JP2015220694A - Device for identifying optical fiber core beneath splitter, and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To identify an optical fiber core beneath a supplier currently in use in a short time with small labor.SOLUTION: A bent fiber 41 is formed on the optical fiber core on the upper part of an optical splitter 151, so that a probe 42 is attached thereto. Wavelength-multiplexed uplink signal light (for a plurality of channels) is acquired by the probe 42, so that wavelength-by-wavelength light intensity of he received uplink signal light is measured. The measured light intensity is compared with a preset threshold. Based on the comparison result, uplink signal light corresponding to a wavelength shorter than the threshold is blocked, whereas uplink signal light corresponding to a wavelength of the threshold or longer is amplified, so that each use state of the plurality of channels is monitored by a monitor tool 45.

Description

  The present invention relates to a technique for specifying an optical fiber core wire below a splitter by using an optical fiber core wire at the top of a splitter for an optical signal output from an optical network unit.

  In communication systems using optical fiber cables, trouble relocation work and optical fiber cable accommodation replacement work are performed. In trouble relocation work and optical fiber cable accommodation replacement work, the optical fiber cable (physical) is temporarily disconnected, and sometimes communication is interrupted while the user uses the service.

  The user will be notified in advance of the construction (communication interruption notice limited to the time zone), but the user will use the service when cutting the optical fiber so as not to reduce customer satisfaction. It is desirable to have a method that can determine whether or not it is in the middle. If the service usage status can be ascertained for each optical line, the inconvenience felt by individual users can be minimized by switching the optical fiber being used later or by switching flexibly according to the service usage status of the user. Can be suppressed.

  For this reason, as a technology for monitoring the traffic of the optical access network and determining the service usage status of the user, the optical network terminal unit (ONU (Optical Network Unit)) installed in the user's house is installed in the communication building. A method has been proposed in which a part of an upstream optical signal to an optical line terminal (OLT) is received, and the data frame is analyzed to determine the usage state of each optical line. (Non-patent document 2). Recently, a method for monitoring upstream signal light with a side light input / output device and an APD (avalanche photodiode) in the section below the off-site splitter without entering the switching center has been proposed (non- Patent Document 1).

Shinbo, “Monitoring of upstream communication light using optical side output technology”, IEICE Technical Report, Optical Fiber Application Technology, 15-18, OPE 2013-207 (2014-02) Kashimura, “FTTH section communication monitoring technology that realizes confirmation during call by switching work such as relocation of trouble”, NTT Technical Journal, 2009.5, pp. 40 Shinbo, "Study of splitter lower contrast method using upstream communication light level fluctuation detection", IEICE Society Conference, B-10-19, 2013

  By the way, in the above method, in order to specify the splitter lower optical fiber core in use, the split optical fiber cores are monitored one by one in the lower part of the splitter. Conventionally, there has been a strong demand for a method that can identify the optical fiber core wire under the splitter in use in a short time and with little effort, for example, in an optical cable unit replacement work.

  An object of the present invention is to provide an apparatus and method for identifying an optical fiber core under a splitter that can identify an optical fiber core under the splitter in use in a short time and with little effort.

  In order to achieve the above object, a splitter lower optical fiber core identifying device according to the present invention wavelength-multiplexes upstream signal light from a plurality of first optical fiber cores to which an optical line terminator is connected. An optical fiber core identifying device used in a communication system including a splitter that outputs to two optical fiber cores and identifying a first optical fiber core being used, the second optical fiber core identifying device of the splitter, A first bent portion is formed which is attached to the optical fiber core side and leaks the upstream signal light output from the optical line termination device from the second optical fiber core in a state where communication continuation can be maintained at least. A first optical fiber bending device; a light receiving portion that receives upstream signal light leaked from the first bending portion; and a usage state of the optical line termination device is monitored from the upstream signal light received by the light receiving portion. The light intensity by wavelength of the upstream signal light received by the monitor unit and the light receiving unit is measured, the measured light intensity is compared with a preset threshold value, and a wavelength less than the threshold value is handled based on the comparison result. And an analysis control unit that blocks the upstream signal light, amplifies the upstream signal light corresponding to the wavelength equal to or greater than the threshold, and outputs the amplified upstream signal light to the monitor unit.

  If comprised in this way, a 1st bending part will be formed in the 2nd optical fiber core wire of a splitter upper part, a light-receiving part will be mounted | worn, and the wavelength-multiplexed (for several line | wire) upstream signal light will be acquired and light-receiving Measure the light intensity of each upstream signal light by wavelength, compare the measured light intensity with a preset threshold value, block the upstream signal light corresponding to the wavelength below the threshold based on the comparison result, and exceed the threshold value By amplifying the upstream signal light corresponding to the wavelength of the light, and monitoring the usage status for multiple lines with the monitor unit, the usage status for the multiple lines can be collectively determined. The fiber core can be specified. As a result, it is possible to specify the optical fiber core under the splitter in use in a short time and with less labor of one operator compared to the method of monitoring the optical fiber cores after branching by the splitter one by one.

  Moreover, one viewpoint of the identification apparatus of the splitter lower optical fiber core wire which concerns on this invention is equipped with the following aspects.

  In the first aspect, the analysis control unit includes an attenuator for attenuating the upstream signal light received by the light receiving unit by an arbitrarily adjustable amount of narrowing, and an amplifier for amplifying the output of the attenuator.

  According to the first aspect, the analysis control unit can have a simple configuration of a known attenuator and a known amplifier.

  According to a second aspect, the first optical fiber core is mounted on the first optical fiber core side of the splitter, and the upstream optical signal output from the optical line terminator is at least capable of maintaining communication continuity. And a second optical fiber bending device for forming a second bent portion that leaks from the first optical fiber.

  According to the second aspect, after the first optical fiber core wire being used is specified by the monitor unit, the second bent portion is formed in the first optical fiber core wire being used at the lower part of the splitter, By reducing the light intensity of the upstream signal light having the wavelength corresponding to the first optical fiber core being used in the light receiving unit by a predetermined intensity, the analysis control unit applies the upstream signal light having the wavelength to the monitoring unit. By cutting off transmission, it is possible to save labor in an optical fiber communication monitor.

  In a third aspect, the attenuator includes an interface for connecting to a known computer device, and the amount of narrowing of the attenuator is automatically determined based on the monitoring result of the monitor unit by the known computer device through the interface. Be controlled.

  According to the third aspect, a known computer device such as a personal computer is connected to the attenuator, and the amount of attenuation of the attenuator can be automatically controlled by using the computer device, thereby enabling a shorter time than manual control by the operator. Can be controlled.

  The present invention monitors the signal light of the optical fiber core before branching at the upper part of the off-site splitter, so that the use status of up to eight lines can be collectively determined, and the optical fiber core of the lower part of the splitter being used is It is possible to specify. Therefore, since the core wire at the bottom of the splitter can be closed and specified at the site, the arrangement of one worker is minimized.

The figure which shows the structure of the system applied to embodiment of this invention. The figure which shows a mode that the optical fiber core wire of the splitter lower part using optical side input / output technology is specified. The figure which shows a mode that the optical fiber core wire of the splitter lower part using a prior art is specified. The figure which shows the structure of the 1st Embodiment of this invention. The flowchart which shows the control processing procedure which adjusts the light quantity of an attenuator in the 2nd Embodiment of this invention. The figure which shows the method of specifying the optical fiber core wire using the bending of the optical fiber core wire of the splitter lower part in the 3rd Embodiment of this invention. The figure which shows the automatic adjustment of an attenuator in the 4th Embodiment of this invention.

  Prior to describing an embodiment according to the present invention, a system to which the embodiment is applied will be described. Here, examples of Non-Patent Documents 1 to 3 will be described as a representative.

  FIG. 1 is a diagram illustrating an example of a relationship between an optical line terminal (OLT) 11 and an optical network unit (ONU) 12. The OLT 11 installed in the communication building 1 is connected to a closure 15 near the subscriber home 2 via an integrated wiring module device (IDM) 14 and an optical cable 13. The closure 15 includes an eight-branch type optical splitter 151, for example. The ONU 12 in the subscriber house 2 is connected to one of the downstream terminals (hereinafter referred to as the lower part) of the optical splitter 151 via an optical fiber. By connecting the OLT 11 and the ONU 12, various services such as the Internet, optical telephone, and video distribution are provided.

  By the way, since the optical cable 13 is installed outside the office, construction work is carried out every day by road widening construction and telephone pole movement construction. In the widening work and the utility pole moving work, the optical cable 13 is switched.

  In the switching work of the optical cable 13, since the optical fiber in the optical cable 13 that has already been stretched is cut and connected to the newly installed optical cable, the service provided to the subscriber is temporarily cut. The workers of the switching work are informed in advance to minimize the effect of the subscriber becoming unable to use the service if the fiber that provides the service suddenly is cut during the construction, I want to confirm that the subscriber is not using the service.

  Therefore, as shown in Non-Patent Documents 1 and 2, a method of confirming the usage status of the ONU 12 using the monitor tool 23 has been proposed. FIG. 2 shows an outline of Non-Patent Document 1. A bent portion 21 is formed in the optical fiber core under the optical splitter 151 outside, the upstream signal light from the ONU 12 leaking from the bent portion 21 is received by the probe 22, and the upstream signal light is received by the monitor tool 23 downstream of the probe 22. The personal computer (hereinafter referred to as a personal computer) 24 confirms the use status of the ONU 12. In Non-Patent Document 1, the target optical fiber is only a core portion having a diameter of 0.25 mm and a glass portion composed of a core and cladding glass and the glass covered with a coating.

  However, considering the actual equipment configuration, the optical fiber is covered with a tube to further protect the core wire with an outer diameter of 0.25 mm and the outer diameter is increased to 0.9 mm, and the core wire with an outer diameter of 0.25 mm is protected. As a result, the outer diameter exceeds 1mm. Leakage light is output by bending a tube or a cord exceeding an outer diameter of 1 mm.

  However, leakage light may be output, but the same light intensity as in Non-Patent Documents 1 and 2 cannot be maintained. In Non-Patent Documents 1 and 2, even with a 0.25 mm core, the coupling efficiency is -25 dB, which is very weak leakage light. The reason why the thickness is further increased to protect the core wire with respect to the 0.25 mm core wire is that the leaked light is further absorbed by the thickness.

  Therefore, in Non-Patent Documents 1 and 2, optical fibers that can be operated outside the office are limited. Therefore, it is a problem when applied as actual construction.

  Therefore, a method of specifying the optical fiber core wire under the optical splitter 151 by the method shown in Non-Patent Document 3 has been proposed. FIG. 3 shows a form in which Non-Patent Document 3 is represented by an equipment drawing. The monitor tool 33 is installed in the communication building 1. Further, an IDM 14 is installed in the communication building 1, and a port 141 is provided in the IDM 14. The upstream signal of the ONU 12 is branched from the port 141 and the upstream signal light is propagated to the monitor tool 33.

  At this time, the monitor tool 33 has a function of measuring the optical signal intensity of the upstream signal light. When the worker bends the core wire at the lower part of the splitter to form the core wire bending portion 31 at the construction site (closure 15 in FIG. 3), a loss occurs in the core wire bending portion 31, and the monitor tool installed in the communication building 1 Since the light receiving power of the upstream signal light is lowered on 33, the optical fiber core wire under the 8-branch optical splitter 151 can be specified through a series of operations.

  However, one worker is placed in the communication building 1 away from the construction site just to check the power fluctuation with the monitor tool 33, and one worker is placed on the construction site, which requires a total of two workers. And not efficient. Therefore, an embodiment of the present invention in which the core wire under the splitter can be specified at the construction site will be described below.

(First embodiment)
FIG. 4 is a diagram illustrating a communication system to which the splitter lower optical fiber core specifying device according to the first embodiment is applied. 4, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the first embodiment, when the operator bends the optical fiber core on the upper side of the 8-branch type optical splitter 151 using the optical fiber bending device 40, the communication light propagating through the fiber core leaks to the outside. The leaked light can be received by the probe 42 disposed in the vicinity of the bending fiber 41. That is, the optical signal propagating through the fiber core can be extracted to the outside simply by bending the optical cable 13.

  The optical fiber bending device 40 bends the optical fiber core wire on the upper side of the optical splitter 151 with a bending radius of 4 mm or more and an angle of 30 degrees or less in order to realize a gentle bending with which communication is not interrupted.

  An attenuator 43 capable of arbitrarily adjusting the amount of narrowing is connected to the subsequent stage of the probe 42. The leaked light transmitted through the attenuator 43 and having a weak light intensity is amplified to a predetermined intensity by the amplifier 44 and emitted to the monitor tool 45. The monitor tool 45 measures the optical signal intensity for each wavelength of the leaked light, that is, the upstream signal light, and outputs the measurement result to the personal computer 46.

  The personal computer 46 displays the usage status of the ONU 12 on a monitor (not shown) based on the measurement result output from the monitor tool 45. With this display, the operator can specify the optical fiber core wire in use among the optical fiber core wires for the eight lines on the lower side of the optical splitter 151.

(Second Embodiment)
In the second embodiment, how to use the apparatus will be described based on the configuration shown in the first embodiment.

  The upstream signal light (wavelength 1310 nm) from the ONU 12 is leaked to the outside of the optical fiber core by bending the optical fiber core wired at the top of the eight-branch optical splitter 151. The leaked light is received by the probe 42, passes through the attenuator 43, and is supplied to the amplifier 44. The amplifier 44 increases the light intensity of the leakage light whose light intensity is weakened by passing through the attenuator 43. Thereafter, the communication light (wavelength 1310 nm) emitted from the amplifier 44 is analyzed by the monitor tool 45 and the analysis result is displayed on the monitor of the personal computer 46 as the usage status of the ONU 12.

  Incidentally, it is necessary to adjust the light amount of the attenuator 43 in order to identify the splitter lower optical fiber core wire being used from the upstream signal light from the ONU 12.

FIG. 5 is a flowchart showing a control processing procedure for adjusting the light amount of the attenuator 43.
The light amount adjustment of the attenuator 43 is executed by an adjustment device (not shown). This adjusting device is also connected to an amplifier 44 and a monitor tool 45.

  When the adjustment device starts adjusting the light amount of the attenuator 43 (step ST5a), the adjustment device reduces (decreases) the light amount of the attenuator 43 (step ST5b). In this case, the amount of light transmitted to the amplifier 44 also decreases. The amplifier 44 has a minimum light receiving sensitivity. If the amplifier 44 falls below the minimum light receiving sensitivity, the amplifier 44 does not operate. When the amplifier 44 does not operate, no light is emitted from the amplifier 44, so that the monitor tool 45 also does not operate.

  Therefore, the adjustment device determines whether or not the monitor tool 45 is operating (step ST5c). Since the monitor tool 45 is operating until the minimum light receiving sensitivity of the amplifier 44 is reached (YES: step ST5d), the adjusting device repeatedly executes the processing of step ST5b and step ST5c until the monitor tool 45 stops operating. To do.

  When the monitor tool 45 stops operating (NO: step ST5e), the adjustment device adjusts the attenuator 43 again, increases the light amount by 1 dB (step ST5f), and ends the light amount adjustment of the attenuator 43 (step ST5g). Here, the reason why the amount of light is increased by 1 dB is that the operation as a system is not stable if the light receiving sensitivity is adjusted to the minimum. As a result, the adjusted narrowing amount of the attenuator 43 is used as a threshold value.

  Here, if the ONU 12 is in use, the upstream signal light (wavelength 1310 nm) coming from the optical fiber core wire (# 1) is compared with the threshold value by the attenuator 43 and is equal to or higher than the threshold value. Is amplified and output to the monitor tool 45. On the other hand, the upstream signal light (for example, wavelength 1312 nm) arriving from the unused optical fiber core wire (# 2) is compared with the threshold value by the attenuator 43 and is lower than the threshold value. It falls below the sensitivity and is not emitted to the monitor tool 45.

(Operational effects of the first and second embodiments)
As described above, in the first and second embodiments described above, the bending fiber 41 is formed on the optical fiber core above the optical splitter 151, the probe 42 is mounted, and wavelength multiplexing is performed by the probe 42 (for a plurality of lines). ) Acquire upstream signal light, measure the light intensity of the received upstream signal light by wavelength, compare the measured light intensity with a preset threshold, and respond to wavelengths below the threshold based on this comparison result By blocking the upstream signal light, amplifying the upstream signal light corresponding to the wavelength equal to or greater than the threshold, and monitoring the usage status for multiple lines with the monitor tool 45, the usage status for the multiple lines can be collectively determined. The optical fiber core wire (# 1) under the optical splitter 151 in use can be identified.

  As a result, the optical splitter being used in a short time and with less labor required by one worker compared to the method of monitoring the optical fiber cores (# 1 to # 8) after branching by the optical splitter 151 one by one. The optical fiber core wire (# 1) at the bottom of 151 can be identified.

(Third embodiment)
In the third embodiment, a method for specifying an optical fiber core wire will be described. Here, the operation procedure after adjustment of the attenuator 43 shown in the second embodiment will be described.

  FIG. 6 shows a specific method of optical fiber core. When the optical fiber core wire under the optical splitter 151 is bent using the optical fiber bending device 40 or another optical fiber bending device to form the bending fiber 51, the amount of the upstream signal light from the ONU 12 is reduced by the bending fiber 51. As shown in the second embodiment, the margin is 1 dB, and if the optical fiber core wire of the 8-branch optical splitter 151 is bent to give a loss of 1 dB or more, the monitor tool 45 does not operate. You can see on the screen. Therefore, characteristics can be obtained by bending the optical fiber core wire under the optical splitter 151. From the viewpoint of the operator, an action of touching and bending the optical fiber core wire is performed while touching the monitor of the personal computer 46. An operator can specify the optical fiber core wire being used by one person, and is a method for specifying the core wire closed at the construction site. For example, if the ONU 12 subscriber is viewing a web page on the Internet, the monitor tool 45 will not operate, and if the ONU 12 subscriber is talking to another communication partner, the monitor tool 45 will not operate. Works.

  In addition, the optical fiber core under the optical splitter 151 is covered with a tube or the like for protection, but even if covered, it is thin and supple, and can be bent any number of times. It is easy to bend the fiber. Moreover, the margin is set to 1 dB, and in order to make a judgment by the personal computer 46, the loss of the bending is caused by 1 dB or more to characterize the optical fiber core. However, the lower part of the 8-branch optical splitter 151 is thin and flexible, so it is simple. The workability will not be worse than what can be done simply by bending it.

  In addition, since the optical fiber core wire is not covered with a tube or the like at the upper portion of the optical splitter 151, the leaked light can be acquired by the probe 42.

  Further, in the method for adjusting the amount of narrowing of the attenuator 43 according to the third embodiment, the adjustment device performs the processing of step ST5b and step ST5c until the loss generated in the bending fiber 51 is reached instead of the minimum light receiving sensitivity of the amplifier 44. Repeatedly.

  As described above, in the third embodiment, after the optical fiber core wire (# 1) being used is specified by the monitor tool 45 and the personal computer 46, the optical fiber core wire under the optical splitter 151 is bent to the optical fiber core wire being used. The fiber 51 is formed, and the optical intensity of the upstream signal light having the wavelength corresponding to the optical fiber core wire (# 1) in use in the probe 42 is reduced by a predetermined intensity, so that the attenuator 43 and the amplifier 44 can reduce the wavelength. The transmission of the upstream signal light to the monitor tool 45 is cut off, thereby making it possible to save labor in the optical fiber communication monitor.

  Further, according to the third embodiment, compared to the first and second embodiments, for example, whether the ONU 12 subscriber is viewing a web page on the Internet, or the ONU 12 subscriber. It is possible to specify the detailed usage status of the ONU 12 such as whether the user is in a state of making a call with another communication partner.

(Fourth embodiment)
In the fourth embodiment, a method for adjusting the attenuator 43 will be described. This apparatus determines the amount of narrowing of the attenuator 43 while observing the operation of the monitor tool 45.

  The attenuator 43 is provided with an interface 62 for connecting a personal computer 61. The operator automatically connects the personal computer 61 to the attenuator 43 and automatically controls the optical aperture of the attenuator 43 and a control for giving a 1 dB margin. Thereby, the worker can set in a shorter time than manual control.

  As described above, according to the fourth embodiment, a known computer device such as the personal computer 61 is connected to the attenuator 43, and the amount of narrowing of the attenuator 43 can be automatically controlled using the personal computer 61. It can be controlled in a shorter time than manual control.

(Other embodiments)
In the first to fourth embodiments, the example in which the analysis control unit is configured by the attenuator 43 and the amplifier 44 has been described. However, the analysis control unit may be realized by a single circuit. In this case, the analysis control unit measures the light intensity by wavelength of the upstream signal light received by the probe 42, compares the measured light intensity with a preset threshold value, and sets the wavelength below the threshold based on the comparison result. The corresponding upstream signal light is blocked, and the upstream signal light corresponding to the wavelength equal to or greater than the threshold is amplified and output to the monitor tool 45.

  In short, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Communication building, 2 ... Subscriber house, 11 ... OLT, 12 ... ONU, 13 ... Optical cable, 14 ... Integrated wiring module apparatus, 15 ... Closure, 21 ... Bending part, 22, 42 ... Probe, 23, 33, 45 ... Monitor tool, 24, 46, 61 ... Personal computer, 31 ... Core wire bending part, 40 ... Optical fiber bending device, 41, 51 ... Bending fiber, 43 ... Attenuator, 44 ... Amplifier, 62 ... Interface, 141 ... Port, 151: Optical splitter.

Claims (7)

Used in a communication system including a splitter that wavelength-multiplexes upstream signal light from a plurality of first optical fiber cores to which an optical line terminator is connected, and outputs the multiplexed signal light to a second optical fiber core. An optical fiber core specifying device below a splitter for specifying one optical fiber core,
A second optical fiber core attached to the splitter on the second optical fiber core side and connected to the splitter in a state where at least communication of the upstream signal light output from the optical line termination device can be maintained. A first optical fiber bender that forms a first bend that leaks from the
A light receiving portion for receiving upstream signal light leaked from the first bent portion;
A monitor unit for monitoring the usage state of the optical line termination device from the upstream signal light received by the light receiving unit;
The light intensity of each upstream signal light received by the light receiving unit is measured, and the measured light intensity is compared with a preset threshold value. Based on the comparison result, upstream signal light corresponding to a wavelength less than the threshold value is blocked. And an analysis control unit that amplifies the upstream signal light corresponding to the wavelength equal to or greater than the threshold and outputs the amplified signal light to the monitor unit.   The said analysis control part is provided with the attenuator which attenuates the upstream signal light received by the said light-receiving part by the amount of narrowing which can be adjusted arbitrarily, and the amplifier which amplifies the output of this attenuator. Optical fiber core wire identification device at the bottom of the splitter.   A second optical fiber that is attached to the first optical fiber core side of the splitter and leaks the upstream signal light output from the optical line terminator from the first optical fiber core wire in a state where communication can be continued at least; The apparatus for specifying an optical fiber core wire under a splitter according to claim 1 or 2, further comprising a second optical fiber bending device for forming a bending portion.   4. The optical fiber core wire under the splitter according to claim 2, wherein the narrowing amount of the attenuator is controlled using a minimum light receiving sensitivity of the amplifier or a loss generated in the second bent portion. Specific device. The attenuator includes an interface for connecting to a known computer device,
4. The optical fiber core below the splitter according to claim 2, wherein the amount of narrowing of the attenuator is automatically controlled based on the monitoring result of the monitor by the known computer device through the interface. Specific device. Used in a communication system including a splitter that wavelength-multiplexes upstream signal light from a plurality of first optical fiber cores to which an optical line terminator is connected, and outputs the multiplexed signal light to a second optical fiber core. An optical fiber core specifying method under a splitter for specifying one optical fiber core,
On the second optical fiber core side of the splitter, the upstream signal light output from the optical line terminator leaks from the second optical fiber core connected to the splitter in a state where communication can be continued at least. A first step of forming a first bent portion,
A second step of receiving upstream signal light leaked from the first bent portion;
The light intensity for each wavelength of the upstream signal light received in the second step is measured, the measured light intensity is compared with a preset threshold value, and the upstream signal light corresponding to a wavelength less than the threshold value based on the comparison result A third step of amplifying the upstream signal light corresponding to the wavelength equal to or greater than the threshold;
And a fourth step of monitoring the utilization state of the optical line termination device from the upstream signal light amplified in the third step.   Furthermore, on the first optical fiber core side of the splitter, the second signal light that leaks from the first optical fiber core wire in a state in which the upstream signal light output from the optical line terminator can be maintained at least in a continuous state. The method for identifying an optical fiber core under a splitter according to claim 6, further comprising a fifth step of forming a bent portion.