JP6533190B2 - Optical repeater and optical repeater method - Google Patents

Description

  The present invention relates to an optical repeater and an optical repeater method.

  Due to the explosive increase in the amount of communication traffic in recent years, an optical access network connecting between a master station device and a subscriber device is required to have higher speed. In addition, the optical access network is also required to have an economic efficiency that the service price is not increased even if the speed is increased. A PON (Passive Optical Network) is mentioned as a candidate of the optical access network which can make high speed and economy compatible.

Description of PON PON is an optical access network based on modulation of an optical signal using an optical fiber. The network topology of PON is a star topology. The PON can achieve a wider band than a conventional network using metal wiring. PON is a network with excellent economy. The PON is an optical subscriber line termination unit (OSU: Optical Subscriber) of an optical subscriber line termination unit (OLT: Optical Line Terminal) which is a parent station unit only by optical branching by an optical splitter disposed in the middle of an optical fiber line. This is because it is possible to accommodate multiple users per one unit of unit). The optical subscriber line termination unit accommodates multiple users via an optical network unit (ONU).

-Importance of prolongation of transmission distance of PON When using PON, the distance (accommodation distance) between the subscriber apparatus and the master station apparatus that can be accommodated is defined in a standard such as IEEE or ITU-T. . For example, IEEE 802.3-2012 Std. The accommodation distance in the PX10 standard is less than 10 km. The definition of the accommodation distance means that building equipment for PON (hereinafter referred to as “communication building”) must be closely arranged according to the distribution of subscriber apparatuses. That is, equipment investment of the optical access network requires a certain number or more of communication buildings. For this reason, the definition of the accommodation distance is a factor that impairs the economy which is one of the excellent features of PON. Therefore, it is necessary to extend the accommodation range beyond the definition of the accommodation distance to widen the accommodation range, and to be able to accommodate many subscriber apparatuses in one communication building.

· Cautions for Longening As a method of extending, there is a method in which the optical repeater amplifies or regenerates the intensity (power) of the optical signal attenuated by the light propagation and the light branching. In this case, if the intensity of the amplified optical signal is equal to or greater than a specified value at the input of the optical receiver, an optical overinput condition occurs in the optical receiver. The optical receiver is, for example, an optical network unit (OSU) or an optical network unit (ONU). If an optical overinput condition occurs in the optical receiver, the optical receiver may be destroyed, which may make it impossible to communicate with the optical access network.

  Hereinafter, the direction from the optical subscriber line network device to the optical subscriber line termination device is referred to as “up”. Hereinafter, the direction from the optical subscriber line termination device to the optical subscriber line network device is referred to as “downward”.

  An optical repeater has been proposed to prevent the occurrence of an optical overinput condition. For example, Patent Document 1 discloses that transmission loss between a master station apparatus and a relay apparatus is predicted by detecting the intensity of an optical signal acquired from the master station apparatus. The relay apparatus disclosed in Patent Document 1 can prevent the occurrence of the excessive light input state in the optical receiver of the master station apparatus by adjusting the intensity of the upstream optical signal according to the transmission loss.

  Patent Document 2 discloses a method of controlling the intensity of the upstream optical signal and the intensity of the downstream optical signal. The light intensity controller disclosed in Patent Document 2 branches the upstream optical signal (upstream burst signal) from the optical subscriber line network device to the optical amplification element, and monitors the intensity of the upstream optical signal. The light intensity controller disclosed in Patent Document 2 performs feedforward control based on the intensity of the light signal at the front stage of light amplification. The light intensity controller disclosed in Patent Document 2 performs feedback control based on the intensity of the light signal in the subsequent stage of light amplification. The light intensity controller disclosed in Patent Document 2 may execute control based on both the intensity of the optical signal at the front stage of the optical amplification and the intensity of the optical signal at the rear stage of the optical amplification.

  The light intensity controller disclosed in Patent Document 2 can prevent the occurrence of an optical overinput condition in the optical subscriber line termination device and the optical subscriber line network device. The optical intensity controller disclosed in Patent Document 2 controls the intensity of the optical signal transmitted from the optical repeater (output power from the optical repeater), so that the optical subscriber line terminating board and the optical subscriber line network apparatus It is possible to prevent the occurrence of the light overload input condition in

Patent No. 5696952 gazette Patent No. 5419141 gazette

  However, the application range of the optical repeater may be limited due to the occurrence of an optical overinput condition in the optical repeater. Therefore, the availability of the optical repeater can be improved if the occurrence of the optical overinput condition in the optical repeater can be prevented.

  The relay apparatus disclosed in Patent Document 1 controls the intensity of the upstream optical signal transmitted from the relay apparatus to the optical subscriber line termination apparatus based on the optical signal strength acquired by the relay apparatus from the optical subscriber line termination apparatus. Do. As a result, the relay device disclosed in Patent Document 1 can prevent the occurrence of the optical overinput condition in the optical subscriber line termination device.

  The relay apparatus disclosed in Patent Document 1 generates an optical overinput state in the optical subscriber line termination apparatus when the optical signal acquired from the optical subscriber line termination apparatus by the relay apparatus is originally in the optical overinput state. Can not prevent. The relay apparatus disclosed in Patent Document 1 generates the optical excess input state in the optical subscriber line termination apparatus when the optical signal acquired from the optical subscriber line network apparatus by the relay apparatus is in the optical excess input state. It can not be prevented. The relay apparatus disclosed in Patent Document 1 can not prevent the occurrence of an optical overinput condition in the optical subscriber line network apparatus. The relay device disclosed in Patent Document 1 can not prevent the occurrence of the excessive light input state in the optical relay device.

  The light intensity controller disclosed in Patent Document 2 controls the intensity of the optical signal transmitted from the optical repeater. The light intensity controller disclosed in Patent Document 2 can prevent the occurrence of the light excessive input state in the master station device. The light intensity controller disclosed in Patent Document 2 can prevent the occurrence of an optical overinput condition in the optical subscriber line network device. The light intensity controller disclosed in Patent Document 2 can not prevent the occurrence of the light excessive input state in the optical repeater.

  Therefore, the relay apparatus disclosed in Patent Document 1 and the light intensity controller disclosed in Patent Document 2 can not prevent the occurrence of the excessive light input state in the optical relay apparatus. The inability to prevent the occurrence of an optical overinput condition in the optical repeater is a major obstacle to achieving the purpose of ensuring normal communication quality.

  For example, when an optical fiber amplifier or an optical semiconductor amplifier is used as an optical amplification element included in the optical repeater, the maximum allowable input power to the optical repeater is about -5 to +10 dBm. In PON, since there is variation in the accommodation distance of the optical subscriber line network device, the optical signal transmitted by the optical subscriber line network device in the vicinity of the optical relay device to the optical relay device is considered as an optical overinput condition in the optical relay device. May be

  Control of the intensity of the optical signal acquired by the optical repeater is technically very difficult. This is because the optical signal is input in a burst state to the input side of the upstream optical signal. The burst state is a state in which optical signals are input from a plurality of optical network units to the optical receiver while changing the intensity of the optical signal at high speed.

  When the optical repeater controls the intensity of the optical signal acquired by the optical repeater, the optical repeater transmits the optical signal to the optical attenuator for intensity control based on the intensity of the optical signal immediately after the acquisition by the optical repeater. It is necessary to determine the amount of attenuation of the optical signal before it arrives, and perform feedforward control in which the intensity of the optical signal is controlled by the optical attenuator in a short time.

  The optical repeater can not execute such a short time feedforward control. Therefore, in the conventional optical repeater, the occurrence of a light excess input state is prevented by using a fixed attenuator (fixed ATT) manually inserted into the optical repeater. The fixed attenuator is an optical attenuator for fixedly changing the intensity of the optical signal. However, when the operator manually inserts the optical attenuator into the optical relay device, there are a problem regarding complication of operation and a problem regarding light attenuation amount for prolongation.

Regarding Problems Related to Complex Operation When extending the optical access network, the optical repeater is also connected to the already existing optical subscriber line network equipment. In this case, the administrator of the optical access network can acquire distance information (information of optical fiber length) between the optical subscriber line network device and the optical repeater from the facility information database. The administrator of the optical access network can acquire the number of optical branches (the number of connection points) by the optical splitter disposed in the middle of the optical fiber from the facility information database.

  The administrator of the optical access network can prevent the occurrence of the optical overinput condition by inserting the optical attenuator into the optical repeater based on the information acquired from the facility information database. However, manually inserting an optical attenuator into an optical repeater by an operator or the like for each optical subscriber line network device existing in units of ten million units in Japan is not practically practical.

  The case where 500,000 optical subscriber line network devices corresponding to 10% of the 5,000,000 optical subscriber line network devices exist in the vicinity of the optical repeater will be described as an example. An optical over-input condition may occur in 500,000 optical subscriber line network devices existing in the vicinity of the optical repeater.

  The administrator needs to extract the information of the optical subscriber line network device that may cause an optical overinput condition from the facility information database based on the distance information and the number of optical branches extracted from the facility information database There is. In order to extract information from the facility information database, an operation cost (extraction operation cost) for extracting information occurs.

  The administrator etc. manually operates the optical attenuator having the optimum light attenuation amount to the optical subscriber line network device in the home of the user of 10,000 optical subscriber line network devices associated with the extracted information. Need to insert. Work within the user's home is not realistic from the perspective of the user's privacy. Regarding the operation of manually inserting the optical attenuator into the optical subscriber line network device, the time for the worker to move to the user's home, the time for the worker to measure the intensity of the optical signal, and the worker If it is assumed that the total of the time for determining the light attenuation amount and the time for the operator to insert the light attenuator is 1 hour and the unit price per hour is 5,000 yen, the extraction operation The total of the cost and the insertion cost is 2.5 billion yen (= 500,000 x 1 x 5,000), which is not realistic in cost.

Regarding the problem concerning the light attenuation amount for prolongation When workers and the like manually prevent insertion of the optical attenuator into the optical relay device to prevent occurrence of an excessive light input state in the optical relay device, it is inserted into the optical relay device. The optical attenuator may excessively attenuate the intensity of the optical signal acquired by the optical repeater. The fact that the optical attenuator excessively attenuates the intensity of the optical signal acquired by the optical repeater is against the purpose of prolonging the transmission distance of the PON by amplifying the intensity of the optical signal by the optical repeater. If the light attenuation amount is set to be excessively large, the effect of extending the optical access network is lost. If the light attenuation amount is set to be too small, an optical overinput condition occurs in the optical repeater.

  As described above, the conventional optical relay device has a problem in that the optical access network can not be extended when the occurrence of the excessive light input state in the optical relay device is prevented.

  In view of the above circumstances, it is an object of the present invention to provide an optical relay device and an optical relay method capable of extending the optical access network even when occurrence of an optical overinput condition in the optical relay device is prevented. And

  One aspect of the present invention is an optical relay apparatus for relaying an optical signal between a master station apparatus and a subscriber apparatus, which detects a pre-amplification intensity that is the intensity of the optical signal before the intensity is amplified. Pre-amplification intensity detection unit, optical amplifier for amplifying the intensity of the light signal, and post-amplification intensity detection unit for detecting the post-amplification intensity which is the intensity of the light signal after the intensity is amplified A control unit configured to adjust an attenuation amount of the optical signal in at least one of a front stage and a rear stage for amplifying the intensity based on the pre-amplification strength and the post-amplification strength.

  One embodiment of the present invention is the above optical repeater, wherein the control unit performs automatic level control on a variable optical attenuator that transmits the optical signal toward the master station device.

  One embodiment of the present invention is the above optical repeater, wherein the control unit controls the amplification amount of the intensity of the optical signal by the optical amplifier.

  One aspect of the present invention is the above optical relay device, wherein the optical relay device is provided in a master station provided with the master station device.

  One embodiment of the present invention is the above optical repeater, wherein the control unit joins the optical access network based on at least a part of the line loss between the master station apparatus and the subscriber apparatus. A value representing a condition under which the person device can be connected is calculated.

  One embodiment of the present invention is an optical relay method performed by an optical relay apparatus for relaying an optical signal between a master station apparatus and a subscriber apparatus, which is the intensity of the optical signal before the intensity is amplified. The steps of detecting the pre-amplification intensity, amplifying the intensity of the light signal, detecting the post-amplification intensity which is the intensity of the light signal after the intensity is amplified, and amplifying the intensity of the light signal Adjusting the attenuation amount of the optical signal in at least one of the former stage and the latter stage based on the pre-amplification strength and the post-amplification strength.

  According to the present invention, it is possible to extend the optical access network even when the occurrence of the optical overinput condition in the optical repeater is prevented.

It is a figure which shows the example of a structure of an optical access network in 1st Embodiment. It is a flowchart which shows the example of operation | movement of an optical access network in 1st Embodiment. It is a figure which shows the example of a structure of an optical access network in 2nd Embodiment. It is a figure which shows the example of a structure of an optical access network in 3rd Embodiment. It is a figure which shows the example of a structure of an optical access network in 4th Embodiment. It is a figure which shows the example of a structure of an optical access network in 5th Embodiment. It is a figure which shows the example of a database in 5th Embodiment.

Embodiments of the present invention will be described in detail with reference to the drawings.
First Embodiment
FIG. 1 is a diagram showing an example of the configuration of the optical access network 1a (optical communication network). The optical access network 1 a includes an optical subscriber line termination device 10, an optical fiber 11, an optical repeater 12 a, an optical fiber 13, and an optical subscriber line network device 14. The optical subscriber line network devices 14 may be plural (N). Hereinafter, a section between the optical subscriber line termination device and the optical repeater is referred to as a "trunk section". Hereinafter, a section between the optical subscriber line termination device and the optical subscriber line network device will be referred to as an "access section". Hereinafter, the wavelength of the upstream optical signal and the wavelength of the downstream optical signal are different.

  The optical subscriber line terminating device 10 (OLT) (master station device) transmits an optical signal to the optical repeater 12 a via the optical fiber 11. The optical subscriber line terminating device 10 acquires an optical signal from the optical repeater 12 a via the optical fiber 11. The optical fiber 11 transmits an optical signal between the optical network unit 10 and the optical repeater 12a. The optical subscriber line termination device 10 is provided at the master station.

  The optical repeater 12a is an optical repeater that relays an optical signal between the optical subscriber line termination unit 10 and the optical subscriber line network unit 14. The optical repeater 12 a acquires an optical signal from the optical subscriber line termination device 10 via the optical fiber 11. The optical repeater 12 a transmits the optical subscriber line termination unit 10 via the optical fiber 11. The optical fiber 13 transmits an optical signal between the optical repeater 12 a and the optical subscriber line network unit 14. The optical repeater 12a is provided at the relay station.

  The optical subscriber line network device 14 (subscriber device) acquires an optical signal from the optical repeater 12 a via the optical fiber 13. The optical subscriber line network device 14 transmits an optical signal to the optical repeater 12 a via the optical fiber 13.

Next, the configuration of the optical repeater 12a will be described.
The optical repeater 12a includes a WDM filter 120, an optical coupler 121, an optical attenuator 122, a downstream amplifier 123, a variable optical attenuator 124, an optical coupler 125, a WDM filter 126, an optical coupler 127, and a photo. A diode 128, a photodiode 129, an optical coupler 130, an optical attenuator 131, an upstream amplifier 132, a variable optical attenuator 133, a photodiode 134, a photodiode 135, and a control unit 136 are provided.

  The WDM filter 120 (Wavelength Division Multiplexing Filter) (wavelength multiplexer / demultiplexer) transmits the downstream optical signal to the optical coupler 121 by wavelength separation. The WDM filter 120 acquires an upstream optical signal from the optical coupler 127. The WDM filter 120 transmits the upstream optical signal to the optical network unit 10 by wavelength separation.

  The optical coupler 121 transmits a part of the downstream optical signal to the optical attenuator 122. The optical coupler 121 transmits a part of the downstream optical signal to the photodiode 129. The optical coupler 121 transmits to the photodiode 129 a downstream optical signal whose intensity is 5 to 10% of the maximum intensity of the downstream optical signal. Thus, the optical coupler 121 can prevent the optical attenuator 122 from excessively attenuating the optical signal amplified by the downstream amplifier 123. Also, the optical coupler 121 can cause the control unit 136 to accurately measure the intensity of the downstream optical signal.

  The optical attenuator 122 (attenuator) acquires a downstream optical signal from the optical coupler 121. The optical attenuator 122 adjusts the intensity of the downstream optical signal by attenuating the intensity of the downstream optical signal according to the control by the control unit 136 so that the optical overinput condition does not occur in the downstream amplifier 123. The optical attenuator 122 transmits the downstream optical signal whose intensity has been adjusted to the downstream amplifier 123.

  The downstream amplifier 123 is an optical amplification device for amplifying a downstream optical signal. The downstream amplifier 123 acquires the downstream optical signal from the optical attenuator 122. The downstream amplifier 123 amplifies the intensity of the downstream optical signal. The downstream amplifier 123 transmits the downstream optical signal whose intensity is amplified to the variable optical attenuator 124. The downstream amplifier 123 is, for example, an optical semiconductor amplifier (SOA: Semiconductor Optical Amplifier) or an optical fiber amplifier.

  The variable optical attenuator 124 (VOA: Variable Optical Attenuator) is an optical attenuator (ALC) for adjusting the intensity of the downstream optical signal to a constant level according to the automatic level control (ALC: Auto Level Control) by the control unit 136. -VOA). The method of automatic level control may be, for example, the method of automatic level control described in Patent Document 1. The variable optical attenuator 124 transmits the downstream optical signal whose intensity is adjusted to the optical coupler 125.

The optical coupler 125 transmits part of the downstream optical signal to the WDM filter 126 . The optical coupler 125 transmits part of the downstream optical signal to the photodiode 135. The optical coupler 125 transmits to the photodiode 135 an optical signal having an intensity of 5 to 10% with respect to the maximum intensity of the optical signal.

  The WDM filter 126 acquires the downstream optical signal from the optical coupler 125. The WDM filter 126 transmits the downstream optical signal to the optical network unit 14 via the optical fiber 13. The WDM filter 126 transmits the upstream optical signal to the optical coupler 130.

  The optical coupler 127 transmits a part of the upstream optical signal acquired from the variable optical attenuator 133 to the WDM filter 120. The optical coupler 127 transmits a part of the upstream optical signal acquired from the variable optical attenuator 133 to the photodiode 128 (photodiode for intensity detection). The optical coupler 127 transmits to the photodiode 128 an upstream optical signal whose intensity is 5 to 10% of the maximum intensity of the upstream optical signal.

  The photodiode 128 (Photodiode) (light intensity detection unit) transmits a signal corresponding to the intensity of the upstream optical signal acquired from the optical coupler 127 to the control unit 136. That is, the photodiode 128 is a signal according to the intensity (post-amplification intensity) of the upstream optical signal after the intensity is adjusted by the variable optical attenuator 133 for the optical signal after the intensity is amplified by the upstream amplifier 132. , To the control unit 136.

  The photodiode 129 (light intensity detection unit) transmits a signal corresponding to the intensity of the downstream light signal acquired from the optical coupler 121 to the control unit 136. That is, for the optical signal before the intensity is amplified by the downstream amplifier 123, the photodiode 129 generates a signal according to the intensity (the intensity before amplification) of the downstream optical signal before the intensity is adjusted by the optical attenuator 122. Transmit to control unit 136.

  The optical coupler 130 acquires the upstream optical signal from the WDM filter 126. The optical coupler 130 transmits a part of the upstream optical signal acquired from the WDM filter 126 to the optical attenuator 131. The optical coupler 130 transmits a part of the upstream optical signal acquired from the WDM filter 126 to the photodiode 134 (photodiode for intensity detection). The optical coupler 130 transmits to the photodiode 134 an upstream optical signal whose intensity is 5 to 10% of the maximum intensity of the upstream optical signal.

  The optical attenuator 131 (attenuator) acquires an upstream optical signal from the optical coupler 130. The optical attenuator 131 adjusts the intensity of the upstream optical signal by attenuating the intensity of the upstream optical signal according to the control by the control unit 136 so that the optical overinput condition does not occur in the upstream amplifier 132. The optical attenuator 131 transmits the upstream optical signal whose intensity has been adjusted to the upstream amplifier 132.

  The upstream amplifier 132 is an optical amplification device for amplifying an upstream optical signal. The upstream amplifier 132 acquires an upstream optical signal from the optical attenuator 131. The upstream amplifier 132 amplifies the intensity of the upstream optical signal. The upstream amplifier 132 transmits the upstream optical signal whose intensity is amplified to the variable optical attenuator 133. The upstream amplifier 132 is, for example, an optical semiconductor amplifier (SOA) or an optical fiber amplifier.

  The variable optical attenuator 133 (VOA) is an optical attenuator (ALC-VOA) for adjusting the intensity of the upstream optical signal to a constant level in accordance with automatic level control (ALC) by the control unit 136. The variable optical attenuator 133 transmits the upstream optical signal whose intensity has been adjusted to the optical coupler 127.

  The photodiode 134 (light intensity detection unit) transmits a signal corresponding to the intensity of the upstream optical signal acquired from the optical coupler 130 to the control unit 136. That is, for the optical signal before the intensity is amplified by the upstream amplifier 132, the photodiode 134 is a signal according to the intensity (the intensity before amplification) of the upstream optical signal before the intensity is adjusted by the optical attenuator 131. Transmit to control unit 136.

  The photodiode 135 (light intensity detection unit) transmits a signal corresponding to the intensity of the downstream light signal acquired from the optical coupler 125 to the control unit 136. That is, for the optical signal whose intensity is amplified by the downstream amplifier 123, the photodiode 135 is a signal according to the intensity (post-amplification intensity) of the downstream optical signal whose intensity is adjusted by the variable optical attenuator 124. , To the control unit 136.

  The control unit 136 is a software function unit that functions when, for example, a processor such as a CPU (Central Processing Unit) executes a program stored in the storage unit. The control unit 136 may also be a hardware functional unit such as a large scale integration (LSI) or an application specific integrated circuit (ASIC).

  The control unit 136 may include a storage unit. The storage unit is configured using a storage device having a non-volatile storage medium (non-temporary storage medium) such as a magnetic hard disk drive or a semiconductor storage device. The storage unit may have, for example, a volatile storage medium such as a random access memory (RAM) or a register.

  For the upstream optical signal, the maximum gain of the upstream optical signal is determined. A saturated output value of the upstream optical signal is determined for the upstream optical signal. For the downstream optical signal, the maximum gain of the downstream optical signal is determined. For the downstream optical signal, the saturated output value of the downstream optical signal is determined.

  The control unit 136 controls the amount of attenuation of the optical signal by the optical attenuator 122 by transmitting an electrical control signal to the optical attenuator 122. The control unit 136 controls the attenuation amount of the optical signal by the optical attenuator 131 by transmitting an electrical control signal to the optical attenuator 131.

  The control unit 136 executes automatic level control of the downstream optical signal by the variable optical attenuator 124 by transmitting an electrical control signal to the variable optical attenuator 124. The control unit 136 executes automatic level control of the upstream optical signal by the variable optical attenuator 133 by transmitting an electrical control signal to the variable optical attenuator 133.

  The control unit 136 controls the gain of each amplifier. Hereinafter, the maximum gain of the optical repeater 12a is, for example, 20 dB. That is, the maximum gain of the down amplifier 123 is 20 dB. The maximum gain of the upstream amplifier 132 is 20 dB. Hereinafter, the saturated output value of the optical repeater 12a is, for example, 5 dBm.

  The control unit 136 acquires, from the photodiode 134, a signal corresponding to the intensity of the upstream optical signal acquired from the optical coupler 130. The control unit 136 acquires from the photodiode 128 a signal corresponding to the intensity of the upstream optical signal acquired from the optical coupler 127. The control unit 136 acquires from the photodiode 129 a signal corresponding to the intensity of the downstream optical signal acquired from the optical coupler 121. The control unit 136 acquires, from the photodiode 135, a signal corresponding to the intensity of the downstream optical signal acquired from the optical coupler 125. The control unit 136 determines the gain of the optical signal in the optical repeater 12a based on the signal acquired from each photodiode.

  When the intensity of the optical signal acquired by the optical repeater 12a is -20 dBm, and the intensity of the optical signal is amplified with a maximum gain of 20 dB, the intensity of the amplified optical signal is 0 dBm. Therefore, the intensity 0 dBm of the amplified optical signal is less than the saturated output value 5 dBm. Therefore, the control unit 136 sets the attenuation amount of the optical signal by the variable optical attenuator 124 to 0 (= 20-20) dB in order to amplify the intensity of the downstream optical signal with the maximum gain of 20 dB. The control unit 136 sets the attenuation amount of the optical signal by the variable optical attenuator 133 to 0 (= 20-20) dB in order to amplify the intensity of the upstream optical signal with a maximum gain of 20 dB.

  When the intensity of the optical signal acquired by the optical repeater 12a is -5 dBm, and the intensity of the optical signal is amplified with a maximum gain of 20 dB, the intensity of the amplified optical signal is 15 dBm. Therefore, the intensity 15 dBm of the amplified optical signal exceeds the saturated output value 5 dBm. Therefore, the control unit 136 sets the attenuation amount of the optical signal by the variable optical attenuator 124 to 10 (= 15−5) dB in order to set the intensity of the downstream optical signal to the saturation output value 5 dBm. The control unit 136 sets the attenuation amount of the optical signal by the variable optical attenuator 133 to 10 (= 15−5) dB in order to set the intensity of the upstream optical signal to the saturation output value 5 dBm. Thus, the control unit 136 can perform stable and quick automatic level control.

  When the control unit 136 can amplify the optical signal without attenuating the intensity of the amplified optical signal, the variable optical attenuator 124 and the variable optical attenuator 133 are used to control the intensity of the optical signal. You may adjust to a fixed level. When the control unit 136 can amplify the optical signal without attenuating the intensity of the amplified optical signal, the control unit 136 changes the drive power supplied to the upstream amplifier 132 and the downstream amplifier 123 to thereby increase the upstream amplifier 132 and the downstream amplifier 123. The gain of the down amplifier 123 may be changed to adjust the intensity of the optical signal to a constant level.

  Next, a control sequence in the case where the upstream amplifier 132 and the downstream amplifier 123 are 1R type optical amplifiers as an example will be described.

  The 1R type optical amplifier performs optical amplification using a device such as an optical semiconductor amplifier (SOA) or an optical fiber amplifier without converting an optical signal into an electric signal or the like. The 1R-type optical amplifier has a complicated control mechanism because the effect of optical amplification (the effect of extending) nonlinearly changes with the intensity of the input optical signal. The upstream amplifier 132 and the downstream amplifier 123 may be 3R type optical amplifiers. The 3R-type optical amplifier converts an optical signal into an electrical signal and converts the converted electrical signal into an optical signal.

Hereinafter, parameters used for control by the control unit 136 will be shown.
(Parameters relating to the optical subscriber line termination device 10)
POLT, min indicates the minimum intensity (minimum output) [dBm] on the standard defined for the optical signal transmitted by the optical subscriber line termination device 10 (master station device).
POLT, max indicates the maximum intensity [dBm] on the standard defined for the optical signal transmitted by the optical line terminal 10.
The SOLT indicates the minimum strength (minimum power allowed) [dBm] on the standard defined for the optical signal acquired by the optical subscriber line termination device 10.
TOLT indicates the maximum intensity (maximum allowable power) [dBm] on the standard defined for the optical signal acquired by the optical subscriber line termination device 10.

(Parameters for Optical Subscriber Line Network Device 14)
The PONU indicates the minimum intensity [dBm] on the standard defined for the optical signal transmitted by the optical subscriber line network device 14.
The SONU indicates the minimum strength (minimum power allowed) [dBm] on the standard defined for the optical signal acquired by the optical subscriber line network device 14.
The TONU indicates the maximum strength (maximum allowable power) [dBm] on the standard defined for the optical signal acquired by the optical subscriber line network device 14.

(Parameters related to the optical repeater 12a)
POA, up, max indicate the saturated output value [dBm] of the upstream amplifier 132.
POA, down, max indicate the downstream saturated output value [dBm] of the downstream amplifier 123.

(Parameters related to the optical attenuator or variable optical attenuator)
ATTup, in indicates the ATT value (set value of attenuation amount of optical signal) [dB] of the optical attenuator 131 on the input side of the upstream amplifier 132.
ATTup and out indicate the ATT value [dB] of the variable optical attenuator 133 on the output side of the upstream amplifier 132.
ATTdown, in indicates the ATT value [dB] of the optical attenuator 122 on the input side of the downstream amplifier 123.
ATTdown, out indicate the ATT value [dB] of the variable optical attenuator 124 on the output side of the downstream amplifier 123.

(Parameter of light signal intensity in each amplifier)
QOA, up indicates the intensity of the upstream optical signal optical repeater 12a is retrieve [dBm]. That is, QOA, up indicates the intensity [dBm] of the optical signal before being attenuated by the optical attenuator 131 .
POA, Stay up-indicates the intensity of the upstream optical signals upstream amplifier 132 to send [dBm]. That is, POA, up indicates the intensity [dBm] of the optical signal before being attenuated by the optical attenuator 133 .
QOA, down indicates the intensity of the downstream optical signal optical repeater 12a is retrieve [dBm]. That is, QOA, down indicates the intensity [dBm] of the optical signal before being attenuated by the optical attenuator 122 .
POA, down indicates the intensity of the downstream optical signals downlink amplifier 123 is sent [dBm]. That is, POA, down indicates the intensity [dBm] of the optical signal before being attenuated by the optical attenuator 124 .

(Parameters related to the optical access network 1a)
Dt indicates the distance [km] of the trunk section.
Da indicates the distance [km] of the access section for the optical subscriber line network apparatus 14 in the vicinity (within a predetermined distance) of the optical repeater 12a.
Losst, up indicates the upstream line loss [dB] of the trunk section.
Losst, down represents the downlink loss [dB] of the trunk section.
Lossa, up indicates the upstream line loss [dB] of the access section related to the optical subscriber line network apparatus 14 in the vicinity of the optical repeater 12a.
Lossa, down indicates the downstream line loss [dB] of the access section related to the optical subscriber line network apparatus 14 in the vicinity of the optical repeater 12a.

(Initial state of control sequence)
In the initial state of the control sequence, the optical subscriber line termination device 10 (master station device) and the optical repeater 12a are connected within the allowable line loss range. The optical repeater 12a and the optical subscriber line network unit 14 are connected within the allowable line loss range. As a result, the optical subscriber line terminating device 10 can accommodate all the optical subscriber line network devices 14 without causing an optical overinput condition by using the optical repeater 12a.

  The optical subscriber line termination device 10 (master station device) is in a continuous light emission state. The optical subscriber line network device 14 is in the off state. Therefore, the optical repeater 12a acquires the downstream optical signal without acquiring the upstream optical signal.

Control unit 136, an optical attenuator 122, Losst shown in equation (1), ATTdown at max (maximum value of the line loss trunk section), to initialize the in. Control unit 136, an optical attenuator 131, lossa shown in equation (2), ATTup at max (maximum value of the line loss of access period), to initialize the in. The control unit 136 initializes ATTdown and out with the variable light attenuator 124 at the maximum value shown in equation (3). The control unit 136 initializes ATTup, out for the variable optical attenuator 133 with the maximum value shown in Expression (4).

ATTdown, in = Losst, max (1)
ATTup, in = Lossa, max (2)
ATTdown, out = Lossa, max (3)
ATTup, out = Losst, max (4)

  For example, even if the optical subscriber line network apparatus 14 in the vicinity of the optical repeater 12a is linked up (communicable) and the optical repeater 12a acquires an upstream optical signal of high intensity, the control unit 136 is an optical attenuator By the attenuation of the upstream optical signal due to 131, it is possible to prevent the occurrence of the optical overinput condition in the upstream amplifier 132.

  In addition, the control unit 136 is in advance based on the accommodation information table of the optical subscriber line network device 14, the optical path database or the construction log whether or not the optical overinput condition may occur in the optical repeater 12a. It may be determined. The control unit 136 may initialize the ATT value with a value smaller than the maximum value, when the possibility that the excessive light input state does not occur in the optical repeater 12a is equal to or more than a threshold.

(Setting sequence of ATT value)
The control unit 136 determines the ATT value by executing setting sequences (i) to (vii) of the ATT value shown below.

(I) Measurement of downstream optical signal strength QOA, down The control unit 136 outputs, from the photodiode 129, a signal corresponding to the downstream optical signal intensity acquired from the optical coupler 121 for the downstream optical signal acquired by the WDM filter 120. get. That is, the control unit 136 obtains, from the photodiode 129, a signal corresponding to the intensity of the downstream optical signal before the intensity is adjusted by the optical attenuator 122.

A control unit 136, the intensity of the downstream optical signal optical repeater 12a has acquired QOA, to measure down.

  When the trunk line loss is a line loss outside the application range of the optical repeater 12a, the photodiode 129 may not be able to detect the downstream optical signal. The photodiode 129 may not be able to detect the downstream optical signal when a fault occurs in the line of the trunk section. The photodiode 129 may not be able to detect the downstream optical signal when any part of the optical repeater 12a is broken. If the downstream optical signal can not be detected, the control unit 136 issues an alarm for warning that the intensity of the downstream optical signal is low to the monitoring network or the like, and executes predetermined abnormal termination processing. It is also good.

・ ATT value (initial value) in setting sequence (i) of ATT value
ATTdown, in = Losst, max
ATTup, in = Lossa, max
ATTdown, out = Lossa, max
ATTup, out = Losst, max

(Ii) Calculation of Downlink Loss Losst, down of Trunk Section Based on the strength QOA, down of the downstream optical signal acquired by the optical repeater 12a, the control unit 136 expresses the downlink loss Losst, down of the trunk section Calculate as 5).

  Losst, down = POLT, min-QOA, down (5)

  The control unit 136 calculates the downstream line loss Losst, down of the trunk section using the statistical data (actual value) on manufacturing regarding the strength of the optical signal transmitted by the optical network unit 10 instead of POLT, min You may The control unit 136 can more optimally determine ATTup and out by using statistical data on manufacturing.

  For example, as shown in 10G-EPON (PR30), when the minimum intensity POLT, min according to the standard is +3 dBm, the control unit 136 temporarily loses 18 dB when the QOA, down is -15 dBm. It may be defined as For example, when the statistical data on manufacture indicates that the 99.999% or more optical subscriber line termination device 10 is POLT, min = + 4 dBm or more, the control unit 136 has a probability of 99.999% or more. Assuming that Losst, down is 19 dB, Losst, down may be set to this value.

  Therefore, when calculating using the minimum intensity POLT, min according to the standard, the control unit 136 sets Losst, down smaller by 1 dB as compared to the case of calculating using statistical data on manufacturing. When the line loss is small, an optical overinput condition easily occurs in the optical amplifier. The control unit 136 sets the ATT value (the set value of the attenuation amount of the optical signal) to a larger value in order to prevent the occurrence of the excessive light input state in the optical amplifier.

  When the control unit 136 determines the ATT value to be a larger value, the control unit 136 can further prevent the occurrence of the light excess input state. A large ATT value may affect the effect of the prolongation if actually only a small amount of light attenuation is required (if no margin is required). A large ATT value has less influence on the effect of prolongation when the statistical data on manufacturing accurately reflects the measured value of the device. A large ATT value may cause an optical over-input condition with low probability if the statistical data on manufacturing accurately reflects the measurement value of the device. The control unit 136 may use either the minimum intensity on the standard or statistical data on manufacturing according to the concept of assurance to prevent the occurrence of the light excessive input state.

  The control unit 136 may calculate the downstream line loss Losst, down of the trunk section based on the statistical data as shown in Formula (6).

  Losst, down = POLT, min-QOA, down + α (6)

  α is a margin term (coefficient) indicating a measurement value of connection loss or fusion loss of the trunk section line. The measurement of splice loss or fusion loss is, for example, a measurement of splice loss or fusion loss. α is a value of 0 or more. α is represented by a function α (Dt) that is directly proportional to the distance. The control unit 136 sets Losst, down to a larger value by adding the coefficient α.

  When α is, for example, 1 dB, the control unit 136 determines Losst, down as 19 (= 18 + 1) dB based on the minimum intensity POLT, min on the standard. In this case, since the ATT value (set value of the attenuation amount of the optical signal) becomes smaller, the effect of the extension is not impaired. The probability of occurrence of an optical overinput condition is higher than when α is 0. That is, the control unit 136 can efficiently execute automatic level control (ALC) by appropriately determining α in accordance with the trade-off between the effect of prolongation and the occurrence probability of the light excessive input state.

(Iii) Estimation of Losst, Up Based on Losst, Down For example, in 10 G-EPON (10 Gbit / s Ethernet Passive Optical Network), the band of the wavelength of the upstream optical signal is the O band. The wavelength band of the downstream optical signal is the L band. In this case, the transmission loss of the upstream optical signal increases by about 0.2 dB per kilometer as compared to the transmission loss of the downstream optical signal. Therefore, when the number of branches and the like in the trunk section are unknown, the relationship between Losst, down and Losst, up is expressed by the approximate expression (7). The control unit 136 calculates Losst, up based on Losst, down as in the approximate expression (7).

  Losst, up = Losst, down + 0.2 Dt (7)

  0.2 shown in the approximate expression (7) is a value based on the difference between the transmission loss of the upstream optical signal and the transmission loss of the downstream optical signal. Dt indicates the distance of the trunk section. That is, Dt indicates the minimum accommodation distance of the aggregation target. Dt is, for example, 1 km.

  For example, when the control unit 136 estimates that Losst, down is 18 dB based on the specified value POLT, min = + 3 dBm and QOA, down, in = -15 dBm of 10 G-EPON, based on the approximation formula (7), It is calculated as Losst, up = 18 + 0.2 × 1 = 18.2 dB.

  As the loss and down are more accurate, the ATT value is optimized, so the effect of prolongation is not impaired. Similarly, since the ATT value is optimized as Losst, up is more accurate, the effect of prolongation is not impaired.

When the control unit 136 acquires the variable Dt indicating the distance from the external database, the control unit 136 may calculate Losst, up using the variable Dt indicating the distance as in the approximate expression (7). When Dt is, for example, 10 km, the control unit 136 sets Losst, up as 20 (= 18 + 0.2 × 10) dB. Similarly, when the number of branches of the trunk section is obtained from the external database, the control unit 136 may add a value obtained by multiplying 10 by the common logarithm value of the number of branches of the trunk section to Losst, down. When the number of branches in the trunk section is four, for example, the control unit 136 adds Lost, up to 24 (= 18 + 6) dB by adding 10 × log ₁₀ (4) (= about 6 dB) to Losst, down. It may be determined.

  When using a wavelength other than the wavelength of the O band or L band, the control unit 136 determines the coefficient shown in the approximate expression (7) according to the measurement value of the wavelength to be used when the transmission loss of the wavelength to be used is known in advance. You may change (0.2).

  The control unit 136 may acquire statistical data of the line loss. For example, when the line loss of the downlink signal is a predetermined value, the control unit 136 sets the coefficient (0.2) shown in the approximate expression (7) based on the result of the maximum likelihood estimation of the value of the most likely uplink loss. You may change it. The control unit 136 may store statistical information in the storage unit of the control unit 136 in advance. The control unit 136 may obtain the latest statistical information from the external database, and store the latest statistical information in the storage unit of the control unit 136.

(Iv) Losst, ATTdown based down, in the calculation of, Losst, based on the u p ATTup, calculation control section 136 of the out is, Losst, based on down, calculates ATTdown, the in the equation (8) . The control unit 136 calculates ATTup, out based on Losst, up as shown in Expression (9).

ATT down, in = Max ((POLT, max-QOA, down + Lost, down), 0) (8)
ATTup, out = Max ((POA, up, max- (TOLT-Losst, up)), 0) (9)

  Here, if ATTdown, in is less than 0 dB, the control unit 136 sets ATTdown, in to 0 dB. When ATTup, out is 0 dB or less, the control unit 136 sets ATTdown, in as 0 dB.

  Since TOLT in 10G-OLT (PR30) is -6 dBm, Losst, up is 18.2 dB. In the case of using an optical amplifier operable at POA, down, max = + 5 dB, the control unit 136 determines ATTup, out as −7.2 (= + 5-(− 6) −18.2) dB. Since ATTup, out is less than 0, the control unit 136 sets ATTup, out as 0. The standard strength TOLT defined for the optical signal acquired by the optical subscriber line termination device 10 may be a prescribed maximum strength (worst spec) or may be a practical value in manufacturing.

-ATT value in setting sequence (iv) of ATT value ATTdown, in = Max ((POLT, max-QOA, down + Lost, down), 0)
ATTup, in = Lossa, max
ATTdown, out = Lossa, max
ATTup, out = Max ((POA, up, max-(TOLT-Lost, up)), 0)

(V) Link-up of the optical subscriber line network device 14 in the vicinity of the optical repeater 12a The optical subscriber line termination device 10 transmits the upstream optical signal (exchange signal) for link up start to the optical subscriber line network device 14 Need to get from. The optical subscriber line network device 14 needs to obtain a downstream optical signal (exchange signal) for link up start from the optical subscriber line termination device 10. Even when the optical subscriber line network device 14 is linked up, in the optical repeater 12a, an optical overinput condition by the upstream optical signal should not occur. The control unit 136 gradually reduces ATTup, in from the initial value shown in equation (1). The control unit 136 gradually reduces ATTdown, out from the initial value shown in equation (3).

  The control unit 136 determines whether the optical subscriber line network device 14 has been linked up based on the signal corresponding to the intensity of the upstream optical signal acquired from the optical coupler 130. The uplink loss Lossa, up of the trunk section is expressed as Expression (10).

  Lossa, up = Lossa, down + 0.2 Da (10)

  The relationship between ATTdown, out and ATTup, in is expressed as equations (11) and (12).

ATTdown, out = Max ((POA, down-SONU-Lossa, down), 0) (11)
ATTup, in = Max ((PONU, max-SOA, up-Lossa, up), 0) (12)

  POA, down is determined based on the optical characteristics of the optical repeater 12a and the known QOA, down. Therefore, equation (13) holds. In practice, the control unit 136 may calculate ATTup, in as in equation (14).

ATTup, in
= PONU-SOA, up-(Lossa, down + 0.2 Da)
= PONU-SOA, up-(POA, down-SONU-ATTdown, out + 0.2 Da)
= ATTdown, out + PONU-SOA, up-(POA, down-SONU)-0.2 Da (13)

ATTup, in
= Max ((ATT down, out + PONU-SOA, up-POA, down-SONU)-0.2 Da), 0) (14)

  Therefore, the control unit 136 may set a value larger than ATTdown, out as the difference between the equation (13) and the equation (14) as ATTup, in. For example, PONU, max is +9 dBm (PR30), SOA, up is -30 dBm, POA, down is +5 dBm (QOA, down is -15 dBm), and SONU is -28.5 dBm (PR30). In some cases, equation (15) holds.

ATTup, in
= ATT down, out + 9-(-30)-(5- (-28.5)) + 0.2 Da, min
= ATTdown, out + 5.5-0.2Da (15)

  The initial value of ATTup, in is 30 dB. The initial value of ATTdown, out is 30 dB. The minimum value Da, min of Da is zero. The minimum value of Da is a value of a variable Da indicating the distance of the access section to be most careful of the light overload state. The control unit 136 updates ATTup, in, which is the initial value, as in equation (16).

  ATTup, in = 30 + 5.5-0.2 x 0 = 35.5 dB (16)

  When no optical subscriber line network apparatus 14 links up even when using ATTup, in shown in the equation (16), the control unit 136 holds ATTdown so that the difference between ATTdown, out and ATTup, in is maintained. , Out and ATTup, in are gradually reduced by the step size ATTStep. The control unit 136 gradually reduces ATTdown, out and ATTup, in with a step size ATTStep while satisfying, for example, equation (17).

  ATTdown, out−ATTup, in = 5.5 dB (17)

  The step size ATTStep is, for example, 0.2 to 1.0 dB. The ATT step allows the control unit 136 to finely determine the ATT value for the optical subscriber line network device 14 to link up.

  For example, if the initial value of ATTdown, out is set to Lossa, max (= 30 dB), ATTdown, out and ATTup, in are reduced by 2 dB per second. That is, the control unit 136 sets (ATTdown, out, ATTup, in) to 1 as (30, 35.5) dB, (28, 33.5) dB, ..., (0, 5.5) dB. Decrease by 2 dB every second.

  For example, when the initial value of (ATTdown, out, ATTup, in) is (30, 20) dB, the control unit 136 calculates (28, 18) dB, ... (0, 4) dB, (0, 2) As in dB and (0, 0) dB, (ATTdown, out, ATTup, in) is reduced by 2 dB every second.

  If the optical network unit 14 does not link up even if ATTdown, out is set to 0 dB, the control unit 136 is a variable indicating the distance of the access section by Dstep, which is a predetermined step width with respect to the distance of the access section. Increase Da. The value of Dstep is, for example, 10 km. The control unit 136 returns ATTdown, out to the initial value (= 30 dB). The control unit 136 determines the ATT value again based on Dstep. For example, when the variable Da indicating the distance of the access section is changed with the step size Dstep (= 10 km), 0.2 Da is 2 dB. The control unit 136 changes (ATTdown, out, ATTup, in) as (30, 33.5) dB, (28, 31.5) dB, and so on.

  The control unit 136 increases the step size Dstep when the optical subscriber line network device 14 does not link up even if the variable Da indicating the distance of the access section is changed with the step size Dstep (= 10 km). For example, the control unit 136 sets the step size Dstep to 20 km. The control unit 136 returns ATTdown, out to the initial value (= 30 dB). The control unit 136 determines the ATT value again based on Dstep (= 20 km).

  For example, when the variable Da indicating the distance of the access section is 30 km and the ATT down, out is 20 dB, when the optical subscriber line network apparatus 14 links up for the first time, the control unit 136 sets ATT up, in (= 19 It is determined that the ATT value of the optical attenuator 131 is .5 dB). The control unit 136 defines ATTdown, out (= 20 dB) as the ATT value of the variable optical attenuator 124.

  The control unit 136 may decrease ATTup, in and ATTdown, out by 0.5 to 10 dB every second. When the optical subscriber line termination device 10 and the optical subscriber line network device 14 can be linked up in a short time, the control unit 136 shortens the time interval for changing ATTup, in and ATTdown, out. It is also good. That is, when the optical subscriber line termination device 10 and the optical subscriber line network device 14 can be linked up in a short time, the control unit 136 sweeps the sweep rates of ATTup, in and ATTdown, out. May be faster.

  When the optical subscriber line termination unit 10 and the optical subscriber line network unit 14 can not link up in a short time, the control unit 136 lengthens the time interval for changing ATTup, in and ATTdown, out. May be That is, when the optical subscriber line termination device 10 and the optical subscriber line network device 14 can not link up in a short time, the control unit 136 reduces the sweep speed of ATTup, in and ATTdown, out. May be

  The control unit 136 sweeps the sweep speed within a range where the time-out alarm based on the fact that the optical subscriber line network device 14 does not link up is not generated from the optical repeater 12 a, the optical subscriber line termination device 10 or the optical subscriber line network device 14. Determined. As a result, the control unit 136 influences the minimum value of ATTdown, out and ATTup, in for link up of the optical subscriber line termination device 10 and the optical subscriber line network device 14 to the exchange signal for link up. It can be determined without giving. The control unit 136 may set an ATT value to which one optical subscriber line network device 14 close to the optical repeater 12a can link up, and an ATT value at which an optical overinput condition does not occur in the optical repeater 12a. it can.

-ATT value in setting sequence of ATT value (vii) ATTdown, in = Max ((POLT, max-QOA, down + Lost, down), 0)
ATTup, in = a value at which at least one optical subscriber line network device 14 can be linked up (a value where an optical overinput condition does not occur in the upstream amplifier 132 when the optical subscriber line network device 14 is linked up)
ATTdown, out = a value at which at least one optical subscriber line network device 14 can be linked up (when the optical subscriber line network device 14 is linked up, an optical overinput condition occurs in the optical subscriber line network device 14 Value that does not occur)
ATTup, out = Max ((POA, up, max-(TOLT-Lost, up)), 0)

(Vi) Calculation of Lossa, up and Lossa, down based on QOA, up The intensity QOA, up of the upstream optical signal acquired by the upstream amplifier 132 from the optical attenuator 131 is that the optical subscriber line network apparatus 14 has been linked up Measured by

  Based on the intensity QOA, up of the upstream optical signal acquired by the upstream amplifier 132 from the optical attenuator 131, the control unit 136 causes the upstream line loss Lossa of the access section related to the optical subscriber line network apparatus 14 in the vicinity of the optical repeater 12a. , Up is calculated. Lossa, up is expressed as equation (18). The control unit 136 calculates the downstream line loss Lossa, down of the access section related to the optical subscriber line network device 14 in the vicinity of the optical repeater 12a based on Lossa, up based on QOA, up. Lossa, down is expressed by equation (19). If QoA, up is not detected by the photodiode 134, the control unit 136 may execute predetermined abnormal end processing.

Lossa, up = PONU-QOA, up + β (18)
Lossa, down = Lossa, up-0.2 Da (19)

  β is a margin term (coefficient) indicating a measurement value of connection loss or fusion loss of the trunk section line. When QOA, up = −25 dBm, PONU = 4 dBm, β = 0, and Da = 30 km, Lossa, up shown in equation (18) is 33 (= 4 − (− 29) +0) dB Become. Lossa, down shown in the equation (19) is 27 (= 33-0.2 x 30) dB.

  (Vii) Adjustment of ATTdown, out and ATTup, in for enabling all the optical subscriber line network devices 14 to be linked up

  The control unit 136 adjusts ATTdown, out and ATTup, in so that all the optical network units 14 can be linked up. The adjusted ATTup, in is expressed as equation (20). The adjusted ATTup, out is expressed as Expression (21).

ATTup, in ← Max ((ATTup , in- (P OA, up-QOA, up), 0) ... (20)
ATTdown, out = Max ((POA, down-TONU-Lossa, down), 0) (21)

If POA, up = −10 dBm and POA, down = + 5 dBm (QOA, down is −15 dBm) and TONU = −9 dBm, then ATTup, in shown in equation (20) is 4.5 ( It becomes 19.5-(-10-(-25))) dB. The ATTdown, out shown in the equation (21) is -13 (= 5-(-9) -27) dB. When ATTdown, out is less than 0, the control unit 136 sets ATTdown, out as 0.

  When ATTdown, out is 20 dB and ATTup, in is 19.5 dB, the optical subscriber line network devices 14 in the vicinity of the optical repeater 12a can be linked up. When ATTdown, out is 4.5 dB and ATTup, in is 0 dB, an optical over-input state does not occur in the optical subscriber line network device 14 closest to the optical repeater 12a. The optical subscriber line termination unit 10 accommodates a further optical subscriber line network unit 14 when the ATTup, in is 19.5 dB, since the line loss is smaller compared to the case where the ATTup, in is 0 dB. can do.

  Therefore, when the optical subscriber line network device 14 is connected to the optical repeater 12a within the allowable loss range, the control unit 136 does not cause an optical overinput condition in any optical subscriber line network device 14. Can link up all the optical subscriber line network devices 14.

-ATT value in setting sequence of ATT value (vii) ATTdown, in = Max ((POLT, max-QOA, down + Lost, down), 0)
ATTup, in ← Max ((ATTup , in- (P OA, up-QOA, up), 0)
ATTdown, out = Max ((POA, down-TONU-Lossa, down), 0)
ATTup, out = Max ((POA, up, max-(TOLT-Lost, up)), 0)

  FIG. 2 is a flowchart showing an example of the operation (setting sequence of ATT values) of the optical access network 1a. The control unit 136 links up one optical subscriber line network device 14 from step S107 to step S110.

  The control unit 136 initializes the ATT value (ATTdown, in = Losst, max, ATTup, in = Lossa, max, ATTdown, out = Lossa, max, ATTup, out = Losst, max) (step S101).

  The control unit 136 measures the intensities QOA and down of the downstream optical signal acquired by the optical repeater 12a (step S102).

  The control unit 136 calculates the downstream line loss Losst, down of the trunk section based on the intensity QOA, down of the downstream optical signal acquired by the optical repeater 12a (Losst, down = POLT, min-QOA, down) ( Step S103).

  The control unit 136 calculates the uplink loss Losst, up in the trunk section based on the downlink loss Losst, down in the trunk section (Losst, up = Losst, down + 0.2 Dt) (step S104).

  The control unit 136 updates the ATT value (ATTdown, in) of the optical attenuator 122 on the input side of the downstream amplifier 123 based on the downstream line loss Losst, down of the trunk section (ATTdown, in = Max ((POLT, max-QOA, down + Los st, down), 0)).

  The control unit 136 updates the ATT value (ATTup, out) of the variable optical attenuator 133 on the output side of the upstream amplifier 132 based on the upstream line loss Losst, up of the trunk section (ATTup, out = Max ((POA , Up, max- (TOLT-Losst, up), 0)) (step S105).

  The control unit 136 sets a variable Da indicating the distance of the access section related to the optical subscriber line network apparatus 14 in the vicinity (within a predetermined distance) of the optical repeater 12a to 0 (step S106).

  The control unit 136 calculates the ATT value (ATTup, in) of the optical attenuator 131 on the input side of the upstream amplifier 132 (ATTup, in = Max ((ATTdown, out + PONU-SOA, up− (POA, down-SONU) −0.2 Da), 0)) (step S107).

  The control unit 136 increments the ATT value (ATTdown, out) of the variable optical attenuator 124 on the output side of the downstream amplifier 123 and the ATT value (ATTup, in) of the optical attenuator 122 on the input side of the downstream amplifier 123. It is gradually reduced by the width ATTStep (ATTdown, out ← ATTdown, out-ATTStep, ATTup, ininATTup, in-ATTStep) (step S108).

  The control unit 136 determines whether ATTdown, out is less than 0 dB. That is, when ATTdown, out is set to 0 dB or more, the control unit 136 determines whether the optical network unit 14 does not link up or links up (step S109).

  If the updated ATTdown, out is less than 0 dB (step S109: YES), the control unit 136 sets the variable Da indicating the distance of the access section by Dstep, which is a step width predetermined for the distance of the access section. (Step S110). The control unit 136 returns the process to step S107.

  If the updated ATTdown, out is 0 dB or more (step S109: NO), the control unit 136 determines whether one optical subscriber line network device 14 is linked up (step S111). When the optical subscriber line network device 14 is not linked up (step S111: NO), the control unit 136 returns the process to step S108.

  Based on the intensity QOA, up of the upstream optical signal acquired by the upstream amplifier 132 from the optical attenuator 131, the control unit 136 causes the upstream line loss Lossa of the access section related to the optical subscriber line network apparatus 14 in the vicinity of the optical repeater 12a. , Up is calculated (Lossa, up = PONU-QOA, up + β).

  The control unit 136 calculates the downstream line loss Lossa, down of the access section related to the optical subscriber line network apparatus 14 in the vicinity of the optical repeater 12a based on Lossa, up based on QOA, up (Lossa, down = Lossa , Up-0.2 Da) (step S112).

Controller 136, so that all optical subscriber line network unit 14 is made possible link-up, ATTdown, out and ATTup, adjusting in (ATTup, in ← Max ( (ATTup, in- (P OA, up -QOA, up), 0), ATTdown, out = Max ((POA, down-TONU-Lossa, down), 0)) (step S113).

  As described above, the optical repeater 12a according to the first embodiment includes the photodiode 129, the photodiode 134, the downstream amplifier 123, the upstream amplifier 132, the photodiode 135, the photodiode 128, the control unit 136, and the like. Equipped with The photodiode 129 (pre-amplification intensity detection unit) detects the intensity of the downstream optical signal (the intensity before amplification of the downstream optical signal) before the downstream amplifier 123 amplifies the intensity. The photodiode 134 (pre-amplification intensity detection unit) detects the intensity of the upstream optical signal (the intensity before amplification of the upstream optical signal) before the intensity is amplified by the upstream amplifier 132. The downstream amplifier 123 amplifies the intensity of the downstream optical signal. The upstream amplifier 132 amplifies the intensity of the upstream optical signal. The photodiode 135 (post-amplification intensity detection unit) detects the intensity of the downstream optical signal (a post-amplification intensity of the downstream optical signal) after the intensity is amplified. The photodiode 128 (after-amplification intensity detection unit) detects the intensity of the upstream optical signal (the intensity after amplification of the upstream optical signal) after the intensity is amplified. The control unit 136 adjusts the attenuation amount of the downstream optical signal in at least one of the front stage and the rear stage that amplifies the intensity of the downstream optical signal based on the pre-amplification intensity and the post-amplification intensity of the downstream optical signal. The control unit 136 adjusts the attenuation amount of the upstream optical signal in at least one of the front stage and the rear stage that amplifies the intensity of the upstream optical signal based on the pre-amplification intensity and the post-amplification intensity of the upstream optical signal.

  As a result, the optical relay device 12a according to the first embodiment can extend the optical access network 1a even when the occurrence of the excessive optical input state in the optical relay device 12a is prevented.

  That is, since the optical repeater 12a of the first embodiment calculates the attenuation amount of the optical signal acquired by the optical amplifier (optical amplification element) based on the upstream optical signal and the downstream optical signal, the optical repeater 12a in the optical repeater 12a It is possible to prevent the occurrence of the input state and extend the optical access network 1a. The optical repeater 12a according to the first embodiment calculates the attenuation amount of the optical signal transmitted by the optical amplifier (optical amplification element) based on the upstream optical signal and the downstream optical signal. Can be prevented, and the optical access network 1a can be extended. The optical repeater 12a according to the first embodiment can prevent the occurrence of the excessive light input state autonomously by omitting the insertion work and the like.

  The optical repeater 12a of the first embodiment is an optical signal by both feedforward control based on the intensity of the optical signal acquired by the optical repeater 12a and feedback control based on the intensity of the optical signal transmitted by the optical repeater 12a. Control the strength of the The optical repeater 12a according to the first embodiment can stably control the intensity of the optical signal.

  The optical repeater 12a of the first embodiment can reduce the facility cost of the optical access network 1a. As shown in the problem of complicated operation, the control unit 136 of the first embodiment can reduce, for example, a total of 2.5 billion yen. The optical repeater 12a according to the first embodiment can autonomously set the attenuation amount of the optical signal when there is a possibility that an optical overinput condition may occur in the optical repeater 12a.

Second Embodiment
The second embodiment is different from the first embodiment in that the control unit 136 executes automatic level control only for the variable optical attenuator 133 that transmits an upstream optical signal. In the second embodiment, only differences from the first embodiment will be described.

  FIG. 3 is a diagram showing an example of the configuration of the optical access network 1b. The optical access network 1 b includes an optical subscriber line termination device 10, an optical fiber 11, an optical repeater 12 b, an optical fiber 13, and an optical subscriber line network device 14. The optical subscriber line network devices 14 may be plural (N).

Next, the configuration of the optical repeater 12b will be described.
The optical repeater 12 b includes a WDM filter 120, an optical coupler 121, an optical attenuator 122, a downstream amplifier 123, an optical coupler 125, a WDM filter 126, an optical coupler 127, a photodiode 128, and a photodiode 129. , An optical attenuator 131, an upstream amplifier 132, a variable optical attenuator 133, a photodiode 134, a photodiode 135, a control unit 136, and an optical attenuator 137. That is, the optical repeater 12b includes an optical attenuator 137 instead of the variable optical attenuator 124, as compared to the optical repeater 12a of the first embodiment.

  The control unit 136 updates the ATT value (ATTup, in) of the optical attenuator 131 as in equation (20). The control unit 136 determines the ATT value (ATTdown, out) of the optical attenuator 137 as shown in equation (21) based on Lossa, down.

  When the optical network unit 14 is linked up in the setting sequence (v), the control unit 136 starts automatic level control for determining the ATT value (ATTup, out) of the variable optical attenuator 133. The control unit 136 basically performs automatic level control by a combination of feedforward control and feedback control.

  As described above, the control unit 136 of the second embodiment performs automatic level control for changing the intensity of the optical signal with respect to the variable optical attenuator 133 that transmits (outputs) the optical signal to the master station apparatus. Execute (ALC). Thus, the optical repeater 12b according to the second embodiment can improve the signal quality and extend the optical access network 1b even when the occurrence of the excessive optical input state in the optical repeater 12b is prevented. Become.

Third Embodiment
The third embodiment is different from the first embodiment in that the optical repeater includes a drive circuit of an optical amplifier. In the third embodiment, only differences from the first embodiment will be described.

  FIG. 4 is a diagram showing an example of the configuration of the optical access network 1c. The optical access network 1 c includes an optical subscriber line termination device 10, an optical fiber 11, an optical repeater 12 c, an optical fiber 13, and an optical subscriber line network device 14. The optical subscriber line network devices 14 may be plural (N).

Next, the configuration of the optical repeater 12c will be described.
The optical repeater 12 c includes a WDM filter 120, an optical coupler 121, an optical attenuator 122, a downstream amplifier 123, an optical coupler 125, a WDM filter 126, an optical coupler 127, a photodiode 128, and a photodiode 129. , An optical attenuator 131, an upstream amplifier 132, a photodiode 134, a photodiode 135, a control unit 136, a drive circuit 138, and a drive circuit 139.

  That is, as compared with the optical repeater 12a of the first embodiment, the optical repeater 12c includes a drive circuit 138 instead of the variable optical attenuator 124. The optical repeater 12c includes a drive circuit 139 instead of the variable optical attenuator 133, as compared with the optical repeater 12a of the first embodiment.

  The drive circuit 138 drives the down amplifier 123 according to the control by the control unit 136. The drive circuit 139 drives the upstream amplifier 132 according to the control by the control unit 136. The control unit 136 controls the amplification amount of the intensity of the downstream optical signal by the downstream amplifier 123 by changing the physical amount (drive amount) for driving the downstream amplifier 123. The control unit 136 controls the amplification amount of the intensity of the upstream optical signal by the upstream amplifier 132 by changing the physical amount for driving the upstream amplifier 132.

  The physical quantity for driving the optical amplification device is, for example, a current amount of a drive injection current when the downstream amplifier 123 and the upstream amplifier 132 are optical semiconductor amplification elements (SOA). The physical quantity for driving the optical amplification device is, for example, the intensity of the pump light when the downstream amplifier 123 and the upstream amplifier 132 are optical fiber amplifiers.

  As described above, the control unit 136 of the third embodiment controls the amplification amount of the intensity of the optical signal by the optical amplifier. As a result, the optical repeater 12c of the third embodiment can increase the response speed of control and extend the optical access network 1c even when the occurrence of the excessive optical input state in the optical repeater 12c is prevented. It becomes possible.

Fourth Embodiment
The fourth embodiment is different from the first embodiment in that the optical relay device is provided in the master station. In the fourth embodiment, only differences from the first embodiment will be described.

  FIG. 5 is a diagram showing an example of the configuration of the optical access network 1d. The optical access network 1 d includes an optical subscriber line termination device 10, an optical fiber 11, an optical repeater 12 d, an optical fiber 13, and an optical subscriber line network device 14. The optical subscriber line network devices 14 may be plural (N).

  The optical repeater 12d is provided to the master station 2 instead of being provided to the relay station. The master station 2 is, for example, a communication building. When the distance from the master station 2 to the optical subscriber line network device 14 is relatively long, the optical repeater 12 d is required for communication, so the optical repeater 12 d is provided in the master station 2. The optical repeater 12 d may be provided in the optical subscriber line termination device 10.

Next, the configuration of the optical repeater 12d will be described.
The optical repeater 12d includes a WDM filter 120, an optical coupler 121, a downstream amplifier 123, a variable optical attenuator 124, an optical coupler 125, a WDM filter 126, an optical coupler 127, a photodiode 128, and a photodiode. 129, an optical coupler 130, an optical attenuator 131, an upstream amplifier 132, a photodiode 134, a photodiode 135, a control unit 136, and an optical attenuator 137. That is, the optical repeater 12 d does not include the optical attenuator 122 and the variable optical attenuator 133 as compared to the optical repeater 12 a of the first embodiment.

  When the distance from the master station 2 to the optical subscriber line network device 14 is relatively long, the upstream optical signal does not need to be attenuated since an optical overinput condition due to the upstream optical signal does not occur. When the distance from the master station 2 to the optical subscriber line network device 14 is relatively long, there is no need to attenuate the downstream optical signal since the optical overinput condition due to the downstream optical signal does not occur. The optical repeater 12 d may not include the optical attenuator 122 and the variable optical attenuator 133. The control unit 136 may not define ATTdown, in and ATTup, out.

  As described above, the optical repeater 12d of the fourth embodiment is provided in the master station 2 including the optical subscriber line termination device 10 (master station device). Thus, the optical repeater 12d according to the fourth embodiment can extend the optical access network 1a at low cost due to simplification of the apparatus even when the occurrence of the excessive optical input state in the optical repeater 12d is prevented. It becomes possible.

Fifth Embodiment
The fifth embodiment is different from the first embodiment in that the optical repeater calculates the range of parameters for which an optical subscriber network can be newly connected to the optical access network. In the fifth embodiment, only differences from the first embodiment will be described.

  FIG. 6 is a diagram showing an example of the configuration of the optical access network 1 e. The optical access network 1 e includes an optical subscriber line termination device 10, an optical fiber 11, an optical repeater 12 e, an optical fiber 13, an optical subscriber line network device 14, and a storage device 15. The optical subscriber line termination device 10 is provided in the master station 2. The optical repeater 12 e is provided in the relay station 3. A plurality of (M units) optical repeaters 12e may be used. The optical subscriber line network devices 14 may be plural (N). The optical access network 1 e may further include an information processing device 16.

  The control unit 136 performs the optical access network 1e on the basis of the upstream line loss Losst, up and the downstream line loss Losst, down of the trunk section and the upstream line loss Lossa, up and the downstream line loss Lossa, down of the access section. A value representing a condition capable of accommodating the subscriber line network device 14 (hereinafter, referred to as “accommodable range”) may be calculated. The value representing the accommodation range is, for example, a value representing the condition of a variable (parameter) indicating a variable Dt indicating the distance of the trunk section, or a value representing a condition of a variable (parameter) indicating a variable Da indicating the distance of the access section. is there.

  The storage device 15 is configured using a storage device having a non-volatile storage medium (non-temporary recording medium) such as a magnetic hard disk drive or a semiconductor storage device. The storage device 15 may have, for example, a volatile storage medium such as a RAM or a register. The storage device 15 stores a database 150. The database 150 is a database of coverage.

  7 shows an example of the database 150. As shown in FIG. In the database 150, parent station identification information, relay station identification information, variable Dt indicating the distance of the trunk section, variable Da indicating the distance of the access section, and identification information of the optical subscriber line network apparatus 14 are associated. It is done. The parent station identification information is identification information of the parent station 2. The database 150 may include identification information of the optical subscriber line termination device 10 instead of the master station identification information. The database 150 may include identification information of the optical repeater 12 instead of relay station identification information.

  In FIG. 7, the variable Dt indicating the distance of the trunk section represents an accommodable range regarding the distance of the trunk section of the optical subscriber line network device 14. In FIG. 7, the variable Da indicating the distance of the access section represents an accommodable range regarding the distance of the access section of the optical subscriber line network device 14. In FIG. 7, when the distance of the trunk section is 10 to 30 km and the distance of the access section is 10 to 15 km, the optical subscriber line network apparatus 14 newly adds the optical subscriber line network apparatus 14 to the optical access network 1 e. It is possible to connect.

  The information processing device 16 illustrated in FIG. 6 is an information processing device such as a personal computer device, a tablet terminal, and a smartphone terminal. The information processing apparatus 16 includes an operation unit, a communication unit, a display unit, and an operation unit.

  The operation unit of the information processing apparatus 16 is operated by the operator. The operation unit of the information processing device 16 transmits a signal corresponding to the operation to the calculation unit of the information processing device 16. The communication unit of the information processing device 16 acquires the database 150 from the storage device 15. The communication unit of the information processing apparatus 16 may transmit the calculation result by the calculation unit of the information processing apparatus 16 to the optical network unit 14. The display unit of the information processing device 16 displays the calculation result by the calculation unit. For example, the display unit of the information processing device 16 displays information according to the database 150. That is, the display unit of the information processing device 16 displays the information indicating the storable range. The information representing the accommodable range is, for example, parameter information such as a variable.

  The calculation unit of the information processing device 16 is a processor such as a CPU. The computing unit of the information processing apparatus 16 may include an operating system. The operation unit of the information processing apparatus 16 determines whether to permit the optical access network 1 e to newly connect the optical subscriber line network apparatus 14 based on the information contained in the database 150. The operator may determine whether to permit the optical access network 1 e to newly connect the optical subscriber line network device 14 or not.

  When the parameter associated with the optical subscriber line network device 14 that is desired to be newly connected to the optical access network 1 e is within the accommodation range, the arithmetic unit of the information processing device 16 transmits the optical subscriber line network to the optical access network 1 e. Allow device 14 to make a new connection. When permitting the optical access network 1 e to newly connect the optical subscriber line network device 14, the operation unit of the information processing device 16 may transmit a command for new construction to a predetermined device.

  If the parameter associated with the optical subscriber line network device 14 that is desired to be newly connected to the optical access network 1 e is out of the storable range, the arithmetic unit of the information processing device 16 is the other optical fiber 13 in the optical access network 1 e. To permit a new connection of the optical subscriber line network device 14. If the parameter associated with the optical subscriber line network apparatus 14 that is desired to be newly connected to the optical access network 1 e is out of the storable range, the computing unit of the information processing apparatus 16 may use another optical fiber 13 for the optical access network 1 e. You may allow new construction.

  The control unit 136 of the optical relay apparatus 12e may execute the same arithmetic processing as the arithmetic unit of the information processing apparatus 16. For example, the control unit 136 may determine whether to permit the optical access network 1 e to newly connect the optical subscriber line network device 14 based on the information included in the database 150. For example, when the parameter associated with the optical subscriber line network apparatus 14 that is desired to be newly connected to the optical access network 1 e is out of the accommodation range, the control unit 136 outputs light to the other optical fiber 13 in the optical access network 1 e. A new connection of the subscriber line network device 14 may be permitted. The display unit of the information processing device 16 may display the calculation result by the control unit 136.

  As described above, the control unit 136 according to the fifth embodiment is configured to transmit light based on at least part of upstream line loss and downstream line loss between the optical subscriber line termination device 10 and the optical subscriber line network device 14. A value representing a condition under which the optical subscriber line network apparatus 14 can be connected to the access network 1e is calculated. As a result, the optical relay device 12 e according to the fifth embodiment can provide the information indicating the storable range to the operator via the information processing device 16.

  The optical subscriber line termination device, the optical subscriber line network device, and at least a part of the optical repeaters in the embodiments described above may be realized by a computer. In that case, a program for realizing this function may be recorded in a computer readable recording medium, and the program recorded in the recording medium may be read and executed by a computer system. Here, the “computer system” includes an OS and hardware such as peripheral devices. The term "computer-readable recording medium" refers to a storage medium such as a flexible disk, a magneto-optical disk, a ROM, a portable medium such as a ROM or a CD-ROM, or a hard disk built in a computer system. Furthermore, “computer-readable recording medium” dynamically holds a program for a short time, like a communication line in the case of transmitting a program via a network such as the Internet or a communication line such as a telephone line. It may also include one that holds a program for a certain period of time, such as volatile memory in a computer system that becomes a server or a client in that case. Further, the program may be for realizing a part of the functions described above, or may be realized in combination with the program already recorded in the computer system. It may be realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design and the like within the scope of the present invention.

  The present invention is applicable to an optical repeater of an optical access network.

1a to 1d: optical access network 2: master station 3: relay station 10: optical subscriber line termination device 11: optical fiber 12: optical repeater device 13: optical fiber 14: optical subscriber line network Device 15 storage device 16 information processing device 120 WDM filter 121 optical coupler 122 optical attenuator 123 downstream amplifier 124 variable optical attenuator 125 optical coupler 126 WDM filter , 127: optical coupler, 128: photodiode, 129: photodiode, 130: optical coupler, 131: optical attenuator, 132: upstream amplifier, 133: variable optical attenuator, 134: photodiode, 135: photodiode, 136 ... Control unit, 137 ... Optical attenuator, 138 ... Drive circuit, 139 ... Drive circuit, 150 ... Database

Claims (7)

An optical relay apparatus for relaying an optical signal between a master station apparatus and a subscriber apparatus, comprising:
A pre-amplification intensity detection unit that detects the pre-amplification intensity that is the intensity of the light signal before the intensity is amplified;
An optical amplifier for amplifying the intensity of the optical signal;
An amplified intensity detection unit that detects an amplified intensity that is an intensity of the light signal after the intensity is amplified;
A controller configured to adjust an attenuation amount of the optical signal in at least one of a front stage and a rear stage that amplifies the intensity of the optical signal based on the pre-amplification intensity and the post-amplification intensity ;
The control unit does not enter an optical excess input state in the subscriber unit and the optical repeater after adjusting the attenuation amount of the optical signal to link up the subscriber unit in the vicinity of the optical repeater. An optical repeater , which adjusts the attenuation amount of the optical signal .   The optical repeater according to claim 1, wherein the control unit executes automatic level control for a variable optical attenuator that transmits the optical signal toward the master station device.   The optical relay device according to claim 1, wherein the control unit controls an amplification amount of the intensity of the optical signal by the optical amplifier.   The optical relay device according to any one of claims 1 to 3, wherein the optical relay device is provided in a parent station provided with the parent station device.   The control unit calculates a value representing a condition under which the subscriber device can be connected to the optical access network based on at least a part of the line loss between the master station device and the subscriber device. The optical repeater according to any one of claims 1 to 4, wherein The control unit changes the time interval for changing the set value of the attenuation amount of the optical signal according to whether or not the master station apparatus and the subscriber apparatus can link up in a short time. The optical repeater according to any one of claims 1 to 5, wherein An optical relay method performed by an optical relay apparatus for relaying an optical signal between a master station apparatus and a subscriber apparatus, comprising:
Detecting an unamplified intensity, which is the intensity of the light signal before the intensity is amplified;
Amplifying the intensity of the light signal;
Detecting the amplified intensity, which is the intensity of the light signal after the intensity has been amplified;
Look including the step of adjusting, based on the pre-amplification intensity and the amplification strength after attenuation of the optical signal in at least one upstream and downstream of the amplifying the intensity of the optical signal,
In the adjusting step, the attenuation amount of the optical signal is adjusted to link up the subscriber unit in the vicinity of the optical repeater, and then an optical overinput condition is generated in the subscriber unit and the optical repeater. An optical relay method for adjusting the attenuation of the optical signal so as not to

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