EP4659384A1 - Procédé et système de test d'un réseau de fibre optique - Google Patents

Procédé et système de test d'un réseau de fibre optique

Info

Publication number
EP4659384A1
EP4659384A1 EP23821684.0A EP23821684A EP4659384A1 EP 4659384 A1 EP4659384 A1 EP 4659384A1 EP 23821684 A EP23821684 A EP 23821684A EP 4659384 A1 EP4659384 A1 EP 4659384A1
Authority
EP
European Patent Office
Prior art keywords
fibre optic
mif
rogue
optic cable
upstream
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP23821684.0A
Other languages
German (de)
English (en)
Inventor
Ian HORSLEY
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
British Telecommunications PLC
Original Assignee
British Telecommunications PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by British Telecommunications PLC filed Critical British Telecommunications PLC
Publication of EP4659384A1 publication Critical patent/EP4659384A1/fr
Pending legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/071—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using a reflected signal, e.g. using optical time domain reflectometers [OTDR]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/27—Arrangements for networking
    • H04B10/272—Star-type networks or tree-type networks

Definitions

  • the present invention relates to method of testing a fibre optic network, and in particular by using a Mechanically Induced Filter to affect transmissivity through the fibre optic network.
  • An Optical Time Domain Reflectometer 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.
  • an OTDR trace is manually interpreted by trained engineers who tag identified features.
  • an OTDR trace may contain a large number of reflections (often, at least thirty), and manual analysis can therefore be time-consuming.
  • co-located features especially downstream of splitters in a Passive Optical Network
  • an Optical Line Terminal used to transmit and receive service signals, can also be used to detect the operating status of transmitting components of the fibre optic network, and in particular to detect the presence of a rogue transmitting component.
  • OLTs and the architecture of large-scale fibre optic networks, are not suitable for identifying and pinpointing a specific transmitting component.
  • a method of testing a fibre optic network so as to identify a rogue transmitter in said network by using a Mechanically Induced Filter, MIF, comprising a grating comprising the steps of: sensing, at a receiver provided as part of the fibre optic network, an upstream rogue transmission from a rogue transmitter; using the MIF to force the grating upon a fibre optic cable of the fibre optic network, wherein said MIF is configured to cause a filtering effect upon the upstream rogue transmission; monitoring, at the receiver, for the upstream rogue transmission; and in response to detecting, by said monitoring, the upstream rogue transmission with the filtering effect, determining that the rogue transmitter is connected and transmitting via (optionally, specifically) the fibre optic cable.
  • MIF Mechanically Induced Filter
  • the term “rogue”, as used in relation to the “transmitter” and “transmission”, preferably connotes unscheduled, improperly functioning, unexpected operation (from a network provider’s perspective) or otherwise unintended operation.
  • the “rogue transmission” preferably connotes a continuous single transmission or a plurality of sequential transmissions, which may be unchanging or may be variable as to type, duration, wavelength and/or intensity.
  • upstream preferably connotes towards: the receiver; a headend of the fibre optic network; away from the rogue transmitter; and/or away from a termination point of the fibre optic network for an end user.
  • the rogue transmitter is an Optical Network Terminal or and an Optical Network Unit.
  • detecting the upstream rogue transmission with the filtering effect preferably connotes determining or observing the upstream rogue transmission being affected (optionally, reduced or attenuated) by the filtering effect in an expected manner that is consistent with the MIF.
  • the filtering effect is a complete (e.g. in an absolute sense or beyond a detection threshold of the receiver) or partial filtering of the rogue transmission. Where the filtering effect is (effectively) complete (or, optionally, absolute or total), detecting, by said monitoring, the upstream rogue transmission with the filtering effect may comprise detecting an absence of the rogue transmission.
  • the filtering effect may be an expected attenuation as a result of the MIF, which may connote a reduction in intensity of a reflected signal, in which said reduction is attributable to the use of the MIF based on an estimated or known location and/or filtering effect of the MIF (for example, transmissivity, which may be known at a given wavelength).
  • the step/s of detecting and/or monitoring is/are performed by the optical reflectometry measuring device and/or by a processor (in any combination), remote from the optical reflectometry measuring device.
  • the method further comprises the step of, in response to detecting, by said monitoring, the upstream rogue transmission without the filtering effect, determining that the rogue transmitter is not connected and not transmitting via the fibre optic cable.
  • the method further comprises the subsequent steps of: identifying an alternative fibre optic cable to the fibre optic cable; using the, or another, MIF to force the grating upon the alternative fibre optic cable, wherein said MIF is configured to cause the filtering effect upon the rogue transmission; subsequently monitoring, at the receiver, for the upstream rogue transmission; and in response to detecting, by said subsequent monitoring, the upstream rogue transmission with the filtering effect, determining that the rogue transmitter is connected and transmitting via the alternative fibre optic cable.
  • the alternative fibre optic cable is unconnected to the fibre optic cable to the extent that upstream transmissions are unexchangeable directly between said fibre optic cables.
  • the rogue transmitter in response to determining that the rogue transmitter is connected and transmitting via the, or the alternative, fibre optic cable, leaving the MIF, or the another, as appropriate, in situ forced upon said corresponding fibre optic cable so as to continue to cause the filtering effect upon the rogue upstream transmission.
  • the method further comprises the step of identifying a characteristic of the upstream rogue transmission, and configuring the MIF in dependence upon said characteristic so as to cause the filtering effect.
  • the characteristic is wavelength and/or intensity.
  • the MIF is configured to cause the filtering effect upon the rogue transmission by tuning the grating (at least by selection of the appropriate periodicity of the grating), relative to the wavelength.
  • the MIF is configured to cause the filtering effect at wavelengths less than 1625nm and/or more than 1700nm, and more preferably between 1300nm and 1550nm.
  • the upstream rogue upstream transmission is a (rogue) service signal.
  • the sensing is performed without using the MIF to force the grating upon the fibre optic cable.
  • the sensing may be performed whilst using the MIF to force the grating upon the fibre optic cable so as to achieve a lesser filtering effect.
  • the filtering effect may be achieved by: changing an angle of the grating upon the fibre optic cable; changing a force with which the MIF is forced upon the fibre optic cable; and/or changing a length of the grating, for example by forcing another grating upon the fibre optic cable.
  • the MIF is configured to induce a Long-Period Fiber Grating, LPFG, or a Fibre Bragg Grating, FGB, when compressing the grating upon the fibre optic cable.
  • the fibre optic cable directly connects only a subset of transmitters of the fibre optic network, wherein each of said transmitters is suitable for transmitting upstream transmissions.
  • the alternative fibre optic cable directly connects only an alternative subset of transmitters.
  • the fibre optic cable directly connects only a single transmitter of the fibre optic cable, wherein said transmitter is suitable for transmitting upstream transmissions.
  • the alternative fibre optic cable uniquely connects an alternative transmitter of the fibre optic cable that is also suitable for transmitting upstream transmissions.
  • the fibre optic cable and/or the alternative fibre optic cable is/are downstream of a splitter or a router, and may directly stem from said splitter or router.
  • the grating is directly urged upon a jacket or a cladding of the fibre optic cable.
  • MIF is urged upon the alternative fibre optic cable in a corresponding manner.
  • the outer jacket of the fibre is removed so as to permit direct compression of the cladding.
  • the MIF directly compresses the fibre optic cable proximate a joint, aggregation node or splitter node.
  • the MIF remains outside of a path of light transmissions through the fibre optic cable; that is, the MIF is not an in-line filter.
  • the MIF remains optically uncoupled from the fibre optic cable.
  • the sensing, detecting and/or monitoring is performed using an Optical Time-Domain Reflectometer, OTDR, and/or an Optical Line Terminal for transmitting and receiving a telecommunications service signal through the fibre optic network.
  • the OTDR and/or OLT are located at a most-upstream point of the fibre optic network.
  • the MIF is remotely operated (optionally, by means of robotics and/or actuators) so as to be urged against the fibre optic cable, thereby to cause the first and/or second extents of filtering.
  • using the MIF so as to cause the first and/or second extents of filtering subsequently triggers the first and/or second test/s, respectively.
  • 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 any one of the methods described above.
  • a system for identifying a rogue transmitter, causing an upstream rogue transmission, in a fibre optic network comprising a: Mechanically Induced Filter, MIF, comprising a grating configured to be forced upon a fibre optic cable of the fibre optic network, wherein said MIF is configured to cause a filtering effect upon the upstream rogue transmission; detector, provided as part of a receiver of the fibre optic network, for detecting an upstream rogue transmission from a rogue transmitter and for monitoring; and a processor configured to, in response to detecting by said detector, the upstream rogue transmission with the filtering effect, determine that the rogue transmitter is connected and transmitting via the fibre optic cable.
  • the MIF is configured to cause the filtering effect
  • the MIF comprises a first plate and an opposing second plate, wherein the first or second plate is flat.
  • the first plate and the second plate are rotatable relative to one another.
  • the first plate and second plate are dimensioned so as to receive and clamp the cladding and/or outer jacket of the fibre optic cable.
  • the second plate comprises a grating.
  • said grating is identical to the grating of the first plate.
  • said grating is arranged to intermesh with the grating of the first plate or are otherwise aligned with one another.
  • the grating is a notched grating.
  • the MIF is in the form of a hand tool comprising pivoted arms, the grating being arranged on one such arm, and an opposing abutment plate being provided on another of the arms, wherein the MIF is pivoted so as to compress the fibre cable between the grating and the opposing abutment plate.
  • the MIF comprises a spring tensioner for the arms.
  • the grating and the abutment plate are flat.
  • the grating is removable, and may be interchangeable.
  • the MIF comprises a clamp for urging the arms together.
  • the filtering effect of the MIF is controllable, known, reversible, non-destructive, and/or repeatable.
  • the fibre optic network is a point-to-multipoint network and/or a Passive Optical Network.
  • the fibre optic network comprises at least two branches (optionally, formed by a splitter), and wherein the fibre optic cable forms one of said branches, and to which the rogue transmitter is connected; in this way, determining that the rogue transmitter is connected and transmitting via the fibre optic cable may help identify which of said branches the rogue transmitter is connected (/.e. the branch served by the fibre optic cable).
  • the fibre optic cable is a single core fibre optic cable.
  • the filtering effect is a relative peak signal strength (e.g.
  • 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.
  • Any apparatus feature may also be provided as a corresponding step of a method, and vice versa.
  • means plus function features may alternatively be expressed in terms of their corresponding structure, for example as a suitably-programmed processor.
  • 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.
  • FIG. 1 shows the MIF in detail
  • FIG. 3 shows the fibre optic telecommunications network with the Mechanically-Induced Filter (MIF) in use
  • Figure 4 is a process for using the MIF to identify a fibre optic cable of the fibre optic telecommunications network
  • Figure 5 is a process for using the MIF to locate a fault in the fibre optic telecommunications network
  • Figures 6a, 6b and 6c show schematic diagnostic test results for diagnostic tests performed as part of the aforementioned process for using the MIF to locate a fault; and Figure 7 is a process for using the MIF to identify a rogue component in the fibre optic telecommunications network.
  • Figure 1 is a schematic diagram of a fibre optic telecommunications network 100, such as for providing wide-area fixed-access broadband network services.
  • the network 100 comprises a/an: Optical Line Terminal (OLT) 110; Optical Time Domain Reflectometer (OTDR) 120; switch 130; WDM splitter 140; power splitter 150; and a plurality of Optical Network Units (ONUs) 160, including a first 160-1 , second 160-2, third 160-3 and fourth 160-4 ONU.
  • the aforementioned components are interconnected using optical links provided using, at least, fibre optic cables (represented as arrowed lines) so as to provide telecommunications services between, at least, the OLT 110 and each of the ONUs 160, and diagnostic test services between, at least, the OTDR 120 and the same ONUs 160.
  • the OLT 1 10 is located at the head-end of the network 100, for example where a local exchange is sited, and is connected to the plurality of ONUs 160 via the WDM splitter 140 and the power splitter 150 (in which the former is located upstream of - that is, sequentially closer than - the latter).
  • Each ONU is connected to the power splitter 150 via a dedicated corresponding distribution fibre optic cable 170; that is, a first optic cable 170-1 for ONU 160-1 , a second fibre optic cable 170-2 for ONU 160-2, a third fibre optic cable 170-3 for ONU 160-3, and a fourth fibre optic cable 170-4 for ONU 160-4.
  • the OLT 1 10 and the OTDR 120 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).
  • a higher-layer network management software application comprising an Element Management System (not shown) and/or a Network Management System (not shown).
  • a user or the network 100 may trigger a diagnostic test to be performed by the OTDR 120.
  • the OTDR 120 is an optical reflectometry measuring device for the network 100.
  • the OTDR 120 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 120 is operated by sending a diagnostics signal down the network 100, this results in backscattering and reflections due to the presence of discontinuities in the fibre structure.
  • 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, whereas a small reflection may indicate a connector with an air gap.
  • the OTDR 120 is a standalone device separate to the OLT 110, and the OTDR connects to the plurality of ONUs 160 using, at least, the same portion of the network as the OLT (i.e. via the WDM splitter 140 and power splitter 150).
  • an exemplary schematic first OTDR test result 180-1 in the form of an OTDR trace, for a first OTDR test performed by the OTDR 120 between the OLT 1 10 and the first ONU 160-1 , is shown in Figure 1.
  • the OTDR test result 180-1 shows a series of significant (i.e. above a noise floor 195) reflections 185 from Rayleigh backscatter and reflections 187 from relatively high reflective features (e.g. ONUs, connections, etc.) of the fibre optic network.
  • the reflections 187 exemplarily comprise a first 187-1 , second 187-2, third 187-3 and fourth 187-4 peak.
  • the network 100 is manipulated using a Mechanically-Induced Filter (MIF) 200, and changes as a result of the MIF are measured, for example using the OTDR, and processed so as to test characteristics of the network 100.
  • MIF Mechanically-Induced Filter
  • FIG. 2 is a detailed schematic representation of the Mechanically-Induced Filter (MIF) 200 for use in the network 100.
  • MIF Mechanically-Induced Filter
  • the MIF 200 comprises a/an: grating 210; primary plate 220; opposing plate 230; first arm 240- 1 ; second arm 240-2; hinge 250; and spring 260.
  • the grating 210 is a mechanical grating formed of periodic grooves arranged so as to, when forced upon the fibre optic cable 170-1 , mechanically induce a loss filter in the form of a Long Period Fibre Grating (LPFG) within the fibre optic cable.
  • LPFG Long Period Fibre Grating
  • the grating 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 (herein "Savin et a!') are hereby incorporated by reference.
  • the grating 210 When pressed against a fibre optic cable, the grating 210 produces periodic pressure points in the fibre optic cable, which, by the photoelastic effect, results in a periodic modulation in refractive index along the fibre optic cable 170-1 , thereby creating the LPFG.
  • a filtering wavelength of the LPFG is also variable. Accordingly, the grating is configured and/or operated to induce an LPFG tuned to filter a desired wavelength.
  • the periodicity of the grating 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 OLT.
  • the periodicity of the grating is set to filter out wavelengths associated with upstream signals from the ONUs 160 (e.g. between 1400nm and 1600nm).
  • the grating 210 is arranged on the primary plate 220 and is exposed.
  • the primary plate 220 is in turn arranged at a terminal end of the first arm 240-1 , which is coupled via a hinge 250 to the second arm 240-2 so as to form a handheld hinged tool, and specifically a clamp, tongs, peg or tweezers.
  • the second arm 240-2 comprises an opposing plate 230 for abutting against the grating 210 when the first and second arms are actuated together.
  • the primary plate 220 and the opposing plate 230 are arranged so that, when apart, the fibre optic cable 170-1 is receivable therebetween, and, when actuated together, the fibre optic cable is compressed by the grating 210 and between the primary plate 220 and the opposing plate 230.
  • the spring 260 interconnects the first and second arms so as to urge said arms together, thereby to provide a clamping action.
  • a jacket or cladding of the fibre optic cable 170-1 , or the optical fibre itself, is available to be received and compressed using the MIF 200.
  • a loss filter can be induced in the fibre optic network, without having to disassemble and then connect such a filter in-line, thereby improving flexibility, ease and continuity of service.
  • the MIF is available to be applied to a fibre optic cable associated with a distribution network, joint, aggregation node, splitter node, ONU and/or switch.
  • FIG. 3 shows, schematically, the MIF 200 being used with the network 100, and the filtering effects achieved therefrom.
  • the MIF is used to clamp the fibre optic cable 170-1 at a point downstream of the power splitter 150 and upstream of the first ONU 160-1 .
  • Figure 3 includes an exemplary schematic second OTDR test result 180-2 from a second OTDR test performed by the OTDR 120 towards the first ONU 160-1 and whilst the MIF 200 is used to clamp the first fibre optic cable 170-1 so as to achieve a filtering effect.
  • the second OTDR test result 180-2 also shows a series of significant (/.e. above a noise floor 195) reflections 185 from Rayleigh backscatter and reflections 187 from (corresponding) relatively high reflective features. Beyond a certain distance along the first fibre optic cable 170-1 , the peak 187-2 attenuates, and in this example (of high filtering by the MIF 200), collapses to the noise floor 195.
  • the peak 187-2 does not therefore appear; this is consistent with expectations given that the MIF 200 is located downstream of the power splitter 150 and upstream of the ONUs 160, and given also the expected filtering effect of the MIF (i.e. configured to achieve very high filtering at the wavelength of the second OTDR test).
  • the attenuation of the second peak 187-2 is attributable to the effects of the MIF 200. Since the MIF is physically located upstream of the first ONU 160-1 , the peak 187-2 is therefore attributable to the fibre optic cable 170-1 and the first ONU 160-1. Accordingly, it can be concluded that the MIF is clamped to the fibre optic cable 170-1 , that the peak 187-2 is associated with the fibre optic cable 170-1 , and in turn with the first ONU 160-1.
  • the exact location of the MIF along the fibre optic cable 170-1 can also be determined, where additions of MIF imprints an expected attenuation upon the second OTDR test result 180-2 compared to the first OTDR test result 180-1 .
  • the location of the MIF is available to be marked (or “tagged”) in the OTDR test results 180. In this way, the physical location of the MIF and the location of the MIF in the OTDR test results 180 (as determined by its detected filtering effect) may be reconciled.
  • Figure 4 shows an exemplary process 400 for using the MIF 200 to help identify the fibre optic cable 170-1 , and specifically to help reconcile a physical fibre optic cable with a fibre optic cable through which a diagnostic test is performed.
  • the first OTDR test result 180-1 is retrieved by a computing device (e.g. the OTDR 120, the Element Management System, or a remote computer or mobile device) from a first OTDR test performed by the OTDR 120 without using the MIF 200.
  • the second test result 180-2 is retrieved by the computing device, from a second OTDR test performed by the OTDR 120 whilst the MIF is used to compress the fibre optic cable 170-1.
  • the first and second OTDR tests are performed using the same wavelength, and the MIF is configured to filter ⁇ e.g. maximally) at said wavelength, e.g. 1650nm.
  • the first and second OTDR test results 180 are compared so as to perform a subsequent determination 440 as to whether there is an expected attenuation, attributable to the MIF, in the second OTDR test result 180-2 compared to the first OTDR test result 180-1.
  • the comparison comprises performing signal difference analysis to identify an expected attenuation that corresponds with the estimated, or known, location of the MIF 200 ⁇ e.g. upstream of the ONU 160-1 , and downstream of the splitter 150) and/or the filtering effect of the MIF e.g. 90% attenuation at 1650nm).
  • the fibre optic cable 170-1 onto which the MIF was applied at step 410 forms a part of the route through which the first and second OTDR tests were performed, and it is determined that the physical location of the MIF 200 corresponds to the second threshold point 190-2, which is marked 470, in association with the MIF, on the first and second OTDR test results 180, and for future corresponding OTDR tests to help map the fibre optic network.
  • FIG. 5 shows a further process 500, extending from the principles described above, for assisting with physically locating a fault in the network 100 by using the MIF 200 and OTDR testing.
  • Process 500 is described with reference to Figures 6a, 6b and 6c, each of which schematically show OTDR test results 600.
  • a diagnostic OTDR test is performed through a path that includes the first fibre optic cable 170-1 between the WDM splitter 140 and the power splitter 150, without the MIF 200, yielding a diagnostic OTDR test result 600-1 , as shown in Figure 6a, from which there is identified a fault result 610 (represented as a reflection and a small attenuation) that is indicative of a fault along the fibre optic network ⁇ e.g. a faulty connection, a severe bend and/or a broken component).
  • the diagnostic OTDR test is available to correspond with the first OTDR test as per step 410 of process 400.
  • the location of the fault result 610 in the diagnostic OTDR test result 600-1 is used to estimate (although, as noted above, typically with some error) the corresponding physical location of the fault in the fibre optic network 100.
  • the MIF 200 is then applied to the fibre optic cable between the WDM splitter 140 and the power splitter 150 (identifiable, for example, using process 400).
  • a subsequent OTDR test, configured as per the diagnostic OTDR test in step 520, is then performed whilst compressing the first fibre optic cable 170-1 with the MIF, thereby yielding a subsequent OTDR test result.
  • the second OTDR test is available to correspond with the second OTDR test as per step 420 of process 400.
  • the diagnostic and subsequent OTDR test results are compared so as to determine whether the fault result 610 persists (to an extent changed by the filtering effect of the MIF) in the subsequent OTDR test result.
  • Figure 6b shows a subsequent OTDR test result 600-2, in which the fault result 610 is still present and unchanged, and in which the MIF is applied at a location 620 downstream of the fault.
  • the subsequent OTDR test was performed with the MIF 200 located upstream of the fault 550; that is, the fault lies beyond (or away from) both the MIF 200 and the OTDR 120, and that the fault cannot be any more upstream from the MIF, thereby setting a ‘lower’ limit to the location of the fault.
  • Figure 6c shows an alternative subsequent OTDR test result 600-3, in which the fault result is no longer present since the MIF is applied at a location 630 upstream of the fault (and location 620), which therefore prevents the corresponding diagnostics signal from reaching the fault and then producing the fault result.
  • steps 540 and 550 are available to re-iterate to step 520, such that the estimated location of the fault is revised using the range of possible locations (and by estimating distance using time-of-flight information from the OTDR tests) of the fault as constrained by the previously-determined ‘upper’ and/or ‘lower’ limits.
  • the Ml F 200 is applied at a revised estimated location (/.e. more upstream if step 540 immediately preceded, or more downstream if step 550 immediately preceded), and a further subsequent OTDR test is performed afresh.
  • steps 520, 530, 540 and 550 may be re-iterated until the location of the fault is sufficiently constrained. Accordingly, iterative use and adjustment of the MIF, along with OTDR testing, is used to narrow-down, and eventually locate, the fault. For example, using both subsequent OTDR test results 600-2 and 600-3, it is deducible that the fault resides between the physical locations where the MIF was applied when performing each corresponding OTDR test.
  • the physical location of the fault 610 is identifiable using conventional ranging based on the OTDR test result, since the error in this distance will have a low absolute value.
  • Figure 7 shows a process 700 for identifying a rogue (or a continuous-mode) ONU by using the MIF.
  • a rogue ONU transmits unscheduled (from the perspective of the network operator) signals, which may be due to the rogue ONU being faulty or operating in an unauthorised manner.
  • a first step 710 the presence - but not identity - of a rogue ONU within the network 100 is identified; this is performed using techniques known in the art, such as by detecting at the OLT 110 unscheduled upstream optical signals from an ONU. In this example, with reference to Figure 1 , it is identified that - an as-yet unknown - one of the plurality of ONUs 160 is a rogue ONU.
  • the MIF 200 is applied to a dedicated fibre optic cable that directly and solely connects a given one of the plurality of ONUs 160 to the splitter 150.
  • the MIF is applied to the first fibre optic cable 170-1 (/.e. uniquely connecting the first ONU 160-1 ), thereby to induce a filtering effect upon transmissions through said fibre optic cable.
  • the MIF is tuned (by selecting the appropriate grating periodicity) to significantly attenuate a wavelength of upstream transmissions from ONUs (e.g. between 1300nm and 1550nm), for example as detected by the OLT.
  • step 730 at the OLT 1 10, detection of the effects of the rogue ONU are reassessed whilst the MIF remains applied to the selected fibre optic cable, for example using the same technique used to detect the presence of a rogue ONU as used at step 710.
  • step 730 if, as per eventuality 740, it is determined that the effects of the rogue ONU persist whilst the MIF remains applied to the selected fibre optic cable 170-1 , and that the detected effects of the rogue ONU are not attenuated in a manner and/or to an extent expected of the filtering effects of the MIF (e.g. complete attenuation), then it is concluded that the ONU uniquely associated with fibre optic cable to which the MIF was applied in preceding step 720 is not the rogue ONU, and is marked as such and as having already been tested.
  • process 700 re-iterates to step 720, at which point the MIF is subsequently applied to a dedicated fibre optic cable, different to that to which the MIF was applied at any preceding step 720, that directly and solely connects another one of the plurality of ONUs 160 to the splitter 150.
  • the MIF is applied to the second fibre optic cable 170-2 (/.e. uniquely connecting the second ONU 160-2), thereby to induce a filtering effect upon transmissions through said fibre optic cable.
  • step 750 if it is determined that the effects of the rogue ONU no longer persist whilst the MIF remains applied to the fibre optic cable selected in immediately preceding step 720, for example by attenuating in a manner and/or to an extent expected of the filtering effects of the MIF, then it is concluded that the ONU uniquely associated with this fibre optic cable is the rogue ONU. Remedial action may subsequently be taken, including repairing or disconnecting the identified rogue ONU, and/or leaving the MIF applied to the fibre optic cable associated with the identified rogue ONU, thereby to filter out the effects of the rogue ONU.
  • step 420 precedes step 410, such that an OTDR test with the use of the MIF is performed before a corresponding test without the MIF.
  • the MIF 200 is used merely to induce a detectable relative - rather than absolute - change in transmissivity. Accordingly, whilst greater filtering effects of the MIF are desirable, the MIF is configured to cause any detectable extent of filtering.
  • the MIF 200 and/or the OTDR 120 is available to be operated in ways so as to change the filtering effect so as to allow for relative comparison.
  • the extent of the filtering effect of the MIF is dependent upon the:
  • the MIF is available to remain continuously clamped to a fibre optic cable, and a wavelength of the optical test signal is available instead to be varied across each OTDR test.
  • a first wavelength is selected that achieves low filtering
  • another optical test signal e.g. the second
  • a second wavelength is selected that achieves a relatively higher degree of filtering.
  • the same principle can be extended to processes 500 and 700.
  • the MIF 200 can remain in situ clamped to the fibre optic cable, with force, angle, length or wavelength varied so as to render the MIF transparent or opaque.
  • service signals can effectively continue to be communicated whilst the MIF remains in situ but tuned to be transparent to the wavelength of the service signals.
  • a new MIF can be added to the fibre optic network at step 520.
  • the MIF and the new MIF are configured to achieve different extents of filtering at different wavelengths, as described above, across multiple iterations of step 530, the subsequent OTDR tests can be performed by selectively using different wavelengths based on the wavelength to which each MIF is specifically tuned to filter. For example, after step 550, a wavelength to which a more upstream MIF is transparent, but to which a more downstream MIF is opaque, is used at subsequent step 520, thereby to prevent filtering by the upstream MIF, which would otherwise conceal the fault and the more downstream MIF.
  • process 500 is primarily described with reference to identifying a fault, it will be appreciated that process 500 can be extended to locating any feature of the fibre optic network that is detectable by an optical reflectometry measuring device , such as an arbitrary selected location, component or joint, whether impaired or fully functioning.
  • process 700 is performed individually to eliminate ONUs as the rogue ONU.
  • process 700 may be adapted such that the MIF is applied to a fibre optic cable connecting a plurality - but not all of the plurality - of ONUs 160 (/.e. a subset), thereby to eliminate multiple ONUs at a time, including at a point upstream of the splitter 120, where multiple such splitters are provided within the network 100.
  • MIF 200 shown in, and described with reference to, Fig. 2 is merely exemplary and that other forms of MIFs are available to be used that need only mechanically- induce a loss filter in a fibre optic cable.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Computing Systems (AREA)
  • Optical Communication System (AREA)

Abstract

L'invention concerne un procédé (700) permettant de tester un réseau de fibre optique (100) de façon à identifier un émetteur indésirable dans ledit réseau à l'aide d'un filtre induit mécaniquement MIF (200) comprenant une grille (210), ledit procédé comprenant les étapes consistant à : détecter, au niveau d'un récepteur (110) faisant partie du réseau de fibre optique, une transmission indésirable en amont provenant d'un émetteur indésirable (710) ; utiliser le MIF pour forcer la grille sur un câble à fibre optique (170-1) du réseau à fibre optique, ledit MIF étant configuré pour provoquer un effet de filtrage sur la transmission indésirable en amont (720) ; surveiller, au niveau du récepteur, la transmission indésirable en amont (730) ; et en réponse à la détection, par ladite surveillance, de la transmission indésirable en amont avec l'effet de filtrage, déterminer que l'émetteur indésirable est connecté et transmettre par le biais du câble à fibre optique (750).
EP23821684.0A 2023-01-31 2023-12-13 Procédé et système de test d'un réseau de fibre optique Pending EP4659384A1 (fr)

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EP23154194 2023-01-31
PCT/EP2023/085611 WO2024160435A1 (fr) 2023-01-31 2023-12-13 Procédé et système de test d'un réseau de fibre optique

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DE102006029967B3 (de) * 2006-04-20 2007-12-13 Siemens Ag Schutzvorrichtung zur Behebung von Signalstörungen in einem passiven optischen Netzwerk sowie passives optisches Netzwerk und Verfahren zur Behebung von Signalstörungen
US9350447B1 (en) * 2012-06-22 2016-05-24 Adtran, Inc. Systems and methods for protecting optical networks from rogue optical network terminals

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