JP2011055281A - Method and system of identifying optical facility - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of identifying an optical facility, identifying a housing facility of an optical fiber by an optical measurement, in an optical fiber line lower than an optical splitter. <P>SOLUTION: The method of identifying the optical facility identifies the condition of a housing facility of an optical fiber configuring an optical line lower than an optical splitter 4, using an optical fiber having a unique Brillouin frequency shift different from each other in each aerial optical fiber cables 5<SB>1</SB>-5<SB>m</SB>connected with a part lower than the optical splitter 4, in an optical fiber line configuring the optical line including the optical splitter 4. The variation of the Brillouin frequency shift generated in the housing facility of the optical fiber is detected by a Brillouin optical pulse tester (BOTDR) to identify the condition of the housing facility of the optical fiber. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical equipment identification method and system used for construction and maintenance of an optical line using an optical fiber.

  In the maintenance and operation of optical fiber communication networks, it is very important to identify the optical equipment such as what route the optical fiber cable goes through or through the equipment when managing or repairing the optical fiber cable. It is. By grasping this in detail, it is possible to design additional changes in equipment and to specify the failure point in a short time when a failure occurs in the optical line, and to reduce the operation for maintenance operation.

  FIG. 5 is a configuration explanatory view showing a conventional optical equipment identification system. As shown in FIG. 5, an optical subscriber line terminating device (Optical line terminal: hereinafter referred to as OLT) 1 installed in the optical line facility building 17 and an optical subscriber line network device (Optical network unit) installed in the user's home 13. : Hereinafter referred to as ONU) 2 are connected by an optical fiber line.

  The configuration of the optical fiber line includes an underground optical cable 3 routed from the optical line facility building 17 through the underground wiring facility, an off-site optical splitter 4 that branches a signal transmitted through the optical fiber to a plurality of users, a connector, a fusion, etc. The connection unit 9, the aerial optical cable 5 constituting the aerial wiring in the vicinity of the user's home 13, the drop cable 15 that leads from the aerial to each user's home, and the home cable 16 that performs the wiring in the home, connect the OLT 1 and the ONU 2.

  The optical fiber line is connected to the module 9 such as the optical splitter 4 and the connection part 9 of the optical fiber cable by means such as a connector or fusion. However, the connection point is protected from environmental conditions such as water immersion and pulling. Covered by a closure 6 or cabinet 8.

  In order to identify the optical equipment, the optical cable length information and connection points stored in the optical line equipment database in advance, and the optical equipment information in which these are stored are compared with the measured loss / reflection distribution in the longitudinal direction of the optical fiber. . The optical fiber state is measured by remotely operating the optical test apparatus 10 installed in advance in the optical line facility building 17. Test light transmitted from an optical pulse tester (hereinafter referred to as OTDR) installed in the optical test apparatus 10 is incident on the optical fiber line through the optical coupler 11 and is subjected to backward Rayleigh scattered light in the optical fiber. And a loss and reflection distribution in the longitudinal direction of the optical fiber can be obtained by performing an optical pulse test that measures the return time and intensity change of the scattered light.

  For example, when it is measured and detected that a failure in which a large loss has occurred at a position L [m] in the longitudinal direction of the optical fiber cable is detected by OTDR measurement, L [m ] Can be identified by extracting the facility information at a distance of].

  However, optical equipment identification by OTDR measurement and equipment database collation is effective in the upper part (non-branching part) on the equipment building side from the optical splitter 4, but a plurality of ONUs for one OLT which is the mainstream in recent years. In the configuration of an optical access system (PON) that connects the two, the signal light as well as the test light are divided on the user side below the optical splitter 4 (branch), and the backscattered light is also superimposed and measured. Therefore, it is extremely difficult to monitor the loss and reflection distribution in the longitudinal direction of the optical fiber for each core, and it is impossible to identify the accommodation facility of the optical fiber below the optical splitter 4.

  In the unlikely event that a failure occurs below the optical splitter 4, in order to detect the failure point, an operator carries a portable OTDR 12 to the user's home 13 side and disconnects the optical line connection port of the ONU 2. The OTDR 12 is connected to perform a pulse test, the approximate position is detected from the OTDR result, and the failure position / failure equipment is specified by the distance information estimated from the visual observation. At this time, if it is determined that the failure is in the aerial facility, a repair work is performed by arranging a new aerial construction vehicle.

  As another prior art document, there is Non-Patent Document 1 regarding a technique for controlling the Brillouin frequency shift of an optical fiber core.

Y. Koyamada, S .; Nakamura, H .; Sotobayashi, and W.H. Chujo, “Simulating and designing Brillouin gain spectrum in single-mode fibers,” J. et al. Lighttw. Technol. , Vol. 22, no. 2, p. 631, Feb. 2004.

  In the conventional optical equipment identification method, it is difficult to identify the optical equipment below the optical splitter. For example, when a failure occurs, there is a problem that it takes time for workers to rush directly or to arrange work equipment.

  Further, in specifying the optical equipment by comparing the measurement result with the equipment data, there is a problem that it becomes difficult to specify the optical equipment if the equipment data is not registered or erroneously input.

  In order to solve the above-described problems, the present invention provides a unique Brillouin frequency shift in each optical fiber connected to the branching unit side from the optical branching unit in the optical fiber line constituting the optical line including the optical branching unit. An optical equipment identification method for identifying the status of accommodation equipment of an optical fiber constituting an optical path on the branching section side from the optical branching section using an optical fiber having a Brillouin frequency shift variation generated in the optical fiber accommodation equipment Is detected by a Brillouin scattered light measuring device, and the accommodation facility status of the optical fiber is identified.

  Further, the present invention is characterized in that in the optical equipment identification method, a Brillouin frequency shift variation caused by a pressure strain applied to the optical fiber connection portion is detected.

  Further, the present invention is characterized in that in the optical equipment identification method, the fluctuation period of the Brillouin scattered light intensity generated due to the birefringence of the bent portion having a specified diameter given in the middle of the optical fiber is detected. .

  Further, the present invention is characterized in that in the optical equipment identification method, an optical pulse is incident on an optical fiber line, one polarization component of the generated Brillouin scattered light is separated, and the intensity change period is detected.

  The optical equipment identification system of the present invention includes an optical fiber line constituting an optical line including an optical branching unit, and optical fibers having different Brillouin frequency shifts connected to the branching unit side from the optical branching unit. A Brillouin scattered light measuring device that detects fluctuations in the Brillouin frequency shift generated in the optical fiber accommodation equipment that constitutes the optical path on the branching portion side from the light branching portion, and the light is transmitted by the Brillouin scattered light measuring device. It is characterized in that the state of the optical fiber accommodation facility is identified by detecting a change in the Brillouin frequency shift occurring in the fiber accommodation facility.

  The present invention makes it possible to identify optical fiber accommodation equipment by optical measurement in an optical fiber line below the optical splitter. As a result, the time required for failure equipment can be shortened, optical line equipment maintenance can be made more efficient, and operation costs can be reduced.

1 is a configuration explanatory diagram showing an optical equipment identification system according to a first embodiment of the present invention. FIG. 2 is a configuration explanatory view showing an example of a Brillouin optical time domain reflectometer (hereinafter referred to as BOTDR) used in FIG. 1. It is composition explanatory drawing which shows the optical equipment identification system which concerns on the 2nd Embodiment of this invention. FIG. 4 is a configuration explanatory diagram illustrating an example of a BOTDR used in FIG. 3. It is composition explanatory drawing which shows the conventional optical equipment identification system.

  Hereinafter, embodiments of the present invention will be described in detail. In the figure, the same portions are described with the same reference numerals.

[Embodiment 1]
FIG. 1A is a configuration explanatory view showing an optical equipment identification system according to the first embodiment of the present invention, and FIG. 1B is a characteristic showing scattered light intensity with respect to frequencies of Brillouin backscattered light and Rayleigh backscattered light. FIG. 1C is a characteristic diagram showing a Brillouin frequency shift (hereinafter referred to as BFS) with respect to distance.

As shown in FIG. 1A, the OLT 1 and the Brillouin scattered light measuring instrument 10 'in the optical line facility building 17 are connected to one end of the underground optical cable 3 via the optical coupler 11, and the other end of the underground optical cable 3 is connected to the optical fiber. The optical fiber cables 5 ₁ , 5 ₂ , 5 ₃ ,..., 5 _m are connected to the non-branching ends of the optical splitter 4, which is a branching portion, via the connecting portions 9. Is connected.

The aerial optical fiber cable 5 ₃ is connected to the drop cable 15 via the connecting portion 9, the drop cable 15 is connected to the home cable 16 via the connecting portion 9 in the user's home 13, the in-home cable 16 ONU 2 Is connected. The aerial optical fiber cable 5 _m is connected to the drop cable 15, and the drop cable 15 is connected to the home cable 16 in the user home 13 via the connection unit 9, and the home cable 16 is connected to the ONU 2. The connecting portions 9 are each covered with an optical closure 6 or a cabinet 8.

  The Brillouin scattered light measuring instrument 10 'is a Brillouin frequency shift (hereinafter referred to as BFS) generated in an optical fiber housing facility such as an optical closure 6 or a cabinet 8 that covers the connecting portion 9 constituting the optical path on the branch side from the optical splitter 4. ) To detect the status of the accommodation facility of the optical fiber. For example, the BFS variation caused by the pressure strain applied to the optical fiber connection portion 9 is detected to identify the status of the accommodation facility for the optical fiber.

That is, aerial optical fiber cable _{5 1,} 5 _2, 5 3, the ......... _{5 m} is a different unique BFS respectively .nu.1, .nu.2, .........? M is allocated. As shown in FIG. 1B, BFS is a phenomenon in which Brillouin backscattered light, which is a kind of scattered light generated when pulsed light is incident on an optical fiber, causes a frequency shift of about 10 GHz with respect to incident pulsed light. It is. BFS can be changed by applying temperature and strain, but there is a method for adjusting the concentration of dopants such as GeO ₂ and F in an optical fiber as a method for assigning a larger change, and easily gives a BFS change of 1.5 GHz. (See, for example, Non-Patent Document 1).

  For example, BOTDR is used as the Brillouin scattered light measuring instrument 10 'for identifying the Brillouin scattered light individually for each optical fiber line.

  FIG. 2 is a configuration explanatory diagram showing an example of the BOTDR used in FIG. Since the Brillouin scattered light is a very small light of about −80 dB with respect to the input pulse peak power, a coherent detection technique is used.

As shown in FIG. 2, a continuous light of a frequency .nu.0 which emits light from the test light source 30 is branched in the mouth by the optical coupler 31 _1, and the local light .nu.0 and the probe light .nu.0. After the probe light ν0 is pulsed with the optical switch 35, and enters the optical fiber line to be measured fiber via the optical coupler 31 _2.

Brillouin backscattered light frequency shift νn generated from the light splitter at the bottom of the optical fiber line passes through the optical coupler 31 _2, wherein are multiplexed by the local light ν0 and the optical coupler 31 _3, the beat signal by the light receiving element 34 Nyu0- νn is received and converted into an electrical signal.

  The electric signal converted by the light receiving element 34 is amplified by the amplifier 32, and further mixed by the mixer 37 with the signal of the local oscillator 33 that generates a frequency signal close to ν0−νn, and converted into a baseband signal. An unnecessary high-frequency signal is removed from the baseband signal converted by the mixer 37 by a low-pass filter 36, and the intensity of the Brillouin scattered light signal is obtained by an A / D (analog / digital) converter 38.

  Furthermore, by varying the local oscillator 33, an arbitrary frequency component of the BFS spectrum can be extracted. It is possible to individually monitor the Brillouin scattered light from the optical fiber line below the optical splitter by detecting the ν1 to νm frequencies which are BFS assigned in advance. Further, by measuring the Brillouin scattered light intensity with respect to the time t when the Brillouin scattered light returns, the distance L from the BOTDR can be obtained by L = 1/2 (v · t). Where v is the speed of light in the fiber.

  A method for identifying an optical fiber accommodation facility below the optical splitter using BOTDR will be described. At the connection portion 9 below the optical splitter 4, the connection / disconnection of the optical equipment occurs frequently due to the service opening / closing order, and therefore the connection is performed by the single-fiber optical connector.

At the connection point of this optical connector, a ferrule is pressed, and for example, JISC5973 specifies 7.9 to 11.8 N. The generated strain ε can be obtained from ε = δ / E, where δ is the stress and E is the Young's modulus. When the Young's modulus of glass is 7.1 × 10 ¹⁰ and the Brillouin frequency shift due to strain is 500 MHz /%, BFS fluctuation of about 450 to 680 MHz is caused. A waveform obtained by measuring this fluctuation by BOTDR is shown in FIG.

In FIG. 1 (c), the horizontal axis represents the distance, and the vertical axis represents the scattered light spectrum in the vicinity of ν1 to νm, which is the BFS assigned to the optical fibers 5 _{1 to} 5 _m , and the frequency value at which the spectrum peak was obtained. It is detected. By detecting a plus shift due to the ferrule pressing at the connection point of the optical connector, the connector connection is detected, and the presence of the optical equipment of the closure 6 or the cabinet 8 that protects the optical connector can be identified.

  In this method, since Brillouin scattered light is detected by frequency filtering, the Fresnel reflection that occurs at the connector connection point in conventional Rayleigh scattered light measurement can be suppressed and a short dead zone can be realized. Even close connection points such as a drop cable to a user home section can be individually identified.

[Embodiment 2]
FIG. 3A is a configuration explanatory view showing an optical equipment identification system according to the second embodiment of the present invention, and FIG. 3B is a characteristic diagram showing Brillouin scattered light power with respect to distance. In FIG. 3A, the same parts as those in FIG.

  As shown in FIG. 3A, an optical fiber connection point below the optical splitter 4 is provided with an extra length processing unit 14 that handles the optical fiber and processes an extra cable length. By providing the extra length processing section 14, the degree of freedom of wiring is increased, and the stress on the connection connector section caused by the pulling of the optical fiber cable after laying is reduced.

  The Brillouin scattered light measuring device 10 'detects a fluctuation in BFS occurring in an optical fiber accommodation facility such as an optical closure 6 or a cabinet 8 that covers an extra length processing unit 14 that constitutes an optical path on the branching side from the optical splitter 4. Then, the status of the accommodation facility for the optical fiber is identified.

  For example, by detecting the BFS fluctuation caused by the birefringence of a bending portion having a specified diameter provided in the middle of the optical fiber such as the extra length processing unit 14, the accommodation state of the optical fiber is identified. . In this case, the fluctuation of BFS can be detected by entering a light pulse into the optical fiber line, separating one polarization component of the generated Brillouin scattered light, and detecting the intensity change period.

When bending is applied at a predetermined constant diameter D in the extra length processing section 14, the birefringence index β is β = C (d / D) ² [rad / m] due to the internal stress of the optical fiber.
Occurs. Where C is a constant determined by the material, refractive index difference and wavelength, and d is the diameter of the optical fiber cladding. By detecting this birefringence, it is possible to detect whether or not the optical fiber is accommodated in the optical fiber line.

  FIG. 4 is an explanatory diagram showing an example of the BOTDR used in FIG. In FIG. 4, the same parts as those in FIG. The BOTDR in FIG. 4 measures the birefringence generated in the optical fiber.

That is, as shown in FIG. 4, the polarization controller 39 is inserted in the transmission path of the local light ν 0 between the optical coupler 31 ₁ and the optical coupler 31 ₃ so that the incident light to the optical coupler 31 ₃ is linearly polarized. In the bend imparting section where the birefringence is generated by the signal light incident on the optical fiber line, the polarization state of the generated Brillouin scattered light νn changes with respect to the longitudinal direction. This Brillouin scattered light νn returns to the BOTDR of the Brillouin scattered light measuring device 10 ′ and is combined with the local light ν0 by the light receiver 34. Changes. The phase difference between the linearly polarized light beams that oscillate orthogonal to each other is β · L with respect to the light transmitted through L [m], and the change in intensity is expressed by sin ² (β · L). π / β.

A method for identifying the optical fiber accommodation equipment below the optical splitter 4 will be described with reference to FIG. As shown in FIG. 3A, the connection point between the optical splitter 4 and the overhead optical fiber cables 5 _{1 to} 5 _m , the connection point between the overhead optical fiber cables 5 _{1 to} 5 _m and the drop cable 15, and the drop cable 15 At a connection point with the home cable 16 or the like, a surplus length processing unit 14 that performs surplus length processing (storage) of the bending diameter D is provided. FIG. 3B shows waveforms obtained by measuring the intensity change of the spectrum peak in the vicinity of each frequency of ν1 to νm which is BFS by BOTDR of the Brillouin scattered light measuring device 10 ′.

For example, if an optical fiber having a cladding diameter of 125 μm is installed with a bending diameter D of 60 mm and a constant C of 4.39 × 10 ⁵ [rad / m], the scattered light power level fluctuation with a period of 1.65 m occurs. By detecting this power level fluctuation period, it is possible to detect the bending accommodation state in the optical fiber line, that is, to identify that there is an optical fiber accommodation facility such as the optical closure 6 or cabinet 8 accommodating the optical fiber connection point.

  In addition, by installing the extra length processing diameter D so as to be different for each accommodation facility such as the optical closure 6, the cabinet 8, the ONU 2, etc., it is possible to identify the optical fiber accommodation facility in more detail. Furthermore, it is possible to individually identify each extra length processing unit 14 by setting the total extra length processing diameter D to be different regardless of the type of accommodation equipment of the optical fiber. Waveguide loss occurs due to bending in optical fibers, but if an optical fiber with a small mode field diameter or a hole assist fiber with an air layer in the cladding is used, a processing (storage) diameter of 1 cm or less can be assigned. Is possible.

  Note that the facility identification by this birefringence detection is an arrayed waveguide that can be designed so that the transmission wavelength band to the line below the optical splitter is different, instead of using the optical fiber assigned the Brillouin frequency below the optical splitter. A transmission wavelength λ1 to λn is assigned to the lower optical fiber using a diffraction grating (array), and the scattered light of each lower line is separated using an OTDR in which the wavelengths of λ1 to λn are variable as an optical test device. The light equipment can be similarly identified by detecting and detecting the intensity change period of the scattered light by providing the light receiving unit of the wavelength tunable OTDR with a polarizing filter or a coherent detection method in the receiving unit.

  The birefringence can also be used by applying a lateral pressure or twist to the optical fiber.

  Note that 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.

1 ... optical line termination device (OLT), 2 ... optical subscriber line network unit (ONU), 3 ... underground optical cable, 4 ... optical _{splitter, 5} 1 to 5 m _... aerial optical fiber cable, 6 ... light closure, DESCRIPTION OF SYMBOLS 8 ... Cabinet, 9 ... Connection part, 10 '... Brillouin scattered light measuring device, 11 ... Optical coupler, 13 ... User's house, 14 ... Extra length processing part, 15 ... Drop cable, 16 ... In-house cable, 17 ... Optical line equipment building, 30 ... test light source, ₃₁ 1-31 3 _... optical coupler, 32 ... amplifier, 33 ... local oscillator, 34 ... light-receiving element, 35 ... optical switch, 36 ... low-pass filter, 37 ... mixer, 38 ... A / D ( Analog / digital) converter, 39... Polarization controller.

Claims (5)

In an optical fiber line constituting an optical line including an optical branching unit, each optical fiber connected to the branching unit side from the optical branching unit uses an optical fiber having a different inherent Brillouin frequency shift, and is branched from the optical branching unit. An optical equipment identification method for identifying the accommodation equipment status of an optical fiber constituting an optical path on the part side,
An optical equipment identification method characterized by detecting a Brillouin frequency shift variation occurring in the optical fiber accommodation equipment with a Brillouin scattered light measuring device to identify the status of the optical fiber accommodation equipment.   The optical equipment identification method according to claim 1, wherein a variation in Brillouin frequency shift caused by a pressure strain applied to the optical fiber connection portion is detected.   2. The optical equipment identification method according to claim 1, wherein fluctuations in the Brillouin frequency shift caused by birefringence of a bent portion having a specified diameter given in the middle of the optical fiber are detected. Method.   4. The optical equipment identification method according to claim 3, wherein an optical pulse is incident on the optical fiber line, one polarization component of the generated Brillouin scattered light is separated, and the intensity change period is detected. . An optical fiber line constituting an optical line including an optical branching part;
Each optical fiber having a different inherent Brillouin frequency shift connected to the branching unit side from the optical branching unit,
A Brillouin scattered light measuring device that detects fluctuations in the Brillouin frequency shift that occurs in the optical fiber accommodation equipment that constitutes the optical line on the branching section side from the optical branching section,
An optical equipment identification system, wherein the Brillouin scattered light measuring device detects a change in Brillouin frequency shift generated in the optical fiber accommodation equipment to identify the status of the optical fiber accommodation equipment.

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