Coherent optical measurement device, optical fiber path testing system and method

Abstract

The purpose of the present disclosure is to make it possible to test a long-distance optical fiber line and to detect the distance to a plurality of abnormal equipment.　The present disclosure is an optical line test system which: detects a distribution of loss locations in the longitudinal direction of an optical line by using a coherent light measuring device; applies vibrations to equipment disposed on the path of the optical line, detects vibration locations in the longitudinal direction of the optical line when the vibrations are applied, by using the coherent light measuring device; and identifies the loss locations on the basis of the detected loss locations and the vibration locations coinciding with each other.

Description

[Technical field]

[0001] The present disclosure relates to a system and method for testing an optical path. [Background technology]

[0002] An optical fiber line testing system has been proposed that detects abnormal points where loss or reflection occurs by measuring the distribution of backscattered light in optical fibers (see, for example, non-patent document 1).In addition, a technology for identifying the location of equipment using optical fiber vibration sensors has been proposed (see, for example, patent document 1).

[0003] By using the facility location identification principle of Patent Document 1, it is possible to measure the vibration of the communication optical fiber using an optical fiber vibration sensing device from a communication fiber aggregation building, and at the same time, by striking the manhole cover, it is possible to detect the striking vibration and its location, making it possible to confirm the presence of the communication optical fiber underground and to match the manhole location with the fiber route map without opening the manhole.

[0004] Various needs and the expansion of the scale of use require more flexible wired network configurations, which in turn requires the use of longer-distance wiring and more communication equipment, and there is a demand for more efficient maintenance and operation of these. In addition, wireless communication, such as 5G, is becoming increasingly important in society, and the wiring of its base stations is a wired network. In most cases, wireless base stations are installed via overhead wiring. In the case of base stations installed on the roof of a building, they reach via on-site wiring. Therefore, there is a need to strengthen the monitoring and fault isolation functions of all communication wiring facilities, including overhead wiring, overhead relays, and on-site wiring.

[0005] In the case of a long-distance optical fiber line, including an aerial optical fiber line, it may not be possible to measure up to the far end with the optical fiber line test described in Non-Patent Document 1. In such cases, the line test itself is a simple direct detection OTDR (Optical Time Domain Reflectometer), so there are problems with the signal-to-noise ratio being small and the measurement distance being relatively short.

[0006] In addition, if a large loss or reflection occurs, the test light becomes very weak at a distance from that point. In such a case, if a large loss or reflection occurs in two or more places, there is a problem that only one point can be detected.

[0007] Even if the distance to the abnormality is known, there is still a possibility of distance error, and there are many manholes, utility poles, and manhole closures near the site, so that abnormalities such as broken wires in both overhead and underground facilities cannot be detected by appearance alone. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2020-052030 A [Patent Document 2] JP 2017-026503 A [Patent Document 3] JP 2020-169904 A [Non-patent literature]

[0009] [Non-Patent Document 1] "2. Overview of Optical Test Module (OTM)", ANSL R&D Times, No. 33, 2003_06, https: / / www.ansl.ntt.co.jp / j / times / 033 / 02 / 02.html [Non-Patent Document 2] "1. Flood Detection Technology", ANSL R&D Times, No. 58, 2009_01, https: / / www.ansl.ntt.co.jp / j / times / 058 / 01 / 01.html Summary of the Invention [Problem to be solved by the invention]

[0010] The present disclosure aims to enable testing of long-distance optical fiber lines and detection of distances to multiple abnormal facilities. [Means for solving the problem]

[0011] In the present disclosure, a long-distance loss distribution is measured by time averaging a single measurement result of an optical fiber line using an OTDR device that performs coherent detection, and a vibration distribution is measured by arranging the results in a time series.

[0012] The optical fiber path testing system and method disclosed herein include: A distribution of loss locations in a longitudinal direction of the optical fiber line is detected using a coherent optical measurement device; Vibrating equipment disposed on the path of the optical fiber; detecting a vibration location in a longitudinal direction of the optical path when the vibration is applied using the coherent light measurement device; The loss location is identified based on whether the detected loss location and the vibration location coincide with each other.

[0013] The coherent detection device of the present disclosure comprises: A coherent OTDR that performs coherent detection, measuring a distribution of the loss locations by time-averaging a plurality of backscattered light waveforms obtained by a plurality of optical pulses; measuring the vibration location by arranging in time series a plurality of backscattered light waveforms obtained by a plurality of light pulses; The coincidence or non-coincidence of the loss location and the vibration location is determined. Effect of the Invention

[0014] According to the present disclosure, it is possible to test long-distance optical fiber lines and detect the distances to multiple abnormal facilities. [Brief description of the drawings]

[0015] [Figure 1] An example of the configuration of a coherent OTDR is shown below. [Diagram 2] 3 shows an example of a backscattered light waveform. [Diagram 3] An example of an optical line testing method according to this embodiment will be described. [Figure 4] An example of the optical path loss measurement result is shown. [Diagram 5] An example of a hitting position is shown. [Figure 6] An example of detecting vibration caused by hitting a manhole is shown below. [Figure 7] An example of a display on a coherent optical measurement device is shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below. These implementation examples are merely illustrative, and the present disclosure can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. Note that components with the same reference numerals in this specification and drawings are assumed to indicate the same components.

[0017] (Example 1) The optical fiber line testing system disclosed herein includes a coherent light measurement device capable of coherent detection at any point in the longitudinal direction of the optical fiber line. In this embodiment, as an example of the measurement technique, a coherent OTDR that performs coherent detection is used.

[0018] Figure 1 shows an example of the configuration of a coherent OTDR. Reference numeral 1 denotes a light source that emits coherent light. The light from light source 1 is split by optical coupler 2, and one of the two is modulated by modulator 3 to generate a frequency-modulated optical pulse, which is then amplified by amplifier 4. This amplified optical pulse is input to optical fiber 6 through circulator 5. Optical fiber 6 is the optical line to be tested, and may be referred to as the optical fiber under test (FUT).

[0019] The scattered light and reflected light from the optical fiber 6 return to the circulator 5, where they are combined with the other light branched by the optical coupler 2, and are coherently detected by the balance PD 8. The coherently detected signal is converted into digital data by the digitizing means 9, and subjected to numerical calculation processing by the computer 10. The control unit 7 controls the modulator 3 and the measurement timing. The control unit 7, digitizing means 9, computer 10, and display unit 11 can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network.

[0020] By using an OTDR that performs coherent detection, it is possible to obtain the backscattered light waveform as shown in Figure 2 for the number of incident optical pulses. Here, it is possible to increase the number of samples of the backscattered light waveform by having the modulator 3 frequency multiplex the frequency of the optical pulse. Furthermore, the coherent detection by the balanced PD 8 is heterodyne detection because the modulator 3 performs frequency modulation. Here, if the modulator 3 does not perform frequency modulation, it becomes homodyne detection. The coherent detection here may be homodyne detection that does not perform frequency modulation by such a modulator 3.

[0021] The backscattered light waveform is a time waveform, and when multiple backscattered light waveforms obtained by multiple optical pulses are averaged, a waveform obtained by a so-called coherent OTDR is obtained, enabling measurement with a high signal-to-noise ratio.

[0022] In addition, by arranging the backscattered light waveforms for each optical pulse before averaging by the chronological pulse number, it becomes possible to measure the time change of the scattered light at each scattering position, that is, vibration measurement. In the case of frequency multiplexing, the techniques of Patent Document 2 and Patent Document 3 can be used. For example, the frequency multiplexing averaging method described in Patent Document 3, which takes phase rotation into consideration, may be adopted.

[0023] With such an OTDR configuration that performs coherent detection, it is possible to measure long-distance loss distribution by averaging a single measurement result, and to measure vibration distribution by arranging the results in chronological order. In this disclosure, vibration is applied to equipment installed on the optical fiber 6, and the distance to the abnormal equipment can be detected by detecting the vibration. Here, in this disclosure, the equipment to be struck is any equipment installed on the optical fiber 6, and examples of this include at least one of a closure, a utility pole, and a manhole.

[0024] (Example 2) In this embodiment, an optical line testing method executed by the optical line testing system will be described. In this embodiment, as an example of matching on-site equipment, an example of bending loss due to water immersion in a water immersion detection module will be described.

[0025] An example of the optical line testing method of this embodiment is shown in Fig. 3. The optical line testing method of this embodiment includes steps S11 to S14. Step S11: Bending loss due to submersion of the optical fiber 6 is detected by optical path loss measurement using coherent detection. FIG. 4 shows an example of an optical path loss measurement result. The optical path loss measurement result is displayed on the display unit 11 as a distribution of loss locations in the longitudinal direction of the optical fiber 6. For example, when bending loss occurs at distances D1 and D2 from the coherent light measurement device, the backscattered light power decreases at distances D1 and D2. Here, since coherent detection is used in the present disclosure, the measurement distance range is expanded and losses at multiple points can be measured.

[0026] Step S12: Dispatch a worker to the area of ​​distances D1 and D2 where bending losses occurred, and strike the covers of manholes M1 and M2 in the surrounding area. For example, as shown in FIG. 5, strike the manhole M1 located in the area of ​​distance D1 from the coherent light measurement device.

[0027] Step S13: Using the coherent light measurement device measured in step S11, the vibration of the optical fiber 6 is measured by observing the change in waveform over time, and the position of the struck manhole is identified. For example, the vibration at distance D1 is detected by measuring the change in waveform of the backscattered light at distance D1 over time using the backscattered light waveform before averaging.

[0028] 6 shows an example of detection of vibration caused by striking a manhole. When optical fiber 6 is laid under a manhole, vibration is detected at the position of the manhole. In this embodiment, since the vibration is detected by a coherent light measurement device placed at the same position as in step S11, the position of the manhole coincides with the distance in the longitudinal direction of optical fiber 6 from the coherent light measurement device to the manhole in step S11. This makes it possible to detect the location of vibration in the longitudinal direction of optical fiber 6.

[0029] Step S14: The waveform measured in step S11 and the waveform measured in step S13 are simultaneously displayed on the display unit 11, and the loss location and the vibration location are compared. If they match, it is determined that the manhole is flooded. For example, if the vibration location detected in step S13 matches the distance D1 where the loss occurred, it is determined that the manhole M1 that was struck is a flooded manhole where bending loss has occurred, and this is displayed on the display unit 11.

[0030] FIG. 7 shows an example of the display on the coherent light measurement device. Since the coherent light measurement device used in the measurement in step S11 is used, it is possible to measure in the same measurement distance range. Therefore, as shown in FIG. 7, the vibration magnitude and backscattered light power are displayed on the display unit 11 in the same measurement distance range. At this time, the worker may record the time when the worker struck and display it on the display unit 11. This allows for a more accurate determination by matching the backscattered light waveform with the vibration detection time.

[0031] As described above, the system and method of the present disclosure enable range expansion through coherent measurement while simultaneously enabling loss measurement and vibration measurement in the same device. In this embodiment, step S13 is executed after step S11, but these may be measured simultaneously. Also, in step S13, the computer 10 may automatically detect waveform changes due to vibration from the digital data, and in step S14, the computer 10 may automatically compare the vibration location with the loss location. Also, the display of the vibration detection result and the backscattered light waveform may be overlapped as shown in Figure 7, or may be side-by-side. Also, the output result may be the waveform shown in Figure 7, or just the coincidence or mismatch of the impact position.

[0032] Furthermore, the coherent optical measurement device may be equipped with a communication function, so that information can be sent to the on-site worker who performed the strike and can be checked on any terminal such as a smartphone or tablet at the site. The information may be, for example, the results of detection of loss locations, the results of detection of vibration locations, and the results of matching the loss locations with the vibration locations. Furthermore, the coherent optical measurement device may operate according to instructions from the terminal of the on-site worker. This allows the worker who performs the strike in step S12 to operate steps S11, S13, and S14 remotely, so that all can be performed simultaneously on-site.

[0033] (Example 3) In this embodiment, a case where a connection loss, a breakage loss, and abnormal reflection at a connection portion of an optical fiber 6 are detected will be described. Steps S11 and S13 are the same as those in the second embodiment. In step S12, a utility pole or a manhole is struck. In step S14, the loss location detected in step S11 is compared with the vibration location detected in step S13 to identify the loss facility (the utility pole or manhole having a closure with an abnormal connection).

[0034] (Example 4) When the equipment of the second embodiment is a closure in an underground manhole, there may be a plurality of closures under the manhole. In that case, each closure is struck in step S12. As a result, vibration is detected for each closure in step S13, and the closure in which vibration is detected is matched with the optical fiber in which loss is detected in step S14. This makes it possible to identify the closure with loss.

[0035] (Overview and key points of this technology) The disclosed optical line testing system uses coherent measurement technology to expand the dynamic range of measurements, enable longer measurement distances, and low-power scattered light reception that can tolerate multiple anomalies. Dynamic strain (vibration) sensing using coherent detection detects vibration points on the optical line caused by external impacts on equipment placed on the optical line path, and compares the distance to the anomaly point in the optical test with the on-site equipment where the impact occurred. Vibration sensing that measures phase using coherent detection improves sensitivity, making it possible to detect vibrations even in the presence of multiple losses or reflections. The above two measurements can be realized using the same hardware, and can also be performed simultaneously by performing one measurement and two processes on the results. By performing the above two measurements with one device and displaying them on the same screen, it is possible to simultaneously identify multiple abnormal locations and on-site work equipment. The information that can be confirmed can be either the waveform itself or the matching results. A configuration can be adopted in which the coherent light measurement device can be controlled from the site where the impact occurred. For example, the coherent light measurement device detects the distribution of loss points in the longitudinal direction of the optical fiber 6 and detects vibration points in the longitudinal direction of the optical fiber 6 according to instructions from a set terminal.

[0036] (effect) -The measurement dynamic range is expanded. This makes it possible to test long-distance optical fiber lines. It is also possible to detect the distance to multiple abnormal facilities. Capable of detecting multiple fault locations for all types of faults, including breakage, bending, reflection, and bending due to water immersion. - Impact detection can be performed on manholes, utility poles, closures inside manholes, etc., simplifying on-site equipment fault checking. By tapping on a wall, it is possible to connect to wiring within a customer's home or other facility. The above measurements can be performed using a single measuring device and judged using a single output. The above effects will enable a significant reduction in operations such as detecting and repairing abnormal equipment in optical fiber lines. The results of the match can be sent to a set device such as a smartphone or tablet and displayed, making it possible to check them at the site where the strike occurred. [Industrial Applicability]

[0037] The present disclosure can be applied to the information and communications industry. [Explanation of symbols]

[0038] 1:Light source 2: Optical coupler 3: Modulator 4: Amplifier 5: Circulator 6: Optical fiber 7: Control unit 8: Balanced PD 9: Quantification methods 10: Calculator 11: Display section

Claims

1. A method of vibrating equipment arranged on the path of an optical fiber line, A vibration location in the longitudinal direction of the optical fiber path when the vibration is applied is measured by using a coherent light measurement device that is a coherent OTDR (Optical Time Domain Reflectometer) that performs coherent detection to coherently detect a plurality of backscattered light waveforms obtained from a plurality of optical pulses, and arranging the backscattered light waveforms by chronological pulse numbers to detect a time change in the scattered light at each scattering position. measuring a distribution of loss points in the longitudinal direction of the optical line by time-averaging the plurality of backscattered light waveforms using the coherent light measurement device in the same measurement distance range as the vibration points; identifying the loss location based on the fact that the loss location and the vibration location measured in the same measurement distance range coincide with each other; Optical fiber line testing system.

2. The facility is at least one of a closure, a utility pole, or a manhole; 2. The optical line testing system according to claim 1.

3. The coherent light measurement device transmits at least one of the detection results of the loss location and the vibration location or the identification result to a set terminal.

3. The optical line testing system according to claim 1 or 2.

4. The coherent light measurement device performs at least one of detection of a distribution of loss points in the longitudinal direction of the optical fiber path and detection of vibration points in the longitudinal direction of the optical fiber path in accordance with an instruction from a set terminal.

4. The optical line testing system according to claim 3.

5. A coherent OTDR that performs coherent detection, A phase is measured by coherently detecting a plurality of backscattered light waveforms obtained from a plurality of optical pulses, and the phase is then arranged by a chronological pulse number to detect a time change in the scattered light at each scattering position, thereby measuring the vibration location; measuring a distribution of loss locations in the same measurement distance range as the vibration location by time-averaging the plurality of backscattered light waveforms; determining whether the loss location and the vibration location coincide or not in the same measurement distance range; Coherent optical measurement equipment.

6. A method of vibrating equipment arranged on the path of an optical fiber line, A vibration location in the longitudinal direction of the optical fiber path when the vibration is applied is measured by using a coherent light measurement device that is a coherent OTDR (Optical Time Domain Reflectometer) that performs coherent detection to coherently detect a plurality of backscattered light waveforms obtained from a plurality of optical pulses, and arranging the backscattered light waveforms by chronological pulse numbers to detect a time change in the scattered light at each scattering position. measuring a distribution of loss points in the longitudinal direction of the optical line by time-averaging the plurality of backscattered light waveforms using the coherent light measurement device in the same measurement distance range as the vibration points; identifying the loss location based on the fact that the loss location and the vibration location measured in the same measurement distance range coincide with each other; Optical line test methods.

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