JP7709643B2 - Apparatus and method for locating optical fiber installations - Google Patents

Description

The present disclosure relates to technology for identifying the location of equipment in which optical fibers are installed.

Optical fiber measurement technologies that use Brillouin scattering include BOTDA (Brillouin Optical Time Domain Analysis) and BOTDR (Brillouin optical time domain reflectometer), which can measure changes in temperature and strain by observing changes in the Brillouin frequency shift (BFS) (see, for example, Non-Patent Document 1). The spatial resolution of these is expressed as Δz = νW/2, where ν is the speed of light in the optical fiber and W is the pulse width of the test light. In general, it is difficult to detect changes in events in the longitudinal direction that are shorter than the spatial resolution Δz.

When constructing an optical cable for optical communication, the length of the optical cable is recorded based on the length written on the outer sheath of the constructed optical cable. However, when the optical cable breaks down or there is a problem such as a closure being submerged, the location of the optical cable fault is identified using optical fiber measurement techniques such as OTDR (Optical Time Domain Reflectometer) measurement, which provides the actual length measurement result rather than the length, so the fault location is searched for on-site by comparing the length information at the time of construction with the actual length measurement result of the OTDR measurement. In facilities such as closures and manholes, the difference between the length and the actual length can be large due to the excess length of the optical cable or optical core wire, making it difficult to identify the location of the facility.

T. Horiguchi, K. Shimizu, T. Kurashima, M. Tateda, and Y. Koyamada, “Development of a Distributed Sensing Technique Using Brillouin Scattering”, JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 13, NO. 7, JULY 1995

The present disclosure aims to make it possible to identify the location of equipment in which optical fibers are installed.

The present disclosure has been made to address the above-mentioned problem, and identifies the positions of facilities such as manholes and aerial closures by measuring changes in the Brillouin gain bandwidth using optical fiber measurement technology that employs Brillouin scattering for feature points that exist or occur in the longitudinal direction of the optical fiber and are shorter than the spatial resolution Δz.

Specifically, the apparatus and method according to the present disclosure include:
An apparatus and method for locating an optical fiber installation, comprising:
Measure the Brillouin scattered light in the optical fiber using test light having a pulse width that provides a spatial resolution greater than that of the equipment;
The Brillouin gain bandwidth of the measured Brillouin scattered light is used to identify the location of the facility along the length of the optical fiber.

The present disclosure makes it possible to identify the location of the equipment in which the optical fiber is installed.

1 illustrates an example system configuration of the present disclosure. An example of an underground infrastructure that accommodates an optical fiber cable is shown. 1 shows an example of the Brillouin gain spectrum obtained at each measurement point, where (a) shows measurement point M1, (b) shows measurement point M2, and (c) shows measurement point M3. 13 shows an example of a feel test result according to the present embodiment.

Below, 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 considered to be identical to each other.

(System Configuration)
An example of a system configuration according to the present disclosure is shown in Fig. 1. A facility location identification device 10 according to the present disclosure includes a BOTDR or BOTDA 11 connected to an optical fiber 100, and a calculation processing unit 12 that performs calculation processing using measurement results of the BOTDR or BOTDA.

The optical fiber 100 is disposed in any facility specified in this disclosure. Examples of the facility include underground infrastructure facilities such as pipelines, manholes, handholes, and underground closures. Examples of overhead infrastructure facilities include overhead optical cables, overhead closures, and utility poles.

The BOTDR or BOTDA11 uses test light having a pulse width W according to the equipment to measure the Brillouin scattered light in the optical fiber 100. In the BOTDR or BOTDA11, the spatial resolution Δz for measuring the Brillouin scattered light can be determined by setting the pulse width W. Therefore, in this disclosure, the section length at each measurement point is set by setting the pulse width W.

The calculation processing unit 12 uses the Brillouin gain bandwidth of the Brillouin scattered light measured by the BOTDR or BOTDA 11 to identify the location of the equipment in the optical fiber 100. The calculation processing unit 12 of the present disclosure 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.

The BOTDR or BOTDA 11 of the present disclosure measures two or more Brillouin scattered lights with different BFSs present within the spatial resolution Δz by using a pulse width W corresponding to a spatial resolution Δz larger than the event to be detected. Through this measurement, the calculation processing unit 12 can acquire a waveform in which two or more Brillouin gain spectra (BGS) with different BFSs contained within the spatial resolution Δz are combined.

By measuring the change in the Brillouin gain bandwidth ΔG of this combined BGS, it is possible to determine whether a change has occurred in the longitudinal direction of the optical fiber 100. Therefore, for an underground optical cable section in which most of the longitudinal section is an underground conduit, the arithmetic processing unit 12 can identify the position of a manhole, which is a characteristic change point. Also, for an aerial optical cable section, the arithmetic processing unit 12 can identify the position of an aerial closure, which is a characteristic change point.

Figure 2 shows an example of underground infrastructure that houses an underground optical cable. Equipment sections S1 and S3 are pipelines 101, and equipment section S2 is a manhole 102. In this embodiment, a case in which the position of the manhole 102 in the longitudinal direction of the optical fiber 100 is detected will be described.

The facility location method of the present disclosure includes the following steps.
Step 1: Set the measurement spatial resolution Δz to a value equal to that of a manhole (2 m) or up to 300% larger.
Step 2: Each of the facility sections S1 to S3 is measured by the BOTDR or BOTDA with a pulse width W corresponding to the measurement spatial resolution Δz.
Step 3: Analyze the BGS width obtained as a result of the measurement.
Step 4: Identify the location where the BGS width changes abruptly (where a spike is observed).
Step 5: Record the distance between the spikes in step 4 as the actual cable length.

Step 1 will be described. Generally, the length of a manhole body is about 3 m, and 5 to 10 m of optical fiber 100, including excess length, is housed in the manhole 102 section. In this embodiment, in order to obtain a waveform that is a composite of multiple BWGSs with different BFSs originating from different equipment sections within the same measurement point M2, a BOTDR or BOTDA with a pulse width that provides a measurement spatial resolution Δz of 2 m or more is used.

Here, the upper limit of the pulse width W is arbitrary, but for example, it can be set to a value that makes the measurement spatial resolution Δz about 300% larger than the length of the manhole body. For example, if the facility is a manhole, the pulse width W can be set so that the measurement spatial resolution Δz is 6 m or less.

In step 2, the Brillouin gain spectrum corresponding to BFS ₁ in the equipment section S1, BFS ₂ in the equipment section S2, and BFS ₃ in the equipment section S3 is obtained by measuring the Brillouin scattered light generated by the test light. The BFS of the equipment sections S1 and S3 may be the same. It is known that the BFS varies depending on the temperature, the strain applied to the optical cable, the type and design parameters of the optical fiber 100, and the manufacturing lot, but it may be considered to be almost constant within the spatial resolution Δz of one optical cable in a typical cable installation state.

In step 2, measurement points M1 to M3 are different points measured with spatial resolution Δz, and have the same section length according to the pulse width W, all of which are 1 m or longer. Measurement points M1 and M3 are set to measure only the pipeline section, and measurement point M2 is set to straddle the pipeline section and the manhole section.

Figure 3 shows an example of the BGS obtained at each measurement point. As shown in Figures 3(a) and 3(c), at measurement points M1 and M3, the BFS is invariant within the spatial resolution Δz, so sharp BGS with narrow Brillouin gain bandwidths ΔG ₁ and ΔG ₃ are obtained. On the other hand, as shown in Figure 3(b), at measurement point M2, three Brillouin gain spectra with different BFSs from equipment sections S1, S2, and S3 are combined, and ΔG ₂ becomes wider than ΔG ₁ and ΔG ₃ .

Furthermore, when BFS ₂ has a value close to BFS ₁ and BFS ₃ , the measurement point M2 is effectively divided into three measurement points, M2-1, M2-2, and M2-3, to measure the Brillouin scattered light. In this case, test light with a pulse width W shorter than that of measurement point M2, which corresponds to the section length of each of measurement points M2-1, M2-2, and M2-3 within the same pulse width W, generates BGS _2-1 , BGS _2-2 , and BGS _2-3 with different BFSs, and the ΔG ₂ of the combined BGS becomes wider. This is synonymous with the BOTDA or BOTDR measurement results using a narrow pulse width W of test light, which means that the frequency spectrum of the test light is broadened, resulting in a broadened BGS.

FIG. 4 shows an example of a field test result according to the present embodiment. L _BGS shows an example of the distance distribution of the BGS width according to the present disclosure. In FIG. 4, the full width at half maximum (FWHM) is shown as an example of the BGS width. The point where the spike occurs due to the widening of the BGS width indicates the position of the manhole 102, and the interval between the spikes corresponds to the actual length of the optical fiber cable laid between the manholes 102.

L _BFS is a comparative example of the present disclosure, and shows the BFS measurement results. In the BFS measurement results shown in L _BFS , the BFS may or may not change even if the facility section is different, so it is difficult to identify the manhole position. For this reason, when using BFS, it is necessary to distinguish the facility section. On the other hand, when using the BGS width of the present disclosure, as shown in L _BGS , a spike due to the widening of the BGS width at the manhole position is clearly observed all at once.

Therefore, in the present disclosure, in step 3, the distance distribution of the BGS width as shown in L _BGS is obtained. Then, in step 4, the spike positions are identified. This allows the manhole positions to be identified. The interval between the spikes corresponds to the actual length of the cable laid between the manholes. Therefore, in step 5, the distance between the spikes is recorded as the actual cable length. In this way, in the present disclosure, in an underground optical facility, the position of the manhole, which is a characteristic point of the facility, can be identified in a single step.

In this embodiment, an example of an underground infrastructure facility is described, but the present disclosure is not limited to this. For example, in an aerial optical facility, it is possible to identify the position of an optical closure having a connection point. In this case, a BOTDR or BOTDA with a pulse width W is used such that the measurement spatial resolution Δz is equal to or greater than the length of the optical closure. As a result, in the present disclosure, in an aerial optical facility, it is possible to collectively identify the position of an aerial closure having a connection point.

As described above, the present disclosure detects whether a change occurs in the longitudinal direction of the optical fiber 100 by observing the change in the Brillouin gain bandwidth ΔBGS using the BOTDA or BOTDR. As a result, the present disclosure can collectively identify the position of any facility such as a manhole or an aerial closure. For example, the positions of a handhole, an underground closure, an aerial closure, and a utility pole can be collectively identified using a pulse width that provides a measurement spatial resolution Δz of 2 m or more. Therefore, according to the present disclosure, it is possible to identify the position (actual length) to the facility, and therefore it is possible to identify the actual fault position from the measurement result of the fault position by the OTDR.

This disclosure can be applied to the information and communications industry.

10: Facility location identification device 11: BOTDR or BOTDA
12: Processing unit 100: Optical fiber 101: Pipe 102: Manhole

Claims (4)

An apparatus for identifying the location of a facility in which optical fibers are installed, comprising:
Measure the Brillouin scattered light in the optical fiber using test light having a pulse width that provides a spatial resolution greater than that of the equipment;
Using the measured Brillouin gain bandwidth of the Brillouin scattered light, a position of the facility in the longitudinal direction of the optical fiber is identified.
Device. The facility is at least one of a handhole, an underground closure, an overhead closure, and a utility pole;
measuring the Brillouin scattered light in the optical fiber using test light having a pulse width that provides a spatial resolution of 2 m or more;
2. The apparatus of claim 1. the Brillouin gain bandwidth is the full width at half maximum of the Brillouin gain spectrum with respect to the longitudinal distance of the optical fiber;
A position where the full width at half maximum of the Brillouin gain spectrum is widened is identified as the position of the equipment.
3. Apparatus according to claim 1 or 2. 1. A method for identifying a location of an optical fiber installation, comprising:
Measure the Brillouin scattered light in the optical fiber using test light having a pulse width that provides a spatial resolution greater than that of the equipment;
Using the measured Brillouin gain bandwidth of the Brillouin scattered light, a position of the facility in the longitudinal direction of the optical fiber is identified.
method.