JP5990310B1 - ONU detection apparatus and ONU detection method - Google Patents

Abstract

An ONU detection device and a detection method that do not cause detection failure or erroneous detection due to S / N ratio deterioration. An ONU (Optical Network Unit) detection device 40 is a device that detects an ONU 30, and deforms an optical cable 70, receives light leaking from the deformed portion, and generates an electrical signal; A light intensity measuring unit 43 for measuring the light intensity in the light receiving unit based on the electrical signal generated by the unit, and the local device 10 side from the light receiving unit until the light intensity measured by the light intensity measuring unit becomes an appropriate light intensity Measurement is performed by a bend imparting unit 41 that imparts a bend to the optical cable, an ONU detection unit 44 that detects the intensity of the waveform characteristic of the transmitted light from the ONU included in the electrical signal generated by the light receiving unit, and a light intensity measurement unit. When the detected light intensity is an appropriate light intensity, the determination unit 45 determines that the ONU is connected if the intensity of the waveform feature detected by the ONU detection unit is equal to or greater than a certain level. Equipped with a. [Selection] Figure 2

Description

  The present invention relates to an ONU detection apparatus and an ONU detection method for detecting an ONU (Optical Network Unit), and in particular, in an access network having a PON (Passive Optical Network) configuration, an attempt is made to perform maintenance during an optical fiber network maintenance operation. The present invention relates to an optical access network maintenance technique for determining whether an ONU is connected to the lower part of an optical cable.

  In an optical access network having a PON configuration, a plurality of ONUs are connected to one in-station device via an optical branching unit. For this reason, signal light for other users is conducted even in an optical cable that is connected to the intra-station device and not connected to the ONU.

  In the maintenance and operation of the optical access network, work on the optical cable such as cutting and reconnecting the optical cable occurs. At this time, it is detected that the optical cable is not in service, that is, the ONU is not connected to the lower part. There is a need.

  In an optical access network having a PON configuration, signal light is also conducted to an optical cable having no ONU connected to the lower part thereof. For this reason, it is necessary to detect whether or not the ONU is connected by detecting the transmission light from the ONU from the signal light that is conducted to the optical cable (see Patent Documents 1 and 2).

  FIG. 9 is a diagram for explaining the outline of the prior art (Patent Document 1). As shown in this figure, a plurality of ONUs 30 are connected to one intra-station device 10 via an optical branching unit 20. The bending portion 400 bends the optical cable 70, and light leaked from the optical cable 70 (hereinafter referred to as leakage light) is received by the light receivers 401 and 402 disposed on the upper side and the lower side of the bending portion 400, respectively, and an electric signal is received. Is generated. Based on this electric signal, the presence or absence of connection of the ONU 30 is detected by electrically detecting the waveform characteristic (intermittent waveform) of the transmission light from the ONU 30.

JP 2012-205284 A JP 2012-060290 A

  In the prior art, in order to separately detect the upstream light 60 and downstream light 50 of the optical cable 70, the light receivers 401 and 402 are disposed on the upper side and the lower side of the bent part 400, respectively, and an electric signal is generated. . However, it is difficult to completely separate the upstream light 60 and downstream light 50, and a certain proportion of downstream light 50 and upstream light 60 are unintentionally received by the upper and lower light receivers 401 and 402, respectively. End up. For this reason, in the bending unit 400, when the downstream light 50 from the intra-station device 10 is larger than the upstream light 60 from the ONU 30, the S / N ratio of the electrical signal of the upstream light 60 is degraded due to the reception of the downstream light 50. However, there is a problem that the connection of the ONU 30 cannot be detected correctly.

  An object of the present invention is to provide an ONU detection device and an ONU detection method that do not cause detection failure or erroneous detection due to S / N ratio deterioration.

  To achieve the above object, the invention according to the first aspect is an ONU detection device for detecting an ONU (Optical Network Unit), which deforms an optical cable, receives light leaking from the deformed portion, and generates an electrical signal A light intensity measuring unit that measures the light intensity in the light receiving unit based on an electrical signal generated by the light receiving unit, and the light intensity measured by the light intensity measuring unit is an appropriate light intensity. A bend applying unit that bends the optical cable on the local device side from the light receiving unit, and an ONU detection unit that detects the intensity of the waveform characteristic of the transmitted light from the ONU included in the electrical signal generated by the light receiving unit When the light intensity measured by the light intensity measurement unit is an appropriate light intensity, if the intensity of the waveform feature detected by the ONU detection unit is greater than or equal to a certain level, it is determined that the ONU is connected. Judgment part And summarized in that it comprises a.

  In the invention according to the second aspect, in the invention according to the first aspect, as the lower limit of the appropriate light intensity, a value at which downstream light having a predetermined minimum light intensity reaches the ONU even when the lower line loss is maximum. Is set as the gist.

  The invention according to the third aspect is the invention according to the second aspect, wherein the predetermined minimum light intensity is set as the lower limit of the appropriate light intensity even when the ONU detection device is installed by mistake in the vertical direction of the optical cable. The gist is that the value at which the downstream light reaches the ONU is set.

  The invention according to a fourth aspect is the invention according to any one of the first to third aspects, wherein as the upper limit of the appropriate light intensity, upstream light having a predetermined S / N ratio is received by the light receiving unit. The gist is that the value is set.

  The invention according to the fifth aspect is an ONU detection method in which the ONU detection device detects an ONU, wherein the optical cable is deformed, the light leaking from the deformed portion is received by the light receiving unit, and an electric signal is generated. A light intensity measuring step for measuring the light intensity in the light receiving unit based on the electrical signal generated in the light receiving step; and from the light receiving unit until the light intensity measured in the light intensity measuring step becomes an appropriate light intensity. A bending step for bending the optical cable on the intra-office device side, an ONU detection step for detecting the intensity of the waveform characteristic of the transmitted light from the ONU included in the electrical signal generated by the light receiving unit, and the light intensity When the light intensity measured in the measurement step is an appropriate light intensity, if the intensity of the waveform feature detected in the ONU detection step is a certain level or more, the ONU And summary to include a determination step to have been continued.

  According to the present invention, it is possible to provide an ONU detection device and an ONU detection method that do not cause detection failure or erroneous detection due to S / N ratio deterioration.

It is a figure which shows the whole structure and usage scene of the system which uses the ONU detection apparatus in embodiment of this invention. It is a functional block diagram of the ONU detection apparatus in embodiment of this invention. It is a flowchart which shows the operation | movement which determines whether ONU is connected to the optical cable lower part using the ONU detection apparatus in embodiment of this invention. It is a figure for demonstrating the light intensity in a prior art. It is a figure for demonstrating the light intensity at the time of utilizing the ONU detection apparatus in embodiment of this invention. It is a figure for demonstrating the light intensity at the time of utilizing the ONU detection apparatus in embodiment of this invention. It is a figure for demonstrating the range of the suitable light intensity adjusted by the bending provision part in embodiment of this invention. It is a figure which shows the bending provision part in embodiment of this invention. It is a figure for demonstrating the outline | summary of a prior art.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments exemplify ONU detection devices for embodying the technical idea of the present invention, and the device configuration, data configuration, and the like are limited to the following embodiments. is not.

(System configuration)
FIG. 1 is a diagram showing an overall configuration and usage scene of a system that uses an ONU detection device 40 according to an embodiment of the present invention. As shown in FIG. 1A, in an access network having a PON configuration, an ONU detection device 40 is used for maintenance operation of an optical fiber network.

  The PON (Passive Optical Network) is an optical communication network in which one intra-station device 10 and a plurality of ONUs 30 are connected to the optical branching device 20 via the optical cable 70. Hereinafter, the direction from the in-station device 10 toward the ONU 30 is referred to as “downward direction”, and the direction from the ONU 30 toward the in-station device 10 is referred to as “upward direction”. Further, light flowing in the downstream direction is referred to as “downstream light 50”, and light flowing in the upstream direction is referred to as “upstream light 60”. Further, the in-station device 10 side is called “upper side”, and the ONU 30 side is called “lower side”.

  An intra-station device (OLT, optical line terminal station device) 10 is a line terminal device on the communication station side used in PON. Generally, it is connected to the core network of a communication carrier through several switches and routers. As shown in FIG. 1B, the transmission light (downstream light 50) of the intra-station device 10 is steady light that is constantly radiated although it fluctuates.

  The optical branching device (optical splitter) 20 is a branching device that connects one optical cable 70 and a plurality of optical cables 70. The optical signal is split and split, but the signal intensity decreases according to the number of branches.

  The ONU (optical line termination unit) 30 is a user-side line termination unit used in the PON. Generally, it is installed in a user's home and connected to a home gateway or a user PC terminal. The transmission light (upstream light 60) of the ONU 30 is intermittent light that repeats blinking, as shown in FIG.

  The ONU detection device 40 is a device that detects the ONU 30. It is attached to the optical cable 70 to be maintained, and it is determined whether the ONU 30 is connected to the lower part thereof.

(ONU detection device)
FIG. 2 is a functional block diagram of the ONU detection device 40 according to the embodiment of the present invention. As shown in this figure, the ONU detection device 40 includes a bend imparting unit 41, a light receiving unit 42, a light intensity measurement unit 43, an ONU detection unit 44, and a determination unit 45.

  The light receiving unit 42 deforms the optical cable 70, and the light leaking from the deformed portion is received by the light receiver 42A to generate an electrical signal. For example, as disclosed in Patent Document 1, the optical cable 70 can be deformed by sandwiching the optical cable 70 between a convex portion and a concave portion.

  The light intensity measurement unit 43 measures the light intensity in the light receiving unit 42 based on the electrical signal generated by the light receiving unit 42. Specifically, the intensity of the light incident on the light receiving unit 42 (the sum of the upstream light 60 and the downstream light 50) is measured for a certain period of time and displayed based on the time average value. This display content is not particularly limited. For example, some information such as numbers may be displayed, and the operator may determine whether the light intensity is appropriate. Alternatively, the light intensity measurement unit 43 may determine whether the light intensity is appropriate or inappropriate and display the determination result.

  The bend imparting unit 41 bends the optical cable 70 in the vicinity of the light receiving unit 42 until the light intensity measured by the light intensity measuring unit 43 becomes an appropriate light intensity. When the ONU detection device 40 is correctly installed, bending is applied on the upper side of the light receiving unit 42 (on the intra-office device 10 side), but when the ONU detection device 40 is installed by mistake, the lower side of the light receiving unit 42 ( The bending is applied on the ONU 30 side). The bending strength can be adjusted by an intended amount by a combination of a fiber guide and an adjusting screw (described later).

  The ONU detection unit 44 detects the intensity of the waveform characteristic of the transmission light from the ONU 30 included in the electrical signal generated by the light receiving unit 42. Specifically, the time variation of the light intensity received by the light receiving unit 42 is observed for a certain time, and the feature point (intermittent light) of the upstream light 60 from the ONU 30 is extracted. In extracting the feature points, a deviation with variation variation may be measured, or a frequency filter may be applied to the electrical signal.

  The determination unit 45 is connected to the ONU 30 if the intensity of the waveform feature detected by the ONU detection unit 44 is not less than a certain level when the light intensity measured by the light intensity measurement unit 43 is an appropriate light intensity. Is determined. Specifically, the intensity of the feature point (intermittent light) extracted by the ONU detection unit 44 is observed, and if it is above a certain level, it is displayed that the ONU 30 has been detected.

  As described above, in the embodiment of the present invention, in order to receive the upstream light 60 having a high S / N ratio, two upstream and downward light receivers are not arranged to separate the upstream light 60 and the downstream light 50. The optical cable 70 is bent at the upper part of the light receiving part 42A, and the downstream light 50 is lost by the bending. In this way, the downstream light 50 is reduced and does not adversely affect the S / N ratio of the upstream light 60, so that the upstream light 60 having a high S / N ratio can be received.

(Operation)
FIG. 3 is a flowchart showing an operation of determining whether the ONU 30 is connected to the lower part of the optical cable 70 using the ONU detection device 40 according to the embodiment of the present invention.

  First, the ONU detection device 40 is attached to the optical cable 70, and the light intensity is detected (measured) in a state where the optical cable 70 is not bent by the bending applying unit 41 (S1).

  In this state, when the light intensity is appropriate, the ONU detection result is confirmed (S2 → S3). As a result, if the ONU 30 is detected, it is determined that “ONU exists” (S3 → S5), and if the ONU 30 is not detected, it is determined that “ONU does not exist” (S3 → S4).

  On the other hand, when the light intensity is not appropriate, the bending is applied to the optical cable 70 by the bend applying unit 41, and the bending strength is adjusted until it becomes appropriate (S2 → S6). If the light intensity is appropriate, the ONU detection result is confirmed in this state (S7). As a result, if the ONU 30 is detected, it is determined that “ONU is present” (S7 → S8). If the ONU 30 is not detected, the optical cable 70 is switched up and down (left and right) to check the ONU detection result ( S7 → S9 → S10). As a result, if the ONU 30 is detected, it is determined that “ONU exists” (S10 → S11). If the ONU 30 is still not detected, it is determined that “ONU does not exist” (S10 → S12).

  As described above, in the embodiment of the present invention, the ONU 30 can be detected while the optical cable 70 is switched upside down. Therefore, even if the upper and lower sides of the optical cable 70 cannot be distinguished, it is finally possible to detect the presence or absence of the ONU 30.

  Here, the upper and lower sides of the optical cable 70 are interchanged, but the present invention is not limited to this. That is, there is an embodiment in which the bend imparting portions 41 are provided on both sides (up and down) of the light receiving unit 42 instead of switching the upper and lower sides of the optical cable 70.

  In addition, in such an embodiment, there is an embodiment in which the upper and lower bending imparting portions 41 are interlocked with a wire or the like and the upper and lower bending are switched with one touch.

  In such an embodiment, there is also an embodiment in which the ONU detection device 40 automatically performs the measurement after the bending is applied by the appropriate bending applying unit 41 of the measuring method. For example, for each measurement value of the upper and lower bending imparting portions 41, it may be determined whether there is a signal having an intensity exceeding a preset threshold value. In this case, when there is a signal having an intensity exceeding a preset threshold value, it can be determined that the measurement is performed after the bending by the appropriate bending applying unit 41.

  In addition, there is also an embodiment in which the ONU detection device 40 automatically performs all procedures of the detection method by providing the ONU detection device 40 with a function of automatically applying bending with a motor or the like.

(Comparative example)
4A and 4B are diagrams for explaining the light intensity in the prior art. FIG. 4A shows an example that can be detected by the prior art, and FIG. 4B shows an example that cannot be detected by the prior art. How the light intensity of the downstream light 50 (transmitted light intensity of the in-station device 10) and the light intensity of the upstream light 60 (transmitted light intensity of the ONU 30) change in the station, the detection location, and the ONU installation location Is shown.

  As shown in this figure, the light intensity of the downstream light 50 from the intra-station device 10 gradually decreases due to the line loss, and similarly, the light intensity of the upstream light 60 from the ONU 30 also gradually decreases due to the line loss. Here, as shown in FIG. 4A, when the line loss between the station and the detection location is sufficiently large, the light intensity of the downstream light 50 at the detection location is sufficiently smaller than the light intensity of the upstream light 60. The light intensity is suitable for detecting the ONU 30. On the other hand, as shown in FIG. 4B, when the line loss between the station and the detection location is small, the light intensity of the downstream light 50 is increased, which increases noise, and the S / N ratio is deteriorated. Cannot detect the connection.

(Example)
FIG. 5 is a diagram for explaining the light intensity when the ONU detection device 40 according to the embodiment of the present invention is used. Here, a case where the ONU detection device 40 is correctly installed in an example that cannot be detected by the conventional technology will be described.

  As shown in this figure, even when the line loss between the station and the detection place is small, the bending imparting unit 41 generates a bending loss according to the measurement result of the light intensity measuring unit 43 to obtain an appropriate light intensity. Therefore, the ONU 30 can be detected. In addition, the ONU 30 can be detected in a state in which the upstream light 60 and the downstream light 50 reach the opposing device by bending to give an appropriate light intensity according to the measurement result of the light intensity measuring unit 43. Is possible.

  FIG. 6 is a diagram for explaining the light intensity when the ONU detection device 40 according to the embodiment of the present invention is used. Here, a case will be described in which the ONU detection device 40 is erroneously installed in an example that cannot be detected by the conventional technology.

  As shown in this figure, even when the ONU detection device 40 is installed by mistake in the vertical direction of the optical cable 70, by bending to give an appropriate light intensity according to the measurement result of the light intensity measurement unit 43, The ONU 30 can be detected while the upstream light 60 and the downstream light 50 reach the opposing device. In this case, the ONU 30 cannot be detected due to the deterioration of the S / N ratio, but the ONU 30 can finally be detected by performing the detection operation again by switching the vertical direction.

(Appropriate light intensity range)
FIG. 7 is a diagram for explaining a range of an appropriate light intensity adjusted by the bending imparting unit 41. Here, it is assumed that the installation location of the intra-station device 10 is a point A, the installation location of the ONU detection device 40 is a location C, and the installation location of the ONU 30 is a location B. The maximum line loss between points A and B is xdB, and the maximum line loss between points C and B is ydB. The transmission intensity of the downstream light 50 is a maximum a1 dBm to a minimum a2 dBm, and the variation rate is w% or less. It is assumed that the signal is designed to reach the ONU 30 even if the transmission intensity of the downstream light 50 is a minimum of a2 dBm. The transmission intensity of the upstream light 60 is assumed to be a maximum b1 dBm to a minimum b2 dBm. The S / N ratio required in the ONU detection device 40 is N% or more.

  First, an appropriate lower limit of light intensity will be described. The light intensity required at the point C is downlink (a2-x + y) dBm and uplink (b2-y) dBm. The light intensity at the point C to satisfy this is ADD [(a2-x + y), b1-y], ADD [(a1-x + y), b2-y]. Therefore, the lower limit value is the larger of ADD [(a2-x + y), b1-y] and ADD [(a1-x + y), b2-y]. ADD [p, q] is as shown in the following equation.

次に、適切な光強度の上限を説明する。地点Ｃにおいて上り光強度は、次式のようになる。

Next, an appropriate upper limit of light intensity will be described. The upstream light intensity at the point C is as follows.

Ｓ／Ｎ比がＮ％のときのノイズ強度は、次式のようになる。

The noise intensity when the S / N ratio is N% is as follows.

変動率がｗ％のときの下り光強度は、次式のようになる。

The downstream light intensity when the variation rate is w% is as follows.

Ｓ／Ｎ比がＮ％以上となるためには、光強度の上限値は、次式のようになる。

In order for the S / N ratio to be N% or more, the upper limit value of the light intensity is expressed by the following equation.

このように算出された適切な光強度の範囲は光強度測定部４３に設定される。これにより、光強度測定部４３は、測定した光強度の適切または不適切を自動で判定することができる。

An appropriate light intensity range calculated in this way is set in the light intensity measurement unit 43. Thereby, the light intensity measurement unit 43 can automatically determine whether the measured light intensity is appropriate or inappropriate.

(Bend imparting part)
FIGS. 8A and 8B are diagrams showing the bending imparting portion 41 in the embodiment of the present invention, where FIG. 8A shows a case where a weak bending is given, and FIG. 8B shows a case where a strong bending is given.

  As shown in this figure, an optical cable 70 is inserted through the fiber guides 41A and 41B. The position of the fiber guide 41D can be adjusted by an adjustment screw 41C provided between the fiber guides 41A and 41B. As the adjustment screw 41C is tightened, the position of the fiber guide 41D is lowered, and the optical cable 70 can be strongly bent. Even when the strongest bend is applied, the optical cable 70 is not broken, but communication is cut off. Of course, the position, size, number, etc. of the fiber guides 41A, 41B, 41D and the adjusting screw 41C can be changed as appropriate.

  As described above, the ONU detection device 40 according to the embodiment of the present invention is a device that detects the ONU 30, and is a light receiving unit that deforms the optical cable 70, receives light leaking from the deformed portion, and generates an electrical signal. 42, a light intensity measuring unit 43 that measures the light intensity in the light receiving unit 42 based on the electrical signal generated by the light receiving unit 42, and until the light intensity measured by the light intensity measuring unit 43 becomes an appropriate light intensity. A bend applying unit 41 that bends the optical cable 70 on the local device 10 side from the light receiving unit 42, and an ONU detection that detects the intensity of the waveform characteristic of the transmitted light from the ONU 30 included in the electrical signal generated by the light receiving unit 42. When the intensity of the waveform feature detected by the ONU detection unit 44 is not less than a certain level when the light intensity measured by the unit 44 and the light intensity measurement unit 43 is an appropriate light intensity, the ONU 30 is in contact. It is provided with a determination unit 45 that. That is, since the bend imparting unit 41 provided in the vicinity of the light receiving unit 42 is bent from the light receiving unit 42 of the optical cable 70 to the local device 10 side, the downstream light 50 can be lost. As a result, the downstream light 50 can be lost on the side of the in-station device 10 from the light receiving unit 42, so that the light intensity of the downstream light 50 reaching the light receiving unit 42 is weakened, and detection failure or false detection due to S / N ratio deterioration occurs. Does not occur.

  Here, a value at which the downstream light 50 having a predetermined minimum light intensity reaches the ONU 30 is set as an appropriate lower limit of the light intensity even when the lower line loss is maximum. As a result, the ONU 30 can be detected while the upstream light 60 and the downstream light 50 reach the opposing device.

  Further, as an appropriate lower limit of the light intensity, even when the ONU detection device 40 is installed by mistake in the vertical direction of the optical cable 70, a value at which the downstream light 50 having a predetermined minimum light intensity reaches the ONU 30 is set. Thereby, even when the ONU detection device 40 is installed by mistake in the vertical direction of the optical cable 70, it is possible to perform the ONU 30 detection operation in a state where the upstream light 60 and the downstream light 50 reach the opposing device.

  In addition, a value at which the upstream light 60 having a predetermined S / N ratio is received by the light receiving unit 42 is set as an appropriate upper limit of the light intensity. As a result, the upstream light 60 having a high S / N ratio can be received, so that the ONU 30 can be detected with high accuracy.

  The ONU detection method according to the embodiment of the present invention is a method in which the ONU detection device 40 detects the ONU 30, which deforms the optical cable 70, receives light leaking from the deformed portion by the light receiving unit 42, and receives an electrical signal. A light receiving step to be generated, a light intensity measuring step for measuring the light intensity in the light receiving unit 42 based on the electrical signal generated in the light receiving step, and the light intensity measured in the light intensity measuring step until an appropriate light intensity is obtained. A bending applying step for bending the optical cable 70 on the local device 10 side from the light receiving unit 42, and an ONU detecting step for detecting the intensity of the waveform characteristic of the transmitted light from the ONU 30 included in the electrical signal generated by the light receiving unit 42 When the light intensity measured in the light intensity measurement step is an appropriate light intensity, the intensity of the waveform feature detected in the ONU detection step is And a and determining steps if constant over ONU30 is connected. As a result, the downstream light 50 can be lost on the side of the in-station device 10 from the light receiving unit 42, so that the light intensity of the downstream light 50 reaching the light receiving unit 42 is weakened, and detection failure or false detection due to S / N ratio deterioration occurs. Does not occur.

  Of course, the present invention includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

10 ... Intra-station equipment 20 ... Optical splitter 30 ... ONU
DESCRIPTION OF SYMBOLS 40 ... ONU detection apparatus 41 ... Bending provision part 42 ... Light receiving part 42A ... Light receiver 43 ... Light intensity measurement part 44 ... ONU detection part 45 ... Judgment part 50 ... Down light 60 ... Up light 70 ... Optical cable

Claims (5)

An ONU detection device that detects an ONU (Optical Network Unit),
A light receiving portion that deforms the optical cable, receives light leaking from the deformed portion, and generates an electrical signal;
A light intensity measuring unit that measures the light intensity in the light receiving unit based on the electrical signal generated by the light receiving unit;
A bend applying unit that applies bending to the optical cable on the local device side from the light receiving unit until the light intensity measured by the light intensity measuring unit becomes an appropriate light intensity;
An ONU detector that detects the intensity of the waveform characteristic of the transmitted light from the ONU included in the electrical signal generated by the light receiver;
A determination unit that determines that the ONU is connected if the intensity of the waveform feature detected by the ONU detection unit is greater than or equal to a certain level when the light intensity measured by the light intensity measurement unit is an appropriate light intensity. An ONU detection device comprising:   2. The ONU detection device according to claim 1, wherein a value at which downstream light having a predetermined minimum light intensity reaches the ONU is set as the lower limit of the appropriate light intensity even when the lower line loss is maximum. .   As the lower limit of the appropriate light intensity, even when the ONU detection device is installed by mistake in the vertical direction of the optical cable, a value at which downstream light with a predetermined minimum light intensity reaches the ONU is set. The ONU detection apparatus according to claim 2.   4. The ONU according to claim 1, wherein a value at which upstream light having a predetermined S / N ratio is received by the light receiving unit is set as the upper limit of the appropriate light intensity. Detection device. An ONU detection method in which an ONU detection device detects an ONU,
A light receiving step for deforming the optical cable, receiving light leaking from the deformed portion at the light receiving unit, and generating an electrical signal;
A light intensity measuring step for measuring light intensity in the light receiving unit based on the electrical signal generated in the light receiving step;
A bending step for bending the optical cable on the local device side from the light receiving unit until the light intensity measured in the light intensity measurement step becomes an appropriate light intensity;
An ONU detection step of detecting the intensity of the waveform characteristic of the transmitted light from the ONU included in the electrical signal generated by the light receiving unit;
A determination step of determining that the ONU is connected if the intensity of the waveform characteristic detected in the ONU detection step is a certain level or more when the light intensity measured in the light intensity measurement step is an appropriate light intensity. The ONU detection method characterized by including these.

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