Fiber analysis tool

Abstract

A combined cleaver and fiber analysis tool for use with fibers lacking continuous rotational symmetry is described. The tool comprises: a region for receiving a fiber holder; cleaving apparatus arranged to cleave a fiber held in the fiber holder; a camera arrangement arranged to image a cleaved end face formed by the cleaving apparatus; and an image analysis module configured to analyze an image of the cleaved end face captured by the camera arrangement, determine a rotational offsets and a lateral offset of the fiber in the fiber holder and store the offsets for transmission to a splicer.

Description

FIBER ANALYSIS TOOLBACKGROUND

[0001] Splicing is typically used to join optical fibers and there are various splicing methods that may be used, including fusion splicing and mechanical splicing. Splicing involves aligning the fibers end-to-end and fixing them in the aligned position. Fusion splicing, for example, joins the two fibers by heating the end region in order to soften the glass from which the fibers are made. By pressing the ends together, the softened glass is made to fuse so that the fibers are permanently connected when the glass cools and hardens. Mechanical splicing, in contrast, does not permanently join the fibers together but instead uses a mechanical arrangement to maintain their aligned position and hold the fiber ends together.

[0002] The join formed by splicing two fibers together is referred to as a splice. The quality of the splice is an important factor in enabling low loss optical propagation for light travelling from one fiber to the other. Accurate alignment of structural features within the two fibers so as to reduce structural discontinuities at the splice contributes to low loss.

[0003] Conventional solid core optical fibers, comprising an annular cladding surrounding a single circular core, are relatively simple to align for splicing. The structures have continuous rotational symmetry in transverse cross-section so that transverse alignment of the fiber ends to match the positions of the longitudinal axes of the fibers necessarily aligns the cores and the cladding. However, antiresonant hollow core fibers have a complex internal structure that lacks continuous rotational symmetry and multi-core solid core fibers also lack continuous rotational symmetry. Misalignment of this internal structure and / or of the individual cores increases the optical loss that occurs when light travels from one fiber to the other across the splice.

[0004] The embodiments described below are not limited to implementations which solve any or all of the disadvantages of known fiber cleaving, splicing and analysis apparatus.SUMMARY

[0005] The 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 ofconcepts disclosed herein in a simplified form as a prelude to the more detailed description that is presented later.

[0006] A combined cleaver and fiber analysis tool for use with fibers lacking continuous rotational symmetry' is described. The tool comprises: a region for receiving a fiber holder; cleaving apparatus arranged to cleave a fiber held in the fiber holder; a camera arrangement arranged to image a cleaved end face formed by the cleaving apparatus; and an image analysis module configured to analyze an image of the cleaved end face captured by the camera arrangement, determine a rotational offsets and a lateral offset of the fiber in the fiber holder and store the offsets for transmission to a splicer.

[0007] 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

[0008] The present description will be better understood from the following detailed description read in light of the accompanying drawings, wherein:FIGs. 1-3 show transverse cross-sectional views of three different examples of antiresonant hollow core fibers;FIG. 4 shows an arrangement for end-view observation in a splicer;FIG. 5 is a schematic diagram showing an end view of an antiresonant hollow core fiber;FIG. 6 shows a schematic diagram of an antiresonant hollow core fiber in an example fiber holder;FIG. 7 shows a schematic diagram of a first example fiber analysis tool;FIG. 8 shows a schematic diagram of a first example fiber analysis tool;FIG. 9 is a flow diagram of an example method of operation of a fiber analysis tool as described herein;FIG. 10 is a flow diagram of a method of operation of a splicer that works in conjunction with the fiber analysis tool or combined cleaver and fiber analysis tool described herein;FIG. 11 shows a schematic diagram of a first example combined cleaver and fiber analysis tool;FIG. 12 shows a schematic diagram of the cleaving apparatus that is part of a combined cleaver and fiber analysis tool;FIG. 13 shows a schematic diagram of a second example combined cleaver and fiber analysis tool;FIG. 14 is a flow diagram of an example method of operation of a combined cleaver and fiber analysis tool such as shown in FIGs. 11 and 13;FIG. 15 shows a schematic diagram of a third example combined cleaver and fiber analysis tool;FIG. 16 is a flow diagram of an example method of operation of a combined cleaver and fiber analysis tool such as shown in FIG. 15; andFIG. 17 illustrates an exemplary image analysis module that is part of a fiber analysis tool or a combined cleaver and fiber analysis tool as described herein.Like reference numerals are used to designate like parts in the accompanying drawings.DETAILED DESCRIPTION

[0009] 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.

[0010] FIGs. 1-3 show transverse cross-sectional views of three different examples of antiresonant hollow core fibers (ARFs). Light is guided in these fibers by an antiresonant optical effect. Each of the fibers 100, 200, 300 comprises a tubular outer cladding (or jacket) 102, a structured, inner, cladding comprising a plurality of tubular cladding capillaries 104, 204, 304 and a hollow core 106. The outer cladding 1 2 has a glass thickness that is typically much larger than that of the cladding capillaries 104, 204, 304. In the first example, shown in FIG. 1. the structured, inner, cladding comprises five capillaries 104 of the same cross-sectional size and shape, which are arranged inside the outer cladding 102 in a single ring so that the longitudinal axes of each cladding capillary 104 and of the outer cladding 102 are substantially parallel. Each cladding capillary 104 is in contact with (e.g. bonded to) the inner surface of the outer cladding 102 at an azimuthal location 108, such that the cladding capillaries 104 are evenly spaced around the inner circumference of the outer cladding 102. and are also spaced apart from each other by gaps 110 (i.e. such that there is no contact between neighbouring capillaries). In some designs of ARF, the cladding capillaries 104 may be positioned in contact with each other (in other words, not spacedapart as in FIG. 1). but spacing to eliminate this contact can improve the fiber’s optical performance. The gaps 1 10 remove nodes that arise at the contact points between adjacent tubes and which tend to cause undesirable resonances that result in high losses.Accordingly, fibers with spaced-apart cladding capillaries may be referred to as ‘‘nodeless antiresonant hollow core fibers”.

[0011] The arrangement of the cladding capillaries 104 in a ring around the inside of the tubular outer cladding 102 creates a central space, cavity, or void within the fiber, also with its longitudinal axis parallel to those of the outer cladding 102 and the cladding capillaries 104, which is the fiber’s hollow core 106. The hollow core 106 is bounded by the inwardly facing parts of the outer surfaces of the cladding capillaries 104. This is the core boundary, and the material (glass or polymer, for example) of the capillary walls that make up this boundary provides the required antiresonance optical guidance effect or mechanism. The cladding capillaries 104 have a thickness, t, at the core boundary which defines the wavelength for which antiresonant optical guiding occurs in the ARF.

[0012] In the second example, shown in FIG. 2, each primary cladding capillary 104 has a secondary, smaller capillary 204 nested inside it, bonded to the inner surface of the primary cladding capillary 104, in this example at the same azimuthal location 108 as the point of bonding between the primary cladding capillary’ 104 and the outer cladding 102. These additional smaller capillaries 204 can reduce the optical loss. ARF designs of this type, with secondary capillaries, may be referred to as “nested antiresonant nodeless fibers” (NANFs) (TM).

[0013] The third example, shown in FIG. 3, has two smaller cladding capillaries 204, 304 nested inside each cladding capillary 104. As with the example shown in FIG. 2, each of the smaller capillaries 204, 304 is bonded to the inner surface of the immediately larger capillary at the same azimuthal location as the point of bonding between the primary' cladding capillary' 104 and the outer cladding 102. In this example, the smaller capillary' 304 may be referred to as the secondary cladding capillary and the smallest capillary 204 may be referred to as the tertiary cladding capillary. The tertiary cladding capillary 204 is bonded to the inner surface of the secondary' cladding capillary 304 and the secondary cladding capillary' 304 is bonded to the inner surface of the primary cladding capillary' 104. ARF designs of this type, with secondary and tertiary cladding capillaries may be referred to as “double-nested antiresonant nodeless fibers” (DNANFs). In yet further examples (not shown in the drawings) there may be a different configuration of cladding capillaries. For example, there may be smaller further capillaries, within the tertiary' capillary' 204 toprovide further levels of nesting and / or there may be a plurality of secondary cladding capillaries within each primary cladding capillary, each secondary cladding capillary being bonded to the inner surface of the primary cladding capillary at a different azimuthal location and / or each primary cladding capillary may have an internal structure (e g. one or more dividing walls).

[0014] All of the examples shown in FIGs. 1-3 comprise five primary cladding capillaries 104 and hence have five-fold rotational symmetry. Furthermore, all the cladding capillaries are circular in cross-section. In other examples, there may be a different number of primary cladding capillaries surrounding the core (e.g. four, six, seven, eight, nine or ten) and / or the cladding capillaries may not be of circular cross-section. Additionally, whilst in the examples of FIGs. 1-3, all the primary cladding capillaries 104 are of the same size and shape, in other examples, the primary cladding capillaries within the outer cladding 102 may not all be the same size and / or shape.

[0015] Regardless of the precise details of the structure, it will be apparent from FIGs. 1-3 and the description above that an ARF lacks continuous circular symmetry. When splicing two lengths of ARF together, any misalignment between the cladding capillaries (which may be referred to collectively as the microstructure of the fiber) will increase the optical propagation loss of the splice. Alignment requires careful rotational adjustment about the longitudinal axis of the fiber in order to bring the structural features into the same orientation, and this can be awkward and time-consuming to achieve.

[0016] Most existing splicers (or splicing apparatus) are not designed for use with ARF and as a result cannot perform the necessary azimuthal alignment to produce a low loss splice when splicing ARF. The rare examples of splicers that can perform azimuthal alignment, and hence are more suitable for splicing ARF, involve observation or detection of the end facets with a camera and an example arrangement is show n in FIG. 4. To perform end-view observation, a mirror 402 is temporarily inserted between the end-facets 404, 406 that are to be spliced. A light source 408 couples light into the fiber 410 to illuminate the end-facet 404 and it is imaged by a camera 412 via the mirror 402 and a lens 414. The fiber 410 can then be rotated into a pre-defined orientation and the process is then repeated for the second fiber 416 using a second light source 418 (to couple light into the second fiber 416) and either a second mirror (not shown in FIG. 4) or by rotating the mirror 402 through 90°. Such apparatus is slow, costly, delicate and bulky (e.g. because of the moving mirror) and therefore largely suitable only for interior laboratory and clean-room use rather than use in the field. Often, however, fiber splicing needs to be performed in the field such as duringthe installation of optical fiber communications networks. Applications of this type require equipment which is preferably robust, portable, simple, and quick to operate (e.g. since there may be 60 or more optical fibers in any cable).

[0017] Described herein are methods and apparatus for aligning fibers which lack continuous circular symmetry such as hollow core fibers (e.g. ARF) and multi-core solid core fibers. The fiber analysis tool described herein images a cleaved fiber end face and performs image analysis on a captured image of the end face to determine both a rotational alignment offset and a lateral (x / y) alignment offset. The resulting offsets are stored for communication to a splicer. The fiber analysis tool does not perform any alignment (neither lateral nor rotational alignment, such that the fiber remains in the same position in a fiber holder throughout) but instead the offsets which are determined by the fiber analysis tool and communicated to the splicer, are used by the splicer to quickly and accurately align two fibers for splicing without any requirement for end or side viewing of the fiber on the splicer for purposes of lateral or rotational alignment of the two fibers. It will be appreciated that whilst the lateral and rotational alignment can be performed without any viewing of the fibers, the splicer may still perform some side viewing of the fiber for other reasons (e.g. to determine the position of the end faces or to assess splice quality7after splicing) or to perform a subsequent fine alignment operation.

[0018] Use of the fiber analysis tool described herein, therefore reduces the time taken to align two fibers for splicing on a splicer and reduces the complexity of the splicer. The splicer only needs a rotational alignment stage for one of the two fibers and does not need to include moving mirrors, such as shown in FIG. 4 and described above. This makes the splicer more robust, portable, simple, and quick to operate and hence it is much more suited to field operation. Use of the fiber analysis tool also removes the need for any manual alignment or manual rotation of the fiber, which improves the overall alignment and reduces the time taken to align the fibers for splicing. In addition, by using the fiber analysis tool, both rotational and lateral alignment are performed by the splicer and any corecladding concentricity error is compensated for. This further improves the alignment of fibers when splicing and hence results in reduced splice loss.

[0019] The rotational and lateral alignment offsets and the core-cladding concentricity error can be described with reference to FIG. 5 which shows a further transverse cross-sectional view of an example ARF 500. Whilst the methods are described with reference to ARF, as noted above the fiber analysis tool (and the methods describedherein) are applicable to any fiber which lacks continuous circular symmetry such as hollow core fibers (including ARF) and multi-core solid core fibers.

[0020] In FIG. 5 the cladding 502 is show n with a more representative thickness than the examples shown in FIGs. 1-3 and the center of the cladding (i.e. the central point of either the outer diameter 504 or the inner diameter 505 of the cladding 502) is marked with a solid cross 506. It will be appreciated that the central point of the outer diameter 504 of the cladding 502 and the central point of the inner diameter 505 of the cladding 502 may be close to each other or may be aligned dependent upon any thickness variations in the cladding 502. One or other definition of the center of the cladding may be used dependent upon which is easier to image (e.g. easier to focus on) in a particular implementation. A dotted circle 508 in FIG. 5 shows the position of the hollow" core within the fiber and the position of the hollow" core (and hence circle 508) is defined by the innermost points (i.e. the points closest to the center of the fiber) of each of the largest capillaries 510. The center of the core (i.e. the center of dotted circle 508) is marked with a dotted cross 512. The corecladding concentricity error is the amount that the core is off-center relative to the outer cladding glass (i.e. cladding 502) and so corresponds to the offset of the center of the core (dotted cross 512) from the center of the cladding (solid cross 506). If there is no corecladding concentricity error, then the two crosses 506. 512 are aligned exactly. In the example shown in FIG. 5, the center of the core (dotted cross 512) is slightly to the left of the center of the cladding (solid cross 506) and this separation, L, is the lateral alignment offset. In this example the offset, L, is in the horizonal, x, direction and in other examples it may be in the vertical, y, direction or the two crosses may be offset in both horizontal and vertical directions. Irrespective of the direction of the offset, this is referred herein to as the lateral alignment offset. The lateral alignment offset, L, is a vector and comprises both a magnitude and a direction. The direction may be defined relative to the horizontal, x, plane 514 when the fiber 500 is held in a fiber holder 600, e g. as shown in FIG. 6, or it may be defined relative to a second plane 516 that is defined relative to the internal microstructure of the fiber, as described below. The horizontal plane 514 may be parallel to a bottom surface 601 of the fiber holder 600.

[0021] FIG. 6 shows a schematic diagram of the ARF 500 in an example fiber holder 600. The fiber holder 600 comprises a base 602 and a clamp 604 that is attached to the base 602 by a hinge 606. The clamp 604 can rotate about the hinge 606 (as indicated by the double ended arrow") between a closed position (as shown) and an open position where the distal end of the clamp is no longer in contact w ith, or proximate to, the base 602. Theclamp 604 may be held in the closed position using magnets, friction or other mechanism (e.g. springs). The base 602 comprises a groove 608 which is of an appropriate size to hold the fiber 500 and different fiber holders may have different sized grooves (e.g. in terms of width and depth) to accommodate different sizes of fibers. The fiber 500 is inserted into the fiber holder 600 by rotating the clamp 604 away from the base 602 about the hinge 606 into the open position. This exposes the full length of the groove 608 such that the fiber can be placed into it by a user. The fiber 500 is then held in place in the fiber holder 600 by rotating the clamp 604 about the hinge 606 so that the distal end of the clamp is close to, or in contact with, the base 602. The clamp 604 applies downwards pressure (in the orientation shown in FIG. 6) on the fiber (e.g. either to the glass or to the coating depending upon how much coating has been stripped and the position of the clamp) to hold it in place such that it cannot slide along the groove 608 (i.e. along its longitudinal axis) or rotate within the groove 608 (i.e. about its longitudinal axis). In the example shown in FIG. 6, the clamp 604 comprises a corresponding groove 610 and the angled sides of this groove 610 apply the downwards pressure to the fiber. In other examples, the clamp 604 may not include a groove but instead may comprise a conformable pad (e.g. made of rubber) which applies the downwards pressure on the fiber to hold it securely in the groove 608 on the base 602.

[0022] The rotational offset, 0. may be defined relative to the reference plane 514 (which may be the horizontal plane, as described above) and is defined as the angle between that plane 514 and the second plane that is defined with respect to the internal microstructure of the fiber. As the internal microstructure will differ between fiber types, the reference features used to define this second plane will differ between fiber types and any suitable features may be used. In order that the rotational offset can be used to rotationally align two fibers for splicing, the same reference features are used to define the second plane for both fibers. In the example shown in FIG. 5, the second plane 516 is defined as dividing the gap between two adjacent largest capillaries 510 into two halves, such that the plane 516 is equidistant from both capillaries 510. In the example shown, the angle is measured in an anti-clockwise direction; however, it may be measured in the opposite direction as long as the same direction is used when analyzing both fibers that are to be spliced together.

[0023] Whilst in the examples described above, both offsets are defined relative to a plane 514 that is parallel to the bottom surface of the fiber holder, it will be appreciated that a different reference plane may instead be used, where the reference plane has a fixed position relative to the fiber holder.

[0024] FIG. 7 shows a schematic diagram of a first example fiber analysis tool 700 for use with any fiber which lacks continuous circular symmetry such as hollow core fibers (including ARF) and multi-core solid core fibers. The fiber analysis tool 700 comprises a region 702 for receiving a fiber in a fiber holder (e.g. such as the fiber holder shown in FIG. 6), a camera arrangement 704 arranged to image an end face of the fiber and an image analysis module 706 configured to analyze an image of the end face captured by the camera arrangement 704 and determine a rotational offset and a lateral alignment offset of the fiber in the fiber holder. The camera arrangement 704 comprises lens and focus mechanisms so that it can capture a focused image of the end face of the fiber. The rotational offset and the lateral alignment offset, as determined by the image analysis module 706, are stored for transmission to a splicer. Consequently, the fiber analysis tool 700 may comprise an offset data store 708 for storing the rotational and lateral offsets. These offsets may be stored along with an identifier for the fiber to which they relate. As described above, the fiber analysis tool 700 does not perform any alignment (neither lateral nor rotational alignment) and so does not include any means of repositioning the fiber within the fiber holder.

[0025] FIG. 7 also shows a dotted line 710 which indicates the position of the longitudinal axis of a fiber in a fiber holder when positioned in the region 702 for receiving the fiber holder. In the example shown in FIG. 7, the camera arrangement 704 is positioned on this axis to enable it to image the end face of the fiber. In an alternative arrangement, shown in FIG. 8, a mirror 802 is positioned on the fiber axis (dotted line 710) and the camera arrangement 704 is position off-axis. This may result in a more compact fiber analysis tool 800. The fiber analysis tool 800 shown in FIG. 8 is otherwise the same as the fiber analysis tool 700 described above with reference to FIG. 7.

[0026] As described above, the fiber analysis tool 700, 800 stores the determined rotational and lateral offsets (either or both of which may be zero) for transmission to a splicer. The transmission of the offset data (comprising both the rotational and lateral offsets and optionally an identifier for the fiber or the fiber holder in which the fiber is held) may be transmitted to the splicer in any suitable manner and the fiber analysis tool 700,800 may further comprise a transmitter 712 for transmitting the offset data. In a first example, where the fiber holder includes a data storage device (e.g. in the form of an RFID tag), the offset data may be written to the data storage device in the fiber holder by the transmitter 712 in the fiber analysis tool. In such an example, an identifier for the fiber may not be included in the offset data since the fiber is implicitly identified by being held in the fiber holder to which the data is written. Additionally, in such an example, the fiber analysis tool700, 800 may not comprise an offset data store 708 (as the storage to which the offsets are written is in the fiber holder). In other examples, other wireless protocols may be used by the transmitter 712 to transmit the offset data (including an identifier for the fiber or the fiber holder) to the splicer. Examples of protocols which may be used include Bluetooth™, BLE, WiFi™ and cellular protocols (e.g. 4G or 5G). Dependent upon the technology used, the fiber analysis tool may transmit the offset data directly to the splicer or via an intermediary device (e.g. wireless access point or router) and / or network. In further examples, the transmitter 712 may use a wired connection, rather than a wireless connection, to transmit the offset data (e g. via an Ethernet link either directly or indirectly to the splicer). Where the offset data includes an identifier for the fiber holder, this may be read from the fiber holder by the fiber analysis tool (e.g. using a receiver, not shown in FIGs. 7 and 8) or may be input by a user. Similarly, an identifier for the fiber may be input by a user or read from the fiber itself (e.g. where it is encoded within the microstructure or printed on the fiber coating).

[0027] FIG. 9 is a flow diagram of an example method of operation of a fiber analysis tool as described herein. A fiber holder containing a fiber is received in the fiber analysis tool (block 902). The fiber holder is received by the region 702 for receiving a fiber holder. As described above, the fiber does not have continuous rotational symmetry and may be a hollow core fiber or a multi-core solid-core fiber. The camera arrangement 704 captures an image of the end face of the fiber which protrudes from the fiber holder (block 904) and the image analysis module 706 analyzes the captured image to determine both a rotational offset and a lateral offset of the fiber (block 906). As described above, the lateral offset is the offset of the center of the core from the center of the cladding of the fiber (where the direction of the offset is specified relative to a reference plane that is defined relative to the fiber holder), where the center of the cladding may be defined as the central point of the outer diameter of the cladding or the central point of the inner diameter of the cladding depending upon whether the inner or outer diameter is more visible in a captured image of the end face of the fiber, and where the rotational offset is an angular offset of a predefined feature in the fiber compared to a reference plane that is defined relative to the fiber holder. The same reference plane may be used to define both the offsets or in other examples, the lateral offset may be defined using a first reference plane and the rotational offset may be defined using a second reference plane, where the first and second reference planes are different.

[0028] The offsets may be determined (in block906) as described above with reference to FIG. 5, i.e. by detecting (in the captured image) the outer diameter 504 of the cladding (or inner diameter 505) and identifying its center, by detecting the position of the core (in the captured image) and identifying its center, and by detecting the position of the second plane defined with reference to the internal microstructure of the fiber. The offset between the two detected centers is the lateral offset (with the direction specified with reference to the detected second plane or alternatively with reference to a reference plane) and the rotational offset is the angle between a reference plane and the detected second plane. By defining the lateral offset with reference to the second plane, it simplifies the subsequent alignment where two fibers are first rotationally aligned (i.e. such that their second planes are aligned) and then laterally aligned.

[0029] Having determined the offsets (in block 906), these offsets are stored for transmission to a splicer (block 908). As described above, the operation of storing the offsets may transmit the offsets to the splicer (e.g. where the offsets are stored on the fiber holder which will subsequently be transferred from the fiber analysis tool to the splicer by a user) or there may be a separate operation of transmission of the offsets (block 910).

[0030] As described above, at no point during the method of FIG. 9, is the fiber removed from, or repositioned in, the fiber holder and so the position and orientation of the fiber is maintained throughout. Instead, the fiber is subsequently orientated so that the internal structure is aligned with that of a second fiber by a splicer, using the offset data transmitted to it by the fiber analysis tool, prior to splicing. FIG. 10 shows a method of operation of a splicer that works in conjunction with the fiber analysis tool described herein. The splicer receives two fiber holders, one containing a first fiber and one containing a second fiber (blocks 1002A and 1002B) and also receives offset data for both fibers (blocks 1004A and 1004B). Dependent on how the transmission is performed by the fiber analysis tool (in block 908 or 910), the offset data may be received with the fiber holder, or separately, and where received separately it may be received before or after the fiber holders are inserted into the splicer. The splicer uses the received offset data to align the two fibers, both laterally and rotationally (block 1006) and once aligned, the fibers are spliced together (block 1008).

[0031] The use of the offset data (in block 1006) comprises calculating the required motion of one or both fibers by the splicer to align both the centers of their cores (a lateral, x / y, motion) and the internal microstructure (a rotational motion) and then moving one or both fibers accordingly. The calculation of the required motion takes into consideration therelative placement of the two fiber holders (and hence the two fibers) into the splicer (e.g. referring to the splicer apparatus shown in FIG. 4, whether the fiber holder containing the fiber is on the left or the right of the position where the splice will be formed).

[0032] Using the offset data provided by the fiber analysis tool, the splicer can more accurately align the fibers and produce a lower loss splice. This is because the offset data defines both the rotational orientation of each fiber, which can otherwise be difficult for the splicer to determine for fibers that do not have continuous rotational symmetry, and the offset of the center of the core from the center of the cladding, which is something that is not typically measured and adjusted for when splicing.

[0033] The fiber analysis tool described above may be incorporated into a cleaver (or cleaving apparatus). Fiber cleavers break a fiber to form a flat end face, e.g. for splicing. Cleavers typically operate by scoring the surface of the fiber at the desired cleave location and then applying tension until the fiber breaks along stress lines created by the scoring.The fiber may be placed under a small amount of tension prior to scoring and the tension may be increased after scoring. The resultant end face is ideally without any cracks or chips, or any chips that are present are not close to the core but instead are just at the outer edge of the cladding.

[0034] By including the fiber analysis functionality within a cleaver, it simplifies the overall cleaving and splicing operation and thereby reduces the time taken. This may be particularly important for field operations as a cable may contain large numbers of fibers that require splicing (e.g. following a cable break). Additionally, as described below, it enables analysis of either the cleaved fiber end, or the cleaved discarded end. Furthermore, as the position of the cleaved face is known precisely within the cleaver and is consistent between cleaving operations, it reduces time taken to focus the camera arrangement.

[0035] FIG. 11 shows a schematic diagram of a first example combined cleaver and fiber analysis tool 1100 for use with any fiber which lacks continuous circular symmetry such as hollow core fibers (including ARF) and multi-core solid core fibers. The combined cleaver and fiber analysis tool 1100 shown in FIG. 11 is a variation on that shown in FIG. 7 and described above; however, in other examples it could include a mirror 802 and be a variation on that show n in FIG. 8 and described above.

[0036] In addition to the elements described above with reference to FIG. 7, the combined cleaver and fiber analysis tool 1100 comprises cleaving apparatus 1102. The cleaving apparatus comprises any suitable apparatus for cleaving a fiber and an example is show n in FIG. 12. In the example shown in FIG. 12, the cleaving apparatus 1102 comprisestwo clamps 1202, 1204 configured to clamp the fiber (where the position of the longitudinal axis of the fiber is shown by the dotted line 11 10), atensioning mechanism 1206 and a blade 1208. The tensioning mechanism 1206 is connected to one or both of the clamps and is arranged to apply tension to the fiber when held by the two clamps. The blade 1208 is moveable between a first position (shown in FIG. 12) where it is distant from the fiber and a second position where it is in contact with the outer edge of the fiber cladding between the two clamps. The cleaving apparatus 1102 may comprise additional elements not shown in FIG. 12. In a variation on that described above, one of the two clamps 1202, 1204 may not be part of the cleaving apparatus 1102 but instead part of the fiber holder (e.g. clamp 604 in FIG. 6). Where the first clamp 1202 is part of the fiber holder, the tensioning mechanism 1206 is connected to the region 702 for receiving the fiber holder rather than to the clamp 604 directly.

[0037] In the combined cleaver and fiber analysis tool 1100 shown in FIG. 11, the region 702 for receiving the fiber in a fiber holder is mounted on a movable stage or mechanism, such that after cleaving, the region 702 (and hence the fiber holder holding the cleaved fiber) can be moved to a second position 702’ (marked with a dotted outline in FIG. 11). In the initial (or first) position of the region 702, the longitudinal axis of a fiber when held in the fiber holder (shown by dotted line 1110) is aligned with the cleaving apparatus 1102, whereas in the second position 702’, the longitudinal axis of a fiber when held in the fiber holder (shown by dotted line 710) is aligned with the camera arrangement 704.

[0038] In the combined cleaver and fiber analysis tool 1100 shown in FIG. 11, the fiber holder moves laterally on the movable stage or mechanism between the initial position and the second position, as indicated by arrow 1104. In contrast, in the second example combined cleaver and fiber analysis tool 1300 shown in FIG. 13, the fiber holder rotates on the movable stage or mechanism between the initial position and the second position, as indicated by arrow 1304. This rotation is not about the longitudinal axis 1310 of the fiber but about an axis that is perpendicular to both the longitudinal axis 1310 of the fiber and to the bottom surface 601 of the fiber holder. In the example of FIG. 13, the rotation is about the point indicated by arrow 1306. As shown in FIGs. 11 and 13, the movement of the region 702 for receiving the fiber holder (and hence the motion of the fiber holder itself in use) keeps the fiber holder in the same plane in both examples (i.e. the motion is within the plane of the drawings).

[0039] FIG. 14 is a flow diagram of an example method of operation of a combined cleaver and fiber analysis tool such as shown in FIGs. 11 and 13. The method of FIG. 14 isa variation on the method of FIG. 9 described above. A fiber holder holding containing a fiber is received in the combined cleaver and fiber analysis tool (block 902). The fiber holder is received by the region 702 for receiving a fiber holder in its initial position. As described above, the fiber does not have continuous rotational symmetry and may be a hollow core fiber or a multi-core solid-core fiber. Before the camera arrangement 704 captures an image (in block 904), the fiber is cleaved to form an end face (block 1402) and then the fiber holder is moved to a second position 702’ (block 1404). As described above, in this second position 702’, the newly cleaved end face is aligned with the camera arrangement 704. The method then proceeds as described above with reference to FIG. 9.

[0040] In the combined cleaver and fiber analysis tools 1100, 1300 shown in FIGs. 11 and 13, the camera arrangement 704 images the end face of the cleaved fiber that is held in the fiber holder and is ultimately spliced with another fiber in the method of FIG. 12. FIG. 15 shows a schematic diagram of a third example combined cleaver and fiber analysis tool 1500 in which it is the end face of the fiber end that has been cleaved off the fiber, i.e. the discarded end of the cleaved fiber, that is imaged and used to determine the lateral and rotational offsets of the cleaved fiber. Instead of moving the fiber holder on a movable stage or mechanism, the clamp 1202 within the cleaving apparatus 1102 that holds the end that is cleaved off the fiber is instead mounted on a movable stage or mechanism. This enables the clamp to move from its initial cleaving position which is aligned with the longitudinal axis of the fiber in the fiber holder, to a second position 1202’ in which the longitudinal axis 1510 of the discarded end is aligned with the camera arrangement 704. In the example shown in FIG. 15, the movement of the clamp is a rotation (as indicated by arrow 1502); however, in other examples it may be a lateral movement (e.g. analogous to that shown in FIG. 1 1 but for the clamp 1202 rather than the region 702 for receiving the fiber holder).

[0041] FIG. 16 is a flow diagram of an example method of operation of a combined cleaver and fiber analysis tool such as shown in FIG. 15. The method of FIG. 16 is a variation on the method of FIG. 14 described above with a small number of differences. Firstly, instead of moving the fiber holder (in block 1404), the clamp holding the discarded end is moved into the second position (block 1602). Secondly, instead of capturing an image of the cleaved end of the fiber (in block 904), an image is captured of the cleaved end face of the discarded end of the fiber (block 1604). Thirdly, when performing the analysis (in block 906), an additional step is performed. Having calculated the offsets (rotational and lateral) for the discarded end, these are translated into a rotational and lateral offset of the cleaved fiber end. This translation comprises a reflection operation since the cleaved endface of the discarded end is a mirror image of the cleaved end face of the fiber in the fiber holder. Otherwise the method proceeds as described above with reference to FIGs. 9 and 14.

[0042] Imaging the discarded end, rather than the cleaved end of the fiber in the fiber holder, may reduce the mechanical complexity of the tool since the length of fiber being moved or rotated is very short (e.g. a few centimeters at most) and light. It may also enable parallelization of the process since the capturing of the image and analysis to determine the offsets may be performed in parallel with the user removing the fiber holder from the tool and transferring it to the splicer. As noted above, this reduction in process time may be particularly beneficial when performing large numbers of cleaving and splicing operations, e.g. following a cable break.

[0043] As described above, the offsets that are determined using the fiber analysis tool or combined cleaver and fiber analysis tool described herein, are transmitted to a splicer for both a first and a second fiber that are to be spliced together and then used to align the two fibers. The alignment of the two fibers may be performed solely based on the offset data (in block 1006) without any need for side / end viewing to assist with alignment. However, in some implementations the splicer may additionally use side-view imaging as part of the alignment process.

[0044] In the examples described above, the methods of FIGs. 9, 14 and 16 are performed by the fiber analysis tool or by the combined cleaver and fiber analysis tool. In a variation of this, however, some of the method steps may be performed by the splicer (e.g. as part of the method of FIG. 12). For example, the fiber analysis tool or by the combined cleaver and fiber analysis tool may store and transmit the captured image of the end face to the splicer (instead of the offsets) and the image analysis and determination of the offsets (in block 906) may be performed by an image analysis module in the splicer. This may enable the methods described herein to be implemented using fiber analysis tools or combined cleaver and fiber analysis tools that are not configured to perform the image analysis and offset determination.

[0045] The image analysis module 706 described above may be a computing-based device that executes image analysis software to analyze the captured image of the end face and determine both the lateral and rotational offset. FIG. 17 shows an example implementation of the image analysis module 706. The image analysis module 706 comprises one or more processors 1702 which are microprocessors, controllers or any other suitable type of processors for processing computer executable instructions to control the operation of the device in order to execute image analysis software 1704. In someexamples, for example where a system on a chip architecture is used, the processors 1702 include one or more fixed function blocks (also referred to as accelerators) which implement a part of the method of image analysis in hardware (rather than software or firmware). Platform software comprising an operating system, or any other suitable platform software, may be provided at the computing-based device to enable the image analysis software 1704 to be executed on the device.

[0046] The computer executable instructions are provided using any computer- readable media that is accessible by the image processing module 706. Computer-readable media includes, for example, computer storage media such as memory 1706 and communications media. Computer storage media, such as memory 1706. 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, compact disc read only memory' (CD-ROM), digital versatile disks (DVD) or other 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 does 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 1706) is shown within the image analysis module 706 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 1708). The memory 1706 may also comprise the offset data store 708 and an image store 1712 arranged to store the images captured by the camera arrangement 704 and received by the image analysis module 706 via an input / output interface 1710.

[0047] Alternatively or in addition to the other examples described herein, examples include any combination of the following clauses:

[0048] Clause A: A combined cleaver and fiber analysis tool for use with fibers lacking continuous rotational symmetry, the tool comprising: a region for receiving a fiberholder; cleaving apparatus arranged to cleave a fiber held in the fiber holder; a camera arrangement arranged to image a cleaved end face formed by the cleaving apparatus; and an image analysis module configured to analyze an image of the cleaved end face captured by the camera arrangement, determine a rotational offsets and a lateral offset of the fiber in the fiber holder and store the offsets for transmission to a splicer.

[0049] Clause B: A fiber analysis tool for use with fibers lacking continuous rotational symmetry, the tool comprising: a region for receiving a fiber holder; a camera arrangement arranged to image a cleaved end face of a fiber held in the fiber holder, wherein the fiber lacks continuous rotational symmetry; and an image analysis module configured to analyze an image of the cleaved end face captured by the camera arrangement, determine a rotational offsets and a lateral offset of the fiber in the fiber holder and store the offsets for transmission to a splicer.

[0050] Clause C: The tool according to clause A or clause B, further comprising: a transmitter configured to transmit the offsets to the splicer.

[0051] Clause D: The tool according to any of clauses A-C, wherein the image analysis module is configured to store the offsets into a memory in the fiber holder.

[0052] Clause E: The tool according to any of clauses A-D, wherein the fiber remains in a constant position in the fiber holder and is not moved within the fiber holder by the tool.

[0053] Clause F: The tool according to any of clauses A-E, wherein the camera arrangement is arranged to image a cleaved end face of the fiber in the fiber holder.

[0054] Clause G: The tool according to clause A or any of clauses B-F when dependent upon clause A, wherein the region for receiving the fiber holder is movable between an initial position aligned with the cleaving apparatus and a second position aligned with the camera arrangement.

[0055] Clause H: The tool according to clause A or any of clauses B-F when dependent upon clause A, wherein the camera arrangement is arranged to image a cleaved end face of a portion of fiber cleaved from the fiber in the fiber holder.

[0056] Clause I: The tool according to clause H, wherein the cleaving apparatus comprises a first clamp, wherein the first clamp is movable between an initial position aligned with the region for receiving the fiber holder and a second position aligned with the camera arrangement.

[0057] Clause J: A method comprising: receiving, by a combined cleaver and fiber analysis tool, a fiber holder containing a fiber lacking continuous rotational symmetry;cleaving, by the combined cleaver and fiber analysis tool, the fiber to form an end face; capturing, by the combined cleaver and fiber analysis tool, an image of the end face; analyzing the captured image to determine a rotational offset and a lateral offset of the fiber in the fiber holder; and storing the offsets for use by a splicer to align the fiber to a second fiber prior to splicing.

[0058] Clause K: A method comprising: receiving, by a fiber analysis tool, a fiber holder containing a fiber lacking continuous rotational symmetry; capturing, by the fiber analysis tool, an image of a cleaved end face of the fiber; analyzing the captured image to determine a rotational offset and a lateral offset of the fiber in the fiber holder; and storing the offsets for use by a splicer to align the fiber to a second fiber prior to splicing.

[0059] Clause L: The method of clause J or K, further comprising: transmitting the offsets to a splicer.

[0060] Clause M: The method of any of clauses J-L. further comprising: storing the offsets into a memory in the fiber holder.

[0061] Clause N: The method of any of clauses J-M, wherein capturing an image of the end face comprises: capturing an image of the end face of the fiber in the fiber holder.

[0062] Clause O: The method of clause N when dependent upon clause J, further comprising, prior to capturing the image, moving the fiber holder from an initial position aligned with cleaving apparatus in the combined cleaver and fiber analysis tool to a second position aligned with a camera arrangement in the combined cleaver and fiber analysis tool.

[0063] Clause P: The method of any of clauses J and L-0 when dependent upon clause J, wherein capturing an image of the end face comprises: capturing an image of the end face of a portion of fiber cleaved from the fiber in the fiber holder.

[0064] Clause Q: The method of clause P, further comprising, prior to capturing the image, moving a clamp in the combined cleaver and fiber analysis tool from an initial position aligned with the fiber holder to a second position aligned with a camera arrangement in the combined cleaver and fiber analysis tool.

[0065] Clause R: The method of any of clauses J-Q, wherein the fiber is a hollow core fiber.

[0066] Clause S: The method of clause R, wherein the fiber is an antiresonant hollow core fiber.

[0067] Clause T: The method of any of clauses J-Q. wherein the fiber is a multicore, solid core, fiber.

[0068] Clause U: A method of splicing a first fiber and a second fiber, both fibers lacking continuous rotational symmetry, the method comprising: receiving, at a splicer, a first fiber holder containing the first fiber and a second fiber holder containing the second fiber; receiving, at the splicer, offset data for the first and second fibers, wherein the offset data is generated using the method of any of clauses J-T; aligning the first and second fibers laterally and rotationally using the received offset data; and splicing the aligned first and second fibers together.

[0069] Clause V : The method according to clause U, wherein receiving, at the splicer, offset data for the first and second fibers comprises: reading, at the splicer, offset data for the first and second fibers from memories in the first and second fiber holders.

[0070] Some aspects of 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.

[0071] 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 dow nload 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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

CLAIMSWhat is claimed is:

1. A combined cleaver and fiber analysis tool for use with fibers lacking continuous rotational symmetry', the tool comprising: a region for receiving a fiber holder; cleaving apparatus arranged to cleave a fiber held in the fiber holder; a camera arrangement arranged to image a cleaved end face formed by the cleaving apparatus; and an image analysis module configured to analyze an image of the cleaved end face captured by the camera arrangement, determine a rotational offsets and a lateral offset of the fiber in the fiber holder and store the offsets for transmission to a splicer.

2. The combined cleaver and fiber analysis tool according to claim 1, further comprising: a transmitter configured to transmit the offsets to the splicer.

3. The combined cleaver and fiber analysis tool according to claim 1, wherein the image analysis module is configured to store the offsets into a memory in the fiber holder.

4. The combined cleaver and fiber analysis tool according to claim 1, wherein the fiber remains in a constant position in the fiber holder and is not moved within the fiber holder by the combined cleaver and fiber analysis tool.

5. The combined cleaver and fiber analysis tool according to claim 1, wherein the camera arrangement is arranged to image a cleaved end face of the fiber in the fiber holder.

6. The combined cleaver and fiber analysis tool according to claim 1 , wherein the region for receiving the fiber holder is movable between an initial position aligned with the cleaving apparatus and a second position aligned with the camera arrangement.

7. The combined cleaver and fiber analysis tool according to claim 1, wherein the camera arrangement is arranged to image a cleaved end face of a portion of fiber cleaved from the fiber in the fiber holder.

8. The combined cleaver and fiber analysis tool according to claim 7, wherein the cleaving apparatus comprises a first clamp, wherein the first clamp is movable between an initial position aligned with the region for receiving the fiber holder and a second position aligned with the camera arrangement.

9. A method comprising:receiving, by a combined cleaver and fiber analysis tool, a fiber holder containing a fiber lacking continuous rotational symmetry; cleaving, by the combined cleaver and fiber analysis tool, the fiber to form an end face; capturing, by the combined cleaver and fiber analysis tool, an image of the end face; analyzing the captured image to determine a rotational offset and a lateral offset of the fiber in the fiber holder; and storing the offsets for use by a splicer to align the fiber to a second fiber prior to splicing.

10. The method of claim 9. further comprising: transmitting the offsets to a splicer.

11. The method of claim 9, wherein the fiber is a hollow core fiber.

12. The method of claim 11, wherein the fiber is an antiresonant hollow core fiber.

13. The method of claim 9, wherein the fiber is a multi-core, solid core, fiber.

14. A method of splicing a first fiber and a second fiber, both fibers lacking continuous rotational symmetry, the method comprising: receiving, at a splicer, a first fiber holder containing the first fiber and a second fiber holder containing the second fiber; receiving, at the splicer, offset data for the first and second fibers, wherein the offset data is generated using the method of claim 9; aligning the first and second fibers laterally and rotationally using the received offset data; and splicing the aligned first and second fibers together.

15. The method according to claim 14, wherein receiving, at the splicer, offset data for the first and second fibers comprises: reading, at the splicer, offset data for the first and second fibers from memories in the first and second fiber holders.

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