JP4355009B2 - Optical transceiver circuit - Google Patents

Description

  The present invention is used in an optical transmission system such as a passive optical network (PON) system that transmits a data signal through an optical fiber. In particular, the present invention relates to a technique for controlling the operating characteristics of PMD when an optical data signal is transmitted and received in an optical transceiver circuit.

  Conventionally, as an optical transmission system that enables high-speed data transmission, a passive optical network (PON) system that time-multiplexes packets of data signals for each subscriber is known. FIG. 6 shows this configuration.

  In the PON system, a plurality of home side devices (ONUs) 102-1 to 102-n are connected to one station side device (OLT) 101 via a passive device such as an optical coupler 103. Reference numeral 104 denotes an optical fiber. Upstream burst signals (packet data) from the respective home side devices 102-1 to 102-n are time-multiplexed and reach the station side device 101.

  In data transmission using such a burst signal, there is a period during which no burst signal exists (no signal period). Since the removal of noise in the no-signal period is necessary to avoid malfunction of the discriminator of the optical receiving circuit in the station side device 101, for example, as in the technique disclosed in Patent Document 1, There is a technique in which signal input to the discriminator or the like of the optical receiving circuit is interrupted during the no-signal period and signal input to the discriminator or the like is permitted when the head of the burst signal is detected.

JP 2007-5968 A

  The technique proposed by Patent Document 1 is a configuration in which input signal light power detection is autonomously performed using burst head detection means. However, since power detection is performed autonomously after receiving an input signal, it takes time to detect the power. In addition, in order to ensure the accuracy of burst head detection, it is necessary to ensure a certain length for the preamble length and the interframe length, which is a constraint for improving the throughput.

  The present invention has been made under such a background, and an object thereof is to provide an optical transmission / reception circuit capable of converting an input optical signal (received signal) into a stable electric signal at high speed. . It is another object of the present invention to provide an optical transmission / reception circuit capable of improving throughput by shortening a preamble length and an interframe length.

The present invention relates to a PMD (Physical Medium Dependent) that transmits and receives an optical signal, and a PMA (Physical Medium Dependent) that performs multiplexing and demultiplexing of an optical signal and also encodes and decodes an optical signal.
Attachment) / PCS (Physical Coding Sub layer) and MAC (Media Access Control) for transmitting and receiving frame signals, and between PMD and PMA / PCS and between PMA / PCS and MAC This is an optical transmission / reception circuit that transmits and receives data signals.

  Here, the present invention is characterized in that the MAC generates a control signal based on the means for holding information on the characteristics of the next frame received from the higher layer, and the control signal. Means for transmitting to the PMD via the PMA / PCS, the PMD changing reception characteristics based on the control information transmitted from the MAC via the PMA / PCS, and a received signal And a means for transmitting the characteristic information to the MAC via the PMA / PCSA. The MAC stores the characteristic information and a frame to be received next held in the holding means. Means for generating the control signal based on the result of comparison with the characteristic information is provided.

  According to this, since the characteristic of the next frame to be received is known in advance, the frame can be received with the reception characteristic that matches the characteristic in advance. Therefore, it is not necessary to determine the reception characteristics after detecting the head of the frame, and the input optical signal (reception signal) can be converted into a stable electric signal at a high speed. Since there is no need to secure a predetermined length for preamble detection or interframe length for head detection, these can be shortened to improve throughput.

  It is assumed that the characteristics of the next frame to be received are stored in advance in the upper layer. Or, it is assumed that learning is performed in a higher layer from past observation results. The present invention is based on the premise that such processing is performed in the upper layer. However, such processing in the upper layer can be easily inferred from the function of the processor or the like. Not added to requirements. The present invention is characterized in that such processing in the upper layer is introduced into processing in the lower layer.

  For example, the generating means lowers the reception amplification gain when the received signal power obtained from the characteristic information is larger than the received signal power obtained from the held characteristic information of the next received frame, and the characteristic When the received signal power obtained from the information is smaller than the received signal power obtained from the held information on the characteristics of the next frame to be received, the control signal is generated so as to increase the reception amplification gain.

  According to this, after receiving the characteristics of the next frame to be received from the upper layer, even if the reception characteristics change, the reception characteristics of the actually received frame are detected, and the detected reception characteristics are notified in advance. Since the reception amplification gain can be controlled according to the comparison result with the received reception characteristics, it is possible to respond quickly to changes in the reception characteristics.

  Further, the PMD may include means for changing transmission characteristics based on the control information. For example, if the condition of the transmission path is a situation where the reception amplification gain must be controlled to be high, it can be predicted that the signal transmitted by the own apparatus will also be greatly attenuated. Therefore, in such a case, the output of the signal transmitted by the own apparatus is increased. On the other hand, if the condition of the transmission path is a situation in which the reception amplification gain must be controlled to be low, it can be predicted that the signal transmitted by the own apparatus will not be greatly attenuated. Therefore, in such a case, the output of the signal transmitted by the own apparatus is reduced.

  Further, the configuration of the PMD will be specifically described. The PMD includes a photodiode that converts a received signal into a current signal, a transimpedance amplifier circuit that receives the current signal and converts it into a voltage signal, and the voltage signal. An amplitude limiting amplifier circuit that converts the amplitude of the signal into a voltage signal limited to a constant value, and a clock / data recovery circuit that extracts a clock from the voltage signal and performs data retiming and reproduction, the amplitude limiting amplification The reception characteristic can be controlled by the circuit changing the characteristic based on the control signal from the PMA / PCS.

  According to this, it is advantageous that the amplification characteristic of the amplitude limiting amplifier circuit can be controlled when the amplitude of the input optical signal varies greatly from frame to frame.

  Further, the transimpedance amplifier circuit can control the reception characteristics by changing the characteristics based on the control signal from the PMA / PCS.

  This has the advantage that the amplification characteristic of the transimpedance amplifier circuit can be controlled when the optical power of the input optical signal varies greatly from frame to frame.

  Also, the reception characteristic can be controlled by changing the characteristic based on the control signal from the PMA / PCS by the amplitude limiting amplifier circuit or the transimpedance amplifier circuit.

  According to this, when a sufficient amplification characteristic cannot be realized by the transimpedance amplifier circuit, the shortage can be compensated by the amplitude limit amplifier circuit. Therefore, the control range of the amplification characteristic can be widened.

  The present invention can also be viewed from the viewpoint of a reception characteristic control method. That is, the present invention is a reception characteristic control method performed by the optical transmission / reception circuit of the present invention. The characteristic of the present invention is that the MAC receives information on characteristics of a frame received next from a higher layer. The control signal is generated based on the information, the control signal is transmitted to the PMD via the PMA / PCS, and the PMD is transmitted from the MAC via the PMA / PCS. The reception characteristic is changed based on the information, the signal characteristic of the received signal is detected, and the characteristic information is transmitted to the MAC via the PMA / PCS, and the MAC is next stored with the characteristic information. The control signal is generated based on the result of comparison with the information on the characteristics of the received frame.

  For example, when generating the control signal, the reception amplification gain is lowered when the received signal power obtained from the characteristic information is larger than the received signal power obtained from the characteristic information of the next received frame. When the received signal power obtained from the characteristic information is smaller than the received signal power obtained from the held characteristic information of the next received frame, the control signal is generated so as to increase the reception amplification gain.

  Further, as the PMD changes the reception characteristics based on the control information, the transmission characteristics can also be changed.

  According to the present invention, an input optical signal can be converted into a stable electrical signal at high speed. Further, since there is no need to detect the burst head, the preamble length and the interframe length can be shortened, and the throughput can be improved.

(Example of optical transceiver circuit)
The configuration of the optical transmission / reception circuit according to the embodiment of the present invention will be described with reference to FIG. FIG. 1 is an overall configuration diagram of an optical transmission / reception circuit according to this embodiment.

  As shown in FIG. 1, the optical transmission / reception circuit according to the present embodiment transmits / receives a frame signal to / from a PMD 10 that transmits / receives an optical signal, a PMA / PCS 20 that performs multiplexing / demultiplexing and performs encoding / decoding. MAC 30 to be configured. Data signals are transmitted and received between the PMD 10 and the PMA / PCS 20 and between the MAC 30 and the PMA / PCS 20.

  The MAC 30 receives information on the power of the optical input signal of the frame from the upper layer as information on the characteristics of the next frame to be transmitted and received, and stores this information. Then, this information is transmitted to the PMA / PCS 20 as a control signal C3.

  The PMA / PCS 20 transmits this information to the PMD 10 as a control signal C1.

  The PMD 10 changes the reception amplification gain and the transmission signal power based on the control information C1 from the PMA / PCS 20.

  Specifically, the reception amplification gain is lowered when information indicating that the power of the optical input signal is high, and the reception amplification gain is increased when information indicating that the power of the optical input signal is low is received. Furthermore, the transmission signal power is reduced when information indicating that the power of the optical input signal is high, and the transmission signal power is increased when information indicating that the power of the optical input signal is low is received.

  The PMD 10 detects the input optical signal (reception signal) power as the signal characteristic of the reception signal, and transmits this characteristic information to the PMA / PCS 20 as the control signal C2.

  The PMA / PCS 20 transmits this characteristic information to the MAC 30 as the control signal C4.

  The MAC 30 stores the current reception signal characteristic, compares it with the next reception signal characteristic, and generates a control signal C3 including information for changing the reception amplification gain of the PMD 10.

  Specifically, the reception amplification gain is lowered when the received signal power is larger than the current stored value, and the reception amplification gain is increased when the received signal power is smaller than the current stored value.

(First Example of PMD)
The configuration of the PMD 10 of the first embodiment is shown in FIG. The PMD 10 includes a photodiode 11 that converts an input optical signal (received signal) into a current signal, a transimpedance amplifier circuit 12 that receives the current signal and converts it into a voltage signal, and the amplitude of the voltage signal is limited to a certain level. An amplitude limiting amplifier circuit 13 for converting into a voltage signal, and a clock / data recovery circuit 14 for extracting a clock from the voltage signal and performing data retiming and reproduction.

  The PMD 10 of the present embodiment is characterized in that the amplitude limiting amplifier circuit 13 switches the gain characteristic based on the control signal C1 from the PMA / PCS 20.

  The operation of the PMD 10 of this embodiment will be described with reference to the flowchart of FIG. The PMD 10 receives the control signal C1 from the PMA / PCS 20 (ST1), and when the control signal C1 is in the autonomous mode (ST2), the gain of the amplitude limiting amplifier circuit 13 is based on the input signal power detected by the PMD 10. Is set (gain a) (ST3), and when the control signal C1 is in the system control mode (ST2), the gain of the amplitude limiting amplifier circuit 13 is set (gain) based on the gain signal of the control signal C1 (ST4). b or c, b ≠ c) (ST5 or ST6).

  The present embodiment has an advantage that the amplification characteristic of the amplitude limiting amplifier circuit 13 can be controlled when the amplitude of the input optical signal varies greatly from frame to frame.

(Second embodiment of PMD)
The configuration of the PMD 10 of the second embodiment is shown in FIG. The basic configuration is the same as that of the first embodiment, but this embodiment is different from the first embodiment in that the transimpedance amplifier circuit 12 is controlled by the control signal C1.

  The output amplitude and the noise characteristic can be controlled by controlling the amplitude limiting amplifier circuit 13 as in the first embodiment, but the transimpedance amplifier circuit 12 is controlled as in the second embodiment. Thus, the dynamic range when controlling the output amplitude and the noise characteristic can be increased.

  This embodiment has an advantage that the amplification characteristic of the transimpedance amplifier circuit 12 can be controlled when the optical power of the input optical signal varies greatly from frame to frame.

(Third embodiment of PMD)
The configuration of the PMD 10 of the third embodiment is shown in FIG. This embodiment is an embodiment that can incorporate the advantages of both the first and second embodiments. That is, the control by the amplitude limiting amplifier circuit 13 and the control by the transimpedance amplifier circuit 12 can be used in combination.

  For example, when the transimpedance amplifier circuit 12 cannot realize sufficient amplification characteristics, the shortage can be compensated for by the amplitude limit amplifier circuit 13.

  The present embodiment is advantageous in that the control range of the amplification characteristic can be widened.

  INDUSTRIAL APPLICABILITY The present invention can convert an input optical signal into a stable electrical signal at high speed, and can be used for speeding up an optical transmission system. Further, since there is no need to detect the burst head, the preamble length and the interframe length can be shortened, which can be used to improve the throughput.

1 is an overall configuration diagram of an optical transmission / reception circuit according to the present embodiment. The block diagram of PMD of a 1st Example. The flowchart which shows operation | movement of PMD of a 1st Example. The block diagram of PMD of a 2nd Example. The block diagram of PMD of a 3rd Example. The block diagram of a PON system.

Explanation of symbols

10 PMD
11 Photodiode 12 Transimpedance Amplifier 13 Amplitude Limiting Amplifier 14 Clock / Data Recovery Circuit 20 PMA / PCS
30 MAC
101 Station side equipment (OLT)
102-1 to 102-n Home unit (ONU)
103 optical coupler 104 optical fibers C1 to C4 control signals R1, R2 received signals S1, S2 transmitted signals

Claims (9)

PMD (Physical Medium Dependent) for transmitting and receiving optical signals and PMA (Physical Medium Attachment) / PCS (Physical Coding Sub layer) for multiplexing and demultiplexing optical signals and encoding and decoding optical signals And a MAC (Media Access Control) that transmits and receives frame signals, and an optical transmission and reception circuit that transmits and receives data signals between the PMD and the PMA / PCS and between the PMA / PCS and the MAC. ,
The MAC is
Means for holding information on the characteristics of the next frame received from the higher layer;
Means for generating a control signal based on the information and transmitting the control signal to the PMD via the PMA / PCS;
The PMD is
Means for changing reception characteristics based on the control information transmitted from the MAC via the PMA / PCS;
Means for detecting a signal characteristic of a received signal and transmitting the characteristic information to the MAC via the PMA / PCS;
The MAC includes means for generating the control signal based on a result of comparing the characteristic information with the characteristic information of a frame to be received next held in the holding means. .   The generating means lowers the reception amplification gain when the received signal power obtained from the characteristic information is larger than the received signal power obtained from the characteristic information of the next received frame, and from the characteristic information 2. The optical transmission / reception circuit according to claim 1, wherein when the received signal power obtained is smaller than the received signal power obtained from the held characteristic information of the next received frame, the control signal is generated so as to increase the reception amplification gain. .   The optical transmission / reception circuit according to claim 1, wherein the PMD includes means for changing transmission characteristics based on the control information. The PMD is
A photodiode that converts a received signal into a current signal;
A transimpedance amplifier that receives this current signal and converts it into a voltage signal;
An amplitude limiting amplifier circuit that converts the amplitude of the voltage signal into a voltage signal that is constant, and
A clock / data recovery circuit that extracts a clock from this voltage signal and performs data retiming and recovery,
The optical transmission / reception circuit according to claim 1, wherein the amplitude limiting amplifier circuit changes characteristics based on a control signal from the PMA / PCS. The PMD is
A photodiode that converts a received signal into a current signal;
A transimpedance amplifier that receives this current signal and converts it into a voltage signal;
An amplitude limiting amplifier circuit that converts the amplitude of the voltage signal into a voltage signal that is constant, and
A clock / data recovery circuit that extracts a clock from this voltage signal and performs data retiming and recovery,
The optical transmission / reception circuit according to claim 1, wherein the transimpedance amplifier circuit changes characteristics based on a control signal from the PMA / PCS. The PMD is
A photodiode that converts a received signal into a current signal;
A transimpedance amplifier that receives this current signal and converts it into a voltage signal;
An amplitude limiting amplifier circuit that converts the amplitude of the voltage signal into a voltage signal that is constant, and
A clock / data recovery circuit that extracts a clock from this voltage signal and performs data retiming and recovery,
The optical transmission / reception circuit according to any one of claims 1 to 3, wherein the amplitude limiting amplifier circuit or the transimpedance amplifier circuit changes characteristics based on a control signal from the PMA / PCS. A PMD that transmits and receives an optical signal; a PMA / PCS that multiplexes and demultiplexes an optical signal and encodes and decodes an optical signal; and a MAC that transmits and receives a frame signal. In a reception characteristic control method performed by an optical transmission / reception circuit that transmits / receives data signals to / from PMA / PCS and between the PMA / PCS and the MAC
The MAC holds information on the characteristics of the next frame received from the higher layer, generates a control signal based on the information, transmits the control signal to the PMD via the PMA / PCS,
The PMD changes reception characteristics based on the control information transmitted from the MAC via the PMA / PCS, detects signal characteristics of a received signal, and transmits the characteristic information via the PMA / PCS. Send to MAC,
The reception characteristic control method, wherein the MAC generates the control signal based on a result of comparing the characteristic information with the held characteristic information of the next frame to be received.   When generating the control signal, when the received signal power obtained from the characteristic information is larger than the received signal power obtained from the held characteristic information of the next received frame, the reception amplification gain is lowered, 8. The control signal is generated so that a reception amplification gain is increased when reception signal power obtained from characteristic information is smaller than reception signal power obtained from characteristic information of the held next received frame. Reception characteristics control method.   The reception characteristic control method according to claim 7 or 8, wherein the PMD changes the transmission characteristic as the reception characteristic is changed based on the control information.

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