JP4759493B2 - Optical equipment detection method and optical equipment detection system - Google Patents

Description

  The present invention relates to a method and system for detecting or identifying optical equipment.

  The optical equipment detection system is a system for remotely detecting or identifying the optical equipment. Optical equipment includes multiple optical fiber cables that make up optical fiber lines for optical communication services, fused parts and connectors that connect optical fiber cables, optical closures that protect the connection points, or optical fiber lines. There is an optical filter provided at the far end to block test light. Patent Document 1 discloses an example of such a system.

  FIG. 11 is a diagram for explaining an existing optical equipment detection system. The system of FIG. 11 includes an OLT (Optical Line Termination) 2 and user-side transmission equipment (ONT: Optical Network Termination) 4 disposed at both ends of the optical fiber line 5, an optical termination 10 provided near the OLT 2, An optical test apparatus 15 connected to the optical termination 10 and an equipment management center 6 connected to the optical test apparatus 15 via a communication network 9 are provided. The facility management center 6 manages facility information, and includes an optical fiber line facility database 7 and an operation terminal 8 for remotely operating the optical test apparatus 15.

  The OLT 2, the optical termination 10 and the optical testing device 15 are provided in a communication facility building 1 that accommodates telecommunication facilities. The communication facility building 1 and the facility management center 6 are connected via a communication network 9. In the communication facility building 1, the optical fiber line 5 is provided with an optical branching module 11 that multiplexes and demultiplexes the test light to the optical fiber line 5 and blocks the test light to the OLT 2. The optical branching module 11 is connected to a core selection device (hereinafter referred to as FS) 16 for selecting an optical fiber core to be tested, and an optical termination 10 is formed. Is connected to the optical test apparatus 15.

  Among these, the optical fiber line 5 ′ on the OLT 2 side is connected to the communication A port of the optical branching module 11, and the optical fiber line 5 on the ONT 4 side is connected to the B port. The FS 16 is connected to the C port and D port, which are test light ports. The C port is selected when testing the optical fiber line 5 and the ONT 4 side, and the D port is selected when testing the OLT 2 side.

  The optical test apparatus 15 includes an optical measurement device 18, an FS 16 and an optical measurement device / test rack selection device (hereinafter referred to as FTES) 17 that selects the optical measurement device 18, and a test control device 19. The optical measuring device 18 includes an optical pulse tester (hereinafter referred to as OTDR) 18-1, a loss test light source 18-2, a core wire control light source 18-3, and a power meter 18-4.

  The state of the optical fiber line 5 can be monitored by inputting pulsed light from the OTDR 18-1 and measuring Rayleigh backscattered light or reflected light. The OTDR 18-1 includes a 1310, 1550 nm light source for measuring a loss at a communication optical band wavelength, and a 1650 nm light source for testing a port in a state where a communication service is provided (in-service). The test control device 19 receives a test instruction from the operation terminal 8 and transmits a test result to the equipment management center 6.

The ONT 4 that faces the OLT 2 via the optical fiber line 5 is installed in the user building 3. A termination filter 23 that transmits communication light and blocks test light to the ONT 4 is connected to the optical fiber line 5 immediately before the ONT 4 in the user building 3. As the test light blocking amount of the termination filter 23, the necessary blocking amount Lt [dB] is designed according to the system design. That is, when monitoring the optical fiber line 5 in-service, the peak power Pt [dBm] of the test light received by the ONT has a noise tolerance X of the ONT with respect to the signal peak power Ps [dBm] received by the ONT. The condition is that the power is lower than the power considered. That is, the condition is that the following expression (1) is satisfied.
Pt <Ps−X (1)
The test light blocking amount of the termination filter 23 is designed to satisfy this condition.

  This termination filter 23 is designed so as to block the test light so that the test light does not affect the ONT 4 and to generate reflection of -12 dB or more. It can be identified that it is the end. Next, a known optical equipment detection method in the above configuration will be described.

  FIG. 12 is a diagram showing measurement results in the above configuration. 12A is an OTDR waveform graph measured by connecting the OTDR 18-1 to the C port of the optical branching module 11. FIG. The vertical axis indicates the power of the return light, and the horizontal axis indicates the distance. FIG. 12B is a diagram schematically illustrating the facility information registered in advance including the distance information. When the event points X1, X2, X3, and X4 on the waveform of FIG. 12A are collated with FIG. 12B that is facility information, X1 is a connector connection, X2 is a fusion connection, and X3 is an optical fiber cable section. , X4 can obtain equipment information indicating that it is a termination filter. By using this information, for example, X3 is an optical fiber cable section, but it is possible to determine the normality / abnormality of the equipment such as a loss abnormality due to bending or the like. However, the existing techniques have the following problems [1] to [3].

[1]
The system of FIG. 11 requires a database. That is, it is impossible to detect an optical facility whose information is not registered in the database 7. If there is even one facility that is not registered, the loss or reflection that appears in the OTDR waveform may be due to the presence of a connection point, or it may be due to an abnormality due to disconnection or bending occurring in the optical fiber cable section. Cannot be identified.

  [2] Between the optical fiber cable length data at the time of registration in the database and the optical fiber cable length obtained from the actually measured OTDR waveform, by adding extra length at the connection point or twisting in the optical fiber cable Generally, a deviation occurs. Therefore, in order to accurately identify the equipment, the numerical values (connection point positions) on the database are corrected by comparing the loss / reflection points on the OTDR waveform actually measured with reference to the equipment data registered in advance. There is a need. This will be described in detail below.

  FIG. 13 is a diagram for explaining a method of correcting the connection point position of the database. Fig. 13 (a) shows the OTDR waveform obtained by conducting an optical pulse test, Fig. 13 (b) shows the length at the time of purchase of the optical fiber cable, the map distance between the facilities that provide the connection points, the connection method in the construction, etc. The connection point information and distance thrown by using are schematically shown.

  At the position of the connection point observed in the OTDR waveform of FIG. 13A, a step due to reflection or connection loss occurs at a position shifted from the connection point of FIG. Therefore, the connection point position information of the registered facility data is corrected according to the OTDR waveform as shown in FIG. Thus, a procedure for matching the OTDR waveform with the data is required. In this method, when the loss at the fusion splice point is very small, or when the splice point cannot be confirmed with the OTDR waveform due to the difference in Rayleigh scattered light level, the distance cannot be corrected, so that the equipment information can be obtained correctly. There is also a problem of not. The state where there is no step difference due to the Rayleigh scattered light level will be described in detail below with reference to FIG.

According to Non-Patent Document 1, the step of the optical fiber connection loss Ls observed in the OTDR waveform is a step obtained by combining the level difference a of the Rayleigh backscattered light of the optical fiber before and after the connection point and the true connection loss s. Measured. This is expressed by the following equation (2).
Ls = s + a (2)
When the Rayleigh scattered light level in the optical fiber behind the connection point is high and a in Expression (2) is negative, Ls is apparently small as shown in FIG. The splicing loss is 0 to 0.1 dB, the level difference of Rayleigh scattered light is about ± 0.3 dB, and when the absolute values of s and a are the same, as shown in FIG. Cancel each other. For this reason, the connection loss position cannot be confirmed with the OTDR waveform, and distance correction becomes impossible. Furthermore, since a layer of air enters the connector at the connector connection point and a very large Fresnel reflection occurs, the position of the fusion connection point is accurately determined by the skirt tail dead zone as shown in FIGS. 15 (a) and 15 (b). Therefore, it is impossible to correct the distance.

[3] Furthermore, a termination filter 23 is installed at the end of the optical fiber line so as not to affect the ONT when the optical pulse test is performed on the in-service core. However, the actual presence or absence of the termination filter 23 cannot be confirmed by an optical pulse test. To determine the presence or absence of termination filter equipment from a remote location, even if there is no blocking by the filter, the modulated light with the light power suppressed to an extent that does not affect the ONT is incident, and the termination is determined by the intensity of the reflected light in the frequency band of the modulated light The presence or absence of a filter is discriminated. However, this method has a problem in that when there is a large reflection due to a defective connector or the like in the middle of the optical fiber line, for example, a reflection point of −25 dB or more, the reflection intensity is saturated and the equipment cannot be identified.
Japanese Patent Laid-Open No. 2-1632 (especially page 4-9, FIG. 1-8) Supervised by Shinji Ishihara, “Points of 200 optical fiber technology useful in practice”, Telecommunications Association, revised edition, June 25, 2001, p. 294

As described above, in the existing technology, it is necessary to register the optical equipment in the database in advance, which requires troublesome work. In addition, there is a problem that it is necessary to correct the distance of the optical connection point, and connection point information necessary for the distance correction may not be obtained by pulse measurement. There is also a problem that the pulse test cannot be performed if the equipment database is incomplete.
This invention is made | formed by the said situation, The objective is to provide the optical equipment detection method and optical equipment detection system which can identify an optical equipment reliably irrespective of the presence or absence of registration information.

  In order to achieve the above object, according to one aspect of the present invention, in an optical equipment detection method for detecting an optical equipment provided in an optical fiber line, a place where the optical equipment is installed in the optical fiber line and the others The distortion in the optical fiber line is varied in the part, and the peak frequency of Brillouin backscattered light caused by the distortion is measured in the longitudinal direction of the optical fiber line by B-OTDR (Brillouin-OTDR), and the frequency obtained by this measurement An optical equipment detection method is provided, wherein the optical equipment is detected based on a change with respect to a shift distance.

  By taking such means, the presence or absence of distortion in the optical fiber line is measured in the longitudinal direction using Brillouin-OTDR. Optical fibers are distorted by the effects of residual stress during manufacturing. On the other hand, in an optical facility (optical closure) or the like provided in the middle, the stress is released by removing the cable jacket, so there is often no distortion. That is, the presence / absence of strain and the presence / absence of optical equipment can be associated with each other, and this is measured in association with the distance by the Brillouin shift measurement using Brillouin-OTDR. Therefore, it is possible to reliably detect or identify the light equipment without requiring a database.

  According to this invention, it is possible to provide an optical equipment detection method and an optical equipment detection system capable of reliably identifying an optical equipment regardless of the presence or absence of registration information.

[First Embodiment]
FIG. 1 is a system diagram showing a first embodiment of an optical equipment detection system according to the present invention. In FIG. 1, parts that are the same as those in FIG. 11 are given the same reference numerals, and only different parts will be described here. The optical measuring device 18 of FIG. 1 includes a B-OTDR (Brillouin-OTDR) 18-1 ′ in addition to the configuration of FIG. B-OTDR is a means for measuring the frequency and power of Brillouin backscattered light in association with the position of the optical fiber. Based on the result of this measurement, the optical equipment is detected in the optical testing device 15 or the equipment management center. Hereinafter, B-OTDR will be described in detail.

  FIG. 2 is a block diagram illustrating an example of B-OTDR. In FIG. 2, the test light source LS emits continuous light having a frequency ν 0, and the output light is branched at the mouth by the optical coupler 31-1 to generate local light and test light. Among these, the test light is pulsed through the optical switch SW and is incident on the measured fiber FB.

  The Brillouin backscattered light having the frequency shift νB generated in the splitter lower line is combined with the local light having the optical frequency ν0 previously divided by the optical coupler 31-3, and the resulting beat signal νB is received by the light receiving element 33. The In the electrical processing section at the subsequent stage of the light receiving element 33, the electrical signal output from the light receiving element 33 is amplified by the amplifier 32, and further mixed by the mixer 37 with the signal of the local oscillator 34 that generates a frequency signal close to νB. Convert to baseband signal. Unnecessary high-frequency components included in the baseband signal are removed by the low-pass filter 36, and the intensity of the Brillouin backscattered light with the frequency shift νB is obtained. This intensity information is converted into digital data by an analog / digital (A / D) converter 38, for example.

  FIG. 3 is a diagram showing the relationship between the incident test light wavelength ν0 and the Brillouin scattered light wavelength νB in FIG. As shown in FIG. 3, Brillouin backscattered light is light that has been frequency-shifted by about 10 GHz from an incident test light pulse into the optical fiber. The phenomenon in which this shifted light is generated and scattered backward (incident end direction) is Brillouin backscattering. Brillouin backscattered light has the property that the frequency shift amount changes by about 500 MHz for 1% strain of the optical fiber. Next, a method for acquiring facility information using Brillouin backscattered light measurement will be described.

FIG. 4 is a diagram showing the relationship between the details of the optical fiber line 5 and the measurement data. As shown in FIG. 4A, the optical fiber line 5 is obtained by connecting optical fiber cables 12 in series, and the connection point is protected by a storage box called an optical closure 14.
The optical fiber cable 12 is obtained by collecting and protecting optical fiber core wires subjected to primary and secondary coatings. In the optical cable portion, about 0.01% of distortion in manufacturing and tension in laying remain. On the other hand, since the optical fiber core wire is removed from the storage slot of the optical fiber cable 12 in the optical closure 14, it becomes a region where almost no distortion is applied. Therefore, when the peak frequency of the Brillouin backscattered light is measured in the longitudinal direction of the optical fiber line 5, the change in the frequency shift νB is measured according to the distance as indicated by the arrow in FIG.

  This change in the frequency shift νB corresponds to a frequency shift difference of about 5 MHz when the strain applied to the optical fiber cable is 0.01% and the strain applied to the optical fiber tape is 0%. Further, since the optical fiber portion accommodated in the optical closure 14 from the optical fiber cable 12 is the same optical fiber having no connection point, the frequency shift change is measured without the influence of the variation in the frequency shift of the Brillouin backscattered light due to the manufacture. be able to. By sampling this shift change in the longitudinal direction of the optical fiber, the installation point of the optical closure 14 can be obtained.

  The above-described change in the Brillouin backscattered light frequency νB is determined depending on whether the optical fiber core wire is outside the optical closure 14 or inside the optical closure 14. Therefore, it can be observed even when there is no step in the connection loss Ls. Therefore, it is possible to determine whether or not the location is a connection point without a previously registered database. In the above method, the connection point is identified by a frequency shift of about 5 MHz, but this can be expanded to further facilitate the identification.

  FIG. 5 is a schematic diagram showing one method for applying strain to the optical fiber tape. For example, the frequency shift of the Brillouin backscattered light frequency νB can be expanded by bending the optical fiber tape and applying strain within the elastic limit range. That is, in the optical closure 14, the optical fiber tape 13 is distorted within a range of 0.2% which is the elastic limit of the optical fiber.

  For example, the extra length of the optical fiber tape 13 is accommodated in the optical closure 14, and the optical fiber tape 13 is wound around at least a radius of 30 mm (diameter 60 mm or more) in order to eliminate the influence of loss due to bending. Then, for example, the core material 100 that has been wound is widened by 0.05% to give a tensile strain of 0.05%, or is wound so that the above-described strain is generated.

A frequency shift of 25 MHz is caused by applying a tension that gives a tensile strain of 0.05% to the optical fiber core over about 1 m in the optical closure 14, and the frequency shift of the optical closure 14 is observed by observing this frequency shift. The installation point can be identified more easily. At this time, assuming that the diameter of the optical fiber is 125 μm and the Young's modulus of the optical fiber is 7.3 × 10 ¹⁰ Pa (73 gigapascal), a stress of 0.45 N (Newton) is applied to the optical fiber to achieve 0.05%. Distortion can be caused.

  The Brillouin frequency shift νB is determined by the concentration of the additive contained in the optical fiber core, and it is possible to change the Brillouin frequency shift of about 100 MHz with a single mode fiber. Therefore, for example, by using the optical fiber cables 12 having different Brillouin frequency shifts before and after the connection point, the connection point can be identified without affecting the optical communication line. Examples of the material added to the optical fiber core include germanium oxide, fluorine, phosphorus oxide, aluminum oxide, and boron oxide.

  Further, even when the Brillouin frequency shifts νB of the optical fiber cables 12 before and after the connection point are equal, optical fibers (single mode fibers) having different concentrations of additives contained in the core are connected to the connection point in the optical closure 14. For example, the connection point can be identified by pinching by fusion. At this time, it is preferable to limit the difference in mode field diameter of the optical fiber sandwiched so as not to affect the optical communication line, and to suppress the connection loss to, for example, 0.5 dB or less.

  In the Brillouin scattered light measurement in this embodiment, only the beat signal is observed as described in the B-OTDR configuration. Therefore, Fresnel reflected light that does not cause frequency shift can be separated, and there is an advantage that connection loss can be measured in a very small dead zone. For example, if a connector connection point with a return loss of 40 dB is measured with test light having a pulse width of 100 ns (nanoseconds), the distance to the point where the tailing of the reflected waveform is within ± 0.1 dB of the backscattered light level steady value. In OTDR, about 100 m is required. On the other hand, since the reflected waveform is not generated in the B-OTDR of this embodiment, even if the connection point is close to about 10 m, these can be individually identified.

[Second Embodiment]
FIG. 6 is a system diagram showing a second embodiment of the optical equipment detection system according to the present invention. In FIG. 6, parts that are the same as those in FIGS. 1 and 11 are given the same reference numerals, and only different parts will be described here. In the system of FIG. 6, the termination filter 23 of FIG. 1 is omitted. Further, the optical measuring device 18 of FIG. 6 is obtained by replacing the OTDR 18-1 of FIG. 11 with a coherent OTDR (C-OTDR) 18-1 ″. The C-OTDR 18-1 ″ has a coherent detection reception function.

  When the termination filter 23 is not present before the ONT 4, the peak power Pt [dB] of the optical pulse from the OTDR that reaches the ONT 4 is not attenuated by the termination filter 23. Therefore, in order to perform the pulse test without affecting the in-service cord, it is necessary to lower Pt by Lt [dB] corresponding to the cutoff amount of the termination filter 23. The necessary cutoff amount of the termination filter 23 is determined for each communication service, and is about 20 to 40 dB. If the input power of OTDR is simply lowered by Lt, the dynamic range measurable by OTDR is reduced by Lt / 2 [dB].

  The termination filter 23 generally generates a reflection of −12 dB or more in order to determine whether it is immediately before the user transmission device, that is, the far end of the optical fiber line 5. The normal open end is -14.5 dB. The difference between the reflected light intensity and the Rayleigh scattered light intensity is about 50 dB. When the OTDR pulse light output power is lowered by Lt [dB] in consideration of the absence of the optical filter, the presence or absence of the termination filter can be confirmed even in the conventional OTDR configuration as long as the termination filter is only reflected or not. However, in order to obtain the connection point data of the optical fiber, it is necessary to confirm the power level of the Rayleigh scattered light.

  FIG. 7 is a block diagram illustrating an example of C-OTDR. In FIG. 7, the test light source LS emits coherent light having a frequency ν 0, and the output light is branched at the mouth by the optical coupler 31-1 to generate local light and test light. Among these, the test light is pulse-modulated by the frequency shifter 39 and is incident on the measured fiber FB. The backscattered light from the optical fiber to be measured is combined with the local light having the optical frequency ν0 by the optical coupler 31-3, and the beat signal νc is received by the light receiving element 33. In the electrical processing section at the subsequent stage of the light receiving element 33, the electrical signal output from the light receiving element 33 is amplified by the amplifier 32, and further mixed with the signal of the local oscillator 34 that generates a frequency signal close to νc by the mixer 37. Convert to baseband signal. Unnecessary high-frequency components included in the baseband signal are removed by the low-pass filter 36, and the intensity of the backscattered light having the frequency shift νc is obtained. This intensity information is converted into digital data by an analog / digital (A / D) converter 38, for example.

  According to the coherent system, it is possible to obtain a reception sensitivity that is about 20 dB or more higher than the reception sensitivity of the normal direct detection OTDR. In order to perform an in-service test on the optical fiber line of the access system, the termination filter 23 blocks the test light by 20 dB or more. If an in-service test is performed using C-OTDR, the test can be performed regardless of whether or not the termination filter equipment is installed, and the pulse waveform can be measured with a dynamic range equivalent to that of the conventional OTDR. .

The optical characteristics of termination filters used in actual lines include the following types (a) and (b).
(A) Type: Transmits in the 1310 wavelength band or less, and blocks and reflects the 1550 nm band or more.
(B) Type: Transmits below the 1550 wavelength band and blocks / reflects the 1650 nm band.

In order to confirm these installation conditions or no installation, a C-OTDR having a light source that outputs test light in the 1310 nm band, 1550 nm band, and 1650 nm band is installed, and a termination filter is used using each wavelength. The presence / absence of large reflection of −12 dB or more required for the pulse waveform is acquired from the pulse waveform. Based on the result, equipment information can be obtained as in 1) to 3) below.
1) No reflection in any of the 1310 nm band, 1550 nm band, and 1650 nm band: No filter.
2) When there is reflection in the 1550 nm band and the 1650 nm band: (a) A type filter is installed.
3) When there is reflection only in the 1650 nm band: (b) A type filter is installed.

  FIG. 8 is a diagram for explaining the height of reflection by the termination filter. In the pulse waveform of FIG. 8, the solid line is a pulse waveform when there is a reflection of −12 dB or more at the end. The reference point 0 of the reflection amount is generally obtained from the pulse width and the Rayleigh scattered light level during the optical pulse test. A broken line is a pulse waveform when there is no filter at the far end of the optical line or when a wavelength that is a transmission wavelength band of termination is used. If the waveform is obtained when the pulse test is performed with the solid line at 1650 nm and the dotted line at 1550 nm, it can be seen from FIG. 8 that the (b) type filter is installed at the far end.

  In this embodiment, when the termination filter facility is confirmed, the return light power from the optical fiber line 5 can be monitored in the distance direction in the same manner as the optical pulse waveform. Therefore, even if a large reflection occurs in the middle of the optical fiber line 5, it is possible to distinguish this reflection from the reflection amount of the termination filter installed at the far end.

[Third Embodiment]
FIG. 9 is a system diagram showing a third embodiment of the optical equipment detection system according to the present invention. The system of FIG. 9 includes B-OTDR 18-1 ′ and C-OTDR 18-1 ″ in the optical measuring device 18.
FIG. 10 is a flowchart showing a processing procedure in the optical equipment detection system of FIG. That is, FIG. 9 shows an automatic database for obtaining the optical fiber line equipment data of the optical fiber line 5 according to the present invention for automatically performing the optical line test by the system of FIG. 9 without the pre-registered optical equipment database. The construction procedure is shown.

  In FIG. 10, the power meter 18-4 is connected to the test ports C and D of the optical branching module 11 inserted in the optical fiber line, and the optical power is measured to confirm the presence or absence of communication light (step S1). This is because a test for identifying an optical fiber line is first performed for the purpose of confirming the service implementation status so as not to affect the in-service core in the absence of equipment data.

  If there is communication light, the presence / absence of the termination filter 23 is determined so as not to affect communication by the method of the second embodiment (step S2). If it is determined in step S1 that there is no communication light, or if it is determined in step S2 that the termination filter 23 is installed in front of the user-side transmission device 4, the input test optical power is limited. Can be tested. Therefore, next, the position of the optical closure is confirmed under the technique of the first embodiment by the optical equipment detection system including the B-OTDR 18-1 ′ (step S4). After that, if a loss test is performed by the conventional OTDR, if there is a termination filter 23, the position of the termination filter 23, the installation position of the optical closure 14, the connection loss at the optical closure 14, the fusion of the connection points or the connector connection The optical fiber line equipment data relating to the discrimination is obtained (step S5). Based on this, it is possible to determine the quality of the optical equipment at each connection point.

  Even when it is determined that there is communication light and no optical filter, by performing a pulse test by C-OTDR (step S3), an OTDR waveform equivalent to the conventional one is used so as not to affect the communication state. It is possible to obtain.

  Conventional methods for identifying optical fiber line equipment include information such as the length of the optical fiber cable constituting the optical fiber line, means such as fusion and connector for connecting the optical fiber cable, and the accommodation status of the connection point in advance. It was determined by manually collating database information with loss and reflection positions that are stored in a database and measured when an optical pulse test described later is performed.

  On the other hand, in the first embodiment, the strain applied to the optical fiber in the optical closure 14 is made different from the strain applied to the optical fiber in the optical fiber line 5, and the optical fiber line is made using B-OTDR. The position of the light closure 14 is identified by detecting the frequency difference between the Brillouin backscattered light generated at 5 and the Brillouin backscattered light generated at the optical closure 14. As a result, the presence or absence of the connection point of the optical fiber of the optical fiber line 5 can be accurately measured in the optical test from the station without the equipment data prepared in the database in advance. Further, even when the connection point in the middle of the optical fiber line 5 is close to the connector connection point, the position of the connection point of the optical fiber line 5 can be accurately measured without using the pre-registration information of the line data. become. Further, the connection point of the optical fiber line 5 can be detected even when the step due to the connection loss does not occur at the connection point in the middle of the optical fiber line. In the case where a failure occurs at a connection point, these repairs the connection point, so that the installation location of the failed connection point can be specified reliably, and the maintenance operation can be reduced.

In the second embodiment, C-OTDR (coherent OTDR) is used, and the presence or absence of the optical filter at the far end of the optical fiber line is identified in-service by its high sensitivity. Furthermore, in the third embodiment, the techniques of the first and second embodiments are combined so that the presence / absence and type of the termination filter 23 and the optical equipment based on the result can be identified. Therefore, the presence or absence of the termination filter 23 can be remotely identified without being affected by the presence or absence of the database.
Accordingly, it is possible to provide an optical equipment detection method and an optical equipment detection system that can reliably identify an optical equipment regardless of the presence or absence of registration information.

  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. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a system diagram showing a first embodiment of an optical equipment detection system according to the present invention. The block diagram which shows an example of B-OTDR. The figure which shows the relationship between the incident test light wavelength (nu) 0 in FIG. 2, and the Brillouin scattered light wavelength (nu) B. The figure which shows the relationship between the detail of the optical fiber line 5, and measurement data. The schematic diagram which shows one method to give distortion to an optical fiber tape. The system diagram which shows 2nd Embodiment of the optical equipment detection system which concerns on this invention. The block diagram which shows an example of C-OTDR. The figure explaining the height of reflection by a termination filter. The system diagram which shows 3rd Embodiment of the optical equipment detection system which concerns on this invention. The flowchart which shows the process sequence of the optical equipment detection method which concerns on this invention. The figure for demonstrating about the existing optical equipment detection system. The figure which shows the measurement result in the system of FIG. The figure for demonstrating the method of correct | amending the connection point position of a database. The figure for demonstrating the loss level | step difference produced in the fusion splicing point of an optical line. The figure explaining that a loss point becomes impossible to measure by the dead zone of a Fresnel reflection point in an optical pulse waveform.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Communication equipment building, 2 ... OLT, 3 ... User building, 4 ... ONT, 5 ... Optical fiber line, 6 ... Equipment management center, 8 ... Operation terminal, 9 ... Communication network, 10 ... Optical termination, 11 ... Optical branch module, 12 ... optical fiber cable, 13 ... optical fiber tape, 14 ... optical closure, 15 ... optical test device, 16 ... FS, 17 ... FTES, 18 ... optical measuring device, 18-1 '... B-OTDR, 18-1 "... C-OTDR, 19 ... Optical test control device, 20 ... Fusion splice point, 23 ... Termination filter, 31-1, 31-2, 31-3 ... Optical coupler, 32 ... Amplifier, 33 ... Light receiving element 34 ... Local oscillator 36 ... Low pass filter 37 ... Mixer 38 ... A / D converter 39 ... Frequency shifter 100 ... Core material LS ... Test light source SW ... Optical switch FB ... Measured light fiber

Claims (10)

In an optical equipment detection method for detecting optical equipment provided in an optical fiber line for optical communication services,
Where the optical equipment in the optical fiber line is installed and other parts, the distortion in the optical fiber line is different,
The peak frequency of Brillouin backscattered light caused by the distortion is measured in the longitudinal direction of the optical fiber line by B-OTDR (Brillouin-OTDR),
An optical equipment detection method, comprising: detecting the optical equipment based on a change in frequency shift distance obtained by this measurement.   The optical equipment detection method according to claim 1, wherein the optical equipment is identified based on the value of the frequency shift.   The optical equipment detection method according to claim 1, wherein the optical fiber line at the location is distorted by winding the optical fiber line around a core material at the location where the optical equipment is installed.   The optical equipment detection method according to claim 3, wherein a tensile strain is applied to the optical fiber line by expanding a diameter of a core member around which the optical fiber line is wound.   The optical equipment detection method according to claim 3, wherein the optical equipment is an optical closure, and an optical fiber line wound around the core member is housed in the optical closure. In an optical equipment detection method for detecting a termination filter provided in an optical fiber line for an optical communication service,
The intensity of the backscattered light of the test light incident on the optical fiber line is measured by C-OTDR (Coherent-OTDR),
The pulse light output power Pt of the test light is lowered by the cutoff amount Lt in the termination filter,
An optical equipment detection method comprising: detecting the termination filter based on the intensity obtained by this measurement. Perform measurement by the C-OTDR using a plurality of test lights having different wavelength bands,
The optical equipment detection method according to claim 6, wherein the presence / absence of the termination filter and the type of the termination filter are detected based on the result of the measurement . Determine the presence or absence of communication light by measuring the optical power in the optical fiber line,
If there is the communication light, determine the presence or absence of the termination filter by the optical equipment detection method according to claim 7,
If there is the termination filter, the optical equipment detection method according to claim 1 is implemented,
If there is no said termination filter, the optical equipment detection method of Claim 6 is implemented, The optical equipment detection method characterized by the above-mentioned . In an optical equipment detection system for detecting optical equipment installed in an optical fiber line for optical communication services,
Measuring means for measuring a peak frequency of Brillouin backscattered light caused by distortion in the optical fiber line in the longitudinal direction of the optical fiber line by B-OTDR (Brillouin-OTDR);
Detecting means for detecting the optical equipment based on a change with respect to a distance of a frequency shift obtained by the measurement, and a difference in the distortion in a portion where the optical equipment is installed in the optical fiber line and the other portion; An optical equipment detection system comprising: In an optical equipment detection system for detecting a termination filter provided in an optical fiber line for optical communication services,
A plurality of test lights having different wavelength bands, the pulsed light output power Pt is lowered by the cutoff amount Lt in the termination filter and is incident on the optical fiber line, and the intensity of the backscattered light of the test light is determined as C-OTDR (Coherent -OTDR), a measuring means for measuring,
An optical equipment detection system that detects the presence / absence of the termination filter and the type of the termination filter, if any, based on the measurement result.

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