OTDR Methodology for Identified Events

Abstract

An OTDR method and apparatus for characterizing an optical fiber link are provided. At least a first OTDR acquisition is performed on the optical fiber link. Based on the at least one first OTDR acquisition, one or more events are identified along the optical fiber link, and a value of at least one characteristic associated with each event is estimated. A second OTDR acquisition is performed on the optical fiber link to target a specific event among the identified events. Values ​​of one or more OTDR acquisition parameters for the second OTDR acquisition are determined so that the OTDR acquisition parameters include a second pulse width that is different from a first pulse width used in the first OTDR acquisition.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority under 35 USC §119(e) to U.S. Provisional Patent Application No. 62 / 744,320, filed on October 11, 2018; the specification of which is incorporated herein by reference. Technical Field

[0003] The present specification relates generally to optical time domain reflectometry (OTDR), and more particularly to using an OTDR to assess target events along an optical fiber link. Background Art

[0004] Optical Time Domain Reflectometer (OTDR, also used to refer to the corresponding device) is also widely used for the characterization of fiber optic links. OTDR is a diagnostic technique that transmits light pulses in a fiber optic link and detects and analyzes the return light generated by backscattering and reflections along the fiber link. Various "events" along the fiber link can be detected and characterized by appropriate analysis of the return light in the time domain, and the insertion loss of the fiber link under test and each component along the link can be characterized.

[0005] OTDR technology can be implemented in different ways, and advanced OTDR technology usually involves multi-pulse acquisition and analysis, whereby the OTDR device uses multiple acquisitions performed with different pulse widths to provide different spatial resolutions and noise level conditions for event detection and measurement along the optical fiber link to be tested, and provides a complete mapping of the optical link. In the multi-pulse method, shorter pulses are used to characterize the most proximal part of the link to be tested, that is, the part closest to the OTDR device, with higher resolution, while longer pulses provide more signal power to characterize the more distant parts of the optical link while reducing the spatial resolution. Therefore, the above-mentioned multi-pulse width method provides a significant improvement over the traditional single pulse width method.

[0006] While multi-pulse OTDR technology can provide a detailed characterization of the optical link under test, multiple acquisitions through different pulse widths imply long acquisition times, which is not suitable for high-volume testing where the number of individual tests to be performed is huge, such as required in the context of data centers and especially web-scale data centers.

[0007] OTDR acquisition time can be minimized by using long pulse widths, which increases the level of backscattered signals received from the fiber link under test and thereby minimizes the averaging time required for a given dynamic range specification. However, longer pulses also mean lower spatial resolution. As a result, such acquisitions tend to hide events that are too close to each other. In OTDR technology, this phenomenon is often referred to as event grouping or merged events.

[0008] On the other hand, the Light Source-Power Meter (LS / PM) test can quickly measure the Layer 1 characteristics of a fiber link, including total link insertion loss, total link length, and fiber link continuity. However, the LS / PM test does not provide any characterization of individual events along the fiber link under test. Only end-to-end measurements can be made.

[0009] Therefore, there remains a need for a rapid OTDR characterization method that can assess the complete fiber link, including individual events along it, rather than just end-to-end characteristics such as total link insertion loss, total link length, and fiber link continuity. Summary of the invention

[0010] An OTDR method and apparatus for characterizing an optical fiber link is provided. At least a first OTDR acquisition is performed on the optical fiber link. Based on the at least one first OTDR acquisition, one or more events are identified along the optical fiber link, and a value of at least one characteristic associated with each event is estimated. A second OTDR acquisition is performed on the optical fiber link to target a specific event among the identified events. Values ​​of one or more OTDR acquisition parameters for the second OTDR acquisition are determined so that the OTDR acquisition parameters include a second pulse width that is different from a first pulse width used in the first OTDR acquisition.

[0011] In one embodiment, a second OTDR acquisition is performed on the fiber link only if the estimated value of at least one characteristic does not meet the evaluation criteria. When there are no problems on the link (i.e., no bad connectors, bad splices, or macrobends), the OTDR acquisition can be fast (faster than multi-pulse measurements), but more time may be required to check for apparent defects when necessary. For example, such an OTDR method can be applied in the following situations: there is no specific request to specifically characterize every single event along the link, as long as a passing status can be confirmed.

[0012] In another embodiment, the target event is the far end of the fiber link to be tested, which is to be spliced ​​with another section of fiber. The values ​​of one or more OTDR acquisition parameters for a second OTDR acquisition are determined based on at least one characteristic associated with the target event. The OTDR acquisitions performed using the determined OTDR acquisition parameters are repeated in a continuous manner, and for each repeated OTDR acquisition, the value of at least one characteristic associated with the target event is estimated and displayed. This functionality allows the user to monitor the splicing process by monitoring at least one characteristic (e.g., loss and / or reflectivity) of the target event (which is the end of the fiber before splicing) in real time, and to initiate OTDR measurements to characterize the spliced ​​fiber link once the splicing process is complete.

[0013] According to one aspect, there is provided an OTDR method for characterizing an optical fiber link, the OTDR method comprising:

[0014] performing at least one first OTDR acquisition on the optical fiber link, wherein each OTDR acquisition is performed by: propagating a test signal corresponding to a first pulse width in the optical fiber link to be tested, and detecting corresponding return light from the optical fiber link to obtain an OTDR trace representing backscattered and reflected light according to a distance in the optical fiber link;

[0015] identifying, based on the at least one first OTDR acquisition, one or more events along the optical fiber link and estimating a value of at least one characteristic associated with each of the one or more events;

[0016] Upon determining that the estimated value of at least one characteristic associated with at least one of the events does not satisfy the evaluation criterion,

[0017] determining values ​​of one or more OTDR acquisition parameters, wherein the OTDR acquisition parameters include a second pulse width different from the first pulse width;

[0018] A second OTDR acquisition is performed on the optical fiber link using the determined OTDR acquisition parameters.

[0019] Advantageously, the OTDR method can be fast when there are no problems on the link under test, but may require more time to check for apparent defects when necessary. In other words, this method can quickly indicate whether the link under test is free of bad connectors, bad splices, and macrobends. It can also locate the problem, if any. Because this method does not require detailed characterization of every single event along the link when the pass-fail criteria are met, it can minimize the average measurement time for each fiber link under test.

[0020] The OTDR method can perform an initial OTDR measurement (involving one or more OTDR acquisitions) with long pulses and therefore low spatial resolution. Based on established evaluation criteria, such as pass / fail thresholds, an initial assessment of the link under test, including any located events, is performed from this initial measurement. If all events meet the evaluation criteria (i.e., pass results), no further investigation is required, and the assessment is completed in a short measurement time. It can be confirmed that the fiber link has no bad connectors, bad splices, or macrobends.

[0021] However, the initial fast OTDR measurement (performed with long pulses) tends to hide events that are close to each other. Thus, in some cases, two or more events along the fiber link under test may be indistinguishable in the initial fast OTDR measurement and appear merged, making it impossible to even identify that there are actually multiple events on what appears to be a single event. In this case, the corresponding characteristics of the merged event cannot be properly assessed, and the pass / fail status associated with the apparent single event may erroneously indicate a failure result, also referred to herein as a pseudo-failure result.

[0022] For example, when two or more events appear merged due to insufficient resolution, the insertion loss of the merged event is accumulated in the apparent single event. The evaluation criteria for insertion loss may then erroneously indicate an insertion loss exceeding the threshold for the apparent single event, while each individual event may show an insertion loss below the threshold. The pass / fail status associated with the apparent single event may then indicate a false fail result. This also applies to reflectivity. Thus, higher resolution provides a more reliable application of the pass / fail threshold.

[0023] Therefore, if (and optionally only if) a failure result (corresponding to a potential defect) is obtained for an event, further investigation is performed to try to eliminate the potential false failure result. In this case, an event-specific OTDR measurement can be performed using OTDR acquisition parameters selected to "best" examine the target event. Improving the spatial resolution to further investigate any potential faults can reveal events that were merged in the initial fast OTDR measurement so that the evaluation criteria can be better applied and the potential false failure results can be eliminated.

[0024] According to another aspect, there is provided an OTDR device for characterizing an optical fiber link, the OTDR device comprising:

[0025] an OTDR acquisition device, the OTDR acquisition device being connectable to an end of the optical fiber link for performing one or more OTDR acquisitions on the optical fiber link, wherein each OTDR acquisition is performed by: propagating a test signal corresponding to a first pulse width in the optical fiber link to be tested, and detecting corresponding return light from the optical fiber link to obtain an OTDR trace representing backscattered and reflected light according to a distance in the optical fiber link;

[0026] A processing unit, the processing unit receiving the OTDR trace and comprising:

[0027] i. an analysis module configured to identify one or more events along the optical fiber link based on at least one OTDR trace, and to estimate a value of at least one characteristic associated with each of the one or more events;

[0028] ii. an event investigation module configured to, upon determining that the estimated value of at least one characteristic associated with at least one of the events does not satisfy an evaluation criterion, determine values ​​of one or more OTDR acquisition parameters for a second OTDR acquisition to be performed on the optical fiber link, wherein the OTDR acquisition parameters include a second pulse width different from the first pulse width.

[0029] According to yet another aspect, there is provided a non-transitory computer-readable storage medium comprising instructions that, when executed, cause a processor to perform the following steps:

[0030] receiving at least one first OTDR acquisition performed on the optical fiber link to be tested, wherein each OTDR acquisition is performed by: propagating a test signal corresponding to a first pulse width in the optical fiber link to be tested, and detecting corresponding return light from the optical fiber link to be tested so as to obtain an OTDR trace representing backscattered and reflected light according to a distance in the optical fiber link to be tested;

[0031] a. based on the at least one first OTDR acquisition, identifying one or more events along the optical fiber link and estimating a value of at least one characteristic associated with each of the one or more events; and

[0032] b. upon determining that the estimated value of at least one characteristic associated with at least one of the events does not satisfy the evaluation criteria,

[0033] i. Determining values ​​of one or more OTDR acquisition parameters, wherein the OTDR acquisition parameters include a second pulse width different from the first pulse width.

[0034] In some embodiments, values ​​of one or more OTDR acquisition parameters are determined based at least on characteristics associated with the target event.

[0035] In some embodiments, the value of at least one characteristic of the merged event included in the target event is obtained from the second OTDR acquisition.

[0036] In some other embodiments, the updated value of at least one characteristic associated with the target event is obtained based on the second OTDR acquisition.

[0037] A plurality of events may be identified along the optical fiber link from the first OTDR acquisition, and the values ​​of one or more OTDR acquisition parameters may be determined based on at least one characteristic associated with a target event among the plurality of events.

[0038] The selected OTDR acquisition parameters for the second OTDR acquisition may include OTDR test signal pulse width, OTDR signal pulse repetition rate, average number, OTDR acquisition time, wavelength, receiver gain and bandwidth, sampling resolution, acquisition range (start / end) and / or any other parameters set by the OTDR device for performing OTDR acquisition. The OTDR acquisition parameters may be selected based on one or more characteristics of the target event so as to maximize spatial resolution while providing a dynamic range suitable for evaluating the target event.

[0039] In some embodiments, the dynamic range associated with the second OTDR acquisition may not allow the end of the fiber link to be reached.

[0040] In some embodiments, the characteristic associated with the target event includes at least one of insertion loss and cumulative loss prior to the target event.

[0041] According to another aspect, there is provided a computer program comprising instructions which, when executed by a processor, cause the processor to perform a method according to any one of the methods described above.

[0042] In this specification, unless otherwise stated, word modifiers such as "substantially" and "about" that modify conditions or relational characteristics of one or more features of an embodiment should be understood to mean that the condition or characteristic is defined within a tolerance that is acceptable for the proper functioning of the embodiment in the context of its intended application.

[0043] Throughout this specification, reference is made to optical reflection techniques and more specifically to OTDR techniques. It should be noted that optical reflection techniques are intended herein to encompass all variants of optical reflection techniques to which the provided methods and systems are equally applicable. Examples of such variants include optical frequency domain reflectometry (OFDR) (e.g., see US 7,515,276 by FROGGATT et al.) and coded OTDR techniques (see "Coded optical time domain reflectometry: principle and applications" by Park et al., Proc. of SPIE, Vol. 6781, 678129 (2007)) - also known as correlation OTDR. Other variants are also intended to be encompassed. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Other features and exemplary advantages of the present invention will become apparent to those skilled in the art through the following detailed description in conjunction with the accompanying drawings, in which:

[0045] Figure 1Ais a flow chart illustrating an OTDR method for characterizing at least one event along an optical fiber link according to one embodiment;

[0046] Figure 1B is a flow chart illustrating an OTDR method for characterizing an optical fiber link according to one embodiment;

[0047] Figure 2 is a graph illustrating an example of an OTDR acquisition showing characteristics associated with an identified event;

[0048] Figure 3 is a graph showing an example of a first OTDR acquisition showing a target event including a merged reflection event and an example of a second OTDR acquisition showing an unmerged merged reflection event;

[0049] Figure 4 is a graph showing an example of a first OTDR acquisition showing a target event including a merged non-reflective event and a second OTDR acquisition showing an unmerged merged non-reflective event;

[0050] Figure 5A is a flow chart illustrating steps of a method for selecting OTDR acquisition parameters to investigate a target event according to a first embodiment;

[0051] Figure 5B is a flow chart illustrating steps of a method for selecting OTDR acquisition parameters to investigate a target event according to a second embodiment;

[0052] Figure 5C is a flow chart illustrating steps of a method for selecting OTDR acquisition parameters to investigate a target event according to a third embodiment;

[0053] Figure 6 is a block diagram showing an exemplary embodiment of an OTDR apparatus for implementing the OTDR method of FIG. 1 ;

[0054] Figure 7 is a flow chart illustrating an OTDR method for monitoring an optical fiber splicing process according to one embodiment;

[0055] Figure 8 is shown in more detail Figure 6 A block diagram of an OTDR device; and

[0056] Fig. 9 It is shown Figure 8 A block diagram of an exemplary embodiment of an OTDR acquisition device of an OTDR device.

[0057] It should be noted that in all the drawings, similar features are identified with similar figure numbers. In order not to unduly obstruct the drawings, some elements may not be identified in some drawings if they have been identified in previous drawings. It should be understood herein that the elements of the drawings are not necessarily depicted to scale. Some mechanical or other physical components may also be omitted so as not to obstruct the drawings.

[0058] The following description is provided to obtain a comprehensive understanding of the methods, devices and / or systems described herein. Various changes, modifications and equivalents of the methods, devices and / or systems described herein will occur to those of ordinary skill in the art. Descriptions of well-known functions and structures may be omitted to enhance clarity and simplicity.

[0059] Although some features may be described with respect to separate exemplary embodiments, aspects are not necessarily limited to those embodiments, such that features from one or more exemplary embodiments may be combinable with other features from one or more exemplary embodiments. DETAILED DESCRIPTION

[0060] OTDR is a diagnostic technique for optical fiber links, in which a test signal in the form of light pulses is emitted in the optical fiber link to be tested, and the return optical signal caused by backscattering and reflections along the link is detected. The process of emitting a test signal and acquiring the return optical signal to obtain an OTDR trace therefrom is referred to herein as "OTDR acquisition". The acquired power level of the return optical signal as a function of time is referred to as an "OTDR trace" or "reflection trace", where the time scale represents the distance between the OTDR acquisition device and a point along the fiber link.

[0061] In the following description, techniques generally known to those skilled in the art of OTDR measurement and OTDR trace processing and analysis will not be explained or described in detail, and in this regard, the reader is referred to the available literature in the art. Such techniques considered to be known include, for example, signal processing methods for identifying and characterizing events from OTDR traces.

[0062] Each OTDR acquisition is understood to refer to the following actions: propagating a test signal including one or more test optical pulses of the same pulse width in the optical fiber link, and detecting the corresponding return optical signal from the optical fiber link as a function of time. The test optical pulse signal traveling along the optical fiber link will return toward its origin by (distributed) backscattering or (local) reflection. The acquired power level of the return optical signal as a function of time is called an OTDR track, where the time scale represents the distance between the OTDR acquisition device and the point along the optical fiber link. The optical acquisition can be repeated with varying pulse width values ​​to produce a separate OTDR track for each test pulse width.

[0063] Those skilled in the art will readily appreciate that, in the context of OTDR methods and systems, each light acquisition typically involves propagating a large number of substantially identical light pulses in a fiber link and averaging the results. In this case, the results obtained by averaging will be referred to herein as OTDR traces. It should also be understood that other factors may need to be controlled during light acquisition or from one light acquisition to the next, such as gain settings, pulse power, etc., as is well known to those skilled in the art.

[0064] "Backscatter" refers to the Rayleigh scattering generated by the interaction of the traveling light with the fiber medium along the fiber link, thereby generating a generally inclined background light (in logarithmic units, i.e., dB on the ordinate) on the OTDR track, whose intensity disappears at the end of the traveling pulse range. An "event" along the fiber will generally cause a more localized drop in the backscattered light on the OTDR track - this can be attributed to local losses, and / or cause a local reflection peak. It should be understood that the "event" characterized by the OTDR method described herein can be generated by any disturbance that affects the return light along the fiber link. Typically, an event can be generated by a fiber splice along the fiber link, which is characterized by a local loss with little or no reflection. Mating connectors can also generate events that generally present reflections, although in some cases these events may not be detected. The OTDR method and system can also provide identification of events such as fiber breakage and losses caused by bends in the fiber, such as fiber breakage events characterized by significant local losses, and often accompanied by reflection peaks. Finally, any other component along the fiber link may also appear as an "event" that produces local losses.

[0065] Now referring to the accompanying drawings, Figure 1A is a flow chart illustrating an OTDR method for characterizing at least one event along an optical fiber link under test, according to one embodiment.

[0066] In steps 12 and 14, a quick OTDR measurement is performed on the fiber link.

[0067] First, in step 12, a first set of one or more OTDR acquisitions are performed on the fiber link to be tested. In one embodiment, a single OTDR acquisition is performed using, for example, preconfigured or predetermined acquisition parameters, which are selected to cover a given maximum distance and loss range of the fiber link (e.g., 40 km and 15 dB). In other embodiments, a set of OTDR acquisitions are performed using a set of different acquisition parameters, such as different pulse widths or different wavelengths.

[0068] In step 14, OTDR analysis is performed based on the OTDR acquisition obtained from step 12 to identify events along the fiber link, including the ends of the fiber link, and to provide a characterization of the identified events. Events can be identified based on the location of the event, i.e., the distance along the fiber link at which the event is identified. Events on the OTDR trace are typically identified in the art by analyzing the OTDR trace to identify local dips and / or reflection peaks of back-reflected / back-scattered light. The presence of one or the other is typically interpreted as an event.

[0069] It is also common in the art to characterize events along a fiber link by attributing values ​​to three different properties: the location of the event along the fiber link, the insertion loss associated with the event, and the reflectivity at the event (when present). Depending on the circumstances, one or a combination of multiple of these properties may be evaluated for a given event. In some embodiments, all three parameters are evaluated for each identified event in step 14. The result of this analysis is a list of events that includes location values ​​as well as the insertion loss and reflectivity associated with each event, and may be referred to as an OTDR measurement result.

[0070] In steps 22 and 24, a second OTDR acquisition is performed on the fiber link to target specific ones of the identified events.

[0071] In step 22, a set of new OTDR acquisition parameter values ​​is determined for use in performing event-specific OTDR measurements. The set of new OTDR acquisition parameters to be determined may include pulse width Δt, pulse repetition period P rep , averaging number Av, acquisition time T and / or any other parameters set by the OTDR device for performing OTDR acquisition.

[0072] In one embodiment, the values ​​of the set of new OTDR acquisition parameters are determined based on at least one characteristic of the target event (see Figure 5A and Figure 5B ). According to the location D of the target event E E , the insertion loss L of the target event E E , the reflectivity R of the target event E E , the cumulative loss L before the target event E CUM and the location D of the end of the optical fiber link EOL The new set of OTDR acquisition parameters is determined by one or more of the following.

[0073] Furthermore, the new set of OTDR acquisition parameters may be determined to satisfy an allowed acquisition time (eg, 2 to 15 seconds) and a dynamic range sufficient to characterize the target event. Step 22 may determine acquisition parameters that satisfy these requirements while maximizing spatial resolution.

[0074] In another embodiment, the values ​​of the new set of OTDR acquisition parameters are determined based at least on the acquisition parameters used in step 12 (see Figure 5C ). The new set of OTDR acquisition parameters is then selected with the aim of improving the spatial resolution compared to the first OTDR acquisition by selecting a shorter pulse width and a larger number of averages and thus a longer acquisition time.

[0075] In step 24 , at least one OTDR acquisition is performed on the optical fiber link to be tested using the new set of OTDR acquisition parameters determined in step 22 .

[0076] Optionally, the event-specific OTDR measurements of steps 22 and 24 may include more than one OTDR acquisition performed with different sets of OTDR acquisition parameters. For example, for reflective events, a second acquisition with higher spatial resolution but lower dynamic range may be used to better distinguish merged events within a potential fault, even though such acquisition may not be used to determine the value of the insertion loss associated with each merged event.

[0077] Figure 1B It is shown that the use Figure 1A Flowchart of an exemplary OTDR method for characterizing a fiber link of the method of FIG. The OTDR method can be fast (e.g., faster than multi-pulse measurement) when the fiber link under test shows no faults (no bad connectors, bad splices, or macrobends), while taking more time to investigate when faults are identified in order to try to eliminate pseudo-faults that may be caused by combined events.

[0078] In steps 12 and 14, a quick OTDR measurement is performed on the fiber link.

[0079] First, in step 12, a first set of one or more OTDR acquisitions are performed on the optical fiber link to be tested. In one embodiment, a single OTDR acquisition is performed using, for example, pre-configured or predetermined acquisition parameters, which are selected to cover a given maximum distance and loss range (e.g., 40km and 15dB) of the optical fiber link. In other embodiments, a set of OTDR acquisitions is performed using a set of different acquisition parameters, such as different pulse widths or different wavelengths. However, the goal of this fast OTDR measurement is to limit the acquisition time. The OTDR acquisition time can be minimized by using a larger pulse width, which increases the level of the backscattered signal received from the optical fiber link to be tested, and thereby minimizes the acquisition time required for a given dynamic range requirement. For example, an acquisition time of 300ms or an acquisition time between 200ms and 500ms can be used.

[0080] The number of OTDR acquisitions in the set of OTDR acquisitions may depend on the distance range and loss range to be covered (eg, 40 km and 15 dB), but the total acquisition time is typically limited to a maximum of a few seconds (eg, 2 to 3 seconds).

[0081] Optionally, the distance range and loss range to be covered can be obtained by performing a preliminary OTDR acquisition that allows the link length to be estimated. This optional step can help optimize the acquisition parameters for the fiber link to be tested. For example, an approximate link length can be obtained from the preliminary OTDR acquisition, which can then be used to determine the repetition rate to be applied in subsequent OTDR acquisitions.

[0082] In step 14, OTDR analysis is performed based on the OTDR acquisition obtained from step 12 to identify events along the fiber link, including the end of the fiber link, and to provide a detailed characterization of the identified events.

[0083] refer to Figure 2 , which shows an example of an OTDR trace obtained from step 12. The OTDR trace shows an event E identified along the fiber link, which passes through position D E , Insertion loss L E and reflectivity R E Event E can also be characterized by the cumulative loss L from the beginning of the link until the event CUM The OTDR trace also allows the location of the end of the fiber link to be determined. EOL and the total link loss L link .

[0084] Optionally, the fast OTDR measurement may include an additional step (not shown) of performing additional OTDR acquisitions performed with shorter pulse widths and slightly longer acquisition times (e.g., 2 seconds) in order to specifically cover the end of the fiber link with higher spatial resolution and detect potential hidden faults at the end of the link. The dynamic range requirements associated with such additional OTDR acquisitions may be relaxed by taking into account the total link length and insertion loss as determined in step 14, thereby allowing the use of smaller pulse widths.

[0085] Back to Figure 1B The result of a fast OTDR measurement may be a list of events associated with estimated values ​​of corresponding characteristics, such as position D E , Insertion loss L E and reflectivity R E .

[0086] In step 16, the determined characteristic is compared to the established evaluation criteria to determine whether the characteristic is acceptable, for example, determined according to a given threshold. For example, the evaluation criteria may include a pass / fail threshold, and step 16 may include determining a pass / fail status associated with each event by comparing the estimated value of the characteristic to the pass / fail threshold. In some embodiments, the established threshold may depend on the type of event identified. For example, the insertion loss threshold for a non-reflective event may be set to 0.3 dB, while the insertion loss threshold for a reflective event may be set to 0.7 dB. Thus, if a non-reflective event E is identified and an insertion loss L is found to be E If the associated value of exceeds the insertion loss threshold (e.g., 0.3 dB), then event E is marked as a potential fault (e.g., failure) because it does not meet an evaluation criterion. Of course, the reflectivity R associated with the reflective event can be similarly E The value of is compared with an established reflectivity threshold to determine whether the event meets an evaluation criterion, such as a pass / fail threshold. Whenever one characteristic of an event does not meet the associated evaluation criterion, the event is identified as a potential failure.

[0087] Of course, any optional additional OTDR acquisitions performed in steps 12 and 14 to specifically cover the fiber ends may be analyzed in step 16 to detect potential faults close to the distal connector.

[0088] In decision box 18, if all events identified along the fiber link meet the evaluation criteria according to step 16, for example, all determined characteristics are below the applicable pass / fail threshold, then in step 20, the OTDR measurement is complete and the OTDR measurement results can be saved in memory, displayed, or otherwise output or made available. The fiber link under test is considered acceptable, so that no further investigation is required. Therefore, the OTDR measurement is complete and it can be confirmed that there are no defects along the fiber link, and this is completed in a very short acquisition time, for example, in less than 500ms.

[0089] However, in decision block 18, if one or more events identified along the optical fiber link do not meet the evaluation criteria, ie, one or more events are identified as potential faults, then more investigation is required.

[0090] It should be understood that the OTDR acquisition parameters for fast OTDR measurements are selected to cover the dynamic range required for the fiber link to be tested with a short acquisition time. Therefore, the selected pulse width for fast OTDR measurements may be relatively long, with an associated low spatial resolution. Therefore, fast OTDR measurements tend to hide events that are too close to each other, which are referred to herein as merged event groups, or simply merged events.

[0091] Therefore, in some cases, two or more events along the link under test may not be individually distinguishable in the initial fast OTDR measurement and appear to be merged, making it impossible to even identify that there are actually multiple events on what appears to be a single event. In this case, the corresponding characteristics of the merged event cannot be properly assessed, and the pass / fail status associated with the merged event may erroneously indicate a failed result, also referred to herein as a false fail result.

[0092] Therefore, if (and optionally, only if) a failure result is obtained for an event (corresponding to a potential fault), further investigation is performed to attempt to eliminate the potential spurious failure result. In this case, event-specific OTDR measurements are performed in steps 22, 24, and 26 to examine the target event using OTDR acquisition parameters selected to "best" examine the fault event (referred to herein as the "target event"). Improving the spatial resolution to further investigate any potential faults can reveal events that were merged in the initial fast OTDR measurement, to which evaluation criteria can be better applied to eliminate potential spurious failure results.

[0093] In step 22, a set of new OTDR acquisition parameter values ​​is determined for use in performing event-specific OTDR measurements. The set of new OTDR acquisition parameters to be determined may include pulse width Δt, pulse repetition period P rep , averaging number Av, acquisition time T and / or any other parameters set by the OTDR device for performing OTDR acquisition.

[0094] In one embodiment, the values ​​of the set of new OTDR acquisition parameters are determined based on at least one characteristic of the target event (see Figure 5A and Figure 5B ). According to the location D of the target event E E , the insertion loss L of the target event E E , the reflectivity R of the target event E E , the cumulative loss L before the target event E CUM and the location D of the end of the optical fiber link EOL The new set of OTDR acquisition parameters is determined by one or more of the following.

[0095] Furthermore, the new set of OTDR acquisition parameters may be determined to satisfy an allowed acquisition time (eg, 2 to 15 seconds) and a dynamic range sufficient to characterize the target event. Step 22 may determine acquisition parameters that satisfy these requirements while maximizing spatial resolution.

[0096] In another embodiment, the values ​​of the new set of OTDR acquisition parameters are determined based at least on the acquisition parameters used in step 12 (see Figure 5C ). The new set of OTDR acquisition parameters is then selected with the aim of improving the spatial resolution compared to the first OTDR acquisition by selecting a shorter pulse width and a larger number of averages and thus a longer acquisition time.

[0097] The new set of OTDR acquisition parameters may be selected to improve spatial resolution compared to the initial fast OTDR measurement in order to distinguish potential merged events. Because the OTDR acquisition is intended to specifically investigate the target event, the event-specific OTDR measurement does not need to provide a dynamic range that reaches the end of the fiber link. Figure 5A , Figure 5B and Figure 5C An exemplary method for selecting OTDR acquisition parameters to investigate a target event is described.

[0098] In step 24 , at least one OTDR acquisition is performed on the optical fiber link to be tested using the new set of OTDR acquisition parameters determined in step 22 .

[0099] Optionally, the event-specific OTDR measurements of steps 22 and 24 may include more than one OTDR acquisition performed with different sets of OTDR acquisition parameters. For example, for reflective events, a second acquisition with higher spatial resolution but lower dynamic range may be used to better distinguish merged events within a potential fault, even though such acquisition may not be available to determine the value of the insertion loss associated with each merged event.

[0100] In step 26, an OTDR analysis is performed based on the OTDR acquisition obtained from step 24 to obtain a value of at least one characteristic of any merged events associated with the target event, or to obtain an updated value of at least one characteristic of the target event. From step 26, it can be determined whether the target event is a real fault or whether it corresponds to a merged event. Step 26 can also compare the determined characteristics of any now unmerged events with established evaluation criteria to determine whether the characteristics are acceptable, for example according to a given pass / fail threshold.

[0101] In one embodiment, if more than one event is revealed (unmerged events) and the insertion loss values ​​of the unmerged events can be determined, the determined characteristic can be compared to the established evaluation criteria to determine whether the characteristic is acceptable. However, if the event-specific OTDR measurement reveals more than one unmerged event, but individual insertion losses cannot be measured due to insufficient spatial resolution, the evaluation criteria can be optionally applied to the group by comparing the total insertion loss of the group of events associated with the target event with the sum of the individual thresholds for each event of the group. If the event-specific OTDR measurement does not reveal any merged events (a single event is seen), the updated value of the characteristic associated with the target event can be compared to the established evaluation criteria.

[0102] In some embodiments, the OTDR analysis of step 26 may update a characterization of all events identified along the fiber link, while in other embodiments, only target events and / or unmerged events are analyzed. All events may be assessed (within the spatial resolution limits of a given OTDR method and apparatus) and the OTDR measurement results are the final results.

[0103] Then, in step 30, the OTDR measurement is completed and the OTDR measurement values ​​may be saved in memory, displayed, or otherwise output or made available.

[0104] Optionally, in step 28, the analysis of step 26 may be repeated for other target events if other potential faults were identified in step 16. Additional event-specific OTDR measurements may also be performed to target any other potential faults identified in step 16.

[0105] Figure 3 An example of an OTDR trace 40 obtained from a fast OTDR measurement and showing a target event including a merged reflective event is shown. Figure 3 Also shown is an OTDR trace 42 obtained from an event-specific OTDR measurement and revealing two reflective events. Although individual insertion loss values ​​cannot be properly derived from the OTDR trace 42, the revealed presence of two events can be used to modify the evaluation criteria. For example, the total insertion loss of the event group can be compared to the sum of the individual thresholds associated with each event of the group.

[0106] Figure 4An example of an OTDR trace 44 obtained from a fast OTDR measurement and showing a target event that appears to be a single event but actually includes merged non-reflective events is shown. The insertion loss of the merged events accumulates to 0.5 dB in the apparent single event, which exceeds an exemplary insertion loss threshold of, for example, 0.3 dB for non-reflective events. Such insertion loss would produce a false failure result. Figure 4 Also shown is an OTDR trace 46 obtained from an event-specific OTDR measurement and revealing two uncombined non-reflective events. In this case, for each uncombined event, an updated value of insertion loss can be appropriately derived from the OTDR trace 46 and then compared to the evaluation criteria to rate the fiber link. For example, the insertion loss value of the uncombined event can be 0.25 dB, which is below the insertion loss threshold and produces a pass status.

[0107] In another example (not shown), the target event E may first be identified as a non-reflective event (reflectivity value R E low or equal to zero), and found that the insertion loss L E The associated value of exceeds the insertion loss threshold of, for example, 0.3 dB for non-reflective events. Event E is then marked as a potential fault (failure) because it does not meet one evaluation criterion. However, long pulses may be prone to hiding connector reflections. If the analysis of step 26 based on the second OTDR acquisition subsequently reveals that event E is a reflective event, a different insertion loss threshold of, for example, 0.7 dB for reflective events may be applied and event E may be found to produce a pass result.

[0108] Figure 5A , Figure 5B and Figure 5C An exemplary method for selecting OTDR acquisition parameters to investigate a target event is shown. Figure 5A , Figure 5B and Figure 5C The methods constitute some possible implementations of step 22 of FIG. 1 , and those skilled in the art will be able to design variations and other implementations not described herein.

[0109] Figure 5A The method of determining a set of OTDR acquisition parameters for performing event-specific OTDR measurements. In this implementation, the values ​​of the set of new OTDR acquisition parameters are determined according to: the insertion loss L of the target event E E , the cumulative loss L before the target event E CUM (or the cumulative loss after the target event E (L E +L CUM )) The location of the end of the optical fiber link D EOL, signal-to-noise ratio requirement SNR and maximum allowed acquisition time T. It should be noted that in other implementations, the values ​​of the new set of OTDR acquisition parameters can be determined based on other characteristics of the target event, including, for example, reflectivity R E and / or position D E and / or other characteristic measurement parameters.

[0110] The method receives in step 50 values ​​determined from a previous fast OTDR measurement, including the event insertion loss L E , cumulative loss L CUM and link end position D EOL In step 52, a value of a signal-to-noise ratio requirement SNR is received. For example, this value may be preset as a fixed value or preconfigured for a given OTDR device. In step 54, a value of a maximum allowed time T for event-specific acquisition is received. The signal-to-noise ratio requirement and the maximum allowed acquisition time T may be predetermined or provided, for example, via configuration parameters.

[0111] In step 56, the event insertion loss L E , cumulative loss L CUM The signal-to-noise ratio requirement (SNR) determines the dynamic range (DR) required in the OTDR acquisition to allow characterization of the target event. The required dynamic range (DR) is determined as the sum of these values:

[0112] DR≥L E +L CUM +SNR

[0113] It will be appreciated that instead of providing the event insertion loss L E and cumulative loss L CUM provides a single value of the cumulative loss after the target event (L E +L CUM ) and determining the required dynamic range DR accordingly is equivalent. Of course, other methods can be used to calculate the required dynamic range, including, for example, the following method for Figure 5B Step 78 of the method is described in the method.

[0114] In step 58, as is known in the art, based on the position D of the link end EOL To determine the repetition period P of the pulse test signal rep More specifically, the repetition period P rep The minimum repetition period that can be used while avoiding ghost pulses can be determined as:

[0115] Prep≥2·D EOL ÷c / n eff

[0116] Where c / n eff Corresponds to the speed of light in a fiber optic link. In other embodiments, the safety repetition period may be determined based on twice the round trip to the end of the link to ensure that any echoes generated by reflectivity at the end of the link have sufficient time to return:

[0117] Prep≥2·2·D EOL ÷c / n eff

[0118] In other embodiments, the distance D of the end of the returning optical signal may be determined by examining the attenuation of the returning optical signal based on a previous fast OTDR acquisition. EOS , to determine the repetition period P rep The minimum value of D EOS may be better than the detection end of the link D EOL Then P rep Can be determined as:

[0119] Prep≥2·D EOS ÷c / n eff

[0120] In step 60, the average number Av, i.e. the number of repetition periods, is determined according to the determined repetition period Prep and the maximum allowed acquisition time T, so as to maximize the average number Av while keeping the acquisition time below the maximum allowed value:

[0121] Av≤T / Prep

[0122] In step 62, a pulse width Δt is determined based on the required dynamic range DR and the average number Av. The determination may be based on, for example, a theoretical or previous dynamic range DR characterization of an OTDR device, which defines the dynamic range DR of the OTDR trace based on the pulse width Δt and the average number Av. The dynamic range DR characterization may be provided, for example, in the form of a table or an algebraic function. The pulse width Δt may then be selected as the minimum pulse width Δt that provides the required dynamic range DR for the determined average number Av.

[0123] In step 64, the pulse width Δt and the repetition period P are selected. rep The average number Av is output to an OTDR acquisition device or otherwise made available to the OTDR acquisition device for performing event-specific OTDR acquisitions.

[0124] It should be noted that Figure 5AThe method is a possible implementation of step 22 of Figure 1. For example, in other implementations, steps 60 and 62 can be replaced by a single step that more generally determines the pulse width Δt based on the required dynamic range DR, the maximum acquisition time T, and the required repetition period Prep. In some OTDR systems, the average number Av may vary with the pulse width for the determined acquisition time T. In this case, the pulse width Δt can be selected as the minimum pulse width that can provide the required dynamic range DR for the required repetition period Prep and the maximum acquisition time T.

[0125] Figure 5B The method of FIG. 1 represents another possible implementation of step 22 to determine a set of OTDR acquisition parameters for performing event-specific OTDR measurements. In this implementation, the values ​​of the new set of OTDR acquisition parameters are determined according to: the insertion loss L of the target event E E , the cumulative loss L before the target event E CUM (or the cumulative loss after the target event E (L E +L CUM )), the repetition period Prep1 and the maximum allowed acquisition time T of the first OTDR acquisition used in step 12.

[0126] The method receives in step 70 values ​​determined from a previous fast OTDR measurement, including the event insertion loss L E and cumulative loss L CUM In step 72, a value of the repetition period Prep1 used in the first OTDR acquisition is received. In step 74, a value of a maximum allowed time T for event-specific acquisition is received. The maximum allowed acquisition time T may be predetermined or provided, for example, via configuration parameters.

[0127] In step 76, the required signal-to-noise ratio SNR value is determined. This can be determined, for example, based on the insertion loss L of the target event E. E Then, the SNR can be determined so that the OTDR trace can properly reveal and measure the signal corresponding to L E The insertion loss is good enough so that the insertion loss L E The lower value of selects the larger value of SNR, for the insertion loss L E Larger values ​​of select lower values ​​of SNR (e.g., when L E <0.5dB, SNR=12dB, and when L E ≥0.5dB, SNR=9dB). Optionally, an insertion loss L can be added E The value of (upper limit is a constant value, such as 3dB):

[0128] SNR=(9 or 12dB)+min(3dB,L E )

[0129] Of course, other methods may be used to determine the required SNR. For example, the required SNR may be preset as a fixed value or pre-configured for a given OTDR device.

[0130] In step 78, according to the accumulated loss L CUM The required signal-to-noise ratio (SNR) determines the required dynamic range (DR) that allows characterization of the target event. r The required dynamic range DR is determined from the sum of these values ​​as:

[0131] DR≥K+L CUM +SNR

[0132] Here, K is a constant that may be preset as a fixed value or preconfigured (eg, K=3 dB).

[0133] In step 80, the repetition period P of the pulse test signal is set to rep Determined to correspond to the repetition period P used in the first OTDR acquisition rep1 Although not necessarily optimal for a given fiber link under test, the first OTDR acquisition is known to be suitable for avoiding ghost pulses and can therefore be used for the event-specific OTDR acquisition.

[0134] In step 82, according to the required dynamic range DR r , the maximum allowed acquisition time T and the repetition period Prep. The determination may be based on, for example, a theoretical or previous dynamic range DR characterization of an OTDR device, which defines the dynamic range DR of the OTDR trace as a function of the pulse width Δt, the maximum allowed acquisition time T and the repetition period Prep. The dynamic range DR characterization may be provided, for example, in the form of a table or an algebraic function. Then, the pulse width Δt may be selected as the minimum pulse width Δt that provides the required dynamic range DR for the maximum allowed acquisition time T and the determined repetition period Prep.

[0135] In step 84, the average number Av, i.e. the number of repetition periods, is determined. The average number Av can be obtained directly from the representation used in step 82, or it can be determined based on the determined repetition period Prep and the maximum allowed acquisition time T in order to maximize the average number Av while keeping the acquisition time below the maximum allowed value:

[0136] Av≤T / Prep.

[0137] In step 86, the pulse width Δt and the repetition period P are selected. repThe average number Av is output to an OTDR acquisition device or otherwise made available to the OTDR acquisition device for performing event-specific OTDR acquisitions.

[0138] Figure 5C The method of FIG. 1 represents another possible implementation of step 22 to determine a set of OTDR acquisition parameters for performing event-specific OTDR measurements. In this implementation, the values ​​of the new set of OTDR acquisition parameters are determined based on at least the first acquisition parameters used for a previous fast OTDR measurement. These values ​​of the new set of OTDR acquisition parameters can be determined based on: the pulse width Δt1 and the repetition period P used for the previous fast OTDR measurement. rep 1, and a dynamic range DR1 corresponding to these first OTDR acquisition parameters.

[0139] exist Figure 5C In the method of , the new set of OTDR acquisition parameters is selected to improve the spatial resolution compared to the previous fast OTDR measurement by selecting a shorter pulse width Δt and a longer acquisition time T.

[0140] In step 90, the values ​​of some first acquisition parameters used for a previous fast OTDR measurement are received, including the pulse width Δt1 and the repetition period P rep 1 and the values ​​of the dynamic range DR1 corresponding to these first OTDR acquisition parameters.

[0141] In step 92, a target dynamic range DR for the event-specific OTDR acquisition is determined to correspond to the dynamic range DR1 corresponding to the first OTDR acquisition.

[0142] In step 94, the repetition period P of the pulse test signal is set to rep Determined to correspond to the repetition period P used in the first OTDR acquisition rep1 .

[0143] In step 96, a pulse width Δt is determined based on the pulse width Δt1 used in the first OTDR acquisition. The pulse width Δt is determined to be shorter than the pulse width Δt1 in order to improve the spatial resolution compared to the previous fast OTDR measurement. For example, the pulse width Δt can be determined as a predetermined fraction of the pulse width Δt1, such as one third of the pulse width Δt1, for example:

[0144] Δt=Δt1 / 3

[0145] Of course, other ratios may be used, such as 2, 4, 5, etc.

[0146] In step 98, the average number Av, i.e. the number of repetition periods, is determined as the average number Av required for obtaining the dynamic range DR with the determined pulse width Δt and repetition period Prep. For example, the determination may be based on, for example, a theoretical or previous dynamic range DR characterization of an OTDR device which defines the dynamic range DR of the OTDR trace as a function of the pulse width Δt, the average number Av and the repetition period Prep.

[0147] It should be noted that the acquisition time T, the average number Av and the repetition period Prep are interrelated values. Therefore, alternatively, the acquisition time T can be determined in step 98 instead of the average number Av.

[0148] In step 100, the pulse width Δt and the repetition period P are selected. rep The sum of the average number Av (or the acquisition time T) is output to an OTDR acquisition device or otherwise made available to an OTDR acquisition device to perform event-specific OTDR acquisition.

[0149] Figure 6 An embodiment of an OTDR device 100 is shown for use in the OTDR method of FIG. 1 to characterize an optical fiber link 110 that includes one or more events E along it.

[0150] The OTDR device 100 includes an OTDR acquisition device 140, which is connectable to the fiber link 110 under test via an output interface 164 for performing OTDR acquisition of the fiber link 110. The OTDR acquisition device 140 includes conventional optical hardware and electronic devices known in the art for performing OTDR acquisition of a fiber link.

[0151] The OTDR device 100 also includes one or more processing units 142 configured to analyze the OTDR traces obtained by the OTDR acquisition device 140 to obtain OTDR measurements therefrom and / or determine values ​​of one or more OTDR acquisition parameters for at least one OTDR acquisition. The one or more processing units 142 may include one or more processors.

[0152] The processing unit 142 may implement an analysis module 144 that is configured to identify and characterize one or more events along the fiber link by appropriate analysis of the acquired OTDR traces. Events are typically characterized by location, insertion loss, and reflectance characteristics, while fiber segments may be characterized by length and attenuation parameters. The analysis module 144 may be implemented by analysis software that performs the calculations necessary to characterize events along one of the fiber links 110. The analysis software identifies and characterizes events along the fiber link 110 by analyzing one or more OTDR traces. In one embodiment, the analysis software performs steps 14, 16, 26 of the method of FIG. 1 described above, and may identify target events that require further investigation.

[0153] The processing unit 142 may also implement an event investigation module 146 that is configured to determine the values ​​of one or more OTDR acquisition parameters for at least one event-specific OTDR acquisition to be performed on the optical fiber link. The event investigation module 146 may be implemented by event investigation software that performs the calculations necessary to determine the OTDR acquisition parameters. In one embodiment, the event investigation software performs step 22 of the method of FIG. 1 described above.

[0154] The analysis module 144 and the event investigation module 146 may be made integral 146, partially external or completely external to the OTDR device 100 used to perform the acquisition.

[0155] The processing unit 142 may also implement a controller 148 configured to control the OTDR acquisition device 140 to start OTDR acquisition according to the determined OTDR acquisition parameters. The controller 146 may be implemented by controller software and may be used to perform steps 18 and 28 of the method of FIG. 1 described above.

[0156] The OTDR acquisition device 140 includes a light generating component 154 , a detecting component 156 , and a directional coupler 158 .

[0157] The optical generation assembly 154 is implemented by a laser 160 driven by a pulse generator 162 to generate a test signal including a test optical pulse with desired characteristics. As known in the art, the optical generation assembly 154 is adapted to generate a test optical pulse with a pulse width, a repetition period and an optical power that varies by appropriately controlling the pattern produced by the pulse generator 162. Those skilled in the art will appreciate that it may be beneficial or required by the application to perform OTDR measurements at various wavelengths. For this purpose, in some embodiments, the optical generation assembly 154 is adapted to generate a test optical pulse with a wavelength that varies by adopting, for example, a tunable laser 160. It will be appreciated that the optical generation assembly 154 can combine both pulse width control capability and wavelength control capability. Of course, different and / or additional components, such as modulators, lenses, mirrors, optical filters, wavelength selectors, etc., may be provided in the optical generation assembly.

[0158] The light generating assembly 154 is coupled to the output interface 164 of the OTDR acquisition device 140 through a directional coupler 158 having three or more ports, such as a circulator. The first port is connected to the light generating assembly 154 to receive the test light pulse therefrom. The second port is connected to the output interface 164. The third port is connected to the detection assembly 156. The connection allows the test light pulse generated by the light generating assembly 154 to be coupled to the output interface 164, and allows the return light signal generated by backscattering and reflection along the optical fiber link 110 to be coupled to the detection assembly 156.

[0159] The detection assembly 156 includes: a light detector 166, such as a photodiode, an avalanche photodiode or any other suitable photodetector, which detects the return light signal corresponding to each test light pulse; and a converter 168, which is used to convert an electrical signal proportional to the detected return light signal from analog to digital to allow processing by the processing unit 142. It will be understood that the detected return light signal can of course be amplified, filtered or otherwise processed before analog-to-digital conversion. The power level of the return light signal as a function of time - which is obtained from the above detection and conversion - is referred to as an acquisition of the OTDR track. Those skilled in the art will readily understand that in the context of OTDR methods and systems, each light acquisition generally involves propagating a large number of substantially identical light pulses in the optical fiber link and averaging the results to improve the signal-to-noise ratio (SNR). In this case, the result obtained by averaging is referred to herein as an OTDR track. It will also be understood that other factors may need to be controlled during light acquisition or from one light acquisition to the next, such as gain settings, pulse power, etc., as known to those skilled in the art.

[0160] Of course, the OTDR acquisition device 140 can also be used to perform multiple acquisitions with varying pulse widths to obtain multi-pulse width OTDR measurements. The OTDR traces thus obtained will typically be stored in a memory (not shown) for further processing. In one embodiment, the OTDR acquisition device 140 performs steps 12 and 24 of the method of FIG. 1 described above.

[0161] The controller 148 is used to control the acquisition conditions of each light acquisition by controlling the light generating component 154 to generate test light pulses with variable pulse width, repetition period, wavelength and / or optical power.

[0162] The OTDR trace acquired from the optical fiber link 110 is received and analyzed by the processing unit 142 .

[0163] The described systems and methods may also involve performing additional light acquisitions under varying acquisition conditions. For example, the systems and methods described herein may further employ multi-pulse width bidirectional OTDR analysis, as described in U.S. Application Publication No. US2014 / 0198311A1, dated July 17, 2014, to L'Heureux et al., and commonly owned by the applicant and hereby incorporated by reference.

[0164] Figure 7 is shown for characterizing a fiber link and using Figure 1A Flow chart of another exemplary OTDR method of the method. Figure 7 The OTDR method is used to monitor fiber splicing. Then, the target event E is the far end of the fiber link to be tested, which will be spliced ​​with another section of fiber. Figure 7 The OTDR method includes Figure 1B For the sake of brevity, the details of these similar steps will not be repeated.

[0165] In steps 12 and 14, a first OTDR measurement is performed on the (not yet spliced) optical fiber link.

[0166] First, in step 12, a first set of one or more OTDR acquisitions are performed on the optical fiber link to be tested.

[0167] In step 14, OTDR analysis is performed based on the OTDR acquisition obtained from step 12 to identify events along the fiber link, including the end of the fiber link to be spliced.

[0168] In step 22, the values ​​of one or more OTDR acquisition parameters for event-specific OTDR acquisition are determined based on at least one characteristic associated with the target event E, i.e., the end of the optical fiber link, to perform event-specific OTDR measurements. The set of new OTDR acquisition parameters to be determined may include pulse width Δt, pulse repetition period P rep , average number Av, acquisition time T and / or any other parameters set by the OTDR device for performing OTDR acquisition. E , the reflectivity R of the target event E E , the cumulative loss L before the target event E CUM and the location D of the end of the optical fiber link EOL The new set of OTDR acquisition parameters is determined by one or more of the following.

[0169] Once the fiber ends are identified in step 14, the splicing process can be initiated and monitored in steps 24 and 26. Once the splicing process begins, additional lengths of fiber are added to the fiber link under test, and position D E The target event at becomes a reflective or non-reflective event E, and the insertion loss of the reflective or non-reflective event E is L E and reflectivity R E can be determined and monitored to monitor the splicing process.

[0170] In steps 24 and 26, OTDR acquisitions performed using the determined OTDR acquisition parameters are repeated in a continuous manner, and for each repeated OTDR acquisition, a value of at least one characteristic associated with the target event E (eg, insertion loss and / or reflectivity) is estimated and displayed.

[0171] In step 24 , at least one OTDR acquisition is performed on the optical fiber link to be tested using the new set of OTDR acquisition parameters determined in step 22 .

[0172] In step 26, an OTDR analysis is performed based on the OTDR acquisition obtained from step 24 to obtain a value of at least one characteristic (e.g., insertion loss and / or reflectivity) associated with the target event E (which is the fiber end before splicing). The updated value is then displayed to the user for each repeated OTDR acquisition.

[0173] Then, steps 24 and 26 are repeated in a continuous manner, so that the user can subsequently monitor the splicing process by monitoring at least one characteristic (e.g., insertion loss and / or reflectivity) of the target event E in real time. E and / or reflectivity R E The value of determines the completion of the splicing process.

[0174] When the user determines that the insertion loss value is close to zero and the reflectivity value drops to a very low value, he knows that the splicing process is complete. In step 32, the technician can interrupt the repeated acquisition, for example by pressing a "capture" button on the OTDR device, in order to save the last OTDR measurement results in memory. Optionally or alternatively, further OTDR measurements can be initiated to better characterize the spliced ​​fiber link, including the new value of the link length. In another embodiment, the insertion loss L can be calculated in software based on the new value of the link length. E and reflectivity R E The completion of the splicing process may be detected by the determined value of and capture and / or OTDR measurements may optionally be performed after such determination.

[0175] Optionally, when the capture process is complete, the OTDR device can be restored to return to continuous monitoring at the previous splice location. The user can move on to the next fiber and wait for the splice to be completed without further interaction with the unit.

[0176] Example of OTDR device architecture

[0177] Figure 8 1 is a block diagram of an OTDR device 1000 that can implement the OTDR method of FIG. 1. The OTDR device 1000 may include a digital device, which, in terms of hardware architecture, generally includes a processor 1002, an input / output (I / O) interface 1004, an optional radio device 1006, a data storage device 1008, a memory 1010, and an optical test device including an OTDR acquisition device 1018. It should be understood by those skilled in the art that Figure 8 The OTDR device 1000 is depicted in a simplified manner, and actual implementations may include additional components and appropriately configured processing logic to support known or conventional operating features not described in detail herein. The local interface 1012 interconnects the main components. The local interface 1012 may be, for example, but not limited to, one or more buses or other wired or wireless connections, as known in the art. The local interface 1012 may have additional elements omitted for simplicity such as controllers, buffers (caches), drivers, repeaters, and receivers, among others, to enable communication. In addition, the local interface 1012 may include address, control, and / or data connections to enable appropriate communication between the aforementioned components.

[0178] The processor 1002 is a hardware device for executing software instructions. The processor 1002 may include one or more processors, including a central processing unit (CPU), an auxiliary processor, or any device generally used to execute software instructions. When the OTDR device 1000 is in operation, the processor 1002 is configured to execute software stored in the memory 1010 to transfer data to and from the memory 1010 and generally control the operation of the OTDR device 1000 according to the software instructions. In one embodiment, the processor 1002 may include an optimized mobile processor, such as one optimized for power consumption and mobile applications. The I / O interface 1004 may be used to receive user input from the system output and / or to provide system output. The user input may be provided via, for example, a keyboard, a touch screen, a scroll ball, a scroll bar, a button, a barcode scanner, etc. The system output may be provided via a display device such as a liquid crystal display (LCD), a touch screen, via one or more LEDs or a group of LEDs, or via one or more buzzers or pagers, etc. The I / O interface 1004 may be used to display a graphical user interface (GUI) that enables a user to interact with the OTDR device 1000 .

[0179] Radio 1006, if included, may enable wireless communication with an external access device or network. Radio 1006 may support any number of suitable wireless data communication protocols, technologies, or methods, including, but not limited to: RF; IrDA (infrared); Bluetooth; ZigBee (and other variants of the IEEE 802.15 protocol); IEEE 802.11 (any variant); IEEE 802.16 (WiMAX or any other variant); direct sequence spread spectrum; frequency hopping spread spectrum; long term evolution (LTE); cellular / wireless / cordless telecommunication protocols (e.g., 3G / 4G, etc.); NarrowBand Internet of Things (NB-IoT); long term evolution machine type communications (LTE-M); magnetic induction; satellite data communication protocols; and any other protocols for wireless communication. Data storage 1008 may be used to store data, such as OTDR traces and OTDR measurement data files. The data storage device 1008 may include any of the following: volatile memory elements (e.g., random access memory (RAM, such as DRAM, SRAM, SDRAM, etc.)), non-volatile memory elements (e.g., ROM, hard drive, magnetic tape, CDROM, etc.), and combinations thereof. In addition, the data storage device 1008 may incorporate electronic, magnetic, optical, and / or other types of storage media.

[0180] The memory 1010 may include any of the following: volatile memory elements (e.g., random access memory (RAM, such as DRAM, SRAM, SDRAM, etc.)), non-volatile memory elements (e.g., ROM, hard disk drives, etc.), and combinations thereof. In addition, the memory 1010 may incorporate electronic, magnetic, optical, and / or other types of storage media. Note that the memory 1010 may have a distributed architecture in which components are located remotely from each other but accessible by the processor 1002. The software in the memory 1010 may include one or more computer programs, each of which includes an ordered list of executable instructions for implementing logical functions. Figure 8 In the example of , the software in the memory 1010 includes a suitable operating system (O / S) 1014 and a computer program 1016. The operating system 1014 basically controls the execution of other computer programs and provides scheduling, input and output control, file and data management, memory management, and communication control and related services. The program 1016 may include various applications, plug-ins, etc., which are configured to provide end-user functions through the OTDR device 1000. For example, the exemplary program 1016 may include: a web browser to connect to a server for transmitting OTDR measurement data files; a dedicated OTDR application software, which is configured to determine OTDR acquisition through the OTDR acquisition device 1018, set OTDR acquisition parameters, analyze the OTDR trace obtained by the OTDR acquisition device 1018, and display a GUI related to the OTDR device 1000. For example, the dedicated OTDR application and / or program 1016 may implement: an OTDR analysis module 114 configured to analyze acquired OTDR traces to characterize the optical fiber link under test and generate an OTDR measurement data file; and an event investigation module 146 for determining values ​​of one or more OTDR acquisition parameters for one or more event-specific OTDR acquisitions to be performed on the optical fiber link.

[0181] It should be noted that in some embodiments, the I / O interface 1004 may be provided via a physically different mobile device (not shown), such as a handheld computer, a smart phone, a tablet computer, a laptop computer, a wearable computer, etc., which is communicatively coupled to the OTDR device 1000, for example, via the radio device 106. In such a case, at least some of the programs 1016 may be located in the memory of such a mobile device for execution by a processor of the physically different device. At that time, the mobile device may also include a radio device and be used to transmit the OTDR measurement data file to a remote test application resident, for example, on a server.

[0182] It should be noted that Figure 8The OTDR apparatus shown in is intended to be an illustrative example only. Many types of computer systems are available and can be used to implement an OTDR apparatus.

[0183] Example of OTDR acquisition unit architecture

[0184] Fig. 9 is a block diagram of an implementation scheme of an OTDR acquisition device 1050. The OTDR acquisition device 1050 may be implemented Figure 8 The OTDR acquisition device 1018 of the OTDR device 1000.

[0185] The OTDR acquisition device 1050 is connectable to the optical fiber link under test via the output interface 1064 for performing OTDR acquisition on the optical fiber link. The OTDR acquisition device 1050 includes conventional optical hardware and electronic devices known in the art for performing OTDR acquisition on an optical fiber link.

[0186] The OTDR acquisition device 1050 includes a light generating component 1054 , a detection component 1056 , a directional coupler 1058 , as well as a controller 1070 and a data storage device 1072 .

[0187] The optical generation component 1054 is implemented by a laser source 1060 driven by a pulse generator 1062 to generate an OTDR test signal including a test optical pulse with desired characteristics. As known in the art, the optical generation component 1054 is adapted to generate a test optical pulse with a pulse width, a repetition period and an optical power that varies by appropriately controlling the pattern produced by the pulse generator 1062. Those skilled in the art will appreciate that it may be useful or required by application to perform OTDR measurements at various wavelengths. For this purpose, in some embodiments, the optical generation component 1054 is adapted to generate a test optical pulse with a wavelength that varies by adopting, for example, a tunable laser source 1060. It will be appreciated that the optical generation component 1054 can combine both pulse width control capability and wavelength control capability. Of course, different and / or additional components, such as modulators, lenses, mirrors, optical filters, wavelength selectors, etc., may be provided in the optical generation component.

[0188] The light generating assembly 1054 is coupled to the output interface 1064 of the OTDR acquisition device 1050 through a directional coupler 1058 having three or more ports, such as a circulator. The first port is connected to the light generating assembly 1054 to receive the test light pulse therefrom. The second port is connected to the output interface 1064. The third port is connected to the detection assembly 1056. The connection allows the test light pulse generated by the light generating assembly 1054 to be coupled to the output interface 1064, and allows the return light signal generated by backscattering and reflection along the optical fiber link 110 to be coupled to the detection assembly 1056.

[0189] The detection component 1056 includes: a photodetector 1066, such as a photodiode, an avalanche photodiode or any other suitable photodetector, which detects the return optical signal corresponding to each test optical pulse; and an analog-to-digital converter 1068, which is used to convert an electrical signal proportional to the detected return optical signal from analog to digital to allow data storage and processing. It will be understood that the detected return optical signal can of course be amplified, filtered or otherwise processed before analog-to-digital conversion. The power level of the return optical signal as a function of time - which is obtained from the above detection and conversion - is called an acquisition of the OTDR track. Those skilled in the art will readily understand that in the context of OTDR methods and systems, each optical acquisition generally involves propagating a large number of substantially identical optical pulses in the optical fiber link and averaging the results to improve the signal-to-noise ratio (SNR). In this case, the result obtained by averaging is referred to as the OTDR track in this article.

[0190] Of course, the OTDR acquisition device 1050 can also be used to perform multiple acquisitions with varying pulse widths to obtain multi-pulse width OTDR measurements.

[0191] The OTDR acquisition device 1050, and more specifically, the light generating assembly 1054, is controlled by a controller 1070. The controller 1070 is a hardware logic device. It may include one or more field programmable gate arrays (FPGAs); one or more application specific integrated circuits (ASICs) or one or more processors configured with a logic state machine or stored program instructions. When the OTDR acquisition device 1050 is in operation, the controller 1070 is configured to control the OTDR measurement process. The controller 1070 controls the parameters of the light generating assembly 1054 according to the OTDR acquisition parameters provided by the operator of the OTDR software or otherwise determined by the program 1016.

[0192] The data storage device 1072 can be used to accumulate the raw data received from the detection component 1056, as well as the intermediate average results and the resulting OTDR traces. The data storage device 908 can include any of a volatile memory element (e.g., a random access memory (RAM, such as DRAM, SRAM, SDRAM, etc.)), etc., and it can be embedded in the controller 1070 or different.

[0193] The OTDR traces acquired by the OTDR acquisition device 1050 may be received and analyzed by one or more of the computer programs 1016 or 816 and / or stored in the data storage device 1008 for further processing.

[0194] It should be noted that Fig. 9 The architecture of the OTDR acquisition device 1050 shown in is intended to be an illustrative example only. Many types of optical and electronic components are available and can be used to implement an OTDR acquisition device.

[0195] It will be understood that some embodiments described herein may include one or more general or special purpose processors ("processor(s)"), such as a microprocessor; a central processing unit (CPU); a digital signal processor (DSP); a custom processor, such as a network processor (NP) or network processing unit (NPU), a graphics processing unit (GPU), etc.; a field programmable gate array (FPGA); etc., and unique stored program instructions (including software and firmware) for controlling it to implement some, most or all of the functions of the methods and / or systems described herein in combination with certain non-processor circuits. Alternatively, some or all of the functions may be implemented by a state machine without stored program instructions, or in one or more application specific integrated circuits (ASICs), where each or some combination of certain functions is implemented as custom logic or circuits. Of course, combinations of the foregoing methods may be used. For some embodiments described herein, the corresponding devices in hardware and optionally with software, firmware and a combination thereof may be referred to as: "circuitry, which is configured or adapted to" perform a set of operations, steps, methods, processes, algorithms, functions, techniques, etc. as described herein for the various embodiments on digital and / or analog signals; "logic, which is configured or adapted to" perform a set of operations, steps, methods, processes, algorithms, functions, techniques, etc. as described herein for the various embodiments on digital and / or analog signals; and so on.

[0196] In addition, some embodiments may include a non-transitory computer-readable storage medium having computer-readable code stored thereon for programming a computer, server, facility, device, processor, circuit, etc., each of which may include a processor to perform functions as described and claimed herein. Examples of such computer-readable storage media include, but are not limited to, hard disks, optical storage devices, magnetic storage devices, ROM (read-only memory), PROM (programmable read-only memory), EPROM (erasable programmable read-only memory), EEPROM (electrically erasable programmable read-only memory), flash memory, etc. When stored in a non-transitory computer-readable medium, software may include instructions executable by a processor or device (e.g., any type of programmable circuit or logic) that, in response to such execution, cause the processor or device to perform a set of operations, steps, methods, processes, algorithms, functions, techniques, etc. as described herein for various embodiments.

[0197] According to one aspect, there is provided an OTDR method for characterizing an optical fiber link, the OTDR method comprising:

[0198] performing at least one first OTDR acquisition on the optical fiber link, wherein each OTDR acquisition is performed by: propagating a test signal corresponding to a first pulse width in the optical fiber link to be tested, and detecting corresponding return light from the optical fiber link to obtain an OTDR trace representing backscattered and reflected light as a function of distance in the optical fiber link;

[0199] identifying, based on the at least one first OTDR acquisition, one or more events along the optical fiber link and estimating a value of at least one characteristic associated with each of the one or more events;

[0200] determining values ​​of one or more OTDR acquisition parameters based at least on characteristics associated with a target event in the events, the OTDR acquisition parameters including a second pulse width different from the first pulse width;

[0201] A second OTDR acquisition is performed on the optical fiber link using the determined OTDR acquisition parameters.

[0202] In some embodiments, the method further comprises deriving, based on at least the second OTDR acquisition, an updated value of at least one characteristic associated with the event or a combined event associated with the event.

[0203] In some embodiments, the method further includes comparing an estimated value of at least one characteristic to an evaluation criterion, wherein the estimated value of at least one characteristic associated with the target event does not satisfy the evaluation criterion.

[0204] In some embodiments, the method further includes deriving, based on at least the second OTDR acquisition, a value of at least one characteristic of a merged event included in the target event.

[0205] In some embodiments, the method further includes obtaining an updated value of at least one characteristic associated with the target event based on at least the second OTDR acquisition.

[0206] In some embodiments, only if the estimated value of at least one characteristic associated with at least one of the events does not meet evaluation criteria, the steps of a) determining values ​​of one or more OTDR acquisition parameters, and b) performing at least a second OTDR acquisition are performed.

[0207] In some embodiments, a plurality of events are identified along the optical fiber link based on the first OTDR acquisition, and wherein the values ​​of one or more OTDR acquisition parameters are determined based on at least one characteristic associated with the target event among the plurality of events.

[0208] In some embodiments, the OTDR acquisition parameters include one or more of an OTDR test signal pulse width, an OTDR signal pulse repetition rate, and an OTDR acquisition time.

[0209] In some embodiments, the characteristic associated with the target event includes at least one of insertion loss and cumulative loss prior to the target event.

[0210] In some embodiments, the target event comprises a far end of the optical fiber link to be tested, and wherein OTDR acquisitions performed using the determined OTDR acquisition parameters are repeated in a continuous manner; and for each repeated OTDR acquisition, a value of at least one characteristic associated with the target event is estimated and displayed.

[0211] According to another aspect, there is provided a computer program comprising instructions which, when executed by a processor, cause the processor to perform any one of the methods described herein.

[0212] According to yet another aspect, there is provided an OTDR device for characterizing an optical fiber link, the OTDR device comprising:

[0213] an OTDR acquisition device, the OTDR acquisition device being connectable to an end of the optical fiber link for performing one or more OTDR acquisitions on the optical fiber link, wherein each OTDR acquisition is performed by: propagating a test signal corresponding to a first pulse width in the optical fiber link to be tested, and detecting a corresponding return optical signal from the optical fiber link to obtain an OTDR trace representing backscattered and reflected light as a function of distance in the optical fiber link; and

[0214] A processing unit, the processing unit receiving the OTDR trace and comprising:

[0215] an analysis module configured to identify events along the optical fiber link based on at least the OTDR trace, and to estimate a value of at least one characteristic associated with the event; and

[0216] An event investigation module is configured to determine values ​​of one or more OTDR acquisition parameters for at least a second OTDR acquisition to be performed on the optical fiber link based at least on a characteristic associated with the event, the OTDR acquisition parameters including a second pulse width different from the first pulse width.

[0217] In some embodiments, the analysis module is further configured to compare an estimated value of at least one characteristic of the event with an evaluation criterion, wherein the estimated value of at least one characteristic associated with the target event does not meet the evaluation criterion.

[0218] In some embodiments, the analysis module is further configured to obtain a value of at least one characteristic of a merged event included in the target event based on at least the second OTDR acquisition.

[0219] In some embodiments, the analysis module is further configured to obtain an updated value of at least one characteristic associated with the target event based on at least the second OTDR acquisition.

[0220] In some embodiments, the OTDR acquisition parameters include one or more of an OTDR test signal pulse width, an OTDR signal pulse repetition rate, and an OTDR acquisition time.

[0221] In some embodiments, the characteristic associated with the event includes at least one of insertion loss and cumulative loss prior to the target event.

[0222] According to another aspect, there is provided a non-transitory computer-readable storage medium comprising instructions that, when executed, cause a processor to perform the following steps:

[0223] receiving at least one first OTDR acquisition performed on the optical fiber link to be tested, wherein each OTDR acquisition is performed by: propagating a test signal corresponding to a first pulse width in the optical fiber link to be tested, and detecting corresponding return light from the optical fiber link to be tested so as to obtain the OTDR trace representing backscattered and reflected light according to a distance in the optical fiber link to be tested;

[0224] a. based on the at least one first OTDR acquisition, identifying one or more events along the optical fiber link and estimating a value of at least one characteristic associated with each of the one or more events; and

[0225] b. Determining values ​​of one or more OTDR acquisition parameters based at least on characteristics associated with a target event among the events, the OTDR acquisition parameters including a second pulse width different from the first pulse width.

[0226] In some embodiments, the non-transitory computer-readable storage medium also includes instructions that, when executed, cause the processor to perform the following steps: comparing an estimated value of at least one characteristic with an evaluation criterion, wherein the estimated value of at least one characteristic associated with the target event does not meet the evaluation criterion, and the target event includes at least two merged events.

[0227] In some embodiments, the non-transitory computer-readable storage medium further includes instructions that, when executed, cause the processor to perform the following steps: obtaining an updated value of at least one characteristic associated with the target event or a merged event associated with the target event based on at least the second OTDR acquisition.

[0228] In some embodiments, only if the estimated value of at least one characteristic associated with at least one of the events does not meet evaluation criteria, the steps of a) determining values ​​of one or more OTDR acquisition parameters, and b) performing at least a second OTDR acquisition are performed.

[0229] According to another aspect, there is provided an OTDR method for characterizing an optical fiber link, the OTDR method comprising:

[0230] performing at least a first OTDR acquisition on the optical fiber link, wherein each OTDR acquisition is performed by: propagating a test signal corresponding to a first pulse width in the optical fiber link to be tested, and detecting a corresponding return optical signal from the optical fiber link to obtain an OTDR trace representing backscattered and reflected light as a function of distance in the optical fiber link;

[0231] identifying, based on said at least first OTDR acquisition, one or more events along said optical fiber link and estimating a value of at least one characteristic associated with each of said events;

[0232] If said estimated value of at least one characteristic associated with at least one of said events does not satisfy an evaluation criterion,

[0233] performing at least a second OTDR acquisition of the optical fiber link using a second pulse width different from the first pulse width; and

[0234] An updated value of the at least one characteristic is obtained based on the at least second OTDR acquisition.

[0235] According to another aspect, there is provided an OTDR method for characterizing an optical fiber link, the OTDR method comprising:

[0236] performing at least a first OTDR acquisition on the optical fiber link, wherein each OTDR acquisition is performed by: propagating a test signal corresponding to a first pulse width in the optical fiber link to be tested, and detecting a corresponding return optical signal from the optical fiber link to obtain an OTDR trace representing backscattered and reflected light as a function of distance in the optical fiber link;

[0237] identifying, based on at least said first OTDR acquisition, one or more events along said optical fiber link and estimating a value of at least one characteristic associated with each of said events;

[0238] comparing each estimated value to an evaluation criterion, wherein the estimated value of at least one characteristic associated with a target event in the events does not satisfy the evaluation criterion, the target event comprising at least two merged events;

[0239] determining values ​​of one or more OTDR acquisition parameters based on at least one characteristic associated with the target event, the OTDR acquisition parameters including a second pulse width different from the first pulse width;

[0240] performing at least a second OTDR acquisition of the optical fiber link using the determined OTDR acquisition parameters; and

[0241] Based on the at least second OTDR acquisition, an updated value of at least one characteristic of each of the combined events associated with the target event is obtained.

[0242] According to yet another aspect, there is provided an OTDR method for characterizing an optical fiber link, the OTDR method comprising:

[0243] performing at least a first OTDR acquisition on the optical fiber link, wherein each OTDR acquisition is performed by: propagating a test signal corresponding to a first pulse width in the optical fiber link to be tested, and detecting a corresponding return optical signal from the optical fiber link to obtain an OTDR trace representing backscattered and reflected light as a function of distance in the optical fiber link;

[0244] identifying an event along the optical fiber link and estimating a value of at least one characteristic associated with the event based on at least the first OTDR acquisition;

[0245] determining values ​​of one or more OTDR acquisition parameters based at least on a characteristic associated with the event, the OTDR acquisition parameters including a second pulse width different from the first pulse width; and

[0246] At least a second OTDR acquisition is performed on the optical fiber link using the determined OTDR acquisition parameters.

[0247] In some embodiments, the method further comprises, based on the at least second OTDR acquisition, obtaining an updated value of at least one characteristic associated with the event or a merged event associated with the event.

[0248] A plurality of events may be identified along the optical fiber link from the first OTDR acquisition, and the values ​​of one or more OTDR acquisition parameters may be determined based on at least one characteristic associated with a target event among the plurality of events.

[0249] In some embodiments, the dynamic range associated with the second OTDR acquisition does not allow reaching the end of the optical fiber link.

[0250] According to yet another aspect, there is provided a non-transitory computer-readable storage medium having a computer program stored thereon, wherein the computer program is operable to perform an OTDR method for characterizing an optical fiber link, and wherein the computer program comprises instructions for instructing one or more processors to perform the following steps:

[0251] receiving an OTDR trace from at least a first OTDR acquisition of the optical fiber link, wherein each OTDR acquisition is performed by: propagating a test signal corresponding to a first pulse width in the optical fiber link to be tested, and detecting a corresponding return optical signal from the optical fiber link to obtain an OTDR trace representing backscattered and reflected light as a function of distance in the optical fiber link;

[0252] identifying, based on at least the first OTDR acquisition, an event along the optical fiber link and estimating a value of at least one characteristic associated with the event;

[0253] Based at least on one characteristic associated with the event, values ​​of one or more OTDR acquisition parameters are determined for at least a second OTDR acquisition to be performed on the optical fiber link, the OTDR acquisition parameters including a second pulse width different from the first pulse width.

[0254] The above-described embodiments are intended to be exemplary only. Accordingly, the scope of the present invention is intended to be limited only by the following claims.

Claims

1. An optical time domain reflectometer (OTDR) method for characterizing an optical fiber link, the OTDR method comprising: performing at least one first OTDR acquisition on the optical fiber link, wherein each OTDR acquisition is performed by: propagating a test signal corresponding to a first pulse width in the optical fiber link to be tested, and detecting corresponding return light from the optical fiber link to obtain an OTDR trace representing backscattered and reflected light according to a distance in the optical fiber link; identifying, based on the at least one first OTDR acquisition, one or more events along the optical fiber link and estimating at least one of a value of insertion loss and a value of reflectivity associated with each of the one or more events; If it is determined that the estimated value of at least one of the insertion loss and the reflectivity associated with at least one of the events does not satisfy an evaluation criterion: determining one or more values ​​of one or more OTDR acquisition parameters, wherein the OTDR acquisition parameters include a second pulse width that is shorter than the first pulse width; A second OTDR acquisition is performed on the optical fiber link using the one or more determined OTDR acquisition parameters to reassess at least one of the events.

2. The method of claim 1, wherein the values ​​of one or more OTDR acquisition parameters are determined based at least on characteristics associated with a target event of the one or more events.

3. The method of claim 2, further comprising: Based on the second OTDR acquisition, a value of at least one characteristic of the combined event included in the target event is obtained.

4. The method of claim 2, further comprising: An updated value of at least one of the insertion loss and the reflectivity associated with the target event is obtained based on the second OTDR acquisition.

5. The method of any one of claims 2 to 4, wherein a plurality of said events are identified along said optical fiber link based on said first OTDR acquisition, and wherein said values ​​of one or more OTDR acquisition parameters are determined based on at least one characteristic associated with said target event selected from said plurality of events.

6. The method according to any one of claims 1 to 4, wherein the OTDR acquisition parameters include one or more of an OTDR test signal pulse width, an OTDR signal pulse repetition rate, and an OTDR acquisition time.

7. The method of any one of claims 2 to 4, wherein the characteristic associated with the target event includes at least one of insertion loss and cumulative loss prior to the target event.

8. The method of any one of claims 2 to 4, wherein the target event is generated by the far end of the optical fiber link to be tested, and wherein the OTDR acquisitions performed using the determined OTDR acquisition parameters are repeated in a continuous manner; for each repeated OTDR acquisition, the value of at least one characteristic associated with the target event is estimated and displayed.

9. An optical time domain reflectometer (OTDR) device for characterizing an optical fiber link, the OTDR device comprising: an OTDR acquisition device, the OTDR acquisition device being connectable to an end of the optical fiber link for performing one or more OTDR acquisitions on the optical fiber link, wherein each OTDR acquisition is performed by: propagating a test signal corresponding to a first pulse width in the optical fiber link to be tested, and detecting corresponding return light from the optical fiber link to obtain an OTDR trace representing backscattered and reflected light according to a distance in the optical fiber link; a processing unit, the processing unit receiving the OTDR trace and being configured to: identifying one or more events along the optical fiber link from at least one OTDR trace, and estimating at least one of a value of insertion loss and a value of reflectivity associated with each of the one or more events; If it is determined that the estimated value of at least one of the insertion loss and the reflectivity associated with at least one of the events does not satisfy an evaluation criterion: determining one or more values ​​of one or more OTDR acquisition parameters, wherein the OTDR acquisition parameters include a second pulse width shorter than the first pulse width, and The OTDR acquisition device is caused to initiate a second OTDR acquisition of the optical fiber link using the one or more determined OTDR acquisition parameters to reassess at least one of the events.

10. The OTDR apparatus of claim 9, wherein the processing unit is further configured to determine the value of one or more OTDR acquisition parameters based at least on characteristics associated with a target event.

11. The OTDR device of claim 10, wherein the processing unit is further configured to obtain a value of at least one characteristic of a merged event included in the target event based on at least the second OTDR acquisition.

12. The OTDR device of claim 10, wherein the processing unit is further configured to obtain an updated value of at least one of the insertion loss and the reflectivity associated with the target event based on at least the second OTDR acquisition.

13. A non-transitory computer-readable storage medium comprising instructions that, when executed, cause a processor to perform the following steps: receiving data obtained according to at least one first OTDR acquisition performed on the optical fiber link to be tested, wherein each OTDR acquisition is performed by: propagating a test signal corresponding to a first pulse width in the optical fiber link to be tested, and detecting corresponding return light from the optical fiber link to be tested so as to obtain an OTDR trace representing backscattered and reflected light according to a distance in the optical fiber link to be tested; identifying, based on the at least one first OTDR acquisition, one or more events along the optical fiber link based on at least one OTDR trace and estimating at least one of a value of insertion loss and a value of reflectivity associated with each of the one or more events; as well as If it is determined that the estimated value of at least one of the insertion loss and the reflectivity associated with at least one of the events does not satisfy an evaluation criterion: determining one or more values ​​of one or more OTDR acquisition parameters, wherein the OTDR acquisition parameters include a second pulse width shorter than the first pulse width, and Causing initiation of a second OTDR acquisition of the optical fiber link using the one or more determined OTDR acquisition parameters to reassess the at least one of the events.

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