JP6024634B2 - Optical line fault detection device and optical line fault detection method - Google Patents

Description

  TECHNICAL FIELD The present invention relates to an optical line failure detection apparatus and an optical line failure detection method, and in particular, in a subscriber system, a WDM-PON (Wavelength Division Multiplexing Passive Optical Optical) using an OTDR (Optical Time Domain Reflectometer) test method. The present invention relates to an optical line failure detection apparatus and an optical line failure detection method for a system.

  There is a WDM-PON (Wavelength Division Multiplex-Passive Optical Network) as a technique for realizing high-speed, large-capacity and low-cost optical communication systems that are wired communication. This makes it possible to provide high-speed communication of 10 Gbps or more to one user by assigning different optical wavelengths to each of the ONUs (Optical Network Units) which are optical line terminating devices on the user side. Further, by applying a branching unit (wavelength division multiplexing (WDM) device) between the ONU and an OLT (Optical Line Terminal) which is a terminating device on the carrier side, the optical fiber accommodation efficiency can be increased.

  In order to maintain and manage the quality and reliability of such WDM-PON, an optical line fault detection device that detects a line fault in an optical fiber is described in Patent Document 1.

  The optical line failure detection device described in Patent Document 1 is an optical line failure detection device that detects a failure in an optical line of a WDM-PON system. As shown in FIG. 8, the WDN-PON system includes a telephone station side optical line terminator (10), a fixed wavelength demultiplexing branching unit (15), and subscriber side optical line terminators (161 to 16n). And have.

  The telephone station side optical line terminator (10) combines signal lights having different wavelengths and enters one end of the common optical fiber line (17), and is sent via the common optical fiber line. Light is separated for each wavelength and received. The fixed wavelength demultiplexing type branching device (15) is connected to the other end of the common optical fiber line, receives the signal light transmitted from the telephone station side optical line terminator (10), and according to the wavelength. It separates and injects into the end of the individual optical fiber track | line (181-18n) separately provided with the different length for every wavelength. On the other hand, the branching device (15) combines the signal lights transmitted through the individual optical fiber lines and outputs them to the common optical fiber line. The subscriber side optical line terminators (161 to 16n) are respectively connected to the other end sides of the individual optical fiber lines.

  The optical line fault detection device (20) described in Patent Document 1 includes a line coupler (21), a broadband optical pulse generation means (22), a coupler (23), a light receiver (25), and a time waveform acquisition. Means (27), reference waveform storage means (28), and fault detection means (29) are provided.

  The line coupler (21) is connected to the common optical fiber line. The broadband optical pulse generating means (22) generates a broadband optical pulse including the wavelengths of all signal lights transmitted through the common optical fiber line. The broadband optical pulse generating means (22) causes the broadband optical pulse to enter during the communication stop period of the WDM-PON system. The coupler (23) receives the broadband optical pulse on the first optical path, emits it from the second optical path, and enters the WDM-PON system via the line coupler (21). In addition, the return light returned from the WDM-PON system to the line coupler in response to the incidence of the broadband optical pulse is received by the second optical path and emitted to the third optical path. The light receiver (25) receives the return light emitted from the third optical path of the coupler and converts it into an electrical signal having an amplitude corresponding to the intensity. The time waveform acquisition means (27) acquires the time waveform of the signal output from the light receiver until a predetermined time elapses from the timing when the broadband optical pulse is incident on the WDM-PON system. The reference waveform storage means (28) stores a time waveform acquired in advance when the WDM-PON system is operating normally as a reference waveform. The fault detection means (29) compares the time waveform newly acquired by the time waveform acquisition means with the reference waveform and searches for a fault in the WDM-PON system.

  By adopting such a configuration, even if the number of branches of the WDM-PON system is enormous, failure detection can be performed in a short time in the measurement time for one line.

JP 2011-035598 A

  In the related optical line failure detection apparatus described above, the wavelength band of the broadband light source overlaps with the transmission wavelength of the transmitter / receiver included in the telephone station side optical line termination device (10). Therefore, the same wavelength component in the wideband pulse becomes noise for the transceiver, and hinders communication in the WDM-PON system.

  For this reason, in Patent Document 1, a failure detection test using a broadband optical pulse is performed during a communication suspension period of the WDM-PON system. However, when the number of subscribers increases and the number of subscriber-side optical line terminators increases, there is a problem that the communication stop period is shortened and it is difficult to secure a time zone for performing a failure detection test.

  As described above, the related optical line failure detection apparatus has a problem that it is difficult to collectively perform a failure detection test for all bands regardless of the configuration of the WDN-PON system.

  The object of the present invention is that the related optical line fault detection device, which is the above-mentioned problem, is difficult to perform fault detection tests for all bands at once regardless of the configuration of the WDN-PON system. An object of the present invention is to provide an optical line failure detection device and an optical line failure detection method that solve the problem.

  The optical line fault detecting device of the present invention includes a broadband pulse generating means for generating a broadband optical pulse including all the wavelengths of signal light used in the WDM-PON system, and a wavelength component corresponding to the wavelength of the signal light from the broadband optical pulse. From the return light from the WDM-PON system including the first wavelength selector that outputs the removed broadband inspection light, the optical splitter that introduces the broadband inspection light into the WDM-PON system, and the broadband inspection light and the signal light A second wavelength selector that removes the signal light and outputs it as return inspection light, and a return inspection light processing unit that converts the return inspection light into an electrical signal and compares the electrical signal with a reference electrical signal.

An optical line fault detection system according to the present invention includes a WDM- PON including a station side optical line terminator, an optical fiber line, a fixed wavelength splitter, a subscriber side optical line terminator, and a narrowband transmission optical filter. System, broadband pulse generating means for generating broadband optical pulses including all the wavelengths of signal light used in WDM- PON systems, and broadband inspection light from which wavelength components corresponding to the wavelength of the signal light are removed from the broadband optical pulses A first wavelength selector, an optical splitter for introducing broadband inspection light into the WDM-PON system, and removing signal light from the return light from the WDM-PON system including the broadband inspection light and signal light, and returning An optical line fault having a second wavelength selector that outputs as inspection light, and a return inspection light processing unit that converts the return inspection light into an electric signal and compares the electric signal with a reference electric signal. And a sensing device, narrow band pass optical filter located in front of the subscriber optical network unit, by transmitting the signal light and blocks the broadband inspection light.

  The optical line fault detection method of the present invention generates a broadband optical pulse including all wavelengths of signal light used in a WDM-PON system, and removes a wavelength component corresponding to the wavelength of the signal light from the broadband optical pulse. The light is generated, the broadband inspection light is introduced into the WDM-PON system, the return inspection light is generated by removing the signal light from the return light from the WDM-PON system including the broadband inspection light and the signal light, and the return inspection light is generated. Is converted into an electric signal, and the electric signal and the reference electric signal are compared.

  According to the optical line fault detection device of the present invention, the fault detection test can be performed collectively for all bands regardless of the configuration of the WDN-PON system.

It is a block diagram which shows the structure of the optical line fault detection apparatus by embodiment of this invention. It is a figure which shows the reflection spectrum of FBG with respect to a signal light wavelength. (A) It is a figure which shows the wavelength spectrum of the broadband optical pulse Pw radiate | emitted from the broadband optical pulse generation means 22. FIG. (B) It is a figure which shows the wavelength spectrum of the broadband optical pulse Pw 'with which the signal wavelength (lambda) k after 1st FBG101w transmission was lose | deleted. (C) It is a figure which shows the wavelength spectrum of the incident light Pw '' to the fixed wavelength splitter 15. FIG. 6 is an enlarged view of the vicinity of a wavelength λi (i = 1 to n) of a wavelength spectrum of incident light Pw ″ entering the fixed wavelength splitter 15. (A) It is the figure which showed the wavelength spectrum after permeate | transmitting the splitter 15 for every optical fiber line 18k (k = 1-n). (B) It is a figure which shows the wavelength spectrum of the return light Pr from the WDM-PON system 1. FIG. It is a figure which shows the return light Pr 'wavelength spectrum after 2nd FBG101r transmission. It is a figure which shows the time waveform which a time waveform acquisition means acquires, (a) is a figure which shows the time waveform for every optical fiber line, (b) is a figure which shows a final time waveform. It is a block diagram which shows the structure of the related optical line fault detection apparatus.

  Hereinafter, an optical line fault detection device according to an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of an optical line failure detection apparatus 20 used in a WDM-PON system according to an embodiment of the present invention.
An optical line fault detection device according to an embodiment of the present invention includes broadband optical pulse generation means, a first wavelength selector, an optical branching device, a second wavelength selector, and a return inspection light processing unit.
The broadband optical pulse generating means generates a broadband optical pulse including all the wavelengths of signal light used in the WDM-PON system. The first wavelength selector outputs a broadband inspection light obtained by removing a wavelength component corresponding to the wavelength of the signal light from the broadband light pulse. The second wavelength selector removes the signal light from the return light from the WDM-PON system including the optical branching device for introducing the broadband inspection light into the WDM-PON system, and the broadband inspection light and the signal light, and returns the inspection. Output as light. The return inspection light processing unit converts the return inspection light into an electric signal, and compares the electric signal with the reference electric signal.

  In the optical line fault detection device according to the embodiment of the present invention, the return inspection light processing unit includes a light receiver, an analog / digital converter, a time waveform acquisition unit, a reference waveform storage unit, and a fault detection unit. Prepare.

  The light receiver outputs a voltage corresponding to the light intensity of the return inspection light. The analog / digital converter converts the voltage into a digital voltage signal. The time waveform acquisition means stores a reference waveform that is a waveform of a reference electric signal for acquiring a time change of the digital voltage signal until a predetermined time elapses after the broadband optical pulse enters the WDM-PON system. The failure detection means compares the time change of the digital voltage signal with the reference waveform.

  Further, the reference waveform storage means of the optical line fault detection device of the present invention stores, as a reference waveform, a time change of the voltage determined to be substantially the same as a result of the fault detection means comparing the time change of the voltage with the reference waveform.

  In the WDM-PON system 1, the number of wavelengths n of the signal light transmitted from the OLT (station side optical network unit) 10 is about 24, for example. The signal light wavelength λk (k = 1 to n) is λ1 = 1530.33 nm, λ2 = 1553.90 nm, λ24 = 1567.13 nm, and extends to the C band and the L band. The wavelength interval is about 1.6 nm (frequency interval 200 GHz). The signal light complies with ITU-T grid, which is a standard in the communication field.

  The broadband optical pulse Pw including the signal light wavelength λk emitted from the broadband optical pulse generating means 22 is incident on the first wavelength selector 102w. The first wavelength selector 102w includes a first optical isolator 100w and a first FBG (Fiber Bragg Grating) 101w.

  The broadband optical pulse Pw incident on the first wavelength selector 102w passes through the optical isolator 100w and is incident on the first FBG 101w. The first FBG 101w has a structure in which the refractive index periodically changes in the longitudinal direction of the optical fiber, and totally reflects a specific wavelength according to the grating period interval width. The first FBG 101w is configured to totally reflect all the signal light wavelengths λk (k = 1 to n). For this reason, the broadband optical pulse after passing through the FBG 101w becomes the broadband optical pulse Pw 'in which the signal light wavelength λk is lost. The first optical isolator 100w blocks the reflected light from the first FBG 101w. As a result, it is possible to prevent the reflected light from entering the broadband optical pulse generating means 22 and having an adverse optical effect.

  The broadband optical pulse Pw ′ lacking the wavelength λk after passing through the first FBG 101w is incident on the optical circulator 23, which is an optical coupler. The optical circulator 23 is connected to the first optical path, the second optical path, and the third optical path.

  The broadband optical pulse Pw ′ lacking the signal light wavelength λk after passing through the first FBG 101 w enters the first optical path of the optical circulator 23 and exits from the second optical path of the optical circulator 23 connected to the WDM-PON system 1. .

  The broadband optical pulse Pw ′ emitted from the second optical path of the optical circulator 23 is incident on the WDM-PON system 1 via the optical splitter 21 which is an optical coupler. Separately, signal light transmitted from the station-side optical line terminator 10 also enters the optical splitter 21. The WDM-PON system 1 includes an OLT (station side optical line terminator) 10, optical fiber lines 181 to 18n, a fixed wavelength branching unit 15, ONUs (subscriber side optical line terminators) 161 to 16n, A band-transmitting optical filter.

  The broadband optical pulse Pw ′ incident on the WDM-PON system 1 and the signal light of the WDM-PON system 1 are incident on the fixed wavelength splitter 15. The fixed wavelength splitter 15 includes n ports 1 to n. In the fixed wavelength splitter 15, incident light is separated for each wavelength and emitted from the corresponding ports 1 to n. The separated broadband optical pulses and signal light emitted from the ports 1 to n enter the ONU 16 through the corresponding optical fiber lines 181 to 18n, respectively.

  In addition, the input part of ONU16k can be equipped with the narrow-band transmission optical filter which interrupts | blocks so that the broadband optical pulse used as a noise component may not be input into ONU16k. The narrow-band transmission optical filter is a filter that transmits only the signal light wavelength λk. By adopting such a configuration, it is possible to prevent the broadband optical pulse from hindering communication between the OLT 10 and the ONUs 161 to 16n.

  When the broadband optical pulse and the signal light separated to the ONUs 161 to 16n arrive, return light as reflected light propagates in the reverse direction. The return light from each of the ONUs 161 to 16n enters the fixed wavelength splitter 15 from the ports 1 to n through the corresponding optical fiber lines 181 to 18n. In the fixed wavelength splitter 15, the return lights are combined into one and propagated as return light Pr. In addition, return light is also generated by Fresnel reflection of broadband light pulses or signal light at connection points or break points of the branching device 15 or the common optical fiber line 17. These are also combined into one at the place where they are generated and become return light Pr.

  The return light Pr enters the second optical path of the optical circulator 23 via the optical splitter 21. The return light Pr that has entered the second optical path of the optical circulator 23 exits from the third optical path of the optical circulator 23.

  The return light Pr emitted from the third optical path of the optical circulator 23 enters the second wavelength selector 102r. The second wavelength selector 102r includes a second optical isolator 100r and a second FBG 101r.

  The return light Pr that has entered the second wavelength selector 102r passes through the second optical isolator 100r and enters the second FBG 101r. Similar to the first FBG 101w, the second FBG 101r is configured to totally reflect all the signal light wavelengths λk (k = 1 to n). The second FBG 101r removes the return light (wavelength λk) corresponding to the signal light emitted from the station side optical network unit 10. The second optical isolator 100r blocks the reflected light from the second FBG 101r. Thereby, it is possible to prevent the reflected light from adversely affecting the broadband optical pulse generating means 22.

  The return inspection light Pr 'lacking the wavelength λk after passing through the second FBG 101r is incident on the return inspection light processing unit 200. The return inspection light processing unit 200 includes a light receiver 25 that outputs a voltage corresponding to the light intensity of the return inspection light, an analog / digital converter 26 that converts an analog voltage signal into a digital voltage signal, and a broadband optical pulse that is WDM−. A time waveform acquisition means 27 for acquiring a time change in voltage until a predetermined time elapses after entering the PON system 1, a reference waveform storage means 28 for storing a reference waveform which is a waveform of a reference electrical signal, Fault detection means 29 for comparing the time variation of the voltage with the reference waveform is provided.

  FIG. 2 is a diagram showing a reflection spectrum of the FBG with respect to one signal light wavelength λk. The vertical axis represents the reflected light power, and the horizontal axis represents the wavelength (nm).

  As shown in FIG. 2, the FBG exhibits high reflected light intensity due to total reflection in the vicinity of the signal light wavelength λk, and the wavelength band far from the wavelength λk has a reflection amount of 0 and has a reflection spectrum that transmits all. In order to totally reflect only the signal light wavelength λk, it is desirable that the reflection spectrum is steep. On the other hand, the signal light wavelength λk from the transceiver in the OLT 10 varies by about λk ± 0.1 nm depending on environmental conditions such as temperature. Therefore, the reflection wavelength bandwidth (full width at half maximum) of the FBG is set to, for example, 0.3 nm (λk ± 0.15 nm). With such a configuration, it is possible to prevent the signal light and the broadband optical pulse from being superimposed in the common optical fiber line 17.

  3 to 6 show the wavelength spectrum at each main point in FIG. 1, and the light intensity on the vertical axis is arbitrary, and is described without considering the passage loss of each component.

  FIG. 3A shows the wavelength spectrum of the broadband optical pulse Pw emitted from the broadband optical pulse generator 22. FIG. 3B is a diagram showing the wavelength spectrum of the broadband optical pulse Pw ′ in which the signal wavelength λk after transmission through the first FBG 101w is lost. FIG. 3C is a diagram illustrating a wavelength spectrum of the incident light Pw ″ entering the fixed wavelength splitter 15. In either case, the vertical axis represents the light intensity, and the horizontal axis represents the wavelength.

  The broadband optical pulse Pw ′ shown in FIG. 3B enters the WDM-PON system 1 via the optical splitter 21. The incident light Pw ″ to the fixed wavelength splitter 15 shown in FIG. 3C is a combination of the broadband optical pulse Pw ′ and the signal light. Since the signal wavelength λk is lost in the broadband optical pulse Pw ′ by the first FBG 101 w, the signal light is located in the missing part of the broadband optical pulse Pw ′. That is, the broadband light pulse Pw ′ and the signal light do not overlap.

  A dotted line shown in FIG. 3C is a transmission wavelength band of n ports 1 to n included in the fixed wavelength splitter 15. As the fixed wavelength splitter 15, an AWG (Arrayed Waveguide Grating) is used. The AWG has a feature that a large number of signal lights can be wavelength-demultiplexed with low loss. The transmission wavelength of the fixed wavelength splitter 15 is the same 24 waves as the signal light, and conforms to ITU-T grid, and the passage loss is 4 dB or less.

  FIG. 4 is an enlarged view in the vicinity of the wavelength λi (i = 1 to n) of the wavelength spectrum of the incident light Pw ″ entering the fixed wavelength splitter 15. The vertical axis represents light intensity, and the horizontal axis represents wavelength.

  The dotted line shown in FIG. 4 is the transmission wavelength band of the port i included in the fixed wavelength splitter 15. By ensuring that the transmission wavelength bandwidth after wavelength separation of the fixed wavelength splitter 15 is 1 nm (λi ± 0.5 nm) at full width half maximum and the crosstalk of adjacent wavelengths (λi−1, λi + 1) is 25 dB or more, the adjacent signal light (Wavelengths λi−1, λi + 1) are blocked, and only the signal light wavelength λi and a broadband optical pulse in the vicinity thereof are transmitted to the optical fiber line 18i. The wavelength spectrum of the optical signal propagating through the optical fiber line 18i is limited by the transmission wavelength band of the port i included in the fixed wavelength splitter 15 indicated by the dotted line, and has a shape having peaks on both sides of the individual signal light wavelength λi. (Dotted line inside).

  FIG. 5A is a diagram showing the wavelength spectrum after passing through the branching device 15 for each optical fiber line 18k (k = 1 to n).

  As shown in FIG. 5A, both the corresponding signal light (wavelength λk) and a part of the broadband optical pulse (near the wavelength λk) propagate through the optical fiber line 18k (k = 1 to n). To do. For this reason, it is possible to detect a failure in the individual optical fiber line 18k while maintaining communication between the OLT 10 and the ONUs 161 to 16n.

  FIG. 5B is a wavelength spectrum of the return light Pr from the WDM-PON system 1. The vertical axis represents light intensity, and the horizontal axis represents wavelength.

  FIG. 6 is a diagram showing the wavelength spectrum of the return inspection light Pr ′ after passing through the second FBG 101r. The vertical axis represents light intensity, and the horizontal axis represents wavelength.

  The return light of the signal light wavelength λk is asynchronous with the broadband optical pulse generating means 22 and hinders detection of the time waveform by the time waveform acquisition means 27 at the subsequent stage. For this reason, the FBG 101r removes the return light (wavelength λk) of the signal light wavelength.

  As described above, the wavelength spectrum at the main points in FIG. 1 has been described. However, when viewed on the time axis, the broadband light pulse Pw generated from the broadband light pulse generating means 22 is Fresnel reflected at the connection point or break point to become return light, The time waveform acquisition means 27 acquires the relationship between the time (distance) reaching the light receiver 25 to the return inspection light processing unit 200 and the received light power as a time waveform. The return light Pr ′ reaching the return inspection light processing unit 200 becomes an optical pulse having two light intensity peaks in the vicinity of the signal light wavelength λk (k = 1 to n) as shown in FIG.

  FIG. 7 is a diagram showing a time waveform acquired by the light stealing means, and (a) is a diagram showing a time waveform for each optical fiber line. The vertical axis represents light intensity, and the horizontal axis represents wavelength.

  As shown in FIG. 7A, the time until the return light reaches the return inspection light processing unit 200 differs depending on the wavelength. This is due to the chromatic dispersion of the common optical fiber line 17 and the individual optical fiber lines 181 to 18n. Since the dispersion value of the common optical fiber line 17 and the individual optical fiber lines 181 to 18n is 18 ps / nm / km, the wavelength interval between the two optical pulses is about 1.0 nm, and the transmission distance is several km. The difference in arrival time of pulses is as short as several tens of picoseconds. For this reason, the optical line failure detection device 20 does not identify these two light pulses, and does not erroneously detect the positions of connection points and break points, and finally the time as shown in FIG. Get the waveform. The subsequent processing in the return inspection light processing unit 200 is the same as that in Patent Document 1.

  Thus, in the present embodiment, the signal light propagating through the WDM-PON system 1 and the broadband optical pulse are not superimposed. For this reason, it is not necessary to stop communication of the WDM-PON system 1 in performing the failure detection test. That is, regardless of the configuration of the WDN-PON system, it is possible to perform a failure detection test for all bands at once.

  The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the invention described in the claims, and it is also included within the scope of the present invention. Not too long.

1 WDM-PON system 10 OLT
DESCRIPTION OF SYMBOLS 15 Fixed wavelength splitter 17 Common optical fiber line 22 Broadband optical pulse generation means 23 Optical circulator 25 Photoreceiver 26 Analog / digital converter 27 Time waveform acquisition means 28 Reference waveform storage means 29 Fault detection means 100w 1st optical isolator 101w 1st 1 FBG
102w 1st wavelength selector 100r 2nd optical isolator 101r 2nd FBG
102r second wavelength selector 161-16n ONU
181 to 18n Optical fiber line 200 Return inspection light processing unit Pw Broadband optical pulse Pw ′ Broadband optical pulse after passing through first wavelength selector Pw ″ Incident light to fixed wavelength splitter 15 Pr after passing through fixed wavelength splitter Return light Pr ′ Return light after second FBG transmission λk Signal light wavelength

Claims (8)

Broadband optical pulse generating means for generating broadband optical pulses including all wavelengths of signal light used in the WDM-PON system;
A first wavelength selector that outputs a broadband inspection light obtained by removing a wavelength component corresponding to the wavelength of the signal light from the broadband light pulse;
An optical splitter for introducing the broadband inspection light into the WDM-PON system;
A second wavelength selector that removes the signal light from the return light from the WDM-PON system including the broadband inspection light and the signal light, and outputs the signal light as return inspection light;
Converting the return inspection light into an electric signal, it possesses a return test light processing unit for comparing the electrical signal and the reference electrical signal,
The first wavelength selector removes the wavelength component with an inspection bandwidth, and the inspection bandwidth is narrower than a bandwidth of a fixed wavelength splitter used in the WDM-PON system.
An optical line fault detection device characterized by the above. The first wavelength selector includes:
A first fiber grating that totally reflects the signal light;
A first optical isolator that blocks reflected light of the first fiber grating.
The optical line fault detection apparatus according to claim 1 . The second wavelength selector includes a second fiber grating that totally reflects the signal light, and
A second optical isolator for blocking the reflected light of the second fiber grating.
The optical path failure detection device according to claim 1 or 2 . The return inspection light processing unit outputs a voltage corresponding to the light intensity of the return inspection light; and
An analog / digital converter for converting the voltage into a digital voltage signal;
A time waveform acquisition means for acquiring a time change of the digital voltage signal until a predetermined time elapses after the broadband optical pulse is incident on the WDM-PON system;
Reference waveform storage means for storing a reference waveform which is a waveform of the reference electrical signal;
A failure detection means for comparing the time variation of the digital voltage signal with the reference waveform;
The optical line failure detection device according to any one of claims 1 to 3 . The reference waveform storage means, a result of the fault detection means is compared with the time change and the reference waveform of the voltage, and wherein the time variation of the voltage is determined substantially the same in claim 4 for storing as said reference waveform Optical line fault detection device. A WDM- PON system comprising a station side optical line terminator, an optical fiber line, a fixed wavelength splitter, a subscriber side optical line terminator, and a narrowband transmission optical filter;
Broadband pulse generating means for generating a broadband optical pulse including all wavelengths of signal light used in the WDM- PON system, and broadband inspection light obtained by removing a wavelength component corresponding to the wavelength of the signal light from the broadband optical pulse A first wavelength selector, an optical splitter for introducing the broadband inspection light into the WDM-PON system, and the signal from the return light from the WDM-PON system including the broadband inspection light and the signal light. A light beam having a second wavelength selector that removes light and outputs it as return inspection light, and a return inspection light processing unit that converts the return inspection light into an electric signal and compares the electric signal with a reference electric signal. A road fault detection device,
The narrow-band transmission optical filter is disposed in the front stage of the subscriber-side optical line termination device , transmits the signal light, blocks the broadband inspection light ,
The first wavelength selector removes the wavelength component with an inspection bandwidth, and the inspection bandwidth is narrower than a bandwidth of a fixed wavelength splitter used in the WDM-PON system.
An optical line fault detection system. Generating a broadband optical pulse that includes all wavelengths of signal light used in the WDM-PON system;
A broadband inspection light is generated by removing a wavelength component corresponding to the wavelength of the signal light from the broadband optical pulse,
Introducing the broadband inspection light into the WDM-PON system;
Generating return inspection light obtained by removing the signal light from the return light from the WDM-PON system including the broadband inspection light and the signal light;
Converting the return inspection light into an electrical signal and comparing the electrical signal with a reference electrical signal;
An optical line fault detection method ,
In the generation of the broadband inspection light, the wavelength component is removed by the inspection bandwidth, and the inspection bandwidth is narrower than the bandwidth of the fixed wavelength branching unit used in the WDM-PON system.
An optical line fault detection method characterized by the above. A voltage corresponding to the light intensity of the return inspection light is generated, and a time change of the voltage is acquired until a predetermined time elapses after the broadband optical pulse is incident on the WDM-PON system,
Storing a reference waveform which is a waveform of the reference electrical signal;
Comparing the time variation of the voltage with the reference waveform;
As a result of the comparison, when the time change of the voltage and the reference waveform are substantially the same, the time change of the voltage is stored as a reference waveform.
The optical line failure detection method according to claim 7 .

Images