Optical cable monitoring device and optical cable monitoring method

Abstract

An optical cable monitoring device and an optical cable monitoring method are provided that can pinpoint an abnormality in an optical cable. [Solution] An optical cable monitoring device characterized by having a first acquisition unit that acquires the monitored section of the optical cable, a heating unit that heats the monitored section of the optical cable, a detection unit that detects the temperature of the monitored section of the optical cable, and a second acquisition unit that acquires abnormal locations in the monitored section of the optical cable based on the temperature detection results of the monitored section of the optical cable.

Description

[Technical Field]

[0001] The present invention relates to an optical cable monitoring device and an optical cable monitoring method. [Background technology]

[0002] Patent Document 1 describes a method for detecting an abnormality in an optical fiber cable, in which infrared light is incident from one end of the optical fiber cable into an optical fiber housed in the optical fiber cable and infrared light leaking from an abnormality in the optical fiber is detected. In this method, the optical fiber cable is passed through a cylindrical body with an infrared light detection element attached to the inner surface, and the cylindrical body is scanned relatively in the longitudinal direction of the optical fiber cable to detect infrared light leaking from an abnormality in the optical fiber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-140712 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the method of detecting an abnormal portion in an optical fiber cable disclosed in Patent Document 1 cannot pinpoint an abnormal portion in the optical fiber cable.

[0005] The present invention has been made in consideration of the above-mentioned problem, and aims to provide an optical cable monitoring device and an optical cable monitoring method that can pinpoint abnormal locations in an optical cable. [Means for solving the problem]

[0006] The optical cable monitoring device of this embodiment includes a first acquisition unit that acquires a monitored section of an optical cable, a heating unit that heats the monitored section of the optical cable, a detection unit that detects the temperature of the monitored section of the optical cable, and a second acquisition unit that acquires an abnormality location in the monitored section of the optical cable based on a temperature detection result of the monitored section of the optical cable. the detection unit waits for a temperature rise saturation time required for heating the monitored section of the optical cable, and then detects the temperature of the monitored section of the optical cable. It is characterized by: The optical cable monitoring device of this embodiment has a first acquisition unit that acquires the monitored section of the optical cable, a heating unit that heats the monitored section of the optical cable, a detection unit that detects the temperature of the monitored section of the optical cable, and a second acquisition unit that acquires abnormal locations in the monitored section of the optical cable based on the temperature detection results of the monitored section of the optical cable, wherein the detection unit detects the pre-heating temperature before heating the monitored section of the optical cable and the post-heating temperature after heating the monitored section of the optical cable, and the second acquisition unit acquires abnormal locations in the monitored section of the optical cable based on the differential temperature between the pre-heating temperature and the post-heating temperature. The optical cable monitoring device of this embodiment comprises a first acquisition unit that acquires the monitored section of the optical cable, a heating unit that heats the monitored section of the optical cable, a detection unit that detects the temperature of the monitored section of the optical cable, and a second acquisition unit that acquires abnormal locations in the monitored section of the optical cable based on the temperature detection results of the monitored section of the optical cable, wherein the optical cable comprises an optical fiber bundle and an outer sheath that covers the optical fiber bundle, the heating unit comprises a laser light irradiation unit that irradiates heating laser light from one end side of the optical cable, and the laser light irradiation unit varies the intensity of the heating laser light depending on the color of the outer sheath of the optical cable.

[0007] The optical cable monitoring method of this embodiment includes the steps of: acquiring a monitored section of an optical cable; heating the monitored section of the optical cable; detecting the temperature of the monitored section of the optical cable; and acquiring an abnormality location in the monitored section of the optical cable based on the temperature detection result of the monitored section of the optical cable. and in the detecting step, after waiting for a temperature rise saturation time required for heating of the monitored section of the optical cable, the temperature of the monitored section of the optical cable is detected. It is characterized by: The optical cable monitoring method of this embodiment includes the steps of acquiring a monitored section of an optical cable, heating the monitored section of the optical cable, detecting the temperature of the monitored section of the optical cable, and acquiring abnormal points in the monitored section of the optical cable based on the temperature detection results of the monitored section of the optical cable, wherein the detecting step detects a pre-heating temperature before heating the monitored section of the optical cable and a post-heating temperature after heating the monitored section of the optical cable, and the acquiring step acquires abnormal points in the monitored section of the optical cable based on the differential temperature between the pre-heating temperature and the post-heating temperature. The optical cable monitoring method of this embodiment includes the steps of acquiring a monitored section of an optical cable, heating the monitored section of the optical cable, detecting the temperature of the monitored section of the optical cable, and acquiring abnormal locations in the monitored section of the optical cable based on the temperature detection results of the monitored section of the optical cable, wherein the optical cable has an optical fiber bundle and an outer sheath covering the optical fiber bundle, and the heating step includes a laser light irradiation step of irradiating heating laser light from one end side of the optical cable, and the laser light irradiation step varies the intensity of the heating laser light depending on the color of the outer sheath of the optical cable. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an optical cable monitoring device and an optical cable monitoring method that can pinpoint an abnormality in an optical cable. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of an FTTH system. [Figure 2] FIG. 1 is a diagram showing a cross-sectional structure of an optical cable. [Figure 3] 10A and 10B are diagrams illustrating the configuration of optical cables when the outer sheath color is white or black. [Figure 4] FIG. 1 is a diagram illustrating a schematic configuration of an optical cable monitoring device. [Figure 5] 10 is a diagram showing how a first acquisition unit acquires a monitoring target section of an optical cable. FIG. [Figure 6]10A and 10B are diagrams illustrating how a temperature detection unit detects the temperature of a monitored section of an optical cable. [Figure 7] 10 is a diagram illustrating temperature detection by a detection unit in a monitored section of an optical cable and acquisition of abnormal locations in the monitored section of an optical cable by a second acquisition unit. FIG. [Figure 8] 1 is a first flowchart showing each processing step of an optical cable monitoring method. [Figure 9] 10 is a second flowchart showing the processing steps of the optical cable monitoring method. DETAILED DESCRIPTION OF THE INVENTION

[0010] The optical cable monitoring device and the optical cable monitoring method of this embodiment will be described below. The optical cable monitoring device and the optical cable monitoring method of this embodiment are applied to, for example, optical line maintenance work and are used to identify abnormalities (fault locations, fault locations) in the optical line. Furthermore, the optical cable monitoring device and the optical cable monitoring method of this embodiment are used to identify abnormalities in an optical cable non-destructively, for example, by using a thermography camera.

[0011] <Conventional technical issues> Fiber-to-the-home (FTTH) communication services for homes using optical fiber are becoming widespread, and there is a demand for efficient maintenance of the communication equipment that supports FTTH services. Among communication equipment, optical fiber in aerial optical cables laid between utility poles is often damaged by strong winds or contact with trees, and when damage occurs, it is necessary to pinpoint the damaged area for repair.

[0012] One technique for identifying (estimating) the location of a fault in an optical cable in an FTTH service is to attach an OTDR (Optical Time Domain Reflectometer) to the terminal and transmit an optical pulse laser to measure the distance to the fault point, thereby identifying (estimating) the fault point. Alternatively, an optical closure (aerial installation closure) can be attached to the optical cable and the fault point can be identified (estimated) based on the optical power inside the optical closure. However, with either technique, it is difficult to pinpoint the location of an abnormality in the optical cable.

[0013] Furthermore, it is possible to identify (estimate) the location of an abnormality by irradiating an optical fiber cable with visible light and observing the light leaking from the optical fiber cable. However, this method is only applicable when the optical fiber cable's outer sheath is damaged, exposing the optical fiber bundle. For example, if the optical fiber bundle inside the optical cable is damaged without damaging the optical fiber cable's outer sheath due to cable bending or lateral pressure, almost no light leaking from the optical cable is observed, making it impossible to identify (estimate) the location of the abnormality. As a result, the outer sheath must be stripped from the location where an abnormality (fault) is suspected to exist to check for optical continuity. Furthermore, if no abnormality (fault) is found in the stripped outer sheath, the optical fiber bundle must be protected from environmental factors such as rain and wind when the optical cable is repaired.

[0014] <Basic technical concept of this embodiment> The present inventors have recognized the above-mentioned problems as important technical challenges and have come up with the idea of ​​an optical cable monitoring device and an optical cable monitoring method that can pinpoint abnormal locations in an optical cable in a non-destructive and easy manner. That is, with the optical cable monitoring technology of this embodiment, even if the outer sheath of the optical cable is not damaged but the optical fiber bundle inside the optical cable is damaged and almost no leaked light from the optical cable is observed, it is possible to pinpoint abnormal locations in the optical cable by observing the temperature rise caused by the leaked light from the optical fiber bundle.

[0015] More specifically, in this embodiment, the first acquisition unit (in the first acquisition step) acquires the monitored section of the optical cable, the heating unit (in the heating step) heats the monitored section of the optical cable, the detection unit (in the detection step) detects the temperature of the monitored section of the optical cable, and the second acquisition unit (in the second acquisition step) acquires abnormal locations in the monitored section of the optical cable based on the temperature detection results of the monitored section of the optical cable.

[0016] That is, the first acquisition unit (in the first acquisition step) acquires the section to be monitored from the entire section of the optical cable (between the terminal and the receiving station) (performs a primary screening to narrow down the section from the entire length), and the second acquisition unit (in the second acquisition step) acquires the abnormality location in the monitored section of the optical cable based on the temperature detection results (after heating or before and after heating) of the monitored section of the optical cable (performs a secondary screening to pinpoint the abnormality location). This makes it possible to pinpoint the abnormality location in the optical cable non-destructively and easily.

[0017] <Specific embodiment> 1 is a diagram showing a schematic configuration of an FTTH (Fiber To The Home) system 100. The FTTH system 100 includes a terminal 200, an access point 300, and an optical cable 400 connecting the terminal 200 and the access point 300.

[0018] The terminal 200 is an optical outlet on the user side installed at an installation location such as a detached house, an apartment building, or an office. The accommodation station 300 is a communication station of an optical line on the provider side that supplies communication light to the terminal 200 via an optical cable 400. In FIG. 1, each terminal 200 and the accommodation station 300 are depicted as being connected via an optical cable 400, but in reality, multiple (many) terminals 200 are connected to one accommodation station 300 via the optical cable 400. Furthermore, in FIG. 1, three relay units 500A, 500B, and 500C are depicted as examples at intermediate positions between the terminal 200 and the accommodation station 300 connected by the optical cable 400.

[0019] In FIG. 1, the sections between the terminal 200 and the repeater unit 500A, between the repeater unit 500A and the repeater unit 500B, between the repeater unit 500B and the repeater unit 500C, and between the repeater unit 500C and the accommodating station 300 can each be the "monitored sections of the optical cable 400" acquired by the first acquisition unit 610 described later.

[0020] FIG. 2 is a diagram showing the cross-sectional structure of an optical cable 400. The optical cable 400 has a plurality of built-in optical fibers. As shown in FIG. 2, the optical cable 400 may be a spacer-type optical cable. In the example of FIG. 2, the optical cable 400 has a spacer 410 with a plurality of spiral slots 420 formed on its outer periphery, and a plurality of stacked optical fiber bundles (tape-shaped optical fibers) 430, each of which has a plurality of (e.g., four) optical fibers 430a arranged in parallel, are housed in each slot 420. A tension member 440 is provided at the central axis position of the spacer 410, and a water stop tape 450 and an outer jacket (sheath) 460 are sequentially provided around the periphery of the spacer 410. Note that the optical cable 400 is not limited to the spacer-type.

[0021] A part of the optical fiber 430a of the optical cable 400 includes a monitoring optical fiber 430b that is optically connected to an OTDR (Optical Time Domain Reflectometer) device and used to acquire (identify, measure, detect) a section to be monitored (a section estimated to be abnormal, a section estimated to be faulty). In the example of Fig. 2, the monitoring optical fiber 430b included in the optical fiber 430a of the optical cable 400 is depicted by being surrounded by a dashed circle. Note that the monitoring optical fiber 430b may also be used for normal communication purposes.

[0022] As described above, the optical cable 400 has the optical fiber bundle 430 and an outer jacket 460 that covers the optical fiber bundle 430. The color of the outer jacket 460 of the optical cable 400 may vary depending on various conditions such as the installation location and environment of the optical cable 400. The color of the outer jacket 460 of the optical cable 400 may be uniform along the longitudinal direction (extension direction) of the optical cable 400, or may vary depending on the position along the longitudinal direction (extension direction) of the optical cable 400.

[0023] 3A and 3B are diagrams depicting the configuration of optical cable 400 when outer cover 460 is white and black, respectively. Whether outer cover 460 is white or black, optical cable 400 has a common configuration in that various types of continuous light (e.g., light for communication, light for testing, and heating laser light, which will be described later) are incident thereon.

[0024] 3A, optical cable 400 having a white outer jacket 460 is commonly used indoors. In the case of optical cable 400 having a white outer jacket 460, if the optical fiber bundle 430 is damaged but the outer jacket 460 is not, a portion of the leaked light from the optical fiber bundle 430 is absorbed by the outer jacket 460 and the remaining portion is emitted from the outer jacket 460, so that only a portion of the energy of the leaked light is converted into heat. Therefore, the optical cable 400 has the characteristic that the temperature of the outer jacket 460 is unlikely to rise.

[0025] 3B, optical cables 400 having a black outer jacket 460 are often drop cables used outdoors, and black carbon is added to prevent deterioration of the outer jacket 460 due to ultraviolet rays. In the case of optical cables 400 having a black outer jacket 460, if the optical fiber bundle 430 is damaged but the outer jacket 460 is not, all of the leaked light from the optical fiber bundle 430 is absorbed by the outer jacket 460, and all of the energy of the leaked light is converted into heat. Therefore, the temperature of the outer jacket 460 of the optical cable 400 is likely to increase.

[0026] 4 is a diagram showing a schematic configuration of the optical cable monitoring device 600. The optical cable monitoring device 600 has a first acquisition unit 610, a heating unit 620, a detection unit 630, and a second acquisition unit 640.

[0027] The first acquisition unit 610 acquires (identifies, measures, detects) a monitoring target section (estimated abnormality section, estimated failure section) of the optical cable 400 at an intermediate position between the terminal 200 and the exchange 300. There is a degree of freedom in how the first acquisition unit 610 acquires the monitoring target section of the optical cable 400, and various design changes are possible, but for example, at least one of an OTDR device and an optical closure can be used.

[0028] FIG. 5 is a diagram showing how the first acquisition unit 610 acquires the monitoring target section of the optical cable 400. As shown in FIG. 5, an OTDR device 610A serving as the first acquisition unit 610 is attached to the end of the optical cable 400 on the terminal 200 side. The OTDR device 610A emits an optical pulse as monitoring light into the monitoring optical fiber 430b (see FIG. 2) of the optical cable 400 and measures the optical intensity of the return light (backscattered light and reflected light) from the monitoring optical fiber 430b. Based on the data on the optical intensity of the return light from the monitoring optical fiber 430b, the OTDR device 610A determines whether or not an abnormality-occurring section (a section where loss is abnormally high) exists in the longitudinal direction of the optical cable 400, and if so, calculates the distance of the abnormality-occurring section from the terminal 200. This distance information is acquired (identified, measured, detected) as the monitoring target section (an estimated abnormality section, an estimated fault section) of the optical cable 400 at an intermediate position between the terminal 200 and the accommodation station 300. Furthermore, an optical closure 610B serving as a first acquisition unit 610 is attached to the optical cable 400 near the repeater units 500A and 500B, making it possible to identify nearby connection points. Based on the optical power (optical continuity confirmation) within the optical closure 610B, a monitoring target section (estimated abnormality section, estimated failure section) of the optical cable 400 at an intermediate position between the terminal 200 and the accommodation station 300 is acquired (identified, measured, detected). In the example of Fig. 5, the section of the optical cable 400 between the terminal 200 and the repeater unit 500A is acquired as the monitoring target section.

[0029] The heating unit 620 heats the monitoring section of the optical cable 400 acquired by the first acquisition unit 610. The heating unit 620 has a laser light irradiation unit that irradiates a heating laser light from one end side of the optical cable 400. When the monitoring section is between the terminal 200 and the relay unit 500A as shown in FIG. 5, the laser light irradiation unit of the heating unit 620 irradiates the monitoring section of the optical cable 400 with a heating laser light from the side of the terminal 200 or the side of the relay unit 500A to which the optical closure 610B is attached.

[0030] The laser light irradiator may vary the intensity of the heating laser light depending on the color of the outer jacket 460 of the optical cable 400 .

[0031] As described above, in the case of a white cable, if the optical fiber bundle 430 is damaged but the outer jacket 460 is not damaged, a portion of the leaked light from the optical fiber bundle 430 is absorbed by the outer jacket 460, and the remaining portion is emitted from the outer jacket 460, so that the temperature of the outer jacket 460 of the optical cable 400 is unlikely to rise. On the other hand, in the case of a black cable, if the optical fiber bundle 430 is damaged but the outer jacket 460 is not damaged, all of the leaked light from the optical fiber bundle 430 is absorbed by the outer jacket 460, so that the temperature of the outer jacket 460 of the optical cable 400 is likely to rise.

[0032] Using the above characteristics, the laser light irradiating section of the heating section 620 may make the intensity of the heating laser light relatively strong (stronger than in the case of a black cable) when the outer jacket 460 of the optical cable 400 is white, and may make the intensity of the heating laser light relatively weak (weaker than in the case of a white cable) when the outer jacket 460 of the optical cable 400 is black. The laser light irradiating section of the heating section 620 may vary the characteristics of the heating laser light in accordance with other parameters such as the thickness of the outer jacket 460 of the optical cable 400 in addition to / instead of the color of the outer jacket 460 of the optical cable 400.

[0033] When heating the monitored section of the optical cable 400, the laser light irradiating section of the heating unit 620 may irradiate the heating laser light having characteristics different from the light used for communication and / or testing by the optical cable 400.

[0034] The power of the communication light between the terminal 200 and the accommodating station 300 is determined by a standard, and the power of the communication light is likely to be insufficient to heat (raise the temperature of) the monitored section of the optical cable 400. Therefore, the heating laser light irradiated by the laser light irradiating unit of the heating unit 620 may be set to a power greater than that of the communication light between the terminal 200 and the accommodating station 300.

[0035] Passive Optical Networks (PONs), an optical transmission standard used in FTTH, specify a test wavelength band, and optical filters are often installed to prevent light in the test wavelength band from entering communication equipment. In this case, even if high optical power is input in the test wavelength band, the communication equipment is not affected. However, depending on the optical line topology without the above-mentioned optical filter, it may be better to avoid an average optical input power of, for example, 0 dBm or more to prevent communication equipment failure. In such a case, if the optical cable 400 is a multi-core cable as shown in FIG. 2 and fiber damage occurs at the same location in multiple cores, the temperature of the cable sheath at the fiber damage location can be increased with the optical input power per core set to 0 dBm or less, and the temperature increase can be observed with the detection unit (thermography camera) 630 (described later). The heating laser light irradiated by the laser light irradiator of the heating unit 620 may be set to a wavelength band or power different from the light in the test wavelength band described above.

[0036] The detection unit 630 detects (acquires, measures) the temperature of the monitored section of the optical cable 400 acquired by the first acquisition unit 610. FIG. 6 is a diagram showing how the detection unit 630 detects the temperature of the monitored section of the optical cable 400. The detection unit 630 has a thermographic camera 630A that scans along the monitored section of the optical cable 400. The thermographic camera 630A is slidably supported on a guide rail (not shown) arranged along the monitored section of the optical cable 400, and may detect the temperature of the monitored section of the optical cable 400 while moving along the monitored section of the optical cable 400 by a drive mechanism (not shown) including a motor, gears, etc. Note that there is a degree of freedom in how the scanning mechanism of the detection unit 630 (thermographic camera 630A) is configured, and various design modifications are possible (for example, a scanning mechanism using a tripod, etc. may also be used).

[0037] The detection unit 630 may detect the temperature of the monitored section of the optical cable 400 (or may start scanning with the thermography camera 630A) after waiting for a temperature rise saturation time required for heating the monitored section of the optical cable 400. The start timing for calculating the temperature rise saturation time may be, for example, the timing when the heating unit (laser light irradiation unit) 620 starts irradiating the optical cable 400 with a heating laser light.

[0038] As a first temperature detection mode, the detection unit 630 (thermography camera 630A) may detect the post-heating temperature after the heating unit (laser light irradiation unit) 620 heats the monitored section of the optical cable 400 (after the temperature rise saturation time has elapsed).

[0039] As a second temperature detection mode, the detection unit 630 (thermography camera 630A) may detect the pre-heating temperature before the monitored section of the optical cable 400 is heated by the heating unit (laser light irradiation unit) 620, and the post-heating temperature after the monitored section of the optical cable 400 is heated by the heating unit (laser light irradiation unit) 620 (after the temperature rise saturation time has elapsed).

[0040] As described above, in the case of a white cable, if the optical fiber bundle 430 is damaged but the outer jacket 460 is not damaged, a portion of the leaked light from the optical fiber bundle 430 is absorbed by the outer jacket 460, and the remaining portion is emitted from the outer jacket 460, so that the temperature of the outer jacket 460 of the optical cable 400 is unlikely to rise. On the other hand, in the case of a black cable, if the optical fiber bundle 430 is damaged but the outer jacket 460 is not damaged, all of the leaked light from the optical fiber bundle 430 is absorbed by the outer jacket 460, so that the temperature of the outer jacket 460 of the optical cable 400 is likely to rise.

[0041] Using the above characteristics, the detection unit 630 (thermography camera 630A) may vary the temperature rise saturation time, which is the waiting time from the start of heating the monitored section of the optical cable 400 until temperature detection, depending on the color of the outer sheath 460 of the optical cable 400. More specifically, in the case of a white cable, the heating effect of the monitored section of the optical cable 400 is unlikely to appear early (the temperature is unlikely to rise), so the temperature rise saturation time may be set relatively longer (longer than for a black cable). Conversely, in the case of a black cable, the heating effect of the monitored section of the optical cable 400 is likely to appear early (the temperature is likely to rise), so the temperature rise saturation time may be set relatively shorter (shorter than for a white cable).

[0042] The second acquisition unit 640 is realized as a functional component of a computer (CPU: Central Processing Unit) of the optical cable monitoring device 600. The second acquisition unit 640 acquires (identifies, calculates, detects) abnormal locations (fiber damaged locations) in the monitored section of the optical cable 400 based on the temperature detection results of the monitored section of the optical cable 400 by the detection unit 630 (thermography camera 630A).

[0043] When the detection unit 630 detects the post-heating temperature of the monitored section of the optical cable 400 (in the case of the first temperature detection mode described above), the second acquisition unit 640 acquires abnormal locations in the monitored section of the optical cable 400 based on the post-heating temperature.

[0044] More specifically, the second acquisition unit 640 acquires, as an abnormal portion, a portion of the monitored section of the optical cable 400 where the post-heating temperature is equal to or higher than the threshold temperature.

[0045] When the detection unit 630 detects the pre-heating temperature and post-heating temperature of the monitored section of the optical cable 400 (in the case of the second temperature detection mode described above), the second acquisition unit 640 acquires abnormal locations in the monitored section of the optical cable 400 based on the differential temperature between the pre-heating temperature and the post-heating temperature.

[0046] More specifically, the second acquisition unit 640 acquires, as an abnormal location, a location in the monitored section of the optical cable 400 where the difference temperature between the pre-heating temperature and the post-heating temperature is equal to or greater than the threshold temperature.

[0047] The second acquisition unit 640 may utilize the characteristics of the white cable and black cable described above to vary the threshold temperature that serves as the criterion for determining abnormal locations in the monitored section of the optical cable 400 depending on the color of the outer sheath 460 of the optical cable 400.

[0048] For example, the threshold temperature may be set lower for a white cable, which tends to have a low cable temperature, and higher for a black cable, which tends to have a high cable temperature.

[0049] In addition, when the optical cable 400 is installed (exposed) outdoors, temperature unevenness occurs in the longitudinal direction (extension direction) of the optical cable 400 depending on environmental factors (for example, weather, temperature, humidity, sunlight exposure, etc.), and this temperature unevenness may hinder (obstruct) the identification of an abnormality. Therefore, in order to reduce the influence of temperature unevenness due to the above-mentioned environmental factors, parameters such as the temperature rise saturation time and the threshold temperature may be changed depending on the position in the longitudinal direction (extension direction) of the optical cable 400.

[0050] FIG. 7 is a diagram showing how the detector 630 detects the temperature of the monitored section of the optical cable 400 and how the second acquirer 640 acquires the abnormal points in the monitored section of the optical cable 400. In FIG.

[0051] In the example of FIG. 7, the monitored section of the optical cable 400 is divided into monitored sections 400-1, 400-2, 400-3, 400-4, 400-5, 400-6, . . . , 400-N (N is a natural number), and the detected temperatures (post-heating temperatures or differential temperatures) T1, T2, T3, T4, T5, T6, . . . , TN of each of the divided monitored sections are shown. The detected temperatures T1 to TN of the monitored sections 400-1 to 400-N are then compared to a threshold temperature Tth to determine whether they are higher or lower. Divided monitored sections whose detected temperatures are lower than the threshold temperature Tth are determined to be normal, and divided monitored sections whose detected temperatures are equal to or higher than the threshold temperature Tth are identified as abnormal locations. In the example of FIG. 7, divided monitored sections T1, T2, T4 to T6, . . . , TN are determined to be normal, and divided monitored section T3 is identified as an abnormal location.

[0052] Temperature detection and identification of abnormal locations in the monitored section of the optical cable 400 may be performed all at once along the entire length of the monitored section of the optical cable 400, or may be performed for each divided monitored section of the optical cable 400. In the former case, temperatures T1 to TN of the monitored sections 400-1 to 400-N are detected all at once, and then the detected temperatures T1 to TN are compared with the threshold temperature Tth. In the latter case, when the temperature of one monitored section is detected, the detected temperature is compared with the threshold temperature Tth, and then when the temperature of another monitored section is detected, the detected temperature is compared with the threshold temperature Tth, and this process is performed for all divided monitored sections.

[0053] In this embodiment, the cable section containing the fiber damage and the connection point near the damage are first identified. This identification can be achieved by measuring with an OTDR or checking the optical continuity within the optical closure. Next, a thermographic camera is used to pinpoint the fiber damage. In the case of a PON network used in FTTH, communication light is constantly emitted from the central office, resulting in leakage of communication light from the fiber damage. However, because the communication light has an average optical power of 0 dBm or less, it is difficult to observe temperature rise with a thermographic camera even in a cable with a black outer sheath. Therefore, a laser light source capable of outputting an average optical power of 3 dBm or more is connected to the optical fiber containing the optical fiber damage. Light from the laser light source is emitted from the optical fiber damage and absorbed by the optical cable outer sheath. However, since it takes about 100 seconds for the temperature rise to saturate, the system waits until the temperature saturates before capturing images with a thermographic camera.

[0054] Furthermore, in the case of optical fiber cables laid outdoors, temperature variations can occur from place to place, making it difficult to identify areas where temperatures have risen. In this case, the cable is photographed with a thermographic camera when the output of the laser light source is turned off, then the laser light source is turned on, and after waiting about 100 seconds, the cable is photographed again with the thermographic camera. By extracting the difference in temperature obtained from these two photographed images, it is possible to identify areas where temperatures have risen due to the laser light source, even if there are temperature variations in the cable itself.

[0055] FIG. 8 is a first flowchart showing the processing steps of the optical cable monitoring method.

[0056] In step ST1, the first acquisition unit 610 (OTDR device 610A, optical closure 610B) acquires the monitored section of the optical cable 400. In step ST2, the heating unit (laser light irradiation unit) 620 heats the monitored section of the optical cable 400. In step ST3, the detection unit 630 (thermography camera 630A) detects the temperature of the divided monitored section of the monitored section of the optical cable 400.

[0057] In step ST4, it is determined whether the temperature of the divided monitoring section detected in step ST3 is equal to or higher than the threshold temperature. If the temperature of the divided monitoring section detected in step ST3 is lower than the threshold temperature (step ST4: No), it is determined that there is no abnormality and the process proceeds to step ST5, where the divided monitoring section among the monitoring sections of the optical cable 400 is changed, and then the process returns to step ST3 to detect the temperature of the new divided monitoring section after the change.

[0058] If the temperature of the divided monitoring section detected in step ST3 is equal to or higher than the threshold temperature (step ST4: Yes), the process proceeds to step ST6, where the divided monitoring section is identified as an abnormal part in the monitoring section of the optical cable 400, and repairs are performed. Specifically, the cable sheath is stripped from the damaged part of the optical fiber, the optical fiber is reconnected, and then the stripped part of the cable sheath is protected.

[0059] FIG. 9 is a second flowchart showing the processing steps of the optical cable monitoring method.

[0060] In step ST11, the first acquisition unit 610 (OTDR device 610A, optical closure 610B) acquires the monitored section of the optical cable 400. In step ST12, the detection unit 630 (thermography camera 630A) detects the pre-heating temperature before heating the monitored section of the optical cable 400. In step ST13, the heating unit (laser light irradiation unit) 620 heats the monitored section of the optical cable 400. In step ST14, the detection unit 630 (thermography camera 630A) detects the post-heating temperature after heating the divided monitored section of the monitored section of the optical cable 400.

[0061] In step ST15, it is determined whether the difference in temperature between the pre-heating temperature and the post-heating temperature of the divided monitoring section is equal to or greater than the threshold temperature. If the difference in temperature of the divided monitoring section is less than the threshold temperature (step ST15: No), it is determined that there is no abnormality and the process proceeds to step ST16, where the divided monitoring section among the monitoring sections of optical cable 400 is changed, and then the process returns to step ST14 to detect the post-heating temperature after heating the new divided monitoring section after the change.

[0062] If the differential temperature of the divided monitoring section is equal to or higher than the threshold temperature (step ST15: Yes), the process proceeds to step ST17, where the divided monitoring section is identified as an abnormal part in the monitoring section of the optical cable 400, and repairs are performed. Specifically, the cable sheath is stripped from the damaged part of the optical fiber, the optical fiber is reconnected, and then the stripped part of the cable sheath is protected.

[0063] As such, the optical cable monitoring device of this embodiment has a first acquisition unit that acquires the monitored section of the optical cable, a heating unit that heats the monitored section of the optical cable, a detection unit that detects the temperature of the monitored section of the optical cable, and a second acquisition unit that acquires abnormal locations in the monitored section of the optical cable based on the temperature detection results of the monitored section of the optical cable.

[0064] For example, the first acquisition unit (in the first acquisition step) acquires the section to be monitored from the entire section of the optical cable (between the terminal and the receiving station) (performs a primary screening to narrow down the section from the entire length), and the second acquisition unit (in the second acquisition step) acquires the abnormality location in the monitored section of the optical cable based on the temperature detection results (after heating or before and after heating) of the monitored section of the optical cable (performs a secondary screening to pinpoint the abnormality location). This makes it possible to pinpoint the abnormality location in the optical cable non-destructively and easily.

[0065] In the optical cable monitoring technology of this embodiment, the cable sheath is heated by light emitted from the damaged part of the optical fiber and observed with a thermographic camera. If a temperature increase is confirmed, the damaged part is reconnected. Infrared thermography measures the internal temperature of the optical fiber by photographing the infrared light emitted from the damaged part of the optical fiber with a thermographic camera, allowing for non-destructive diagnosis of the internal condition of the optical fiber. If the temperature of the optical fiber changes due to a fault, the fault location can be pinpointed using infrared thermography.

[0066] The specific procedure of the optical cable monitoring technique of this embodiment is as follows. (1) Identify cable sections with fiber damage and nearby splice points of optical fibers by OTDR measurement or optical continuity confirmation within the optical closure (first acquisition step). (2) Light from a laser light source is incident on an optical fiber having fiber damage (heating step). (3) Wait until the temperature rise is saturated. (4) The area suspected of being faulty is photographed using a thermographic camera (detection step). (5) If no temperature rise is observed in the photographed image, change the photographing location and repeat step (4) above. If a temperature rise is observed in the photographed image, perform step (6) below. (6) Identifying the location of the optical fiber damage from the location of the temperature increase in the captured image (second acquisition step). (7) Peel back the cable jacket from the damaged optical fiber and reconnect the optical fiber. (8) Protect the area where the cable sheath has been stripped.

[0067] Although the invention according to the present disclosure has been described in detail above, it is clear to those skilled in the art that the invention according to the present disclosure is not limited to the embodiments described in the present disclosure. The invention according to the present disclosure can be implemented in modified and altered forms without departing from the spirit and scope of the invention as defined by the description of the claims. Therefore, the description of the present disclosure is intended to be illustrative and does not impose any limiting meaning on the invention according to the present disclosure. [Explanation of symbols]

[0068] 100 FTTH systems 200 devices 300 Receiving Station 400 Optical Cable 410 Spacer 420 Slots 430 Optical fiber bundle (tape-shaped optical fiber) 430a optical fiber 430b Optical fiber for monitoring 440 Tension member 450 Waterproof Tape 460 Outer skin (sheath) 500A 500B 500C Relay section 600 Optical cable monitoring device 610 First acquisition part 610A OTDR device 610B Optical Closure 620 Heating unit (laser light irradiation unit) 630 Detector 630A Thermal Imaging Camera 640 Second Acquisition Department

Claims

1. a first acquisition unit that acquires a monitored section of an optical cable; a heating unit that heats the monitoring target section of the optical cable; a detector for detecting the temperature of the monitored section of the optical cable; a second acquisition unit that acquires an abnormality location in the monitored section of the optical cable based on a temperature detection result of the monitored section of the optical cable; and the detection unit waits for a temperature rise saturation time required for heating the monitored section of the optical cable, and then detects the temperature of the monitored section of the optical cable. An optical cable monitoring device characterized by:

2. The optical cable includes an optical fiber bundle and an outer jacket covering the optical fiber bundle, the detection unit varies the temperature rise saturation time depending on the color of the outer jacket of the optical cable.

2. The optical cable monitoring device according to claim 1.

3. a first acquisition unit that acquires a monitored section of an optical cable; a heating unit that heats the monitoring target section of the optical cable; a detector for detecting the temperature of the monitored section of the optical cable; a second acquisition unit that acquires an abnormality location in the monitored section of the optical cable based on a temperature detection result of the monitored section of the optical cable; and the detection unit detects a pre-heating temperature before heating the monitored section of the optical cable and a post-heating temperature after heating the monitored section of the optical cable; the second acquisition unit acquires an abnormality location in the monitored section of the optical cable based on a differential temperature between the pre-heating temperature and the post-heating temperature. An optical cable monitoring device characterized by:

4. The second acquisition unit acquires, as the abnormal location, a location in the monitored section of the optical cable where the differential temperature is equal to or greater than a threshold temperature.

4. The optical cable monitoring device according to claim 3.

5. The optical cable includes an optical fiber bundle and an outer jacket covering the optical fiber bundle, the second acquisition unit varies the threshold temperature depending on the color of the outer jacket of the optical cable; 5. The optical cable monitoring device according to claim 4.

6. a first acquisition unit that acquires a monitored section of an optical cable; a heating unit that heats the monitoring target section of the optical cable; a detector for detecting the temperature of the monitored section of the optical cable; a second acquisition unit that acquires an abnormality location in the monitored section of the optical cable based on a temperature detection result of the monitored section of the optical cable; and The optical cable includes an optical fiber bundle and an outer jacket covering the optical fiber bundle, the heating unit has a laser light irradiation unit that irradiates a heating laser light from one end side of the optical cable, the laser light irradiating unit varies the intensity of the heating laser light depending on the color of the outer jacket of the optical cable. An optical cable monitoring device characterized by:

7. The detection unit includes a thermographic camera that scans along the monitored section of the optical cable.

7. The optical cable monitoring device according to claim 1, wherein the optical cable monitoring device is a monitoring device for monitoring an optical fiber.

8. acquiring a section of an optical cable to be monitored; heating the monitored section of the optical cable; detecting a temperature of the monitored section of the optical cable; acquiring an abnormality location in the monitored section of the optical cable based on a temperature detection result of the monitored section of the optical cable; and In the detecting step, after waiting for a temperature rise saturation time required for heating of the monitored section of the optical cable, the temperature of the monitored section of the optical cable is detected. An optical cable monitoring method comprising:

9. acquiring a section of an optical cable to be monitored; heating the monitored section of the optical cable; detecting a temperature of the monitored section of the optical cable; acquiring an abnormality location in the monitored section of the optical cable based on a temperature detection result of the monitored section of the optical cable; and In the detecting step, a pre-heating temperature before heating the monitored section of the optical cable and a post-heating temperature after heating the monitored section of the optical cable are detected, In the step of acquiring the abnormality location, the abnormality location in the monitored section of the optical cable is acquired based on a differential temperature between the pre-heating temperature and the post-heating temperature. An optical cable monitoring method comprising:

10. acquiring a section of an optical cable to be monitored; heating the monitored section of the optical cable; detecting a temperature of the monitored section of the optical cable; acquiring an abnormality location in the monitored section of the optical cable based on a temperature detection result of the monitored section of the optical cable; and The optical cable includes an optical fiber bundle and an outer jacket covering the optical fiber bundle, In the heating step, a laser light irradiation step is performed in which a heating laser light is irradiated from one end side of the optical cable, In the laser light irradiation step, the intensity of the heating laser light is varied depending on the color of the outer jacket of the optical cable. An optical cable monitoring method comprising:

Images