Method and system for reconnecting optical fibers

Abstract

The invention relates to a method of reconnecting a first optical fiber (12) and a second optical fiber (34), each having a plurality of outer cores, the method comprising: (a) positioning a first end of the first optical fiber (12) and a second end of the second optical fiber (34) in proximity to each other so as to be aligned with each other along a longitudinal axis of the first and second ends at a current connection position, the current connection position comprising a current connection orientation in which a current relative angle of rotation between the first end and the second end about the longitudinal axis is unknown relative to a relative angle of rotation between the first end and the second end in a registered connection orientation, the registered connection orientation being determined relative to a coordinate system during a previous connection of the first optical fiber (12) and the second optical fiber (34); (b) optically interrogating the outer cores of the first and second optical fibers (12, 34) through the current connection position to receive optical signals from the outer cores; (c) modifying the registered connection orientation in dependence on the optical interrogation of the outer cores so that the first and second optical fibers in the current connection orientation are correctly registered relative to the coordinate system, the current connection orientation comprising a current relative angle of rotation between the first and second ends about the longitudinal axis.

Description

Technical Field

[0001] This invention generally relates to the field of optical shape sensing (OSS) using fiber optic sensors (also known as FORS (Fiber Optic True Shape)). In particular, this invention relates to a method for reconnecting optical fibers to each other. Reconnecting the fibers may be necessary in processes using FORS. This invention also relates to a system for reconstructing the shape of a fiber optic sensor. Background Technology

[0002] While this specification relates to the use of FORS in the medical or surgical fields, it should be understood that the invention is not limited thereto.

[0003] In the medical field, there is a clear and ongoing trend to replace conventional surgical procedures with minimally invasive interventions. In these interventions, medical devices, such as guidewires, catheters, endoscopes, and needles, are inserted into the body through small incisions, minimizing shock and reducing complications and side effects for the patient. Physicians can use several visualization techniques to navigate these medical devices within the body.

[0004] In many procedures, X-ray imaging is currently the gold standard for providing real-time monitoring of equipment. However, this imaging technique exposes patients and medical teams to harmful ionizing radiation. Furthermore, it provides only a two-dimensional projection. This projection lacks crucial information about the three-dimensional shape of the medical instrument, such as its orientation and orientation relative to the patient's anatomy. Additional information about the shape of the device would greatly assist physicians in navigating through the body and could reduce procedure time.

[0005] Several non-imaging tracking techniques exist that can determine the position and orientation of a device. Such tracking systems can be based on sensing of electromagnetic, acoustic, impedance, and optical techniques, and can use principles such as signal strength (and attenuation), signal phase / frequency shift, and / or time of flight to perform triangulation of the sensor in three-dimensional space.

[0006] Fiber True Shape Reconstruction (FORS) is one of these tracking techniques. In FORS, the geometric changes of the device are encoded into an optical field that propagates through a special type of optical fiber integrated into the device. Optical interrogation of this fiber provides the information needed to reconstruct, in principle, the three-dimensional shape of the entire fiber (and therefore the three-dimensional shape of the device) in real time. Given a suitable reference frame (coordinate system), one can now know the exact orientation and position of the complete medical device in real time.

[0007] The optical fiber (FORS sensor) used to determine the shape of the device typically comprises multiple optical cores, such as a central core and multiple outer cores, which can be spiraled around the central core along the length of the fiber. For example, the optical fiber may include four cores, one central core and three outer cores, which can be nominally positioned 120° apart from each other at a fixed distance from the central core. For the purposes of this invention, the number of outer cores should be equal to or greater than two.

[0008] To establish a functional connection between a first optical fiber (e.g., an optical fiber integrated into a medical device) and a second optical fiber (e.g., an optical fiber integrated into a connector cable connected to an optical interrogator), aligning the outer cores of the two fibers is crucial. A common way to achieve this alignment is to assemble the two fibers into an optical fiber connector and mate them within a mating sleeve. Low-tolerance elements in the connector, such as ceramic ferrules, ensure that the two fibers are centered within the mating sleeve. The connector key defines the angular alignment between the two fibers.

[0009] For certain designs in medical devices, such as guidewires, especially reverse-loaded guidewires, where the outer diameter is typically no more than one millimeter, robust connector keys are difficult to manufacture. In such cases, alternative alignment methods are needed to ensure proper alignment between the outer cores of the two optical fibers.

[0010] In FORS (Forward Orthogonal System), the reconstructed shape of the fiber optic sensor (and thus the reconstructed shape of the medical device to which the fiber optic sensor is integrated) is typically displayed in an associated coordinate system, such as the coordinate system that matches the operating room using FORS, for example, the coordinate system linked to the fixed operating table or the X-ray system. For this purpose, the FORS sensor is typically registered to the associated coordinate system during setup using, for example, one or more X-ray images. This registration can be a time-consuming and lengthy process. Therefore, it is desirable to maintain this registration once it is completed throughout the surgical procedure. However, during the medical procedure, the FORS guidewire may need to be disconnected from and reconnected to the optical interrogator several times. This is particularly true for reversibly loadable FORS guidewires, for which the conventional approach of fixing the starting position (the position of the fiber optic sensor where shape reconstruction begins) cannot be used due to strict limitations on the outer diameter of the medical device. When such a device (e.g., the guidewire) is disconnected to slide the treatment device onto the proximal end of the guidewire, the need for re-registration after reconnecting the fiber optic sensor to the optical connector connected to the interrogator is undesirable, as this will cause delays in the procedure.

[0011] When reconnecting two optical fibers, such as an fiber integrated into a device and an fiber integrated into a patch cord, the cores of both fibers need to be aligned with high accuracy. It is known to measure reflectivity to ensure such good alignment, as described in US 2019 / 0391341 A1. It is also known to use a recalibrable / reassignable calibration dataset for each outer core to ensure good reconnection, involving comparing the measured optical response of the corresponding interrogated fiber core with the calibration dataset of the corresponding fiber core of the patch cord, as disclosed in WO 2017 / 182535 A1.

[0012] However, there is still a need for a method that helps users reconnect two optical fibers, minimizes the number of required registration steps, and improves workflows, for example, in operating rooms. Summary of the Invention

[0013] The purpose of this invention is to provide an improved method for reconnecting a first optical fiber to a second optical fiber.

[0014] Another object of the present invention is to provide a method for reconnecting optical fibers to each other without requiring re-registration of the fibers in the relevant coordinate system.

[0015] Another object of the present invention is to provide a method for reconnecting optical fibers, which is highly suitable for having a reversibly loaded guidewire with an integrated optical fiber.

[0016] Another object of the present invention is to provide a system that can utilize the method according to the present invention.

[0017] According to a first aspect of the present invention, a method for reconnecting a first optical fiber to a second optical fiber is provided, wherein the first optical fiber and the second optical fiber each have a plurality of outer cores, the method comprising:

[0018] (a) Positioning the first end of the first optical fiber and the second end of the second optical fiber close to each other so that they are aligned with each other along the longitudinal axis of the first and second ends at a current connection position, the current connection position including a current connection orientation in which the current relative rotation angle between the first and second ends about the longitudinal axis is unknown relative to the relative rotation angle between the first and second ends in a registration connection position including a registration connection orientation that has been determined relative to a coordinate system during a previous connection of the first and second optical fibers.

[0019] (b) Optically interrogating the outer cores of the first and second optical fibers at the current connection location to receive optical signals from the outer cores.

[0020] (c) Modify the registration connection orientation based on the optical interrogation of the outer core such that the first and second optical fibers in the current connection orientation are correctly registered with respect to the coordinate system, the current connection orientation including the current relative rotation angle between the first end and the second end about the longitudinal axis.

[0021] The method according to the invention facilitates the reconnection of two optical fibers. In particular, the method eliminates the need for re-registration of the optical fibers relative to a relevant coordinate system. When the first optical fiber is reconnected to the second optical fiber, the mutual ends of the first and second optical fibers are positioned close to each other. Although the positions of the optical fibers along the longitudinal axis and in two directions perpendicular to the longitudinal axis, as well as their orientation about two axes perpendicular to the longitudinal axis, can be mechanically defined with high precision, the remaining degree of freedom, namely the current relative rotation angle between the first and second ends about the longitudinal axis, is unknown, at least not with the necessary accuracy. The method according to the invention allows the relative rotation angle between the first and second ends in the current connection direction to be determined by optically interrogating the outer core of the first and second optical fibers through the current connection position to receive optical signals from the outer core. Therefore, the method according to the invention utilizes optical measurements of the two optical fibers through the current connection position. The result of this measurement is then used to modify a previously determined registration connection orientation, for example, during the setup of the system, relative to the coordinate system in the case of the previous connection of the optical fibers, such that the first and second optical fibers in the current connection orientation, including the current relative rotation angle between the first and second ends about the longitudinal axis, are correctly registered relative to that coordinate system. During optical interrogation of the outer cores of the first and second optical fibers, the two fibers can be rotated relative to each other (e.g., by rotating the distal fiber relative to the proximal fiber) until the optical signal received from the outer core is optimal. However, such rotation will typically not be precise enough that the relative rotation angle between the fiber ends will be the same as the relative rotation angle in the previous connection that forms the basis of the registration. Performing optical measurements by optically interrogating the outer cores of the two fibers allows for much more accurate results from which the relative rotation angle between the ends of the two fibers can be derived. These measurements can now be used to modify the registration alignment of the two fibers about the longitudinal axis, which has been obtained from the previous connection and registration with the relevant coordinate system. In subsequent shape reconstruction, the previous registration, such as the initial registration, can be further used, but it is now corrected with the current actual relative rotation angle obtained from the optical interrogation. This eliminates the need for re-registering the fibers in the relevant coordinate system.

[0022] To implement the method according to the invention, it is not necessary to use a connector with a connector key to define the rotational alignment of the two optical fibers about the longitudinal axis. Therefore, the method according to the invention is highly suitable for reversibly loaded guidewires with integrated optical fibers.

[0023] Preferred embodiments of the invention are defined in the dependent claims and as described in this disclosure.

[0024] In an embodiment, the method may further include instructing the user that the first end and the second end should be rotated relative to each other about the longitudinal axis in order to optimize the strength of the received signal.

[0025] When the user attempts to refine the relative rotational position of the two optical fibers about the longitudinal axis to obtain a better signal, he or she is unaware of which side the current alignment is on. Instead, by instructing the user on the direction in which the first and second parts should rotate relative to each other about the longitudinal axis, compared to simply treating signal strength as a function of orientation, a more intuitive and therefore faster feedback for aligning the outer core is enabled during reconnection. Thus, faster alignment can be achieved, which is advantageous given the duration of the intervention and the number of device exchanges required for a complex process.

[0026] The indication can be provided to the user as a visual indication on a display or graphical user interface. The indication can also be provided as an acoustic indication, such as a sound with varying loudness or frequency, indicating the direction in which the optical fibers should rotate relative to each other.

[0027] It should be understood that rotation of the first and second ends relative to each other includes rotating only the first end, rotating only the second end, and rotating both the first and second ends.

[0028] In an embodiment, step (c) may include determining the current relative rotation angle between the first end and the second end based on the optical interrogation of the outer core, and using the determined current relative rotation angle to correct the registration connection orientation.

[0029] Using optical measurements obtained from optical interrogation of the outer cores of the two optical fibers, the current relative rotation angle between the ends of the optical fibers can be determined very accurately. Knowing the current relative rotation angle simplifies modifications to the registration connection orientation. Modifications can be performed using the difference between the current rotation angle and the rotation angle in the previous connection.

[0030] In an embodiment, step (b) may include deriving the amount of light selected from the group consisting of: insertion loss, transmission, and reflection at the current connection location for each of the outer cores, based on the optical signal.

[0031] Optical interrogation from the outer core of the optical fiber allows for the measurement of the light quantity indicated above with very high accuracy. Insertion loss is a measure of the loss of optical signal power at the connection point and can be expressed in dB (decibels). Insertion loss is related to the relative rotation angle between the first and second ends about the longitudinal axis. By measuring the insertion loss at the current connection point, this relative rotation angle can be determined in a simple manner, as will be described in more detail herein.

[0032] In conjunction with previous embodiments, the method may further include determining the current relative rotation angle between the first end and the second end based on the light intensity for each fiber core, and on the storage characteristics specific to the two fibers to be reconnected.

[0033] Preferably, the stored characteristics can be obtained from optical measurements of the amount of light relative to multiple rotation angles between the first and second ends during a previous connection of the first and second optical fibers.

[0034] During the initial (or prior) connection (and before registration), the two optical fibers can be rotated relative to each other, and the amount of light in the outer core, such as insertion loss, is continuously determined. Using these data points, the angular position of the outer core of the first optical fiber relative to the angular position of the outer core of the second optical fiber can be estimated, and these relative angular positions can be used as stored characteristics. When the optical fibers are aligned sufficiently, they can be left in that orientation, and the registration step can then be performed. During the reconnection phase, the previously stored characteristics can be used, and the amount of light (e.g., insertion loss) is measured during the reconnection to determine the relative orientation (relative rotation angle). One can even rotate the two optical fibers relative to each other again during the reconnection phase, thereby re-determining the relative angular position of the outer core, or combine these measurements with those taken during the initial connection to refine the relative angular position.

[0035] Alternatively, the storage characteristics can be obtained from measurements taken during the early stages of the manufacturing process of the optical fiber, such as splicing wires and sensors equipped with the optical fiber.

[0036] In order to use the previous registration, such as the initial registration, of the fiber connection in the relevant coordinate system, it is important to know the current relative rotation angle at the current connection position relative to the previous connection position used for registration. Therefore, the determination (e.g., calculation) of the current relative rotation angle is perfectly tailored to the alignment of the fiber on which the (initial) registration is based, based on the storage characteristics obtained from measurements of (the same) light quantity during the previous connection of the fiber.

[0037] Furthermore, compared to re-determining this characteristic during the reconnection of the two optical fibers, using storage characteristics specific to the actual combination of the two particular optical fibers reduces the computation time and expense of determining the current relative rotation angle. Additionally, it increases the accuracy of the difference between the current alignment and the previous alignment.

[0038] The stored characteristics may include the deviation of the angular position of the outer core of the first optical fiber relative to the angular position of the outer core of the second optical fiber.

[0039] Such deviations in the angular position of the outer core between the two optical fibers may be caused by tolerances in the manufacturing process of the optical fibers. These deviations are specific to the actual two optical fibers to be connected and reconnected during the process. Taking these deviations into account when determining the relative rotation angle between the optical fibers increases the accuracy of the measurement results for determining the amount of light at that relative rotation angle.

[0040] When considering two optical fibers, each with N outer cores, there are N possible combinations of core-to-core configurations when reconnecting the two fibers. For example, if each of the two fibers has three outer cores, there are three possible combinations of the outer cores of the first fiber and the second fiber. In the previous connection, the fibers were connected in a core-to-core configuration. When this core-to-core configuration is also used for the reconnection of the two fibers, it is sufficient to know, for that particular core-to-core configuration, the deviation between the angular positions of the outer cores of the first fiber and the second fiber. Therefore, in this embodiment, computational overhead and computation time can be reduced.

[0041] However, it is also possible that, for all possible combinations of the outer core of the first optical fiber and the outer core of the second optical fiber, the stored characteristics include the deviation between the angular positions of the outer core of the first optical fiber and the outer core of the second optical fiber.

[0042] In this case, the stored characteristics include N parameters. An advantage of this embodiment is that when reconnecting the two optical fibers, it is not necessary for the reconnected fiber core-to-fiber configuration to be the same as in the previous connection. Since the user does not need to pay attention to the alignment of the same fiber cores in the first fiber with the same fiber cores in the previous connection, the reconnection and alignment of the two optical fibers are further simplified.

[0043] In either of the two embodiments described above, it is advantageous if the method further includes identifying the current combination of the outer core of the first optical fiber and the outer core of the second optical fiber.

[0044] Identification of the current combination of the outer cores of the two optical fibers can be performed as described in WO 2017 / 182535 A1, which discloses identifying the core-to-core configuration by comparing the measured optical response of the interrogated fiber core with a calibration dataset of the corresponding core of the other optical fiber.

[0045] In an embodiment, the method may further include instructing a user to rotate the first optical fiber and the second optical fiber relative to each other about the longitudinal axis until the same cores of the first optical fiber and the second optical fiber are optically connected to each other, as in a previous connection between the first optical fiber and the second optical fiber.

[0046] This embodiment is particularly advantageous in the context of the above embodiment, according to which the stored characteristics include only the deviation between the angular positions of the outer cores of the two optical fibers in this combination, for the outer cores already in optical communication during the previous connection. Instructing the user how far to rotate the first and second optical fibers relative to each other about the longitudinal axis to achieve the core-to-core configuration of the previous connection also helps the user find the “correct” (previously) core-to-core configuration as quickly as possible.

[0047] Furthermore, the indication can be provided as a visual indication on a display or graphical user interface. The indication can also be provided as an acoustic indication, such as a sound with varying loudness or frequency, indicating the direction in which the optical fibers will rotate relative to each other.

[0048] As mentioned above, if the stored characteristics include the deviation between the angular positions of the outer cores of the two fibers for all possible combinations or core-to-core configurations, the user does not need to notice the previously connected core-to-core configuration. This also speeds up the alignment process and avoids large rotational movement of one or both of the two fibers, and thus reduces the risk of wear on the connectors used to connect the two fibers.

[0049] In an embodiment, the registration connection position can be registered relative to the activation position, and the second optical fiber is connected to the first optical fiber directly at the activation position or at a distance away from the activation position.

[0050] The starting position of the FORS system is the location where shape reconstruction of the FORS system begins. Conventionally, this starting position is mechanically fixed away from any optical connection. In such a configuration, the optical fibers can be connected and disconnected while the starting position is held in a mechanically stable starting fixation device. However, such a configuration is not possible when using a reversibly loaded guidewire integrated with the optical fiber. In this embodiment, the connection between the two optical fibers is directly on the distal side of the starting position or at a distance from the starting position, thus enabling the use of reversible loading. Another advantage of this embodiment is that the process of connecting, disconnecting, and reconnecting the two optical fibers can be performed closer to the patient, which is an improvement in surgical procedures, especially in complex surgical procedures where connecting, disconnecting, and reconnecting must be repeatedly performed.

[0051] In one embodiment, one of the first optical fiber and the second optical fiber is integrated in the device, and the method may further include reconstructing the shape of the device using the registration position modified during the reconnection of the first optical fiber and the second optical fiber.

[0052] Re-registration of the device is not required because the registration performed in the previous connection of the two optical fibers can be further used after the reconnection of the optical fibers, and the registration is modified by the current relative rotation angle between the two optical fibers. Integration into the device includes both cases where the optical fibers extend through the interior of the device and cases where the optical fibers extend along the exterior of the device.

[0053] According to a second aspect of the present invention, a system is provided, comprising:

[0054] A first optical fiber and a second optical fiber, each having multiple outer cores, are positioned such that a first end of the first optical fiber and a second end of the second optical fiber are aligned with each other along a longitudinal axis at a current connection position including a current connection orientation. The current relative rotation angle between the first and second ends about the longitudinal axis is unknown relative to the relative rotation angle between the first and second ends in a registration connection orientation determined relative to a coordinate system during a previous connection of the first and second optical fibers.

[0055] An optical interrogator is configured to interrogate the outer cores of the first and second optical fibers at the current connection position to receive optical signals from the outer cores.

[0056] A circuit configured to modify the registration connection orientation based on the optical interrogation of the outer core, such that the first and second optical fibers in the current connection orientation are correctly registered relative to the coordinate system, the current connection orientation including the current relative rotation angle between the first and second ends about the longitudinal axis.

[0057] In another aspect of the invention, a computer program including program code modules is provided, the program code modules being used to cause the system of the second aspect to perform the steps of the method according to the first aspect.

[0058] It should be understood that the claimed system and computer program have preferred embodiments similar to and / or identical to the claimed method, particularly as defined in the dependent claims and as disclosed herein. Attached Figure Description

[0059] These and other aspects of the invention will become apparent and will be illustrated with reference to the embodiments described below. In the following figures:

[0060] Figure 1 An embodiment of a system suitable for FORS is shown;

[0061] Figure 2 An example length of an optical fiber is shown;

[0062] Figure 3 The fiber core geometry of a typical FORS sensor multi-core fiber in a coordinate system is shown, where the origin is placed at the mechanical center of the fiber.

[0063] Figure 4 It shows Figure 1 A simplified schematic diagram of the system, with enlarged details;

[0064] Figure 5 The insertion loss curves for light transmission from the first fiber to the second fiber for each core of the fiber are shown as a function of the relative rotation angle between the first and second fibers at the connection point.

[0065] Figure 6 This shows the combination into vectors and plotted in a 3D graph. Figure 5 The insertion loss curve in the figure;

[0066] Figure 7 A flowchart illustrating an embodiment of a method for reconnecting two optical fibers to each other according to a first embodiment is shown;

[0067] Figure 8The simulation of the insertion loss curve of light transmission from the first fiber to the second fiber connected to the first fiber as a function of the relative rotation angle between the two fibers is shown, where all possible core-to-core configurations of the two fibers are considered.

[0068] Figure 9 A flowchart illustrating a method for reconnecting two optical fibers to each other according to a second embodiment is shown;

[0069] Figure 10 The diagram illustrates examples of possible user feedback at different stages of the alignment of two optical fibers relative to each other, with and without embodiments of the present invention; and

[0070] Figure 11 a) through c) illustrate schematic diagrams of three possible configurations of the FORS setup, including an interrogator, a patch cord equipped with multi-fiber optic cables, a sensor equipped with multi-fiber optic cables, and an activation area, wherein... Figure 11 a) shows the standard settings, and Figure 11 b) and 11c) illustrate embodiments using the setup of the present invention. Detailed Implementation

[0071] Before describing the invention in detail, some introductory explanations of FORS will be given to facilitate understanding of the invention.

[0072] Figure 1 The components of a system 10 configured to sense and reconstruct the shape of the fiber optic sensor 12 are schematically shown. The system 10 may also be referred to as the FORS system 10.

[0073] System 10 can be configured as a multi-channel optical frequency domain back reflection (OFDR) and distributed strain sensing system for interrogating fiber optic sensor 12 and reconstructing the shape of fiber optic 12. Fiber optic 12 may embed multiple fiber cores 14, 16, 18, and 20 therein; in this example, it has four cores: a central core 16 and three outer cores 14, 18, and 20. It should be understood that the invention is not limited to the use of four-core fibers, but can also be used with fibers having fewer or more than four cores.

[0074] Figure 2 A length of fiber cores 14, 16, 18, and 20 is shown, wherein the outer cores 14, 18, and 20 are spirally arranged around the central core. The outer cores are spaced at an angle relative to each other around the longitudinal central axis of fiber 12. The central core 16 can be positioned on the longitudinal central axis, subject to some tolerances due to the fiber manufacturing process. Depending on the number of four cores with three outer cores in this example, the angular spacing between adjacent cores is typically 120°.

[0075] Refer again Figure 1The FORS system 10 may include an optical shape sensing console 21. The optical shape sensing console 21 is also referred to herein as an interrogator for optically interrogating the fiber optic cable 12. The system 10 may be adapted to perform methods according to the principles of this disclosure, which will be described below.

[0076] The shape sensing console 21 may include a tunable light source 22 that can sweep across a series of optical frequencies. Light emitted by the light source 22 is coupled into an optical interference network 24 having optical channels 24a, 24b, 24c, and 24d. In the use of the optical shape sensing system 10, each of the individual fiber cores 14, 16, 18, and 20 is connected to one of the optical channels 24a, 24b, 24c, and 24d.

[0077] As the tunable light source 22 sweeps across a series of optical frequencies (or wavelengths), each channel 24a, 24b, 24c, 24d of the fiber 12, and therefore each fiber core 14, 16, 18, 20, is simultaneously but independently optically interrogated, and the resulting interference pattern and reference light from the reflected light from each of the fiber cores 14, 16, 18, 20 are routed to the processing unit 26 via the corresponding photodetector 25. Each channel 24a, 24b, 24c, 24d can be processed independently of the other channels. The distributed strain measurements recorded from the fiber cores 14, 16, 18, 20 using a multi-channel OFDR system can then be derived for further processing, particularly for the three-dimensional shape reconstruction of the fiber optic sensor 12 and for visual display of the reconstructed three-dimensional sensor fiber shape, wherein these processes can be performed by a processor or circuit 27.

[0078] The optical fiber 12 can be integrated into a device (not shown). Such a device can be, for example, a guidewire, catheter, endoscope, etc.

[0079] In OSS, the geometric changes of fiber 12 are encoded into the optical field propagating through fiber 12. Optical interrogation of fiber 12 provides the required information: in principle, to reconstruct the three-dimensional shape of the entire fiber 12 in real time, and thus the three-dimensional shape of the device including fiber 12. Given a suitable coordinate system or reference frame, it is possible to know the exact orientation and position of the complete fiber 12 in real time.

[0080] A more detailed overview of the principles of optical shape sensing can be found in US 2012 / 0069347 A1 and US 8,773,650 B2.

[0081] Figure 3 The diagram illustrates the core geometry of a 4-core optical fiber that can be used as or incorporated into a FORS sensor, with its origin positioned at the geometric center of the fiber. Figure 5In this context, the number 0 exemplarily refers to the central core, and the numbers 1, 2, and 3 exemplarily refer to the outer cores. The core's angle φ relative to the origin of the chosen coordinate system... i and distance a i (i = 0, 1, 2, 3) Figure 5 The relative angle c with respect to fiber core 1 is defined in the code. i (concen) and relative distance r i (Radial, not shown). Therefore, more generally, c i =φ i -φ1 and r i =a i / a1, where i = 1, 2, ..., N, and N is the number of outer cores of the optical fiber. In this definition, c i This is a relative angle to the angular position of a reference core, in this case, core 1. Similarly, r i The radial distance from fiber core 1 to the center of the fiber is normalized.

[0082] c for the outer core i The nominal value is c i = (i-1)360 / N, i = 1, 2, ..., N, and if all outer cores have the same radial distance from the fiber center as core 1, then r i =1. In reality, manufacturing tolerances will result in c i and r i These are small changes in the nominal values.

[0083] Figure 4 The standard FORS settings are shown, where, corresponding to Figure 1 The components in the middle utilize those components with Figure 1 The same reference number markers are used. Thus, Figure 4 A simplified representation is shown of a shape-sensing console or interrogator 21 and an optical fiber 12 connected to it. The optical fiber 12 can be connected to the shape-sensing console 21 via a connector, which is also equipped with an optical fiber 34 having the same number of cores as the optical fiber 12. The connector is not necessarily present, but the optical fiber 12 can be directly connected to the shape-sensing console 21. Figure 4 In the diagram, the fiber cores of optical fiber 12 are designated A1, A2, A3, and A4, and the fiber cores of optical fiber 34 connected to the connector are designated B1, B2, B3, and B4. C1, C2, C3, and C4 refer to the fiber cores of the optical fibers exiting from the interrogator (shape sensing control console 21).

[0084] In the use of system 10, the end of the optical fiber 12 equipped with connector 30 is connected to the end of the optical fiber 34 of the connector cable equipped with connector 32. Similarly, the proximal end of the optical fiber 34 of the connector cable equipped with connector 36 can be connected to the end of the optical fiber having integrated optical channels 24a, 24b, 24c, 24d as the core. When the connector cable is not used, the connector 30 with optical fiber 12 is directly connected to the optical fiber of the interrogator or shape sensing console 21.

[0085] For a functional optical connection to be established between fiber 12 and optical interrogator 21 (optionally via optical connector 34), it is important to align the outer and center cores of fiber 12 with the outer or center cores of fiber 34 of connector 34 at the connection point. A common way to achieve this alignment is to assemble the two fibers into kit fiber optic connectors 30, 32 (or 36 and 38), each kit having keys 48, 50 or 44, 46, configured to engage for locking the connection between the fibers in a rotationally fixed standard orientation. Low-tolerance elements (not shown) in connectors 30, 32 (or 36, 38), such as ceramic ferrules, ensure that the two fibers are centered within the mating sleeve. Connector keys 48, 50 (or 44, 46) define the angular alignment.

[0086] For certain guidewire designs, such as back-mounted guidewires, where the outer diameter typically cannot exceed a fraction of 1 mm, robust connectors like the Key 50 are difficult to manufacture. In such cases, an active alignment method may be necessary to ensure proper optical connection between the outer cores of the two connected optical fibers. This article will describe embodiments of such alignment methods.

[0087] In FORS, the reconstruction algorithm creates a shape starting from a certain location on the FORS sensor fiber; this location (starting position) is called the initiation (or initiation only) of the reconstructed shape. The sensor's starting position is either in position (x, y, and z) or in direction (R). x R y and R z When the sensor moves, the entire reconstructed shape translates or rotates along with it. To ensure that the reconstructed shape is displayed stably, it is important to always know the position and orientation of the starting point relative to the relevant coordinate system. This can be achieved by ensuring that this part of the sensor cannot be moved relative to the coordinate system using a mechanically actuated fixing device (no rotation and no translation), or by continuously measuring the rotation and translation of the starting point and correcting the shape for any movement.

[0088] The reconstructed shape can then be displayed in a relevant coordinate system, such as one that matches the operating room using FORS, for example, linked to the operating table. It is possible that additional registration steps are required to correctly translate and rotate the shape to the desired position and orientation. Such registration can be accomplished by comparing the shape with standard data, such as X-ray images. Once this registration is complete, and provided the starting position and orientation are stable (or continuously known so that any movement can be corrected), the reconstructed shape of the fiber will be correctly represented in its matched desired coordinate system.

[0089] During medical procedures, FORS guidewires may need to be connected, disconnected, and reconnected several times. This is especially true for reversibly loadable FORS guidewires, for which the conventional method of using a fixed start-up area cannot be used due to strict limitations on the outer diameter of the device. When disconnecting such a guidewire to slide the treatment device onto the proximal end of the guidewire, it is undesirable to require re-registration during the reconnection of the FORS guidewire's fiber to the connector (or directly to the interrogator), as this would cause delays in the procedure.

[0090] To avoid the need for re-registration, after each reconnection, it is necessary to know with high accuracy the orientation and position of the FORS sensor's fiber optic cable at the connection point between the fiber optic cable and the interrogator's fiber optic cable. Although for most degrees of freedom (x, y, z, R...) x R y Mechanical solutions can ensure that the guidewire can be reconnected in a repeatable manner, but the relative rotation angle (i.e., R) between the two fiber ends connected at the connection point about the longitudinal axis is limited. z (Also known as relative roll) is a difficult problem where mechanical solutions cannot provide the required accuracy. For example, for a good optical connection between two multi-core FORS fibers with 35-micron outer cores, aligning the relative roll between the two fibers within one degree (17.5 mrad) is sufficient, such that the corresponding outer cores of the two fibers overlap within a fraction of a micrometer. This measure of accuracy is also provided by conventional fitting methods such as fitting sleeves. However, in order to correctly map the shape of a device with integrated fibers to the relevant coordinate system, the relative roll must be known with at least an order of magnitude higher accuracy. An error of 1 mrad can already give a 1 mm error on a 1 m reconstructed shape of the device. Therefore, it is impossible to rely on the fact that once a good optical connection is achieved when reconnecting the two fibers, the relative roll is also fully equivalent to its value during the previous connection, and the registration is based on that connection.

[0091] Based on the principles of this disclosure, the first optical fiber (such as...) Figure 4 Fiber 12 in the middle and the second fiber (such as Figure 4The method of reconnecting the fiber optic cable (34) avoids re-registration of the current connection position of the two fibers, wherein the registered connection position, which was determined relative to the relevant coordinate system during the previous connection of the two fibers, can be modified using the current relative rolling relative to the previous or initial connection between the two fibers. This method can utilize optical measurements of the amount of light at the current connection position of the reconnected fibers.

[0092] Coupled light from one optical fiber to another, it typically results in some loss, depending on the degree of mode overlap between the fiber cores in both fibers. This loss, known as insertion loss, can be expressed in terms of the transmitted power T. The spatial mode overlap between two nominally equivalent fiber cores is determined by their relative alignment. This assumes direct fiber coupling such that there is no gap between them, the angular mismatch is small, and both fibers have the same mode field radius ω0 at the free-space wavelength (intensity drops to 1 / e). 2 The radius of the first optical fiber, the power transmission T between the core i in the first optical fiber and the core j in the second optical fiber. ij The insertion loss, measured in decibels (dB), can be expressed as follows:

[0093]

[0094] In equation (1), ω0 is the mode field radius, a is the core distance from the core center, which is considered the same for all outer cores for simplicity of calculation, and δ ij =c i 1 -c j 2 θ is the difference between the Concen of core i in the first optical fiber and the Concen of core j in the second optical fiber, and θ is the (unknown) relative rotation angle (roll) between the first and second optical fibers about the longitudinal axis when the fibers are reconnected.

[0095] Difference δ ij δ is a specific characteristic, a measure of the deviation of the angular position of the outer core of the first optical fiber relative to the angular position of the outer core of the second optical fiber. This deviation may be caused by tolerances in the manufacturing processes of the two optical fibers. ij It can be determined by measurements, for example, as described below.

[0096] Equation (1) can be further simplified by Taylor expansion, and is approximately δ. ij -θ = 0, because this will be the relevant range of the optical signal received from the optical interrogation when reconnecting the two optical fibers:

[0097]

[0098] The insertion loss T between the core i of the first optical fiber and the core j of the second optical fiber at the connection point ij dB Insertion loss can be measured by optically interrogating two optical fibers based on their relative rotation angle θ. Different optical techniques can be used to measure insertion loss, but using techniques like OFDR is likely the easiest. Figure 1 The OFDR system in System 10 allows for the measurement of reflections in optical fibers as a function of position with high spatial resolution. FORS relies on the OFDR to interrogate the reflection pattern in each core of the fiber separately, and thus is also able to measure the insertion loss over the optical connection between two fibers.

[0099] Figure 5 The curve showing the insertion loss between two fibers at the connection point is presented as a function of the relative rotation angle θ of a multi-core fiber with N=3 outer cores. This has been obtained from simulations. Figure 5 The curve in the figure. It should be noted again that the number of outer cores needs to be equal to or greater than two for this invention to be applicable. In this simulation, the radial distance from the fiber core to the fiber center is assumed to be 35 μm, and the outer cores are assumed to be arranged at nominal azimuth angles relative to -120° and +120° of core 1. Furthermore, the core angle deviation between the cores of the first fiber and the second fiber has been considered to simulate manufacturing tolerances. δ has been assumed. 11 =0, δ 22 =0.014, and δ 33 = 0.016 rad. The field mode radius ω0 is set to 2.8 μm.

[0100] The insertion losses of all outer cores can be combined into a vector, such as... Figure 6 As shown. This vector traces the curve in three-dimensional space as a function of the relative rotation angle θ. The difference in geometry between the first and second fibers will give different relationships between the insertion losses of the outer cores. In the example of three outer cores, the vector is three-dimensional. Analytically, the vector can be described by the following:

[0101]

[0102] For a given fiber design, it is assumed that ω0 and a are known and possible. The only unknown parameter is δ. 11 δ 22 and δ 33 This depends on the exact geometry of the first fiber compared to the second fiber. These values ​​can be found from measurements, for example, by fitting a plane to a point, since the normal vector of the plane is proportional to the following:

[0103]

[0104] In this embodiment, it is assumed that the angular rotation angle θ between the two optical fibers is unknown in the current connection position when the two optical fibers are reconnected. This embodiment also assumes that after the reconnection of the two optical fibers, the same fiber cores as in the previous connection are connected to each other, i.e., fiber core 1 of the first fiber is connected to fiber core 1 of the second fiber, fiber core 2 of the first fiber is connected to fiber core 2 of the second fiber, and fiber core 3 of the first fiber is connected to fiber core 3 of the second fiber. This particular fiber core-to-fiber configuration can be implemented in several ways, wherein the same fiber cores are connected to each other after reconnection as before reconnection. For example, this alignment can be achieved by a coarse keying mechanism that is good enough to ensure alignment within 360 / N degrees, where N is the number of outer cores. Another way to achieve this alignment is to use optical fingerprinting during alignment to identify which fiber cores of the first fiber are connected to which fiber cores of the second fiber, for example as described in WO 2017 / 182535 A1, and to provide a feedback signal to maintain rotation when an incorrect fiber core is connected. This would require the two optical fibers to be able to rotate relative to each other over a full 360°.

[0105] Although it is expected that the optical signal will always be measured against the center core when the two fiber end faces are close to each other, since it does not depend in principle on the relative angular orientation between the two fibers, there is a high chance that the optical signal at the first contact point between the two fibers cannot be obtained on the outer core without any additional active rotational alignment.

[0106] After positioning the ends of the two optical fibers close to each other to align them along the longitudinal axis of the ends in the current connection position, including the current connection orientation (where the current relative rotation angle is unknown), the two optical fibers (i.e., one or both fibers) are rotated relative to each other. During the rotation, the insertion loss of the outer core changes. As can be seen from equation (2), the insertion loss in decibels is approximately quadratic and depends on the angular mismatch δ between the mating core pairs. ij -θ. Figure 5 The width of the curve in the equation, i.e. how rapidly the transmission decreases with a particular rotation, is given only by the nominal core distance a from the center and the mode field radius ω0. Figure 6 The relative positions of the curves in the curves with respect to each other depend on δ. ij .

[0107] Figure 7 A flowchart illustrating possible implementations of the method according to this embodiment is shown. Figure 8 On the left, the flowchart describes the steps at the initial or previous connection of the two optical fibers, and on the right, it describes the steps for reconnecting the two optical fibers after a disconnection.

[0108] In step 60, the ends of the two optical fibers are initially positioned close to each other at the connection point (e.g., via...). Figure 4 Connectors 30 and 32 (but at least connector 30 has no connector key) are used to align the fibers in the longitudinal direction. In step 62, the ends are rotated relative to each other. For example, only the end of the fiber included by the FORS sensor is rotated relative to the fixed end of another fiber, such as a splice. During rotation, insertion loss is continuously measured on all outer cores. If it is determined in step 64 that the insertion loss of the outer core is not at its minimum, rotation continues. If the insertion loss reaches its minimum in step 64, the method proceeds to step 66, where it is detected which core of the first fiber is connected to which core of the second fiber. During the insertion loss measurement in step 64, enough measurement points are obtained to derive δ from the data for a specific core-to-core configuration. 11 δ 22 and δ 33 δ 11 δ 22 and δ 33 It is stored in the memory of a system such as system 10. The memory may be included by circuit 27 of system 10. Points on the curve ( Figure 6 It is also stored at the position where the alignment stops.

[0109] Figure 6 Exemplary points are shown on the curves corresponding to θ = -2, 0, and 2°.

[0110] The method now proceeds to step 68, a registration step, to align the first and second optical fibers in a relevant coordinate system, including the connection location, such as an operating table in a medical application. Such a registration step can be accomplished using X-ray imaging, but can also be accomplished using other imaging modalities. Following the registration step, a rotation matrix, as known in the art, is obtained and then stored in memory. Therefore, the registered connection location, including the connection orientation, is the connection location registered relative to the relevant coordinate system during the initial or previous connection.

[0111] In step 70, the shape sensing can now be mapped to the relevant coordinate system to which the fiber is registered.

[0112] At some point in the process, the FORS sensor, such as the guide wire, will have to be disconnected from the connector or interrogator and reconnected, for example, when equipment exchange is required, as indicated in step 72.

[0113] After the equipment is swapped, the two optical fibers must be reconnected. The ends of the two optical fibers are repositioned close to each other so that they are aligned relative to each other in the longitudinal direction in the current connection position, including the current connection orientation. In the current connection orientation, the relative rotation angle between the first and second ends of the optical fibers is unknown, or at most known with insufficient accuracy. In step 82, the ends of the optical fibers are rotated relative to each other about the longitudinal axis to optimize the optical signal received from the outer core during optical interrogation of the outer core until the insertion loss of the outer core is sufficiently low, as indicated in step 84. In step 86, it is detected whether the same core of the first and second optical fibers is connected as in the previous connection position. If not, the system 10 may instruct the user to further rotate the end of the first optical fiber relative to the end of the second optical fiber until the same core of the first optical fiber is connected to the same core of the second optical fiber as detected in step 66. Then, the insertion loss on the outer core is determined again. If enough points are collected in step 88 to create a... Figure 6 The curve in the figure can be created in step 90 based on the data, such as... Figure 6 The multidimensional transmission curve in the figure. Using parameter δ 11 δ 22 and δ 33 Using the stored properties, and the known values ​​of the core distance a and mode field radius ω0, one can now use equation (2) (either by fitting or by reversing the function) to determine the relative rotation angle between the first and second fibers about the longitudinal axis in the current alignment, which is relative to the registration alignment obtained through the first or previous connection of the two fibers. Therefore, the difference in relative roll can be calculated in step 92. Finding the roll difference with an accuracy of 1 mrad is possible when the insertion loss on each of the outer cores can be measured with sufficient precision. The reconstructed shape of the sensor's fibers is rotated again using the previously determined rotation matrix (step 68), but in addition, an angular correction based on the calculated relative rotation angle between the two fibers is included in the rotation matrix to correct for the roll difference between the first connection and the reconnection.

[0114] In the previous embodiment, reconnecting the two optical fibers included a fiber-to-fiber configuration after reconnection that was identical to the fiber-to-fiber configuration in the previous or first connection. In this case, the parameter δ was stored only for a single fiber-to-fiber configuration (e.g., 1-1, 2-2, 3-3). ijThis is sufficient. However, limiting the rotation of the two fibers relative to each other may be desirable, for example, to minimize the time required for alignment or to reduce the risk of damaging the fiber optic connectors located at the ends of the first or second fiber. Therefore, it is possible that when the ends are positioned close together in the current connection position, the other cores of the two fibers may not mate as well as in the previous connection. For example, during reconnection, core 1 of the first fiber may be connected to core 2 of the second fiber. Compared to the situation before disconnection, the data points generated by the insertion loss measured on the outer cores will now lie on different curves, making direct comparison to find the relative rotation angle impossible or at least difficult. To link the different transmission curves belonging to different core-to-core configurations, a larger number of insertion loss curves must be considered. For two fibers, each with N=3 outer cores, there are three possible core-to-core configurations. Instead of... Figure 6 There is now three different curves instead of one insertion loss curve.

[0115]

[0116]

[0117]

[0118] It should be noted again that this principle can be generalized to any number of outer cores ≥2.

[0119] The three vectors indicated above all depend on the geometric differences between the two connected fiber optic cables. This means that for any combination of i and j, δ ij It should be known. If for all possible combinations, and given the nominal outer core distance a and the mode field radius ω0, δ ij If it is known, then the curve can be predicted for all possible core-to-core configurations. Figure 8 These curves are shown.

[0120] δ for all core-to-core configurations ij Measurements can be performed in advance as a manufacturing step, for example, each including a connector and sensor with a specific optical fiber.

[0121] Figure 9 This is a flowchart describing possible implementations of this embodiment. Steps 60 and 66 can be... Figure 7 The flowchart is the same. Using the geometric information δ on the two optical fibers at its connector... ij As indicated in step 94, in step 96, transmission profiles can be calculated for all arrangements of core-to-core alignment. The established transmission profiles will be used for the reconnection of the two optical fibers.

[0122] In step 98, the core-to-core configuration of the two optical fibers at the initial or first connection is determined.

[0123] Steps 68 and 72 Figure 7 The same as in the flowchart.

[0124] During reconnection, after steps 80, 82, and 84 have been performed, it is determined which core of the first fiber is connected to which core of the second fiber at the current connection location, as indicated by step 100. Now, using the transmission curves obtained in step 96, and knowing all these curves allows for the determination of positions on these curves before and after reconnection. Using this knowledge, the relative rotation angle θ can be found for each value of θ between 0 and 360°, such as... Figure 8 As shown. The new core-to-core configuration can be determined in step 102.

[0125] Therefore, use similar Figure 8 From the transmission curve of the curve, the value of θ can be found, and this value of θ can then be used in step 104 to correct the rotation matrix obtained in registration step 68.

[0126] As described in the above embodiments, the insertion loss of the outer core in the optical fiber of the FORS sensor can be combined into a vector, for example, as... Figure 6 and 8 As shown, it tracks a curve in N-dimensional space, where N is the number of outer cores. Now, when reconnecting the two fibers, it is possible to use the actual or current position on the curve as a feedback signal, because this signal contains information about which side the current alignment is on for optimal (e.g., maximum transmission). Therefore, it is now possible to provide directional information to the user during alignment.

[0127] This is Figure 10 The diagram is shown in the image. Figure 10 Several steps (a) to (e) during the alignment of the optical fiber of the FORS sensor are shown. For each step (a) to (e), it is described in... Figure 11 The present invention indicates what a conventional feedback signal can look like and what it can look like using the principles of this disclosure. By examining the center core of the sensor's optical fiber, the system can (only) determine whether the sensor is connected (steps (a) and (b)). Then, a rotational alignment is performed to align the outer core (steps (c), (d), and (e)). Without the principles of this disclosure, it would be impossible to see whether the rotational alignment about the longitudinal axis is before or after optimal alignment, but with the present invention, it is possible to distinguish between these alignments, as shown by indicator 108. Indicator 108 can be visually displayed by the system, for example, on a graphical user interface. Instead of a visual indicator, it is also feasible to output an audio signal as an indicator, wherein direction can be indicated by a specific frequency and / or loudness.

[0128] refer to Figure 11 The principles of this disclosure will also be described in their implementation in a FORS system (such as system 10).

[0129] Figure 11 a) illustrates the standard setup. In the standard setup, the shape reconstruction of the optical connection 122 between the mechanically activated fixing device 120 and the optical fiber to the connector 126 (or directly to the interrogator 21) remote from the sensor 124 begins, as defined by the optical connection 122. Figure 11 As shown in a). Therefore, the twist is continuous throughout the reconstructed shape of sensor 124. In such a configuration, it is possible to connect and disconnect sensor 124, while actuation 120 can be held in a mechanically stable actuation fixture.

[0130] When using a reversibly loadable guidewire as sensor 124, Figure 11 The setup in a) will not be feasible. This is because the stringent dimensional requirements for the guidewire outer diameter prevent a robust mechanical actuation device that can accurately reproduce the relative rotation angle between the end of the fiber of sensor 124 and the end of the fiber of connector 126. The x, y, and z positions, as well as the connector orientation with respect to the x and y axes, can still be mechanically defined.

[0131] exist Figure 11 In b) and c), two possible embodiments are depicted for use as sensor 124 in conjunction with a reversibly loadable FORS guidewire when implementing the principles of this disclosure. Figure 11 In b) and c), the roll (rotation angle about the longitudinal axis) relative to the registration is fixed proximally to the optical connection 122, which allows the reversibly loaded FORS guidewire with integrated fiber to be freely disconnected from the rest of the system. Since the activation fixation device 120 is now positioned proximally to the optical connection 122 between sensor 124 and connector 126, the rotational orientation (roll) of sensor 124 relative to the initial registration (via activation 120) is a priori unknown after reconnection of sensor 124. At this point, the principles of this disclosure, as described herein, allow the relative rotation angle (R) between sensor 124 and connector 126 about the longitudinal axis to be found. z When the relative rotation angle is known, the shape can be reconstructed relative to the original registration performed before the reconnection of the two optical fibers of the sensor and connector.

[0132] Figure 11 The difference between the settings in b) and c) is that, Figure 11 In b), the optical connection 122 is directly at the rolling fixed point (mechanical actuation). Figure 11In c), the optical connection 122 is positioned at a distance from the fixture 120. The latter setting also requires reconstructing the shape of the portion of the connector 126 leading from the starter 120 to the optical connection 122 in order to know the orientation of the connector 126 at the connection point 122.

[0133] While the invention has been illustrated and described in detail in the accompanying drawings and foregoing description, such illustrations and descriptions should be considered illustrative or exemplary rather than restrictive; the invention is not limited to the disclosed embodiments. Other variations of the disclosed embodiments can be understood and implemented by those skilled in the art in practicing the claimed invention by studying the drawings, specification, and appended claims.

[0134] In the claims, the word "comprising" does not exclude other elements or steps, and the words "a" or "an" do not exclude a plurality. A single element or other unit can perform the functions of several items recited in the claims. Although specific measures are recited in different dependent claims, this does not indicate that combinations of these measures cannot be advantageously used.

[0135] Computer programs can be stored / distributed on suitable non-transient media, such as optical storage media or solid-state media supplied together with or as part of other hardware, but computer programs can also be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0136] All registration data, initial or modified registration data, or any other optical, geometric or positioning-based data, may be stored, for example, in memory or another storage medium.

[0137] Any reference numerals in the claims should not be construed as limiting the scope.

Claims

1. A method for reconnecting a first optical fiber (12) to a second optical fiber (34), the first optical fiber (12) and the second optical fiber (34) being used to determine the shape of a device in a coordinate system by optical shape sensing, the first optical fiber (12) and the second optical fiber (34) each having a plurality of outer cores, the method comprising: (a) Positioning the first end of the first optical fiber (12) and the second end of the second optical fiber (34) close to each other so that they are aligned with each other at a current connection position along the longitudinal axis of the first and second ends, the current connection position including a current connection orientation in which the current relative rotation angle between the first and second ends about the longitudinal axis is ( θ The relative rotation angle between the first and second ends in the registration connection orientation is unknown. The first and second optical fibers have been registered relative to the coordinate system during the previous connection of the first optical fiber (12) and the second optical fiber (34). (b) Optically interrogating the outer cores of the first optical fiber (12) and the second optical fiber (34) through the current connection position to receive optical signals from the outer cores. (c) Modify the previous registration by means of the current relative rotation angle based on the optical interrogation of the outer core, such that the first and second optical fibers in the current connection orientation are correctly registered relative to the coordinate system, the current connection orientation including the current relative rotation angle between the first end and the second end about the longitudinal axis. θ ).

2. The method of claim 1, further comprising instructing the user that the first end and the second end be rotated relative to each other about the longitudinal axis in order to optimize the strength of the received signal.

3. The method according to claim 1, wherein, Step (c) includes determining the current relative rotation angle between the first end and the second end based on the optical interrogation of the outer core. θ ), and using the determined current relative rotation angle ( θ This is used to correct the registration connection orientation.

4. The method according to claim 1, wherein, Step (b) includes deriving the amount of light selected from the group consisting of: insertion loss, transmission, and reflection at the current connection location for each of the outer cores, based on the optical signal.

5. The method according to claim 4, further comprising: Based on the light quantity for each fiber core, the current relative rotation angle between the first and second ends is determined based on the storage characteristics specific to the two fibers (12, 34) to be reconnected. θ ).

6. The method according to claim 5, wherein, The stored characteristics include the deviation of the angular position of the outer core of the first optical fiber (12) relative to the angular position of the outer core of the second optical fiber (34).

7. The method according to claim 6, wherein, The stored characteristics include the deviation between the angular position of the outer core of the first optical fiber (12) and the angular position of the outer core of the second optical fiber, which are already in optical communication during the previous connection.

8. The method according to claim 6, wherein, The stored characteristics include all possible combinations of the outer core of the first optical fiber (12) and the outer core of the second optical fiber (34), and the deviation between the angular position of the outer core of the first optical fiber (12) and the angular position of the outer core of the second optical fiber (34).

9. The method according to claim 5, wherein, During the initial or previous connection of the first optical fiber (12) and the second optical fiber (34), the stored characteristics are determined based on optical measurements of the amount of light relative to a plurality of relative rotation angles between the first end and the second end.

10. The method of claim 1, further comprising identifying a current combination of the outer core of the first optical fiber (12) and the outer core of the second optical fiber (34).

11. The method of claim 10, further comprising instructing a user to rotate the ends of the first optical fiber (12) and the second optical fiber (34) relative to each other about the longitudinal axis until the cores of the first optical fiber (12) and the second optical fiber (34) that are optically connected to each other in the previous connection between the first optical fiber and the second optical fiber are optically connected to each other.

12. The method according to claim 1, wherein, The registration position, including the registration orientation, is registered relative to the start position (120), and the second optical fiber (34) is directly connected to the first optical fiber (12) at the start position (120) or at a distance away from the start position (120).

13. The method according to claim 1, wherein, One of the first optical fiber (12) and the second optical fiber (34) is integrated in the device (124), and the method further includes reconstructing the shape of the device (124) using the registration position modified in the case of reconnection of the first optical fiber and the second optical fiber.

14. A system comprising: A first optical fiber (12) and a second optical fiber (34), the first optical fiber (12) and the second optical fiber (34) being used to determine the shape of the device in a coordinate system by optical shape sensing, the first optical fiber (12) and the second optical fiber (34) each having a plurality of outer cores, a first end of the first optical fiber (12) and a second end of the second optical fiber (34) being positioned, wherein the first end of the first optical fiber and the second end of the second optical fiber are aligned with each other along the longitudinal axis of the first end and the second end at a current connection position including the current connection orientation, wherein the current relative rotation angle between the first end and the second end about the longitudinal axis in the current connection orientation is ( θ The relative rotation angle between the first and second ends in the registration connection orientation is unknown. The first and second optical fibers have been registered relative to the coordinate system during the previous connection of the first optical fiber (12) and the second optical fiber (34). An optical interrogator (21) is configured to interrogate the outer cores of the first optical fiber (12) and the second optical fiber (34) at the current connection position to receive optical signals from the outer cores. A circuit configured to modify a previous registration by means of the current relative rotation angle based on the optical interrogation of the outer core, such that the first fiber (12) and the second fiber (34) are correctly registered relative to the coordinate system in the current connection orientation, which includes the current relative rotation angle between the first end and the second end about the longitudinal axis.

15. A computer program product including a program code module, the program code module being configured to cause the system of claim 14 to perform the steps of the method of claim 1.

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