JP2009296292A - Optical transmitter, optical transmission device, and control method of optical transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical transmitter in which the number of terminals can be reduced, by using one terminal in common for both a shutdown control signal (TxDisable) and an abnormal state detection signal (TxFault). <P>SOLUTION: The optical transmitter 3 includes an LD 4, an LD driving circuit 6, an APC circuit 7, a controller 8, an external supervisory control signal input/output terminal (g), and an output buffer 9. The output buffer 9 includes an input terminal, connected to the TxFault output terminal (b), and an output terminal which is pulled up to a predetermined voltage and connected to the TxDisable input terminal (a), and is connected to the external supervisory control signal input/output terminal (g). The controller 8 outputs TxFault, from the TxFault output terminal (b) to the output buffer 11; outputs a shutdown signal to the APC circuit 7 based upon input to the TxDisable input terminal (a); and outputs the TxFault to the external supervisory control signal input/output terminal (g), when a monitor value of a bias current exceeds a shutdown threshold. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical transmitter used for optical communication, an optical transmission apparatus including the optical transmitter, and a method for controlling the optical transmitter.

  There is an increasing demand for optical transceivers that transmit and receive optical signals to and from optical fibers. In such an optical transceiver, two types of standards are defined by MSA (Multiple Source Agreement). They are called SFF (Small Form Factor) type and SFP (Small Form Factor Pluggable) type, respectively.

  When both optical transceivers (SFF type and SFP type) are attached to the system equipment, the attachment state of both is substantially the same, but in the case of the SFF type, the system equipment is fixed directly to the motherboard by a method such as soldering. Only the optical connector is exposed from the face panel, and the optical connector is inserted and removed from the outside. On the other hand, in the case of the SFP type, an electrical signal is input / output from the rear of the main body, that is, from the opposite side of the optical receptacle into which the optical connector is inserted (commonly called the rear / butt side of the main body), that is, This means that the optical transceiver body can be inserted and removed from the system equipment even when it is “ON”. It is called pluggable (plug + able) because it can be inserted and removed even when it is electrically “ON”. The SFP optical transceiver has electrical specifications, appearance specifications, and the like based on Non-Patent Document 1.

  Further, it is known that the optical output power of a semiconductor laser (LD: Laser Diode) often used as a signal light source fluctuates according to a change in ambient temperature (see, for example, Patent Document 1). A conventional optical transmitter is provided with an APC (Automatic Power Control) circuit for controlling the bias current in response to the fluctuation of the optical output characteristic due to the temperature change and obtaining a constant optical output. This APC circuit has a function to monitor the bias current being controlled in order to keep the light emission output of the LD constant, and to issue an alarm when the bias current increases. In some cases, forced emission stop (shutdown) The function to make is also provided.

  FIG. 5 is a block diagram showing a configuration of a conventional optical transmitter. In the figure, reference numeral 100 denotes a host board. The host board 100 includes a transmission signal generation circuit 101, an optical transmitter 102, and an external controller 108. Further, the optical transmitter 102 includes an LD 103, a monitor PD (Photo Diode) 104, an LD drive circuit 105, an APC circuit 106, and a controller 107.

  The controller 107 includes independent monitoring control pins corresponding to the light output shutdown control signal (TxDisable) and the light output abnormal state flag signal (TxFault). Hereinafter, TxDisable is referred to as a shutdown control signal, and TxFault is referred to as an abnormal state detection signal.

  When the shutdown control signal is asserted from the external controller 108 of the host board 100, the controller 107 outputs a shutdown signal to the APC circuit 106 to shut down the optical output. Here, asserting means that the signal is enabled.

  The controller 107 monitors the bias current from the LD drive circuit 105, and when the bias current is determined to be in an abnormal state, the controller 107 asserts an abnormal state detection signal to the external controller 108 and sends a shutdown signal to the APC circuit 106. Output and shut down the light output. This abnormal state detection signal is latched in the controller 107, and this is not canceled even if the bias current becomes equal to or lower than the threshold value by shutting down the optical output by asserting the abnormal state detection signal. The asserted abnormal state detection signal is held until the shutdown control signal is asserted from the external controller 108.

The external controller 108 and the controller 107 of the optical transmitter 102 are connected by a serial communication interface, and the external controller 108 can monitor the internal state of the optical transmitter 102 and perform software control.
INF-8074i Specification for SFP (Small Formfactor Pluggable) Transceiver Rev 1.0 May 12, 2001 JP 2000-22631 A

  However, in the case of a pluggable optical data link such as the SFP type defined in Non-Patent Document 1, it is necessary to reduce the number of pins due to physical restrictions in order to further reduce the size. Since it is difficult to reduce power supply pins and optical transmission / reception signal pins due to operational characteristics, external monitoring control signal pins are targeted for reduction.

It is conceivable to perform monitoring control using a serial communication pin such as I ² C and delete other monitoring control signal pins. However, when a high-speed response is required, a dedicated control pin is necessary. Become. For example, Non-Patent Document 1 stipulates that shutdown by a shutdown control signal is performed within 10 μs, but it takes 300 μs or more in communication time to perform control by serial communication at a transmission rate of 100 kHz, so that it can be used as an alternative. I can't do it.

  Further, when the abnormal state detection signal is issued, as described in Patent Document 1, since the optical output is shut down, the host board 100 detects that the abnormal state detection signal is issued. Recovery processing such as switching the communication line to a backup system must be performed immediately. For this reason, Non-Patent Document 1 stipulates that the abnormal state detection signal be issued within 100 μs after the occurrence of the abnormal state, but this also uses serial communication as an alternative means for the same reason as the shutdown control signal. It is not possible.

As described above, the shutdown control signal input pin and the abnormal state detection signal output pin need to be realized not by serial communication such as I ² C but by hardware monitoring control pins, but these are independent monitoring control pins. For this reason, it has been an adverse effect in promoting downsizing.

  The present invention has been made in view of the above circumstances, and an optical transmitter, an optical transmitter, and an optical transmitter that can reduce the number of terminals by sharing the terminals of the shutdown control signal (TxDisable) and the abnormal state detection signal (TxFault) An object of the present invention is to provide a transmission apparatus and a method for controlling an optical transmitter.

An optical transmitter according to the present invention includes a semiconductor laser that transmits an optical signal, a drive unit that outputs a bias current to the semiconductor laser, an APC unit that controls the drive unit to keep the optical output of the semiconductor laser constant, and a drive Provided between the external monitoring control signal input / output terminal and the control unit, the control unit monitoring the bias current output from the control unit, the external monitoring control signal input / output terminal for connecting the control unit and the optical transmission device Output buffer.
The output buffer is connected to an input terminal connected to an abnormal state detection signal output terminal provided in the control unit, and to a shutdown control signal input terminal provided in the control unit that is pulled up to a predetermined voltage, and is connected to an external monitoring control signal input. An output terminal connected to the output terminal.
The control unit outputs an abnormal state detection signal from the abnormal state detection signal output terminal to the output buffer when the monitor value of the bias current exceeds the shutdown threshold, and based on the input to the shutdown control signal input terminal, the APC unit And a shutdown signal is output to the external monitoring control signal input / output terminal.

  According to the present invention, since the terminals of the shutdown control signal (TxDisable) and the abnormal state detection signal (TxFault) can be made common, the number of terminals (pins) can be reduced without impairing the function.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of an optical transmitter, an optical transmission apparatus including the optical transmitter, and an optical transmitter control method according to the invention will be described with reference to the accompanying drawings.

  FIG. 1 is a block diagram illustrating a configuration example of an optical transmission device including an optical transmitter according to the present invention. In the figure, reference numeral 1 denotes an optical transmission device (hereinafter referred to as a host board). The host board 1 includes a transmission signal generation circuit 2, an optical transmitter 3, an output buffer 11, an external controller 12, and an optical transmitter power switch 13. Is provided. The output buffer 11 corresponds to the external output buffer of the present invention, and is composed of a transistor. The external controller 12 corresponds to an external control unit of the present invention, and an input terminal d connected to the external monitoring control signal input / output terminal g of the optical transmitter 3 and an output terminal connected to the input terminal of the output buffer 11. e. The drain or collector of the output buffer 11 is connected to the external monitoring control signal input / output terminal g of the optical transmitter 3.

  The optical transmitter 3 is an SFP type optical transceiver for performing optical communication, and includes an LD (Laser Diode) 4, a monitor PD (Photo Diode) 5, an LD driving circuit 6, an APC circuit 7, a controller 8, and an output. Buffer 9 and pull-up resistor 10.

  The transmission signal generation circuit 2 generates a transmission signal and inputs it to the optical transmitter 3. The LD drive circuit 6 corresponds to a drive unit of the present invention, and outputs a drive (bias) current based on the transmission signal input from the transmission signal generation circuit 2 to the LD 4. The LD 4 corresponds to the semiconductor laser of the present invention, and outputs an optical signal based on the drive current input from the LD drive circuit 6.

  The monitor PD 5 monitors the optical output power of the LD 4 and outputs an optical output power monitor signal to the APC circuit 7. The APC circuit 7 corresponds to the APC section of the present invention, and provides a drive current control signal to the LD drive circuit 6 in order to keep the light emission output of the LD 4 constant based on the light output power monitor signal from the monitor PD 5. Output.

  The controller 8 corresponds to a control unit of the present invention, and determines whether or not there is an abnormality in the bias current based on the bias current monitor signal from the LD driving circuit 6. If there is an abnormality, the controller 8 sends a shutdown signal to the APC circuit 7. Is output. Further, as shown in FIG. 2 described later, the controller 8 includes a TxFault output terminal b that outputs an abnormal state detection signal (TxFault) and a TxDisable input terminal a that inputs a shutdown control signal (TxDisable).

FIG. 2 is a view showing in detail the portion X shown in FIG. As described above, the controller 8 is configured to perform the output of the abnormal state detection signal and the input of the shutdown control signal at one external monitoring control signal input / output terminal g.
Moreover, FIG. 3 is a figure for demonstrating an example of the external monitoring control state which concerns on operation | movement of the optical transmitter of this invention. In the figure, TxDisable indicates a shutdown control signal, and TxFault indicates an abnormal state detection signal.

  2 and 3, an output buffer 9 is a bipolar or FET (Field Effect Transister) type transistor, whose base or gate is connected to the controller 8, and whose collector or drain is a predetermined voltage via a pull-up resistor 10. Connected to potential. When TxFault output from the external monitoring control signal input / output terminal g is High, since the output terminal c of the output buffer 9 is High, the external monitoring control signal is High, and the optical output state of the optical transmitter 3 is enabled. It becomes. On the other hand, when TxFault output from the external monitoring control signal input / output terminal g is Low, the output terminal c of the output buffer 9 is turned on (Low), so that the external monitoring control signal is Low, and the optical transmitter 3 The light output state of is shut down.

  In FIG. 1, TxFault output from the controller 8 is output as an external monitoring control signal via the output buffer 9, and is set to an internal predetermined voltage (for example, power supply voltage Vcc) by the pull-up resistor 10 of the optical transmitter 3. Pulled up. The controller 8 monitors the bias current from the LD drive circuit 6, and when the monitored value exceeds the threshold value, the controller 8 determines that the bias current is in an abnormal state and asserts TxFault. This TxFault is High when normal, and Low when abnormality is detected.

  The TxDisable output from the external controller 12 is output as an external monitoring control signal via the output buffer 11 and input to the controller 8 as an input of TxDisable inside the optical transmitter 3. In addition, when TxFault is issued, the optical output is always controlled to shut down.

  When TxDisable is asserted and the optical output is shut down, the bias current becomes zero and below the threshold value, but TxFault is latched by the controller 8. Therefore, this TxFault is asserted until the optical transmitter 3 is turned off by the optical transmitter power switch 13 or is released by serial communication with the external controller 12.

  The host board 1 monitors TxFault output from the controller 8 and performs processing such as switching the communication line to a backup (backup) system when the controller 8 detects an abnormality in the bias current.

  When it is desired to shut down the optical output from the host board 1, the external controller 12 outputs TxDisable at Low and controls the external monitoring control signal to Low. As a result, the TxDisable input of the controller 8 is asserted, and the optical output from the optical transmitter 3 is shut down.

  As described above, the optical transmitter 3 is provided between the external monitoring control signal input / output terminal g for connecting the controller 8 and the host boat 1, and between the external monitoring control signal input / output terminal g and the controller 8. And an output buffer 9.

  The output buffer 9 has an input terminal connected to the TxFault output terminal b of the controller 8, a voltage pulled up to a predetermined voltage and connected to the TxDisable input terminal a of the controller 8, and an external monitoring control signal input / output terminal g A connected output terminal.

  When the monitored value of the bias current exceeds the shutdown threshold, the controller 8 outputs TxFault from the TxFault output terminal b to the output buffer 9 and sends a shutdown signal to the APC circuit 7 based on the input to the TxDisable input terminal a. At the same time, this TxFault is output as an external monitoring control signal to the external monitoring control signal input / output terminal g.

  1, a is a TxDisable input terminal of the controller 8, b is a TxFault output terminal of the controller 8, c is an output of the output buffer 9, d is a TxFault input terminal of the external controller 12, and e is a TxDisable output terminal of the external controller 12. , F are the outputs of the output buffer 11. Note that the external monitoring control signal corresponds to a signal between the paths c to d, the paths c to a, and the paths f to a.

  The output c of the output buffer 9 is connected to both the external monitoring control signal input / output terminal g of the optical transmitter 3 and the TxDisable input terminal a of the controller 8. By setting the Disable signal issued by the controller 8 to High, the TxDisable input terminal a of the controller 8 becomes Low via the output buffer 9 and is shut down. Further, when the external controller 12 issues a TxDisable signal (High) and sets the output f of the output buffer 11 to Low, the controller 8 regardless of whether the output of the TxDisable signal of the controller 8 is High or Low. Since the TxDisable input terminal a is Low, the shutdown is performed.

  Here, when the controller 8 detects an abnormality by the bias monitor, the controller 8 sets the TxFault output terminal b of the controller 8 to High. As a result, the output c of the output buffer 9 becomes Low, and the potential of the TxDisable input terminal a of the controller 8 that has been pulled up to High in the normal state also becomes Low. When the TxDisable input terminal a becomes Low, the controller 8 issues a shutdown signal to the APC circuit 7.

  When the TxDisable input terminal a of the controller 8 becomes Low, the TxFault input terminal d of the external controller 12 becomes Low, and the host board 1 detects an abnormality of the optical transmitter 3. The external controller 12 maintains the TxDisable output terminal e High, that is, the output f of the output buffer 11 is Low. Therefore, in the optical transmitter 3, even if the TxFault output terminal b of the controller 8 changes from High to Low, the potential of the TxDisable input terminal a is maintained at Low. The shutdown is canceled only when the TxDisable output terminal e of the external controller 12 is set to Low and the TxFault output terminal b of the controller 8 is Low.

  Thereby, the terminals of the shutdown control signal (TxDisable) and the abnormal state detection signal (TxFault) can be shared, and the number of terminals (pins) can be reduced without impairing the function. Further, since the TxDisable input and the TxFault output are realized by the hardware monitoring control pin, a high-speed response can be realized.

  Further, the host board 1 includes a communication control IC (not shown), and this communication control IC can detect an abnormality of the optical transmitter 3 by distinguishing its own control state (TxDisable) from the external monitoring control signal. it can. That is, as shown in FIG. 3, when the output of TxDisable is High and the external monitoring control signal is Low, the communication control IC determines that the optical transmitter 3 is in an abnormal state, and the optical output of the optical transmitter 3 Control to shut down.

  Here, in order to release the TxFault latched in the controller 8, the conventional configuration shown in FIG. 5 employs a method in which TxDisable is asserted from the external controller. However, since the TxDisable input and the TxFault output are shared by one terminal in the circuit configuration according to the present invention, this method cannot be adopted. Therefore, as a countermeasure, an optical transmitter power switch 13 is provided on the host board 1 to temporarily turn off the optical transmitter 3 or to cancel TxFault by serial communication between the external controller 12 and the controller 8. May be.

  When the abnormality detection state is reset (released) using serial communication, the optical transmitter power switch 13 can be dispensed with. In this case, since the abnormality detection state can be reset by serial communication without turning off the power, a power ON / OFF circuit for the optical transmitter on the host board becomes unnecessary, and the host board circuit can be simplified.

FIG. 4 is a flowchart for explaining an example of the control method of the optical transmitter 3 according to the present invention.
First, the controller 8 of the optical transmitter 3 clears the abnormal state detection signal (Txfault), that is, sets Txfault = High (step S1), and determines whether TxDisable = Low (step S2). When TxDisable = High instead of TxDisable = Low (in the case of NO), the optical output state of the optical transmitter 3 is enabled (step S3). In step S2, if TxDisable = Low (YES), the optical output of the optical transmitter 3 is shut down (step S4).

  Next, the controller 8 determines whether or not the bias current monitor value> the shutdown threshold value (step S5). If the bias current monitor value> the shutdown threshold value is not satisfied (in the case of NO), the controller 8 returns to step S2 and repeats the process. If the bias current monitor value> the shutdown threshold value (YES), the abnormal state detection signal is asserted, that is, TxFault = Low (step S6), and the process returns to step S2 to repeat the process.

It is a block diagram which shows the structural example of the optical transmission apparatus provided with the optical transmitter by this invention. It is the figure which showed the X section shown in FIG. 1 in detail. It is a figure which shows an example of the external monitoring control state which concerns on operation | movement of the optical transmitter of this invention. It is a flowchart for demonstrating an example of the control method of the optical transmitter by this invention. It is a block diagram which shows the structure of the conventional optical transmitter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,100 ... Host board (optical transmission apparatus), 2,101 ... Transmission signal generation circuit, 3,102 ... Optical transmitter, 4,103 ... LD, 5,104 ... Monitor PD, 6,105 ... LD drive circuit, 7, 106 ... APC circuit, 8, 107 ... controller, 9, 11 ... output buffer, 10 ... pull-up resistor, 12, 108 ... external controller, 13 ... power switch for optical transmitter.

Claims (5)

A semiconductor laser that transmits an optical signal, a drive unit that outputs a bias current to the semiconductor laser, an APC unit that controls the drive unit to keep the optical output of the semiconductor laser constant, and is output from the drive unit An optical transmitter including a control unit that monitors the bias current,
An external monitoring control signal input / output terminal for connecting the control unit and the optical transmission device, and an output buffer provided between the external monitoring control signal input / output terminal and the control unit,
The output buffer is connected to an input terminal connected to an abnormal state detection signal output terminal included in the control unit, a shutdown control signal input terminal pulled up to a predetermined voltage and included in the control unit, and the external buffer It has an output terminal connected to a monitoring control signal input / output terminal,
The control unit outputs an abnormal state detection signal from the abnormal state detection signal output terminal to the output buffer when the monitored value of the bias current exceeds a shutdown threshold, and inputs to the shutdown control signal input terminal And outputting an abnormal state detection signal to the external monitoring control signal input / output terminal as well as outputting a shutdown signal to the APC unit.   2. The light according to claim 1, wherein the output buffer includes a transistor having a base or a gate connected to the control unit, and a collector or a drain connected to a predetermined potential via a resistance element. Transmitter. The control unit includes a serial communication interface for communicating with the optical transmission device,
The optical transmitter according to claim 1 or 2, wherein an abnormality detection state of the optical transmitter is reset by a reset command transmitted from the optical transmission device via the serial communication interface. An optical transmission device comprising the optical transmitter according to any one of claims 1 to 3,
An external control unit for controlling the optical transmitter from the outside, and an external output buffer composed of transistors,
The external control unit includes an input terminal connected to an external monitoring control signal input / output terminal of the optical transmitter, and an output terminal connected to an input terminal of the external output buffer,
An optical transmission apparatus, wherein a drain or a collector of the external output buffer is connected to an external monitoring control signal input / output terminal of the optical transmitter. A semiconductor laser that transmits an optical signal, a drive unit that outputs a bias current to the semiconductor laser, an APC unit that controls the drive unit to keep the optical output of the semiconductor laser constant, and is output from the drive unit A control unit for monitoring the bias current, an external monitoring control signal input / output terminal for connecting the control unit and the optical transmission device, and provided between the external monitoring control signal input / output terminal and the control unit. A method of controlling an optical transmitter including an output buffer,
An input terminal of the output buffer is connected to an abnormal state detection signal output terminal provided in the control unit,
An output terminal of the output buffer is pulled up to a predetermined voltage and connected to a shutdown control signal input terminal provided in the control unit, and is connected to the external monitoring control signal input / output terminal,
When the monitor value of the bias current exceeds a shutdown threshold, the control unit outputs an abnormal state detection signal from the abnormal state detection signal output terminal to the output buffer, and inputs to the shutdown control signal input terminal And outputting a shutdown signal to the APC unit based on the APC unit and outputting the abnormal state detection signal to the external monitoring control signal input / output terminal.

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