaneous (percutaneous) ultrasound probe can be configured with one or more optical sensors based on fiber according to embodiments of the present invention. In another embodiment, a guidewire can be configured with one or more optical sensors based on fiber according to embodiments of the present invention.

[0155] In other embodiments, real-time visualization of the tip of the device containing the fiber optic sensor can be co-registered with the diagnostic ultrasound image, eliminating the need for calibration. This breakthrough enables clinicians to confidently track the device in challenging anatomical areas. A real-time confidence indicator of the intersection of the device tip with the imaging plane can be provided, with special consideration given to detecting when the device tip leaves the imaging plane, which can ensure accurate device tip tracking even during complex surgeries. Real-time prospective visualization of the tip trajectory can be provided, providing valuable insights into the predicted path of the device tip and visualization of the device tip trajectory, which can be used to enhance procedural confidence and documentation. In addition, a device incorporating the fiber optic sensor described herein can facilitate the display of anatomical and blood flow images from an indwelling sensor co-registered with a cross-sectional image, which can enhance diagnostic accuracy and confidence.

[0156] The terms used herein are only used to describe specific embodiments and are not intended to limit the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms "a / an" and "the" are expected to also include plural forms. It should be further understood that the term "includes and / or including" used in this specification specifies the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0157] Additional embodiments may include:

[0158] Embodiment 1 is a device comprising: a sensor optical fiber, comprising: an optical waveguide, which includes a core and a cladding structure; an optical sensor structure, which is coupled to a first end of the optical waveguide and includes at least one of an optical resonator, an optical interferometer, a facet microstructure and a polarization sensitive structure, the optical sensor structure being configured to: detect an acoustic signal, and provide an optical signal corresponding to the acoustic signal to the optical waveguide.

[0159] Embodiment 2 is the apparatus of embodiment 1, and further comprises an encapsulation structure configured with a first portion surrounding the optical waveguide and a second portion at least partially surrounding the optical sensor structure.

[0160] Embodiment 3 is the apparatus of any one of embodiments 1 to 2, wherein the optical sensor structure is a fiber optic sensor.

[0161] Embodiment 4 is the apparatus of any one of embodiments 1 to 3, wherein the optical sensor structure is an optical resonator comprising a Fabry-Perot resonator, a whispering gallery mode resonator, a microring, a microtoroid, a spiral resonator, or a photonic crystal resonator.

[0162] Embodiment 5 is the apparatus of any one of embodiments 1 to 3, wherein the optical sensor structure is an optical interferometer, including a Mach-Zehnder (MZ) interferometer, a Fabry-Perot interferometer, a phase-shifting coherence interferometer, or a self-mixing interferometer.

[0163] Embodiment 6 is a device according to any one of embodiments 1 to 3, wherein the optical sensor structure is an optical fiber end face, which contains an acoustically responsive metasurface pattern, an acoustically responsive low-dimensional material, or a plasma structure, and the plasma structure is patterned to amplify light-matter interaction.

[0164] Embodiment 7 is the apparatus of any one of embodiments 1 to 6, wherein the optical sensor structure is configured to cause a change in polarization of the transmitted light in response to the acoustic signal.

[0165] Embodiment 8 is the apparatus of any one of embodiments 1 to 7, wherein the optical sensor structure is a point sensor or a line sensor.

[0166] Embodiment 9 is the apparatus of any one of embodiments 1 to 8, wherein the core or the cladding structure comprises a material having at least one of a relatively small Young's modulus (E) and a relatively high photoelastic coefficient.

[0167] Embodiment 10 is the apparatus of any one of embodiments 1 to 9, wherein the cladding structure has a lower refractive index (n) than the core.

[0168] Embodiment 11 is the apparatus of any one of embodiments 1 to 10, wherein the acoustic impedance of the encapsulation structure is selected to match an impedance within 20% of an optical resonator structure impedance.

[0169] Embodiment 12 is a device according to any one of embodiments 2 to 11, wherein the encapsulating structure comprises a material having a relatively small Young's modulus (E), a relatively high photoelastic coefficient and / or a relatively large refractive index (n).

[0170] Embodiment 13 is the apparatus of any one of embodiments 1 to 12, wherein the acoustic impedance of the encapsulation structure is selected to match an impedance within 20% of an optical resonator structure impedance.

[0171] Embodiment 14 is the apparatus of any one of embodiments 1 to 13, further comprising a medical device in which the sensor optical fiber is disposed.

[0172] Embodiment 15 is an apparatus according to embodiment 14, wherein the medical device is one of a needle, an endoscope, a catheter, a cannula, a guidewire, a surgical tool, a diagnostic tool, or a therapeutic tool.

[0173] Embodiment 16 is an apparatus according to embodiment 15, wherein the medical device is a needle comprising: a shaft portion configured to receive the sensor optical fiber; and a tip portion configured to receive the optical sensor structure.

[0174] Embodiment 17 is the apparatus of embodiment 16, wherein the needle further comprises a window in the shaft portion or the tip portion proximate the optical sensor structure.

[0175] Embodiment 18 is the apparatus of embodiment 16, wherein the needle further comprises a channel disposed in the shaft portion, the sensor fiber disposed within the channel.

[0176] Embodiment 19 is the apparatus of embodiment 16, wherein the needle further comprises a sheath disposed around the needle and configured to house the sensor optical fiber.

[0177] Embodiment 20 is the apparatus of embodiment 17, wherein the needle further comprises a plurality of additional windows in the shaft portion or the tip portion.

[0178] Embodiment 21 is an apparatus according to any one of embodiments 1 to 20, wherein the optical sensor structure is configured to detect the acoustic signal across a directional range of at least 180 degrees, at least 270 degrees, at least 300 degrees, at least 330 degrees, or 360 degrees.

[0179] Embodiment 22 is the apparatus of any one of embodiments 1 to 21, wherein the optical sensor structure is configured for forward detection of the acoustic signal.

[0180] Embodiment 23 is the apparatus of any one of embodiments 1 to 22, wherein the optical sensor structure is further configured for rear-view detection of acoustic signals.

[0181] Embodiment 24 is the apparatus of any one of embodiments 1 to 23, wherein the optical sensor structure is configured for lateral detection of the acoustic signal.

[0182] Embodiment 25 is the apparatus of any one of embodiments 1 to 24, wherein the optical sensor structure comprises a distal portion comprising silicon dioxide and a proximal portion comprising a polymer.

[0183] Embodiment 26 is the apparatus of embodiment 16, wherein the optical sensor structure comprises an in-fiber Bragg grating.

[0184] Embodiment 27 is the apparatus of any one of embodiments 1 to 26, wherein the core is contained among a plurality of cores in the optical waveguide.

[0185] Embodiment 28 is a device according to any one of Embodiments 1 to 28, further comprising: a light source configured to provide light to the optical sensor structure via the optical waveguide; a photodetector configured to receive the light signal; and a processing unit configured to: control the light source, receive optical data based on the light signal from the photodetector, and perform at least one of image generation and position determination based on the optical data.

[0186] Embodiment 29 is the apparatus of any one of embodiments 1 to 28, further comprising a wavelength tuning mechanism configured to adjust the resonance of the optical sensor structure via application of at least one of thermal stress and mechanical stress.

[0187] Embodiment 30 is the apparatus of embodiment 28, wherein the light source is a working laser, and the processing unit is further configured to tune a wavelength of the working laser.

[0188] The above embodiments are illustrative examples, and should not be construed as limiting the present invention to these specific embodiments. It should be understood that the various embodiments disclosed herein may be combined in a combination form different from the combination specifically presented in the description and the drawings. It should also be understood that, depending on the example, certain actions or events of any process or method described herein may be performed in different orders, may be added, merged or completely omitted (for example, all described actions or events may not be necessary for implementing the method or process). In addition, although for clarity, certain features of the embodiments of the present invention are described as being performed by a single module, device or unit, it should be understood that the features and functions described herein may be performed by any combination of units or modules. Therefore, without departing from the spirit or scope of the present invention defined in the appended claims, those skilled in the art may affect various changes and modifications.

Claims

1. A device comprising: A sensor optical fiber comprising: an optical waveguide comprising a core and a cladding structure; an optical sensor structure coupled to the first end of the optical waveguide and comprising at least one of an optical resonator, an optical interferometer, a facet microstructure, and a polarization sensitive structure, the optical sensor structure being configured to: Detecting an acoustic signal, and An optical signal corresponding to the acoustic signal is provided to the optical waveguide.

2. The apparatus of claim 1, further comprising an encapsulation structure configured with a first portion surrounding the optical waveguide and a second portion at least partially surrounding the optical sensor structure.

3. The device of claim 1, wherein the optical sensor structure is a fiber optic sensor.

4. The apparatus of claim 1, wherein the optical sensor structure is an optical resonator comprising a Fabry-Perot resonator, a whispering gallery mode resonator, a microring, a microtoroid, a spiral resonator, or a photonic crystal resonator.

5. The apparatus of claim 1, wherein the optical sensor structure is an optical interferometer, including a Mach-Zehnder (MZ) interferometer, a Fabry-Perot interferometer, a phase-shifting coherence interferometer, or a self-mixing interferometer.

6. The apparatus of claim 1, wherein the optical sensor structure is an optical fiber end facet comprising an acoustically responsive metasurface pattern, an acoustically responsive low-dimensional material, or a plasmonic structure patterned to amplify light-matter interactions.

7. The apparatus of claim 1, wherein the optical sensor structure is configured to cause a change in polarization of transmitted light in response to the acoustic signal.

8. The device of claim 1, wherein the optical sensor structure is a point sensor or a line sensor.

9. The apparatus of claim 1, wherein the core or the cladding structure comprises a material having at least one of a relatively small Young's modulus (E) and a relatively high photoelastic coefficient.

10. The apparatus of claim 2, wherein the cladding structure has a lower refractive index (n) than the core.

11. The apparatus of claim 2, wherein the acoustic impedance of the encapsulating structure is selected to match an impedance within 20% of an optical resonator structure impedance.

12. The device of claim 2, wherein the encapsulating structure comprises a material having a relatively small Young's modulus (E), a relatively high photoelastic coefficient, and / or a relatively large refractive index (n).

13. The apparatus of claim 10, wherein the acoustic impedance of the encapsulating structure is selected to match an impedance within 20% of an optical resonator structure impedance.

14. The apparatus of claim 1, further comprising a medical device in which the sensor optical fiber is disposed.

15. The apparatus of claim 14, wherein the medical device is one of a needle, an endoscope, a catheter, a cannula, a guidewire, a surgical tool, a diagnostic tool, or a therapeutic tool.

16. The apparatus of claim 15, wherein the medical device is a needle, comprising: a shaft portion configured to receive the sensor optical fiber; and A tip portion is configured to receive the optical sensor structure.

17. The apparatus of claim 16, wherein the needle further comprises a window in the shaft portion or the tip portion proximate the optical sensor structure.

18. The apparatus of claim 16, wherein the needle further comprises a channel disposed in the shaft portion, the sensor fiber disposed within the channel.

19. The apparatus of claim 16, wherein the needle further comprises a sheath disposed around the needle and configured to house the sensor optical fiber.

20. The apparatus of claim 17, wherein the needle further comprises a plurality of additional windows in the shaft portion or the tip portion.

21. The apparatus of claim 1, wherein the optical sensor structure is configured to detect the acoustic signal across a directional range of at least 180 degrees, at least 270 degrees, at least 300 degrees, at least 330 degrees, or 360 degrees.

22. The apparatus of claim 1, wherein the optical sensor structure is configured for forward detection of the acoustic signal.

23. The apparatus of claim 1, wherein the optical sensor structure is further configured for rear-view detection of acoustic signals.

24. The apparatus of claim 1, wherein the optical sensor structure is configured for lateral detection of the acoustic signal.

25. The apparatus of claim 1, wherein the optical sensor structure comprises a distal portion comprising silicon dioxide and a proximal portion comprising a polymer.

26. The apparatus of claim 16, wherein the optical sensor structure comprises an in-fiber Bragg grating.

27. The apparatus of claim 1, wherein the core is contained among a plurality of cores in the optical waveguide.

28. The apparatus of claim 1, further comprising: a light source configured to provide light to the optical sensor structure via the light waveguide; a photodetector configured to receive the optical signal; as well as A processing unit configured to: controlling the light source, receiving optical data based on the optical signal from the photodetector, and Based on the optical data, at least one of image generation and position determination is performed.

29. The apparatus of claim 1, further comprising: A wavelength tuning mechanism is configured to adjust the resonance of the optical sensor structure via application of at least one of thermal stress and mechanical stress.

30. The apparatus of claim 28, wherein the light source is a working laser, and the processing unit is further configured to tune a wavelength of the working laser.

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