JP2016058916A - Detection device and detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detection device and a detection method that are capable of confirming whether or not there is an optical line termination device in various communication systems.SOLUTION: A detection device 10 receives leakage light leaked from an optical cable by a light-receiving element 25. The detection device comprises: a voltage signal conversion unit 12 that converts a downlink optical signal transmitted toward an optical line termination device 7 in the leaked light into a voltage signal including a direct current component, and also converts an uplink optical signal transmitted by the optical line termination device 7 into a voltage signal including a burst-like pulse waveform; a signal passage unit 14 that, among the voltage signals obtained by conversion at the voltage signal conversion unit 12, removes the downlink optical signal including the direct current component and allows the uplink optical signal including the burst-like pulse waveform to pass therethrough; and a determination unit 22 that measures the uplink optical signal that has passed through the signal passage unit 14 for a certain period, and determines whether or not there is the optical line termination device 7 by analyzing the uplink optical signal.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a detection device and an inspection method for an optical line termination device.

  As a conventional detection device for an optical line termination device, for example, a detection device described in Patent Document 1 is known. The detection device described in Patent Document 1 deforms an optical cable used in an optical communication network, receives a light leaking from the deformed portion and generates an electrical signal, and a subscriber side of the electrical signal. Based on the intensity of the electrical signal that has passed through the filter unit that passes the electrical signal according to the period of the bursty light transmitted from the installed optical line terminator and the presence of the bursty light And a display unit for displaying a determination result by the determination unit.

JP 2012-205284 A

  In a PON (Passive Optical Network) communication system in which a branching device (drop closure, etc.) is provided in the middle of an optical fiber network and a single fiber is branched into a plurality of subscribers, the optical line terminator is provided for each communication system. The burst period (frequency) of upstream light is different. In the conventional detection apparatus, the filter unit is set so as to correspond only to a specific period of upstream burst light. That is, in the conventional detection device, the upstream burst light that can pass through the filter unit is fixed, and therefore, when applied to other communication systems having different burst light periods, the filter unit (hardware, digital filter) is changed. Is required.

  An object of this invention is to provide the detection apparatus and detection method which can confirm the presence or absence of an optical line termination device in various communication systems.

  One aspect of the present invention is a detection device that detects the presence or absence of an optical line terminator, wherein light leaked from an optical cable is received by a light receiving element, and the leaked light is transmitted toward the optical line terminator. A voltage signal conversion unit that converts the downstream optical signal into a voltage signal having a DC component and converts the upstream optical signal transmitted from the optical line termination device into a voltage signal having a burst-like pulse waveform; Of the voltage signal converted by the signal converter, the downstream signal having a DC component is removed, and the upstream signal having a burst-like pulse waveform is passed, and the signal passing part is passed. A determination unit that measures the upstream optical signal for a certain period and analyzes the upstream optical signal to determine the presence or absence of the optical line termination device.

  According to another aspect of the present invention, there is provided a detection method for detecting the presence or absence of an optical line terminator, wherein light leaked from an optical cable is received by a light receiving element, and the leaked light is transmitted toward the optical line terminator. A voltage signal conversion step for converting the downstream optical signal into a voltage signal having a DC component, and converting the upstream optical signal transmitted from the optical line terminator into a voltage signal having a burst-like pulse waveform; Of the voltage signal converted in the conversion step, a downstream signal having a DC component is removed, and a signal passing step for passing an upstream signal having a burst-like pulse waveform is passed in the signal passing step. A determination step of measuring the upstream optical signal for a certain period and analyzing the upstream optical signal to determine the presence or absence of an optical line termination device. .

  According to the present invention, the presence or absence of an optical line termination device can be confirmed in various communication systems.

It is a figure which shows the structure of the optical communication system provided with the detection apparatus which concerns on 1st Embodiment. It is a figure which shows the structure of a detection apparatus. It is a figure which shows the structure of the light receiving element which receives leaked light. It is a figure which shows the structure of the light receiving element which receives the leakage light in the modification of 1st Embodiment. It is a figure which shows the structure of the detection apparatus which concerns on 2nd Embodiment. It is a figure which shows the structure of the detection apparatus which concerns on 3rd Embodiment. It is a figure which shows the structure of the detection apparatus which concerns on 4th Embodiment. It is a figure which shows the structure of the optical communication system provided with the detection apparatus which concerns on 4th Embodiment. It is a figure which shows the structure of the detection apparatus which concerns on 5th Embodiment. It is a figure explaining the detection of an edge. FIG. 11A is a diagram illustrating a theoretical waveform of the ONU upstream signal, and FIG. 11B is a diagram illustrating an actual waveform of the ONU upstream signal. 12A is a diagram illustrating a theoretical waveform of an ONU upstream signal, FIG. 12B is a diagram illustrating an actual waveform of the ONU upstream signal, and FIG. 12C is a diagram illustrating an ONU upstream signal. It is a figure which shows the waveform which differentiated the signal. It is a figure for demonstrating the setting of the threshold value in the determination part of the detection apparatus which concerns on other embodiment. It is a figure for demonstrating the setting of the threshold value in the determination part of the detection apparatus which concerns on other embodiment.

[Description of Embodiment of the Present Invention]
First, embodiments of the present invention will be listed and described.

  One aspect of the present invention is a detection device that detects the presence or absence of an optical line terminator, wherein light leaked from an optical cable is received by a light receiving element, and the leaked light is transmitted toward the optical line terminator. A voltage signal conversion unit that converts the downstream optical signal into a voltage signal having a DC component and converts the upstream optical signal transmitted from the optical line termination device into a voltage signal having a burst-like pulse waveform; Of the voltage signal converted by the signal converter, the downstream signal having a DC component is removed, and the upstream signal having a burst-like pulse waveform is passed, and the signal passing part is passed. A determination unit that measures the upstream optical signal for a certain period and analyzes the upstream optical signal to determine the presence or absence of the optical line termination device.

  In this detection device, the signal passing unit removes the downstream light signal having a DC component and passes the upstream light signal having a burst-like pulse waveform, and the determination unit transmits the upstream light that has passed through the burst light acquisition unit. Is measured for a certain period, and the presence or absence of the optical line terminator is determined by analyzing the upstream optical signal. As described above, in the detection apparatus, the upstream optical signal having all burst-like pulse waveforms is passed through the signal passing section, and the upstream optical signal is analyzed to determine the presence or absence of the optical line termination device. Therefore, even if the burst period of upstream light is different for each communication system, it is not necessary to change the configuration of the detection apparatus according to the burst period. Therefore, the detection device can confirm the presence or absence of the optical line termination device in various communication systems.

  In one embodiment, an edge detection unit that detects an edge of an upstream light signal that has passed through a signal passing unit and outputs an edge detection signal in response to the detection of the edge is provided. Alternatively, the presence or absence of the optical line termination device may be determined by measuring the edge detection signal output from the unit for a certain period and analyzing the number of times of the edge detection signal. As described above, the detection apparatus detects an edge of an upstream optical signal, analyzes the number of times of the edge detection signal, and determines the presence or absence of an optical line termination apparatus, and performs an A / D conversion of the signal. Do not need. Accordingly, the configuration of the detection device can be simplified. In addition, the pulse width of the burst pulse signal transmitted from the optical line termination device is as short as microseconds. Thus, in order to capture an extremely short burst-like pulse waveform, a high-performance CPU and a huge storage area are required. On the other hand, since the detection apparatus only needs to analyze the number of edge detection signals, a burst-like pulse waveform can be captured even in the case of an apparatus configuration in which the sampling period is equal to or greater than the pulse width.

  In one embodiment, the edge detection unit may detect the edge by differentiating the upstream light signal that has passed through the signal passing unit. Thereby, it becomes possible to detect an edge more reliably. As a result, the detection device can accurately determine the presence or absence of the optical line termination device.

  In one embodiment, the determination unit may determine that there is an optical line termination device when a signal having a higher intensity than the noise signal is present in the upstream optical signal. Thereby, the detection device can accurately determine the presence or absence of the optical line termination device.

  In one embodiment, the apparatus includes a peak intensity recording unit that records the highest intensity signal having the highest signal intensity in the upstream light signal that has passed through the signal passing unit within a certain period, and the determination unit is recorded in the peak intensity recording unit. The presence / absence of the optical line termination device may be determined based on the strongest signal. The pulse width of the burst pulse signal transmitted from the optical line terminal is as short as microseconds. Thus, in order to capture an extremely short burst-like pulse waveform, a high-performance CPU and a huge storage area are required. On the other hand, by recording the strongest signal with the highest signal intensity in the upstream light signal that has passed through the signal passing part within a certain period, even in the case of a device configuration in which the sampling period is equal to or greater than the pulse width, A burst-like pulse waveform can be captured.

  In one embodiment, the determination unit obtains an average value of the noise signal from the upstream light signal that has passed through the signal passing unit, and compares the average value of the noise signal with the maximum intensity signal recorded in the peak intensity recording unit. Then, when the strongest signal is significantly different from the average value of the noise signal, it may be determined that there is an optical line termination device. Thus, the detection device can more accurately determine the presence or absence of the optical line termination device.

  In one embodiment, the determination unit may determine that there is an optical line termination device when the value of the strongest signal recorded in the peak intensity recording unit exceeds a preset threshold value. Thus, the detection device can more accurately determine the presence or absence of the optical line termination device.

  In one embodiment, the apparatus includes a peak intensity recording unit that records the highest intensity signal having the highest signal intensity in the upstream light signal that has passed through the signal passing unit within a certain period, and the determination unit is stored in the peak intensity recording unit. The presence or absence of the optical line termination device may be determined by setting a threshold value according to the strongest signal and analyzing the strongest signal exceeding the threshold value. When the downstream signal component cannot be completely removed in the signal passing unit, the alternating current component signal of the downstream signal is superimposed on the upstream signal. At this time, if the intensity of the AC component signal exceeds a preset threshold value, there is a possibility that the presence / absence of the optical line terminator cannot be determined well. Therefore, by setting the threshold value with the strongest signal as a reference, even if the AC component signal is superimposed on the upstream signal, the AC component signal can be set so as not to exceed the threshold value. Presence / absence of a termination device can be accurately determined.

  In one embodiment, the leakage light is leakage light obtained by deforming the optical cable, and at least two light receiving elements may be provided along the longitudinal direction of the optical cable and sandwiching the deformation portion. In this way, by providing two light receiving elements and comparing the intensity of the upstream light signal in the two light receiving elements, the propagation direction of the upstream light can be determined. Thereby, upstream light can be detected regardless of the direction of the optical cable.

  In one embodiment, a first light source unit that transmits first light toward the optical line terminator side with respect to the optical cable, and a rear side of the first light transmitted from the first light source unit and incident on the optical cable A light receiving unit that receives the scattered light, and the determination unit obtains the return loss based on the intensity of the first light transmitted from the light source unit and the backscattered light received by the light receiving unit, The presence or absence of an optical line termination device may be determined based on the return loss. When the optical line terminator is turned off, no upstream light (burst light) is transmitted from the optical line terminator. Therefore, the upstream signal cannot be acquired in the signal conversion unit. Therefore, the first light source emits light toward the optical termination device, and the return loss is obtained based on the intensity of the first light transmitted from the light source unit and the backscattered light received by the light receiving unit. . In this manner, the detection device can determine the presence or absence of the optical line terminator by obtaining the return loss even when the power of the optical line terminator is off.

  In one embodiment, the optical cable is provided immediately before the optical line terminator and includes a reflection unit that reflects light of a specific wavelength. What is the first light transmitted from the first light source unit? A second light source unit that transmits second light having a different wavelength and reflected by the reflection unit is provided, and the determination unit transmits the intensity of the second light transmitted from the second light source unit and the second light source unit. When the reflection attenuation amount is obtained based on the backscattered light of the second light incident on the optical cable and received by the light receiving portion, and the reflection by the reflection portion is confirmed from the reflection attenuation amount, the first light The presence / absence of the optical line termination device may be determined together with the measurement result of the return loss. The optical cable may be left in a disconnected state before reaching the subscriber's home. In such a case, when determining the presence or absence of the optical line termination device based on the return loss amount using the first light source, the value of the return loss amount is determined depending on the state of the cut surface of the optical cable. There is a risk of the value being judged.

  Therefore, the determination unit returns the return loss based on the intensity of the second light transmitted from the second light source unit and the backscattered light of the second light transmitted from the second light source unit and incident on the optical cable. When the reflection by the reflection unit is confirmed from the reflection attenuation amount, the presence / absence of the optical line termination device is determined together with the measurement result of the reflection attenuation amount of the first light. Thereby, in the detection device, after the reflection by the reflection unit provided immediately before the optical line termination device is confirmed, that is, after it is confirmed that the optical line termination device and the optical cable are connected, the optical line termination is performed. Since the presence / absence of the device is determined, erroneous determination of the presence / absence of the optical line termination device can be prevented.

  According to another aspect of the present invention, there is provided a detection method for detecting the presence or absence of an optical line terminator, wherein light leaked from an optical cable is received by a light receiving element, and the leaked light is transmitted toward the optical line terminator. A voltage signal conversion step for converting the downstream optical signal into a voltage signal having a DC component, and converting the upstream optical signal transmitted from the optical line terminator into a voltage signal having a burst-like pulse waveform; Of the voltage signal converted in the conversion step, a downstream signal having a DC component is removed, and a signal passing step for passing an upstream signal having a burst-like pulse waveform is passed in the signal passing step. A determination step of measuring the upstream optical signal for a certain period and analyzing the upstream optical signal to determine the presence or absence of an optical line termination device. .

  In this detection method, the downstream light signal having a DC component is removed in the signal passing step and the upstream light signal having a burst-like pulse waveform is allowed to pass. In the determination step, the upstream light that has passed through the burst light acquisition unit is passed. Is measured for a certain period, and the presence or absence of the optical line terminator is determined by analyzing the upstream optical signal. As described above, in the detection method, in the signal passing step, all upstream optical signals having a burst-like pulse waveform are passed, and the upstream optical signal is analyzed to determine the presence or absence of the optical line termination device. Therefore, in the detection method, even if the burst period of upstream light differs for each communication system, it is not necessary to change the configuration according to the burst period. Therefore, in the detection method, the presence or absence of the optical line termination device can be confirmed in various communication systems.

  In one embodiment, an edge detection step of detecting an edge of an upstream signal that has passed through the signal passage unit and outputting an edge detection signal in response to the detection of the edge is included. In the determination step, output is performed in the edge detection step. The presence / absence of the optical line termination device may be determined by measuring the edge detection signal thus obtained for a certain period and analyzing the number of times of the edge detection signal.

  In one embodiment, in the edge detection step, the edge may be detected by differentiating the upstream signal that has passed through the signal passage unit.

  In one embodiment, in the determination step, it may be determined that there is an optical line termination device when a signal having a higher intensity than the noise signal is present in the upstream optical signal.

  In one embodiment, the method includes a peak intensity recording step for recording the highest intensity signal having the highest signal intensity in the upstream light signal that has passed in the signal passing step within a certain period, and the determination step is recorded in the peak intensity recording step. The presence / absence of the optical line termination device may be determined based on the strongest signal.

  In one embodiment, in the determining step, an average value of the noise signal is obtained from the upstream light signal passed in the signal passing step, and the average value of the noise signal is compared with the maximum intensity signal recorded in the peak intensity recording step. Then, when the strongest signal is significantly different from the average value of the noise signal, it may be determined that there is an optical line termination device.

  In one embodiment, the determination step may determine that there is an optical line termination device when the value of the strongest signal recorded in the peak intensity recording step exceeds a preset threshold value.

  In one embodiment, the method includes a peak intensity recording step that records the highest intensity signal having the highest signal intensity in the upstream light signal that has passed through the signal passing section within a certain period, and the determination step stores the peak intensity recording step. The presence or absence of the optical line termination device may be determined by setting a threshold value according to the strongest signal and analyzing the strongest signal exceeding the threshold value.

  In one embodiment, a first optical transmission step for transmitting first light to the optical line terminator side with respect to the optical cable, and a first light transmitted in the first optical transmission step and incident on the optical cable A light receiving step for receiving the backscattered light, and in the determining step, the reflection attenuation based on the intensity of the first light transmitted in the first light transmitting step and the backscattered light received in the light receiving step The amount may be obtained, and the presence / absence of the optical line termination device may be determined based on the return loss amount.

  In one embodiment, a reflection unit that reflects light of a specific wavelength is provided immediately before the optical line termination device of the optical cable, and the reflection unit has a wavelength different from that of the first light transmitted in the first light transmission step. A second light sending step for sending the second light reflected by the optical cable, and in the determining step, the intensity of the second light sent in the second light sending step and the optical cable sent in the second light sending step The reflection attenuation amount is obtained based on the backscattered light of the second light incident on the light source, and when the reflection by the reflection unit is confirmed from the reflection attenuation amount, the measurement result of the reflection attenuation amount of the first light is obtained. In addition, the presence / absence of an optical line termination device may be determined.

[Details of the embodiment of the present invention]
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted.

[First Embodiment]
FIG. 1 is a diagram illustrating a configuration of an optical communication system including the detection device according to the first embodiment. An optical communication system 1 shown in FIG. 1 includes a terminal 3 (hereinafter referred to as OLT: Optical Line Terminal) 5 and a subscriber's optical line terminal (hereinafter referred to as ONU: Optical Network Unit) by PON (Passive Optical Network) communication. 7 is a system for performing communication with an optical cable 9. The detection apparatus 10 according to the first embodiment is provided, for example, in a branch drop closure 6 and a drop closure 8 provided between the OLT 5 and the ONU 7. The detection device 10 is a device that detects the presence (existence) of the ONU 7.

  In the optical communication system 1 shown in FIG. 1, the direction from the OLT 5 of the station 3 to the ONU 7 of the subscriber's house is defined as “downward”, and the direction from the ONU 7 to the OLT 5 is defined as “upward”. Light flowing from the OLT 5 to the ONU 7 via the optical cable 9 is referred to as “OLT downstream light”, and light flowing from the ONU 7 to the OLT 5 via the optical cable 9 is referred to as “ONU upstream light”. The OLT 5 transmits light having a wavelength of 1.49 μm, for example. The ONU 7 transmits light having a wavelength of 1.31 μm, for example. From the ONU 7, burst-like light (hereinafter referred to as burst light) is transmitted.

  FIG. 2 is a diagram illustrating a configuration of the detection device. As shown in FIG. 2, the detection device 10 includes a leakage light acquisition unit (voltage signal conversion unit) 12, an AC coupling unit (signal passage unit) 14, an AD conversion unit 16, a control unit 18, and a digital signal. The recording unit 20, the determination unit 22, and the display unit 24 are included. The detection device 10 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like. The control unit 18, the digital signal recording unit 20, and the determination unit 22 are programmed. Run as.

  The leaked light acquisition unit 12 acquires light that leaks from the deformed portion of the optical cable 9 when the optical cable 9 is deformed (hereinafter, leaked light). FIG. 3 is a diagram illustrating a configuration of a light receiving element that receives leakage light. As shown in FIG. 3, the leakage light is received by the light receiving element 25. The light receiving element 25 is, for example, a photodiode (PD). A detailed description of the device for deforming the optical cable 9 is omitted, but a known device can be used. The light receiving element 25 is disposed at a position where the leakage light of the ONU upstream light is easily received, and mainly receives the ONU upstream light, but also receives the OLT downstream light at the same time. The means for leaking light from the optical cable 9 is not limited to the one that deforms the optical cable 9.

  The leak light acquisition unit 12 generates an electrical signal from the leak light received by the light receiving element 25. Specifically, the light receiving element 25 outputs the received leaked light as a current signal to the leaked light acquisition unit 12. The leaked light acquisition unit 12 amplifies the electric signal according to the received light intensity. Specifically, the leaked light acquisition unit 12 converts the current signal output from the light receiving element 25 into a voltage signal using a load resistance (voltage signal conversion step). In the leaked light acquisition unit 12, the load resistance R is used for voltage conversion, and the frequency characteristic (cut-off frequency [Hz]) of the voltage signal that can be converted into voltage is considered in consideration of the inter-terminal capacitance C of the light receiving element 25. It is determined by 1 / 2πRC.

  Specifically, for example, when the inter-terminal capacitance C of the light receiving element 25 is 10 pF and the load resistance R is 10 MΩ, the cutoff frequency is about 1.6 kHz. In this case, the response to a signal of 1.6 kHz or higher becomes poor, and the signal becomes dull in a DC shape. By using a load resistor R having a large resistance value such as 10 MΩ, the converted voltage signal V is greatly amplified from the relationship of V = IR.

  In the optical communication system 1 in which the transmission rate of the signal through the optical cable 9 is 500 MHz (1 Gbps) or more, the leaked light acquisition unit 12 is an OLT downstream light signal (hereinafter referred to as an OLT downstream optical signal) and an ONU upstream light signal (hereinafter referred to as an ONU upstream light signal). , ONU upstream optical signal) is converted as follows.

  The OLT 5 simultaneously transmits communication signals to a plurality of ONUs 7 in the optical communication system 1 (TDM: Time Division Multiplexer) and always transmits other control signals (Discovery, etc.). For this reason, the OLT downstream optical signal is a signal that constantly fluctuates at high speed. For an OLT downstream optical signal that constantly fluctuates at a high speed, the response is poor and it is difficult to decompose the signal. Therefore, in the leaked light acquisition unit 12, the OLT downstream optical signal is converted into a voltage signal having a DC component (dull to DC component) and amplified.

  The ONU 7 intermittently sends an ONU upstream optical signal according to the control signal from the OLT 5. As described above, in the optical communication system 1, the transmission rate of the ONU upstream optical signal is 500 MHz or more. For this reason, the ONU upstream optical signal is a signal that fluctuates at high speed and is difficult to decompose. Therefore, the leakage light acquisition unit 12 converts the ONU upstream optical signal into a voltage signal having a lump pulse waveform and amplifies it. In general, since the signal length of the signal transmitted by the ONU 7 at a time is in units of microseconds, it is converted and amplified as a burst-like pulse waveform in units of microseconds. The leaked light acquisition unit 12 outputs the converted OLT downstream signal and ONU upstream signal to the AC coupling unit 14.

  The AC coupling unit 14 functions as a filter that removes a specific voltage signal and passes the specific voltage signal. When the AC coupling unit 14 receives the OLT downstream signal and the ONU upstream signal output from the leaked light acquisition unit 12, the AC coupling unit 14 removes the OLT downstream signal having a DC component and passes all the ONU upstream signal (signal passing step). The AC coupling unit 14 outputs the passed ONU upstream signal (analog voltage signal) to the AD conversion unit 16.

  The AD converter 16 converts an analog signal into a digital signal. The AD conversion unit 16 acquires an ONU upstream signal (electrical signal) that is an analog signal output from the AC coupling unit 14 based on a command from the control unit 18 to be described later, and converts the analog signal into a digital signal. Convert. The AD conversion unit 16 outputs the converted digital signal to the control unit 18.

  The control unit 18 outputs a command to the AD conversion unit 16 and causes the AD conversion unit 16 to convert an analog signal into a digital signal. When the control unit 18 receives the digital signal converted by the AD conversion unit 16 and output from the AD conversion unit 16, the control unit 18 causes the digital signal recording unit 20 to record the digital signal. The digital signal recording unit 20 records the digital signal obtained and converted by the AD conversion unit 16 for a certain period. Note that the pulse width of the ONU upstream burst light having a pulse wave shape is in units of microseconds in a general PON communication system. Therefore, the control unit 18 sets an analog signal acquisition and conversion period in the AD conversion unit 16 to be equal to or less than the pulse width in order to accurately acquire the ONU upstream burst signal.

  The determination unit 22 determines the presence / absence of ONU upstream burst light, that is, the presence / absence of ONU 7. The determination unit 22 analyzes the digital signal converted in a certain period recorded in the digital signal recording unit 20 and determines the presence / absence of ONU upstream burst light (determination step). Since the optical signal transmitted from the ONU 7 is in the form of a burst, the electrical signal while not transmitting the optical signal becomes a noise signal. The determination unit 22 refers to the digital signal recording unit 20 and analyzes the presence of a signal whose intensity is higher than that of the noise signal among the electric signals recorded in the digital signal recording unit 20 to determine whether there is ONU upstream light. Determine. Specifically, the determination unit 22 determines that ONU upstream burst light is present (communicating) when a signal having a higher intensity than the noise signal exists. That is, the determination unit 22 determines that the ONU 7 is present.

  As a method for determining the presence of a high-intensity signal (burst optical signal) in the determination unit 22, for example, the following method can be used. As a first method, the determination unit 22 uses a preset threshold value of signal strength, and determines that there is ONU upstream burst light when there is a signal whose signal strength is higher than the threshold value. As a second method, the determination unit 22 performs statistical analysis (average, variance, etc.) on the strength of all electric signals recorded in the digital signal recording unit 20 and detects a significantly high signal strength. , It may be determined that there is ONU upstream burst light. The determination unit 22 outputs the determination result to the display unit 24.

  The display unit 24 displays the determination result in the determination unit 22. Upon receiving the determination result output from the determination unit 22, the display unit 24 performs display based on the determination result. For example, the display unit 24 may display an image indicating that the ONU 7 is present (not indicating that the ONU 7 is not present), or may light a lamp or the like indicating that.

  As described above, in the detection apparatus 10 according to the present embodiment, the AC coupling unit 14 removes the downstream light signal having a direct current component, and allows the upstream light signal having a burst-like pulse waveform to pass. The unit 22 measures the upstream light signal that has passed through the AC coupling unit 14 for a certain period, and determines the presence or absence of the ONU 7 by analyzing the upstream light signal. As described above, in the detection apparatus 10, the AC coupling unit 14 passes all upstream light signals having a burst-like pulse waveform, and analyzes the upstream light signal to determine the presence or absence of the ONU 7. Therefore, in the detection apparatus 10, even if the burst period of upstream light differs for each communication system, it is not necessary to change the configuration according to the burst period. Therefore, the detection device 10 can confirm the presence or absence of the ONU 7 in various communication systems.

  In the above embodiment, the first method and the second method are described as examples of the determination method in the determination unit 22, but the determination method in the determination unit 22 may be the following method. As a third method, a signal amplification circuit is further provided between the AC coupling unit 14 and the AD conversion unit 16, and an electric signal output from the AC coupling unit 14 is amplified by the signal amplification circuit and the AD conversion unit 16 performs the amplification. A / D conversion may be performed. When the electric signal output from the AC coupling unit 14 is amplified by the signal amplification circuit, the signal intensity difference between the noise signal and the burst optical signal increases. Thereby, the determination part 22 can determine more correctly whether the signal whose intensity | strength is higher than a noise signal exists.

  Further, as a fourth method, in the above-described signal amplification circuit, an amplification factor that saturates only the burst optical signal is set, and the determination unit 22 determines whether or not the saturation signal exists, thereby determining the ONU upstream burst light. It may be determined that there is (communication). Thereby, the determination in the determination part 22 can be performed still more correctly.

  In the above-described embodiment, the control unit 18 may cause the AD conversion unit 16 to acquire and convert an analog signal a plurality of times. Thereby, in the detection apparatus 10, the probability that the ONU burst optical signal matches the acquisition timing is improved. For example, the control unit 18 performs A / D conversion and acquisition 100 times. The determination unit 22 determines that the ONU 7 is present when a predetermined number of ONU burst optical signals are detected among the 100 times. As a method of performing a plurality of measurements for acquiring and converting an analog signal in the AD conversion unit 16 in the control unit 18, a reference clock is set and shifted every microseconds from the reference clock every measurement or obtained by a random number. There is a way to shift the given time.

[Second Embodiment]
Next, the second embodiment will be described. FIG. 4 is a diagram illustrating a configuration of a detection device according to the second embodiment. As illustrated in FIG. 4, the detection device 10 </ b> A includes a leakage light acquisition unit 12, an AC coupling unit 14, an AD conversion unit 16, a control unit 18, a digital signal recording unit 20, a determination unit 22, and a display. Part 24 and a peak intensity recording part 26.

  The AC coupling unit 14 outputs an electrical signal to the AD conversion unit 16 and the peak intensity recording unit 26. When receiving a command from the control unit 18, the peak intensity recording unit 26 receives the electrical signal output from the AC coupling unit 14 and records the highest signal strength (maximum strength signal) in the electrical signal (peak). Intensity recording step). The peak intensity recording unit 26 outputs the recorded electrical signal to the control unit 18.

  The control unit 18 causes the AD conversion unit 16 to start signal acquisition and conversion, and causes the peak intensity recording unit 26 to start recording. When receiving the electrical signal output from the peak intensity recording unit 26, the control unit 18 resets the peak intensity recording unit 26. The control unit 18 causes the digital signal recording unit 20 to record the digital signal output from the AD conversion unit 16 and the electrical signal output from the peak intensity recording unit 26.

  The determination unit 22 refers to the signal recorded in the digital signal recording unit 20 and obtains an average of the noise signal from the periodically acquired electric signal. The determination unit 22 compares the average value with the maximum intensity value of the electrical signal recorded by the peak intensity recording unit 26. If the maximum intensity value is significantly different from the noise average value, the ONU 7 is present. judge. Alternatively, the determination unit 22 determines that the ONU 7 is present when the maximum intensity value recorded in the digital signal recording unit 20 exceeds a preset threshold value. The determination unit 22 outputs the determination result to the display unit 24.

  As described above, in the detection apparatus 10 </ b> A of the present embodiment, the peak intensity recording unit 26 records the highest signal intensity in the electric signal output from the AC coupling unit 14. The determination unit 22 determines the presence / absence of the ONU 7 based on the maximum intensity value of the electrical signal recorded by the peak intensity recording unit 26. As described in the first embodiment, in a general PON communication system, since the pulse width of burst light transmitted from the ONU 7 is, for example, in microseconds, the control unit 18 accurately transmits the ONU upstream burst optical signal. In order to acquire it, the AD conversion unit 16 acquires and converts an analog signal and sets the cycle to be equal to or less than the pulse width. However, when the signal acquisition cycle is set to be equal to or less than the pulse width, a high-performance CPU is required, and since the acquired data for the measurement period increases, the data recording area must be enlarged. As a result, the production cost of the apparatus may increase.

  On the other hand, in the detection apparatus 10A, by providing the peak intensity recording unit 26, even when the signal acquisition cycle does not satisfy the pulse width or less, the maximum intensity value of the electric signal is recorded, thereby enabling the ONU. The presence or absence of upstream burst light can be detected. Therefore, the presence / absence of the ONU 7 can be determined at low cost without providing a high-performance CPU or the like.

  In the said 1st and 2nd embodiment, in the leak light acquisition part 12, although the structure (refer FIG. 3) provided with one light receiving element 25 was demonstrated as an example, as FIG. For example, two may be provided. As described above, two light receiving elements 25 are provided along the longitudinal direction of the optical cable 9 and sandwiching the deformed portion. By comparing the intensity of the ONU upstream optical signals of the two light receiving elements 25 and 25, the propagation direction of the upstream light Can be determined. Thereby, ONU upstream light can be detected regardless of the direction of the optical cable 9.

[Third Embodiment]
Subsequently, the third embodiment will be described. FIG. 6 is a diagram illustrating a configuration of a detection device according to the third embodiment. As illustrated in FIG. 6, the detection device 10B includes a leakage light acquisition unit 12, an AC coupling unit 14, an AD conversion unit 16, a control unit 18, a digital signal recording unit 20, a determination unit 22, and a display. A unit 24, a light source unit (first light source unit) 28, a light receiving unit 30, and an optical multiplexing / demultiplexing unit 32.

  The detection device 10B has a configuration in which, for example, when the ONU 7 is powered off and the leakage light acquisition unit 12 cannot detect the ONU burst light, the presence or absence of the ONU 7 is determined. In the detection device 10B, if the ONU burst light cannot be detected by the leakage light acquisition unit 12, the connector C1 or C2 (see FIG. 1) in the branch drop closure 6 or the drop closure 8 is removed, and the optical cable 9 ( The drop cable) is directly connected to the detection device 10B. The detection device 10B is provided with a coupler (not shown). In the following description, a configuration for determining the presence or absence of the ONU 7 in the branch drop closure 6 will be described as an example.

  After the connector C1 is connected to the coupler of the detection device 10B, the control unit 18 sends a command to send continuous light to the light source unit 28. The light source unit 28 receives a command from the control unit 18 and transmits continuous light (first light) (first light transmission step). The light source unit 28 is an LD (Laser Diode), for example, and transmits light having a predetermined wavelength. The light transmitted from the light source unit 28 enters the optical cable 9 through the optical multiplexing / demultiplexing unit 32. The light incident on the optical cable 9 is propagated to the subscriber premises.

  The light receiving unit 30 receives backscattered light transmitted from the light source unit 28 and incident on the optical cable 9 (light receiving step). The light receiving unit 30 directly receives the light transmitted from the light source unit 28 via the optical multiplexing / demultiplexing unit 32. The light receiving unit 30 outputs a current signal of the received light to the AD conversion unit 16.

  The control unit 18 acquires the intensity of continuous light transmitted from the light source unit 28 and the intensity of backscattered light from the optical cable 9 via the AD conversion unit 16. The control unit 18 causes the digital signal recording unit 20 to record the acquired continuous light intensity and the intensity of the backscattered light from the optical cable 9.

  The determination unit 22 determines the return loss of the optical cable 9 based on the intensity of continuous light recorded in the digital signal recording unit 20 and the intensity of backscattered light of the optical cable 9. The return loss is the ratio of the reflected light to the intensity of the incident light that has entered the optical cable 9. When the calculated return loss is a value indicating high reflection equivalent to Fresnel reflection, the determination unit 22 determines that the end of the optical cable 9 on the subscriber's home side is open, and the ONU 7 is present. It is determined that there is no (no ONU 7). On the other hand, when the determined return loss is a value indicating low reflection equivalent to connector connection, the determination unit 22 determines that the end of the optical cable 9 on the subscriber's home side is connected to the ONU 7, and the ONU 7 Is determined to exist. At this time, the determination unit 22 determines that the ONU 7 is powered off in response to the result that the leakage light acquisition unit 12 cannot detect the ONU burst light. The determination unit 22 outputs the determination result to the display unit 24.

  The display unit 24 displays the determination result in the determination unit 22. Upon receiving the determination result output from the determination unit 22, the display unit 24 performs display based on the determination result. For example, the display unit 24 may display an image indicating that the ONU 7 is in an off state and the ONU 7 is present, or may light a lamp or the like.

  As described above, in the detection device 10B according to this embodiment, for example, even when the ONU 7 is powered off and the ONU 7 is not transmitting ONU upstream burst light, the presence of the ONU 7 is determined based on the return loss. Presence / absence can be determined.

  The detection device 10B can determine the state of the optical cable 9 in addition to determining whether the ONU 7 exists. The optical cable 9 removed in the branch drop closure 6 and the drop closure 8 is not connected to the ONU 7 but is left in the closure and may be reused when re-contracted. At this time, for example, bending or the like is added to the remaining optical cable 9, so that transmission loss increases, and there is a possibility that communication cannot be performed normally in the ONU 7.

  For such a problem, in the detection apparatus 10B, after being connected to the connector C1 (C2) of the optical cable 9, the continuous light is transmitted from the light source unit 28 and the return loss of the optical cable 9 is measured. 9 states can be determined. Since the end of the optical cable 9 on the subscriber's home side is an open end, a return loss equivalent to Fresnel reflection can be obtained when the state of the optical cable 9 is normal. On the other hand, when the state of the optical cable 9 is abnormal (transmission loss is high), the reflection is lower than the Fresnel reflection. Note that a threshold value based on Fresnel reflection may be set for determining the state of the optical cable 9. In the above description, the continuous light has been described as an example of the first light. However, the first light may be intermittent light.

[Fourth Embodiment]
Subsequently, a fourth embodiment will be described. FIG. 7 is a diagram illustrating a configuration of a detection device according to the fourth embodiment. As illustrated in FIG. 7, the detection device 10 </ b> C includes a leakage light acquisition unit 12, an AC coupling unit 14, an AD conversion unit 16, a control unit 18, a digital signal recording unit 20, a determination unit 22, and a display. Unit 24, light source unit 28, light receiving unit 30, optical multiplexing / demultiplexing unit 32, high reflection light source unit (second light source unit) 34, and optical multiplexing unit 36.

  FIG. 8 is a diagram illustrating a configuration of a communication system including the detection device according to the fourth embodiment. As shown in FIG. 8, in the optical communication system 1A, an optical high reflection filter F is provided in the optical cable 9 immediately before the ONU 7 on the subscriber's home side. The optical high reflection filter F is, for example, a filter that transmits light having wavelengths of 1.31 μm, 1.49 μm, and 1.55 μm, and reflects higher than Fresnel reflection only for a specific light wavelength different from the communication light wavelength. It is. As the optical high reflection filter F, for example, an FBG (fiber Bragg grating) filter can be used.

  When the connector C1 (see FIG. 1) is connected to the coupler of the detection device 10C, the control unit 18 sends a command to send continuous light to the high reflection light source unit 34. The high reflection light source unit 34 receives a command from the control unit 18 and transmits continuous light (second light) (second light transmission step). The high reflection light source unit 34 is, for example, an LD (Laser Diode). The light transmitted from the high reflection light source unit 34 has a wavelength different from that of the light transmitted from the light source unit 28 and is reflected by the optical high reflection filter F. The light transmitted from the high reflection light source unit 34 enters the optical cable 9 through the optical multiplexing unit 36 and the optical multiplexing / demultiplexing unit 32. The light incident on the optical cable 9 is propagated to the subscriber premises.

  The control unit 18 acquires the intensity of continuous light transmitted from the high reflection light source unit 34 and the intensity of backscattered light from the optical cable 9 via the AD conversion unit 16. The control unit 18 causes the digital signal recording unit 20 to record the acquired continuous light intensity and the intensity of the backscattered light from the optical cable 9.

  The determination unit 22 reflects the light transmitted from the high reflection light source unit 34 on the optical cable 9 based on the intensity of continuous light recorded in the digital signal recording unit 20 and the intensity of the backscattered light of the optical cable 9. Obtain the attenuation. If the obtained return loss is a value indicating high reflection exceeding Fresnel reflection, the determination unit 22 determines that the optical high-reflection filter F has been reflected and determines that the optical cable 9 is not cut.

  On the other hand, the determination part 22 determines with the optical cable 9 having been cut | disconnected, when the calculated | required return loss amount is not a value which shows the high reflection exceeding Fresnel reflection. When the determination unit 22 determines that the optical cable 9 is not cut, the detection device 10C sends a command for the continuous light to be transmitted to the light source unit 28 by the control unit 18, and the method according to the third embodiment. Thus, the presence or absence of the ONU 7 is determined. When the determination unit 22 determines that the optical cable 9 is disconnected, the detection device 10C does not determine whether the ONU 7 is present. The determination unit 22 outputs the determination result to the display unit 24. In the above description, continuous light has been described as an example of the second light. However, the second light may be intermittent light.

  As described above, in the detection device 10C of the present embodiment, it can be determined whether or not the optical cable 9 is disconnected. When the optical cable 9 is cut, depending on the state of the cut end face, the reflection attenuation amount may be a value indicating low reflection. In this case, it may be determined that the ONU 7 exists. On the other hand, since the detection apparatus 10C determines whether the ONU 7 exists after determining whether the optical cable 9 is disconnected, it is possible to prevent erroneous determination of the presence of the ONU 7.

  Further, even when determining whether or not the optical cable 9 that is not connected to the ONU 7 and is left in the closure as described in the third embodiment is normal, the methods of the third embodiment and the fourth embodiment are combined. By using it, the state of the optical cable 9 can be grasped by two lights having different wavelengths, and the state determination of the optical cable 9 can be performed more reliably.

  Further, in the detection device 10C, the bending loss of the optical cable 9 can be estimated. The bending loss of the optical cable 9 depends on the optical wavelength. For example, ITU-T G.I. In the single-mode optical fiber of 625, when the bending radius is 15 mm, the bending loss is about 2.33 × 10 −2 dB / m when the wavelength is 1.31 μm, and the bending loss is 1.45 dB / when the wavelength is 1.55 μm. When the wavelength is about 1.65 μm, the bending loss is about 4.77 dB / m.

  The detection device 10 </ b> C includes light sources having two different wavelengths, the light source unit 28 and the high reflection light source unit 34. In the detection apparatus 10C, the return loss of the optical cable 9 at two different wavelengths is obtained, and the bend radius of the optical cable 9 is estimated from the difference in return loss from the loss corresponding to the bend radius of each wavelength stored in advance. .

Specifically, the detection device 10 </ b> C sets the wavelength of the light transmitted from the light source unit 28 to 1.55 μm, the wavelength of the light transmitted from the high reflection light source unit 34 to 1.65 μm, and reflects the reflected light from the optical high reflection filter F. When the attenuation is 1 dB, the reflection attenuation of the optical cable 9 is as follows.
Wavelength 1.55 μm: Return loss about 15 dB (Fresnel reflection)
Wavelength 1.65 μm: Return loss about 1 dB (reflection by high reflection filter)
That is, under the above conditions, the difference in return loss is about 14 dB.

Here, it is assumed that ITU-T G. When a 625 single-mode optical fiber optical cable 9 is bent with a bending radius of 15 mm, the respective return loss amounts are as follows.
Wavelength 1.55 μm: Return loss about 18 dB
Wavelength 1.65 μm: Return loss about 10.5 dB
That is, the difference in return loss is 7.5 dB. Therefore, when the difference between the reflection attenuation amounts at both wavelengths of the light source unit 28 and the highly reflective light source unit 34 is about 7.5 dB, the optical cable 9 is bent with a bending radius of 15 mm. Furthermore, the transmission loss of the transmission wavelength can be estimated from the estimated bending radius. As described above, the detection device 10 </ b> C can estimate the bending radius and transmission loss of the optical cable 9.

  The detection devices 10B and 10C can be used as follows. When the ONU 7 is installed at the subscriber's home, an optical cable 9 (drop cable) is connected to the ONU 7. On the closure side, the remaining optical cable 9 is connected to the detection device 10B (10C). Then, the presence or absence of the ONU 7 is determined in the detection device 10B (10C). As a result of the determination, if it is determined that the ONU 7 is present, it can be confirmed that the connected optical cable 9 is a cable used for installation work. Therefore, the detection devices 10B and 10C can be used for the confirmation work of the optical cable 9 used for the installation work when the ONU 7 is set.

[Fifth Embodiment]
Subsequently, a fifth embodiment will be described. FIG. 9 is a diagram illustrating a configuration of a detection device according to the fifth embodiment. As illustrated in FIG. 9, the detection device 10 </ b> D includes a leakage light acquisition unit 12, an AC coupling unit 14, an edge detection unit 40, a determination unit 22, and a display unit 24. The leak light acquisition unit 12 may be configured to include one light receiving element 25 or may be configured to include two light receiving elements 25, for example.

  The edge detection unit 40 detects an edge of the ONU upstream signal that has passed through the AC coupling unit 14 and outputs an edge detection signal in response to the detection of the edge. When the edge detection unit 40 receives the ONU upstream signal output from the AC coupling unit 14, the edge detection unit 40 detects an edge of the ONU upstream signal. As shown in FIG. 10, the edge detection unit 40 detects a rising edge (portion surrounded by a broken-line circle) in the ONU upstream signal output from the AC coupling unit 14.

  Here, the waveform of the ONU upstream signal will be described. FIG. 11A is a diagram illustrating a theoretical waveform of the ONU upstream signal, and FIG. 11B is a diagram illustrating an actual waveform of the ONU upstream signal. As shown in FIGS. 11A and 10A, the theoretical waveform of the ONU upstream signal is a square wave (rectangular wave). On the other hand, the waveform of the actual ONU upstream signal is dull at the rising and falling portions as shown in FIG. This is due to the following reason. That is, the leakage light acquisition unit 12 has a time constant of R × C due to the load resistance R used for voltage conversion and the inter-terminal capacitance C of the light receiving element 25. Therefore, the waveform of the ONU upstream signal generated in the leaked light acquisition unit 12 becomes a smooth asymptotic line at the rising and falling portions, as shown in FIG. In such a waveform, for example, when the interval between ONU upstream signals is small, it is difficult to detect an edge.

  Therefore, in the present embodiment, the edge detection unit 40 differentiates the ONU upstream signal output from the AC coupling unit 14 to detect the edge of the ONU upstream signal. The edge detection unit 40 has a differentiation circuit that differentiates the ONU upstream signal. The differentiating circuit differentiates the ONU upstream signal to amplify the signal and output a signal having a large amplitude at a point where the ONU upstream signal changes greatly (rising edge, falling edge).

  12A is a diagram illustrating a theoretical waveform of an ONU upstream signal, FIG. 12B is a diagram illustrating an actual waveform of the ONU upstream signal, and FIG. 12C is a diagram illustrating an ONU upstream signal. It is a figure which shows the waveform which differentiated the signal. As shown in FIG. 12A, when the burst light interval is short, the signal interval is small in the ONU upstream signal. Then, as shown in FIG. 12B, in the actual ONU upstream signal, the rising and falling portions are dull, and therefore there is a possibility that the edge is not detected when the signal interval is small. Therefore, the edge detection unit 40 differentiates the ONU upstream signal. As a result, as shown in FIG. 12C, the rising and falling portions of the ONU upstream signal are amplified. Therefore, the edge detection unit 40 can accurately detect the edge. When the edge detection unit 40 detects an edge, the edge detection unit 40 outputs an edge detection signal to the determination unit 22. The edge detection signal is output from the edge detection unit 40 every time an edge is detected.

  The determination unit 22 measures the edge detection signal output from the edge detection unit 40 for a certain period and analyzes the number of edge detection signals to determine the presence / absence of ONU upstream burst light, that is, the presence / absence of ONU 7. When the determination unit 22 receives the edge detection signal output from the edge detection unit 40, the determination unit 22 counts the number of times the edge detection signal is received. The determination unit 22 determines that the ONU 7 is present when the edge detection signal is counted a predetermined number of times. The predetermined number of times is set to one or more times. From the viewpoint of preventing erroneous determination due to the influence of noise, it is preferable to set the predetermined number to a plurality of times. The determination unit 22 outputs the determination result to the display unit 24.

  As described above, in the detection device 10D of the present embodiment, the edge detection unit 40 detects the edge of the ONU upstream signal and outputs an edge detection signal, and the determination unit 22 analyzes the number of times of the edge detection signal. The presence or absence of an optical line termination device is determined. Thus, the detection device 10D does not require a device such as an AD conversion unit. Therefore, the configuration of the detection device 10D can be simplified.

  Here, as described above, in the general PON communication system, the pulse width of the burst light transmitted from the ONU 7 is, for example, in units of microseconds. Therefore, in order to accurately acquire the ONU upstream signal, the AD conversion unit The period for acquiring and converting the analog signal is set to the pulse width or less. When the performance of the CPU is low, AD conversion takes time. If the conversion time is longer than the pulse width time of the ONU upstream signal, the ONU upstream signal may not be acquired. Therefore, when the signal acquisition cycle is set to be equal to or less than the pulse width, a high-performance CPU is required, and the data recording area needs to be enlarged because the acquired data for the measurement period increases. As a result, the production cost of the apparatus may increase. On the other hand, since the detection device 10D can determine the presence or absence of the ONU 7 without performing AD conversion, it can accurately determine the presence or absence of the ONU 7 even if it does not have a high-performance CPU or the like. Can do.

  In the present embodiment, the edge detection unit 40 detects an edge by differentiating the ONU upstream signal that has passed through the AC coupling unit 14. Thereby, it becomes possible to detect an edge more reliably. As a result, the detection device 10D can accurately determine the presence or absence of the ONU 7.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

  For example, in the detection apparatus 10A according to the second embodiment, the determination unit 22 sets a threshold value according to the maximum intensity signal stored in the peak intensity recording unit 26, and analyzes the maximum intensity signal exceeding the threshold value, thereby determining the ONU7. You may determine the presence or absence of.

  13 and 14 are diagrams for explaining setting of a threshold value in a determination unit of a detection device according to another embodiment. 13 and 14, the ONU upstream signal is indicated by a solid line, and the noise signal is indicated by a broken line. FIG. 14 illustrates a case where the determination unit 22 has a fixed threshold value, that is, a case where the threshold value is unchanged. The noise signal is, for example, an AC component of the OLT downstream signal when the AC coupling unit 14 cannot completely remove the component of the OLT downstream signal, and is superimposed on the ONU upstream signal. As shown in FIG. 13A, when the value of the noise signal does not exceed the preset threshold value, the determination unit 22 determines that the ONU 7 is in the state where the maximum intensity value of the ONU upstream signal exceeds the threshold value. It is determined that there is. However, as shown in FIG. 13B, when the value of the noise signal exceeds the threshold value, the determination unit 22 captures the noise signal as the maximum intensity value of the ONU upstream signal. When the value exceeds the threshold, it is erroneously determined that there is an ONU 7.

  Therefore, the determination unit 22 sets a threshold according to the maximum intensity value of the ONU upstream signal stored in the peak intensity recording unit 26. Specifically, the determination unit 22 acquires the maximum intensity value of the ONU upstream signal, and sets a value smaller than the maximum intensity value by a predetermined value as the threshold value. That is, the determination unit 22 varies the threshold according to the maximum intensity value of the ONU upstream signal. The predetermined value may be appropriately set according to the design, but is set, for example, as a ratio with respect to the maximum intensity value. Thereby, for example, as shown in FIG. 14B, even if the value of the noise signal is large as in FIG. 13B, the threshold value is set according to the maximum intensity value of the ONU upstream signal. For example, the noise signal can be set so as not to exceed the threshold value by making the value larger than the threshold value shown in FIG. Thereby, in the determination part 22, since it determines that a noise signal is mistakenly determined as a strongest signal, it can determine the presence or absence of ONU7 exactly.

DESCRIPTION OF SYMBOLS 7 ... ONU (optical line termination device), 9 ... Optical cable, 10, 10A, 10B, 10C, 10D ... Detection device, 12 ... Leakage light acquisition part (voltage signal conversion part), 14 ... AC coupling part (signal passage part) , 22 ... determination part, 25 ... light receiving element, 26 ... peak intensity recording part, 28 ... light source part (first light source part), 30 ... light receiving part, 34 ... high reflection light source part (second light source part), 40 ... edge Detection unit.

Claims (12)

A detection device for detecting the presence or absence of an optical line termination device,
Light leakage from an optical cable is received by a light receiving element, and in the leaked light, a downstream light signal transmitted toward the optical line terminator is converted into a voltage signal having a DC component, and the optical line terminator A voltage signal conversion unit that converts the upstream light signal transmitted from the signal into a voltage signal having a burst-like pulse waveform;
A signal passing unit that removes the downstream optical signal having the DC component from the voltage signal converted by the voltage signal converting unit, and passes the upstream optical signal having the burst pulse waveform; ,
A detection device comprising: a determination unit that measures the upstream optical signal that has passed through the signal passing unit for a certain period of time and analyzes the upstream optical signal to determine the presence or absence of the optical line termination device. An edge detection unit that detects an edge of the upstream light signal that has passed through the signal passing unit and outputs an edge detection signal in response to detecting the edge,
The said determination part measures the said edge detection signal output from the said edge detection part for a fixed period, and determines the presence or absence of the said optical line termination | terminus apparatus by analyzing the frequency | count of the said edge detection signal. Detection device.   The detection device according to claim 2, wherein the edge detection unit differentiates the upstream light signal that has passed through the signal passage unit to detect the edge.   The detection device according to claim 1, wherein the determination unit determines that the optical line termination device is present when a signal having a higher intensity than a noise signal exists in the upstream optical signal. A peak intensity recording unit that records the highest intensity signal having the highest signal intensity in the upstream light signal that has passed through the signal passing unit within the predetermined period;
The detection device according to claim 1, wherein the determination unit determines the presence or absence of the optical line termination device based on the maximum intensity signal recorded in the peak intensity recording unit.   The determination unit obtains an average value of a noise signal from the upstream light signal that has passed through the signal passing unit, and compares the average value of the noise signal with the maximum intensity signal recorded in the peak intensity recording unit. The detection device according to claim 5, wherein the optical line termination device is determined to be present when the strongest signal is significantly different from an average value of the noise signal.   6. The detection device according to claim 5, wherein the determination unit determines that the optical line termination device is present when a value of the maximum intensity signal recorded in the peak intensity recording unit exceeds a preset threshold value. . A peak intensity recording unit that records the highest intensity signal having the highest signal intensity in the upstream light signal that has passed through the signal passing unit within the predetermined period;
The determination unit sets a threshold according to the maximum intensity signal stored in the peak intensity recording unit, and determines the presence or absence of the optical line termination device by analyzing the maximum intensity signal exceeding the threshold, The detection apparatus as described in any one of Claims 1-4. The leakage light is leakage light obtained by deforming the optical cable,
The detection device according to claim 1, wherein at least two light receiving elements are provided along a longitudinal direction of the optical cable and sandwiching a deformed portion. A first light source unit for sending a first light toward the optical line terminator side with respect to the optical cable;
A light receiving unit that receives backscattered light of the first light transmitted from the first light source unit and incident on the optical cable;
The determination unit obtains a return loss based on the intensity of the first light transmitted from the first light source unit and the backscattered light received by the light receiving unit, and based on the return loss The detection device according to claim 1, wherein the presence or absence of the optical line termination device is determined. The optical cable is disposed immediately before the optical line termination device, and is provided with a reflecting portion that reflects light of a specific wavelength,
A second light source unit that transmits second light having a wavelength different from that of the first light transmitted from the first light source unit and reflected by the reflecting unit;
The determination unit includes the intensity of the second light transmitted from the second light source unit and the second light transmitted from the second light source unit and incident on the optical cable and received by the light receiving unit. The return loss is obtained based on the backscattered light, and when the reflection by the reflection unit is confirmed from the return loss, the optical line termination is combined with the measurement result of the return loss of the first light. The detection device according to claim 10, wherein presence or absence of the device is determined. A detection method for detecting the presence or absence of an optical line termination device,
Light leakage from an optical cable is received by a light receiving element, and in the leaked light, a downstream light signal transmitted toward the optical line terminator is converted into a voltage signal having a DC component, and the optical line terminator A voltage signal conversion step of converting the upstream light signal transmitted from the signal into a voltage signal having a burst-like pulse waveform;
A signal passing step for removing the downstream optical signal having the DC component from the voltage signal converted in the voltage signal converting step and passing the upstream optical signal having the burst pulse waveform; ,
And a determination step of determining the presence or absence of the optical line terminator by measuring the upstream optical signal passed in the signal passing step for a certain period and analyzing the upstream optical signal.

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