Enclosure for fibre optic cables and a method of using the same

Abstract

An enclosure (120) for routing a fibre optic cable (190) for a telecommunications network (100), the enclosure comprising a / an: routing member (310) for receiving and routing a fibre optic cable (190) within the enclosure; securing structure (180) for securing the fibre optic cable within the routing member; grating (240) for generating a Mechanically Induced Filter, MIF, in the fibre optic cable; urging member (180) configured to urge the grating against the fibre optic cable thereby to generate the MIF within said fibre optic cable; translation mechanism (230) configured to translate the urging member and the securing structure between: a first arrangement, in which the grating is urged against the fibre optic cable when said fibre optic cable is routed in the routing member, and in which the securing structure secures the fibre optic cable; and a second arrangement, in which the grating is not urged against the fibre optic cable when said fibre optic cable is routed in the routing member, the MIF thereby being absent from the fibre optic cable (540-2), and the fibre optic cable is unsecured by the securing structure.

Description

[0001] ENCLOSURE FOR FIBRE OPTIC CABLES AND A METHOD OF USING THE SAME

[0002] Field of Invention

[0003] The present invention relates to an enclosure for fibre optic cables for a fibre optic telecommunications network, a fibre optic telecommunications network incorporating said enclosure, and a method of operating the fibre optic telecommunications network, and in particular where said enclosure comprises a grating for inducing a Mechanically-Induced Filter (MIF).

[0004] Background

[0005] Large-scale fibre optic networks, as used in wide-area fixed-access telecommunications, are complex, and the infrastructure required to establish such networks may be difficult to access. Notwithstanding, such networks require engineer intervention for maintenance, decommissioning and installation.

[0006] In turn, identifying and locating specific network features (e.g. fibre optic cables, connectors, splitters, switches, splice trays, filters and other components, as well as faults and rogue elements) may pose a considerable challenge.

[0007] An Optical Time Domain Reflectometer (OTDR) is a diagnostic device, used in fibre optic networks, that injects an optical pulse (or a “diagnostic signal”) and measures the arrival time of (and, by inference, a distance travelled by) light reflected as a result of Fresnel back-reflections and Rayleigh backscatter from fibre optic cables and reflections from connectors, components and other discontinuities in the network. A resultant OTDR trace is produced in which features, and their state, can be identified from characteristics of detected reflections.

[0008] Attenuation of a pulse of light through a fibre optic cable may be used to help distinguish between different fibre optic lines, since - all else being equal - attenuation is predominantly a function of the length of a fibre optic cable. However, where two fibre optic lines have sufficiently identical lengths, this method cannot distinguish between such lines, and is one such limitation of OTDR.

[0009] Once the correct fibre optic cable has been identified, engineer intervention may be performed. However, tools - including OTDR - to detect whether the fibre optic network has been made good ( / .e. returned to a fully operational and / or best-practice state) after an intervention are limited in their efficacy of locating and identifying improper or incomplete interventions.

[0010] It is an aim of the present invention to at least alleviate some of the aforementioned problems. Statements of Invention

[0011] According to a first aspect of the present invention, there is provided: an enclosure for routing a fibre optic cable for a telecommunications network, the enclosure comprising a / an: routing member for receiving and routing a fibre optic cable within the enclosure; securing structure for securing the fibre optic cable within the routing member; grating for generating a Mechanically Induced Filter, MIF, in the fibre optic cable; urging member configured to urge the grating against the fibre optic cable thereby to generate the MIF within said fibre optic cable; translation mechanism configured to translate the urging member and the securing structure between: a first arrangement, in which the grating is urged against the fibre optic cable when said fibre optic cable is routed in the routing member, and in which the securing structure secures the fibre optic cable; and a second arrangement, in which the grating is not urged against the fibre optic cable when said fibre optic cable is routed in the routing member, the MIF thereby being absent from the fibre optic cable, and the fibre optic cable is unsecured by the securing structure.

[0012] As used herein, the fibre optic cable being “secured” by the securing structure preferably connotes the fibre optic cable being constrained, fastened, enclosed, protected, shielded, inaccessible and / or sealed, and the fibre optic cable being “unsecured” in turn preferably connotes the fibre optic cable being loose, accessible, unshielded, unsealed, exposed, disengaged and / or unfastened.

[0013] Optionally, the urging member and the securing structure are the same entity or are different. Optionally, the routing member is in the form of a groove, slot, channel, duct, pipe, tube and / or baffle. Optionally, the grating, translation mechanism and urging member are arranged to clamp the fibre optic cable against the routing member, and more preferably against a wall or a base of the routing member. Preferably, the grating is engaged (or fixed) to the securing structure, translation mechanism and / or urging member. Optionally, the translation mechanism comprises a: tracked, sliding and / or rail mechanism; screw; piston; hinge or pivot, and / or compliant (or flexible or elastic) structure. Optionally, the grating is fixed relative to the routing member.

[0014] Preferably, the translation mechanism is further configured to translate the grating between the: first arrangement, in which the grating abuts the fibre optic cable; second arrangement, in which the grating is arranged apart from the fibre optic cable. Preferably, the grating is configured to be urged against the fibre optic cable by the urging member only when said grating is in the first arrangement, and not when the grating is in the second arrangement. Preferably, at least two of the grating, securing structure and / or urging member are coupled to the translation mechanism so as simultaneously to be translated between the first and second arrangements. Optionally, the translation mechanism is configured to translate, the grating, urging member and / or the securing structure linearly, and optionally only linearly. Optionally, the translation mechanism is configured orbitally to rotate the grating, urging member and / or the securing structure. Preferably, the grating is configured (by appropriate dimensioning, orientation and alignment) to be received, at least in part, into the routing member when in the first arrangement. Preferably, the grating is oversized relative to a depth of the routing member, less a gauge of the fibre optic cable at the point of contact with the grating. Optionally, the securing structure comprises the grating.

[0015] Preferably, the securing structure comprises a cover, shield, door and / or lid for preventing or impeding access to the fibre optic cable when in the first arrangement. Preferably, the first arrangement is a closed, or stowed, state of the securing structure. Preferably, said access is human and / or environmental (e.g. liquid and / or dirt). Optionally, the securing structure comprises an engagement formation for fastening the fibre optic cable within the routing member when in the first arrangement. Optionally, the engagement formation comprises a clamp or vice. Optionally, the engagement formation comprises the grating. Optionally, the securing structure comprises a support formation for supporting the fibre optic cable within the routing member when in the first arrangement. Optionally, the securing structure is a lid, cover or door for the entire enclosure as a whole. Optionally, the securing structure is configured to secure only the fibre optic cable. Optionally, the translation mechanism comprises an opening and closing mechanism for the securing structure. Optionally, the urging member comprises a fastening mechanism for fastening the securing structure in the closed state.

[0016] Preferably, the enclosure comprises a splice tray. Preferably, the splice tray comprises the routing member. Optionally, the splice tray comprises, or is, the securing structure. Optionally, the routing member comprises the securing structure. Optionally, the routing member is provided elsewhere to the splice tray and within the enclosure.

[0017] Preferably, the splice tray comprises the translation mechanism and / or the urging member. Preferably, the splice tray comprises the grating. Preferably, the enclosure comprises a further splice tray. Optionally, the further splice tray is identical to the splice tray, or may be different. Preferably, the further splice tray comprises the, or another of the, grating. Preferably, the grating is arranged on the further splice tray so as to be exposed to the to the fibre optic cable when provided within the routing member of the splice tray. Optionally, the grating is arranged on a side of the further splice tray that is closest to the splice tray. Optionally, the grating is arranged on an underside of the further splice tray, thereby to be exposed to a top-side of the splice tray. Optionally, the grating is arranged on a top-side of the further splice tray, thereby to be exposed to an underside of the splice tray. Optionally, the further splice tray comprises, or is, the securing structure. Optionally, the further splice tray comprises the routing member. Optionally, the translation mechanism is configured bodily to translate the entire splice tray and / or the further splice tray, and / or or to rotate said tray / s.

[0018] Preferably, the further splice tray comprises the, or another of the, translation mechanism and / or urging member. Optionally, the translation mechanism is configured to translate the grating in the plane of the splice tray (or the further splice tray), and more preferably only in said plane. Optionally, the translation mechanism is configured to translate the grating in and out of the plane of the splice tray (or the further splice tray), and more preferably only in and out of said plane.

[0019] Preferably, in the first arrangement, the securing structure is stacked upon the splice tray, or vice versa. Optionally, the splice tray and the further splice tray overlie one another, and may be stacked upon one another. Optionally, in the first arrangement, the securing structure is configured freely to bear down upon the splice tray and / or the further splice tray, or vice versa, the urging member thereby comprising the securing structure as a weight (i.e. the urging member comprises the mass of the securing structure). In this way, gravity may help urge the grating upon the fibre optic cable. Preferably, the grating is the sole point of contact of the securing structure (and / or the splice tray or further splice tray) upon the fibre optic cable. Where the translation mechanism comprises a hinge, for control of mechanical advantage, the grating and the routing member are arranged proximate to, or distally from, said hinge. Where provided proximate to the hinge, the grating and the routing member may be arranged within 50% of the maximum extent of the corresponding splice tray from the hinge, more preferably within 25%, and still more preferably within 10%.

[0020] An enclosure according to any preceding claim, comprising a plurality of the (or other) routing members and / or a plurality of the (or other) gratings, wherein each routing member is configured to receive and to route at least one (optionally, further) fibre optic cable, and wherein, in the first arrangement, each of the gratings is urged against a different one of said fibre optic cables or the same fibre optic cable / s, thereby to generate the MIF therewithin. Optionally, the routing member is configured to receive and to route (e.g. by appropriate dimensioning) a plurality of fibre optic cables. Optionally, the grating is configured (for example, by appropriate sizing, arrangement, orientation, and alignment) simultaneously to compress each of the plurality of fibre optic cables when in the first arrangement. Optionally, at least two (and optionally all) of the gratings are configured simultaneously to compress fibre optic cables in different routing members when in the first arrangement. Optionally, each grating is associated with a different routing member (i.e. thereby to compress only the fibre optic cable / s within the associated routing member). Optionally, at least two (but not all) of the gratings are configured simultaneously to compress fibre optic cables in the same routing member. Optionally, the urging member is the same (single) urging member for all gratings or wherein a different urging member is provided for each grating. Optionally, the translation mechanism is the same (single) translation mechanism for all gratings or wherein a different translation mechanism is provided for each grating. Optionally, each of the gratings are the same, or are different so as generate MIFs having different filtering effects. Optionally, the plurality of gratings differ, at least, as to groove: periodicity; number; depth; and / or orientation (relative to a routing direction of the associated routing member and / or others of the gratings). Optionally, the filtering effects differ as to: filtering extent; and / or filtering wavelength.

[0021] According to another aspect of the invention, there is provided a fibre optic telecommunications network comprising at least one enclosure as described above.

[0022] According to another aspect of the invention, there is provided a method of operating a fibre optic telecommunications network, said network comprising: enclosure for routing a fibre optic cable for the telecommunications network, the enclosure comprising a / an: routing member for receiving and routing a fibre optic cable within the enclosure; securing structure for securing the fibre optic cable within the routing member; grating for generating a Mechanically Induced Filter, MIF, in the fibre optic cable; urging member configured to urge the grating against the fibre optic cable thereby to generate the MIF within said fibre optic cable; translation mechanism configured to translate the urging member and the securing structure between: a first arrangement, in which the grating is urged against the fibre optic cable when said fibre optic cable is routed in the routing member, and in which the securing structure secures the fibre optic cable; and a second arrangement, in which the grating is not urged against the fibre optic cable when said fibre optic cable is routed in the routing member, the MIF thereby being absent from the fibre optic cable, and the fibre optic cable is unsecured by the securing structure; wherein the method comprises the steps of: retrieving a: first test result from a first optical reflectometry test performed upon the fibre optic cable whilst the enclosure is in the first arrangement, thereby to detect a filtering effect of the MIF; and second test result from a second optical reflectometry test performed upon the fibre optic cable whilst the enclosure is in the second arrangement; comparing the first and second test results; identifying, from said comparing, an absence of the filtering effect of the MIF in the second test result; and in response to said identifying, generating an alert that the enclosure is in the second arrangement.

[0023] Preferably, the first, second and third optical reflectometry tests are Optical Time-Domain Reflectometry, OTDR, tests, or may be an Optical Frequency Domain Reflectometry, OFDR, tests. Optionally, the alert comprises a confirmation that the fibre optic cable that is subject to the second arrangement and the fibre optic cable that is subject to the first and second optical reflectometry tests are the same fibre optic cable. Preferably, the method comprises the further step of identifying, from said comparing, a presence of the filtering effect of the MIF in the second test result; and in response to said identifying, generating a notice that the enclosure remains in the first arrangement. Optionally, the method comprises the further steps of: retrieving a third test result from a third optical reflectometry test performed after the second optical reflectometry test and upon the fibre optic cable whilst the enclosure is in the second arrangement; including the third test result in the comparing; further identifying, from said comparing, an absence of the filtering effect of the MIF in the third test result; and in response to said identifying, generating a further alert that the enclosure remains in the second arrangement. Preferably, in response to the further alert performing an intervention upon the enclosure to re-arrange (or restore) the enclosure to the first arrangement. Optionally, the alert and / or the further alert identifies the enclosure and / or fibre optic cable. Optionally, the first, second and / or third optical reflectometry test / s are triggered by a user or are routinely performed. Optionally, the second and / or third optical reflectometry test / s is / are triggered in response to an intervention at the enclosure. Optionally, the second optical reflectometry test is performed before the first optical reflectometry test.

[0024] Optionally, the enclosure comprises, consists, or is a constituent, of a / an: aggregation node; splice node; splitter node; Connectorized Block Terminal; Optical Network Terminal; Optical Distribution Terminal; Optical Distribution Frame; Wavelength Division Multiplexing node; Customer Splice Point; or Optical Line Terminal. Preferably, the fibre optic network is a point-to- multipoint network and / or a Passive Optical Network (PON). Preferably, the fibre optic cable comprises at least one fibre, and may be a single- or multi-core fibre optic cable. Preferably, the routing member is configured, at least, to guide, secure, constrain, and / or protect the fibre optic cable when routed therewithin. Optionally, the grating is provided as a part (integrally or engaged) of the routing member; that is, the routing member may comprise the grating. In this case, the translation mechanism may also form a constituent of the routing member, and may be in the form of the compliant structure. Optionally, the fibre optic cable comprises a splice, wherein the routing member is configured to receive and to arrange said splice so as to be compressed by the grating when in the first arrangement. Preferably, the urging member comprises a: spring; magnet; weight; compression fit; latch; friction fit; clamp; vice; and / or strap, tie or tether. Preferably, the grating is configured to induce a Long-Period Fiber Grating, LPFG, or a Bragg grating more generally, when compressing the fibre optic cable. Preferably, the grating is directly urged against a jacket, a cladding, or a splice of the fibre optic cable. Preferably, the outer jacket of the fibre is removed so as to permit direct compression of the cladding. Preferably, the grating remains outside of a path of light transmissions through the fibre optic cable; that is, the grating is not an in-line filter. Preferably, the grating remains optically uncoupled from the fibre optic cable. Optionally, the grating is removable, and may be interchangeable. Preferably, the filtering effect of the grating is controllable, known, reversible, non-destructive, and / or repeatable. Preferably, the grating is tuned to induce a filtering effect upon (only) a diagnostic signal, and not upon a service signal. Preferably, the service signal is used to communicate a telecommunications service to a user. Preferably, the service signal operates at a service wavelength, and wherein the service wavelength is less than 1625nm and / or more than 1700nm. Preferably, the diagnostic signal does not carry signals for providing a telecommunications service to a user, and is therefore merely for testing and diagnostics, and is operated at a diagnostic wavelength. Preferably, the diagnostic wavelength is within the ll-band or C-band, as defined by the ITU Telecommunication Standardization Sector. Preferably, the diagnostic test wavelength is between 1200nm and 1700nm, and still more preferably between 1625nm and 1675nm, or between 1535nm and 1565nm. Optionally, the filtering effect is partial, and may be at least 10%, 20%, 50%, 70%, or 90%, and may reduce reflected signals to below a noise floor of the optical reflectometry test. Optionally, the filtering effect is total.

[0025] According to yet another aspect of the invention, there is provided a (non-transitory) computer- readable carrier medium comprising a computer program, which, when the computer program is executed by a computer, causes the computer to carry out the method described above.

[0026] The above summary is not intended to describe each illustrated embodiment or every implementation of the subject matter hereof. The invention includes any novel aspects described and / or illustrated herein. The invention also extends to methods and / or apparatus substantially as herein described and / or as illustrated with reference to the accompanying drawings. The invention is also provided as a computer program and / or a computer program product for carrying out any of the methods described herein and / or for embodying any of the apparatus features described herein, and a computer-readable medium storing thereon a program for carrying out any of the methods and / or for embodying any of the apparatus features described herein. Features described as being implemented in hardware may alternatively be implemented in software, and vice versa.

[0027] It should be understood that the individual operations used in the methods of the present teachings may be performed in any order and / or simultaneously, as long as the teaching remains operable. Furthermore, it should be understood that the apparatus and methods of the present teachings can include any number, or all, of the described embodiments, as long as the teaching remains operable. Any apparatus feature may also be provided as a corresponding step of a method, and vice versa. As used herein, means plus function features may alternatively be expressed in terms of their corresponding structure, for example as a suitably-programmed processor.

[0028] Any feature in one aspect of the invention may be applied, in any appropriate combination, to other aspects of the invention. Any, some and / or all features in one aspect can be applied to any, some and / or all features in any other aspect, in any appropriate combination. Particular combinations of the various features described and defined in any aspects of the invention can be implemented and / or supplied and / or used independently.

[0029] As used throughout, the word 'or' can be interpreted in the exclusive and / or inclusive sense, unless otherwise specified.

[0030] The invention extends to an enclosure for fibre optic cables for a fibre optic network, a telecommunications network, and a method of operating a telecommunications network as described herein and / or substantially as illustrated with reference to the accompanying drawings. The present invention is now described, purely by way of example, with reference to the accompanying diagrammatic drawings, in which:

[0031] Figure 1 shows an exemplary fibre optic telecommunications network comprising a plurality of nodes;

[0032] Figure 2 is a detailed schematic representation of one of the nodes comprising a plurality of splice trays;

[0033] Figure 3 is a schematic representation of one of the plurality of splice trays;

[0034] Figures 4a and 4b shows an adjacent pair of the plurality of splice trays in different arrangements; Figures 5a and 5b show schematic OTDR traces corresponding, respectively, to the different arrangements;

[0035] Figure 6 shows a process for operating the fibre optic telecommunications network; and Figure 7 shows an alternative example of one of the plurality of splice trays.

[0036] While various embodiments are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the claimed inventions to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by, at least, the claims.

[0037] Figure 1 is a schematic diagram of an exemplary fibre optic telecommunications network 100, such as for providing wide-area fixed-access broadband network services. In particular, the network 100 is in the form of a Passive Optical Network (PON).

[0038] The network 100 comprises a / an: headend 1 10 comprising an Optical Line Terminal (OLT) and Optical Time Domain Reflectometer (OTDR); plurality of distribution nodes 120; and first 130-1 and second 130-2 Optical Network Terminals (ONTs).

[0039] The aforementioned components are interconnected using an optical link provided by optical fibres 140, 150 (generally represented in Fig. 1 with dashed lines) so as to provide telecommunications services between, at least, the headend 1 10 and the plurality of ONTs 130 via the plurality of distribution nodes 120.

[0040] In more detail, each of the plurality of distribution nodes 120, form enclosures for routing fibre optic cables, and comprises (in sequence downstream from the headend 110) a / an: Optical Distribution Frame 120-1 (ODF); Splitter Node 120-2 (SN); Connectorised Block Terminal 120-3 (CBT); and first 120-4-1 and second 120-4-2 Customer Splice Points (CSPs). Each of the distribution nodes 120 are configured to receive, organise, secure, connect, permit access to, route and distribute fibre optic cables from the headend 1 10 to the ONTs 130.

[0041] The OLT is located, for example, at a local exchange, and is connected to each ONT 130 via the ODF 120-1 , SN 120-2, CBT 120-3, and CSPs 120-4. The OLT and OTDR are operatively connected to a higher-layer network management software application (not shown) comprising an Element Management System (not shown) and / or a Network Management System (not shown). For example, via the network management software application, an operator (e.g. an engineer) of the network 100 may trigger a diagnostic test to be performed by the OTDR.

[0042] The OTDR is an optical reflectometry measuring device for the network 100. The OTDR enables discovery of physical discontinuities ( / .e. breaks in the fibre, faulty connections and splices, excessive fibre bends and other structural deformities) in an optical link. The OTDR is operated by sending a diagnostics signal down the network 100, this results in backscattering and reflections due to the presence of discontinuities in fibre structures. By measuring the time that the diagnostics signal takes to return to the OTDR (from which, distance may be inferred) and the magnitude of the received signal relative to the transmitted signal, a suitably configured OTDR can help determine the location, nature and extent of physical discontinuities. For example, a drop in backscatter to a noise floor may indicate a full break, a small reflection may indicate a connector with an air gap, and a loss (partial or complete) may indicate a loss filter.

[0043] A single fibre spine 140 extends from the headend 1 10 to the ODF 120-1 , which in turn comprises a shelf 150 for routing said fibre spine 140 on to the SN 120-2.

[0044] The SN 120-2 comprises an input splice tray 160, an optical splitter 170, and a plurality of output splice trays 180 (also referred to as “splice cassettes”), including a first splice tray 180-1 , a second splice tray 180-2 and a last splice tray 180-x (where any number of further splice trays are provided between the second and last splice trays). The SN 120-2 receives the fibre spine 140 from the ODF 120-1 at the input splice tray 160 which routes said fibre spine 140 to the optical splitter 170, which in turn splits the fibre spine into a first fibre 190-1 and second fibre 190-2. In turn, the first 190-1 and second 190-2 fibres are routed to the first 180-1 and second 180-2 splice trays, respectively.

[0045] In turn, the first 190-1 and second 190-2 fibres are routed in a corresponding fibre optic cable to the CBT 120-3, and then on to a respective one of the first 120-4-1 and second 120-4-2 CSPs, and then a respective one of the first 130-1 and second 130-2 ONTs.

[0046] Figure 2 is a schematic representation of the SN 120-2 shown in profile.

[0047] The SN 120-2 comprises an enclosure 210, in turn comprising a body (or housing) 210-1 and a lid 210-2, within which the plurality of output splice trays 180 are in a vertically-stacked arrangement mounted to a column 220 via a corresponding hinge 230. The first splice tray 180-1 is arranged as an uppermost splice tray, the second splice tray 180-2 is arranged immediately below, and the last splice tray 180-x is arranged as a bottommost splice tray.

[0048] Figure 3 is a schematic detail view of the first splice 180-1 tray shown in isolation and from above. Figures 4a and 4b are schematic diagrams of the first 180-1 and second 180-2 splice trays shown in cross section (along A-A of Fig. 3) and in isolation, in which the first splice tray is shown stowed and unstowed in Figs 4a and 4b, respectively.

[0049] Each splice tray 180 further comprises a routing member 310 (as best shown in Figs 3 and 4), configured to receive and securely route fibre, and in form of a groove, slot, channel, duct, pipe, tube and / or baffle. The first fibre 190-1 is routed through the first splice tray 180-1 using the constituent first routing member 310-1 , whereas the second fibre 190-2 is routed through the second splice tray 180-2 using the constituent second routing member 310-2. A first splice 320-1 of the first fibre 190-1 is received and secured within the first routing member 310-1 , whereas a second splice 320-2 of the second fibre 190-2 is received and secured within the second routing member 310-2.

[0050] In the example of Figs 1 to 4, the first 180-1 and second 180-2 splice trays, and any of the remaining (but not the last 180-3) splice trays, are effectively identical. To aid differentiation, constituent components of the first 180-1 and second 180-2 splice trays are enumerated according to the same ordinal index of the splice tray comprising said components and the reference numerals are enumerated accordingly (e.g. such that the first splice tray 180-1 comprises the first routing member 310-1 and the first fibre 190-1 , etc.).

[0051] Each hinge 230 acts as a translation mechanism for the associated splice tray, thereby permitting each splice tray to be freely rotated between a first arrangement (as shown in Fig. 2 for all but the first splice tray) - or a stowed position - and a second arrangement - or an unstowed position - in which splice trays are separated to allow access to the fibres 190 stored within, above and / or below.

[0052] In this way, when in the stowed position, the splice trays 180 may act as a structure for securing the fibres 190 routed through adjacent splice trays by acting as a support and / or guard for said fibres.

[0053] As shown in Figs 2 and 4, the first 180-1 and second 180-2 (and indeed all but the last 180-x) splice trays further comprise a grating 240, which, in this example, is provided on an underside of each splice tray. Specifically, the first splice tray 180-1 comprises a first grating 240-1 , and the second splice tray 180-2 comprises a second grating 240-2. A grating of a given splice tray is exposed to the adjacent splice tray below, such that the first grating 240-1 is exposed to the second splice tray 180-2 (and so on for all but the last splice tray 180-x).

[0054] Each grating 240 is a mechanical grating formed of periodic grooves arranged so as to, when forced upon a fibre, mechanically induces a loss filter, or a Mechanically-Induced Filter (MIF), in the form of a Long Period Fibre Grating (LPFG) within the fibre. For example, each grating 240 is as described in S. Savin, M. J. F. Digonnet, G. S. Kino, and H. J. Shaw, "Tunable mechanically induced long-period fiber gratings" Opt. Lett. 25, 710-712 (2000), the contents of which are hereby incorporated by reference. Accordingly, when pressed against a fibre, each grating 240 produces periodic pressure points in said fibre, which, by the photoelastic effect, results in a periodic modulation in refractive index along the fibre optic cable, thereby creating the LPFG. By varying the periodicity of the induced pressure points, for example by varying the period of grooves of said grating, a filtering wavelength of the LPFG is also variable. Accordingly, the gratings 240 are configured and / or operated to induce a LPFG tuned to filter a desired wavelength.

[0055] Specifically, to help with network diagnostics without interfering with service signals, the periodicity of each grating 240 is set specifically to filter-out the wavelength of the diagnostic signal from the OTDR (e.g. between 1600nm and 1650nm), whilst also being transparent to wavelengths at which service signals are transmitted and received by the OLTs 130.

[0056] As shown in Figure 4a, in the stowed position the first splice tray 180-1 rests upon the second splice tray 180-2. For vertically-stacked splice trays, the force of gravity may render the stowed position default, as gravity urges the splice trays 180 downwards upon one another.

[0057] In this stowed position, the first grating 240-1 is received within the second routing member 310- 2 and arranged (by suitably aligning, shaping, orientating and sizing the first grating 240-1 and the second routing member 310-2), to extend into the second routing member 310-2 so as to abut the second fibre 190-2 at the second splice 320-2

[0058] By oversizing (exaggerated in Figs 2 and 4 to aid understanding) the first grating 240-1 relative to a depth of the second adjacent routing member 310-2, less the gauge of the second splice 320-2, the first grating 240-1 contacts the second splice 320-2.

[0059] Furthermore, in this vertically-stacked and free-hanging arrangement, the entire weight of the first splice tray 180-1 bears down only upon the second splice 320-2, since the first grating 240-1 serves as the only contact point therebetween. In this way, the mass of the first splice tray 180-1 weighing down upon the second splice 320-2 acts as an urging member for forcing the first grating 240-1 upon the second splice 320-2, thereby creating a Mechanically-Induced Filter (MIF), and thus a corresponding filtering effect, in the second fibre 190-2.

[0060] As shown in Fig. 4b, in the unstowed position, the first splice tray 180-1 is lifted about the first hinge 230-1 and away and apart from the second splice tray 108-2, thereby also alleviating the second fibre 320-2 of the first grating 240-1 and temporarily eliminating the MIF from the second fibre 190-2 (until the first grating 240-1 is returned compressing the second fibre 320-2 in the stowed position). Figures 5a and 5b show exemplary schematic OTDR test results, in the form of OTDR traces 500, for OTDR tests performed by the OTDR for the second ONT 130-2 ( / .e. served by the second fibre 190-2). It should be noted that the OTDR traces 500 are simplified to illustrate only certain specific features, rather than fully characterising the network 100 as represented in Fig. 1 .

[0061] In both OTDR traces 500 there is observed gradual fibre loss 510 of the OTDR signal and, beyond range of the OTDR, a noise floor 520. A reflection and loss 530 indicative of a connector is also observed.

[0062] Figure 6, which is described with reference to Figs 5, shows an exemplary process 600 of operating the network 100 so as remotely to detect a state of the SN 120-2 for the betterment of performing interventions.

[0063] In a first step 610, a first OTDR trace 500-1 is retrieved from a first OTDR test performed whilst the first splice tray 180-1 is in the stowed position, and therefore whilst the first grating 240-1 induces the MIF upon the second fibre 190-2. Accordingly, in the first OTDR trace 500-1 there is observed a loss due to the MIF 540-1 at a distance 550 in the first OTDR trace 500-1 consistent with the location in the network 100 of the SN 120-2 (and, specifically, the second splice 320-2). The noise floor 520 commences at a first distance 560-1 . The first OTDR trace 500-1 is retrieved from the headend 110 OTDR or from another (e.g. portable) OTDR.

[0064] At a next step 620, as part of an intervention, the SN 120-2 is accessed e.g. for routine maintenance or new network deployments), and the first splice tray 180-1 is unstowed so as to access the second splice tray 180-2 and the second fibre 190-2; this action dispels the MIF from the second fibre 190-2.

[0065] In a next step 630, in response to the intervention (for example, as triggered by an engineer) a second trace from a second OTDR test performed whilst the first splice tray 180-1 is in the unstowed position (and therefore without the attenuating effect of the MIF upon the second fibre 190-2) is retrieved in a corresponding manner to the first OTDR trace 500-1 .

[0066] At a next step 640, the first 500-1 and the second OTDR traces are compared, and in particular as to whether the attenuating effect of the MIF upon the second fibre 190-2 has disappeared from the latter. In the event that there is no change in the second OTDR trace attributable to removal of the MIF (e.g. where the OTDR traces retrieved at steps 610 and 630 are both as per the first OTDR trace 500-1 of Fig. 5a), then it may be determined that the splice tray accessed by the engineer is not associated with the same fibre that is the subject of the first and second OTDR traces; this may be indicative of an error in identifying the correct fibre (physically, by the engineer, and / or as part of the OTDR tests). In this case, the correct SN, splice tray and / or fibre may be re-sought and the OTDR tests reconfigured and repeated, as per preceding steps of process 600.

[0067] Alternatively, after step 640, in the event that the second OTDR trace lacks the same attenuating effect of the MIF upon the second fibre 190-2 e.g. as per the second OTDR trace 500-2 of Fig. 5b, where loss due to the MIF is absent and the measured signal power at distance 550 is greater 540-2, to the extent of the attenuating effect of the MIF, than at the corresponding point 550 in the first OTDR trace 500-1 ), then this helps corroborate that the fibre that is the subject of the first and second OTDR traces and the fibre affected by the intervention are the same ( / .e. the second fibre 190-2), and therefore that the correct fibre has likely been targeted be the engineer and the OTDR tests, reassuring the engineer to continue with their intervention 660.

[0068] Because the signal power at distance 550 is greater 540-2 in this second OTDR trace 500-2 than at the corresponding point in the first trace 500-1 , the noise floor 520 in the second OTDR trace 500-2 commences at a second distance 560-2 that is greater ( / .e. further away from the OTDR) than the first distance 560-1 , thereby helping to probe further into the network 100.

[0069] After step 660, once the engineer has deemed the intervention complete (and providing that the second fibre 190-2 is intact), the engineer returns the SN 120-2 to its original (or default) state 670 by stowing the first splice tray 180-1 , and therefore again forcing the first grating 240-1 upon the second splice 320-2 and reintroducing the MIF to the second fibre 190-2.

[0070] Once the SN 120-2 has been returned to its original state 670, a third OTDR trace is retrieved from a third OTDR test performed e.g. triggered by the engineer or performed routinely) whilst the SN 120-2 is expected to be in the original state 680.

[0071] Next, the third OTDR trace is compared with the first OTDR trace so as to identify substantial differences in signal strength attributable to the absence of the MIF in the second fibre 690.

[0072] If the first 500-1 and third OTDR traces are substantially identical with respect to the attenuating effects of the MIF upon the second fibre 190-2 ( / .e. both comprising the loss due to the MIF 540- 1 ), then it is confirmed that the SN 120-2 has been correctly returned to the original state and that the network 100 has been made good following the intervention. Since the first grating 240-1 is specifically associated with the SN 120-2, first 180-1 and second 180-2 splice trays, and the second fibre 190-2, process 600 permits identification of the specific distribution node, splice tray and fibre left in an improper state.

[0073] If, however, the first 500-1 and third OTDR traces are not substantially identical with respect to the attenuating effects of the MIF upon the second fibre 190-2 (e.g. the third OTDR trace comprises the gain indicative of the absence of the MIF 540-2, as per the second OTDR trace 500-2 of Fig. 5b), then this may suggest that the SN 120-2, and in particular the first splice tray 180-1 and the second fibre 190-2, have been left in an incorrect state. For example, the first splice tray 180-1 may have been left unstowed and / or the second fibre 190-2 arranged outside of the second routing member 310-2. In this case, an alert is generated to notify an operator of the network 100 of this improper state of the SN 120-2, and process 600 re-iterates to step 670 by having an engineer re-attempt making the SN 120-2 good.

[0074] Alternatives and Modifications

[0075] The description above is provided in the context of engineer interventions. However, it will be appreciated that the SN 120-2 and process 600 are additionally or alternatively useful for generally detecting changes in the physical state of the SN 120-2, and specifically of the constituent splice trays 180 and fibres 190, including unauthorised access and / or damage due to vandalism, theft and / or environmental effects.

[0076] In part, the attenuating effect of a MIF is dependent upon the force with which the grating 240 compresses a fibre. This force can be adapted (increased or decreased) so as also to vary the attenuating effect, by, for example, changing: surface area of the gratings 240 ( / .e. all else being equal, a smaller surface area creating greater contact pressure, and therefore greater filtering); changing a length that the gratings 240 extend along the optical path of the fibres 190 ( / .e. all else being equal, greater longitudinal contact between grating and fibre creates a longer LPFG, and therefore greater filtering); changing mass of said component and / or providing a compression member, such as a weight, magnet, ratchet, spring, vice, clamp, strap and / or tie, to help force together the splice trays 180 ( / .e. all else being equal, a greater force causing greater filtering); and / or exploiting mechanical advantage (such as arranging the gratings 240 closer to the hinge 230 in the examples of Figs. 2 to 4 so as to increase compression, and therefore the filtering effect).

[0077] Furthermore, different fibres 190, and different splice trays 180, are distinguishable by detecting variations in the attenuating effects due to different MIFs from gratings that vary as to their characteristics and / or the force with which they are urged against fibres 190. For example, all else being equal, the extent of attenuation due to the MIF in the second fibre 190-2 is proportional to the weight of the first splice tray 180-1 bearing down upon the second splice 320-2 , whereas the extent of attenuation due to the MIF within the last splice 320-x routed within the last splice tray 180-x is proportional to the - greater - combined weight of all the other splice trays 180 bearing down upon the last splice 320-x, and observed in a corresponding OTDR trace as a deeper observed loss. Accordingly, differential attenuating effects may be used to uniquely identify fibres 190, and to pinpoint the component (e.g. a splice tray 180) that is subject to an intervention.

[0078] In one example, each grating 240 (whether within the same splice tray 180, otherwise, or provided elsewhere) has a different inherent characteristic so as to induce MIFs of differing characteristics e.g. attenuation extent and / or filter wavelength), for example by varying: grating period; grating length in contact with a given fibre optic cable; groove depth; and / or relative angles of said grating and said fibre). In this way, the distinct attenuating effect provided by the different gratings further helps improve pinpointing of specific fibres subject to an intervention, and to be responsive (and unresponsive) to different frequencies of diagnostic signals.

[0079] The principles described above in relation to inducing a MIF in the second fibre 190-2 by means of the first grating 240-1 are extendable to fibres 190 routed through others of the splice trays 180. However, in the example of Figs 2 to 4, since no splice tray 180 is provided above the first splice tray 180-1 , alternative means are available, additionally or alternatively, to induce a MIF within the first fibre 190-1 ; such alternative means are described below.

[0080] Fig. 7 shows an alternative exemplary form 700 of the first splice tray 180-1 , in which the first 240- 1 (or another) grating is arranged within the splice tray proximate to the first routing member 310- 1. In this example, the first routing member 310-1 comprises an aperture (not shown) through which the first grating 240-1 is available to extend to make contact with the first fibre 190-1 routed therewithin. The first grating 240-1 is coupled to a plate 710 that is in turn engaged to a tracked translation mechanism 720 that permits movement of the first grating 240-1 towards and away from the first fibre 190-1 . An urging mechanism, in the form of a spring 730, is coupled to a static end plate 740 and to the plate 710, and is configured to urge the plate 710, and therefore the first grating 240-1 , towards and into abutment against, the first fibre 190-1 . A planar base plate 750 is provided in opposition to the first grating 240-1 , and between which the first fibre 190-1 is arranged; in this way, the first grating 240-1 clamps the first fibre 190-1 against the base plate 750. As a result, the MIF is induced in the first fibre 190-1 , by the first grating 240-1 , when correctly routed through the first routing member 310-1. In this way, there is also provided a fastening mechanism for securing the fibre 190-1 within the routing member 310-1 . After an intervention in which the first fibre 190-1 is removed from the first routing member 310-1 , process 600 may be performed in order to confirm that the first fibre 190-1 has been correctly reinstalled within the first routing member 310-1 ( / .e. pinched between the first grating 240-1 and the base plate 750) by observing no substantial changes in the first 500-1 and third OTDR traces attributable to changes in the MIF (as per step 690 of process 600). The same configuration is available, alternatively or additionally, be applied to others of the splice trays 180.

[0081] In an alternative to the example 700 of Fig. 7, the first grating 240-1 is provided, additionally or alternatively, on the planar base plate 750 and exposed to the first fibre 190-1 , with the plate 710 compressing said fibre against the static grating on the planar base plate 750.

[0082] As a general principle, it will be appreciated that the first grating 240-1 is available to be arranged at various locations in the first splice tray 180-1 , so as to affect the first 190-1 , and / or other, fibre / s 190, and that the configurations disclosed herein are merely selected examples.

[0083] For example, with appropriate modification, the arrangement of Figs 1 to 4 is available to be reversed, so that the second grating 240-2 is provided (additionally or alternatively) on a top-side of the second splice tray 180-1 and exposed to the first fibre 190-1 (e.g. by providing an appropriate window in the first splice tray 180-1 ), thereby to induce the MIF within the first fibre 190-1.

[0084] Furthermore, the first (or any other) grating 240-1 is available to be arranged, instead of on the first splice tray 180-1 , in another actuatable component of the SN 120-1 , such as the lid 210-2 (or a door) of the enclosure 210, whereby the act of closing the lid 210-2 (or door) translates the first grating 240-1 into abutment with the first (or any other) fibre 190-1 , and a corresponding urging member (a spring and / or weight of the lid 210-2 itself) compresses the grating 240-1 upon the first fibre 190-1.

[0085] In an alternative, by routing multiple fibres 190 within the same routing member 320, the same grating 240 is available simultaneously to induce a MIF within said multiple fibres 190.

[0086] Alternatively or additionally, a set of at least two gratings 240 are provided within the same splice tray 180 so as to affect a plurality of fibres 190 routed within a given single splice tray 180 (whether within the same or different routing members 320).

[0087] Additionally or alternatively, said set of gratings 240, or a subset of at least two gratings, are arranged to affect the same one, or many different, fibres 190. That is, there is available to be a one-to-one, one-to-many, or a many-to-many contact between the set of gratings 240 and the fibres 190.

[0088] In an alternative, and in particular where the weight of the splice trays 180 is inadequate solely to serve as the urging member for forcing the grating 240 onto the fibres 190 with sufficient force so as to induce a MIF therewithin (e.g. where the splice trays are too light and / or where splice trays 180 are arranged horizontally), then the compression member is additionally provided.

[0089] It will be appreciated that the structure of the SN 120-2 described above is equally applicable to other forms of distribution nodes e.g. the CBT 120-3 or CSPs 120-4), in addition, or alternatively, to the SN (with appropriate changes to the translation mechanism and urging members, for example where no splice tray 180 is provided) so as to detect the state of the distribution nodes. In an alternative, at least one of the distribution nodes is in the form of a “Fibre Management Unit” (FMU), “Optical Distribution Box” (ODB), fibre splice rack, Fibre Distribution Panel (FDP), and / or Fibre Distribution Centre (FDC).

[0090] In one embodiment, the system and / or its components or subsystems can include computing devices, microprocessors, modules and other computer or computing devices, which can be any programmable device that accepts digital data as input, is configured to process the input according to instructions or algorithms, and provides results as outputs. In one embodiment, computing and other such devices discussed herein can be, comprise, contain or be coupled to a Central Processing Unit (CPU) configured to carry out the instructions of a computer program. Computing and other such devices discussed herein are therefore configured to perform basic arithmetical, logical, and input / output operations.

[0091] Various embodiments of systems, devices, and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the claimed inventions. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, configurations and locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the claimed inventions.

[0092] Persons of ordinary skill in the relevant arts will recognise that embodiments may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, embodiments can comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art. Moreover, elements described with respect to one embodiment can be implemented in other embodiments even when not described in such embodiments unless otherwise noted. Although a dependent claim may refer in the claims to a specific combination with one or more other claims, other embodiments can also include a combination of the dependent claim with the subject matter of each other dependent claim or a combination of one or more features with other dependent or independent claims. Such combinations are proposed herein unless it is stated that a specific combination is not intended. Furthermore, it is intended also to include features of a claim in any other independent claim even if this claim is not directly made dependent to the independent claim.

[0093] Moreover, reference in the specification to “one embodiment,” “an embodiment,” or “some embodiments” means that a particular feature, structure, or characteristic, described in connection with the embodiment, is included in at least one embodiment of the teaching. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.

[0094] Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein. Any incorporation by reference of documents above is further limited such that no claims included in the documents are incorporated by reference herein. Any incorporation by reference of documents above is yet further limited such that any definitions provided in the documents are not incorporated by reference herein unless expressly included herein.

[0095] Each feature disclosed herein, and (where appropriate) as part of the claims and drawings may be provided independently or in any appropriate combination.

[0096] Any reference numerals appearing in the claims are for illustration only and shall not limit the scope of the claims.

Claims

Claims1 . An enclosure for routing a fibre optic cable for a telecommunications network, the enclosure comprising a / an: routing member for receiving and routing a fibre optic cable within the enclosure; securing structure for securing the fibre optic cable within the routing member; grating for generating a Mechanically Induced Filter, MIF, in the fibre optic cable; urging member configured to urge the grating against the fibre optic cable thereby to generate the MIF within said fibre optic cable; translation mechanism configured to translate the urging member and the securing structure between: a first arrangement, in which the grating is urged against the fibre optic cable when said fibre optic cable is routed in the routing member, and in which the securing structure secures the fibre optic cable; and a second arrangement, in which the grating is not urged against the fibre optic cable when said fibre optic cable is routed in the routing member, the MIF thereby being absent from the fibre optic cable, and the fibre optic cable is unsecured by the securing structure.

2. An enclosure according to Claim 1 , wherein the translation mechanism is further configured to translate the grating between the: first arrangement, in which the grating abuts the fibre optic cable; second arrangement, in which the grating is arranged apart from the fibre optic cable.

3. An enclosure according to Claim 1 or 2, wherein the securing structure comprises a cover, shield, door and / or lid for preventing or impeding access to the fibre optic cable when in the first arrangement.

4. An enclosure according to any preceding claim, wherein the enclosure comprises a splice tray.

5. An enclosure according to Claim 4, wherein the splice tray comprises the routing member.

6. An enclosure according to Claim 4 or 5, wherein the splice tray comprises the translation mechanism and / or the urging member.

7. An enclosure according to any of Claims 4 to 6, wherein the splice tray comprises the grating.

8. An enclosure according to any of Claims 4 to 7, wherein the enclosure comprises a further splice tray.

9. An enclosure according to Claim 8, wherein the further splice tray comprises the, or another of the, grating.

10. An enclosure according to Claim 8 or 9, wherein the further splice tray comprises the, or another of the, translation mechanism and / or urging member.

11. An enclosure according to any of Claims 4 to 10, wherein, in the first arrangement, the securing structure is stacked upon the splice tray, or vice versa.

12. An enclosure according to any preceding claim, comprising a plurality of the routing members and / or a plurality of the gratings, wherein each routing member is configured to receive and to route at least one fibre optic cable, and wherein, in the first arrangement, each of the gratings is urged against a different one of said fibre optic cables or the same fibre optic cable / s, thereby to generate the MIF therewithin.

13. A fibre optic telecommunications network comprising at least one enclosure according to any preceding claim.

14. A method of operating a fibre optic telecommunications network, said network comprising: an enclosure for routing a fibre optic cable for the telecommunications network, the enclosure comprising a / an: routing member for receiving and routing a fibre optic cable within the enclosure; securing structure for securing the fibre optic cable within the routing member; grating for generating a Mechanically Induced Filter, MIF, in the fibre optic cable; urging member configured to urge the grating against the fibre optic cable thereby to generate the MIF within said fibre optic cable; translation mechanism configured to translate the urging member and the securing structure between: a first arrangement, in which the grating is urged against the fibre optic cable when said fibre optic cable is routed in the routing member, and in which the securing structure secures the fibre optic cable; and a second arrangement, in which the grating is not urged against the fibre optic cable when said fibre optic cable is routed in the routing member, the MIF therebybeing absent from the fibre optic cable, and the fibre optic cable is unsecured by the securing structure; wherein the method comprises the steps of: retrieving a: first test result from a first optical reflectometry test performed upon the fibre optic cable whilst the enclosure is in the first arrangement, thereby to detect a filtering effect of the Ml F; and second test result from a second optical reflectometry test performed upon the fibre optic cable whilst the enclosure is in the second arrangement; comparing the first and second test results; identifying, from said comparing, an absence of the filtering effect of the MIF in the second test result; and in response to said identifying, generating an alert that the enclosure is in the second arrangement.

15. A computer-readable carrier medium comprising a computer program, which, when the computer program is executed by a computer, causes the computer to carry out the steps of Claim 14.

Images