JP2011249863A - Master station device and optical signal receiving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a master station device capable of obtaining excellent receiving sensitivity at each transmission rate in a PON system in which a plurality of different transmission rates coexist.SOLUTION: A master station device comprises: a gain adjusting unit 16 for adjusting gain of TIA 12; a gain adjusting unit 17 for 10G; a memory 30 for storing an identification number, a transmission rate, a reception voltage and a set voltage of each slave station device; and control means 15 for determining whether or not using the gain adjusting unit 17 for 10G for each slave station device based on the transmission rate of each slave station device stored in the memory 30, searching the set voltage of each slave station during training communication and storing it in the memory 30, reading the set voltage from the memory 30 during normal communication, and applying the read set voltage to the gain adjusting unit 16 or the gain adjusting unit 16 and the gain adjusting unit 17 for 10G.

Description

  The present invention relates to a master station apparatus capable of receiving optical signals at a plurality of different transmission rates.

  With the spread of the Internet and the expansion of broadband services such as high-definition video distribution / exchange to the general subscriber area (subscriber), the number of subscribers and data traffic in the subscriber communication network have exploded. Has increased. In order to meet such demands for large-capacity communications in subscriber systems, full-scale market development of FTTH (Fiber to the home) service that enables communications using broadband optical signals via optical fibers has been started. Yes.

  As an example of the FTTH system, there is a PON (Passive Optical Networks) system. In the PON system, a single optical fiber and an optical coupler are used as a transmission path, and a master station device (OLT: Optical Line Terminal) accommodates a plurality of slave station devices (ONU: Optical Network Unit). In the PON system, a plurality of slave station devices share one master station device, so that the number of master station devices can be reduced. For this reason, the PON system is economically superior and is being introduced as the main infrastructure of the FTTH system.

  In the PON system, the master station device needs to adjust the received signals from the slave station devices having different distances and signal outputs to the optimum reception level at high speed. Patent Document 1 below discloses a technique for performing AGC (Auto Gain Control) gain adjustment at a high speed when a received signal is amplified to an optimum level. Specifically, the master station device stores a set voltage to be applied to the gain adjustment circuit in a memory and holds it as a table in order to obtain an AGC gain according to the reception level of the optical signal received from each slave station device. . When there is a communication request from an arbitrary slave station device, the master station device reads the set voltage from the table in the memory and applies it to the gain adjustment circuit to adjust it to the optimum AGC gain. As a result, the master station device can ensure good reception sensitivity.

  In recent years, in the PON system, standardization activities relating to the 10 Gbps-PON system have been actively performed with the aim of further increasing the bandwidth of the existing 1 Gbps-PON system. As an operation mode of the 10 Gbps-PON system, generally, a system mixed with the existing 1 Gbps has been proposed, and development of a device corresponding to the 1G / 10G mixed system is being promoted. Here, in the PON system in which 1G / 10G coexists (mixed), the master station device changes the optimum reception level according to the transmission rate of the optical signal received from the slave station device in order to ensure good reception sensitivity. To do. In order to ensure good reception sensitivity at each transmission rate, the master station apparatus needs to change the optimum gain according to the transmission rate from the characteristics of the amplifier determined by the GB product (Gain Bandwidth product).

JP 2005-020417 A

  However, according to the above conventional technique, the master station apparatus determines the AGC gain setting voltage only from the received light level of the received optical signal (packet), and controls the AGC gain based on this setting voltage. Yes. Therefore, in a PON system in which a plurality of different transmission rates are mixed, the master station device can determine an optimal AGC gain setting voltage at a specific transmission rate and can ensure good reception sensitivity. At other transmission rates, the optimum AGC gain setting voltage cannot be determined, and there is a problem that good reception sensitivity cannot be secured.

  The present invention has been made in view of the above, and it is an object of the present invention to obtain a master station device capable of obtaining good reception sensitivity at each transmission rate in a PON system in which a plurality of different transmission rates are mixed. And

  In order to solve the above-described problems and achieve the object, the present invention provides a PON system in which a high-speed optical signal having a high transmission speed and a low-speed optical signal slower than the high-speed optical signal are mixed. A light receiving means for photoelectrically converting an optical signal received from a slave station apparatus and outputting an electric signal; an amplifying means for amplifying the electric signal after photoelectric conversion; An average value detecting means for detecting an average value of the voltage of the amplified electric signal in a predetermined period and using the detected average value as a received voltage; and a function for adjusting the gain of the amplifying means based on a predetermined applied voltage. A first gain adjusting means having the same function as the first gain adjusting means, arranged in parallel with the first gain adjusting means, and a high-speed optical signal from a slave station device that performs communication by a high-speed optical signal When you receive the first A second gain adjusting means used together with the gain adjusting means, an identification number of the slave station device, a transmission rate, a received voltage, and the first gain adjusting means or the first gain when the received voltage is obtained; Based on the transmission speed stored in the storage means, storage means for storing the set voltage, which is the voltage applied to the gain adjustment means and the second gain adjustment means, for each slave station device, It is determined whether or not the second gain adjusting unit is used for each slave station device, and a set voltage is obtained for each slave station device during training communication, stored in the storage unit, and set from the storage unit during normal communication And a control means for reading the voltage and applying the read set voltage to the first gain adjusting means or the first gain adjusting means and the second gain adjusting means.

  According to the present invention, in a PON system in which a plurality of different transmission rates are mixed, there is an effect that good reception sensitivity can be obtained at each transmission rate.

FIG. 1 is a diagram illustrating a configuration example of a PON system in which different transmission rates of 1G / 10G are mixed. FIG. 2 is a diagram illustrating a PON system that performs training communication. FIG. 3 is a diagram illustrating a configuration example of the OLT receiving unit. FIG. 4 is a flowchart showing the operation of the 1G / 10G master station device in the training mode. FIG. 5 is a flowchart showing the operation of the 1G / 10G master station device in the self-running mode.

  Embodiments of a master station apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment.
FIG. 1 is a diagram illustrating a configuration example of a PON system in which different transmission rates of 1G / 10G are mixed. The PON system includes a 1G / 10G master station device (OLT) 1, a 1G slave station device (ONU) 2, a 10G slave station device (ONU) 3, and a 1G slave station device (ONU) 4. . The 1G / 10G master station device 1 is a master station device capable of receiving a dual rate of 1G / 10 Gbps. The 1G slave station devices 2 and 4 are slave station devices dedicated to 1 Gbps transmission / reception. The 10G slave station device 3 is a slave station device dedicated to 10 Gbps transmission / reception. The packet 5 is an upstream packet signal with different transmission power and transmission rate transmitted from each slave station device.

  Each slave station device transmits packet data to the 1G / 10G master station device 1 as a burst optical signal that is intermittent in time at the respective transmission rates. Here, the packet 5 received by the 1G / 10G master station device 1 is the 1G / 10G master station device due to the transmission power of each slave station device and the transmission path loss from each slave station device to the 1G / 10G master station device 1. The packet data of different power is reached when 1 is reached.

  Next, an outline of the present embodiment will be described. FIG. 2 is a diagram illustrating a PON system that performs training communication. The configuration of the PON system is the same as that in FIG. The 1G / 10G master station device 1 includes an OLT receiving unit 10, an AD (Analogue to Digital) / DA (Digital to Analogue) conversion control unit 20, and a memory 30.

  The OLT receiver 10 is an optical signal receiver that adjusts to an optimum reception gain for each transmission rate and obtains good reception sensitivity when a plurality of different transmission rates (transmission speeds) coexist. The optimum reception gain for each transmission rate means a gain for obtaining each output level because the optimum output level differs depending on the transmission rate. This is because, when there are a plurality of transmission rates, if the output level of another transmission rate is matched with the optimum output level for one of the transmission rates, good reception sensitivity cannot be obtained at the other transmission rates. Detailed operation will be described later.

  The AD / DA conversion control unit 20 performs AD conversion on the set voltage (gain adjustment voltage) recorded in the memory 30 by the OLT receiver 10, and performs DA conversion when the OLT receiver 10 reads the set voltage from the memory 30. Do.

  The memory 30 includes a table 31 and is a storage unit for storing the set voltage set by the OLT receiving unit 10 for each slave station device.

  First, the 1G / 10G master station device 1 performs training communication with each slave station device in order to determine the optimum gain of each slave station device. Each slave station apparatus that has received a request from the 1G / 10G master station apparatus 1 transmits training data (6 to 8) having a packet length sufficient to determine the gain. In the 1G / 10G master station device 1 that has received the training data 6 to 8, the OLT receiving unit 10 adjusts the gain to an optimum value. The OLT receiving unit 10 performs AD conversion of the set voltage used when the gain is adjusted by the AD / DA conversion control unit 20 and stores the converted voltage in the memory 30. The memory 30 stores the contents shown in the table 31 for each slave station device.

  The table 31 includes an ONU identification number, a transmission rate (1G / 10G), a reception power (Pf), and a set voltage. The ONU identification number is a number for identifying a slave station device connected to the PON system. The transmission rate (1G / 10G) indicates the transmission rate of optical communication performed by the connected slave station device. Here, there are two types of 1 Gbps and 10 Gbps. The transmission rate can be recognized by the 1G / 10G master station device 1 when each slave station device connects to the PON system. The reception power (Pf) indicates the reception power of the reception packet. The set voltage is a voltage set in order to obtain an optimum gain for each slave station device based on processing described later. During actual operation, the 1G / 10G master station device 1 adjusts the optimum gain for each slave station device based on the information held in the table 31, and receives packets from each slave station device.

  Next, the configuration of the OLT receiving unit 10 of the 1G / 10G master station device 1 will be described. FIG. 3 is a diagram illustrating a configuration example of the OLT receiving unit 10. The OLT receiving unit 10 includes a light receiving element 11, a TIA (Trans Impedance Amplifier) 12, an average value detecting unit 13, a selector 14, a control unit 15, a gain adjusting unit 16, a 10G gain adjusting unit 17, Voltage follower circuits 18 and 19.

  The light receiving element 11 receives an optical signal (packet) from each slave station device, photoelectrically converts it, and outputs an electric signal (current). The TIA 12 converts the current after photoelectric conversion into a voltage, and outputs the voltage after amplification. The average value detection unit 13 detects the average value of received power that is an output from the TIA 12.

  Based on the mode switching signal from the control unit 15, the selector 14 determines the optimum gain of each child station device from the training mode when determining the optimum gain of each child station device or the set voltage information stored in the memory. The output destination from the average value detection unit 13 is switched depending on the self-running mode to be adjusted.

  The control unit 15 controls the mode switching of the selector 14 and the switching of the 1G / 10G mode of the 10G gain adjustment unit 17. Further, in the training mode, a voltage is applied to the gain adjusting unit 16 or the gain adjusting unit 16 and the 10G gain adjusting unit 17 according to the reception power from the selector 14, and in the free-running mode, from the table 31 provided in the memory 30. The set voltage is read out and applied to the gain adjusting unit 16 or the gain adjusting unit 16 and the 10G gain adjusting unit 17.

  The gain adjusting unit 16 functions as a feedback resistor that determines the gain of the TIA 12. As a configuration of the gain adjusting unit 16, for example, there is a method of changing a resistance value between a source and a drain by changing a gate voltage applied to an FET (Field Effect Transistor), but is not limited thereto. .

  The 10G gain adjustment unit 17 is arranged in parallel to the gain adjustment unit 16 with respect to the TIA 12, and functions as a 10G feedback resistor for widening the band when a 10G signal is input. The specific configuration is the same as that of the gain adjusting unit 16.

  The voltage follower circuit 18 holds a set voltage stored in the memory 30 via the AD / DA conversion control unit 20. The voltage follower circuit 19 holds a set voltage read from the memory 30 via the AD / DA conversion control unit 20.

  Next, the operation of the 1G / 10G master station device 1 in the training mode, which is a mode for obtaining the optimum gain of the TIA 12 for each slave station device, will be described. FIG. 4 is a flowchart showing the operation of the 1G / 10G master station device 1 in the training mode. First, in the 1G / 10G master station device 1, training is performed at an arbitrary timing (every time, every packet, etc.) based on control of an OLT control unit (not shown) that controls the entire 1G / 10G master station device 1. A communication request is transmitted to a slave station apparatus (here, ONU # X) having a predetermined identification number (step S1).

  At this time, the OLT receiving unit 10 switches the mode of the selector 14 to the training mode based on the mode switching signal transmitted from the control unit 15 (step S2). Specifically, the selector 14 switches the reception power from the average value detection unit 13 to be output to the control unit 15 via the left path.

  Next, the OLT receiving unit 10 receives the training data from the ONU #X that has received the training communication request (step S3). Specifically, in the OLT receiving unit 10, the light receiving element 11 receives the training data from the ONU # X, and outputs the training data to the TIA 12 after photoelectric conversion. Here, the current is output. The TIA 12 amplifies the signal after photoelectric conversion, and outputs the amplified signal to the subsequent stage AMP and the average value detection unit 13. At this time, the voltage is output by current-voltage conversion. The average value detection unit 13 detects the average value of received power of the amplified packets in a predetermined period and outputs the average value to the selector 14. The average value may be calculated from a plurality of reception powers sampled from within a predetermined period, or may be a reception power at a half time of the predetermined period.

  Since the selector 14 switches to the training mode path based on the control of the control unit 15, the input reception power is output to the control unit 15. The control unit 15 applies a voltage to the gain adjustment unit 16 according to the received reception power. The control unit 15 may apply an equivalent voltage based on the value of the reception power, or may apply a different voltage depending on the circuit configuration of the gain adjustment unit 16.

  At this time, the control unit 15 switches the mode of the selector 14 and the 1G / 10G select signal based on the transmission rate (1G / 10G) of the slave station apparatus that has requested training communication to the 10G gain adjustment unit 17. Send. The control unit 15 can grasp the transmission rate of the slave station device by referring to the table 31.

  The 10G gain adjusting unit 17 switches Enable / Disable based on the 1G / 10G select signal. For example, when the transmission rate of ONU # X that requested the training communication is 10G (step S4: Yes), the 10G gain adjustment unit 17 sets Enable (step S5). That is, in the case of a 10G slave station device, a circuit configuration using the 10G gain adjustment unit 17 is adopted. On the other hand, when the transmission rate of ONU # X that requested the training communication is 1G (step S4: No), the 10G gain adjustment unit 17 sets it to Disable (step S6). That is, in the case of the 1G slave station device, the circuit configuration does not use the 10G gain adjustment unit 17.

  In the above state, the OLT receiving unit 10 performs feedback control based on the magnitude of the received power via the selector 14 and the control unit 15, and determines an optimum gain for the TIA 12 to perform feedback control. Then, the control unit 15 stores the voltage applied by the control unit 15 at the determined optimum gain as a set voltage in the memory 30 through AD conversion processing by the voltage follower circuit 18 and the AD / DA conversion control unit 20. (Step S7). The above processing is performed for each slave station device, and the 1G / 10G master station device 1 stores the set voltage for each slave station device in the form of a table 31 shown in FIG. The control unit 15 also stores the received power output from the selector 14 in the table 31 together.

  In the case of a PON system in which 1G / 10G is mixed, the optimum output level in the TIA 12 varies depending on the transmission rate, and therefore the optimum gain also varies depending on the transmission rate. As shown in FIG. 3, in the case of 10G, the OLT receiving unit 10 adds resistance in parallel, so that the feedback resistance is reduced and the amount of amplification can be reduced. That is, the received power after amplification is greater at 1G than at 10G.

  As in the prior art, when the set voltage is determined only by looking at the reception power of the received packet, it cannot be determined from the received packet only whether the packet is 1G / 10G. Therefore, the optimum gain (output level) according to the transmission rate cannot be obtained. For example, in the case of an optimum gain for a 1G transmission rate, a good reception sensitivity can be ensured with 1G, but an optimum gain cannot be ensured with a transmission rate of 10G.

  In the present embodiment, in the training mode, the 1G / 10G master station device 1 stores known information (child slave devices) stored in the table 31 so that an optimum gain (output level) is obtained for each transmission rate. By using the transmission rate information for each station device, the 10G gain adjusting unit 17 is appropriately used. Thereby, even when there are a plurality of different transmission rates, the 1G / 10G master station device 1 can obtain an optimum gain for each transmission rate.

  Next, the operation of the 1G / 10G master station device 1 during normal operation (self-running mode) will be described. FIG. 5 is a flowchart showing the operation of the 1G / 10G master station device 1 in the self-running mode. First, in the 1G / 10G master station device 1, when the OLT receiving unit 10 receives a communication request from a slave station device (here, ONU # X) having a predetermined identification number (step S11), control is performed. The unit 15 reads the set voltage set in the slave station device having the identification number of the ONU # X from the memory 30 through the DA conversion process in the AD / DA conversion control unit 20.

  At this time, similarly to the training mode, the control unit 15 sends a 1G / 10G select signal to the 10G gain adjustment unit 17 based on the transmission rate (1G / 10G) of the slave station apparatus that has requested communication. Send. That is, when the transmission rate of the slave station apparatus that has requested communication is 10G, the 10G gain adjustment unit 17 is enabled, and when the transmission rate of the slave station apparatus that has requested communication is 1G, the gain adjustment unit 17 for 10G Is set to Disable.

  Then, the control unit 15 applies the read set voltage to the gain adjustment unit 16 or the gain adjustment unit 16 and the 10G gain adjustment unit 17 to set the TIA 12 to the optimum gain in the ONU # X (step). S12).

  In the 1G / 10G master station device 1, an OLT control unit (not shown) grants communication to the ONU #X that requested the training communication, and starts receiving a packet (step S13). Thereafter, as in the training mode, the light receiving element 11 receives the packet data from the ONU # X, and outputs the packet data to the TIA 12 after photoelectric conversion. The TIA 12 amplifies the signal after photoelectric conversion, and outputs the amplified signal to the subsequent stage AMP and the average value detection unit 13.

  In the OLT reception unit 10 of the 1G / 10G master station device 1, the average value detection unit 13 detects the average value of the reception power for the actually received packet (step S14). At this time, a mode switching signal in the self-running mode is input from the control unit 15 to the selector 14. The average value detection unit 13 inputs the detected average value of received power through the right path of the selector 14 to the memory 30 via the AD / DA conversion control unit 20, and the corresponding ONU # X in the table 31. The received power is stored in the column (step S15).

  The table 31 stores the relationship between the received power and the set voltage stored in the training mode for each slave station device. Here, when a difference is detected between the received power stored in the training mode and the received power detected and stored in the self-running mode, the control unit 15 may update the set voltage in the table 31. Furthermore, the control unit 15 may change the set voltage stored in association with the received power in the training mode based on the difference in received power, and use the changed set voltage for gain adjustment. For example, the received power stored in the training mode may be compared with the received power stored in the self-running mode, and the set voltage stored in the training mode may be changed according to the ratio of the two received powers.

  If the packet received at a certain point in time is the Nth packet while the self-running mode is continued, the reception power detected in the average value when the Nth packet is received and the reception power stored in the table 31. To the received power value of the Nth packet, to update the received power value stored in the table 31, and to update the set voltage when the N + 1th packet is received ( (Adjustment of optimum gain).

  As described above, in the present embodiment, in the PON system in which a plurality of different transmission rates are mixed, in the 1G / 10G master station device 1, the control unit 15 is optimal for the slave station devices having different transmission rates. In order to set the gain, during the training communication, when the transmission rate is 10 G (when the transmission speed is high), the TIA 12 amplifies the received light signal as compared with the case where the transmission rate is 1 G (when the transmission speed is low). In order to reduce the gain of 10G, a 10G gain adjusting unit 17 that is not used at 1G is inserted in parallel with the gain adjusting unit 16 with respect to the TIA 12. Then, the control unit 15 stores the voltage applied to the gain adjustment unit 16 or the gain adjustment unit 16 and the 10G gain adjustment unit 17 in the memory 30 as a set voltage when the optimum gain is obtained for each slave station device. . During normal communication, the control unit 15 reads the set voltage related to the slave station apparatus that requested communication from the table 31, and applies the set voltage to the gain adjustment unit 16, or the gain adjustment unit 16 and the 10G gain adjustment unit 17. It was decided. As a result, an optimum gain can be obtained for each transmission rate, and reception sensitivity at each transmission rate can be improved. In addition, the overhead time can be shortened and the AGC gain setting error at the time of continuous same sign signal input can be solved.

  Although the 10G gain adjustment unit 17 is used during normal communication, the present invention is not limited to this. For example, the control unit 15 converts the gain of the TIA 12 by the set voltage obtained in the training mode into a voltage value realized only by the gain adjustment unit 16 without using the 10G gain adjustment unit 17 and stores it in the table 31. You may keep it. In this case, since the 10G gain adjustment unit 17 is not used during normal communication, the control can be simplified.

  As described above, the optical signal receiving apparatus according to the present invention is useful for a PON system, and is particularly suitable for a PON system in which different transmission rates are mixed.

1 1G / 10G master station device 2, 4 1G slave station device 3 10G slave station device 10 OLT receiver 11 light receiving element 12 TIA
DESCRIPTION OF SYMBOLS 13 Average value detection part 14 Selector 15 Control part 16 Gain adjustment part 17 10G gain adjustment part 18, 19 Voltage follower circuit 20 AD / DA conversion control part 30 Memory 31 Table

Claims (10)

In a PON system in which a high-speed optical signal having a high transmission speed and a low-speed optical signal that is slower than the high-speed optical signal are mixed, a master station device that performs communication using an optical signal with a plurality of slave station devices,
A light receiving means for photoelectrically converting an optical signal received from the slave station device and outputting an electrical signal;
Amplifying means for amplifying the electric signal after photoelectric conversion;
An average value detecting means for detecting an average value of the voltage of the electric signal after amplification in a predetermined period, and using the detected average value as a reception voltage;
First gain adjusting means having a function of adjusting the gain of the amplifying means based on a predetermined applied voltage;
The first gain adjusting means has the same function, is arranged in parallel with the first gain adjusting means, and receives the high-speed optical signal from a slave station device that performs communication by a high-speed optical signal. A second gain adjusting means used together with the gain adjusting means;
It is applied to the first gain adjusting means or the first gain adjusting means and the second gain adjusting means when the slave station device identification number, transmission speed, received voltage, and the received voltage are obtained. Storage means for storing a set voltage, which is a set voltage, for each slave station device;
Based on the transmission speed stored in the storage means, for each slave station device, determine whether to use the second gain adjustment means, and obtain a set voltage for each slave station device during training communication Store in the storage means, read a set voltage from the storage means during normal communication, and apply the read set voltage to the first gain adjustment means or the first gain adjustment means and the second gain adjustment means Control means to
A master station device comprising: The control means includes
When confirming the speed of the optical signal performed by each slave station device based on the transmission speed of each slave station device stored in the storage means, and when communicating with a slave station device that performs communication by a high-speed optical signal, A select signal that is invalidated to the second gain adjusting means when transmitting a select signal that is valid to the second gain adjusting means and communicating with a slave station device that performs communication using a low-speed optical signal. Send,
The master station device according to claim 1. The control means includes
In training communication, the first gain adjusting means or the first gain adjusting means and the second gain adjusting means are received while receiving training data longer than the packet length during normal communication transmitted from the slave station device. In contrast, feedback control is performed by applying a voltage corresponding to the magnitude of the received voltage, and the applied voltage when the amplified signal voltage becomes constant is set as the set voltage, and the set voltage is received at this time. The process of storing in the storage means together with the voltage is performed for all connected slave station devices,
During normal communication, the set voltage of the slave station device that is the communication request transmission source is read from the storage unit, and the read set voltage is read from the first gain adjustment unit or the first gain adjustment unit and the second gain adjustment. Applying to the means to adjust the gain of the amplifying means;
The master station device according to claim 1, wherein the master station device is a master station device. The control means includes
When a difference is detected between the current received voltage and the received voltage stored in the storage means in the training communication during normal communication, the received voltage stored in the storage means is updated to the current received voltage. And updating the set voltage stored in the storage unit based on the ratio of the reception voltage before update and the reception voltage after update.
4. The master station apparatus according to claim 1, 2, or 3. The control means includes
When a difference is detected between the current received voltage during normal communication and the received voltage stored in the storage means in the training communication, the current received voltage is weighted, and after the weighting is performed Based on the received voltage and the received voltage stored in the storage means, the received voltage stored in the storage means is updated, and based on the ratio between the received voltage before the update and the updated received voltage, the stored voltage is stored. Update the set voltage stored in the means,
4. The master station apparatus according to claim 1, 2, or 3. In a PON system in which a high-speed optical signal having a high transmission speed and a low-speed optical signal that is slower than the high-speed optical signal are mixed, an optical signal receiving method for a master station apparatus that performs optical signal communication with a plurality of slave station apparatuses. And
The master station device is
A first gain adjusting means having a function of adjusting a gain when amplifying the electric signal after photoelectric conversion based on a predetermined applied voltage;
The first gain adjusting means has the same function, is arranged in parallel with the first gain adjusting means, and receives the high-speed optical signal from a slave station device that performs communication by a high-speed optical signal. A second gain adjusting means used together with the gain adjusting means;
It is applied to the first gain adjusting means or the first gain adjusting means and the second gain adjusting means when the slave station device identification number, transmission speed, received voltage, and the received voltage are obtained. Storage means for storing a set voltage, which is a set voltage, for each slave station device;
If you have
A light receiving step for photoelectrically converting an optical signal received from the slave station device and outputting an electrical signal;
An amplification step for amplifying the electrical signal after photoelectric conversion;
An average value detecting step of detecting an average value of the voltage of the electric signal after amplification in a predetermined period, and using the detected average value as a reception voltage;
A determination step of determining whether to use the second gain adjustment unit for each slave station device based on the transmission rate stored in the storage unit;
A training step of obtaining a set voltage for each slave station device during training communication and storing it in the storage means;
The set voltage is read from the storage means during normal communication, and when the determination step determines that the second gain adjustment means is not used, the read set voltage is applied to the first gain adjustment means. A normal communication step of applying the read set voltage to the first gain adjusting means and the second gain adjusting means when it is determined that the second gain adjusting means is used;
An optical signal receiving method comprising: In the determination step,
When confirming the speed of the optical signal performed by each slave station device based on the transmission speed of each slave station device stored in the storage means, and when communicating with a slave station device that performs communication by a high-speed optical signal, A select signal that is invalidated to the second gain adjusting means when transmitting a select signal that is valid to the second gain adjusting means and communicating with a slave station device that performs communication using a low-speed optical signal. Send,
The optical signal receiving method according to claim 6. In the training step,
While receiving training data longer than the packet length during normal communication transmitted from the slave station device, for the first gain adjusting means or the first gain adjusting means and the second gain adjusting means, Feedback control is performed by applying a voltage corresponding to the magnitude of the received voltage, and the applied voltage when the amplified signal voltage becomes constant is set as a set voltage, and the set voltage is stored together with the received voltage at this time The process stored in the means is performed for all connected slave station devices,
In the normal communication step,
The set voltage of the slave station device that is the communication request transmission source is read from the storage means, and the read set voltage is applied to the first gain adjusting means or the first gain adjusting means and the second gain adjusting means. Adjusting the gain when amplifying the electric signal after photoelectric conversion in the amplification step,
8. The optical signal receiving method according to claim 6, wherein the optical signal is received. further,
When a difference is detected between the current received voltage and the received voltage stored in the storage means in the training communication during normal communication, the received voltage stored in the storage means is updated to the current received voltage. And a storage means update step for updating the set voltage stored in the storage means based on the ratio between the reception voltage before update and the reception voltage after update,
The optical signal receiving method according to claim 6, 7 or 8. further,
When a difference is detected between the current received voltage during normal communication and the received voltage stored in the storage means in the training communication, the current received voltage is weighted, and after the weighting is performed Based on the received voltage and the received voltage stored in the storage means, the received voltage stored in the storage means is updated, and based on the ratio between the received voltage before the update and the updated received voltage, the stored voltage is stored. A storage means update step for updating the set voltage stored in the means;
The optical signal receiving method according to claim 6, 7 or 8.

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