Optical fiber device calibration

Abstract

A method and device for generating calibration data for an optical heating fiber device. The method comprising placing a hollow core optical fiber (HCF) in a calibration device, the HCF having an outer structure and an internal structure; subjecting the HCF to an amount of heat energy; monitoring the internal structure of the HCF; determining, using data from monitoring, when the internal structure of the HCF changes; and recording the change of the internal structure of the HCF and an associated amount of energy provided to the heating device for creating the heat energy.

Description

OPTICAL FIBER DEVICE CALIBRATIONBACKGROUND

[0001] Aii optical fiber, also known as an optical fibre, is a glass or plastic fiber that can transmit light along a length of the optical fiber. An optical fiber may be used in a fiberoptic communication system where data is transmitted over long distances and at a high bandwidth. An optical fiber may take a large number of different forms and may have cladding applied around an outer surface to mechanically protect the optical fiber and / or aid in light transmission along the optical fiber. An optical fiber may comprise a solid core such as a solid core optical fiber (SCF) illustrated in FIGs. 1A and IB or a hollow core making it a hollow core optical fiber (HCF). An HCF guides light within a hollow region of the fiber. In HCF, a minor portion of the optical power may still propagate through solid fiber material.

[0002] FIG. 1A illustrates a cross section of a SCF orthogonal to a longitudinal axis. The SCF has an outer surface 11, a solid core 110 and cladding 111 surrounding the solid core 110. Light travels axially through the solid core 1 10 along the SCF. The cladding 111 is to reduce light escaping the solid core 110. FIG. IB illustrates a cross section the SCF of FIG. 1A parallel to a longitudinal axis. The solid core is not visible in FIG. IB but its path is indicated using dashed lines.

[0003] An optical fiber may become damaged or broken either intentionally or accidentally and ends of respective fibers need to be joined, also known as spliced, fused or welded, back together to allow the transmission of light along the entire length of a fiber across both parts that were previously two or more parts. The fusing may be performed with a device known as a fusion splicer. The fusion splicer may align optical fiber ends using an optical aid, such as a camera, and then emit heat energy to the aligned ends of the optical fiber lengths. The emitted heat energy is sufficiently hot to soften or melt the fiber material, usually glass, and the fusion splicer will then force the ends of the fibers together to repair the break. The join is known as a splice. The process is performed to repair breaks and also performed during fiber installation. Fusion splicers may use a variety of devices and methods to generate the heat energy. In one example, a fusion splicer may generate heat energy from an electric arc between two electrodes across an air-gap proximal to aligned ends of optical fiber lengths. In another example, a fusion splicer may generate heat energy using a filament. In yet another example, a fusion splicer may generate heat energy using a flame. In a further example, a fusion splicer may generate heat energy using a laser. Alternative ways to generate heat energy within fusion splicers are known and the belowdisclosures are widely applicable to different types of fusion splicers and similar devices required to heat optical fibers.

[0004] In an arc heating device, the temperature of the arc created between the electrodes can be regulated based on the current and / or voltage provided at the electrodes. Each time a splice or optical fiber heating is performed, it is important that the temperature generated by the arc is controlled and consistent. Further, a fixed current / voltage does not necessarily generate a consistent heat generated by the electrodes because air pressure, air humidity, air temperature, and electrode shape or electrode coating (caused by wear etc.) can lead to different arc temperatures. For an optimum fusion process, calibration is required. Corresponding issues are present for other devices that use heating methods other than arcing. For example, resistive heating element performance may change over time leading to a change in resistance characteristics of the heater meaning that calibration is required in order to avoid over heating or underheating an optical fiber. For example, a laser optic may become coated in deposits that are created during heating from oxidation of materials being heated - the deposits may degrade heating efficiency meaning calibration is required. In the below disclosure, heating using an arc device is described for consistency and readability, however the examples are not limited to only arc devices operable to heat optical fibers.

[0005] Arc calibration is a process that may be performed on a fusion splicer to calibrate a generated arc temperature relative to a current / voltage applied to electrodes of the fusion splicer. Two arc calibration methods are illustrated in FIGs. 3A-3D. Both require two ends of SCFs and changes based on applied heat are measured in order to calculate an amount of generated heat and / applied energy.

[0006] A first method requires two ends of SCFs, illustrated in FIG. 3A. The ends are separated by a distance D 1. A set amount of voltage / current is applied to two electrodes sufficient to cause an electrical arc and generation of heat proximal to the ends. Each fiber has a solid central portion 31 and an outer surface 30. FIG. 3B illustrates the ends of the SCFs after heat has been applied. The applied heat has caused melting of both SCFs and the distance D2 separating the ends of the two SCFs has increased. The melt-back rate of a SCF of known structure is proportional to the applied heat; therefore, the relative distance between the two ends DI, D2 may be used to calibrate a fusion splicer.

[0007] A second method requires two ends of SCFs, illustrated in FIG. 3C. The ends are separated and the angle between the end surface and circumference of each SCF is approximately 90 degrees with a very small radius at the corner. A set amount of voltage / current is applied to two electrodes sufficient to cause an electrical arc andgeneration of heat proximal to the ends. Each fiber has a solid central portion 33 and an outer surface 32. FIG. 3D illustrates the ends of the SCFs after heat has been applied. The applied heat has caused melting of both ends of the SCFs and so the radius at the comers between the end surfaces and the circumferential surfaces has increased. The melting has caused SCF material present prior to heating to move during heating leaving empty space 33, 34 that is visible and is measurable. The increase in radius at ends of a SCF of known structure is proportional to the applied heat therefore a change in radius may be used to calibrate a fusion splicer.

[0008] In non-arc devices, other heating parameters may be changed during calibration to affect heat output.SUMMARYThe following presents a simplified summary of the disclosure in order to provide a basic understanding to the reader. This summary is not intended to identify key features or essential features of the claimed subject matter nor is it intended to be used to limit the scope of the claimed subject matter. Its sole purpose is to present a selection of concepts disclosed herein in a simplified form as a prelude to the more detailed description that is presented later.

[0009] A first aspect is a method for generating calibration data for an optical fiber heating device. The method comprising placing a HCF in a calibration device, the HCF having an outer structure and an internal structure; subjecting the HCF to an amount of heat energy; monitoring the internal structure of the HCF; determining, using data from monitoring, when the internal structure of the HCF changes; and recording the change of the internal structure of the HCF and an associated amount of energy provided to a heating device for creating the heat energy.

[0010] A second aspect is an apparatus comprising a processor; and a memory storing instructions that, when executed by the processor, cause the apparatus to perform operations for generating calibration data for an optical fiber heating device. The operations comprising an amount of heat energy subjected to a HCF; monitoring an internal structure of the HCF; determining, using data from monitoring, when the internal structure of the HCF changes; and recording the change of the internal structure of the HCF and an associated amount of energy provided to a heating device for created the heat energy.

[0011] A third aspect is a device arranged to generate calibration data for an optical fiber heating device. The device comprising a processor; and a memory storing instructions that, when executed by the processor, cause the device to perform operations, comprising: subjecting a HCF in the device to heat energy; monitoring an internal structure of the HCF;subjecting, after the monitoring, the HCF in the device to further heat energy; monitoring, after subjecting to further heat energy, the internal structure of the HCF; determining, using data from the monitoring, when the internal structure of the HCF changes; and recording the change of the internal structure of the HCF and an associated amount of energy provided to the heating device.[ 00121 Calibrating an optical fiber heating device using an HCF means that the calibrated device will operate better with HCFs as the calibration power range is aligned with the operation power range. Calibrating an optical fiber heating device using a SCF means that the calibration power range is much greater than an HCF operation power range so there is a greater chance that an extrapolation of the calibration data will provide non- optimal calibration. Further, calibration taking into account an HCF structure will provide calibration data relevant to the same or similar HCF structure, which structures vary greatly. This means that a first HCF with microstructures close to a longitudinal axis may have a different calibration range to an HCF with microstructures further from a longitudinal axis. In addition, HCF with different cladding thickness will have a different calibration range. A further use of the methods disclosed herein is to identify a maximum optical fiber heating power corresponding to when a HCF microstructure begins to miss-shapen due to heat as this information may be used to minimize an amount of miss-shapen microstructures when splicing together two ends of HCF.

[0013] Many of the attendant features will be more readily appreciated as the same becomes better understood by reference to the following detailed description considered in connection with the accompanying drawings.DESCRIPTION OF THE DRAWINGS

[0014] The present description will be better understood from the following detailed description read in light of the accompanying drawings, wherein:FIG. 1A illustrates a cross section of a SCF orthogonal to a longitudinal axis; FIG. IB illustrates a cross section the SCF parallel to the longitudinal axis;FIG. 2 illustrates a schematic view of a device for calibrating heating of an optical fiber;FIG. 3A illustrates two ends of a first two SCFs prior to heating; FIG. 3B illustrates the ends of the first two SCFs after heating; FIG. 3C illustrates two ends of a second two SCFs prior to heating; FIG. 3D illustrates the ends of the second two SCFs after heating; FIG. 4A illustrates a cross section of an HCF;FIG. 4B illustrates a length of the HCF;FIG. 4C illustrates a side-view image of an HCF;FIGs. 5A-5C illustrates images of an HCF undergoing heating;FIG. 6 illustrates a method for generating calibration data for an optical fiber heating device; andFIG. 7 illustrates a schematic diagram of an exemplary computing-based system for use with example devices and methods.

[0015] Like reference numerals are used to designate like parts in the accompanying drawings.DETAILED DESCRIPTION

[0016] The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present examples are constructed or utilized. The description sets forth the functions of the examples and the sequence of operations for constructing and operating the examples. However, the same or equivalent functions and sequences may be accomplished by different examples.

[0017] FIG. 2 illustrates a schematic view of a device suitable for calibrating the heating of an optical fiber. The device may be part of a fusion splicer, be part of a different device or be a separate device. The illustrated device is an arc device and comprises a first and second electrode 251, 252 and an electrode controller 26 arranged to control current and / or voltage provided to the electrodes. Applied electrical power creates an arc between the electrodes 251, 252 at a heating zone 24. An optical fiber can be placed between the electrodes and pass through the heating zone 24. One or more cameras 28, 29 may be arranged to view the optical fiber 21 in the heating zone 24. A camera system 27 coupled to the camera(s) may view the optical fiber 21 at specified times and collect image data of the optical fiber 21 . The fiber may run along a Z-axis and cameras may be placed on an X-axis and / or a Y-axis with a camera field of view including the heating zone 24 and a point intersecting the X, Y and Z-axes. A controller may be included and arranged to control the electrode controller and the camera system 27 for automated functionality of the device. In FIG. 2, the is an arc device and two electrodes are illustrated, however in other examples more than two electrodes may be present.

[0018] FIG. 4A illustrates a cross section of an HCF. The HCF has an outer surface 42 that is an outer surface of a solid outer wall or cladding 420. Within the solid outer wall or cladding 420 is a hollow core 400. Additional structures within the HCF extend along the length of the HCF. In FIG. 4AB, there are six inner tubular structures 421 and six intermediate tubular structures 422 extending along the length of the fiber. The inner andintermediate tubular structures 421, 422 are substantially equally placed around the hollow core 400. Within each respective intermediate tubular structure 422 is an inner tubular structure 421 extending along the length of the HCF. The outer wall 42, inner tubular structure 421, and intermediate structure 422 ran substantially parallel to each other along the length of the HCF. The space within the HCF illustrated as a void in the figure is filled with a fluid. For example, the fluid may be an inert gas such as argon, nitrogen, or atmospheric air. Advantages of HCF over SCF are that transmitted light travels faster along HCF (lower latency), higher powers can be transmitted over HCF and that light scatter is reduced in HCF therefore attenuation of light travelling along a fiber length is reduced. The HCF of FIG. 4A is merely an example fiber and there are many other HCF structures possible with different numbers, shapes and positions of internal structures.

[0019] FIG. 4B illustrates a length of the HCF 41 with an open end (at the right side of the figure). There are many configurations of HCF not limited to those in FIGs. 4A and 4B. In FIG. 4B, the type of HCF illustrated in FIG. 4A is used. The figure illustrates a small section of a long length of HCF. The length of HCF may be placed in a calibration device such as that illustrated in FIG. 2.

[0020] FIG. 4C illustrates an image of an HCF. In FIG. 4C, the HCF runs horizontally with a central axis running across the page. The image is backlit, the top and bottom bands 431, 438 are a background, and the darker horizontal object is the HCF. The HCF has top 432 and bottom 437 surfaces corresponding to the fiber’s edge. The lines 433, 434, 435, 436 within the fiber correspond to structures within the HCF. In the figure the structures are microstructure tubes within the HCF and the structures ran parallel to a central axis of the fiber.

[0021] FIGs. 5A-5C illustrates images 501-515 of an HCF undergoing heating as part of a calibration process. A hollow region, structures or microstructures within an HCF may collapse due to surface tension when heat is applied to the HCF and part of the fiber material is in a molten state. For this reason, calibration techniques which rely on measuring the melting of SCF ends, edges or corners can be inconsistent for HCFs due to the collapsing of internal structures of the HCF prior to a change to an external structure of the HCF. Further, the energy required to melt external or internal parts of a SCF may be far greater than the energy required to collapse an internal structure of an HCF. This means that the calibration energy levels relevant to an HCF are different to those of an SCF and therefore a device calibrated using a SCF may require extrapolation of a calibration range down to reach energy levels relevant for an HCF.

[0022] Images 501-515 show a close-up of an HCF being subject to heating inside a calibration device. In each image, the top and bottom bands relate to a background and the darker central band is the HCF with the exterior cylindrical surface of the HCF being at the top and bottom of the darker central band. The light substantially horizontal bands within the darker central band correspond to microstructures within the HCF.[0023| Different heating protocols are used in respect of the calibration method and device disclosed herein. In the example of FIGs. 5A-5C, the HCF was heated for 1000 ms and an image was taken - this was repeated with the current between the electrodes increased by approximately 0.5 mA between each image. Only one camera was used. FIG. 4C illustrates an initial image prior to heating and FIG. 5A, image 501 was taken after a first heating. For brevity, only alternatively taken images are presented in FIGs. 5A-5C so that two heating session occurred between each image 501-515. In the example of FIGs. 5A-5C, the HCF was heated, allowed to cool, imaged prior to being reheated. In the images 501 - 515, microstructures inside the HCF are observable and it is observable when the internal structures of the HCF soften or melt and deform or collapse. Changes to the HCF microstructure occur prior to changes to the external surface of the fiber.

[0024] Images 501-506 show minimal changes to the HCF microstructure, however images 507-512 show a collapse in a number of microstructures. Image 510 illustrates a collapse in multiple microstructures in a central part of the HCF with the collapse spreading along a central axis in both directions with the application of further heating. Images S ISS IS show changes in the outer circumferential wall of the HCF, which occur after substantial changes in the internal structure of the HCF. In the example of FIGs. 5A-5C, some or all external fiber coating, if present, must be removed prior to heating as the coating would carbonize and so obscure the HCF image.

[0025] In an alternative example, one heating duration is used and the HCF internal structure is imaged / monitored during or after the heating duration. In a further example, a similar technique may be performed wherein images are taken of a cleaved-open HCF end face and end view of microstructures within the HCF are viewed at various points during a heating protocol. In a yet further example, an HCF is heated using a heating protocol and light is transmitted along the HCF and changes to internal HCF microstructures are detected and monitored by measuring the amount of light reflected / scattered and / or transmitted. While FIGs. 5A-C result from arc heating, other heating methods disclosed herein may be used to generate calibration data.

[0026] FIG. 6 illustrates a method for generating calibration data for an optical fiber heating device.

[0027] Block SI recites placing an HCF having an outer structure and an internal structure in a calibration device. The device may correspond to the device illustrated in FIG. 2 or a non-arc heating optical fiber heating device.

[0028] Block S2 recites subjecting the HCF to an amount of heat energy. The heat energy may be supplied by arcing between electrodes or by resistive heating, etc. In some examples, the heating intensity increases by increasing the duration of each heating pulse but each with a same heating intensity, increasing the duration of each heating pulse with a same intensity, maintaining the duration of each heating pulse and increasing the heating intensity, or increasing both the duration and intensity of the heating pulses.

[0029] Block S3 recites monitoring the internal structure of the HCF. The monitoring may be performed by any of the methods disclosed herein (including viewing the HCF from a side, viewing the HCF from a cleaved end face, and / or monitoring the transmittal of light along the HCF or any other suitable method.

[0030] Block S4 recites determining, using data from monitoring, when the internal structure of the HCF changes. The determination may be performed by a number of methods. In one example, image analysis is used to determine relative changes between images, for example by subtraction of the original image, prior to heating, from the iterative images. Alternatively, measuring pixel changes in the vertical and / or horizontal direction. In further examples, data sets of images are used to train one or more machine learning models to detect changes to the collected image data. A convolutional neural network (CNN) model and a deep learning method recurrent neural network (RNN) both function to classify images and can detect the changes in HCF microstructures. In examples where the transmittal of light along the HCF is monitored, a percentage or absolute change in transmittal is used as a threshold to indicate microstructure changes.

[0031] Block S5 recites recording the change of the internal structure of the HCF and an associated amount of subjected heat energy.

[0032] Block S6 is optional and recites generating a file comprising calibration data for an optical fiber heating device, the file comprising the recorded change and the associated amount of subjected heat energy. The file can then be used for further analysis or for applying a calibration to the device or another optical fiber heating device. A calibration may require a device to increase or decrease a reference point power, which may be either adding or subtracting current supplied to the electrodes, or by varying the heating means of the specific device.

[0033] Alternatively, or in addition, the functionality described herein is performed, at least in part, by one or more hardware logic components. For example, and withoutlimitation, illustrative types of hardware logic components that are optionally used include Field-programmable Gate Arrays (FPGAs), Application-specific Integrated Circuits (ASICs), Application-specific Standard Products (ASSPs), System-on-a-chip systems (SOCs), Complex Programmable Logic Devices (CPLDs), Graphics Processing Units (GPUs).|0034| FIG. 7 illustrates various components of an exemplary computing-based device 1000 which are implemented as any form of a computing and / or electronic device that may be included in the device of FIG. 2.

[0035] Computing -based device 1000 comprises one or more processors 1001 which are microprocessors, controllers or any other suitable type of processors for processing computer executable instructions to control the operation of the device of FIG. 2. Platform software comprising an operating system 1011 or any other suitable platform software is provided at the computing-based device to enable application software 1012 to be executed on the device. The application software 1012 may perform steps of the method illustrated in FIG. 6.

[0036] The computer executable instructions are provided using any computer-readable media that is accessible by computing based device 1000. Computer-readable media includes, for example, computer storage media such as memory 1010 and communications media. Computer storage media, such as memory 1010, includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or the like. Computer storage media includes, but is not limited to, random access memory (RAM), read only memory (ROM), erasable programmable read only memory (EPROM), electronic erasable programmable read only memory (EEPROM), flash memory or other memory technology, or optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that is used to store information for access by a computing device. In contrast, communication media embody computer readable instructions, data structures, program modules, or the like in a modulated data signal, such as a carrier wave, or other transport mechanism. As defined herein, computer storage media do not include communication media. Therefore, a computer storage medium should not be interpreted to be a propagating signal per se.Although the computer storage media (memory 1010) is shown within the computing-based device 1000 it will be appreciated that the storage is, in some examples, distributed or located remotely and accessed via a network or other communication link (e.g. using communication interface 1002, if present).

[0037] The computing-based device 1000 also comprises an input / output controller1003 arranged to output display information to an optional display device 1021 which may be separate from or integral to the computing-based device 1000. The display information may provide a graphical user interface. The input / output controller 1003 is also arranged to receive and process input from one or more devices, such as a user input device 1022 (e.g. a mouse, keyboard, camera, microphone or other sensor). The input / output controller 1003 may communicate with one or more cameras 28, 29, such as those illustrated in FIG. 2 and may also control the electrode controller 26 of FIG. 2. Processor 1001 may be used to automatically control heating and image sampling of an HCF or light transmittal through an HCF during calibration. The results of the calibration may be generated prior to use in the same device as a fusion splicer or in another device.

[0038] Alternatively or in addition to the other examples described herein, examples include any combination of the following:

[0039] Clause A. A method for generating calibration data for an optical fiber heating device, the method comprising: placing an HCF in a calibration device, the HCF having an outer structure and an internal structure; subjecting the HCF to an amount of heat energy; monitoring the internal structure of the HCF ; determining, using data from monitoring, when the internal structure of the HCF changes; and recording the change of the internal structure of the HCF and an associated amount of energy provided to a heating device for creating the heat energy.

[0040] Clause B. The method of clause A further comprising: monitoring an external structure of the HCF; determining, using data from monitoring, when the external structure of the HCF changes; and recording the change of the external structure of the HCF and an associated amount of energy provided to the heating device.

[0041] Clause C. The method of clause B, wherein the external structure is within a cladding on at least part of the HCF.

[0042] Clause D. The method of clause A further comprising generating calibration data for an optical fiber heating device, the calibration data comprising an indication of the recorded change and the associated amount of energy provided to the heating device.

[0043] Clause E. The method of clause A, wherein the HCF comprises a cylindrical surface and the monitoring comprises detecting light passing out of the cylindrical surface of the HCF.

[0044] Clause F. The method of clause E, wherein the monitoring comprises a camera detecting the light.

[0045] Clause G. The method of clause A, wherein the internal structure of the HCF changes comprise a change in a wall of an internal structure adjacent to the hollow core of the HCF.

[0046] Clause H. The method of clause A, wherein the optical fiber heating device is a fusion splicer.[0047| Clause 1. The method of clause A, wherein the monitoring comprises detecting a change in either transmission of light or reflectance of light passing along the HCF.

[0048] Clause J. The method of clause A, wherein the optical fiber heating device is arranged to provide the heat energy.

[0049] Clause K. The method of clause A, wherein the subjecting the HCF to an amount of heat energy comprises subjecting the HCF to multiple durations of heat energy, wherein: each duration of the multiple durations is substantially the same; the durations of the multiple durations increase or decrease; an intensity of a duration increases with respect to a previous duration or each duration of the multiple durations is substantially the same, and an intensity of a duration increases or decreases with respect to a previous duration.

[0050] Clause L. An apparatus comprising: a processor; and a memory storing instructions that, when executed by the processor, cause the apparatus to perform operations for generating calibration data for an optical fiber heating device. The operations comprising: applying an amount of heat energy to an HCF; monitoring an internal structure of the HCF; determining, using data from monitoring, when the internal structure of the HCF changes; and recording the change of the internal structure of the HCF and an associated amount of energy provided to a heating device for created the heat energy.

[0051] Clause M. A device arranged to generate calibration data for an optical fiber heating device, the device comprising: a processor; and a memory storing instructions that, when executed by the processor, cause the device to perform operations, comprising: subjecting an HCF in the device to heat energy; monitoring an internal structure of the HCF; subjecting, after the monitoring, the HCF in the device to further heat energy; monitoring, after subjecting to further heat energy, the internal structure of the HCF; determining, using data from the monitoring, when the internal structure of the HCF changes; and recording the change of the internal structure of the HCF and an associated amount of energy provided to the heating device.

[0052] Clause N. The device of clause M, wherein the operations further comprise: generating a file comprising calibration data for an optical fiber heating device, the file comprising an indication of the recorded change and the associated amount of energy provided to the heating device.

[0053] Clause O. The device of clause M further comprising a camera, wherein the monitoring is performed by the camera.

[0054] Clause P. The device of clause O, wherein the camera is arranged to detect light passing out from a cylindrical surface of the HCF.

[0055] Clause Q. The device of clause M, wherein the monitoring comprises detecting a change in either transmission of light or reflectance of light passing along the HCF.

[0056] Clause R. The device of clause M further comprising an arcing means arranged to provide the heat energy.

[0057] Clause S. The device of clause M, wherein the subjecting the HCF to an amount of heat energy comprises subjecting the HCF to multiple durations of heat energy, wherein: each duration of the multiple durations is substantially the same; the durations of the multiple durations increase or decrease; an intensity of a duration increases with respect to a previous duration; or each duration of the multiple durations is substantially the same, and an intensity of a duration increases or decreases with respect to a previous duration.

[0058] Clause T. The device of clause M, wherein the device is a fusion splicer.

[0059] The methods described herein are performed, in some examples, by software in machine readable form on a tangible storage medium e.g., in the form of a computer program comprising computer program code means adapted to perform all the operations of one or more of the methods described herein when the program is run on a computer and where the computer program may be embodied on a computer readable medium. The software is suitable for execution on a parallel processor or a serial processor such that the method operations may be carried out in any suitable order, or simultaneously.

[0060] Those skilled in the art will realize that storage devices utilized to store program instructions are optionally distributed across a network. For example, a remote computer is able to store an example of the process described as software. A local or terminal computer is able to access the remote computer and download a part or all of the software to run the program. Alternatively, the local computer may download pieces of the software as needed, or execute some software instructions at the local terminal and some at the remote computer (or computer network). Those skilled in the art will also realize that by utilizing conventional techniques known to those skilled in the art that all, or a portion of the software instructions may be carried out by a dedicated circuit, such as a digital signal processor (DSP), programmable logic array, or the like.

[0061] Any range or device value given herein may be extended or altered without losing the effect sought, as will be apparent to the skilled person.

[0062] Although the subject matter has been described in language specific to structural features and / or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.[0063| It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item refers to one or more of those items.

[0064] The operations of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the scope of the subject matter described herein. Aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples without losing the effect sought.

[0065] The term 'comprising' is used herein to mean including the method blocks or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements.

[0066] It will be understood that the above description is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the scope of this specification.

Claims

CLAIMS1. A method for generating calibration data for an optical fiber heating device, the method comprising: placing a hollow core optical fiber, HCF, in a calibration device, the HCF having an outer structure and an internal structure; subjecting the HCF to an amount of heat energy; monitoring the internal structure of the HCF ; determining, using data from monitoring, when the internal structure of the HCF changes; and recording the change of the internal structure of the HCF and an associated amount of energy provided to a heating device for creating the heat energy.

2. The method of claim 1 further comprising: monitoring an external structure of the HCF; determining, using data from monitoring, when the external structure of the HCF changes; and recording the change of the external structure of the HCF and an associated amount of energy7provided to the heating device.

3. The method of claim 2, wherein the external structure is within a cladding on at least part of the HCF.

4. The method of claim 1 further comprising generating calibration data for an optical fiber heating device, the calibration data comprising an indication of the recorded change and the associated amount of energy provided to the heating device.

5. The method of claim 1. wherein the HCF comprises a cylindrical surface and the monitoring comprises detecting light passing out of the cylindrical surface of the HCF.

6. The method of claim 5, wherein the monitoring comprises a camera detecting the light.

7. The method of claim 1, wherein the internal structure of the HCF changes comprise a change in a wall of an internal structure adjacent to the hollow core of the HCF.

8. The method of claim 1, wherein the optical fiber heating device is a fusion splicer.

9. The method of claim 1, wherein the monitoring comprises detecting a change in either transmission of light or reflectance of light passing along the HCF.

10. The method of claim 1. wherein the optical fiber heating device is arranged to provide the heat energy7.

11. The method of claim 1, wherein the subjecting the HCF to an amount of heat energy comprises subjecting the HCF to multiple durations of heat energy, wherein:each duration of the multiple durations is substantially the same; the durations of the multiple durations increase or decrease; an intensity of a duration increases with respect to a previous duration or each duration of the multiple durations is substantially the same, and an intensity of a duration increases or decreases with respect to a previous duration.

12. An apparatus compnsing: a processor; and a memory' storing instructions that, when executed by the processor, cause the apparatus to perform operations for generating calibration data for an optical fiber heating device, the operations comprising: instructing an application of an amount of heat energy subjected to a hollow core optical fiber, HCF; monitoring one or more images of an internal structure of the HCF ; determining, using data from monitoring, when the internal structure of the HCF changes; and recording the change of the internal structure of the HCF and an associated amount of energy' provided to a heating device for created the heat energy'.

13. A device arranged to generate calibration data for an optical fiber heating device, the device comprising: a processor; and a memory' storing instructions that, when executed by the processor, cause the device to perform operations, comprising: subjecting a hollow core optical fiber, HCF, in the device to heat energy; monitoring an internal structure of the HCF; subjecting, after the monitoring, the HCF in the device to further heat energy; monitoring, after subjecting to further heat energy, the internal structure of the HCF; determining, using data from the monitoring, when the internal structure of the HCF changes; and recording the change of the internal structure of the HCF and an associated amount of energy' provided to the heating device.

14. The device of claim 13 further comprising a camera, wherein the monitoring is performed by the camera, and wherein the camera is arranged to detect light passing out from a cylindrical surface of the HCF.

15. The device of claim 13, w herein the monitoring comprises detecting a change in either transmission of light or reflectance of light passing along the HCF.

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