Directing light into optical fiber

Abstract

To provide a system that can direct light into an optical fiber.SOLUTION: The system has imaging optics that can form an image of an end of an optical fiber. An actuatable optical element of the system can be configured to define an optical path that extends to the actuatable optical element and further to the end of the optical fiber. A processor of the system can determine a location in the image of a specified feature in the image. The processor can actuate, based on the location of the specified feature in the image, the actuatable optical element so as to align the optical path to a core of the optical fiber. A light source of the system can direct a light beam along the optical path to couple into the core of the optical fiber.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of U.S. Provisional Application No. 63 / 034,277, filed June 3, 2020, which is incorporated by reference in its entirety.

[0002] The present disclosure relates to optical systems capable of directing light into optical fibers. [Background technology]

[0003] The optical system may use an optical fiber, such as a single mode fiber. Misalignment of a light beam with respect to the core of the single mode fiber may reduce the coupling efficiency of the beam into the core and increase losses in the optical system. Summary of the Invention

[0004] As an example, the system may direct light to an optical fiber. The system includes imaging optics, an actuatable optical element, a processor, and a light source. The imaging optics are configured to form an image of an end of the optical fiber. The actuatable optical element is configured to define an optical path that extends to the actuatable optical element and further to the end of the optical fiber. The processor is configured to determine a location within the image of a designated feature within the image. The processor is further configured to actuate the actuatable optical element to align the optical path to a core of the optical fiber based on the location of the designated feature within the image. The light source is configured to direct a light beam along the optical path to couple to the core of the optical fiber.

[0005] In another example, a method is for operating a system to direct light to an optical fiber. The system has imaging optics, a processor, and an actuatable optical element. The actuatable optical element defines an optical path, the optical path extending to the actuatable optical element and further to an end of the optical fiber. The method includes: generating an image of the end of the optical fiber with the imaging optics; determining, with the processor, a location within the image of a designated feature within the image; operating, with the processor, based on the location of the designated feature within the image, the actuable optical element to align the optical path with a core of the optical fiber; and directing a light beam along the optical path to couple to the core of the optical fiber.

[0006] In another example, a computer-readable medium stores instructions that, when executed by a processor of a system for directing light into an optical fiber, can cause the processor to perform operations such as the methods described above or elsewhere in this description. [Brief description of the drawings]

[0007] [Figure 1] 1 shows a schematic diagram of an example of an apparatus including a system for directing light into an optical fiber.

[0008] [Diagram 2] 2 illustrates an end view of an example of a light source configured as a fiber bundle suitable for use in the system of FIG. 1.

[0009] [Diagram 3] 2 shows a plan view of an example of a portion of the system of FIG. 1, where the objective element is configured as an objective mirror.

[0010] [Figure 4] 2 shows a plan view of an example of a longitudinal position sensor element suitable for use in the system of FIG. 1;

[0011] [Diagram 5]2 shows a top view of another example of a longitudinal position sensor element suitable for use in the system of FIG. 1;

[0012] [Figure 6] 2 shows a top view of another example of a longitudinal position sensor element suitable for use in the system of FIG. 1;

[0013] [Figure 7] 2 shows a plan view of a longitudinal alignment device element in the system of FIG. 1.

[0014] [Figure 8] 2 shows a plan view of an example of a longitudinal alignment device element suitable for use in the system of FIG. 1.

[0015] [Figure 9] 1 shows a flow chart of an example method of operating a system to direct light into an optical fiber.

[0016] [Figure 10] 13 shows a flow chart of an example of another method of operating a system to direct light into an optical fiber.

[0017] Corresponding reference characters indicate corresponding parts throughout the several views. Elements in the drawings are not necessarily drawn to scale. The configurations illustrated in the drawings are merely examples and should not be construed as limiting the scope of the invention in any way. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] In one example, the system can direct light to an optical fiber. Imaging optics can form an image of the end of the optical fiber. An actuatable optical element can define an optical path that extends to the actuatable optical element and further to the end of the optical fiber. A processor can determine a location within the image of a specified feature. The processor can operate the actuatable optical element to align the optical path with a core of the optical fiber based on the location of the specified feature within the image. A light source can direct a light beam along the optical path to couple to the core of the optical fiber.

[0019] The system can identify a feature in an image of the end of the optical fiber and then use the location of the feature to actively align the optical path to the core of the optical fiber. Active alignment allows the system to improve the robustness of the alignment of the optical beam with respect to the core of the optical fiber. The improved robustness of the alignment can help compensate for misalignment due to physical misalignment of the optical fiber, such as due to manufacturing tolerances, non-idealities in the mounting of the mechanical holder, etc. As a result, the system can achieve a higher coupling efficiency of the beam into the core of the optical fiber compared to an otherwise identical system that does not utilize this technology.

[0020] Further, in various examples, active alignment can be performed one or more times per use of the system. Active alignment can be performed before and / or during use of the system. As a specific example, active alignment performed one or more times during operation can help improve or maintain alignment while the optical system is operating. For example, during operation, the optical system may be subject to movement, temperature changes, physical shock or vibration (such as caused by air currents), and / or other environmental or physical changes that affect alignment. The system can compensate for environmental or physical changes periodically or in real time in response to a determination of misalignment, which can help improve or maintain sufficiently high coupling while the optical system is in use. The term "sufficiently high" is used herein to indicate sufficient coupling that allows the system to function at the performance level (e.g., in terms of resolution, accuracy, power consumption, etc.) for which the system is designed.

[0021] Furthermore, the system can help achieve sufficiently high coupling efficiency without direct contact with the end of the optical fiber, and since the system uses non-contact alignment of the optical path to the optical fiber, the system can help reduce contamination, physical wear, etc., of the end of the optical fiber.

[0022] One example of an optical system that can incorporate one or more features from the systems described below is an optical fiber-based strain, temperature, or shape sensing system. As a specific example, the optical system couples light into a multi-core optical fiber and senses the three-dimensional position in space of an element in real time or near real time. As another specific example, the optical system couples light into a multi-core optical fiber and senses the three-dimensional shape of the optical fiber in real time or near real time.

[0023] Further, example optical systems can include medical or non-medical systems. Example medical systems can include those used for diagnosis and treatment, including surgical systems. In example medical systems, the system described below can be disposed in an optical path between one or more light sources and one or more cores of the sensing optical fiber to help establish and / or maintain a sufficiently high coupling efficiency (or coupling efficiencies) of light entering the sensing optical fiber during the course of one or more medical procedures. This is just one example use of the system, which is described in more detail below. Other uses are possible.

[0024] 1 shows a schematic diagram of one example of an apparatus 1 that includes a system 100 for directing light into an optical fiber. Because system 100 can identify a feature in an image of the end of the optical fiber and then use the location of that feature to actively align an optical path to the core of the optical fiber, the system can achieve a relatively robust alignment of a light beam to the core of the optical fiber.

[0025] The controller 10 can include various optical and electronic components. In medical applications, the controller 10 can be configured as one main instrument that can be used and reused for multiple procedures. For applications directed to shape sensing, such as sensing the three-dimensional orientation or shape of an optical fiber, the controller 10 can include an interrogator 12. The interrogator 12 can direct light into the fiber and analyze the light returning from the fiber. The interrogator 12 can use techniques such as optical frequency domain reflectometry (OFDR) to determine the three-dimensional position of the optical fiber.

[0026] In some examples, a portion of the equipment can be configured as a replaceable element that can be used for part or several procedures, or can be used for one or more entire procedures and then discarded. The replaceable element can include a catheter 14 that can include a sensing optical fiber 16 that extends along at least a portion of the length of the catheter 14. In a medical example, the catheter 14 and the sensing optical fiber 16 can be maintained or reprocessed in a clean environment prior to use, or in a sterile environment if clinically necessary.

[0027] The system 100, described in detail below, can use active alignment to optically connect the optical fiber 16 to the controller 10. When optically connected, the interrogator 12 can direct light (through the system 100) to the sensing optical fiber 16, receive light reflected from locations along the length of the sensing optical fiber 16 (also through the system 100), and analyze the reflected light (such as by OFDR) to determine strain, temperature, or other physical information of the sensing optical fiber 16. For shape sensing applications, the interrogator 12 is configured to determine a three-dimensional position or shape of the sensing optical fiber 16. For clarity, the following description will refer to the sensing optical fiber 16 as the optical fiber 108. It will be understood that the optical fiber 108 can include the sensing optical fiber 16 or, optionally, a separate section of fiber coupled to the proximal end of the sensing optical fiber 16. References below to the optical fiber 108 can include one or both of these cases.

[0028] The controller 10 can include a fiber connection 18, such as a multicore fiber or a plurality of single mode fibers, that can provide light as an input to the system 100. The plurality of single mode fibers may also be referred to in this document as a bundle of single mode fibers or a fiber bundle, although the plurality of single mode fibers may be arranged in a bundle, in a linear array, or the like. The system 100 can direct the light provided by the fiber connection 18 through various elements in the system 100 to couple to the sensing optical fiber 16. Light reflected from locations along the length of the sensing optical fiber 16 can return to the system 100, can propagate through various elements in the system 100, can propagate through the fiber connection 18, and can be processed by the interrogator 12 in the controller 10. The system 100 can direct a portion of the light through the various elements to one or more detectors. The detectors can generate one or more control signals. The system 100 can use the one or more control signals to control one or more actuatable elements in the system to improve the coupling efficiency of the light into the optical fiber 108.

[0029] The controller 10 can include electrical connections 20, which can provide power to the system 100. A processor 114, which can be located in the controller 10 or in the system 100, can receive control signals from one or more detectors in the system 100 and drive one or more actuatable elements in the system 100 to improve coupling efficiency.

[0030] During operation, imaging optics in the system 100 can form an image 104 of the end 106 of the optical fiber 108. An actuatable optical element 110, such as a pivotable mirror, can define an optical path 112 that extends to the actuatable optical element 110 and further to the end 106 of the optical fiber 108, if the optical fiber 108 is present. A processor 114 can determine a location within the image 104 of a designated feature, such as a circumferential edge of the end 106 of the optical fiber 108. Although the processor 114 is shown as being co-located with the system 100, it will be understood that the processor 114 can alternatively be co-located with the controller 10. The processor 114 can operate the actuatable optical element 110 to align the optical path 112 with the core 116 of the optical fiber 108 based on the location of the designated feature within the image 104.

[0031] The optical path 112 is a geometrical construct that extends from optical element to optical element between the optical fiber connection 18 and the optical fiber 108. Specifically, one end of the optical path is at the optical fiber connection 18 and the other end is at the optical fiber 108, if the optical fiber 108 is present. The optical path 112 can be bent, translated, rotated, or otherwise aligned by the optical components during operation of the system 100. During operation of the system 100, the optical beam 120 is directed to propagate from optical element to optical element along the optical path 112, such that the optical beam 120 follows the optical path 112. It is instructive to clarify that the optical path 112 can be redirected both when the optical beam 120 is present and when the optical beam 120 is not present. In configurations where the optical fiber 108 includes multiple cores, the system 100 can include multiple optical paths 112 propagating toward respective cores of the optical fiber 108.

[0032] A light source 118 can direct a light beam 120 along the optical path 112 to couple to a core 116 of the optical fiber 108. In some examples, the controller 10 can include one or more light generating elements, such as light emitting diodes or laser diodes, and one or more light coupling elements, such as lenses, that can direct light from the light generating elements to one or more cores of one or more fibers in the fiber connection 18. In the configuration of FIG. 1, the light source 118 can include a distal end of the fiber connection 18, or a length of fiber coupled to the distal end of the fiber connection 18. For clarity, the fiber of the fiber connection 18 is referred to as a source optical fiber 138 in the following description. It is understood that the source optical fiber 138 can be the same as the fiber connection 18, or can optionally include a separate section of fiber coupled to the distal end of the fiber connection 18.

[0033] In examples where the optical fiber 108 includes a single core 116, the source optical fiber 138 can include a single core 140. In examples where the optical fiber 108 includes multiple cores 116, the source optical fiber 138 can also include multiple cores 140. The multiple cores 140 can be arranged in a pattern similar to the pattern of the multiple cores of the optical fiber 108. As a specific example, the source optical fiber 138 and the optical fiber 108 can each include six cores arranged in a hexagonal pattern around a circumferential center of the fiber. In operation, the system 100 can simultaneously direct light from the multiple cores 140 of the source optical fiber 138 to the multiple cores of the optical fiber 108.

[0034] In examples where the optical fiber 108 includes multiple cores 116, an alternative to receiving light from multiple cores of a multi-core fiber of the fiber connection 18 is to receive light from the cores of multiple single-core fibers, such as fibers in a fiber bundle or a linear array of fibers. In some examples, the optical fiber 108 can be a multi-core optical fiber. The core 116 of the optical fiber 108 can be a first core of multiple cores of the multi-core optical fiber. The optical path 112 can be a first optical path of multiple optical paths defined by the actuatable optical element 110. Each optical path of the multiple optical paths can extend to the actuatable optical element 110 and further to the end 106 of the multi-core optical fiber. The processor 114 can operate the actuatable optical element 110 to align the optical path 112 to the core 116 by operating the actuatable optical element 110 to simultaneously align the multiple optical paths to multiple cores of the multi-core optical fiber. The light source 118 can be a first light source of multiple light sources. Each light source of the plurality of light sources can direct a corresponding light beam along a corresponding one of the plurality of optical paths to couple to a corresponding one of the cores of the multi-core optical fiber.

[0035] FIG. 2 illustrates an end view of an example light source 118 configured as a fiber bundle 200 suitable for use in the system 100 of FIG. 1. The fiber bundle 200 includes a plurality of single mode fibers 202, 204, 206, 208, 210, and 212. The plurality of single mode fibers includes corresponding cores 216, 218, 220, 222, 224, and 226, respectively. The plurality of single mode fibers surround a central fiber 214 having a core 228. In this example, the plurality of single mode fibers 202, 204, 206, 208, 210, and 212 are arranged in a regular hexagonal pattern surrounding the central fiber 214. The fiber bundle 200 is suitable for use as a light source 118 for an optical fiber 108 having a plurality of cores arranged in a similarly shaped hexagonal pattern. The fiber bundle 200 of FIG. 2 is only one example of a fiber bundle; other fiber arrangements are possible. The system 100 can further include a magnification optical system capable of providing magnification to the multiple optical paths. The magnification can be equal or substantially equal to a ratio of a spacing between adjacent cores of the multiple cores of the multi-core optical fiber to a spacing between adjacent cores of the multiple single-core optical fibers, such as within a tolerance of 1%, 5%, 10%, 20%, etc. The magnification optical system can include a source objective element 148 (described below) capable of collimating light emerging from the light source 118 to form a light beam 120, and an objective element 122 (described below) capable of focusing the light beam 120 for coupling into the optical fiber 108. A ratio of focal lengths of the source objective element 148 and the objective element 122 can be selected to be equal or substantially equal to a ratio of a spacing between adjacent cores of the multiple cores of the multi-core optical fiber of the optical fiber 108 to a spacing between adjacent cores of the multiple single-core fibers of the light source 118.

[0036] Returning to FIG. 1 , in some examples, the processor 114 can operate the actuable optical element 110 to align the optical path 112 to the core 116 by using at least the following two operations: First, the processor 114 can determine an offset between a position of a specified feature in the image 104 and a predetermined target position in the image 104. Second, the processor 114 can operate the actuable optical element 110 to reduce the offset. The processor 114 can optionally repeat these two operations during operation of the system 100 to help maintain a sufficiently high coupling efficiency to the core 116 during operation. For example, the processor 114 may determine a pixel location (e.g., a set of orthogonal position coordinates such as x and y) within the image 104 of a specified feature (e.g., the center of the circumference of the optical fiber 108), compare the determined pixel location to a specified pixel location (e.g., a set of values ​​stored in a look-up table or other suitable memory) that corresponds to a well-aligned optical fiber 108, and actuate the actuable optical element 110 to move the determined pixel location to coincide with the specified pixel location.

[0037] In some examples, the specified feature may include some or all of the periphery of the end 106 of the optical fiber 108. The core 116 may be located at a predetermined core location relative to the periphery of the optical fiber 108. The processor 114 may operate the optical element 110 operable to align the optical path 112 to the core 116 by aligning the optical path 112 to the predetermined core location. For example, in a configuration where the optical fiber 108 is a single-core fiber, the core 116 may be located at the center of the periphery of the optical fiber 108. In a configuration where the optical fiber 108 is a multi-core fiber (e.g., a fiber in which a single cladding surrounds multiple spaced-apart cores), the core 116 may be located at a specified location relative to the periphery of the optical fiber 108. For example, the optical fiber 108 may include four cores, with a central core located at the center of the periphery and three cores located at the corners of an equilateral triangle centered around the central core. As another example, the optical fiber 108 may include six cores arranged in a hexagonal pattern around a periphery center of the optical fiber 108 (e.g., the cores may be arranged at corners of a regular hexagon spaced azimuthally by 60 degrees, approximately 60 degrees, or within a tolerance of 1 degree, 2 degrees, 5 degrees, or other suitable value). As yet another example, the optical fiber 108 may include seven cores, with a central core located at the periphery center and six cores located at corners of a regular hexagon centered on the central core. Other suitable multi-core configurations may also be used.

[0038] In configurations where the optical fiber 108 includes multiple cores, the periphery of the optical fiber 108 may include optional azimuthal locating features, such as a partially flattened edge, a notch, a protrusion, or other features that may mechanically or optically indicate the azimuthal location of the core. For example, the optical fiber 108 may include a rod (not a core) that extends along the length of the optical fiber 108. Such a rod may appear as a bright dot (e.g., brighter than the area surrounding the point) or a dark dot (e.g., darker than the area surrounding the point) in the image 104 of the end 106 of the optical fiber 108. In some examples, the azimuthal locating feature may be a mechanical feature of a connection element. For example, the optical fiber 108 may be held in a ferrule and a standard optical connector. When the connector is manufactured, a particular core of the optical fiber 108 may be illuminated to align the particular core with a key of the standard optical connector.

[0039] Other designated features may be used in addition to or instead of the periphery of the end 106 of the optical fiber 108. For example, the features may include the appearance of the core 116 of the optical fiber 108 in the image 104. In some illumination configurations, the core 116 may appear as a dark spot in the image 104, which may appear darker (e.g., of greater intensity or brightness) than the area surrounding the core 116. In other illumination configurations, the core 116 may appear as a bright spot in the image 104, which may appear brighter (e.g., of greater intensity or brightness) than the area surrounding the core 116. Identifying the core 116 directly from bright and / or dark spots in an image may also be used with multicore fibers having multiple cores.

[0040] The system 100 may further include an optional illumination source 130. The illumination source 130 may illuminate the optical fiber 108 with illumination 132. The illumination 132 may have a wavelength different from the wavelength of the light beam 120. As a specific example, the wavelength of the light may be 1550 nm, and the wavelength of the illumination 132 may be in the visible spectrum, such as between 400 nm and 700 nm. Other wavelength values ​​may also be used.

[0041] For configurations that include an illumination source 130, at least a portion of the illumination 132 can be reflected or scattered from the optical fiber 108 to form the first light. In some examples, illumination 132 reflecting off the end 106 of the optical fiber 108 can generate the first light. In some examples, illumination entering a side of the optical fiber 108 and exiting the end 106 of the optical fiber 108 can form the first light.

[0042] The objective element 122 can collimate at least a portion of the first light to form the second light. In some examples, such as the configuration of FIG. 1, the objective element 122 can include an objective lens. The light path 112 can extend through the objective lens. Alternatively, the objective element 122 can include an objective mirror. FIG. 3 shows a top view of an example of a portion of the system 100 of FIG. 1, where the objective element 122 is configured as an objective mirror 302. The objective mirror 302 can have a cross section that includes a portion of a parabola. Other configurations of the objective element 122 are possible, including multiple mirrors, multiple lenses, or a combination of at least one mirror and at least one lens. Similarly, the focusing element 126 can include at least one of a focusing lens or a focusing mirror.

[0043] Returning to Figure 1, a dichroic mirror 124 can direct at least a portion of the second light away from the light path 112 to form a third light. For example, the dichroic mirror 124 can transmit light in a transmission band that includes 1550 nm. The dichroic mirror 124 can reflect light in a reflection band that includes the wavelength of the illumination 132, such as the visible spectrum. This is just one numerical example; other wavelengths and wavelength ranges can also be used.

[0044] In the configuration of FIG. 1, the dichroic mirror 124 is a long-pass dichroic mirror that can transmit relatively long wavelengths (such as those used to perform shape sensing, optionally in the infrared portion of the electromagnetic spectrum, such as 1550 nm) and reflect relatively short wavelengths (such as those used to perform imaging functions, optionally in the visible portion of the electromagnetic spectrum, such as between 400 nm and 700 nm). Alternatively, the dichroic mirror 124 can be a short-pass dichroic mirror that can transmit relatively short wavelengths (such as those used to perform imaging functions) and reflect relatively long wavelengths (such as those used to perform shape sensing). Replacing the long-pass filter with a short-pass dichroic mirror involves swapping the transmitting and reflecting arms such that the light path 112 reflects off the dichroic mirror 124 rather than transmitting through it as currently shown in FIG. 1.

[0045] The focusing element 126 can focus the third light to form the image 104 at a focal plane of the focusing element 126. An imaging array 128 can be disposed at the focal plane of the focusing element 126 and can sense the image 104. In some examples, the imaging optics can include the objective element 122, the dichroic mirror 124, the focusing element 126, and the imaging array 128. The processor 114 can receive analog and / or digital signals corresponding to the image 104 from the imaging array 128. Other suitable configurations can also be used.

[0046] In the example of FIG. 1, the actuatable optical element 110 is configured as a pivotable mirror. The pivotable mirror can include a single mirror that can pivot in two dimensions, two separate mirrors that can each pivot in one dimension, multiple mirrors that can each pivot in one or two dimensions, and other suitable configurations. In the configuration of FIG. 1, the pivotable mirror can include a reflective mirror that can pivot about a pivot point and a linear actuator 136 that can pivot the reflective mirror about the pivot point. Although the pivotable mirror is shown in FIG. 1 as pivoting in only one dimension, it will be understood that the pivotable mirror can pivot in two orthogonal dimensions using a pair of linear actuators 136. The processor 114 can control the linear actuator 136. The processor 114 can operate the actuable optical element 110 to align the optical path 112 with the core 116 of the optical fiber 108 by pivoting the rotatable mirror to steer the optical path 112 based on the position of a specified feature in the image 104.

[0047] The optical path 112 may include a fixed portion extending between the light source 118 and the actuatable optical element 110. The optical path 112 may include a movable portion extending between the actuatable optical element 110 and the end 106 of the optical fiber 108. During operation of the system 100, the movable portion of the optical path 112 may move in space while the fixed portion of the optical path 112 may remain stationary. In the configuration of Figure 1, the dichroic mirror 124, the focusing element 126, and the imaging array 128 are located in the fixed portion of the optical path 112. Other configurations may be used.

[0048] In some examples, the actuatable optical element 110 can be positioned in the optical path 112 so as to be telecentric. In the telecentric configuration, pivoting the pivotable mirror can cause a lateral translation of the optical path 112 at the end 106 of the optical fiber 108 without causing a change in the angle of the optical path 112 at the end 106 of the optical fiber 108. In some examples, placing the pivotable mirror at the back focal plane (or back focal plane) of the objective element 122 can create a telecentric condition.

[0049] 1 is just one example of a suitable actuatable optical element 110. Other suitable configurations can include a translatable optical element, such as a translatable lens or a translatable mirror. In some examples, the translatable optical element can include the objective element 122, the complete system 100, and / or the optical fiber 108.

[0050] In some examples, the system 100 can include features that allow the system 100 to operate in another environment, such as a clean room environment in an industrial example, a sterile environment in a medical example that includes sterility, etc. In some applications where a medical procedure is performed, such as where the system 100 can be reusable (e.g., can be a primary piece of equipment) and the optical fiber 108 can be replaceable (e.g., can be discarded after one use, or can be reprocessed and discarded after multiple uses, or can be reprocessed for an indefinite number of uses), the system 100 can optionally include a barrier, such as a window or optical surface. In a medical example, the barrier can meet cleanliness requirements that help provide a clean environment for certain medical procedures that do not require sterility, or can meet sterility requirements that help ensure sterility for medical procedures that do require sterility.

[0051] The window or optical surface can pass the light beam 120 to the optical fiber 108 and receive light from the optical fiber 108 without touching the optical fiber 108. In some examples, the window or optical surface can be easily cleaned between uses of the system 100 to avoid contamination of the optical fiber used in a subsequent procedure. In some examples, the objective element 122, such as an objective lens, can form part of the barrier of the system 100. For example, the objective lens can be planar convex, with the planar side optionally forming part of the sterile barrier. Other configurations can also be used. As previously mentioned, in some examples, the barrier formed by the system 100 may not be a sterile barrier in that it does not meet sterility requirements.

[0052] The system 100 may optionally further include a field aligning lens 134 disposed in the optical path 112 proximate the end 106 of the optical fiber 108. Such a field aligning lens 134 may improve coupling efficiency when the optical fiber 108 is disposed away from the central axis of the optical elements of the system 100 (e.g., off-axis performance). The field aligning lens 134 may optionally have the same focal length as the objective lens 122. The field aligning lens 134 may optionally have a diameter (e.g., clear aperture) smaller than the diameter of the objective lens 122. The field aligning lens 134 may optionally have a numerical aperture (e.g., half the diameter divided by the focal length) smaller than the numerical aperture of the objective lens 122. The field aligning lens 134 may optionally be formed as a plano-convex lens. The field aligning lens 134 may optionally have a planar surface that forms part of the sterility barrier of the system 100. Because the field aligning lens 134 can be a relatively inexpensive item, the field aligning lens 134 can be optionally configured as a replaceable (e.g., single use, multiple use, etc.) element that can be removed, reprocessed, reused, and / or discarded. Such a replaceable element can optionally be packaged together with or separately from the optical fiber 108.

[0053] In some examples, the system 100 can optionally monitor the amount of light reflected from one or more cores of the optical fiber 108. For example, in a position sensing application, the system 100 can couple light into one or more cores of the optical fiber 108, the light can reflect in varying amounts from locations along the length of the optical fiber 108, and the system 100 can analyze the reflected light, such as by optical frequency domain reflectometry (OFDR) performed by the interrogator 12, to determine a three-dimensional position of the optical fiber 108. In some examples, the analysis of the reflected light can include sensing a magnitude or amplitude of the reflected light. Such sensed magnitude or amplitude can correspond to a coupling efficiency of the light into the optical fiber 108. The system 100 can actuate the actuatable optical element 110 to raise, maximize, and / or optimize the sensed magnitude or amplitude of the reflected light from the optical fiber 108. In some examples, the system 100 can use the sensed magnitude or amplitude in coordination with the imaging techniques described above. For example, system 100 may use imaging techniques to perform initial positioning of optical path 112 near or at core 116 (e.g., as a coarse alignment procedure) and may use the detected magnitude or amplitude to more precisely position optical path 112 relative to core 116 (e.g., as a fine adjustment procedure). In some examples, system 100 may use the sensed magnitude or amplitude to position optical path 112 relative to core 116 without using the above imaging techniques.

[0054] As described above, the system 100 can illuminate the optical fiber 108 to capture the image 104 of the end 106 of the optical fiber 108. In a configuration in which the light source 118 includes a source optical fiber 138, the system 100 can optionally illuminate the end of the source optical fiber 138 and include additional optical elements to overlay a view of the end 142 of the source optical fiber 138 onto a view of the end 106 of the optical fiber 108 in the image 104. (As an alternative to, or in addition to, illuminating the end 142 of the source optical fiber 138, the controller 10 can inject illumination into the opposite end of the source optical fiber 138, which can propagate along the source optical fiber 138 and emerge from the end 142 of the source optical fiber 138. Because the illumination for imaging can use a different wavelength than the light for shape sensing, the injection of illumination can be done by wavelength division multiplexing in the controller 10.) Allowing the ends of the two fibers to be viewed simultaneously can provide additional information during the assembly and alignment phase of the system 100.

[0055] As mentioned above, a first illumination source, such as 130, can illuminate the optical fiber 108 with a first illumination, such as 132. The first illumination 132 can have a first wavelength that is different from the wavelength of the light beam 120. At least a portion of the first illumination 132 can be reflected or scattered from the optical fiber 108 to form a first light. An objective element 122, such as an objective lens or an objective mirror, can collimate at least a portion of the first light to form a second light. A second illumination source 144 can illuminate the source optical fiber 138 with a second illumination 146. The second illumination 146 can have a second wavelength that is different from the first wavelength and different from the wavelength of the light beam 120. At least a portion of the second illumination 146 can be reflected or scattered from the source optical fiber 138 to form a third light. A source objective element 148, such as a source objective lens or a source objective mirror, can collimate at least a portion of the third light to form a fourth light. A dichroic mirror such as 124 and a reflector 150, such as a retroreflector or retroreflecting prism, can superimpose the second and fourth lights to form a fifth light. In the configuration shown in FIG. 1, the dichroic mirror 124 can reflect at least a portion of the fourth light towards the reflector 150. Alternatively, the dichroic mirror 124 can be oriented to reflect at least a portion of the second light towards the reflector 150. A focusing element such as 126 can focus the fifth light to form an image 104 at a focal plane of the focusing element 126. An imaging array such as 128 located at the focal plane of the focusing element 126 can sense the image 104. Because the ends 106, 142 of the fibers can be imaged with different wavelengths of light, the processor 114 can optionally separate information from the two superimposed views as needed. Providing a superimposed view of the fiber ends 106, 142 can provide additional information during the assembly and / or alignment stages of the system 100 and / or during use of the system 100.For example, the ends of the fibers are visible in image 104 and can be used to check whether the ends of the fibers are dirty or damaged.

[0056] The optical path 112 may include an optional first pivotable element 152 that can redirect the optical path 112 within an angular range spanning one or two dimensions. The first pivotable element 152 may include a mirror on an adjustable mount that can be controllably pivoted about one, two, three, or more axes. When the pivotable element is pivoted about multiple axes, the axes may or may not intersect, may be orthogonal to each other, or may be rotationally offset by some other angle. The phrase "pivotable element" is intended to include a variety of "tip / tilt elements" that may include elements such as mirrors mounted on a tip / tilt stage. The tip / tilt stage is typically pivotable about each of two orthogonal and intersecting axes, although other configurations may be used. In the configuration of FIG. 1, the first pivotable element 152 may have a nominal angle of incidence of 45 degrees, or about 45 degrees, such that the optical path 112 is nominally redirected by 90 degrees, or about 90 degrees. The 45 degree angle of incidence is only one example of an angle of incidence; other suitable angles of incidence may be used. The first pivotable element 152 may provide an additional degree of freedom during assembly and alignment of the system 100. For example, placing the first pivotable element 152 in the optical path 112 may help to alleviate some placement tolerances on the source optical fiber 138 and may help to compensate for rotations and / or displacements of other optical elements in the optical path 112. The first pivotable element 152 may be placed in the optical path 112 between the light source 118 and the dichroic mirror 124, between the dichroic mirror 124 and the actuatable optical element 110, between the actuatable optical element 110 and the optical fiber 108, or at any other suitable location along the optical path 112.

[0057] The optical path 112 may include an optional second pivotable element 154 that may redirect the optical path 112 within an angular range spanning one or two dimensions. The second pivotable element 154 may be similar in structure and function to the first pivotable element 152. The second pivotable element 154 may be disposed in the optical path 112 between the light source 118 and the dichroic mirror 124, between the dichroic mirror 124 and the actuatable optical element 110, between the actuatable optical element 110 and the optical fiber 108, or at any other suitable location along the optical path 112. The first and second pivotable elements 152 and 154 may be disposed at different locations along the optical path 112 (e.g., may be separated longitudinally along the optical path 112). Although in FIG. 1 the second pivotable element 154 is shown adjacent to the first pivotable element 152 with no intervening optical element between them, the second pivotable element 154 can be located at any suitable location along the optical path 112, including between the beam splitters or between the beam splitter and the actuatable optical element 110. Using two pivotable elements separated along the optical path 112 can be helpful during assembly and alignment of the optical components in the system 100. For example, using two longitudinally separated pivotable elements can allow the optical path 112 to be laterally translated (e.g., moved without rotation) to a desired position or rotated in two dimensions while maintaining a fixed spatial position. As a specific example, using two pivotable elements can allow the optical path 112 to pass through the center of a lens rather than the edge of the lens to improve the optical performance of the lens.

[0058] In some instances, it may be beneficial to use one or more rotatable elements to steer the optical path 112 so that the optical fiber 108 and the source optical fiber 138 are nearly parallel (at least within a few degrees) to one another. Orienting the fibers nearly parallel is generally consistent with the use of common physical contact connectors, which typically require insertion of the fiber from the opposite side. The configuration of FIG. 1 can be modified to achieve this parallel condition by deleting one of the rotatable elements 152 or 154, adding an additional rotatable element, changing the dichroic mirror 124 to a shortpass filter instead of a longpass filter, and making other geometric changes.

[0059] Thus far, the focus has been on laterally aligning the optical path 112 to the core 116 of the optical fiber 108. Specifically, for a coordinate system (x, y, z) of the end 106 of the optical fiber 108, where z corresponds to the central axis of the optical path 112, the above discussion has been directed to aligning the optical path 112 in the x and y dimensions. For example, capturing an image 104 of the end 106 of the optical fiber 108 can provide the x and y coordinates of one or more features on the optical fiber 108, and the system 100 can actively align the optical path 112 in the x and y dimensions relative to the features in the image 104.

[0060] In some applications, active alignment in the x and y dimensions may be sufficient to achieve sufficiently high coupling to the optical fiber 108. These applications may rely on mechanical placement of the end 106 of the optical fiber 108 to be accurate enough to achieve sufficiently high coupling. For example, the optical fiber 108 may fit into a clamp that can position the end 106 of the optical fiber 108 within a specified tolerance in a specified plane (z direction) such that for any z position within the tolerance, the coupling efficiency is sufficiently high.

[0061] In other applications, the mechanical positioning in the z-direction may not be adequately accurate to achieve sufficiently high coupling. For these applications, the system 100 may further include one or more longitudinal position sensor elements. The longitudinal position sensor elements may detect a longitudinal separation (e.g., a distance measured along the optical path 112) between the focal point of the light beam 120 and the end 106 of the optical fiber 108. The longitudinal position sensor elements may be positioned at any suitable location on the fixed portion of the optical path 112.

[0062] Similarly, the system 100 may further include one or more longitudinal positioning elements. The longitudinal positioning elements may longitudinally position the focal point of the light beam 120 to reduce the longitudinal separation between the focal point and the end 106 of the optical fiber 108. The longitudinal positioning elements may be disposed at any suitable location in the fixed portion of the optical path 112. In some examples, the longitudinal positioning elements may be disposed in the optical path 112 between the longitudinal position sensor element and the optical fiber 108.

[0063] In the configuration of FIG. 1, the longitudinal position sensor element may include a beam splitter 156, such as a dichroic beam splitter, a 50-50 beam splitter, or another suitable beam splitting element. In the configuration of FIG. 1, the beam splitter 156 may be disposed along the optical path 112 between the dichroic mirror 124 and the optical fiber 108. Alternatively, the dichroic mirror 124 may be disposed along the optical path 112 between the beam splitter 156 and the optical fiber 108. Other configurations may be used, including configurations in which the functions of the transmitted and reflected paths through the beam splitter 156 may be interchanged.

[0064] The beam splitter 156 may receive the reflected and / or scattered light from the end 106 of the optical fiber 108. The beam splitter 156 may direct a portion of the reflected light to a biprism 158, a lens 160, and a sensor 162. The lens 160 may focus the light from the biprism 158 to form an image 164 on the sensor 162. The sensor 162 may be coupled to the processor 114.

[0065] The biprism 158 can provide a wedge angle between the opposing halves of the reflected light such that a specified feature in the image 164 (such as the periphery of the optical fiber 108) has a corresponding duplicate feature in the image 164. The processor 114 can further determine a longitudinal separation between the focal point and the end 106 of the optical fiber 108 based at least in part on the spacing between the specified feature and the corresponding duplicate feature. In these configurations, the spacing can be considered a focus error signal. The spacing can be compared to a specified distance that can be determined at an initial configuration of the system 100, such as at a factory during initial assembly and alignment of the system 100. If the spacing is less than the specified distance, the focal point can be on one side of the end 106 of the optical fiber 108, such as outside the optical fiber 108. If the spacing is greater than the specified distance, the focal point can be on the other side of the end 106 of the optical fiber 108, such as within the optical fiber 108.

[0066] The biprism configuration of Figure 1 is only one example of a configuration for the longitudinal position sensor element, other suitable configurations are shown in Figures 4-6 and described below.

[0067] 4 shows a top view of an example of a longitudinal position sensor element suitable for use in the system 100 of FIG. 1. The beam splitter 156 of the optical path 112 directs a light portion 402 of the light beam 120 reflected and / or scattered from the end 106 (FIG. 1) of the optical fiber 108 (FIG. 1) toward a split-field dichroic filter 404, a lens 406, and a sensor 410. A first half 404A of the split-field dichroic filter 404 can have a first spectral profile (e.g., can pass a first wavelength or a first wavelength band). A second half 404B of the split-field dichroic filter 404 can have a second spectral profile that is different from the first spectral profile (e.g., can pass a second wavelength different from the first wavelength or a second wavelength band different from the first wavelength band). The light portion 402 can form an image 408 on the sensor 410. The sensor 410 may be coupled to the processor 114 .

[0068] The portion of light 402 can have multiple wavelengths. The split-field dichroic filter 404 can be configured such that a specified feature in the image 408 has a corresponding replica feature in the image 408 at a different wavelength. The processor 114 can further determine a longitudinal separation between the focal point and the end 106 of the optical fiber 108 based at least in part on the spacing between the specified feature and the corresponding replica feature. The spacing can be compared to a specified distance, as discussed above.

[0069] Figure 5 shows a top view of another example of a longitudinal position sensor element suitable for use in the system 100 of Figure 1. The beam splitter 156 in the optical path 112 directs a light portion 502 of the light beam 120 reflected and / or scattered from the end 106 (Figure 1) of the optical fiber 108 (Figure 1) to a liquid crystal on silicon (LCOS) device 504 having a programmable aperture, a lens 506, and a sensor 510. The light portion 502 can form an image 508 on the sensor 510. The sensor 510 can be coupled to the processor 114.

[0070] The LCOS device 504 can use time multiplexing to achieve a similar splitting effect achieved by the elements shown in Figures 1 and 4. Initially, a first half 504A of the aperture of the LCOS device 504 can be reflective and a second half 504B of the aperture of the LCOS device 504 can be non-reflective. During the first time, the processor 114 can acquire a first image from the sensor 510. A second time after the first, the first half 504A of the aperture of the LCOS device 504 can be non-reflective and the second half 504B of the aperture of the LCOS device 504 can be reflective. During the second time, the processor 114 can acquire a second image from the sensor 510. The LCOS device 504 can be configured such that a designated feature in the first image has a corresponding duplicate feature in the second image. The processor 114 can further determine a longitudinal separation between the focal point and the end 106 of the optical fiber 108 based at least in part on the spacing between the designated feature and the corresponding duplicate feature. The interval can be compared to a specified distance as described above.

[0071] Figure 6 shows a top view of another example of a longitudinal position sensor element suitable for use in the system 100 of Figure 1. The beam splitter 156 in the optical path 112 directs a light portion 602 of the light beam 120 reflected and / or scattered from the end 106 (Figure 1) of the optical fiber 108 (Figure 1) to a chromatic aberration lens 606 and to a sensor 610. The light portion 602 may form an image 608 on the sensor 610. The sensor 610 may be coupled to the processor 114.

[0072] The portion of light 602 can have multiple wavelengths. Because the chromatic aberration lens 606 includes chromatic aberration, the chromatic aberration lens 606 can place light of one wavelength at a first focal point at a first focal plane and place light of a second wavelength (a second wavelength different from the first wavelength) at a second focal point at a second focal plane away from the first focal plane. Note that in the absence of chromatic aberration, which is typically the case for most well-designed lenses that operate at more than one wavelength, the first and second focal planes are often coincident or nearly coincident.

[0073] The chromatic aberration lens 606 can be configured such that a specified feature in the image 608 has a corresponding replica feature in the image 608 at different wavelengths. The processor 114 can further determine a longitudinal separation between the focal point and the end 106 of the optical fiber 108, at least in part, from a size of the specified feature in the image 608 and a size of the corresponding replica feature in the image 608. Additionally or alternatively, the processor 114 can process the image 608, such as by performing a two-dimensional fast Fourier transform on the image 608, to evaluate the sharpness of the image 608 at different wavelengths. The sharpness at different wavelengths can help determine the longitudinal separation between the focal point and the end 106 of the optical fiber 108 and / or can help determine at least a sign (e.g., positive or negative) of the longitudinal separation.

[0074] The configuration of FIG. 1 uses different beam splitters (such as dichroic mirror 124 and beam splitter 156), different focusing elements (such as focusing element 126 and lens 160), and different sensors (such as imaging array 128 and sensor 162) to perform the tasks of imaging (such as using dichroic mirror 124, focusing element 126, imaging array 128) and focus sensing (such as using beam splitter 156, lens 160, and sensor 162). Alternatively, the tasks and elements can be combined, such as by using a single beam splitter (such as dichroic mirror 124) and moving a longitudinal position sensing element (such as the biprism of FIG. 1, the split-field dichroic filter of FIG. 4, the LCOS device of FIG. 5, or the chromatic lens of FIG. 6) to be located between the focusing element 126 and the imaging array 128. Such an alternative is particularly useful when the end 106 of the optical fiber 108 is illuminated with multiple wavelengths, such as three wavelengths, that can all be located in the reflection band (or transmission band if the longpass filter in FIG. 1 is replaced with a shortpass filter) of the dichroic mirror 124.

[0075] FIG. 7 shows a plan view of the longitudinal position adjustment device elements in the system 100 of FIG. 1. In FIGS. 1 and 7, the longitudinal position adjustment elements can include a variable focus lens 166. The variable focus lens 166 can be located in the optical path 112, such as in a fixed portion of the optical path 112. The processor 114 can further cause the variable focus lens 166 to adjust the collimation of the light beam 120 to position the focal point at the end 106 of the optical fiber 108 based on the longitudinal separation between the focal point and the end 106 of the optical fiber 108 (determined by the longitudinal position sensor element).

[0076] FIG. 8 shows a plan view of an example of a longitudinal positioner element suitable for use in the system 100 of FIG. 1. Instead of using the variable focus lens 166 of FIGS. 1 and 7, the system 100 can include a linear actuator 802 for longitudinally positioning the objective element 122 relative to the end 106 of the optical fiber 108, for longitudinally positioning the entire system 100 relative to the end 106 of the optical fiber 108, for longitudinally positioning the optical fiber 108 relative to the system 100, or for controllably varying the spacing between the system 100 and the end 106 of the optical fiber 108. The processor 114 can control the linear actuator 802 based on the longitudinal separation determined by the longitudinal position sensor element. The linear actuator 802 can adjust the spacing between the focal point and the end 106 of the optical fiber 108. Other suitable actuators and actuator types can also be used.

[0077] Any or all of the longitudinal position sensor techniques (e.g., using the biprism of FIG. 1, the split field dichroic filter of FIG. 4, the LCOS device of FIG. 5, the chromatic lens of FIG. 6, or others) can be used with any or all of the longitudinal position adjustment techniques (e.g., using the variable focus lens of FIG. 1 and FIG. 7, the linear actuator of FIG. 1 and FIG. 7, or others). Additionally, any or all of the longitudinal position sensor techniques and any or all of the longitudinal position adjustment techniques can be used with any or all of the objective element configurations (e.g., objective lens or objective mirror), any or all of the optical fiber configurations (e.g., single core or multi-core), any or all of the light source configurations (e.g., single core optical fiber, multi-core optical fiber, multiple single core optical fibers, etc.), and any or all of the rotatable element configurations (including two, omitting one and including only one, omitting both and including neither, including more than two, etc.).

[0078] 9 illustrates a flow chart of an example method 900 of operating a system to direct light into an optical fiber. The system can include imaging optics, a processor, and an actuatable optical element. The actuatable optical element can define an optical path. The optical path can extend to the actuatable optical element and further to an end of the optical fiber. Method 900 can be performed in system 100 of FIG. 1 or other suitable system.

[0079] In operation 902, the system can generate an image of the end of the optical fiber using imaging optics.

[0080] In operation 904, the system may use a processor to determine a location within the image of a specified feature within the image.

[0081] In operation 906, the system, using a processor, can operate an actuatable optical element to align the optical path with the core of the optical fiber based on the location of the specified feature in the image.

[0082] In operation 908, the system can direct the light beam along an optical path to couple to a core of the optical fiber.

[0083] In some examples, the method 900 may further include, optionally, determining, with a processor, an offset between a position of the designated feature in the image and a predetermined target position in the image. The method 900 may further include, optionally, with a processor, activating an optical element operable to reduce the offset.

[0084] In some examples, the specified feature can be a periphery of an end of the optical fiber. The core can be located at a predetermined core location relative to the periphery of the optical fiber. Method 900 can optionally further include actuating, with the processor, an actuable optical element to align the optical path to the core by aligning the optical path to the predetermined core location.

[0085] In some examples, the method 900 can optionally further include illuminating the optical fiber with illumination having a wavelength different from the wavelength of the light beam.

[0086] In some examples, the method 900 may further include optionally reflecting or scattering at least a portion of the illumination from the optical fiber to form the first light. The method 900 may further include optionally collimating at least a portion of the first light with an objective element of the imaging optics to form the second light. The method 900 may further include optionally directing at least a portion of the second light away from the optical path with a dichroic mirror of the imaging optics to form a third light. The method 900 may further include optionally focusing the third light with a focusing element of the imaging optics to form an image at a focal plane of the focusing element. The method 900 may further include optionally sensing the image with an imaging array located at a focal plane of the focusing element.

[0087] In some examples, the method 900 can optionally further include detecting a longitudinal separation between the focal point and the end of the optical fiber with a longitudinal position sensor. The method 900 can optionally further include positioning the focal point with a longitudinal position adjustment device to reduce the longitudinal separation.

[0088] In some examples, the longitudinal positioning device can further create a replica feature in the image. Method 900 can optionally further include determining, by the processor, a longitudinal separation between the focal point and the end of the optical fiber based, at least in part, on a spacing or size difference between the designated feature and the corresponding replica feature.

[0089] In some examples, the longitudinal positioning device can include a variable focus lens disposed in the optical path. Method 900 can optionally further include causing the processor to adjust the collimation of the optical beam to position the focal point at the end of the optical fiber based on the longitudinal separation between the focal point and the end of the optical fiber.

[0090] In some examples, the longitudinal positioning device can include an actuatable objective lens capable of directing the optical path to an end of the optical fiber. Method 900 can optionally further include moving, by the processor, the actuatable objective lens to position the focal point at the end of the optical fiber based on the longitudinal separation between the focal point and the end of the optical fiber.

[0091] 10 illustrates a flow chart of an example of another method 1000 for operating a system to direct light into an optical fiber. The optical fiber can include a core. The system can include imaging optics, a first actuatable optical element, and a second actuatable optical element. The method 1000 can be performed in the system 100 of FIG. 1 or other suitable system.

[0092] In operation 1002, the system can generate a first image of the end of the optical fiber using imaging optics.

[0093] In operation 1004, the system can determine a two-dimensional lateral position of the core on the end of the optical fiber from the first image.

[0094] In operation 1006, the system can actuate the first actuatable optical element to laterally align the optical path to the core based on the two-dimensional lateral position. Method 1000 can repeat operations 1002 through 1006 as necessary until the system can determine that the optical path is sufficiently aligned to the core. Once the system completes operation 1006, the optical path is considered to be laterally aligned with respect to the core (e.g., aligned in an xy plane orthogonal to the optical path at the end of the optical fiber).

[0095] In operation 1008, the system can generate a second image of the end of the optical fiber using the imaging optics.

[0096] In operation 1010, the system can determine from the second image a longitudinal position of the core on the end of the optical fiber.

[0097] In operation 1012, the system can actuate the second actuable optical element to focus the light path at the end of the optical fiber based on the longitudinal position. Method 1000 can repeat operations 1008 through 1006 as necessary until the system can determine that the focal point is sufficiently close to the end of the optical fiber. Once the system completes operation 1012, the focal point of the light path is considered to be longitudinally aligned with the end of the fiber (e.g., aligned in a z-direction parallel to the light path at the end of the optical fiber).

[0098] In some examples, the first actuatable optical element can include a pivotable mirror. Method 1000 can optionally further include directing the light beam along an optical path to couple to a core of the optical fiber. Method 1000 can optionally further include repeatedly performing at least the following three operations: First, the system can dither an angular position of the pivotable mirror in two dimensions. Second, the system can sense an amount of light reflected from the core. In some examples, the second operation can be performed by an interrogator of a controller coupled to the system. Third, the system can adjust an angular position of the pivotable mirror to increase an amount of light reflected from the core.

[0099] In some examples, at least one of the controllers or processors included in the system can take measurements at multiple angular positions (x, y) and / or multiple focal positions (z) of the rotatable mirror, measure the amount of light reflected from the core at each of the angular and / or focal positions, fit one or more curves to the measured amounts of light, and adjust the angular position and / or focus adjustment of the rotatable mirror to correspond to a local maximum of the one or more curves.

[0100] In some examples, the controller 10 can measure the reflected signal using OFDR at each position of the mirror search pattern. Various data processing techniques can be used to evaluate where optimal fiber coupling is achieved (e.g., what separation between the focal point of the light beam 120 and the end 106 of the optical fiber 108 provides the maximum amount of light returning from the optical fiber 108 and therefore the highest coupling efficiency into the optical fiber 108).

[0101] In one technique, the controller 10 can sum the reflection amplitudes of the raw frequency domain data and report the total reflection amplitude. While such techniques are effective, it is also possible to filter out additional relatively large background signals. The techniques described below can filter out these relatively large background signals, thereby increasing the signal-to-noise ratio of the coupling efficiency measurement.

[0102] In another technique, the controller 10 can select a section of the time domain or optical delay domain reflection amplitudes that represent a section of the optical fiber 108 that has a grating in its core and sum over the selected section. For example, in the time domain, reflections arising from optical interfaces (such as glass-air interfaces, such as lenses or window faces) appear as peaks along the horizontal axis because the horizontal axis corresponds to the round trip propagation time. The controller 10 can thus effectively ignore the peaks arising from these optical interfaces and analyze data arising from light reflected from positions along the length of the optical fiber 108. The controller 10 can sum the reflection amplitudes for data resulting from reflection(s) along the length of the optical fiber 108 and exclude data resulting from reflection(s) from the end 106 of the optical fiber 108 or other optical surfaces. Selecting which data to use in this manner can increase sensitivity compared to using all of the light returning to the controller 10. For example, selecting which data to use in this manner can indicate a higher signal (e.g., above noise level) only when light is coupled into the optical fiber 108 and is reflected off the grating structure along the length of the optical fiber 108.

[0103] In yet another technique, the controller 10 can select the entire area of ​​the optical fiber 108 in the time domain where the grating is present, convert the data to the frequency domain, such as by a Fast Fourier Transform, and sum the amplitude only in the spectral region where the grating reflects. Processing the amplitude data in this manner can help reduce or eliminate low level broadband reflection amplitudes that may arise from connector reflections or other optical interfaces.

[0104] A computer readable medium can store instructions that, when executed by a processor of a system for directing light to an optical fiber, cause the processor to perform operations. The system can include an actuatable optical element that defines an optical path. The optical path can extend to the actuatable optical element and can further extend to an end of the optical fiber. The operations can include at least four operations: First, the system can generate an image of the end of the optical fiber using imaging optics. Second, the system can determine from the image a location within the image of a designated feature within the image. Third, the system can operate the actuatable optical element to align the optical path with a core of the optical fiber based on the location of the designated feature within the image. Fourth, the system can direct a light beam along the optical path to couple to the core of the optical fiber.

[0105] Although various aspects of the present invention have been described with reference to preferred embodiments, it will be understood that the invention is entitled to full protection within the full scope of the appended claims.

Claims

1. 1. A system for directing light emitted by a first optical core of a first light source to a second optical core of a sensing optical fiber, comprising: a first objective element and a second objective element for directing the light from the first optical core along respective optical paths; an actuatable optical element disposed between the first objective element and the second objective element; a second light source configured to direct illumination towards the end of the sensing optical fiber such that the illumination is reflected or scattered from the end of the sensing optical fiber as reflected or scattered illumination, the illumination having an illumination wavelength different from a wavelength of the light emitted by the first optical core; a focusing element and an imaging array configured to form an image of the edge from the reflected or scattered illumination; 1. A control system having one or more processors, comprising: Determining the location of a specified feature within the image; and causing actuation of the actuatable optical elements to align the optical paths with the respective second optical cores based on the positions. a control system configured to perform operations including: The system has:

2. The first light source comprises: an optical fiber having the first optical core and a cladding surrounding the first optical core; or a bundle of optical fibers, each optical fiber of the bundle having an optical core of the first optical core; The system of claim 1 .

3. and a physical barrier, the physical barrier having a window configured to separate the second objective element from the sensing optical fiber.

3. A system according to claim 1 or 2.

4. The specified features are: a periphery of the end of the sensing optical fiber; azimuth location features on the periphery of said end; and a core of the second optical core; The present invention includes embodiments selected from the group consisting of: A system according to any one of claims 1 to 3.

5. the first objective element has a first objective lens and the second objective element has a second objective lens; or The first objective element has a first parabolic mirror, and the second objective element has a second parabolic mirror. A system according to any one of claims 1 to 4.

6. The actuatable optical element comprises a pivotable mirror. A system according to any one of claims 1 to 5.

7. the rotatable mirror is positioned telecentrically with respect to the second objective element such that pivoting the rotatable mirror causes a lateral translation of the optical path at the end of the sensing optical fiber without causing an angular change of the optical path at the end of the sensing optical fiber. The system of claim 6.

8. Causing the actuation of the actuatable optical element comprises: determining an offset between the location of the designated feature in the image and a predetermined target location; and causing the actuation based on the offset. A system according to any preceding claim.

9. the reflected or scattered illumination includes illumination that propagates along the optical path and is collimated by the second objective element into collimated reflected or scattered illumination; the system further comprising a dichroic mirror disposed in the optical path between the first objective element and the second objective element, the collimated reflected or scattered illumination being redirected by the dichroic mirror away from the optical path as redirected reflected or scattered illumination; the focusing element is disposed in a path of the redirected reflected or scattered illumination and configured to focus the redirected illumination onto the imaging array. A system according to any preceding claim.

10. the dichroic mirror is disposed between the actuatable optical element and the first objective element; Causing the actuation of the actuatable optical elements to align the optical paths with the respective second optical cores comprises: determining an offset between the location of the designated feature in the image and a predetermined target location in the image; and causing said actuation to reduce said offset; The system of claim 9.

11. the first light source includes a light source optical fiber, the light source optical fiber including the first optical core; the second light source is a first illumination source and the illumination wavelength is a first illumination wavelength; the system further includes a third light source configured to direct a second illumination at an end of the source optical fiber at a second illumination wavelength, the second illumination being reflected or scattered from the end of the source optical fiber in a direction along the optical path, collimated by the first objective element, and then redirected away from the optical path by a dichroic mirror to become a redirected second illumination; the second illumination wavelength is different from the first illumination wavelength and different from the wavelength of the light emitted by the first optical core; the system further comprising a reflector configured to reflect the redirected second illumination towards the focusing element to focus the reflected redirected second illumination onto the imaging array such that an image of the end of the source optical fiber is overlaid with the image of the end of the sensing optical fiber. A system according to any one of claims 1 to 10.

12. The system further includes an interrogator for analyzing reflected light that is reflected along a length of the second optical core of the sensing optical fiber and coupled back into the first optical core of the first light source; the interrogator is configured to determine a magnitude or amplitude of the reflected light; the operations further include, after an initial alignment of the optical path with each of the second optical cores based on the location of the designated feature in the image, causing a further actuation of the actuatable optical element based on the magnitude or amplitude of the reflected light to further align the optical path with each of the second optical cores. A system according to any one of claims 1 to 11.

13. a sensor for sensing a longitudinal separation between the end of the sensing optical fiber and a focal point of the light coupled into each of the first to second optical cores based on a second image of the reflected or scattered illumination; and a position adjuster configured to adjust a position of the focal spot to reduce the longitudinal separation. A system according to any preceding claim.

14. the position adjuster comprises a variable focus lens disposed in the optical path, and the action further comprises adjusting the position of the focal point by causing the variable focus lens to adjust collimation of the light; or the position adjuster has an actuator configured to move the second objective element, and the operation further comprises adjusting the position of the focal spot by having the actuator move the second objective element; or the sensor has a biprism configured to impart a wedge angle between opposing halves of the reflected or scattered illumination to generate replica features in the second image, the operations further including determining the longitudinal separation based on a spacing between the replica features; or the second light source is configured to illuminate the end of the sensing optical fiber at a plurality of wavelengths, and the sensor is configured to have a split-field dichroic filter or a chromatic aberration lens and generate replica features at two different wavelengths in the second image, and the operations further include determining the longitudinal separation based on a spacing between the replica features. The system of claim 13.

15. 1. A system for directing light emitted by a first optical core of a multi-core optical fiber to a second optical core of a sensing optical fiber, comprising: a first objective element and a second objective element for directing the light from the first optical core along respective optical paths; an actuatable optical element disposed between the first objective element and the second objective element; a second light source configured to direct illumination towards the end of the sensing optical fiber such that illumination is reflected or scattered from the end of the sensing optical fiber, propagates along the optical path, and is collimated by the second objective element into collimated reflected or scattered illumination, the illumination having an illumination wavelength different from a wavelength of the light emitted by the first optical core; a dichroic mirror disposed in the optical path between the first objective element and the second objective element and configured to redirect the collimated reflected or scattered illumination away from the optical path as redirected reflected or scattered illumination; a focusing element and an imaging array disposed in a path of the redirected, reflected or scattered illumination and configured to form an image of the end of the sensing optical fiber from the redirected, reflected or scattered illumination; 1. A control system having one or more processors, comprising: Determining the location of a specified feature within the image; and causing actuation of the actuatable optical elements to align the optical paths with the respective second optical cores based on the positions. a control system configured to perform operations including: The system has:

16. the dichroic mirror is disposed between the actuatable optical element and the first objective element; Causing the actuation of the actuatable optical elements to align the optical paths with the respective second optical cores comprises: determining an offset between the location of the designated feature in the image and a predetermined target location in the image; and causing said actuation to reduce said offset; The system of claim 15.

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