JP2012151739A - Optical communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform proper automatic adjustment of an output light level of an optical module of an interface board and an optical module of an optical network unit without inserting an optical attenuator, relating to an optical communication device.SOLUTION: An optical communication device comprises: an optical line terminal having one or a plurality of interface boards and one supervisory control part for supervising and controlling the interface boards; at least one optical network unit connected to the interface board; and means for automatically adjust an output light level of an optical module of the interface board by measuring a light reception level at the optical network unit by means of transmission/reception of an optical signal between the optical network unit and the interface board.

Description

  The present invention relates to an optical communication apparatus, for example, a configuration for adjusting the output optical level of an optical module of an interface board and an optical module of a subscriber-side line terminator without inserting an optical attenuator.

  Currently, a GE-PON (Gigabit Ethernet (registered trademark) -Passive Optical Network) system is known as a subscriber optical fiber network system for subscriber homes such as general homes.

  In this GE-PON system, one optical line terminal (OLT) and multiple optical line units (ONU) are connected using an optical fiber cable and an optical star coupler or optical splitter. ) Are connected, and bidirectional communication is performed between the station-side line terminator (OLT) and the subscriber-side line terminator (ONU) at a communication speed in units of Gbit / s.

  FIG. 8 is a system configuration diagram of a conventional GE-PON system, in which a station-side line terminator 50 and a plurality of subscriber-side line terminators 60 are connected via a backbone optical fiber 71, an optical star coupler 72, and a branch optical fiber 73. It is connected. The station-side line termination device 50 includes a plurality of interface boards 51 and a monitoring control unit 56.

  FIG. 9 is a block diagram of a conventional GE-PON system, and each interface board 51 includes an optical module 52, an ASIC (Application Specific IC) 53, and an FPGA (Field Programmable Gate Array) 54. The monitoring control unit 56 includes an MPU (Micro-Processing Unit) 57 and an FPGA 58. On the other hand, the subscriber line terminating device 60 includes an optical module 61 and an ASIC 62.

  The output level of the optical module 52 mounted on each interface board 51 is fixed, and an optical attenuator 59 is attached according to the distance between the subscriber-side line terminator 60 and the interface board 51, so that the subscriber side The light reception level at the line termination device 60 is lowered to prevent an optical module from being damaged due to an excessive light reception level (see, for example, Patent Document 1).

  That is, in the prior art, even when the number of subscriber-side line terminators 60 connected to the interface board 51 is small or the connection distance is short and the like, a strong output light level is not required and the light is output at a fixed light level. Therefore, there is a possibility that the light reception level of the interface board 51 and the subscriber-side line terminator 60 to the optical module 61 is too high, causing the optical module to fail.

  For this reason, the builder measures the light level and attaches the optical attenuator 59 to the interface board 51 to attenuate the light, and the optical module 52 of the interface board 51 and the optical module 61 of the subscriber-side line termination device 60 fail. I try not to. An optical module capable of measuring the input / output level is also known (see, for example, Patent Document 2).

JP 2009-200353 A JP 2008-236612 A

  However, when the builder measures the light level and attaches the optical attenuator to the interface board, the construction work becomes complicated and the number of parts increases by the amount of the optical attenuator, making it difficult to reduce the cost. is there.

  In addition, since the light output level is fixed, the power is always output at a strong light level so that communication with the farthest subscriber line termination device is possible. There is also a problem.

  Accordingly, an object of the present invention is to appropriately and automatically adjust the output optical levels of the optical module of the interface board and the optical module of the subscriber-side line terminator without inserting an optical attenuator.

  According to one aspect of the disclosure, a station-side line terminating device including one or a plurality of interface boards and a monitoring control unit that monitors and controls the interface boards, and at least one subscriber connected to the interface boards The optical level of the output from the optical module of the interface board by the transmission / reception of the optical signal between the side line terminator and the subscriber side line terminator and the interface board By measuring the above, there is provided an optical communication device comprising means for automatically adjusting the output light level of the optical module of the interface board.

  From another viewpoint to be disclosed, at least one interface board provided with one or a plurality of interface boards and one monitoring control unit for monitoring and controlling the interface boards, and at least one connected to the interface board. The optical level of the output from the optical module of the subscriber-side line terminator is determined by the interface board by transmitting and receiving optical signals between the two subscriber-side line terminators and the subscriber-side line terminator and the interface board. By measuring the received light level, there is provided an optical communication device comprising means for automatically adjusting the output light level of the optical module of the subscriber line terminating device.

  According to the disclosed optical communication apparatus, it is possible to automatically and appropriately adjust the output optical levels of the optical module of the interface board and the optical module of the subscriber-side line termination apparatus without inserting an optical attenuator.

1 is a system configuration diagram of an optical communication apparatus having a function of automatically adjusting an output light level of an optical module according to an embodiment of the present invention. It is a block diagram of the optical communication apparatus provided with the function to adjust automatically the output light level of the optical module of embodiment of this invention. It is a block diagram which shows an example of the optical module 20 of embodiment of this invention. It is explanatory drawing of the sequence of the automatic adjustment of the output light level of the optical module of embodiment of this invention. It is explanatory drawing of the automatic adjustment sequence of the output light level at the time of the interface board initial startup of Example 1 of this invention. It is explanatory drawing of the automatic readjustment sequence of the output light level at the time of operation | use of Example 2 of this invention. It is explanatory drawing of the automatic adjustment sequence of the output light level at the time of the new connection of the subscriber side line termination apparatus of Example 3 of this invention. It is a system block diagram of the conventional GE-PON system. It is a block diagram of the conventional GE-PON system.

  Here, an optical communication device having a function of automatically adjusting the output light level of the optical module according to the embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a system configuration diagram of an optical communication apparatus having a function of automatically adjusting an output optical level of an optical module according to an embodiment of the present invention, which includes a station-side line terminator 10 and a plurality of subscriber-side line terminators. 30 are connected via a backbone optical fiber 41, an optical star coupler 42, and a branch optical fiber 43.

  FIG. 2 is a block diagram of an optical communication apparatus having a function of automatically adjusting the output optical level of the optical module according to the embodiment of the present invention. The station side line termination apparatus 10 includes a plurality of interface boards 11 and a supervisory control. Each interface board 11 includes an optical module 20 and an ASIC 12 that controls and monitors the operation of the optical module 20. Each interface board 11 includes an FPGA as in the conventional case, but is omitted because it is not directly related to the present invention. The monitoring control unit 16 includes the MPU 17 and the FPGA for controlling and monitoring the communication device, but the FPGA is not directly related to the present invention, and is omitted.

  FIG. 3 is a configuration diagram showing an example of the optical module 20 according to the embodiment of the present invention. A WDM (Wavelength Division Multiplexing) filter 21, an avalanche photodiode (APD) 22, a preamplifier (TIA: Trans Impedance). Amplifier) 23, amplifier 24, optical isolator 25, semiconductor laser 26, monitor photodiode 27, and drive circuit 28.

  The optical input from the branch optical fiber 43 is converted into an electrical signal by the avalanche photodiode 22 through the WDM filter 21, amplified by the preamplifier 23 and the amplifier 24, and output as data.

  On the other hand, the transmission data is applied to the semiconductor laser 26 as an electrical signal by the drive circuit 28 and is sent as an optical signal from the WDM filter 21 to the branch optical fiber 43 via the optical isolator 25. Further, the monitor light from the semiconductor laser is received by the monitoring photodiode 27 and the output is fed back to the drive circuit 28 to control the output light level of the semiconductor laser 26 so as to maintain a preset value.

  On the other hand, the subscriber line terminating device 30 includes an optical module 31 and an ASIC 32. The basic configuration of the optical module 31 is the same as that of the optical module 20 shown in FIG.

  FIG. 4 is an explanatory diagram of a sequence of automatic adjustment of the output light level of the optical module according to the embodiment of the present invention. The handshake at the time of establishing the connection between the interface board and the subscriber-side line terminator, Communication, or when a new subscriber-side line terminator is connected, the optical level necessary and sufficient for optical communication over that connection is measured and output from the interface board and the subscriber-side line terminator Adjust the light level.

a. First, an ONU that receives an optical signal transmitted from the optical module of the interface board (IF) by the APD transmits a response signal from the semiconductor laser in response to the signal, thereby establishing signal detection.
b. Next, a signal detection notification is sent from the IF to the monitoring control unit.
c. Next, a command to start adjustment of the output light level of the IF optical module and the output light level of the ONU optical module is commanded from the MPU of the monitoring controller.
d. Then, based on the command, the IF transmits a signal to that effect to the ONU by the optical output of the initial level intensity of the IF semiconductor laser, and requests the ONU light reception level and output level.
e. Next, the optical signal from the IF is detected by the APD of the optical module of the ONU, and the output is output to the ASIC. The ASIC transmits the information about the received light level to the optical signal of the initial level intensity of the semiconductor laser of the optical module of the ONU. By transmitting to the IF, the ONU light reception level response and the output level response are executed.
f. Next, the APD of the IF optical module detects this optical signal, and the IF determines whether the output light level of the semiconductor laser of the IF optical module is within an appropriate range based on the received light level information in the optical signal. Judgment is made by the provided ASIC. At the same time, the ASIC provided in the IF determines whether the output level of the semiconductor laser of the ONU optical module is within an appropriate range based on the light receiving level of the APD of the IF optical module. If it is not in the proper range, an ASIC provided for the IF or ONU sends a control signal to the drive circuit of the optical module, and the drive circuit controls the drive voltage to each semiconductor laser so that the output light level of each semiconductor laser is appropriate. Repeat the exchange of optical signals until. The drive voltage value when the output light level becomes appropriate is stored in each ASIC.
g. Next, when the output light level of each semiconductor laser becomes appropriate, an output light level adjustment end response is transmitted to the monitoring control unit, and the monitoring control unit stores information on each set output light level in the MPU. As a result, the output light level adjustment is completed.

  As described above, in the embodiment of the present invention, the power consumption can be suppressed by adjusting the output light levels of the interface board and the subscriber-side line terminator. Moreover, since it is not necessary to attach an optical attenuator by this invention, the convenience improves.

  Based on the above, the output light level automatic adjustment sequence according to the first embodiment of the present invention will be described below with reference to FIG. FIG. 5 is an explanatory diagram of an automatic adjustment sequence of the output light level at the initial startup of the interface board according to the first embodiment of the present invention.

a. First, the initial startup of the IF is performed.
b. Next, the ONU that receives the optical signal transmitted from the IF optical module by the APD transmits a response signal from the semiconductor laser in response to the signal, thereby establishing signal detection.
c. Next, the IF initial startup and the signal detection notification are completed by notifying the monitoring control unit of the signal detection from the IF.
d. Next, a command to start adjustment of the output light level of the IF optical module and the output light level of the ONU optical module is commanded from the MPU of the monitoring controller.
e. Then, based on the command, the IF transmits a signal to that effect to the ONU by the optical output of the initial level intensity of the IF semiconductor laser, and requests the ONU light reception level and output level.
f. Next, the optical signal from the IF is detected by the APD of the optical module of the ONU, and the output is output to the ASIC. The ASIC transmits the information about the received light level to the optical signal of the initial level intensity of the semiconductor laser of the optical module of the ONU. By transmitting to the IF, the ONU light reception level response and the output level response are executed.
g. Next, the APD of the IF optical module detects this optical signal, and the IF determines whether the output light level of the semiconductor laser of the IF optical module is within an appropriate range based on the received light level information in the optical signal. Judgment is made by the provided ASIC. At the same time, the ASIC provided in the IF determines whether the output level of the semiconductor laser of the ONU optical module is within an appropriate range based on the light receiving level of the APD of the IF optical module. The exchange of optical signals is repeated until the output light level of each semiconductor laser becomes appropriate, and the drive voltage value when the output light level becomes appropriate is stored in each ASIC.
h. Next, when the output light level of each semiconductor laser becomes appropriate, an output light level adjustment end response is transmitted to the monitoring control unit, and the monitoring control unit stores information on each set output light level in the MPU. Thus, the output light level adjustment for one ONU is completed.
i. Next, the MPU of the monitoring control unit determines whether or not the ONU whose output light level adjustment is completed is the last ONU, and repeats the same sequence until the output light level adjustment of the last ONU is completed.
j. Next, when the output light level adjustment of the last ONU is completed, the maximum output light level among the output light levels set for each ONU of the semiconductor laser of the IF optical module stored in the MPU is set. The connection is established by storing the set value in the IF ASIC.

  As described above, in the first embodiment of the present invention, the output light level of the semiconductor laser provided in each optical module by the exchange of optical signals between the OLT and the ONU before connection establishment at the initial startup of the interface board is set. Since it is automatically adjusted to an appropriate value, it is not necessary to provide an optical attenuator for each interface board.

  Next, an automatic adjustment sequence of the output light level according to the second embodiment of the present invention will be described with reference to FIG. FIG. 6 is an explanatory diagram of an automatic readjustment sequence of the output light level during operation of Embodiment 2 of the present invention.

a. First, the monitoring control unit detects the arrival of a preset readjustment time during operation. Since this readjustment time has a different readjustment frequency depending on the operating environment of the ONU connected to the OLT, the OLT monitoring control unit is provided with a function of changing the readjustment time according to the operating environment. The readjustment frequency is, for example, once / day, and the time required for readjustment is, for example, about several seconds.
b. Next, an output light level readjustment request is made from the monitoring control unit to the IF.
c. Next, based on the directive, it is confirmed whether or not readjustment is necessary, and the operation is suspended only when necessary, and the IF sends a signal to that effect for the operation of the IF semiconductor laser. It transmits to ONU by the light output of the set intensity, and requests the ONU light reception level and output level.
d. Next, the optical signal from the IF is detected by the APD of the optical module of the ONU, and the output is output to the ASIC. The ASIC sets information about the light reception level for the operation of the semiconductor laser of the optical module of the ONU. An ONU light reception level response and an output level response are executed by transmitting to the IF by an intensity optical signal.
e. Next, the APD of the IF optical module detects this optical signal, and the IF determines whether the output light level of the semiconductor laser of the IF optical module is within an appropriate range based on the received light level information in the optical signal. Judgment is made by the provided ASIC. At the same time, the ASIC provided in the IF determines whether the output level of the semiconductor laser of the ONU optical module is within an appropriate range based on the light receiving level of the APD of the IF optical module. The exchange of optical signals is repeated until the output light level of each semiconductor laser becomes appropriate, and the drive voltage value when the output light level becomes appropriate is stored in each ASIC.
f. Next, when the output light level of each semiconductor laser becomes appropriate, an output light level adjustment end response is transmitted to the monitoring control unit, and the monitoring control unit stores information on each set output light level in the MPU. Thus, the read light level readjustment for one ONU is completed. When the output light level readjustment is completed, the connection is established and the operation is started again. Such readjustment of the output light level is sequentially executed based on the readjustment time set according to the operational environment of each ONU.

  As described above, in the second embodiment of the present invention, the output light level is automatically readjusted periodically during operation. Therefore, the output light level is higher than the output light level required by the change in the operation environment. In such a case, since the output is readjusted to an appropriate value, power saving can be achieved. For example, when the environmental temperature decreases, the light output of the semiconductor laser increases.

  In addition, when the optical signal transmitted due to deterioration of the branch optical fiber is attenuated due to degradation of the operating environment, the output light level of the IF optical module and the ONU optical module is periodically readjusted. Therefore, stable optical communication can be realized.

  Next, the automatic adjustment sequence of the output light level according to the third embodiment of the present invention will be described with reference to FIG. FIG. 7 is an explanatory diagram of an automatic adjustment sequence of the output light level at the time of new connection of the subscriber-side line termination device according to the third embodiment of the present invention.

a. First, signal detection is established by receiving an optical signal periodically transmitted from the IF optical module by the APD of the newly connected ONU and transmitting a response signal from the semiconductor laser in response to the signal.
b. Next, a signal detection notification is sent from the IF to the monitoring control unit.
c. Next, an output light level adjustment request for the newly connected ONU is made to the IF from the monitoring control unit.
d. Next, based on the command, the IF sends a signal to that effect to the newly connected ONU, and requests the light reception level and output level of the newly connected ONU.

  At this time, since the distance between the newly connected ONU and the OLT is far from the other currently connected ONUs, and the output optical level of the IF optical module in operation that is regularly adjusted is not sufficient, it is new. In some cases, the optical signal does not reach the connection ONU, and it is not detected that a new connection ONU is connected.

  Therefore, an optical signal in which the output light level of the IF optical module is set to a level stronger than the regularly adjusted output light level is transmitted. However, the output light level is within an allowable range in which the APD of the optical module of another ONU currently connected is not damaged.

e. Next, the optical signal from the IF is detected by the APD of the optical module of the newly connected ONU, and the output is output to the ASIC. The ASIC provides information on the light reception level of the operation of the semiconductor laser of the optical module of the newly connected ONU. Therefore, the newly connected ONU light reception level response and the output level response are executed by transmitting to the IF by the optical signal having the set intensity.
f. Next, the APD of the IF optical module detects this optical signal, and the IF determines whether the output light level of the semiconductor laser of the IF optical module is within an appropriate range based on the received light level information in the optical signal. Judgment is made by the provided ASIC. At the same time, the ASIC provided in the IF determines whether the output level of the semiconductor laser of the optical module of the newly connected ONU is within an appropriate range based on the light reception level of the APD of the IF optical module. The exchange of optical signals is repeated until the output light level of each semiconductor laser becomes appropriate, and the drive voltage value when the output light level becomes appropriate is stored in each ASIC.
g. Next, when the output light level of each semiconductor laser becomes appropriate, an output light level adjustment end response is transmitted to the monitoring control unit, and the monitoring control unit sends a new semiconductor laser of the IF optical module stored in the MPU. The connection is established by storing the set value in the ASIC of the IF so as to set the value of the maximum output light level among the output light levels set for all the ONUs including the connection ONU.

  As described above, in the third embodiment of the present invention, when an ONU is newly connected, the output light level of the interface board is set to a level stronger than the regularly adjusted output light level, and the optical signal is transmitted. Therefore, the connection can be established by reliably detecting the connection of the new connection ONU.

  As mentioned above, although embodiment of this invention containing Example 1 thru | or Example 3 was demonstrated, this invention is not restricted to the structure demonstrated above, Various changes are possible. For example, the optical module shown in FIG. 2 is only an example, and can be applied to various optical modules shown in publicly known documents such as the above-mentioned Patent Document 1 or Patent Document 2.

  In addition, the GE-PON system shown in FIG. 1 is not duplexed, but in order to enhance safety, a duplexed GE-PON equipped with a normal use optical module and an abnormal use optical module on the subscriber side line terminating device side. The present invention is also applied to a system (for example, see Japanese Patent Application Laid-Open No. 2008-227782). In this case, prior to establishing the connection, the output light level is automatically adjusted for both the normal use optical module and the abnormal use optical module.

  Further, in the embodiments of the present invention including the above-described Examples 1 to 3, the optical star coupler is used when the optical fiber is branched from the basic optical fiber to the branched optical fiber. However, a multi-stage is used instead of the optical star coupler. A configured optical splitter may be used.

10, 50 Station side line terminator 11, 51 Interface board 12 ASIC
16, 56 Monitoring control unit 17, 57 MPU
20, 52 Optical module 21 WDM filter 22 Avalanche photodiode 23 Preamplifier 24 Amplifier 25 Optical isolator 26 Semiconductor laser 27 Monitor photodiode 28 Drive circuit 30, 60 Subscriber side line termination device 31, 61 Optical module 32, 53, 62 ASIC
41, 71 Core optical fiber 42, 72 Optical star coupler 43, 73 Branch optical fiber 54, 58 FPGA
59 Optical attenuator

Claims (7)

One or more interface boards and a station side line termination device comprising one monitoring control unit for monitoring and controlling the interface boards;
At least one subscriber line terminator connected to the interface board;
By transmitting and receiving an optical signal between the subscriber-side line terminator and the interface board, by measuring a light reception level at the subscriber-side line terminator, an output light level from the optical module of the interface board, Means for automatically adjusting the output light level of the optical module of the interface board. One or more interface boards and a station side line termination device comprising one monitoring control unit for monitoring and controlling the interface boards;
At least one subscriber line terminator connected to the interface board;
By transmitting and receiving an optical signal between the subscriber-side line terminator and the interface board, by measuring the light reception level at the interface board, the output light level from the optical module of the subscriber-side line terminator, Means for automatically adjusting the output light level of the optical module of the subscriber line terminating device.   The means for automatically adjusting the output light level of the optical module performs transmission / reception of an optical signal for automatically adjusting the output light level in a handshake before the connection between the subscriber-side line terminator and the interface board is established. The optical communication apparatus according to claim 1 or 2, which has a function.   3. The light according to claim 1, wherein the means for automatically adjusting the output light level of the optical module has a function of periodically transmitting and receiving an optical signal for automatically adjusting the output light level during operation. Communication device.   Means for automatically adjusting the output light level of the optical module is obtained from each subscriber-side line terminating device by transmitting and receiving an optical signal for automatically adjusting the output light level at the initial startup of the interface board. The optical communication apparatus according to claim 1, wherein the optical communication apparatus has a function of setting a maximum value among the appropriate output light levels as an output light level of the optical module of the interface board.   The means for automatically adjusting the output optical level of the optical module receives and transmits an optical signal for automatically adjusting the output optical level when a new subscriber-side line terminator is connected to the station-side line terminator. The optical communication device according to claim 1, which has a function to perform.   The output optical level from the optical module of the interface board in the transmission / reception of the optical signal for automatically adjusting the output optical level is higher than the output optical level set at the time of operation, and the light of the already connected subscriber line terminating device The optical communication device according to claim 5, wherein the optical communication device has a function of setting a range lower than an allowable input light level of the module.

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