JP6280457B2 - Optical signal repeater and communication control method - Google Patents

Description

  The present invention relates to an optical signal relay device and a communication control method, and more particularly to an optical signal relay device and a communication control method using an optical amplifier.

  In recent years, the Internet has become widespread, and users can access various information on sites operated in various parts of the world and obtain the information. Accordingly, devices capable of broadband access such as ADSL (Asymmetric Digital Subscriber Line) and FTTH (Fiber To The Home) are rapidly spreading.

  In IEEE Std 802.3ah (registered trademark) -2004 (Non-patent Document 1), a plurality of ONUs (ONU: Optical Network Unit) share an optical communication line and communicate with a station side device (OLT: Optical Line Terminal). One method of a passive optical network (PON), which is a medium sharing communication for performing data transmission, is disclosed. That is, EPON (Ethernet (registered trademark) PON) in which all information is communicated in the form of an Ethernet (registered trademark) frame, including user information passing through the PON and control information for managing and operating the PON, and EPON An access control protocol (MPCP (Multi-Point Control Protocol)) and an OAM (Operations Administration and Maintenance) protocol are defined. By exchanging MPCP frames between the station-side apparatus and the ONU, ONU joining / leaving, uplink access multiplexing control, and the like are performed. Non-Patent Document 1 describes a method for registering a new ONU, a report indicating a bandwidth allocation request, and a gate indicating a transmission instruction using an MPCP message.

  As a next-generation technology of GE-PON, which is an EPON that realizes a communication speed of 1 gigabit / second, 10G-EPON standardized as IEEE 802.3av (registered trademark) -2009, that is, a communication speed of 10 gigabit / second. Even in EPON equivalent to seconds, the access control protocol is predicated on MPCP.

  As an example of an optical amplifier used in an optical communication system, for example, Japanese Patent No. 497559 (Patent Document 1) discloses the following configuration. That is, an optical amplifier that amplifies an optical signal includes an optical amplification unit that excites an amplification medium doped with an active substance for optical amplification to perform optical amplification, and a semiconductor optical amplifier that is installed after the optical amplification unit, An input light level adjusting unit that adjusts an input light level of the semiconductor optical amplifier, and a driving unit that supplies a driving current to the semiconductor optical amplifier. The input optical level adjusting unit has an operating point of the semiconductor optical amplifier near a boundary between a non-saturated region and a saturated region of gain with respect to the amplification characteristic of the semiconductor optical amplifier amplified by the supplied driving current. The input light level is set so as to be positioned. The semiconductor optical amplifier is operated at the operating point with the input light level set, and when an optical surge generated in the optical amplification unit is input, a gain saturation state in which the output light level is not increased above a certain level. Thus, the optical surge is suppressed.

  Also, in an optical communication system, when the distance between the station side device and the optical line terminator becomes long, an optical signal repeater may be installed to maintain the optical signal transmission characteristics. As an example of such an optical signal relay device, for example, Japanese Patent No. 4919067 (Patent Document 2) discloses the following configuration. That is, an optical burst signal repeater that relays an optical burst signal, an optical / electrical converter that converts an upstream optical burst signal into an electrical relay signal, and a relay signal converted by the optical / electrical converter In order to identify the upstream signal recovery unit to be reproduced and this optical burst signal repeater as one optical line termination device, the communication / switch control unit for creating a frame compliant with the PON protocol, the error information is monitored, and the error is monitored. If information is generated, an error information monitoring unit that outputs an error information pattern to the communication / switching control unit, and installed between the optical / electrical converter and the upstream signal reproducing unit, the communication / switching control unit In accordance with the control, the monitoring information signal obtained from the communication / switch control unit and the relay signal obtained from the optical / electrical converter are switched and supplied to the upstream signal regeneration unit. And a first switching unit of the order. The communication / switch control unit creates a monitoring information signal including an error information pattern acquired from the error information monitoring unit, and supplies the monitoring information signal to an empty slot of an optical burst section.

IEEE Std 802.3ah (registered trademark) -2004

Japanese Patent No. 497559 Japanese Patent No. 4919067

  As an example of processing in the optical signal repeater, a configuration in which an optical signal received from an optical transmitter is amplified using an optical amplifier without being converted into an electrical signal and transmitted to the optical receiver can be considered.

  Here, the distance from the optical transmitter to the optical signal repeater and the distance from the optical signal repeater to the optical receiver differ depending on the installation location of the optical communication system. For this reason, the optical signal repeater receives optical signals of various strengths.

  When the intensity of the optical signal received by the optical signal repeater is large, the output of the optical amplifier is saturated and the transmission quality of the optical signal is reduced, and the optical communication system, specifically, from the optical signal repeater to the optical receiver The communication limit distance becomes smaller.

  For example, when the optical amplifier described in Patent Document 1 is applied to an optical signal repeater, control is performed to reduce the intensity of input light to the optical amplifier in order to avoid saturation of the optical amplifier. In this case, in order to obtain a desired communication limit distance, it is necessary to increase the gain by increasing the drive current supplied to the optical amplifier and increase the intensity of the output light of the optical amplifier, resulting in an increase in power consumption.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to extend the communication limit distance of an optical communication system and to reduce power consumption in an optical signal repeater that amplifies and transmits a received optical signal. It is an object to provide an optical signal relay device and a communication control method capable of suppressing the above.

  In order to solve the above problems, an optical signal repeater according to an aspect of the present invention receives and amplifies an optical signal having a level corresponding to a logical value of data to be transmitted, and transmits the amplified optical signal. An optical signal relay device that receives and amplifies and outputs the optical signal, a measurement unit that performs measurement on the optical signal, and outputs from the optical amplifier based on a measurement result of the measurement unit And a control unit that performs drive control to adjust the magnitude of the drive current or drive voltage supplied to the optical amplifier so that the modulation amplitude of the optical signal to be a predetermined value.

  An optical signal repeater according to another aspect of the present invention is an optical signal repeater that receives and amplifies an optical signal having a level corresponding to a logical value of data to be transmitted, and transmits the amplified optical signal. An optical amplifier that receives and amplifies and outputs the optical signal; a measurement unit that performs measurement on the optical signal; and a modulation amplitude of the optical signal in the optical amplifier based on a measurement result of the measurement unit. And a control unit that performs drive control to adjust the magnitude of the drive current or drive voltage supplied to the optical amplifier so that the gain becomes a predetermined value.

  An optical signal repeater according to another aspect of the present invention is an optical signal repeater that receives and amplifies an optical signal having a level corresponding to a logical value of data to be transmitted, and transmits the amplified optical signal. An optical amplifier that receives, amplifies, and outputs the optical signal, and a measurement unit that performs measurement on the optical signal, and the measurement unit obtains an extinction ratio of the optical signal received by the optical amplifier. The optical signal repeater further includes a control unit that performs drive control to adjust the magnitude of the drive current or drive voltage supplied to the optical amplifier based on the extinction ratio acquired by the measurement unit. .

  In order to solve the above problems, a communication control method according to an aspect of the present invention receives and amplifies an optical signal having a level corresponding to a logical value of data to be transmitted, and transmits the amplified optical signal. A communication control method for controlling an optical signal repeater, wherein the optical signal repeater includes an optical amplifier that receives, amplifies and outputs the optical signal, and the communication control method performs a measurement on the optical signal. And the gain of the modulation amplitude of the optical signal in the optical amplifier becomes a predetermined value so that the modulation amplitude of the optical signal output from the optical amplifier becomes a predetermined value based on the step and the result of the measurement Or, based on the extinction ratio of the optical signal received by the optical amplifier obtained by the measurement, drive control is performed to adjust the magnitude of the drive current or drive voltage supplied to the optical amplifier. And a step.

  The present invention can be realized not only as an optical signal relay apparatus including such a characteristic processing unit, but also as a program for causing a computer to execute such characteristic processing steps. In addition, the present invention can be realized as a semiconductor integrated circuit that realizes part or all of the optical signal repeater, or can be realized as a system including the optical signal repeater.

  ADVANTAGE OF THE INVENTION According to this invention, in the optical signal relay apparatus which amplifies and transmits the received optical signal, while extending the communication limit distance of an optical communication system, power consumption can be suppressed.

FIG. 1 is a diagram showing a configuration of an optical communication system according to the first embodiment of the present invention. FIG. 2 is a diagram showing a configuration of the optical signal repeater according to the first embodiment of the present invention. FIG. 3 is a diagram illustrating an example of the relationship between the intensity and gain of input light in the optical amplifier. FIG. 4 is a diagram illustrating an example of an eye pattern of an optical signal output from an optical amplifier in a non-saturated region. FIG. 5 is a diagram illustrating an example of an eye pattern of an optical signal output from the optical amplifier in the saturation region. FIG. 6 is a diagram illustrating an example of a difference in eye pattern depending on the presence or absence of ASE. FIG. 7 is a diagram illustrating a configuration of a downlink signal relay unit in the optical signal relay device according to the first embodiment of the present invention. FIG. 8 is a diagram illustrating an example of the relationship between the reception level and the reception sensitivity in the optical receiver. FIG. 9 is a diagram illustrating an example of the relationship between the modulation amplitude and the reception sensitivity in the optical receiver. FIG. 10 is a diagram illustrating a setting example of the modulation amplitude of the optical signal in the optical signal relay device according to the first embodiment of the present invention. FIG. 11 is a flowchart defining an example of an operation procedure when the optical signal repeater according to the first embodiment of the present invention controls the optical amplifier. FIG. 12 is a diagram illustrating a configuration of a downlink signal relay unit in a modification of the optical signal relay device according to the first embodiment of the present invention. FIG. 13 is a flowchart defining an example of an operation procedure when the modification of the optical signal relay device according to the first embodiment of the present invention controls the optical amplifier. FIG. 14 is a diagram illustrating an example of an eye pattern of an optical signal output from an optical amplifier in a non-saturated region. FIG. 15 is a diagram illustrating an example of an eye pattern of an optical signal output from an optical amplifier in a non-saturated region. FIG. 16 is a diagram illustrating a setting example of the modulation amplitude of the optical signal in the modification of the optical signal relay device according to the first embodiment of the present invention. FIG. 17 is a flowchart defining an example of an operation procedure when the modification of the optical signal relay device according to the first embodiment of the present invention controls the optical amplifier. FIG. 18 is a diagram illustrating a setting example of the gain of the modulation amplitude of the optical signal in the optical signal relay device according to the second embodiment of the present invention. FIG. 19 is a flowchart defining an example of an operation procedure when the optical signal repeater according to the second embodiment of the present invention controls the optical amplifier. FIG. 20 is a diagram illustrating a configuration of a downlink signal relay unit in a modification of the optical signal relay device according to the second embodiment of the present invention. FIG. 21 is a flowchart that defines an example of an operation procedure when the modification of the optical signal relay device according to the second embodiment of the present invention controls the optical amplifier. FIG. 22 is a diagram illustrating a setting example of the gain of the modulation amplitude of the optical signal in the modification of the optical signal relay device according to the second embodiment of the present invention. FIG. 23 is a flowchart defining an example of an operation procedure when the modification of the optical signal relay device according to the second embodiment of the present invention controls the optical amplifier. FIG. 24 is a diagram illustrating an example of the relationship between the reception level and the reception sensitivity in the optical receiver. FIG. 25 is a diagram illustrating an example of an eye pattern of an optical signal received by the optical amplifier in a state where there is no secular change. FIG. 26 is a diagram showing an example of an eye pattern of an optical signal that has changed over time received by the optical amplifier. FIG. 27 is a diagram illustrating a setting example of the time average output level of the optical signal when the extinction ratio of the input optical signal is relatively small in the optical signal relay device according to the third embodiment of the present invention. FIG. 28 is a diagram illustrating a setting example of the time average output level of the optical signal when the extinction ratio of the input optical signal is relatively large in the optical signal relay device according to the third embodiment of the present invention. FIG. 29 is a flowchart defining an example of an operation procedure when the optical signal repeater according to the third embodiment of the present invention controls the optical amplifier. FIG. 30 is a diagram illustrating an example of an eye pattern of an optical signal received by the optical amplifier in a state where there is no secular change. FIG. 31 is a diagram illustrating an example of an eye pattern of an optical signal that has changed over time received by the optical amplifier. FIG. 32 is a flowchart defining an example of an operation procedure when the modification of the optical signal relay device according to the third embodiment of the present invention controls the optical amplifier.

  First, the contents of the embodiment of the present invention will be listed and described.

  (1) An optical signal repeater according to an embodiment of the present invention receives and amplifies an optical signal having a level corresponding to a logical value of data to be transmitted, and transmits the amplified optical signal. An optical amplifier that receives and amplifies and outputs the optical signal; a measurement unit that performs measurement on the optical signal; and the light output from the optical amplifier based on a measurement result of the measurement unit And a control unit that performs drive control for adjusting the magnitude of the drive current or drive voltage supplied to the optical amplifier so that the modulation amplitude of the signal becomes a predetermined value.

  As described above, in the optical signal repeater, the modulation amplitude of the optical signal is suitable as an index indicating the characteristics of the optical signal repeater compared to the time average output level of the optical signal, and the light received by the optical receiver. When the signal modulation amplitude is the same, paying attention to the fact that the reception sensitivity of the optical receiver is the same value even when the time average output level of the optical signal is different, it is output from the optical amplifier regardless of the reception intensity of the optical signal. The drive current or drive voltage to the optical amplifier is controlled so that the modulation amplitude of the optical signal becomes a predetermined value. With such a configuration, it is possible to prevent a decrease in transmission quality and extend the communication limit distance from the optical signal repeater to the optical receiver, for example, even in the saturation region of the optical amplifier, regardless of the reception intensity of the optical signal. Further, unlike the technique described in Patent Document 1, it is not necessary to significantly reduce the intensity of input light to the optical amplifier, and an increase in power consumption in the optical amplifier accompanying an increase in gain of the optical amplifier can be prevented. . Therefore, in the optical signal repeater according to the embodiment of the present invention, in the optical signal repeater that amplifies and transmits the received optical signal, the communication limit distance of the optical communication system is extended and the power consumption is suppressed. it can.

  (2) An optical signal repeater according to an embodiment of the present invention receives and amplifies an optical signal having a level corresponding to a logical value of data to be transmitted, and transmits the amplified optical signal. An optical amplifier that receives, amplifies and outputs the optical signal; a measurement unit that performs measurement on the optical signal; and a modulation of the optical signal in the optical amplifier based on a measurement result of the measurement unit And a control unit that performs drive control to adjust the magnitude of the drive current or drive voltage supplied to the optical amplifier so that the amplitude gain becomes a predetermined value.

  As described above, in the optical signal repeater, the modulation amplitude of the optical signal is suitable as an index indicating the characteristics of the optical signal repeater compared to the time average output level of the optical signal, and the light received by the optical receiver. Paying attention to the fact that when the signal modulation amplitude is the same, even when the time average output level of the optical signal is different, the reception sensitivity of the optical receiver is the same value, and the optical signal in the optical amplifier is independent of the reception intensity of the optical signal. The drive current or drive voltage to the optical amplifier is controlled so that the gain of the modulation amplitude becomes a predetermined value. With such a configuration, it is possible to prevent a decrease in transmission quality and extend the communication limit distance from the optical signal repeater to the optical receiver, for example, even in the saturation region of the optical amplifier, regardless of the reception intensity of the optical signal. Further, unlike the technique described in Patent Document 1, it is not necessary to significantly reduce the intensity of input light to the optical amplifier, and an increase in power consumption in the optical amplifier accompanying an increase in gain of the optical amplifier can be prevented. . Therefore, in the optical signal repeater according to the embodiment of the present invention, in the optical signal repeater that amplifies and transmits the received optical signal, the communication limit distance of the optical communication system is extended and the power consumption is suppressed. it can.

  (3) An optical signal repeater according to an embodiment of the present invention receives and amplifies an optical signal having a level corresponding to a logical value of data to be transmitted, and transmits the amplified optical signal. An optical amplifier that receives, amplifies, and outputs the optical signal; and a measuring unit that performs measurement on the optical signal, and the measuring unit determines an extinction ratio of the optical signal received by the optical amplifier. And the optical signal relay device further performs a drive control for adjusting a magnitude of a drive current or a drive voltage supplied to the optical amplifier based on the extinction ratio acquired by the measurement unit. Is provided.

  Thus, paying attention to the change in the extinction ratio due to the secular change of the optical signal from the optical transmitter, the extinction ratio of the optical signal received by the optical amplifier is monitored, and the drive current to the optical amplifier is based on the extinction ratio. Or, by controlling the driving voltage, the transmission quality is prevented from deteriorating and the communication limit distance from the optical signal repeater to the optical receiver is extended, for example, even in the saturation region of the optical amplifier, regardless of the reception intensity of the optical signal. Can do. Further, unlike the technique described in Patent Document 1, it is not necessary to significantly reduce the intensity of input light to the optical amplifier, and an increase in power consumption in the optical amplifier accompanying an increase in gain of the optical amplifier can be prevented. . Therefore, in the optical signal repeater according to the embodiment of the present invention, in the optical signal repeater that amplifies and transmits the received optical signal, the communication limit distance of the optical communication system is extended and the power consumption is suppressed. it can.

  (4) Preferably, the measurement unit acquires at least one of a cross point of the optical signal output by the optical amplifier and a cross point of the optical signal received by the optical amplifier, and the control unit Based on the cross point acquired by the measurement unit, the adjustment content by the drive control is corrected.

  In this way, with the configuration for monitoring the cross point of the optical signal, for example, when distortion of the waveform of the optical signal is detected from the cross point, the modulation amplitude of the optical signal can be reduced, so that the communication quality is deteriorated. Can be suppressed.

  (5) More preferably, the measurement unit measures the high level of the optical signal and the low level of the optical signal, or the high level or low level of the optical signal and the average level of the optical signal per predetermined time Or the high level of the optical signal, the low level of the optical signal, and the average level of the optical signal per predetermined time.

  With such a configuration, various characteristics such as the modulation amplitude, cross point, and extinction ratio of the optical signal repeater can be easily obtained from the high level, low level, and average level of the optical signal.

  (6) Preferably, the optical signal relay device further includes a recovery circuit that extracts a clock from the optical signal, and the measurement unit performs the measurement using the clock extracted by the recovery circuit.

  With such a configuration, even when the modulation speed of the optical signal is high, it is possible to obtain a sufficient operation speed for acquiring various measured values of the optical signal.

  (7) Preferably, before performing the drive control, the control unit sets an average level per predetermined time of the optical signal output from the optical amplifier to a predetermined value based on a measurement result of the measurement unit. Thus, pre-drive control is performed to adjust the magnitude of the drive current or drive voltage supplied to the optical amplifier so that the average level gain in the optical amplifier becomes a predetermined value.

  With such a configuration, even when it takes time until an accurate measurement result is obtained in the measurement unit, first, control is performed so that the time average output level of the optical amplifier becomes a predetermined value with a certain degree of accuracy. Communication between the optical signal repeater and the optical receiver can be started early.

  (8) Preferably, the measurement unit acquires a cross point or an extinction ratio of the optical signal received by the optical amplifier, and the control unit is based on the cross point or the extinction ratio acquired by the measurement unit. To detect abnormalities.

  In this way, by monitoring the cross point or extinction ratio of the optical signal and detecting an abnormality, for example, maintenance and replacement of the optical transmitter can be performed at an early stage, thereby avoiding an unexpected communication failure in the optical communication system. be able to.

  (9) A communication control method according to an embodiment of the present invention receives and amplifies an optical signal having a level corresponding to a logical value of data to be transmitted, and transmits the amplified optical signal. A communication control method for controlling the optical signal, wherein the optical signal repeater includes an optical amplifier that receives, amplifies, and outputs the optical signal, and the communication control method performs a measurement on the optical signal; Based on the measurement result, so that the modulation amplitude of the optical signal output from the optical amplifier becomes a predetermined value, so that the gain of the modulation amplitude of the optical signal in the optical amplifier becomes a predetermined value, or Performing drive control for adjusting the magnitude of the drive current or drive voltage supplied to the optical amplifier based on the extinction ratio of the optical signal received by the optical amplifier obtained by the measurement.

  Thus, compared with the time average output level of the optical signal, the modulation amplitude of the optical signal is suitable as an index indicating the characteristics of the optical signal repeater, and the modulation amplitude of the optical signal received by the optical receiver is the same. In this case, paying attention to the fact that the reception sensitivity of the optical receiver has the same value even when the time average output level of the optical signal is different, the modulation amplitude of the optical signal output from the optical amplifier is independent of the reception intensity of the optical signal. Alternatively, the drive current or drive voltage to the optical amplifier is controlled so that the gain of the modulation amplitude becomes a predetermined value. Alternatively, paying attention to the change in the extinction ratio due to the secular change of the optical signal from the optical transmitter, the extinction ratio of the optical signal received by the optical amplifier is monitored, and the drive current or drive to the optical amplifier is based on the extinction ratio Control the voltage.

  Accordingly, it is possible to prevent the transmission quality from being lowered and to extend the communication limit distance from the optical signal repeater to the optical receiver, for example, even in the saturation region of the optical amplifier, regardless of the reception intensity of the optical signal. Further, unlike the technique described in Patent Document 1, it is not necessary to significantly reduce the intensity of input light to the optical amplifier, and an increase in power consumption in the optical amplifier accompanying an increase in gain of the optical amplifier can be prevented. . Therefore, in the communication control method according to the embodiment of the present invention, in the optical signal relay device that amplifies and transmits the received optical signal, the communication limit distance of the optical communication system can be extended and the power consumption can be suppressed. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated. Moreover, you may combine arbitrarily at least one part of embodiment described below.

<First Embodiment>
[Configuration and basic operation]
FIG. 1 is a diagram showing a configuration of an optical communication system according to the first embodiment of the present invention.

  Referring to FIG. 1, an optical communication system 301 is, for example, a GE-PON, a station side device 201 connected to an upper network, an optical signal relay device 101, one or a plurality of ONUs 202, an optical coupler 211, 212. The optical communication system 301 may be a 10G-EPON, or another type of optical communication system.

  The station-side device 201 is an optical termination device located on the upper side of the PON, and is installed in a telephone station, a substation, or the like, and communicates with a plurality of ONUs 202. The ONU 202 is an optical terminator located on the lower side of the PON. The ONU 202 is installed on a subscriber-side building, an outdoor utility pole, or the like, and communicates with one station-side device 201.

  In the optical communication system 301, each ONU 202 is connected to a plurality of optical fibers branched from the optical coupler 211. The optical coupler 211 and the optical signal relay device 101 are connected via one optical fiber. The optical coupler 212 and the optical signal relay device 101 are connected via one optical fiber. One or more ONUs 202 are also connected to the optical fiber branched from the optical coupler 212. The optical coupler 212 and the station side device 201 are connected via one optical fiber.

  As described above, in the optical communication system 301, the station side apparatus 201 or the optical signal relay apparatus 101 and an arbitrary number of ONUs 202 can be connected by a configuration using a plurality of optical couplers.

  Each ONU 202 and the station-side device 201 are connected via an optical fiber and an optical coupler and via the optical signal relay device 101 according to the connection position of the ONU 202, and transmit / receive optical signals to / from each other. In the optical communication system 301, each ONU 202 transmits an upstream optical signal to the station apparatus 201 via a common communication line, that is, a PON line, and the optical signal from each ONU 202 to the station apparatus 201 is time-division multiplexed. The In the optical communication system 301, a continuous optical signal is transmitted from the station side device 201 to each ONU 202.

  The station-side device 201 can transmit and receive optical signals to and from the ONU 202 via the optical signal relay device 101 connected between itself and the ONU 202.

  The optical signal relay device 101 relays the optical signal transmitted from the station side device 201 to the ONU 202 and relays the optical signal transmitted from the ONU 202 to the station side device 201.

  Hereinafter, the direction from the ONU to the upper network is referred to as an upstream direction, and the direction from the upper network to the ONU is referred to as a downstream direction.

  FIG. 2 is a diagram showing a configuration of the optical signal repeater according to the first embodiment of the present invention.

  With reference to FIG. 2, the optical signal relay device 101 includes an electrical / optical converter 11, a downstream signal relay unit 12, an optical / electrical converter 13, and an upstream signal regeneration unit 14.

  The optical / electrical converter 13 receives the upstream optical signal transmitted from the ONU 202, converts it into an electrical signal, and outputs the electrical signal to the upstream signal regeneration unit 14.

  The upstream signal regeneration unit 14 extracts, for example, a clock from the electrical signal received from the optical / electrical converter 13, performs waveform shaping of the electrical signal using the extracted clock, and converts the electrical signal into the electrical / optical converter. 11 to output.

  The electrical / optical converter 11 converts the electrical signal received from the upstream signal reproduction unit 14 into an upstream optical signal and transmits the upstream signal to the station apparatus 201.

  The downlink signal relay unit 12 receives the downlink optical signal transmitted from the station side device 201, amplifies the received downlink optical signal, and transmits the amplified signal to the ONU 202. The upstream optical signal and downstream optical signal have levels according to the logical value of the data to be transmitted. The duty ratio of the upstream optical signal and downstream optical signal is, for example, 50%.

[Task]
As described above, the distance from the optical transmitter to the optical signal repeater and the distance from the optical signal repeater to the optical receiver often vary depending on the installation location of the optical communication system. For this reason, the optical signal repeater receives optical signals of various strengths.

  FIG. 3 is a diagram illustrating an example of the relationship between the intensity and gain of input light in the optical amplifier. In FIG. 3, the horizontal axis indicates the time average input level of the optical amplifier, that is, the average level of input light per predetermined time, and the unit is [dBm]. The vertical axis represents the gain of the optical amplifier, and its unit is [dB]. Graphs G1 to G4 show cases where the drive currents supplied to the optical amplifier are 399 mA, 299 mA, 199 mA, and 99 mA, respectively.

  Referring to FIG. 3, the optical amplifier has a characteristic that the gain increases as the drive current increases.

  In the optical signal repeater, when the intensity of the received optical signal is high, the output of the optical amplifier is saturated. That is, the gain of the optical amplifier is saturated. Here, the saturated region is defined as a region having a time average input level in which the gain decreases by 0.2 dB or more from the gain in the non-saturated region. In this example, when the drive current supplied to the optical amplifier is 199 mA, a region where the time average input level is less than −20 dBm is a non-saturated region, and a region where −20 dBm or more is a saturated region.

  When the output of the optical amplifier is saturated, the transmission quality of the optical signal is lowered, and the communication limit distance from the optical communication system, specifically, the optical signal repeater to the optical receiver is reduced.

  For example, when the optical amplifier described in Patent Document 1 is applied to an optical signal repeater, the intensity of input light to the optical amplifier is reduced in order to avoid saturation of the optical amplifier, that is, the operating point of the optical amplifier is set as a non-saturation region. Control is performed in the vicinity of the boundary with the saturation region.

  However, as shown in FIG. 3, the time-average input level that becomes a non-saturated region is as small as −20 dBm. For this reason, in order to obtain a desired communication limit distance, it is necessary to increase the drive current supplied to the optical amplifier to increase the intensity of the output light of the optical amplifier, resulting in an increase in power consumption.

  Further, there may be a case where the gain of the optical amplifier such that the output light has a desired intensity cannot be obtained. For example, when the intensity of the output light is desired to be in a range of about ± 10 dBm, it is necessary to set the time average input level in the saturation region instead of the non-saturation region in consideration of the characteristics of a general optical amplifier.

  Moreover, in the technique described in Patent Document 1, it is necessary to add a part or the like for adjusting the intensity of input light to the optical amplifier, which increases the manufacturing cost.

  Here, in a digital communication system using optical communication, for example, a modulation method called OOK (on / off keying) that transmits a digital signal in two ways of on and off of light is employed.

  As an index of the characteristics of the optical transmitter in such a system, for example, a predetermined time of the level of an optical signal having a high level of optical output corresponding to light on and a low level of optical output corresponding to light off A time average level is used, which is an average value around. Further, for example, an extinction ratio that is a ratio of the high level of the optical output to the low level of the optical output, for example, the modulation amplitude that is the difference between the high level of the optical output and the low level of the optical output, and the rising transition of the high level of the optical output A cross point indicating the waveform quality obtained from the time and the low level falling transition time of the optical output and the duty ratio is used.

  Further, as control related to optical signal transmission in the optical signal repeater, for example, ALC (auto level control) for controlling the time average output level to be constant, and gain for the time average input level and time average output level are controlled to be constant. AGC (Auto Gain Control) is used.

  Here, amplitude modulation of the optical signal is performed by changing the intensity of the light. As the intensity of the optical signal received by the optical signal repeater increases, the optical amplifier in the optical signal repeater becomes saturated. Due to this saturation, in the optical amplifier, the low level amplification factor of the optical output and the high level amplification factor of the optical output depend on the intensity of the input optical signal, specifically, the difference between the low level and the high level of the input optical signal. Different values. Therefore, in the optical signal repeater, even if the time average output level of the optical signal is controlled to be constant, unlike the optical transmitter, the modulation amplitude is not constant, and communication from the optical signal repeater to the optical receiver is performed. There is a difference in distance.

  FIG. 4 is a diagram illustrating an example of an eye pattern of an optical signal output from an optical amplifier in a non-saturated region. FIG. 5 is a diagram illustrating an example of an eye pattern of an optical signal output from the optical amplifier in the saturation region. 4 and 5, the horizontal axis represents time, and the vertical axis represents the optical output level of the optical amplifier. W1 indicates an eye pattern in the non-saturated region, and W2 indicates an eye pattern in the saturated region.

  Referring to FIGS. 4 and 5, even if the time average output level of the optical signal of the optical signal repeater is controlled to be constant, various characteristics are determined depending on whether the optical amplifier is in the non-saturation region or the saturation region. Therefore, a difference occurs in the communication limit distance from the optical signal repeater to the optical receiver.

  Specifically, the waveform of the eye pattern W2 in the saturation region is distorted compared to the eye pattern W1 in the non-saturation region. For this reason, when the optical amplifier is in the saturation region, the high level of the optical output becomes small. That is, the light output high level P1d in the saturation region is smaller than the light output high level P1 in the non-saturation region.

  More specifically, in the non-saturated region and the saturated region, the extinction ratio, which is the ratio between the high level P1 of the optical output and the low level P0 of the optical output, is different from P1 / P0 or P1d / P0d, and the time average output level is ( Unlike (P1-P0) / 2 or (P1d-P0d) / 2, the modulation amplitude, which is the difference between the high level of the optical output and the low level of the optical output, is different from (P1-P0) or (P1d-P0d). The point is different from Xp or Xpd.

  FIG. 6 is a diagram illustrating an example of a difference in eye pattern depending on the presence or absence of ASE.

  Semiconductor optical amplifiers (SOA) and erbium-doped fiber amplifiers (EDFA: Erbium Doped Fiber Amplifiers), which are examples of optical amplifiers, emit spontaneously emitted light (ASE: Amplified SpongeEstimated Emission) even in the absence of an optical signal. Occur.

  In FIG. 6, the vertical axis indicates the optical output level of the optical amplifier. W11 shows an eye pattern when there is no ASE, and W12 shows an eye pattern when there is ASE.

  Referring to FIG. 6, the extinction ratio of the optical signal varies depending on the presence or absence of ASE. That is, P1 / P0 ≠ P1d / P0d. On the other hand, the modulation amplitude of the optical signal is the same regardless of the presence or absence of ASE. That is, (P1-P0) = (P1d-P0d).

  The inventors of the present application pay attention to the fact that the modulation amplitude of the optical signal does not change depending on the presence or absence of ASE, and is suitable as an index indicating the characteristics of the optical signal repeater compared with the time average output level of the optical signal. I found a way to solve these problems. That is, the optical signal repeater according to the embodiment of the present invention solves the above-described problems by the following configuration and operation.

  FIG. 7 is a diagram illustrating a configuration of a downlink signal relay unit in the optical signal relay device according to the first embodiment of the present invention.

  Referring to FIG. 7, downlink signal relay unit 12 includes optical amplifier 21, optical couplers 22, 23, current supply unit 24, input detection unit 25, control unit 26, output detection unit 27, and measurement. Part 28.

  The optical coupler 22 branches the downstream optical signal received from the station side device 201 and outputs the branched optical signal to the optical amplifier 21 and the input detection unit 25.

  The optical amplifier 21 is a semiconductor optical amplifier, for example, and amplifies the downstream optical signal received from the optical coupler 22 and outputs it to the optical coupler 23. The gain of the optical amplifier 21 changes according to the drive current supplied from the current supply unit 24. Specifically, for example, as a general characteristic tendency, the gain of the optical amplifier 21 increases as the drive current increases, and the gain of the optical amplifier 21 decreases as the drive current decreases.

  The optical coupler 23 branches the downstream optical signal received from the optical amplifier 21 and outputs the branched optical signal to the ONU 202 and the output detection unit 27.

  The input detection unit 25 includes a light receiving element 31 such as a photodiode. In the input detection unit 25, the light receiving element 31 generates a current having a magnitude corresponding to the intensity of the downstream optical signal received from the optical coupler 22, that is, a current having a magnitude corresponding to the intensity of the input light of the optical amplifier 21. Output to.

  The output detection unit 27 includes a light receiving element 32 such as a photodiode. In the output detection unit 27, the light receiving element 32 generates a current having a magnitude corresponding to the intensity of the downstream optical signal received from the optical coupler 23, that is, a current having a magnitude corresponding to the intensity of the output light from the optical amplifier 21. Output to.

  Measurement unit 28 includes, for example, two sets of a current-voltage conversion circuit and an A / D converter (not shown). The first set of current / voltage conversion circuits converts the output current of the light receiving element 31 received from the input detection unit 25 into a voltage and outputs the voltage. The A / D converter generates a digital signal indicating the level of the voltage received from the current-voltage conversion circuit. The second set of current / voltage conversion circuits converts the output current of the light receiving element 32 received from the output detection unit 27 into a voltage and outputs the voltage. The A / D converter generates a digital signal indicating the level of the voltage received from the current-voltage conversion circuit.

  For example, the measurement unit 28 performs a measurement on the downstream optical signal based on at least one of the digital signal generated by the first set of A / D converters and the digital signal generated by the second set of A / D converters. The measurement information indicating the measurement result is output to the control unit 26.

  The control unit 26 determines the magnitude of the drive current based on the measurement information received from the measurement unit 28 and outputs a control signal indicating the determined magnitude of the drive current to the current supply unit 24.

  The current supply unit 24 supplies the drive current to the optical amplifier 21 and changes the magnitude of the drive current supplied to the optical amplifier 21 according to the control signal received from the control unit 26.

  The optical signal repeater 101 may be configured to include, as the optical amplifier 21, an optical fiber amplifier such as an erbium-doped fiber amplifier and Raman amplification instead of the semiconductor optical amplifier.

  In this case, an amplifying fiber is connected between the optical coupler 22 and the optical coupler 23, pump light is injected into the optical signal transmission path before the amplifying fiber using a laser diode, and an optical signal is transmitted after the amplifying fiber. The pump light is separated from the transmission line. By changing the drive current value of the laser diode, the intensity of the pump light changes and the gain of the optical fiber amplifier is controlled.

  FIG. 8 is a diagram illustrating an example of the relationship between the reception level and the reception sensitivity in the optical receiver. In FIG. 8, the horizontal axis indicates the time average input level of the optical receiver, that is, the average of the reception level of the optical signal per predetermined time, and the vertical axis indicates the BER (Bit Error Ratio) corresponding to the reception sensitivity. Graphs G11 to G13 show cases where the modulation amplitudes of the optical signals are +5.5 dBm, +6.0 dBm, and +6.8 dBm, respectively.

  Referring to FIG. 8, the reception sensitivity of the optical receiver, that is, the BER with respect to the time average input level varies depending on the modulation amplitude of the optical signal. That is, even if the time average input level of the optical signal in the optical receiver is the same, if the modulation amplitude of the optical signal is different, the reception sensitivity of the optical receiver has a different value. Specifically, when the modulation amplitude of the optical signal decreases, the reception sensitivity of the optical receiver deteriorates.

  FIG. 9 is a diagram illustrating an example of the relationship between the modulation amplitude and the reception sensitivity in the optical receiver. In FIG. 9, the horizontal axis represents the modulation amplitude of the optical signal received by the optical receiver, and the vertical axis represents the BER corresponding to the reception sensitivity. Graphs G21 to G23 show cases where the time average output levels of the optical signals are +6.0 dBm, +6.5 dBm, and +7.0 dBm, respectively.

  Referring to FIG. 9, the reception sensitivity of the optical receiver, that is, the BER with respect to the modulation amplitude of the optical signal is constant regardless of the time average output level of the optical signal. That is, even if the time average output level of the optical signal is different, the reception sensitivity of the optical receiver has the same value when the modulation amplitude of the optical signal received by the optical receiver is the same.

  In addition to the fact that the modulation amplitude of the optical signal does not change depending on the presence or absence of ASE as described above, the inventors of the present application are suitable as an index indicating the characteristics of the optical signal repeater compared to the time average output level of the optical signal. Therefore, when the modulation amplitude of the optical signal received by the optical receiver is the same, even when the time average output level of the optical signal is different, the reception sensitivity of the optical receiver is the same value. I found a way to solve the problem. That is, in the optical signal repeater according to the first embodiment of the present invention, the output level of the optical signal is controlled so that the modulation amplitude of the optical signal transmitted to the optical receiver becomes a predetermined value. In this case, the drive current to the optical amplifier is controlled.

  That is, the control unit 26 sets the magnitude of the drive current supplied to the optical amplifier 21 based on the measurement result of the measurement unit 28 so that the modulation amplitude of the optical signal output from the optical amplifier 21 becomes a predetermined value. The drive control to be adjusted is performed.

  More specifically, the measurement unit 28 obtains the high level and low level of the optical signal output from the optical amplifier 21 from the output current of the light receiving element 32 received from the output detection unit 27, and the high level of the optical signal. The low level difference is calculated as the modulation amplitude of the optical signal output from the optical amplifier 21. The measurement unit 28 acquires the high level and time average output level of the optical signal output from the optical amplifier 21 from the output current of the light receiving element 32 received from the output detection unit 27, and the high level of the optical signal and The modulation amplitude of the optical signal may be calculated from the time average output level. In addition, the measurement unit 28 acquires the low level and the time average output level of the optical signal output from the optical amplifier 21 from the output current of the light receiving element 32 received from the output detection unit 27, and the low level of the optical signal and The modulation amplitude of the optical signal may be calculated from the time average output level.

  Specifically, the measuring unit 28 calculates, for example, high level and low level peak hold values of the output current of the light receiving element 32 or average values of high level and low level of the output current of the light receiving element 32, respectively. To obtain the high level and low level of the optical signal.

  FIG. 10 is a diagram illustrating a setting example of the modulation amplitude of the optical signal in the optical signal relay device according to the first embodiment of the present invention.

  Referring to FIG. 10, here, when the modulation amplitude of the optical signal received by the optical receiver is −28.5 dBm or more, the receiving sensitivity of the optical receiver is good. Specifically, the BER in the optical receiver is Is 10E-12, that is, less than 10 to the negative twelfth power.

  When the upper limit of the distance from the optical signal repeater 101 to the optical receiver is 10 km and the optical signal is attenuated by 25 dB at the maximum, the modulation amplitude of the optical signal transmitted from the optical signal repeater 101 is set to −3.5 dBm or more. To do. When the upper limit of the distance from the optical signal repeater 101 to the optical receiver is 20 km and the optical signal is attenuated by 30 dB at the maximum, the modulation amplitude of the optical signal transmitted from the optical signal repeater 101 is +2.5 dBm or more. Set. Further, when the upper limit of the distance from the optical signal repeater 101 to the optical receiver is 30 km, when the optical signal is attenuated by 35 dB at the maximum, the modulation amplitude of the optical signal transmitted from the optical signal repeater 101 is +7.5 dBm or more. Set.

[Operation]
Next, the operation of the optical signal repeater in the optical communication system according to the first embodiment of the present invention will be described.

  Each device in the optical communication system 301 includes a computer, and an arithmetic processing unit such as a CPU in the computer reads and executes a program including a part or all of each step of the following flowchart from a memory (not shown). Each of the programs of the plurality of apparatuses can be installed from the outside. The programs of the plurality of apparatuses are distributed while being stored in a recording medium.

  FIG. 11 is a flowchart defining an example of an operation procedure when the optical signal repeater according to the first embodiment of the present invention controls the optical amplifier.

  Referring to FIG. 11, first, optical signal relay apparatus 101 measures the output current of light receiving element for monitoring, here light receiving element 32 (step S1).

  Next, the optical signal repeater 101 calculates the modulation amplitude of the output optical signal, that is, the optical signal output from the optical amplifier 21, based on the measurement result (step S2).

  Next, when the calculated modulation amplitude is less than the predetermined threshold Th1 (YES in step S3), the optical signal repeater 101 increases the drive current supplied to the optical amplifier 21 to increase the modulation amplitude of the output optical signal. Drive control is performed to increase the value (step S4).

  On the other hand, when the calculated modulation amplitude is greater than or equal to the predetermined threshold Th1 (NO in step S3), the optical signal repeater 101 reduces the modulation amplitude of the output optical signal by reducing the drive current supplied to the optical amplifier 21. Drive control is performed to make it smaller (step S5).

  The optical signal relay device 101 continuously or irregularly measures the output current of the light receiving element 32 (step S1).

[Modification 1]
When the modulation speed of the optical signal is low, the acquisition speed of the output current of the light receiving element 32 by the measurement unit 28, that is, the acquisition speed of the high level and low level of the optical signal, for example, part or all of the measurement unit 28 is realized. By making the speed equal to the operation speed of MPU (Micro Processing Unit), it is possible to follow the change in the level of the optical signal.

  On the other hand, when the modulation speed of the optical signal is high, it is necessary to make the acquisition speed sufficiently higher than the operation speed.

  FIG. 12 is a diagram illustrating a configuration of a downlink signal relay unit in a modification of the optical signal relay device according to the first embodiment of the present invention.

  Referring to FIG. 12, downlink signal relay unit 12 further includes a CDR (clock / data recovery circuit: Clock and Data Recovery) 29 compared to downlink signal relay unit 12 shown in FIG. 7.

  The CDR 29 extracts the data and clock included in the optical signal from the output current of the light receiving element 32 received from the output detection unit 27, and outputs the extracted data and clock to the measurement unit 28.

  The measurement unit 28 performs measurement on the optical signal using the clock extracted by the CDR 29.

  More specifically, the measurement unit 28 includes an A / D converter. This A / D converter samples and holds the data received from the CDR 29 using the clock received from the CDR 29 as a trigger. The measurement unit 28 acquires the high level and low level of the optical signal from the sampled and held data. Note that the measurement unit 28 may include a circuit that adjusts the phase of the clock received from the CDR 29, and may acquire the high level and low level of the optical signal using the clock after the phase adjustment as a trigger.

  Here, when it takes time to adjust the clock phase in the measurement unit 28 as described above, first, control is performed so that the time average output level of the optical signal from the optical amplifier 21 becomes a predetermined value with a certain degree of accuracy. Then, after phase adjustment is performed so that accurate high and low levels of the optical signal are obtained, control is performed so that the modulation amplitude of the optical signal becomes a predetermined value. As a result, communication between the optical signal repeater 101 and the optical receiver can be started early without waiting for completion of the phase adjustment.

  FIG. 13 is a flowchart defining an example of an operation procedure when the modification of the optical signal relay device according to the first embodiment of the present invention controls the optical amplifier.

  Before performing the drive control, the control unit 26 controls the optical amplifier 21 so that the average level per predetermined time of the optical signal output from the optical amplifier 21 becomes a predetermined value based on the measurement result of the measurement unit 28. Pre-drive control is performed to adjust the magnitude of the supplied drive current. The measurement unit 28 performs measurement on the optical signal in a state where the pre-drive control is performed.

  Specifically, referring to FIG. 13, first, the optical signal repeater 101 performs pre-drive control at a predetermined timing so that the time average output level of the optical signal output from the optical amplifier 21 becomes a predetermined value. Start. Thereby, communication between the station-side apparatus 201 and the ONU 202 via the optical signal relay apparatus 101 is started (step S11).

  Next, the optical signal relay apparatus 101 continues the pre-drive control until a predetermined time has elapsed from the predetermined timing (NO in step S12). While the pre-drive control is being performed, the clock phase adjustment in the measurement unit 28 is completed.

  Next, when a predetermined time has elapsed from the predetermined timing (YES in step S12), the optical signal repeater 101 measures the output current of the light receiving element 32 (step S13), and modulates the optical signal output from the optical amplifier 21. Calculation of the amplitude (step S14) and adjustment of the drive current supplied to the optical amplifier 21 are started (steps S15 to S17).

  The operations in steps S13 to S17 are the same as the operations in steps S1 to S5 shown in FIG.

[Modification 2]
The cross point of the optical signal is an index indicating the waveform quality of the optical signal.

  When the high level of the optical output is 100% and the low level of the optical output is 0%, the degree of saturation in the optical amplifier is large when the cross point is deviated from 50%.

  FIG. 14 is a diagram illustrating an example of an eye pattern of an optical signal output from an optical amplifier in a non-saturated region. The way of viewing the figure is the same as in FIG.

  Referring to FIG. 14, when the optical amplifier is in a non-saturated region, the cross point Xp is 50% when the high level P1 of the optical output is 100% and the low level P0 of the optical output is 0%. Further, the actually measured value of the time average output level and the calculated value (P1−P0) / 2 at the midpoint of the modulation amplitude are equivalent values.

  FIG. 15 is a diagram illustrating an example of an eye pattern of an optical signal output from an optical amplifier in a non-saturated region. The way of viewing the figure is the same as in FIG.

  Referring to FIG. 15, when the optical amplifier is in the saturation region, the high level of the optical output becomes small. Specifically, the light output high level P1d in the saturation region is smaller than the light output high level P1 in the non-saturation region.

  The time average output level is a time integral value of the high level of the optical output and the low level of the optical output. Therefore, when the high level P1d of the optical output is 100% and the low level P0d of the optical output is 0%, the cross point Will not be 50%. Further, the actually measured value of the time average output level and the calculated value (P1d−P0d) / 2 at the midpoint of the modulation amplitude are different values.

  Further, when the degree of saturation in the optical amplifier is large, the waveform of the eye pattern is distorted and the cross point becomes large.

  As shown in FIGS. 14 and 15, the inventors of the present application pay attention to the point that the cross point is suitable as an index indicating the characteristics of the optical signal repeater, and a method for further improving the communication of the optical communication system. discovered.

  That is, in the optical signal relay device 101, the measurement unit 28 acquires the cross point of the optical signal output from the optical amplifier 21. For example, the measurement unit 28 determines the high level of the optical signal output from the optical amplifier 21, that is, the high level of the optical output, the low level of the optical signal, that is, the low level of the optical output, and the average level of the optical signal per predetermined time. Measure and use this measurement result to calculate the crosspoint.

  The control unit 26 corrects the adjustment content by the drive control based on the cross point acquired by the measurement unit 28.

  FIG. 16 is a diagram illustrating a setting example of the modulation amplitude of the optical signal in the modification of the optical signal relay device according to the first embodiment of the present invention.

  When the optical receiver receives an optical signal with an eye pattern having a cross point of 70% or more, for example, the penalty of the optical receiver's reception sensitivity increases. Specifically, the reception quality of the optical signal at the optical receiver is increased. Deteriorating, for example, the graph shown in FIG. That is, the BER obtained with the same modulation amplitude is increased.

  For this reason, when the cross point becomes 70% or more, the modulation amplitude of the output optical signal is reduced to reduce the cross point to less than 70%, thereby suppressing the distortion of the waveform of the output optical signal, and the reception sensitivity of the optical receiver. Suppress the penalty. Thereby, degradation of communication quality can be suppressed.

  Specifically, referring to FIG. 16, control unit 26 sets, for example, a cross-point threshold value Th <b> 2 at a cross-point boundary value at which the reception sensitivity penalty of the optical receiver deteriorates to some extent.

  When the cross point of the optical signal output from the optical amplifier 21 is the threshold Th2, that is, 70% or more, the control unit 26 increases the reception sensitivity penalty of the optical receiver from 0.5 dB. The modulation amplitude of the optical signal is reduced so that is smaller than 70%.

  On the other hand, when the cross point of the optical signal output from the optical amplifier 21 is less than the threshold Th2, that is, less than 70%, the control unit 26 increases the reception sensitivity penalty of the optical receiver within 0.5 dB. From this, the modulation amplitude of the optical signal is maintained. In addition, when the cross point is less than the threshold Th2, the control unit 26 may increase the modulation amplitude of the optical signal so that the cross point becomes large with 70% being the upper limit.

  FIG. 17 is a flowchart defining an example of an operation procedure when the modification of the optical signal relay device according to the first embodiment of the present invention controls the optical amplifier.

  Referring to FIG. 17, the operations in steps S21 to S25 are the same as the operations in steps S1 to S5 shown in FIG.

  Next, the optical signal relay device 101 calculates the cross point of the output optical signal, that is, the optical signal output from the optical amplifier 21 based on the measurement result of the output current of the light receiving element 32. Specifically, the optical signal repeater 101 acquires the high level and low level of the optical signal and the time average output level, and uses the midpoint of the modulation amplitude as a 50% cross point to modulate the time average output level and the modulation. A cross point is calculated based on the difference from the midpoint of the amplitude (step S26).

  Next, when the calculated cross point is larger than the predetermined threshold Th2 (YES in step S27), the optical signal relay apparatus 101 reduces the modulation amplitude of the output optical signal by reducing the drive current supplied to the optical amplifier 21. Decrease (step S28).

  On the other hand, when the calculated cross point is equal to or less than the predetermined threshold Th2, the optical signal relay device 101 maintains the value of the drive current supplied to the optical amplifier 21 (NO in step S27).

  The optical signal relay device 101 continuously or irregularly measures the output current of the light receiving element 32 (step S21).

  Incidentally, the distance from the optical transmitter to the optical signal repeater and the distance from the optical signal repeater to the optical receiver differ depending on the installation location of the optical communication system. For this reason, the optical signal repeater receives optical signals of various strengths.

  In an optical signal repeater that amplifies an optical signal received from an optical transmitter using an optical amplifier without converting it into an electrical signal and transmits the optical signal to the optical receiver, if the received optical signal has a high intensity, The output is saturated and the transmission quality of the optical signal is lowered, and the optical communication system, specifically, the communication limit distance from the optical signal repeater to the optical receiver is reduced.

  For example, when the optical amplifier described in Patent Document 1 is applied to an optical signal repeater, control is performed to reduce the intensity of input light to the optical amplifier in order to avoid saturation of the optical amplifier. In this case, in order to obtain a desired communication limit distance, it is necessary to increase the gain by increasing the drive current supplied to the optical amplifier and increase the intensity of the output light of the optical amplifier, resulting in an increase in power consumption.

  On the other hand, in the optical signal repeater according to the first embodiment of the present invention, the optical amplifier 21 receives an optical signal, amplifies it, and outputs it. The measurement unit 28 performs measurement related to the optical signal. Then, the control unit 26 determines the magnitude of the drive current supplied to the optical amplifier 21 based on the measurement result of the measurement unit 28 so that the modulation amplitude of the optical signal output from the optical amplifier 21 becomes a predetermined value. The drive control to be adjusted is performed.

  As described above, in the optical signal repeater 101, the optical receiver receives the point that the modulation amplitude of the optical signal is suitable as an index indicating the characteristics of the optical signal repeater compared to the time average output level of the optical signal. When the modulation amplitude of the optical signal is the same, it is noted that the reception sensitivity of the optical receiver is the same value even when the time average output level of the optical signal is different. From the optical amplifier 21 regardless of the reception intensity of the optical signal. The drive current to the optical amplifier 21 is controlled so that the modulation amplitude of the output optical signal becomes a predetermined value.

  With such a configuration, it is possible to prevent a decrease in transmission quality and extend the communication limit distance from the optical signal repeater 101 to the optical receiver, for example, even in the saturation region of the optical amplifier 21, regardless of the reception intensity of the optical signal. it can. Further, unlike the technique described in Patent Document 1, it is not necessary to significantly reduce the intensity of input light to the optical amplifier, and an increase in power consumption in the optical amplifier accompanying an increase in gain of the optical amplifier can be prevented. .

  Therefore, in the optical signal repeater according to the first embodiment of the present invention, in the optical signal repeater that amplifies and transmits the received optical signal, the communication limit distance of the optical communication system is increased and the power consumption is suppressed. can do.

  In the optical signal repeater according to the first embodiment of the present invention, the measurement unit 28 acquires the cross point of the optical signal output from the optical amplifier 21. And the control part 26 correct | amends the adjustment content by drive control based on the cross point acquired by the measurement part 28. FIG.

  Thus, with the configuration for monitoring the cross point of the optical signal output from the optical amplifier 21, for example, when distortion of the waveform of the optical signal is detected from the cross point, the modulation amplitude of the optical signal can be reduced. Therefore, deterioration of communication quality can be suppressed.

  In the optical signal repeater according to the first embodiment of the present invention, the measurement unit 28 measures the high level of the optical signal and the low level of the optical signal for the output optical signal, or the optical signal The high level or low level of the optical signal and the average level of the optical signal per predetermined time, or the high level of the optical signal, the low level of the optical signal, and the average level of the optical signal per predetermined time Measure.

  With such a configuration, various characteristics such as the modulation amplitude and cross point of the optical signal repeater 101 can be easily obtained from the high level, low level and average level of the optical signal.

  In the optical signal repeater according to the first embodiment of the present invention, the CDR 29 extracts a clock from the optical signal. Then, the measurement unit 28 performs measurement on the optical signal using the clock extracted by the CDR 29.

  With such a configuration, even when the modulation speed of the optical signal is high, it is possible to obtain a sufficient operation speed for acquiring various measured values of the optical signal.

  Further, in the optical signal relay device according to the first embodiment of the present invention, the control unit 26 performs the optical signal output from the optical amplifier 21 based on the measurement result of the measurement unit 28 before performing the drive control. The pre-drive control is performed to adjust the magnitude of the drive current supplied to the optical amplifier 21 so that the average level per predetermined time becomes a predetermined value.

  With such a configuration, even when it takes time for the measurement unit 28 to obtain an accurate measurement result, control is first performed so that the time average output level of the optical amplifier 21 becomes a predetermined value with a certain degree of accuracy. And communication between the optical signal repeater 101 and the optical receiver can be started early.

  Further, in the communication control method according to the first embodiment of the present invention, first, measurement relating to an optical signal is performed. Next, based on the measurement result, drive control is performed to adjust the magnitude of the drive current supplied to the optical amplifier 21 so that the modulation amplitude of the optical signal output from the optical amplifier 21 becomes a predetermined value. .

  As described above, in the optical signal repeater 101, the optical receiver receives the point that the modulation amplitude of the optical signal is suitable as an index indicating the characteristics of the optical signal repeater compared to the time average output level of the optical signal. When the modulation amplitude of the optical signal is the same, it is noted that the reception sensitivity of the optical receiver is the same value even when the time average output level of the optical signal is different. From the optical amplifier 21 regardless of the reception intensity of the optical signal. The drive current to the optical amplifier 21 is controlled so that the modulation amplitude of the output optical signal becomes a predetermined value.

  Accordingly, it is possible to prevent the transmission quality from being lowered and to extend the communication limit distance from the optical signal repeater 101 to the optical receiver, for example, even in the saturation region of the optical amplifier 21, regardless of the reception intensity of the optical signal. Further, unlike the technique described in Patent Document 1, it is not necessary to significantly reduce the intensity of input light to the optical amplifier, and an increase in power consumption in the optical amplifier accompanying an increase in gain of the optical amplifier can be prevented. .

  Therefore, in the communication control method according to the first embodiment of the present invention, in the optical signal repeater that amplifies and transmits the received optical signal, the communication limit distance of the optical communication system is increased and the power consumption is suppressed. be able to.

  In the optical communication system according to the first embodiment of the present invention, the optical signal repeater 101 is configured to include the control unit 26 and the measurement unit 28. However, the present invention is not limited to this. A device other than the optical signal repeater 101 in the optical communication system 301 includes the control unit 26 and the measurement unit 28, and monitors the output light of the optical amplifier and controls the drive current to the optical amplifier. Good.

  In the optical communication system according to the first embodiment of the present invention, the configuration is such that the output light of the optical amplifier is monitored and the drive current to the optical amplifier is performed in the downstream direction. Instead of this, it is also possible to adopt a configuration in which the output light of the optical amplifier is monitored and the drive current to the optical amplifier is monitored in the upstream direction as in the downstream direction.

  Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

<Second Embodiment>
The present embodiment relates to an optical communication system in which the control reference of the optical amplifier is changed as compared with the optical communication system according to the first embodiment. The contents other than those described below are the same as those of the optical communication system according to the first embodiment.

  In addition to the fact that the modulation amplitude of the optical signal does not change depending on the presence / absence of ASE and is suitable as an index indicating the characteristics of the optical signal repeater as described above, the inventors of the present application have added the optical signal received by the optical receiver. Focusing on the fact that the reception sensitivity of the optical receiver has the same value when the modulation amplitudes are the same, a method different from the first embodiment was further discovered as a method for solving the above problem. That is, in the optical signal repeater according to the second embodiment of the present invention, the output level of the optical signal is controlled so that the gain of the modulation amplitude of the optical signal in the optical amplifier becomes a predetermined value. Controls the drive current to the optical amplifier.

  That is, the control unit 26 adjusts the magnitude of the drive current supplied to the optical amplifier 21 based on the measurement result of the measurement unit 28 so that the gain of the modulation amplitude of the optical signal in the optical amplifier 21 becomes a predetermined value. The drive control is performed.

  More specifically, the measurement unit 28 acquires the high level and low level of the input optical signal received by the optical amplifier 21 from the output current of the light receiving element 31 received from the input detection unit 25, and the high level and low level of the optical signal. The level difference is calculated as the modulation amplitude of the input optical signal. The measurement unit 28 acquires the high level and time average output level of the optical signal received by the optical amplifier 21 from the output current of the light receiving element 31 received from the input detection unit 25, and the high level and time average of the optical signal. The modulation amplitude of the optical signal may be calculated from the output level. In addition, the measurement unit 28 acquires the low level and time average output level of the optical signal received by the optical amplifier 21 from the output current of the light receiving element 31 received from the input detection unit 25, and the low level and time average of the optical signal. The modulation amplitude of the optical signal may be calculated from the output level.

  The measuring unit 28 acquires the high level and low level of the output optical signal output from the optical amplifier 21 from the output current of the light receiving element 32 received from the output detection unit 27, and the high level and low level of the optical signal. Is calculated as the modulation amplitude of the output optical signal.

  Specifically, the measuring unit 28 calculates, for example, high-level and low-level peak hold values of the output currents of the light receiving element 31 and the light receiving element 32, respectively, or each of the light receiving element 31 and the light receiving element 32. By calculating the average value of the high level and the low level of the output current, the high level and the low level of each of the input optical signal and the output optical signal are obtained.

  Then, the measurement unit 28 calculates the modulation amplitude of each of the input optical signal and the output optical signal from the high level and low level of each of the acquired input optical signal and output optical signal. As described above, the measurement unit 28 may calculate the modulation amplitude of the optical signal from the high level and the time average output level of the optical signal, or may calculate the light from the low level and the time average output level of the optical signal. The modulation amplitude of the signal may be calculated. The measuring unit 28 divides the modulation amplitude of the output optical signal by the modulation amplitude of the input optical signal, and uses the obtained quotient as the gain of the modulation amplitude in the optical amplifier 21.

  FIG. 18 is a diagram illustrating a setting example of the gain of the modulation amplitude of the optical signal in the optical signal relay device according to the second embodiment of the present invention.

  Referring to FIG. 18, here, when the modulation amplitude of the optical signal received by the optical receiver is −28.5 dBm or more, the reception sensitivity of the optical receiver is improved. Specifically, the BER in the optical receiver is Is 10E-12, that is, less than 10 to the negative twelfth power. Further, it is assumed that the time average level of the optical signal received by the optical receiver is −20 dBm or more.

  When the upper limit of the distance from the optical signal repeater 101 to the optical receiver is 10 km, when the optical signal is attenuated by 25 dB at the maximum, the gain of the modulation amplitude of the output optical signal in the optical signal repeater 101 is set to 16.5 dB or more. To do. When the upper limit of the distance from the optical signal repeater 101 to the optical receiver is 20 km and the optical signal is attenuated by 30 dB at the maximum, the gain of the modulation amplitude of the output optical signal in the optical signal repeater 101 is 21.5 dB or more. Set to. Further, when the upper limit of the distance from the optical signal repeater 101 to the optical receiver is 30 km and the optical signal is attenuated by 35 dB at the maximum, the gain of the modulation amplitude of the output optical signal in the optical signal repeater 101 is 26.5 dB or more. Set to.

[Operation]
Next, the operation of the optical signal repeater in the optical communication system according to the second embodiment of the present invention will be described.

  Each device in the optical communication system 301 includes a computer, and an arithmetic processing unit such as a CPU in the computer reads and executes a program including a part or all of each step of the following flowchart from a memory (not shown). Each of the programs of the plurality of apparatuses can be installed from the outside. The programs of the plurality of apparatuses are distributed while being stored in a recording medium.

  FIG. 19 is a flowchart defining an example of an operation procedure when the optical signal repeater according to the second embodiment of the present invention controls the optical amplifier.

  Referring to FIG. 19, first, optical signal relay apparatus 101 measures the output current of each of the light receiving elements for monitoring, here light receiving elements 31 and 32 (step S31).

  Next, based on the measurement result, the optical signal relay apparatus 101 modulates the input optical signal, that is, the modulation amplitude of the optical signal received by the optical amplifier 21, and the output optical signal, that is, the modulation amplitude of the optical signal output from the optical amplifier 21. Is calculated. Then, the optical signal repeater 101 divides the modulation amplitude of the output optical signal by the modulation amplitude of the input optical signal, and sets the obtained quotient as the gain of the modulation amplitude (step S32).

  Next, when the gain of the calculated modulation amplitude is less than the predetermined threshold Th11 (YES in step S33), the optical signal relay apparatus 101 increases the drive current supplied to the optical amplifier 21 to increase the modulation of the optical signal. Drive control for increasing the gain of the amplitude is performed (step S34).

  On the other hand, when the gain of the calculated modulation amplitude is equal to or greater than the predetermined threshold Th11 (NO in step S33), the optical signal repeater 101 reduces the drive current supplied to the optical amplifier 21 to reduce the modulation amplitude of the optical signal. The drive control for reducing the gain is performed (step S35).

  The optical signal relay device 101 continuously or irregularly continues to measure the output currents of the light receiving element 31 and the light receiving element 32 (step S31).

[Modification 1]
When the modulation speed of the optical signal is low, the acquisition speed of the output currents of the light receiving element 31 and the light receiving element 32 in the measurement unit 28, that is, the acquisition speed of the high level and low level of the optical signal, By making the speed equal to the operation speed of the MPU that realizes all, it is possible to follow the change in the level of the optical signal.

  On the other hand, when the modulation speed of the optical signal is high, it is necessary to make the acquisition speed sufficiently higher than the operation speed.

  FIG. 20 is a diagram illustrating a configuration of a downlink signal relay unit in a modification of the optical signal relay device according to the second embodiment of the present invention.

  Referring to FIG. 20, downlink signal relay unit 12 includes optical amplifier 21, optical couplers 22 and 23, current supply unit 24, input detection unit 25, control unit 26, output detection unit 27, and measurement. Part 28 and CDR 30.

  The CDR 30 extracts the data and clock included in the optical signal from the output current of the light receiving element 31 received from the input detection unit 25, and outputs the extracted data and clock to the measurement unit 28.

  The measurement unit 28 performs measurement on the optical signal using the clock extracted by the CDR 30.

  More specifically, the measurement unit 28 includes an A / D converter. This A / D converter samples and holds the data received from the CDR 30 using the clock received from the CDR 30 as a trigger. The measurement unit 28 acquires the high level and low level of the optical signal from the sampled and held data. Note that the measurement unit 28 may include a circuit that adjusts the phase of the clock received from the CDR 30, and may acquire the high level and low level of the optical signal using the clock after the phase adjustment as a trigger.

  Further, the downlink signal relay unit 12 may include a CDR 29 instead of the CDR 30 as in the downlink signal relay unit according to the first embodiment.

  Here, when it takes time to adjust the phase of the clock in the measuring unit 28 as described above, first, control is performed so that the gain of the time average output level of the optical signal in the optical amplifier 21 becomes a predetermined value with a certain degree of accuracy. Then, after the phase adjustment is performed so as to obtain an accurate high level and low level of the optical signal, control is performed so that the modulation amplitude of the optical signal becomes a predetermined value. As a result, communication between the optical signal repeater 101 and the optical receiver can be started early without waiting for completion of the phase adjustment.

  FIG. 21 is a flowchart that defines an example of an operation procedure when the modification of the optical signal relay device according to the second embodiment of the present invention controls the optical amplifier.

  Before performing the drive control, the control unit 26 is based on the measurement result of the measurement unit 28 so that the gain of the average level per predetermined time of the optical signal output from the optical amplifier 21 becomes a predetermined value. Pre-drive control for adjusting the magnitude of the drive current supplied to 21 is performed.

  Specifically, referring to FIG. 21, first, the optical signal repeater 101 starts pre-drive control at a predetermined timing so that the gain of the time average output level of the optical signal in the optical amplifier 21 becomes a predetermined value. To do. Thereby, communication between the station-side apparatus 201 and the ONU 202 via the optical signal relay apparatus 101 is started (step S41).

  Next, the optical signal relay device 101 continues the pre-drive control until a predetermined time has elapsed from the predetermined timing (NO in step S42). While the pre-drive control is being performed, the clock phase adjustment in the measurement unit 28 is completed.

  Next, when a predetermined time elapses from the predetermined timing (YES in step S42), the optical signal repeater 101 measures the output current of the light receiving element 31 and the light receiving element 32 (step S43), and outputs the optical signal in the optical amplifier 21. Calculation of the gain of the modulation amplitude (step S44) and adjustment of the drive current supplied to the optical amplifier 21 are started (steps S45 to S47).

  The operations in steps S43 to S47 are the same as the operations in steps S31 to S35 shown in FIG.

[Modification 2]
As described above, the inventors of the present application pay attention to the point that the cross point is suitable as an index indicating the characteristics of the optical signal relay device, and have found a method for further improving the communication of the optical communication system.

  That is, in the optical signal repeater 101, the measuring unit 28 acquires the cross point of the optical signal output from the optical amplifier 21 and the cross point of the optical signal received by the optical amplifier 21. For example, the measurement unit 28 measures the high level, the low level, and the average level per predetermined time for the input optical signal and the output optical signal of the optical amplifier 21, and calculates each cross point using the measurement result.

  The control unit 26 corrects the adjustment content by the drive control based on the difference between the cross points acquired by the measurement unit 28.

  FIG. 22 is a diagram illustrating a setting example of the gain of the modulation amplitude of the optical signal in the modification of the optical signal relay device according to the second embodiment of the present invention.

  When the optical receiver receives an optical signal with an eye pattern in which the cross point difference, which is the difference between the cross points of the input optical signal and the output optical signal, is 20% or more, for example, the penalty of the receiving sensitivity of the optical receiver increases. Specifically, the reception quality of the optical signal in the optical receiver deteriorates, and for example, the graph shown in FIG. 9 shifts in parallel to the horizontal axis to the side with the large modulation amplitude. That is, the BER obtained with the same modulation amplitude is increased.

  For this reason, when the cross point difference becomes 20% or more, by reducing the modulation amplitude of the output optical signal, the cross point difference is made less than 20% to suppress the distortion of the waveform of the output optical signal, and the optical receiver Reduces reception sensitivity penalty. Thereby, degradation of communication quality can be suppressed.

  Specifically, referring to FIG. 22, control unit 26 sets, for example, a cross-point difference boundary value, for example, 20%, at which the reception sensitivity penalty of the optical receiver deteriorates to some extent, as cross-point threshold value Th12.

  When the cross point difference is the threshold Th12, that is, 20% or more, the control unit 26 increases the reception sensitivity penalty of the optical receiver from 0.5 dB so that the cross point difference becomes smaller than 20%. In addition, the modulation amplitude of the optical signal is reduced.

  On the other hand, when the cross point difference is less than the threshold Th12, that is, less than 20%, the control unit 26 maintains the modulation amplitude of the optical signal because the increase in the reception sensitivity penalty of the optical receiver remains within 0.5 dB. To do. In addition, when the cross point difference is less than the threshold Th12, the control unit 26 may increase the modulation amplitude of the optical signal so that the cross point difference becomes large with 20% as an upper limit.

  FIG. 23 is a flowchart defining an example of an operation procedure when the modification of the optical signal relay device according to the second embodiment of the present invention controls the optical amplifier.

  Referring to FIG. 23, the operations in steps S51 to S55 are the same as the operations in steps S31 to S35 shown in FIG.

  Next, the optical signal relay device 101 calculates each cross point of the input optical signal and the output optical signal based on the measurement result of the output current of each of the light receiving element 31 and the light receiving element 32. Specifically, the optical signal repeater 101 acquires the high level and the low level and the time average output level for each of the input optical signal and the output optical signal, and sets the midpoint of the modulation amplitude as a 50% cross point. The cross point is calculated based on the difference between the time average output level and the midpoint of the modulation amplitude. Then, the optical signal repeater 101 calculates the difference between the cross point of the input optical signal and the cross point of the output optical signal (step S56).

  Next, when the calculated cross point difference is larger than the predetermined threshold Th12 (YES in step S57), the optical signal repeater 101 reduces the drive current supplied to the optical amplifier 21 to reduce the modulation amplitude of the output optical signal. Is reduced (step S58).

  On the other hand, when the calculated cross point difference is equal to or smaller than the predetermined threshold Th12, the optical signal relay device 101 maintains the value of the drive current supplied to the optical amplifier 21 (NO in step S57).

  The optical signal relay device 101 continuously or irregularly continues to measure the output currents of the light receiving element 31 and the light receiving element 32 (step S51).

  Note that the control unit 26 is not limited to the configuration of acquiring each cross point of the input optical signal and the output optical signal, and acquires and acquires either the cross point of the input optical signal or the cross point of the output optical signal. The configuration may be such that the adjustment content by drive control is corrected based on the cross point.

  As described above, in the optical signal repeater according to the second embodiment of the present invention, the optical amplifier 21 receives, amplifies, and outputs an optical signal. The measurement unit 28 performs measurement related to the optical signal. Then, the control unit 26 adjusts the magnitude of the drive current supplied to the optical amplifier 21 based on the measurement result of the measurement unit 28 so that the gain of the modulation amplitude of the optical signal in the optical amplifier 21 becomes a predetermined value. The drive control is performed.

  As described above, in the optical signal repeater 101, the optical receiver receives the point that the modulation amplitude of the optical signal is suitable as an index indicating the characteristics of the optical signal repeater compared to the time average output level of the optical signal. When the modulation amplitude of the optical signal is the same, it is noted that the reception sensitivity of the optical receiver is the same value even when the time average output level of the optical signal is different, and the optical amplifier 21 does not depend on the reception intensity of the optical signal. The drive current to the optical amplifier 21 is controlled so that the gain of the modulation amplitude of the optical signal becomes a predetermined value.

  With such a configuration, it is possible to prevent a decrease in transmission quality and extend the communication limit distance from the optical signal repeater 101 to the optical receiver, for example, even in the saturation region of the optical amplifier 21, regardless of the reception intensity of the optical signal. it can. Further, unlike the technique described in Patent Document 1, it is not necessary to significantly reduce the intensity of input light to the optical amplifier, and an increase in power consumption in the optical amplifier accompanying an increase in gain of the optical amplifier can be prevented. .

  Therefore, in the optical signal repeater according to the second embodiment of the present invention, in the optical signal repeater that amplifies and transmits the received optical signal, the communication limit distance of the optical communication system is increased and the power consumption is suppressed. can do.

  Further, in the optical signal repeater according to the second embodiment of the present invention, in the optical signal repeater 101, the measurement unit 28 uses the cross point of the optical signal output from the optical amplifier 21 and the optical signal received by the optical amplifier 21. Get the cross point. And the control part 26 correct | amends the adjustment content by drive control based on the difference of each cross point acquired by the measurement part 28. FIG.

  As described above, for example, when the distortion of the waveform of the optical signal is detected from each cross point by the configuration of monitoring the cross point of the optical signal output from the optical amplifier 21 and the cross point of the optical signal received by the optical amplifier 21, Since the modulation amplitude of the optical signal can be reduced, deterioration in communication quality can be suppressed.

  In the optical signal repeater according to the second embodiment of the present invention, for example, the measurement unit 28 measures the high level of the optical signal and the low level of the optical signal for the input optical signal and the output optical signal. Or measuring the high level or low level of the optical signal and the average level of the optical signal per predetermined time, or the high level of the optical signal, the low level of the optical signal, and the predetermined level of the optical signal. Measure the average level per hour.

  With such a configuration, various characteristics such as the modulation amplitude and cross point of the optical signal repeater 101 can be easily obtained from the high level, low level and average level of the optical signal.

  In the optical signal repeater according to the second embodiment of the present invention, the CDR 30 extracts a clock from the optical signal. Then, the measurement unit 28 performs measurement related to the optical signal using the clock extracted by the CDR 30.

  With such a configuration, even when the modulation speed of the optical signal is high, it is possible to obtain a sufficient operation speed for acquiring various measured values of the optical signal.

  In the optical signal repeater according to the second embodiment of the present invention, the control unit 26 calculates the time average of the optical signal in the optical amplifier 21 based on the measurement result of the measurement unit 28 before performing the drive control. Pre-drive control for adjusting the magnitude of the drive current supplied to the optical amplifier 21 is performed so that the gain of the output level becomes a predetermined value.

  With such a configuration, even when time is required until an accurate measurement result is obtained in the measurement unit 28, the gain of the time average output level in the optical amplifier 21 is set to a predetermined value with a certain degree of accuracy. Control can be performed and communication between the optical signal repeater 101 and the optical receiver can be started early.

  Further, in the communication control method according to the second embodiment of the present invention, first, a measurement relating to an optical signal is performed. Next, based on the measurement result, drive control is performed to adjust the magnitude of the drive current supplied to the optical amplifier 21 so that the gain of the modulation amplitude of the optical signal in the optical amplifier 21 becomes a predetermined value.

  As described above, in the optical signal repeater 101, the optical receiver receives the point that the modulation amplitude of the optical signal is suitable as an index indicating the characteristics of the optical signal repeater compared to the time average output level of the optical signal. When the modulation amplitude of the optical signal is the same, it is noted that the reception sensitivity of the optical receiver is the same value even when the time average output level of the optical signal is different, and the optical amplifier 21 does not depend on the reception intensity of the optical signal. The drive current to the optical amplifier 21 is controlled so that the gain of the modulation amplitude of the optical signal becomes a predetermined value.

  Accordingly, it is possible to prevent the transmission quality from being lowered and to extend the communication limit distance from the optical signal repeater 101 to the optical receiver, for example, even in the saturation region of the optical amplifier 21, regardless of the reception intensity of the optical signal. Further, unlike the technique described in Patent Document 1, it is not necessary to significantly reduce the intensity of input light to the optical amplifier, and an increase in power consumption in the optical amplifier accompanying an increase in gain of the optical amplifier can be prevented. .

  Therefore, in the communication control method according to the second embodiment of the present invention, in the optical signal repeater that amplifies and transmits the received optical signal, the communication limit distance of the optical communication system is increased and the power consumption is suppressed. be able to.

  In the optical communication system according to the second embodiment of the present invention, the optical signal repeater 101 is configured to include the control unit 26 and the measurement unit 28. However, the present invention is not limited to this. A device other than the optical signal repeater 101 in the optical communication system 301 includes a control unit 26 and a measurement unit 28, and monitors input / output light of the optical amplifier and controls drive current to the optical amplifier. Also good.

  In the optical communication system according to the second embodiment of the present invention, the configuration is such that the input / output light of the optical amplifier and the drive current to the optical amplifier are monitored in the downstream direction. However, it is also possible to adopt a configuration in which the input / output light of the optical amplifier and the drive current to the optical amplifier are monitored in the upstream direction, as in the downstream direction.

  Since other configurations and operations are the same as those of the optical communication system according to the first embodiment, detailed description thereof will not be repeated here.

  Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

<Third Embodiment>
The present embodiment relates to an optical communication system in which the control reference of the optical amplifier is changed as compared with the optical communication system according to the first embodiment. The contents other than those described below are the same as those of the optical communication system according to the first embodiment.

  FIG. 24 is a diagram illustrating an example of the relationship between the reception level and the reception sensitivity in the optical receiver. In FIG. 24, the horizontal axis indicates the time average input level of the optical receiver, that is, the average of the optical signal reception level per predetermined time, and the vertical axis indicates the BER corresponding to the reception sensitivity. Graphs G31 to G32 show cases where the extinction ratios of the optical signals are 9 dB and 12 dB, respectively.

  Referring to FIG. 24, the reception sensitivity of the optical receiver, that is, the BER with respect to the time average input level varies depending on the extinction ratio of the optical signal. That is, even if the time average input level of the optical signal in the optical receiver is the same, if the extinction ratio of the optical signal is different, the reception sensitivity of the optical receiver has a different value. Specifically, when the extinction ratio of the optical signal decreases, the reception sensitivity of the optical receiver deteriorates.

  FIG. 25 is a diagram illustrating an example of an eye pattern of an optical signal received by the optical amplifier in a state where there is no secular change. FIG. 26 is a diagram showing an example of an eye pattern of an optical signal that has changed over time received by the optical amplifier. 25 and 26, the horizontal axis indicates time, and the vertical axis indicates the optical output level of the optical amplifier. W11 shows an eye pattern in a state without aging, and W12 shows an eye pattern in a state with aging.

  Referring to FIG. 25 and FIG. 26, the eye pattern W12 of the optical signal that has changed over time has a waveform distortion compared to the eye pattern W11 that has not changed over time. That is, when the optical signal received by the optical amplifier has changed over time, the high level of the optical output becomes small. Specifically, the high level P1d of the optical output having the secular change is smaller than the high level P1 of the optical output having no secular change.

  More specifically, the extinction ratio, which is the ratio between the high level of the optical output and the low level of the optical output, changes from P1 / P0 to P1d / P0d due to aging, and the time average output level becomes (P1-P0) / 2 changes to (P1d−P0d) / 2, and the cross point changes from Xp to Xpd.

  That is, due to the aging of the optical signal, the extinction ratio decreases from P1 / P0 to P1d / P0d, and the reception sensitivity of the optical receiver deteriorates.

  In an optical communication system that performs communication between an optical transmitter and an optical receiver via an optical signal repeater, the time average output level of the optical signal from the optical transmitter is, for example, ALC (auto level control) or time average It is controlled by AGC (Auto Gain Control) that controls the gain of the time average output level with respect to the input level to be constant.

  In such an optical communication system, the extinction ratio of the optical transmitter is not monitored, and there is a problem that the communication limit distance from the optical signal repeater to the optical receiver varies due to the fluctuation of the extinction ratio of the optical signal.

  The inventors of the present application have found a problem relating to such an extinction ratio of an optical signal and a solution to the problem. That is, in the optical signal repeater according to the third embodiment of the present invention, the time average output level of the optical signal transmitted to the optical receiver based on the extinction ratio of the optical signal received by the optical signal repeater 101. More specifically, the drive current to the optical amplifier is controlled.

  That is, the measurement unit 28 acquires the extinction ratio of the optical signal received by the optical amplifier 21. For example, the measurement unit 28 measures the high level of the optical signal received by the optical amplifier 21 and the low level of the optical signal, and calculates the extinction ratio using the measurement result. Then, the control unit 26 performs drive control for adjusting the magnitude of the drive current supplied to the optical amplifier 21 based on the extinction ratio acquired by the measurement unit 28.

  FIG. 27 is a diagram illustrating a setting example of the time average output level of the optical signal when the extinction ratio of the input optical signal is relatively small in the optical signal relay device according to the third embodiment of the present invention.

  Referring to FIG. 27, here, it is assumed that the extinction ratio of the optical signal received by optical signal relay apparatus 101 is between 9 dB and 12 dB. For this reason, when the time average level of the optical signal received by the optical receiver is −30 dBm, the reception sensitivity of the optical receiver is good. Specifically, the BER in the optical receiver is 10E-12, that is, minus 12 of 10. Suppose that it is less than the power.

  When the upper limit of the distance from the optical signal repeater 101 to the optical receiver is 10 km and the optical signal is attenuated by 25 dB at the maximum, the time average output level of the optical signal transmitted from the optical signal repeater 101 is set to -5 dBm or more. To do. When the upper limit of the distance from the optical signal repeater 101 to the optical receiver is 20 km and the optical signal is attenuated by 30 dB at the maximum, the time average output level of the optical signal transmitted from the optical signal repeater 101 is 0 dBm or more. Set. When the upper limit of the distance from the optical signal repeater 101 to the optical receiver is 30 km and the optical signal is attenuated by 35 dB at the maximum, the time average output level of the optical signal transmitted from the optical signal repeater 101 is +5 dBm or more. Set.

  FIG. 28 is a diagram illustrating a setting example of the time average output level of the optical signal when the extinction ratio of the input optical signal is relatively large in the optical signal relay device according to the third embodiment of the present invention.

  Referring to FIG. 28, here, it is assumed that the extinction ratio of the optical signal received by optical signal relay apparatus 101 is a value larger than 12 dB. For this reason, when the time average level of the optical signal received by the optical receiver is −31 dBm, the reception sensitivity of the optical receiver is good. Specifically, the BER in the optical receiver is 10E-12, that is, minus 12 of 10. Suppose that it is less than the power.

  When the upper limit of the distance from the optical signal repeater 101 to the optical receiver is 10 km and the optical signal is attenuated by 25 dB at the maximum, the time average output level of the optical signal transmitted from the optical signal repeater 101 is set to -6 dBm or more. To do. When the upper limit of the distance from the optical signal repeater 101 to the optical receiver is 20 km, when the optical signal is attenuated by 30 dB at the maximum, the time average output level of the optical signal transmitted from the optical signal repeater 101 is −1 dBm or more. Set to. Further, when the upper limit of the distance from the optical signal repeater 101 to the optical receiver is 30 km and the optical signal is attenuated by 35 dB at the maximum, the time average output level of the optical signal transmitted from the optical signal repeater 101 is +4 dBm or more. Set.

  As described above, the optical signal repeater 101 according to the first embodiment for controlling the modulation amplitude and the gain of the modulation amplitude by controlling the time average output level of the output optical signal based on the extinction ratio of the input optical signal. An effect equivalent to that of the optical signal repeater 101 according to the second embodiment for controlling the optical signal can be obtained.

[Operation]
Next, the operation of the optical signal repeater in the optical communication system according to the third embodiment of the present invention will be described.

  Each device in the optical communication system 301 includes a computer, and an arithmetic processing unit such as a CPU in the computer reads and executes a program including a part or all of each step of the following flowchart from a memory (not shown). Each of the programs of the plurality of apparatuses can be installed from the outside. The programs of the plurality of apparatuses are distributed while being stored in a recording medium.

  FIG. 29 is a flowchart defining an example of an operation procedure when the optical signal repeater according to the third embodiment of the present invention controls the optical amplifier.

  Referring to FIG. 29, first, the optical signal relay apparatus 101 measures the output current of the monitoring light receiving element, here the light receiving element 31 (step S61).

  Next, the optical signal repeater 101 calculates the extinction ratio of the input optical signal, that is, the optical signal received by the optical amplifier 21 based on the measurement result (step S62).

  Next, when the calculated extinction ratio is less than the predetermined threshold Th21 (YES in step S63), the optical signal repeater 101 increases the drive current supplied to the optical amplifier 21 to increase the time average output of the optical signal. Drive control for increasing the level is performed (step S64).

  On the other hand, when the calculated extinction ratio is equal to or greater than the predetermined threshold Th21 (NO in step S63), the optical signal repeater 101 reduces the drive current supplied to the optical amplifier 21 to reduce the time average output level of the optical signal. Drive control is performed to reduce the value (step S65).

  The optical signal relay device 101 continuously or irregularly measures the output current of the light receiving element 31 (step S61).

[Modification]
If the high level of the optical output is 100% and the low level of the optical output is 0%, when the cross point is deviated from 50%, it indicates that the optical signal received by the optical amplifier has changed over time.

  FIG. 30 is a diagram illustrating an example of an eye pattern of an optical signal received by the optical amplifier in a state where there is no secular change. The way of viewing the figure is the same as in FIG.

  Referring to FIG. 30, when the optical signal received by the optical amplifier has not changed over time, when the high level P1 of the optical output is 100% and the low level P0 of the optical output is 0%, the cross point Xp is 50%. It becomes. Further, the actually measured value of the time average output level and the calculated value (P1−P0) / 2 at the midpoint of the modulation amplitude are equivalent values.

  FIG. 31 is a diagram illustrating an example of an eye pattern of an optical signal that has changed over time received by the optical amplifier. The way of viewing the figure is the same as in FIG.

  Referring to FIG. 31, when the optical signal received by the optical amplifier has changed over time, the high level of the optical output becomes small. Specifically, the high level P1d of the optical output having the secular change is smaller than the high level P1 of the optical output having no secular change.

  The time average input level is a time integration value of the high level of the optical output and the low level of the optical output. Therefore, when the high level P1d of the optical output is 100% and the low level P0d of the optical output is 0%, the cross point Will not be 50%. Further, the actually measured value of the time average output level and the calculated value (P1d−P0d) / 2 at the midpoint of the modulation amplitude are different values.

  Thus, when the optical signal received by the optical amplifier has changed over time, the waveform of the eye pattern is distorted and the cross point becomes large.

  As shown in FIGS. 30 and 31, the inventors of the present application pay attention to the point that the cross point is suitable as an index indicating the characteristics of the secular change of the optical signal transmitted from the optical transmitter. I found a way to make communication better.

  As described with reference to FIG. 16, when the optical receiver receives an optical signal having an eye pattern with a cross point of 70% or more, for example, the penalty of the reception sensitivity of the optical receiver increases. The reception quality of the optical signal in the optical receiver deteriorates, and for example, the graph shown in FIG. That is, the BER obtained with the same modulation amplitude is increased.

  For this reason, when the cross point becomes larger than 60%, for example, the optical signal repeater 101 determines that the input optical signal is abnormal and notifies it.

  That is, the measurement unit 28 acquires the cross point of the optical signal received by the optical amplifier 21. For example, the measurement unit 28 measures the high level of the optical signal received by the optical amplifier 21, the low level of the optical signal, and the average level of the optical signal per predetermined time, and calculates the cross point using the measurement result. To do.

  The control unit 26 detects an abnormality based on the cross point acquired by the measurement unit 28.

  Further, as described above, when the extinction ratio becomes small, the reception sensitivity of the optical receiver deteriorates. Therefore, for example, when the optical signal repeater 101 cannot sufficiently suppress the deterioration of the reception sensitivity of the optical receiver due to the decrease in the extinction ratio even if the time average output level of the optical signal is increased, specifically, When the extinction ratio is less than 9 dB, for example, it is determined that the input optical signal is abnormal and notified.

  That is, the measurement unit 28 acquires the extinction ratio of the optical signal received by the optical amplifier 21. Then, the control unit 26 detects an abnormality based on the extinction ratio acquired by the measurement unit 28.

  FIG. 32 is a flowchart defining an example of an operation procedure when the modification of the optical signal relay device according to the third embodiment of the present invention controls the optical amplifier.

  Referring to FIG. 32, the operations in steps S71 to S72 are the same as the operations in steps S61 to S62 shown in FIG.

  Next, when the calculated extinction ratio is equal to or less than the predetermined threshold Th22 (NO in step S73), the optical signal relay apparatus 101 notifies an abnormality of the input optical signal (step S74). However, threshold Th22 <threshold Th21.

  On the other hand, when the calculated extinction ratio is greater than the predetermined threshold Th22 (YES in step S73) and is less than the predetermined threshold Th21 (YES in step S75), the optical signal repeater 101 transmits to the optical amplifier 21. Drive control is performed to increase the time average output level of the optical signal by increasing the supplied drive current (step S76).

  On the other hand, when the calculated extinction ratio is greater than the predetermined threshold Th22 (YES in step S73) and is equal to or greater than the predetermined threshold Th21 (NO in step S75), the optical signal repeater 101 sends an optical amplifier 21 to the optical amplifier 21. Drive control is performed to reduce the time average output level of the optical signal by reducing the supplied drive current (step S77).

  Next, the optical signal repeater 101 calculates a cross point of the input optical signal based on the measurement result. Specifically, the optical signal repeater 101 acquires the high level and low level of the optical signal and the time average output level, and uses the midpoint of the modulation amplitude as a 50% cross point to modulate the time average output level and the modulation. A cross point is calculated based on the difference from the midpoint of the amplitude (step S78).

  Next, when the calculated cross point is larger than the predetermined threshold Th23 (YES in step S79), the optical signal relay apparatus 101 notifies an abnormality of the input optical signal (step S80).

  The optical signal relay device 101 continuously or irregularly measures the output current of the light receiving element 31 (step S71).

  Note that, in the optical signal relay device according to the third embodiment of the present invention, the first and second modifications of the optical signal relay device according to the first embodiment or the second embodiment of the present invention. It is also possible to adopt a configuration.

  In addition, in the optical signal repeater according to the first embodiment and the second embodiment of the present invention, a configuration that performs abnormality detection based on the crosspoint or the extinction ratio according to the third embodiment is adopted. Is also possible.

  As described above, in the optical signal repeater according to the third embodiment of the present invention, the optical amplifier 21 receives, amplifies, and outputs an optical signal. The measurement unit 28 performs measurement related to the optical signal. The measuring unit 28 acquires the extinction ratio of the optical signal received by the optical amplifier 21. Then, the control unit 26 performs drive control for adjusting the magnitude of the drive current supplied to the optical amplifier 21 based on the extinction ratio acquired by the measurement unit 28.

  Thus, paying attention to the change in the extinction ratio due to the secular change of the optical signal from the optical transmitter, the extinction ratio of the optical signal received by the optical amplifier 21 is monitored, and the optical amplifier 21 is supplied to the optical amplifier 21 based on the extinction ratio. The configuration for controlling the drive current prevents the transmission quality from deteriorating and extends the communication limit distance from the optical signal repeater 101 to the optical receiver, for example, even in the saturation region of the optical amplifier 21, regardless of the reception intensity of the optical signal. be able to. Further, unlike the technique described in Patent Document 1, it is not necessary to significantly reduce the intensity of input light to the optical amplifier, and an increase in power consumption in the optical amplifier accompanying an increase in gain of the optical amplifier can be prevented. .

  Therefore, in the optical signal repeater according to the third embodiment of the present invention, in the optical signal repeater that amplifies and transmits the received optical signal, the communication limit distance of the optical communication system is increased and the power consumption is suppressed. can do.

  In the optical signal repeater according to the third embodiment of the present invention, the measurement unit 28 acquires the cross point or extinction ratio of the optical signal received by the optical amplifier 21. Then, the control unit 26 detects an abnormality based on the cross point or the extinction ratio acquired by the measurement unit 28.

  In this way, by monitoring the cross point or extinction ratio of the optical signal and detecting an abnormality, for example, maintenance and replacement of the optical transmitter can be performed at an early stage, thereby avoiding an unexpected communication failure in the optical communication system. be able to.

  In the optical signal repeater according to the third embodiment of the present invention, the measuring unit 28 measures the high level of the optical signal and the low level of the optical signal for the input optical signal, or the optical signal The high level or low level of the optical signal and the average level of the optical signal per predetermined time, or the high level of the optical signal, the low level of the optical signal, and the average level of the optical signal per predetermined time Measure.

  With such a configuration, various characteristics such as the modulation amplitude, cross point, and extinction ratio of the optical signal repeater 101 can be easily obtained from the high level, low level, and average level of the optical signal.

  Further, in the communication control method according to the third embodiment of the present invention, first, a measurement relating to an optical signal is performed. Next, drive control is performed to adjust the magnitude of the drive current supplied to the optical amplifier 21 based on the extinction ratio of the optical signal received by the optical amplifier 21 obtained by the measurement.

  Thus, paying attention to the change in the extinction ratio due to the secular change of the optical signal from the optical transmitter, the extinction ratio of the optical signal received by the optical amplifier 21 is monitored, and the optical amplifier 21 is supplied to the optical amplifier 21 based on the extinction ratio. By controlling the drive current, the transmission quality is prevented from being lowered and the communication limit distance from the optical signal repeater 101 to the optical receiver is extended, for example, even in the saturation region of the optical amplifier 21, regardless of the reception intensity of the optical signal. be able to. Further, unlike the technique described in Patent Document 1, it is not necessary to significantly reduce the intensity of input light to the optical amplifier, and an increase in power consumption in the optical amplifier accompanying an increase in gain of the optical amplifier can be prevented. .

  Therefore, in the communication control method according to the third embodiment of the present invention, in the optical signal repeater that amplifies and transmits the received optical signal, the communication limit distance of the optical communication system is increased and the power consumption is suppressed. be able to.

  In the optical communication system according to the third embodiment of the present invention, the optical signal repeater 101 is configured to include the control unit 26 and the measurement unit 28. However, the configuration is not limited thereto. Even if the device other than the optical signal repeater 101 in the optical communication system 301 includes the control unit 26 and the measurement unit 28, the input light of the optical amplifier is monitored and the drive current to the optical amplifier is controlled. Good.

  Further, in the optical communication system according to the third embodiment of the present invention, the configuration is such that the input light of the optical amplifier is monitored and the drive current to the optical amplifier is performed in the downstream direction. Instead of this, it is also possible to adopt a configuration in which the input light of the optical amplifier is monitored and the drive current to the optical amplifier is monitored in the upstream direction as in the downstream direction.

  Since other configurations and operations are the same as those of the optical communication system according to the first embodiment, detailed description thereof will not be repeated here.

  In the optical signal repeater according to the first to third embodiments of the present invention, the control unit 26 performs drive control for adjusting the magnitude of the drive current supplied to the optical amplifier 21. Although it is the configuration, it is not limited to this. The control unit 26 may be configured to perform drive control that adjusts the magnitude of the drive voltage supplied to the optical amplifier 21 according to the type of the optical amplifier 21 and the like.

  The above embodiment should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The above description includes the following features.

[Appendix 1]
An optical signal repeater that receives and amplifies an optical signal having a level corresponding to a logical value of data to be transmitted, and transmits the amplified optical signal,
An optical amplifier that receives and amplifies and outputs the optical signal;
A measurement unit for measuring the optical signal;
Drive that adjusts the magnitude of the drive current or drive voltage supplied to the optical amplifier based on the measurement result of the measurement unit so that the modulation amplitude of the optical signal output from the optical amplifier becomes a predetermined value A control unit for performing control,
The optical signal repeater is used in a PON,
The optical signal relay device, wherein the optical signal is a downstream optical signal transmitted from the station side device to the home side device.

DESCRIPTION OF SYMBOLS 11 Electrical / optical converter 12 Downstream signal relay part 13 Optical / electrical converter 14 Upstream signal reproduction | regeneration part 21 Optical amplifier 22, 23 Optical coupler 24 Current supply part 25 Input detection part 26 Control part 27 Output detection part 28 Measurement part 30 CDR
101 Optical signal repeater 201 Station side device 202 ONU
211, 212 Optical coupler 301 Optical communication system

Claims (9)

An optical signal repeater that receives and amplifies an optical signal having a level corresponding to a logical value of data to be transmitted, and transmits the amplified optical signal,
An optical amplifier that receives and amplifies and outputs the optical signal;
A measurement unit for measuring the optical signal;
Drive that adjusts the magnitude of the drive current or drive voltage supplied to the optical amplifier based on the measurement result of the measurement unit so that the modulation amplitude of the optical signal output from the optical amplifier becomes a predetermined value for example Bei and a control unit for performing control,
The measurement unit obtains at least one of a cross point of the optical signal output by the optical amplifier and a cross point of the optical signal received by the optical amplifier,
The said control part is an optical signal relay apparatus which correct | amends the adjustment content by the said drive control based on the said cross point acquired by the said measurement part . An optical signal repeater that receives and amplifies an optical signal having a level corresponding to a logical value of data to be transmitted, and transmits the amplified optical signal,
An optical amplifier that receives and amplifies and outputs the optical signal;
A measurement unit for measuring the optical signal;
Drive control that adjusts the magnitude of the drive current or drive voltage supplied to the optical amplifier so that the gain of the modulation amplitude of the optical signal in the optical amplifier becomes a predetermined value based on the measurement result of the measurement unit Bei example and a control unit that performs,
The measurement unit obtains at least one of a cross point of the optical signal output by the optical amplifier and a cross point of the optical signal received by the optical amplifier,
The said control part is an optical signal relay apparatus which correct | amends the adjustment content by the said drive control based on the said cross point acquired by the said measurement part . An optical signal repeater that receives and amplifies an optical signal having a level corresponding to a logical value of data to be transmitted, and transmits the amplified optical signal,
An optical amplifier that receives and amplifies and outputs the optical signal;
A measurement unit for measuring the optical signal,
The measurement unit obtains an extinction ratio of the optical signal received by the optical amplifier,
The optical signal relay device further includes:
An optical signal relay apparatus comprising: a control unit that performs drive control for adjusting a magnitude of a drive current or a drive voltage supplied to the optical amplifier based on the extinction ratio acquired by the measurement unit. The measurement unit obtains at least one of a cross point of the optical signal output by the optical amplifier and a cross point of the optical signal received by the optical amplifier,
The optical signal relay device according to claim 3 , wherein the control unit corrects the adjustment content by the drive control based on the cross point acquired by the measurement unit. The measuring unit measures the high level of the optical signal and the low level of the optical signal, or measures the high level or low level of the optical signal and the average level of the optical signal per predetermined time, or 5. The light according to claim 1 , wherein a high level of the optical signal, a low level of the optical signal, and an average level per predetermined time of the optical signal are measured. Signal relay device . The control unit, before performing the drive control, based on the measurement result of the measurement unit, so that the average level per predetermined time of the optical signal output from the optical amplifier becomes a predetermined value, or as the gain of the mean level of the optical amplifier becomes a predetermined value, it performs the pre-drive control for adjusting the magnitude of the driving current or the driving voltage is supplied to the optical amplifier, one of claims 1 to 5 2. An optical signal relay device according to item 1. The measurement unit obtains a cross point or an extinction ratio of the optical signal received by the optical amplifier,
Wherein the control unit detects the abnormality based on the cross point or the extinction ratio obtained by the measurement unit, the optical signal relay device according to any one of claims 1 to 6. A communication control method for receiving and amplifying an optical signal having a level corresponding to a logical value of data to be transmitted and controlling an optical signal repeater that transmits the amplified optical signal,
The optical signal repeater includes an optical amplifier that receives, amplifies, and outputs the optical signal,
The communication control method includes:
Performing measurements on the optical signal;
Based on the result of the measurement, the modulation amplitude of the optical signal output from the optical amplifier becomes a predetermined value , or the gain of the modulation amplitude of the optical signal in the optical amplifier becomes a predetermined value. and performing a drive control for adjusting the magnitude of the driving current or the driving voltage is supplied before Symbol optical amplifier,
Obtaining at least one of a cross point of the optical signal output by the optical amplifier and a cross point of the optical signal received by the optical amplifier;
Correcting the adjustment content by the drive control based on the acquired cross point . A communication control method for receiving and amplifying an optical signal having a level corresponding to a logical value of data to be transmitted and controlling an optical signal repeater that transmits the amplified optical signal,
The optical signal repeater includes an optical amplifier that receives, amplifies, and outputs the optical signal,
The communication control method includes:
Performing measurements on the optical signal ;
Based on the extinction ratio of the optical signal is the optical amplifier obtained experienced by prior Symbol measure, and a step of performing a drive control for adjusting the magnitude of the driving current or the driving voltage is supplied to the optical amplifier, communication Control method.

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