JP2015061270A - Optical communication system, optical network unit, optical line terminal, and optical communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To implement power saving of an Optical Network Unit.SOLUTION: A transmission side optical communication device 1 comprises: an electrical-optical conversion unit 10; an optical-electrical conversion unit 11; and an output change unit 12 for changing intensity of an optical signal output from the electrical-optical conversion unit 10 according to an instruction order included in an optical signal from a reception side optical communication device 2. The reception side optical communication device 2 comprises: an optical-electrical conversion unit 20; a performance value measurement unit 21 for measuring a performance value for evaluating quality of an optical signal from the transmission side optical communication device 1; a reception side evaluation unit 22 for evaluating the quality of the optical signal from the transmission side optical communication device 1 on the basis of the performance value, before making an optical signal including an instruction order for changing intensity of the optical signal from the transmission side optical communication device 1 according to a result of the evaluation be output to the transmission side optical communication device 1; and an electrical-optical conversion unit 23.

Description

  The present invention relates to an optical communication system including a station-side communication device and a home-side communication device, and more particularly to an optical communication system, a home-side communication device, a station-side communication device, and an optical communication method that realize power saving of the home-side communication device. Is.

  An optical communication system includes a communication device that transmits and receives optical signals and an optical fiber that connects the communication devices. FIG. 10 shows a configuration of a 10G-EPON (10 Gigabit-Ethernet (registered trademark) Passive Optical Network) system as an example of an optical communication system. This system includes a station side communication device (Optical Line Terminal: OLT) 100, a plurality of home side communication devices (Optical Network Unit: ONU) 101-1 to 101-n, and an optical splitter 102. An economical system is realized by sharing a plurality of ONUs 101-1 to 101-n.

In general, the performance of an optical communication system is standardized. In the 10G-EPON system, the signal quality is BER (Bit Error Rate) at the time of reception of 10 ⁻³ or less, and transmission between the OLT and the ONU. It is prescribed that the distance is within 20 km (Non-Patent Document 1). That is, a system is required in which the BER at the time of reception at a transmission distance of 20 km is 10 ⁻³ or less.

In actual use with respect to such provisions, communication is performed at various transmission distances that are shorter than the upper limit value (20 km) prescribed by the standard, but the output of the transmission device is uniformly when the transmission distance is 20 km. Is set to a large value such that the BER at the time of reception is 10 ⁻³ or less. For this reason, the BER at the time of reception is sufficiently lower than 10 ^−3, but the power consumption of the transmission device is increased. In the case of uniform transmission output, the signal received by the OLT has a large difference in the strength of the received signal depending on the distance from the connected ONU and the transmission state, so that high performance of the receiving device is also required. The

  Conventionally, an optical communication system disclosed in Patent Document 1 is known as a technique for controlling the output level of an optical transmission apparatus. In this optical communication system, as shown in FIG. 11, the optical signal output from the optical transmission device 211 is received by the optical reception device 213 via the transmission path 212, and the level signal generation unit 213 </ b> A of the optical reception device 213 receives the optical signal. A level signal 214 having information corresponding to the value of the received power is generated and fed back to the optical transmitter 211.

  The signal processing unit 211C of the optical transmission device 211 generates an adjustment signal in response to the level signal 214 transmitted from the reception side, and outputs this adjustment signal to the level adjustment unit 211B. The level adjustment unit 211B adjusts the power of the optical signal output from the optical transmission unit 211A in response to the adjustment signal output from the signal processing unit 211C. In this way, the power of the optical signal received by the optical receiving device 213 is adjusted so as to be always a constant value.

JP 2003-163638 A

IEEE Std 802.3av, 2009

  In the optical communication system disclosed in Patent Document 1, the evaluation of the level signal 214 for adjusting the output level of the optical transmission device 211 (evaluation of whether to increase or decrease the output level of the optical transmission device 211) is performed. The signal processing unit 211 </ b> C has a problem that the power consumption of the optical transmission device 211 becomes large. That is, there is a problem that the power consumption of the ONU in the optical communication system becomes large.

  The present invention has been made to solve the above problems, and provides an optical communication system, a home side communication device, a station side communication device, and an optical communication method capable of realizing power saving of the home side communication device. For the purpose.

  An optical communication system according to the present invention includes a home side communication device and a station side communication device connected to the home side communication device via a transmission path, and the home side communication device is connected to the station side communication device. In accordance with a first optical output means for outputting an optical signal, a first optical input means for inputting an optical signal from the station side communication apparatus, and a command command included in the optical signal from the station side communication apparatus, Output changing means for changing the intensity of the optical signal output from the first optical output means, the station side communication device, the second optical output means for outputting the optical signal to the home side communication device, A second optical input means for inputting an optical signal from the home side communication device; a performance value measuring means for measuring a performance value for evaluating the quality of the optical signal from the home side communication device; Based on this, the quality of the optical signal from the home side communication device is evaluated. And an evaluation unit that outputs an optical signal including a command command for changing the intensity of the optical signal from the home-side communication device to the home-side communication device from the second optical output unit. It is a feature.

In the configuration example of the optical communication system of the present invention, the home side communication device further includes error correction coding means for performing error correction coding of a signal to be sent to the station side communication device, and the station side communication The performance value measuring means of the device corrects the error of the signal from the home-side communication device, the bit error rate, the number of correction bits that have corrected the error, the number of uncorrectable codewords that could not be corrected, the error bit And error correction decoding means for measuring at least one of the number, codeword error rate, error frame number, and frame error rate as the performance value.
Further, in one configuration example of the optical communication system of the present invention, the performance value measuring means of the station side communication device further includes a round trip time which is a time required for communication between the station side communication device and the home side communication device. Round trip time measuring means for measuring as a performance value, and signal strength measuring means for measuring the strength of a signal from the home side communication device as the performance value, and the evaluation means for the station side communication device, Using the performance value measured by the error correction decoding means, the round trip time measured by the round trip time measuring means, and the signal strength measured by the signal strength measuring means, the home-side communication device The quality of the optical signal from is evaluated.

In one configuration example of the optical communication system of the present invention, the output changing unit of the home side communication device receives a registration permission signal from the station side communication device when establishing a link with the station side communication device. The registration request signal is repeatedly output from the first optical output means to the station side communication device while gradually increasing the strength of the registration request signal for establishing a link, and the station side communication device permits registration. When a signal is received, a reception confirmation signal is output from the first optical output unit to the station-side communication device, and the evaluation unit of the station-side communication device determines that the quality of the optical signal from the home-side communication device is If it is determined that the registration is good, a registration permission signal is output from the second light output means to the home communication device.
In the configuration example of the optical communication system according to the present invention, the evaluation unit evaluates the quality of the optical signal from the home side communication device by comparing the performance value with a corresponding threshold value set in advance. The command command for changing the intensity of the optical signal from the home side communication device in a direction in which the quality of the optical signal is improved is generated.

Further, the home side communication device of the present invention outputs an optical output means for outputting an optical signal to the station side communication device, an optical input means for inputting an optical signal from the station side communication device, and an output from the optical output means. Output changing means for changing the intensity of the optical signal, the output changing means according to the evaluation result of the quality of the optical signal input from the home side communication apparatus to the station side communication apparatus When the optical signal output from the optical signal is received, the intensity of the optical signal output from the optical output means is changed according to a command command included in the optical signal.
The station-side communication device of the present invention includes an optical output unit that outputs an optical signal to the home-side communication device, an optical input unit that inputs an optical signal from the home-side communication device, and the home-side communication device. Performance value measuring means for measuring a performance value for evaluating the quality of the optical signal, and evaluating the quality of the optical signal from the home side communication device based on the performance value, and the home side according to the evaluation result And an evaluation unit that outputs an optical signal including a command command for changing the intensity of the optical signal from the communication device to the home communication device from the optical output unit.

  The optical communication method of the present invention includes a transmission step in which the home side communication device outputs an optical signal to a station side communication device connected via a transmission line, and the station side communication device is connected to the home side communication device. A performance value measuring step for measuring a performance value for evaluating the signal quality based on the optical signal from, and the station side communication device determines the quality of the optical signal from the home side communication device based on the performance value. An evaluation step of evaluating and outputting an optical signal including a command command for changing the intensity of the optical signal from the home-side communication device to the home-side communication device according to the evaluation result; and the home-side communication device Includes an output changing step of changing the intensity of the optical signal output from the own apparatus in accordance with a command command included in the optical signal from the station side communication apparatus.

  According to the present invention, since the performance value measuring means and the evaluation means are provided in the station side communication device, the means for evaluating the signal quality in the home side communication device can be made unnecessary. The side communication device can be reduced in size, saved in power, and reduced in price. In the present invention, evaluation of received signals from a plurality of home-side communication devices can be performed for each home-side communication device by the performance value measuring means and the evaluation means of the station-side communication device, and a device for evaluating signals The increase can be suppressed.

  Also, in the present invention, the bit error rate, the number of correction bits that have corrected the error, the number of uncorrectable code words that could not be corrected, the number of error bits, the code word error rate, the number of error frames, and the frame error rate Even if the strength of the signal from the home-side communication device is high by measuring at least one as the performance value, the strength of the optical signal from the home-side communication device when the quality of the signal evaluated from the performance value is poor By raising the signal quality, the signal quality can be improved. In addition, even when the signal strength from the home side communication device is small, if the quality of the signal evaluated from the performance value is good, the strength of the optical signal from the home side communication device can be lowered, and power can be efficiently saved. Can be realized.

  In the present invention, two or more of the performance value measured by the error correction decoding means, the round trip time measured by the round trip time measuring means, and the signal strength measured by the signal strength measuring means are used to By evaluating the quality of the optical signal from the communication device on the side, if the determination result that the optical output of the home communication device should be increased by two or more determinations, the optical output is increased to achieve one performance value The signal quality can be evaluated more accurately than the case where only the signal is used. In addition, when the determination result that the optical output of the home-side communication device should be reduced is obtained by two or more determinations, the optical output is decreased too much than when only one performance value is used. Data loss can be avoided. In addition, when the determination result that the optical output of the home side communication device should be increased by one determination, the optical output is increased when the determination result that the optical output of the home side communication device should be decreased by two or more determinations. If the optical output from the home side communication device deteriorates, the optical output can be immediately increased to avoid data loss. By making the judgment more strict than when the optical output is increased, it is possible to avoid the occurrence of data loss due to the excessive decrease of the optical output. In addition, when the determination result that the optical output of the home side communication device should be increased by two or more determinations, the optical output is increased when the determination result that the optical output of the home side communication device should be increased is determined by three or more determinations. By lowering the light output when light is emitted, the signal quality can be evaluated more accurately than when only one performance value is used. Therefore, it is possible to avoid a loss of data due to excessively low optical output.

  Further, in the present invention, when establishing a link between the home side communication device and the station side communication device, the registration request for link establishment is received until the home side communication device receives a registration permission signal from the station side communication device. While gradually increasing the intensity of the signal, the registration request signal is repeatedly output from the first optical output unit of the home side communication device to the station side communication device, and the evaluation unit of the station side communication device receives the light from the home side communication device. When it is determined that the signal quality is good, the registration permission signal is output from the second optical output unit of the station side communication device to the home side communication device, thereby establishing a link between the home side communication device and the station side communication device. Can be established.

It is a block diagram which shows the structure of the optical communication system which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the specific example of the optical communication system which concerns on the 1st Embodiment of this invention. It is a sequence diagram explaining operation | movement of the optical communication system which concerns on the 1st Embodiment of this invention. It is a sequence diagram explaining operation | movement of the optical communication system when the transmission side optical communication apparatus establishes a link with the reception side optical communication apparatus in the 1st Embodiment of this invention. It is a block diagram which shows the structure of the optical communication system which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the optical communication system which concerns on the 3rd Embodiment of this invention. It is a figure which shows one example of the transmission output control of the station side communication apparatus in the 4th Embodiment of this invention. It is a sequence diagram explaining operation | movement of the optical communication system when a station side communication apparatus establishes a link with a home side communication apparatus in the 4th Embodiment of this invention. It is a sequence diagram explaining another operation | movement of the optical communication system when a station side communication apparatus establishes a link with a home side communication apparatus in the 4th Embodiment of this invention. It is a block diagram which shows the structure of 10G-EPON system which is an example of an optical communication system. It is a block diagram which shows the structure of the conventional optical communication system which controls the output level of an optical transmitter.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing a configuration of an optical communication system according to the first embodiment of the present invention. The optical communication system according to the present embodiment includes a transmission-side optical communication device 1, a reception-side optical communication device 2, and a transmission path 3 such as an optical fiber that connects the transmission-side optical communication device 1 and the reception-side optical communication device 2. It consists of.

  The transmission-side optical communication device 1 includes an electro-optical conversion unit 10 (first optical output means) that converts a transmission signal to the reception-side optical communication device 2 into an optical signal and outputs the optical signal, and the reception-side optical communication device 2 The optical-electrical conversion unit 11 (first optical input means) that inputs the optical signal of the optical signal and converts it into an electrical signal, and the electrical-optical conversion unit according to a command command included in the optical signal from the reception-side optical communication device 2 And an output changing unit 12 that changes the intensity of the optical signal output from the unit 10.

  The reception-side optical communication device 2 includes an optical-electric conversion unit 20 (second optical input means) that inputs an optical signal output from the transmission-side optical communication device 1 and converts the optical signal into an electrical signal, and a transmission-side optical communication device. The performance value measuring unit 21 that measures the performance value for evaluating the quality of the optical signal from 1 and the quality of the optical signal from the transmission side optical communication device 1 are evaluated based on the performance value, and according to the evaluation result A receiving side evaluation unit 22 (evaluating means) for outputting an optical signal including a command command for changing the intensity of the optical signal from the transmitting side optical communication device 1 to the transmitting side optical communication device 1, and a transmitting side optical communication device And an electro-optical converter 23 (second optical output means) for converting the transmission signal to 1 into an optical signal and outputting the optical signal.

  In general, an optical communication system is equipped with an error correction encoding function and an error correction decoding function in order to correct an error occurring in the transmission path 3 between the transmission side optical communication apparatus 1 and the reception side optical communication apparatus 2. For example, a 10G-EPON system, which is an example of an optical communication system, employs a Reed Solomon (RS (255, 223)) code as an error correction code. FIG. 2 shows a specific configuration of an optical communication system in which an error correction coding function and an error correction decoding function are installed.

In addition to the configuration shown in FIG. 1, the transmission side optical communication device 1 includes an error correction encoding unit 13 that performs error correction encoding of a signal to be sent to the reception side optical communication device 2. The electro-optical converter 10 converts the signal error-encoded by the error correction encoder 13 into an optical signal and outputs the optical signal.
The receiving-side optical communication device 2 includes an error correction decoding unit 21A that corrects an error in the input signal as the performance value measurement unit 21.

FIG. 3 is a sequence diagram for explaining the operation of the optical communication system according to the present embodiment. Here, the transmission side optical communication device 1 is an ONU, and the reception side optical communication device 2 is an OLT.
The electro-optical converter 10 of the transmission side optical communication apparatus 1 sends an optical signal (user data) to the reception side optical communication apparatus 2 via the transmission path 3 (step S10 in FIG. 3).

  The optical-electric conversion unit 20 of the reception-side optical communication device 2 receives the optical signal from the transmission-side optical communication device 1, converts it to an electrical signal, and outputs it to the error correction decoding unit 21A. The error correction decoding unit 21A corrects an error in the signal input from the photoelectric conversion unit 20, and the number of input bits of the signal, the number of correction bits for correcting the error, and a unit for performing the error correction processing The number of uncorrectable codewords in which the error could not be corrected is counted (step S11 in FIG. 3) among the following codewords (255 bytes in the case of RS (255, 223) code).

  The reception side evaluation unit 22 of the reception side optical communication device 2 evaluates the quality of the optical signal input from the transmission side optical communication device 1 using the result counted by the error correction decoding unit 21A. Specifically, the receiving side evaluation unit 22 multiplies the number of uncorrectable code words by the known minimum number of error bits that can be included in the uncorrectable code word (17 bits in the case of the RS (255, 223) code). The number of error bits is obtained by adding the number of correction bits to the value, and the error rate (BER) is calculated by dividing the number of error bits by the number of input bits (step S12 in FIG. 3). The technique of this embodiment can be applied with less error when the BER is sufficiently lower than the value obtained by dividing the minimum number of error bits that can be included in one uncorrectable codeword by the total number of bits in the codeword.

  Then, the receiving side evaluation unit 22 uses the calculated BER as a performance value to be evaluated for signal quality, compares this BER with a preset threshold value, and determines that the signal quality is good if the BER is equal to or less than the threshold value. Thus, a command command (evaluation result) for instructing to reduce the optical output of the transmission side optical communication apparatus 1 is stored in a control signal such as an extended MPCP frame or an extended OAM frame. Further, the receiving side evaluation unit 22 determines that the signal quality is poor if the BER is larger than the threshold value, and extends a command command (evaluation result) for instructing to increase the optical output of the transmitting side optical communication device 1. It is stored in a control signal such as an MPCP frame or an extended OAM frame (step S13 in FIG. 3).

  The electro-optical conversion unit 23 of the reception-side optical communication device 2 converts the control signal input from the reception-side evaluation unit 22 into an optical signal and sends the optical signal to the transmission-side optical communication device 1 (step S14 in FIG. 3).

The calculation of the BER is performed every time the number of input bits counted by the error correction decoding unit 21A reaches a constant multiple of the inverse of the BER to be calculated (for example, 10 times 10 ⁴ bits when the BER is 10 ⁻³ ). Or may be performed every preset unit time. In order to ensure a sufficient number of input bits, a part of the number of input bits used in the previous calculation (for example, the last 100 bits or 100 nsec) may be used.

The threshold value set in advance in the receiving side evaluation unit 22 is 1 considering the thermal noise (white noise) of the transmission line 3 with respect to the upper limit value (for example, 10 ⁻³ ) of the BER specified in the standard. A value obtained by taking a / 10 margin (for example, 10 ⁻⁴ ) may be used. In general, in the case of errors due to thermal noise, even when errors are concentrated locally, it is unlikely that the BER will be more than 10 times larger than the average. For example, if 10 ⁻⁴ is set as a threshold, the BER is 10 times 10 ⁻⁴ . The possibility of exceeding the value of 10 ⁻³ is low.

Similarly, 10 ⁻⁵ taking a 1/100 margin in consideration of device-derived burst noise may be used as the threshold value. When installing the transmission side optical communication device 1 or the reception side optical communication device 2, the error distribution is examined, and according to this error distribution (whether the error is caused by thermal noise or burst noise, etc. is determined). And a threshold value may be set.

The optical-electrical conversion unit 11 of the transmission-side optical communication device 1 receives the optical signal from the reception-side optical communication device 2, converts it into an electrical signal, and outputs it to the output changing unit 12.
When the signal input from the photoelectric conversion unit 11 is a control signal and the command signal is included in the control signal, the output changing unit 12 receives the command of the electrical / optical conversion unit 10 according to the command command. Change the light output. Specifically, when receiving a command command to reduce the light output, the output changing unit 12 emits light for a preset value (for example, 1 dB) during a period in which data is not output (for example, a Discovery Window period, etc.). When a command to increase the light output is received by changing the output, a change is made to increase the light output by a preset value during a period in which no data is output (step S15 in FIG. 3).

  Unlike the prior art, in this embodiment, the ONU (transmission-side optical communication device 1) does not have an evaluation unit (the signal processing unit 211C in FIG. 11), thereby reducing the number of ONUs, reducing power consumption, and Low price can be realized. The OLT (receiving optical communication device 2) is connected to a plurality of ONUs. In the present embodiment, the evaluation of received signals from a plurality of ONUs can be performed for each ONU by the OLT performance value measurement unit 21 and the reception side evaluation unit 22. The performance value measurement unit 21 and the reception side evaluation unit 22 can be shared for signals from a plurality of ONUs, and an increase in devices for evaluating signals can be suppressed.

  The Discovery Window is a period in which an ONU that has not established a link transmits a registration request signal (Register Req.) For requesting link establishment to the OLT. It is a period not to be performed. The period for changing the optical output of the transmission side optical communication apparatus 1 is not limited to the Discovery Window period, but the transmission side optical communication apparatus 1 itself, such as a sleep period or an output period of other ONUs in a DBA cycle in the 10G-EPON system, Any period that does not output data is acceptable.

  In this embodiment, BER is used as a performance value to be compared with a threshold value, but the performance value is not limited to this, and the number of uncorrectable code words in an arbitrary period such as a sleep period or a DBA cycle may be used as the performance value. The number of correction bits in an arbitrary period may be used as a performance value, the number of error bits in an arbitrary period may be used as a performance value, or the number of uncorrectable code words (or the number of uncorrectable code words and corrections in an arbitrary period). The codeword error rate calculated by dividing the sum of the number of codewords including bits) by the total number of received codewords in the arbitrary period may be used as the performance value.

  Further, the number of error frames realized by an FCS (Frame Check Sequence) function may be used as a performance value, or a frame error rate calculated by dividing the number of error frames by the number of all received frames may be used as a performance value.

  As a method of changing the optical output of the transmission side optical communication apparatus 1, for example, a table in which the laser bias current and the modulation current corresponding to the ambient temperature and the optical output intensity are recorded in advance may be prepared. When changing the light output of the electro-optical converter 10, the output changing unit 12 acquires the value of the ambient temperature from a temperature measuring unit (not shown) that measures the ambient temperature of the transmission side optical communication device 1, and this ambient temperature. The values of the bias current and the modulation current corresponding to the light output intensity after the change and the modulation current may be obtained from the table, and the laser bias current and the modulation current of the electro-optical converter 10 may be set to the obtained values.

FIG. 4 is a sequence diagram for explaining the operation of the optical communication system when the transmission side optical communication device 1 (ONU) establishes a link with the reception side optical communication device 2 (OLT).
At the time of link establishment, a period (Discovery Windows) for transmitting a registration request (Register Req.) Signal from the electro-optical conversion unit 23 of the reception side optical communication apparatus 2 to the transmission side optical communication apparatus 1 with no link established. The Discovery Gate signal to be instructed is transmitted (step S20 in FIG. 4).

  The electro-optical conversion unit 10 of the transmission side optical communication apparatus 1 that has not established a link transmits a registration request signal to the reception side optical communication apparatus 2 during a period (Discovery Windows) instructed by the reception side optical communication apparatus 2 ( FIG. 4 step S21).

  The reception side evaluation unit 22 of the reception side optical communication device 2 performs the quality evaluation of the signal received from the transmission side optical communication device 1 by the above method. At the time of this link establishment, when it is determined that the signal quality is poor, the reception side evaluation unit 22 performs the discovery from the electro-optical conversion unit 23 of the reception side optical communication device 2 similarly to the previous transmission process (step S20). A Gate signal is transmitted (step S22 in FIG. 4).

  If the output changing unit 12 of the transmission side optical communication apparatus 1 receives the Discovery Gate signal again before receiving the Register signal from the reception side optical communication apparatus 2, the light intensity P1 of the immediately preceding registration request (Register Req.) Signal is received. The output is changed more so that the registration request (Register Req.) Signal is transmitted again from the electro-optic conversion unit 10 with the changed light intensity P2 (step S23 in FIG. 4). Thus, the process of gradually increasing the optical output of the transmission side optical communication device 1 is repeated up to a preset maximum number of times until a Register signal is received from the reception side optical communication device 2.

  When it is determined that the signal quality is good, the reception side evaluation unit 22 of the reception side optical communication device 2 causes the electro-optical conversion unit 23 to transmit a registration permission (Register) signal to the transmission side optical communication device 1 (step in FIG. 4). S24).

  When the output change unit 12 of the transmission side optical communication device 1 receives the Register signal from the reception side optical communication device 2, the output change unit 12 receives from the electro-optical conversion unit 10 with the same light intensity as that of the immediately preceding registration request (Register Req.) Signal. A reception confirmation (Register ACK) signal is transmitted to the side optical communication device 2 (step S25 in FIG. 4). In this way, a link between the transmission side optical communication device 1 and the reception side optical communication device 2 is established.

  When the link described in FIG. 4 is established, the output is switched at a rough n level so that the link can be established in a short time. In the operation after the link establishment described in FIG. n) Perform at level. As a result, it is possible to reduce the influence on the increase in time required for link establishment, and to perform optimum power saving by performing fine output control after link establishment.

  In order to evaluate the bit level with high accuracy, a test signal is transmitted from the transmission side optical communication apparatus 1 to the reception side optical communication apparatus 2, and the reception side evaluation unit 22 of the reception side optical communication apparatus 2 is stored in advance. The signal quality may be evaluated by comparing the error-free test signal pattern with the received test signal. In this case, although a test frame is required, there is an advantage that the quality can be accurately evaluated even if an error exceeding the error correction performance occurs in the transmission line 3.

  On the other hand, there is a method using an extended frame (extended OAM frame) as an evaluation method that can only be evaluated in units of frames but does not require an additional frame or a change to an existing device. In this method, when an extended frame (extended OAM frame) is transmitted from the transmission side optical communication apparatus 1 to the reception side optical communication apparatus 2, the reception is performed only when the extended OAM frame can be received without error by only error correction. Using the fact that the reception confirmation signal indicating that the reception has been performed is sent from the reception-side optical communication apparatus 2 to the transmission-side optical communication apparatus 1, the quality is evaluated based on the presence or absence of the reception confirmation signal.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the first embodiment, signal quality is evaluated by comparing one performance value with a threshold value. However, a plurality of performance values may be compared with corresponding threshold values. For example, the count result or error rate in the above error correction, the strength of the received signal, and the round trip time (RTT) that is the time required for communication between the transmission side optical communication device 1 and the reception side optical communication device 2 Signal quality may be evaluated using two or more.

FIG. 5 is a block diagram showing a configuration of an optical communication system according to the second embodiment of the present invention. The same reference numerals are given to the same configurations as those in FIGS.
In the example of the present embodiment, an error correction decoding unit 21A, a signal strength measurement unit 21B, and an RTT measurement unit 21C are provided as the performance value measurement unit 21a of the reception-side optical communication device 2.

  The operation of the error correction decoding unit 21A is as described in the first embodiment. The signal strength measuring unit 21 </ b> B measures the strength of the received signal input from the photoelectric conversion unit 20. The RTT measurement unit 21C measures RTT using a measurement signal, for example. Since the RTT measurement technique is a well-known technique, detailed description thereof is omitted.

  The receiving side evaluation unit 22a of the receiving side optical communication apparatus 2 determines the performance values (BER, number of uncorrectable codewords, number of correction bits, number of error bits, codeword error rate, number of error frames) obtained by the error correction decoding unit 21A. , Any one of the frame error rates) is compared with a corresponding threshold value set in advance, the intensity of the received signal measured by the signal strength measurement unit 21B is compared with a corresponding threshold value set in advance, and the RTT measurement unit 21C Compare the measured RTT with a corresponding preset threshold.

  When the reception side evaluation unit 22a determines that the optical output of the transmission side optical communication device 1 should be reduced by two or more of the performance value, reception signal strength, and RTT obtained by the error correction decoding unit 21A, A command command (evaluation result) for instructing to reduce the optical output of the transmission side optical communication apparatus 1 is stored in a control signal such as an extended MPCP frame or an extended OAM frame. Further, the reception side evaluation unit 22 has determined that the optical output of the transmission side optical communication device 1 should be increased by two or more of the performance value, reception signal strength, and RTT obtained by the error correction decoding unit 21A. In this case, a command command (evaluation result) for instructing to increase the optical output of the transmission side optical communication apparatus 1 is stored in a control signal such as an extended MPCP frame or an extended OAM frame.

  Similarly to the first embodiment, the reception side evaluation unit 22a has good signal quality and the optical performance of the transmission side optical communication device 1 if the performance value obtained by the error correction decoding unit 21A is equal to or less than the corresponding threshold value. If it is determined that the output should be reduced and the performance value obtained by the error correction decoding unit 21A is larger than the corresponding threshold value, it is determined that the signal quality is poor and the optical output of the transmission side optical communication apparatus 1 should be increased.

  Further, if the received signal strength is greater than the corresponding threshold value, the receiving side evaluation unit 22a determines that the signal quality is good and the optical output of the transmitting side optical communication device 1 should be lowered, and the received signal strength corresponds to the threshold value. If it is less, the signal quality is poor and it is determined that the optical output of the transmission side optical communication apparatus 1 should be increased. Further, the receiving side evaluation unit 22a determines that the signal quality is good if the RTT is equal to or less than the corresponding threshold value, and that the optical output of the transmitting side optical communication device 1 should be lowered, and if the RTT is larger than the corresponding threshold value. It is determined that the signal quality is poor and the optical output of the transmission side optical communication apparatus 1 should be increased.

  The operation of the other configuration is as described in the first embodiment. As described above, when the determination result that the optical output of the transmission side optical communication device 1 should be increased is obtained by two or more determinations among the performance value, the received signal strength, and the RTT, the first optical output is increased. The signal quality can be evaluated more accurately than when only one performance value is used as in the embodiment. In addition, when the determination result that the optical output of the transmission-side optical communication device 1 should be reduced is obtained by two or more determinations among the performance value, the received signal strength, and the RTT, the optical output is decreased to reduce the optical output. Rather than using only one performance value as in the embodiment, it is possible to avoid the loss of data due to too low optical output. Note that if one of the performance value, the received signal strength, and the RTT determines that the optical output of the transmission side optical communication device 1 should be increased, the optical output is increased and two or more determinations indicate the transmission side light. The light output may be lowered when a determination result indicating that the light output of the communication device 1 should be lowered is obtained. Thereby, when the optical signal from the transmission-side optical communication device 1 is deteriorated, the optical output of the transmission-side optical communication device 1 can be immediately increased to avoid data loss, and the optical output is decreased. By making the judgment more strict than when raising the light output, it is possible to avoid the loss of data due to the light output being lowered too much. In addition, when the determination result that the optical output of the transmission side optical communication apparatus 1 should be increased is obtained by two or more determinations among the performance value, the received signal strength, and the RTT, the optical output is increased and the transmission is performed by three or more determinations. The optical output may be reduced when a determination result indicating that the optical output of the side optical communication device 1 should be reduced is obtained. As a result, the signal quality can be evaluated more accurately than when only one performance value is used as in the first embodiment, and when the light output is reduced, the determination is higher than when the light output is increased. Therefore, it is possible to avoid a loss of data due to excessively low optical output.

  In the first and second embodiments, when it is desired to reduce the processing amount of the reception side optical communication device 2, the signal strength and RTT are received from the reception side evaluation units 22 and 22a of the reception side optical communication device 2. Only the count result by the error correction decoding unit 21A is output from the electro-optical conversion unit 23 to the transmission side optical communication device 1, and the output change unit 12 of the transmission side optical communication device 1 sets the error rate described above. Signal quality may be evaluated by performing calculation or threshold processing, and the optical output of the transmission side optical communication apparatus 1 may be changed.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. FIG. 6 is a block diagram showing a configuration of an optical communication system according to the third embodiment of the present invention. The same reference numerals are given to the same configurations as those in FIG. In the present embodiment, a performance value measuring unit 14 that performs the same processing as the performance value measuring units 21 and 21a, and a transmitting side evaluating unit 15 that performs the same processing as the receiving side evaluation units 22 and 22a are provided on the transmitting side. The optical communication apparatus 1 is provided.

  Based on the signal received by the photoelectric conversion unit 11, the performance value measurement unit 14 evaluates the evaluation signal (the performance value obtained by the error correction decoding unit described in the first and second embodiments, the received signal strength, At least one of the RTTs).

  The transmission side evaluation unit 15 evaluates the quality of the signal received by the opto-electric conversion unit 11 based on the evaluation signal input from the performance value measurement unit 14, and based on the evaluation result, the electro-optical conversion unit. A command command for changing the optical output of 10 is output to the output changing unit 12. The output changing unit 12 changes the light output of the electro-optical converting unit 10 in accordance with the command command.

In the present embodiment, the receiving side optical communication device 2 is combined with the configuration having the performance value measuring units 21 and 21a and the receiving side evaluation units 22 and 22a. For example, the received signal to the transmitting side optical communication device 1 is transmitted. As soon as the quality deteriorates, there is an advantage that it is possible to quickly cope with the deterioration of the signal quality by increasing the optical output of the transmission side optical communication apparatus 1 without waiting for the evaluation at the reception side optical communication apparatus 2.
In order to reduce the processing amount of the reception side optical communication device 2, the performance value measurement unit 21 and the reception side evaluation unit 22 are deleted from the reception side optical communication device 2 of FIG. The signal output may be evaluated and the light output may be changed.

[Fourth Embodiment]
In the first to third embodiments, an example in which the optical output of the ONU is changed has been described. With the same method, the OLT is set as the transmission-side optical communication device 1 and the ONU is set as the reception-side optical communication device 2, so that the OLT optical output is changed. The output may be changed. As shown in FIG. 10, since the OLT is connected to a plurality of ONUs, signals addressed to each ONU are transmitted from the OLT in a time division manner. When the optical output of the OLT is changed for each ONU of the transmission destination, the number of times of optical output control and the optical output difference to be controlled at a time can be reduced by transmitting near optical outputs as much as possible.

  For example, only four units of ONU 101-1 to ONU 101-4 in FIG. 10 are connected to the OLT, and a signal is transmitted from the OLT to the ONU 101-1 with the optical output P2, and the optical output P1 from the OLT to the ONU 101-3. When it is determined that the signal is transmitted with (P1> P2) and the signal is transmitted with the optical output P3 (P2> P3) from the OLT to the ONUs 101-2 and 101-4, the signals may be transmitted in the order shown in FIG. good.

FIG. 8 is a sequence diagram for explaining the operation of the optical communication system when the OLT (transmission-side optical communication device 1) establishes a link with the ONU (reception-side optical communication device 2).
At the time of link establishment, a Discovery Gate signal indicating a period (Discovery Windows) for transmitting a registration request (Register Req.) Signal from the OLT electro-optical conversion unit 10 to the ONU that has not established the link is used with the light intensity Pa. Transmit (step S30 in FIG. 8).

  The receiving side evaluation unit 22 of the ONU performs the quality evaluation of the signal received from the OLT by the above method. At the time of this link establishment, if the receiving side evaluation unit 22 determines that the signal quality is poor, it does not execute any processing.

  When the OLT output changing unit 12 does not receive a registration request (Register Req.) Signal from the ONU during the Discovery Windows period, the output changing unit 12 changes the output to be higher than the light intensity Pa of the immediately preceding Discovery Gate signal. The Discovery Gate signal is transmitted again from the electro-optic converter 10 at the light intensity Pb (Pa <Pb) (step S31 in FIG. 8). In this way, the process of gradually increasing the optical output of the OLT is repeated up to a preset maximum number of times until a registration request (Register Req.) Signal is received from the ONU. Before receiving the registration request (Register Req.) Signal from the ONU, if the maximum number of times is repeated, the optical output of the OLT is returned to Pa again, and the optical output of the OLT is gradually increased again.

  When the reception side evaluation unit 22 of the ONU determines that the quality of the signal from the OLT is good, a registration request (Register Req.) From the electro-optical conversion unit 23 to the OLT during a period instructed by the OLT (Discovery Windows). A signal is transmitted (step S32 in FIG. 8).

  When receiving a registration request (Register Req.) Signal from the ONU, the output changing unit 12 of the OLT transmits a registration permission (Register) signal from the electro-optical conversion unit 10 to the ONU with the same light intensity as that of the immediately preceding Discovery Gate signal. (Step S33 in FIG. 8).

  When receiving the Register signal from the OLT, the electro-optical conversion unit 23 of the ONU transmits a reception confirmation (Register ACK) signal to the OLT (Step S34 in FIG. 8). Thus, a link between the OLT and the ONU is established.

  For example, although the evaluation result is sufficiently good even with the Discovery gate signal with the light intensity Pa, it is determined that the evaluation is good for the Discovery gate signal with the light intensity Pb received for the first time after connection of the ONU, and a registration request (Register) is received from the ONU. Req.) Signal may be transmitted. In this case, sufficient power saving of the OLT cannot be performed. Therefore, when the Discovery gate signal is received by the ONU for the same number of times as the number of output switching, and the signal with the lowest received signal strength is received again by the ONU, the registration request is received from the ONU. By transmitting the (Register Req.) Signal, the optical output of the OLT can be set to the minimum optical output with good signal quality.

  As shown in FIG. 9, the OLT electro-optical converter 10 may continuously transmit a plurality of Discovery gate signals with different optical outputs (steps S40 and S41 in FIG. 9). In this case, the receiving side evaluation unit 22 of the ONU determines that the quality is good among the plurality of received discovery gate signals, and selects the discovery gate signal having the minimum signal strength. Then, the reception side evaluation unit 22 transmits a registration request (Register Req.) Signal from the electro-optical conversion unit 23 to the OLT during the period (Discovery Windows) indicated by the selected Discovery gate signal (step in FIG. 9). S42). In this way, the optical output of the OLT can be set to the minimum optical output with good signal quality, and power saving can be realized.

  Furthermore, in the first to fourth embodiments, the degree of error correction processing may be changed or the presence / absence of error correction processing may be controlled from the above evaluation results in order to increase the power saving of the apparatus. . For example, if the evaluation units 15, 22, and 22a determine that the quality of the received signal is good, the error correction processing performed by the error correction decoding unit in the performance value measurement units 14, 21, and 21a is invalidated, or When the correction performance is low but the power consumption is changed to an error correction process such as RS (255, 239) with low power consumption, and the evaluation units 15, 22, and 22a determine that the quality of the received signal is poor, the performance value measurement units 14, 21 , 21a may be changed to error correction processing such as RS (255, 223) with high power consumption but high correction performance.

  Among the devices of the transmission side optical communication device 1 and the reception side optical communication device 2 described in the first to fourth embodiments, at least the performance value measurement unit 14 and the transmission side evaluation unit of the transmission side optical communication device 1 15 and the performance value measuring units 21 and 21a and the receiving side evaluation units 22 and 22a of the receiving side optical communication apparatus 2 are a computer having a CPU (Central Processing Unit), a memory and an interface, and hardware resources thereof. It can be realized by a program to be controlled. The CPU of each device executes the processing described in the first to fourth embodiments in accordance with a program stored in the memory.

  INDUSTRIAL APPLICABILITY The present invention can be applied to a technique for realizing power saving of a home side communication device in an optical communication system including a station side communication device and a home side communication device.

  DESCRIPTION OF SYMBOLS 1 ... Transmission side optical communication apparatus, 2 ... Reception side optical communication apparatus, 3 ... Transmission path, 10 ... Electric-light conversion part, 11 ... Optical-electric conversion part, 12 ... Output change part, 13 ... Error correction encoding part , 14 ... performance value measurement unit, 15 ... transmission side evaluation unit, 20 ... optical-electrical conversion unit, 21 and 21a ... performance value measurement unit, 21A ... error correction decoding unit, 21B ... signal strength measurement unit, 21C ... RTT Measurement unit, 22, 22a... Reception side evaluation unit, 23... Electro-optical conversion unit.

Claims (8)

Consists of a home side communication device and a station side communication device connected to the home side communication device via a transmission line,
The home-side communication device is
First optical output means for outputting an optical signal to the station side communication device;
First optical input means for inputting an optical signal from the station side communication device;
An output changing means for changing the intensity of the optical signal output from the first optical output means in accordance with a command instruction included in the optical signal from the station side communication device;
The station side communication device is:
Second optical output means for outputting an optical signal to the home side communication device;
Second optical input means for inputting an optical signal from the home-side communication device;
Performance value measuring means for measuring a performance value for evaluating the quality of the optical signal from the home side communication device;
An optical signal including a command command for evaluating the quality of the optical signal from the home side communication device based on the performance value and changing the intensity of the optical signal from the home side communication device according to the evaluation result An optical communication system comprising: an evaluation unit that outputs the second optical output unit to the home communication device. The optical communication system according to claim 1.
The home side communication device further comprises error correction coding means for performing error correction coding of a signal to be sent to the station side communication device,
The performance value measuring means of the station side communication device corrects the error of the signal from the home side communication device, and corrects the bit error rate, the number of correction bits that have corrected the error, and the uncorrectable codeword in which the error could not be corrected. An optical communication system comprising error correction decoding means for measuring at least one of a number, an error bit number, a code word error rate, an error frame number, and a frame error rate as the performance value. The optical communication system according to claim 2.
The performance value measuring means of the station side communication device,
Furthermore, round trip time measuring means for measuring a round trip time which is a time required for communication between the station side communication device and the home side communication device as the performance value,
Signal strength measuring means for measuring the signal strength from the home side communication device as the performance value,
The evaluation unit of the station side communication apparatus is configured to calculate 2 out of the performance value measured by the error correction decoding unit, the round trip time measured by the round trip time measurement unit, and the signal strength measured by the signal strength measurement unit. The optical communication system characterized by evaluating the quality of the optical signal from the said home side communication apparatus using two or more. The optical communication system according to any one of claims 1 to 3,
The output changing means of the home side communication device, when establishing a link with the station side communication device, increases the strength of the registration request signal for link establishment until a registration permission signal is received from the station side communication device. When the registration request signal is repeatedly output from the first optical output unit to the station side communication device while gradually increasing, and the registration permission signal is received from the station side communication device, the first optical output unit Output a reception confirmation signal from the station side communication device,
The evaluation unit of the station side communication device causes the second optical output unit to output a registration permission signal to the home side communication device when it is determined that the quality of the optical signal from the home side communication device is good. An optical communication system. The optical communication system according to any one of claims 1 to 4,
The evaluation means evaluates the quality of the optical signal from the home-side communication device by comparing the performance value with a corresponding threshold set in advance, and the home-side in a direction in which the quality of the optical signal is improved. An optical communication system, wherein the command command for changing the intensity of an optical signal from a communication device is generated. In the home side communication device connected to the station side communication device through the transmission path,
Optical output means for outputting an optical signal to the station side communication device;
An optical input means for inputting an optical signal from the station side communication device;
Output changing means for changing the intensity of the optical signal output from the light output means,
The output changing means receives the optical signal output from the station side communication device according to the evaluation result of the quality of the optical signal input from the home side communication device to the station side communication device. A home-side communication apparatus characterized by changing the intensity of an optical signal output from the optical output means in accordance with a command instruction included in the signal. In the station side communication device connected to the home side communication device via the transmission path,
Optical output means for outputting an optical signal to the home-side communication device;
Optical input means for inputting an optical signal from the home side communication device;
Performance value measuring means for measuring a performance value for evaluating the quality of the optical signal from the home side communication device;
An optical signal including a command command for evaluating the quality of the optical signal from the home side communication device based on the performance value and changing the intensity of the optical signal from the home side communication device according to the evaluation result And a station side communication device comprising: an evaluation unit that outputs the light output unit to the home side communication device. A transmission step in which the home-side communication device outputs an optical signal to the station-side communication device connected via the transmission path;
A performance value measuring step in which the station side communication device measures a performance value for evaluating signal quality based on an optical signal from the home side communication device;
The station side communication device evaluates the quality of the optical signal from the home side communication device based on the performance value, and changes the intensity of the optical signal from the home side communication device according to the evaluation result An evaluation step of outputting an optical signal including a command command to the home-side communication device;
An optical communication method comprising: an output changing step in which the home side communication device changes the intensity of an optical signal output from the own device in accordance with a command command included in the optical signal from the station side communication device.

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