JP4432666B2 - Optical module and optical transmission device - Google Patents

Description

  The present invention relates to an optical module and an optical transmission device.

Document 1 (Japanese Patent Laid-Open No. 2003-298524) describes a light source for wavelength division multiplexing (WDM) transmission. The light source includes a plurality of optical modules. At startup of the laser diode in the optical module, the output of the laser diode is shut down by the output shutdown circuit. After the shutdown, temperature control of the laser diode is started. By this temperature control, the temperature of the laser diode is stabilized to a predetermined temperature, which is a temperature corresponding to a temperature at which a desired emission wavelength is generated. When the temperature of the laser diode is stabilized, the shutdown of the laser diode is released, and the laser diode outputs laser light.
JP 2003-298524 A

  In an optical module used for a WDM application or a wide temperature range, it is necessary to control a current flowing through a thermoelectric element for adjusting the temperature of the laser diode in order to control the wavelength to a target value. In starting the optical module, it takes about several milliseconds to several hundred milliseconds from the start of automatic temperature control (ATC) until the laser diode reaches the target temperature. During this time, a large inrush current to the thermoelectric element flows temporarily. That is, when starting an optical transmission apparatus equipped with a plurality of optical modules, each optical module performs ATC in order to stabilize its temperature, but ATC control of each optical module is started at the same time. The current consumption increases from the start of control to the stabilization of wavelength.

  For example, an optical communication apparatus for WDM use includes a plurality of optical modules of the same type having different wavelengths. At the start-up time of the optical communication device, the total inrush current is a consumption current obtained by multiplying the inrush current of each optical module by the number of the optical modules, so that a power supply capacity sufficient to cover this current capacity is required.

  Accordingly, an object of the present invention is to provide an optical module and an optical transmission device that can reduce the total inrush current required when the optical transmission device is activated.

The optical module of the present invention includes a laser diode, a laser driver for driving the laser diode, a thermoelectric element for adjusting the temperature of the laser diode, and a current control unit for driving the thermoelectric element, the laser diode A memory unit that stores oscillation wavelength information and delay time information; and a control unit that controls the current control unit . The control unit reads the oscillation wavelength information and the delay time information, determines a delay time for delaying the start of driving the thermoelectric element in order to adjust a timing at which an inrush current starts to flow through the thermoelectric element, and controls the control The control unit controls the current control unit so as not to operate the thermoelectric element during the delay time, and the current control unit starts controlling the thermoelectric element after the delay time .

In each optical module in the optical transmission device, the thermoelectric element adjusts the temperature of the laser diode to determine the wavelength of light generated by the laser diode. The control unit operates so as to delay the start of driving of the thermoelectric element. Therefore, the time during which the inrush current flows through the optical module can be different from the time during which the inrush current flows through other optical modules in the optical transmission apparatus.
In the optical module of the present invention, after the delay time, the current control unit controls the thermoelectric element so that the temperature of the laser diode falls within a desired range. In the optical module of the present invention, the control unit may include a memory element writing unit for writing the oscillation wavelength information and the delay time information into the memory element. The laser diode is not driven before the temperature of the laser diode enters a desired range.

  The optical transmission apparatus of the present invention includes a first optical module in which the driving start of the thermoelectric element is delayed by a first delay time, and a second optical module in which the driving start of the thermoelectric element is delayed by a second delay time. And a host control device connected to the first and second optical optical modules, the first delay time being different from the second delay time.

  In this optical transmission device, since the first delay time is different from the second delay time, the total inrush current that flows when the optical transmission device is activated can be reduced.

  In the optical transmission apparatus of the present invention, the first and second optical modules emit light having different wavelengths. The first and second optical modules may have different unique addresses. The unique address can be associated with a delay time.

  As described above, according to the present invention, it is possible to provide an optical module and an optical transmission device that can reduce the total inrush current required when the optical transmission device is activated.

  DESCRIPTION OF EMBODIMENTS Embodiments relating to an optical module and an optical transmission apparatus of the present invention will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals.

(First embodiment)
FIG. 1 is a schematic diagram showing an optical transmission apparatus for WDM. The optical transmission device 1 includes first to eighth optical modules 3a to 3h, a host control device 5, and a mounting substrate 7. The host control device 5 is connected to each of the first to eighth optical modules 3a to 3h using a bus line 9 (for example, an I ² C bus), and can perform bidirectional communication between them. it can. The wavelength of the oscillation light of the first to eighth optical modules 3a to 3h is different from the wavelength of the oscillation light of the other optical modules. For example, in the optical transmission device used for CWDM, the wavelengths of the first to eighth optical modules 3a to 3h are eight types of 1470 to 1610 nanometers at intervals of 10 nanometers, respectively. Addresses “A0h, A2h” are assigned to the first to eighth optical modules 3a to 3h.

  FIG. 2 is a schematic view showing an example of each optical module in FIG. The optical module 11 includes a laser diode 13, a thermoelectric element 15, a current control circuit 17, a memory element 19, and a control circuit 21. As the laser diode 13, for example, a distributed feedback laser diode, a Fabry bellow laser diode, a surface emitting laser diode, or the like can be used. The thermoelectric element 15 is a Peltier element, for example. The thermoelectric element 15 is used to adjust the temperature of the laser diode 13 to adjust the oscillation wavelength of the laser diode 13 to a target value. The current control circuit 17 drives the thermoelectric element 15. The control unit 20 includes a memory element 19 and a control circuit 21, and the memory element 19 stores oscillation wavelength information of the laser diode 13. The control circuit 21 drives the thermoelectric element 15 by controlling the current control circuit 17 based on the oscillation wavelength information read from the memory element 10. Further, the driving start time of the thermoelectric element 15 is adjusted based on the oscillation wavelength information.

  Therefore, the timing at which the inrush current starts to flow to the thermoelectric element in each optical module can be made different from the timing at which the inrush current starts to flow to the other optical modules.

The laser driver 51 receives the transmission signal S1 from the terminal 53a, and outputs a drive signal _SD to the laser diode 13 in response to the signal S1. In response to the drive signal _SD , the laser diode 13 emits the signal light L1 toward the optical fiber WG1.

  The laser driver 51 receives two types of control signals from the control circuit 21, that is, a bias current control signal and a modulation current control signal. These control signals are also provided to terminals 53b and 53c.

  The temperature monitor 55 can use, for example, a thermistor, monitors the temperature of the laser diode 13, and outputs a corresponding monitor signal M 1 to the current control circuit 17 and the control circuit 21. The current control circuit 17 controls the thermoelectric element 15 in response to the monitor signal M1.

  The photodiode 57 receives the signal light L2 transmitted through the optical fiber WG2, and generates a reception signal S2 corresponding to the signal light L2. As the photodiode 57, a pin photodiode or an avalanche photodiode can be used. The photodiode 57 receives a bias from the photodiode bias circuit 59. The post-amplifier 61 amplifies the reception signal S2 from the photodiode 57 and provides the signal S3 to the terminal 53f.

  FIG. 3 is a schematic diagram illustrating an example of the control unit 20. The control unit 20 includes a CPU 25, an A / D converter 27, a bidirectional communication bus interface 29, a control interface 31, an output interface 33, an input interface 35, and a monitor interface 37. The CPU 25 is connected to an A / D converter 27, a bus interface 29, a control interface 31, an output interface 33, an input interface 35, and a monitor interface 37 via an internal bus 39. The control unit 20 includes a memory unit 41 connected to the internal bus 39.

  The bus interface 29 is used for communicating with the host control device. The control interface 31 provides a signal for controlling the current control circuit 17 and the photodiode bias circuit. The output interface 33 is used to control the laser driver and the post amplifier. The input interface 35 is used for receiving a signal from outside the optical module. The memory unit 41 includes a ROM 43, a RAM 45, and an EEPROM 47. The ROM 43 stores a program for controlling the optical module. The EEPROM 47 stores delay time information 47a and oscillation wavelength information 47b.

  FIG. 4 is a flowchart 100 showing the startup operation of the optical module. In step S101, power is turned on or the optical module 11 is reset, but the control circuit 21 controls the current control circuit 17 so as not to operate the thermoelectric element 15.

  In step S <b> 102, the control circuit 21 issues a control signal to the laser driver 51, and the laser driver 51 does not provide a drive signal to the laser diode 13. That is, at the time of start-up, the control circuit 21 reads the wavelength information and delay amount information held in the EEPROM 47 and determines the delay time for delaying the start of driving of the thermoelectric element 17. After waiting in step S103 for this predetermined delay time, the current control circuit 17 starts controlling the thermoelectric element 15 in step S104. Inrush current flows in the optical module 11 for a while from the start of this control. Steps S104 and S105 are repeated until the temperature of the laser diode 13 falls within a desired range (ATC control is performed). Thereafter, in step S106, the laser diode 13 is driven to start automatic power control (APC). Even after the temperature of the laser diode 13 enters a desired range, the ATC control and the APC control are still effective. As a result of these controls, the wavelength and intensity of the laser light are maintained in desired ranges, and the optical module 11 can be used for optical communication (step S107).

  As described above, when the optical module 11 is activated, control of the current flowing through the thermoelectric element is started after the initial processing of the CPU. The control circuit 21 includes an EEPROM that stores information (hereinafter referred to as a delay time parameter) that can change the start time, and this delay amount is individually set when the optical module is adjusted in the factory. Is done. In the optical module, for example, CWDM 8 waves (1470, 1490, 1510, 1530, 1550, 1570, 1590, 1610 nm) correspond to different times (50, 100, 150, 200, 250, 300, 350, 400 msec). The delay time is recorded in the EEPROM. In this optical transmission device, as shown in FIG. 5A, the peak of the current supplied to the thermoelectric element in each optical module is shifted in time. That is, in this optical transmission device, the timing of inrush current after activation of each optical module is shifted to suppress the maximum current consumption as the optical transmission device. On the other hand, the thermoelectric elements of all the optical modules in the optical transmission device according to the conventional configuration are activated almost simultaneously, and the time change of the current supplied to the thermoelectric elements is as shown in FIG. The peak of the current in the module has almost the same timing. Therefore, in this case, the burden on the power supply device is increased.

  In the optical module 11, the control circuit 21 includes memory element writing means 63 for writing initial setting values such as delay time information and oscillation wavelength information into the EEPROM 19.

(Second Embodiment)
FIG. 6 is a schematic diagram showing the optical transmission device 81. Only differences from the first optical transmission apparatus will be described below. Different addresses are assigned to the first to eighth optical modules 83a to 83h, respectively. That is, in each of the first to eighth optical modules 83a to 83h, an address is set using the three terminals A0 to A2. The three terminals A0 to A2 are connected to either a ground line (GND) or a power supply line (VCC) via a resistance element. The number of combinations is 2 ^3, with three terminals and a resistor, it is possible to identify eight optical modules. The address given to the optical module by the three terminals A0 to A2 and the resistor is fixed. Each of the first to eighth optical modules 83a to 83h has the structure shown in FIGS.

  The EEPROM 47 stores the above unique address, and the control circuit 20 adjusts the driving start time of the thermoelectric element 15 in response to the address signal stored in the EEPROM 47.

  FIG. 7 is a flowchart 110 showing a startup operation of the optical module 11a. In step S110, the optical module 11a is powered on (or the optical module 11a is reset). In step S111, as in the example of the optical module 11, the laser driver 51 does not provide a drive signal to the laser diode 13. Further, the control circuit 21 controls the current control circuit 17 so as not to supply current to the thermoelectric element 15. The control circuit 21 reads the addresses of the terminals 65a, 65b, and 65c, and the address signal is analyzed in subsequent steps S112 to S118 to determine the drive start delay time of the thermoelectric element 17. In accordance with the analysis result, in any one of steps S119 to S126, the control circuit 21 sets the thermoelectric element after the delay time adjusted for each module that actually adjusts the driving start timing of the thermoelectric element 17. 17 is provided to the current control circuit 17, and control of the thermoelectric element 17 is started in step S127. Steps S127 and S128 are repeated until the temperature of the laser diode 13 enters a desired range (ATC control is performed). After the temperature of the laser diode 13 enters the desired range, APC control of the laser diode 13 is started in step S129, and the ATC control and APC control continue even after the temperature of the laser diode 13 enters the desired range. It is valid. As a result of these controls, the laser oscillation wavelength and emission intensity become desired values (step S130).

The optical module uses three external pins (A0 to A2) to uniquely set the I ² C bus address (Slave Address), and a specific delay time is associated with this address. Can do. For example, parameters corresponding to different delay times (50 msec to 400 msec at 50 msec intervals) can be recorded in the EEPROM for up to eight optical modules (addresses: 000b to 111b).

The host assigns each optical module a value shifted by 1 bit to the physical address of the optical module as an authentication address, and writes a delay time to each optical module via the I ² C bus. That is, first, the host puts the A0h address on the bus and specifies the corresponding optical module (in this case, 000b). Delay time information (50 milliseconds) is transmitted from the host to the module between the specified optical module and the host, and the optical module captures this information into the CPU via the bus interface 29. The CPU stores the information in the EEPROM 47. This delay information is written in a predetermined memory address. This operation is performed for other optical modules, and different delay times are transmitted to all the optical modules.

(Third embodiment)
FIG. 8 is a schematic diagram showing an optical transmission apparatus 91 according to the third embodiment. Unlike the first to eighth optical modules 3a to 3h of the first embodiment, the first to eighth optical modules 93a to 93h are connected to the host control device 95 via control lines Mod_Desel1 to Mod_Desel8, respectively. Has been. Mod_Desel1 to Mod_Desel8 are input to the terminal 67 of each optical module. The same address, for example, “A0h” is assigned to the first to eighth optical modules 93a to 93h. In the optical transmission device of this embodiment, each of the first to eighth optical modules 93a to 93h does not use information in the memory unit 41 in order to adjust the driving start timing of the thermoelectric element 15. Each of the first to eighth optical modules 93a to 93h can have a structure similar to that of the optical module shown in FIGS. 2 and 3, but instead of the control unit 20, an external part on the control line Mod_Desel is used. A control unit is provided for delaying the start of driving of the thermoelectric element 15 in response to the signal.

  FIG. 9 is a diagram illustrating timings of external signals on the control lines Mod_Desel1 to Mod_Desel8. In response to the signals on Mod_Desel1 to Mod_Desel8, the control circuit operates the current control circuit 17 so that the operation start times of the thermoelectric elements 15 are different. Therefore, in the optical transmission device 91, the time during which the inrush current flows through the optical module can be different from the time during which the inrush current flows through another optical module.

  FIG. 10 is a flowchart 140 showing the startup operation of the optical module. It is activated in step S140, and steps S141 and S142 are repeated. In step S142, the control circuit 21 monitors the Mod_Desel terminal and delays the start of driving of the thermoelectric element 17 until receiving the permission signal provided on the control line Mod_Desel. After this delay time, the control circuit 21 provides the current control circuit 17 with a signal that permits driving of the thermoelectric element 17. In response to this permission signal, the current control circuit 17 starts control of the thermoelectric element 17 in step S143, and an inrush current flows through the optical module at the start of this control. Steps S143 and S144 are repeated until the temperature of the laser diode 13 enters a desired range (ATC control is performed). After the temperature of the laser diode 13 enters the desired range, APC control is performed while driving the laser diode 13 in step S145. Even after the temperature of the laser diode 13 enters a desired range, the ATC control and the APC control are still effective. As a result of these controls, the wavelength and intensity of the laser light are in the desired ranges, and the optical module can be used for optical communication (step S146).

This embodiment is suitable when the mother board is mounted with a plurality of optical modules (for example, eight optical modules). This optical transmission device is equipped with an I ² C bus and a “MOD_DESEL” terminal that allows the host control device to select whether or not I ² C communication is possible. In order to use the host controller and each optical module on the same I ² C bus, each optical module normally needs to have a unique slave address. However, in the communication apparatus according to this example, the host controller By sending a communication permission signal (Low) to the “MOD_DESEL” terminal of one optical module on the I ² C bus, it becomes possible to communicate with this optical module.

  Similarly to the optical module of the first embodiment, the optical module according to the present embodiment also includes a current control circuit that can control the thermoelectric element, a control circuit, and the like, and responds to a signal on the “MOD_DESEL” terminal. Thus, the current control of the thermoelectric element can be delayed. Specifically, after the power is turned on, the “MOD_DESEL” terminal of all optical modules sends a communication prohibition signal (“High”), and the “MOD_DESEL” terminal every certain time interval, for example, every 50 milliseconds (msec.) Is switched to the communication enable signal (“Low”). By this switching, when starting an optical module mounted on the same substrate, the timing at which the inrush current flowing through each optical module reaches a peak shifts, and therefore the maximum current consumption as the optical transmission device can be suppressed.

  According to some embodiments described above, a laser diode that requires temperature control, a thermoelectric element current control circuit, and a control circuit that can control the current control circuit are built-in, An optical module (an optical transmission module, an optical transmission / reception module) capable of adjusting timing before shipment is provided.

  In the series of embodiments described above, the case where the optical module has both transmission and reception functions has been described as an example. However, the present invention also applies to a light emitting module having only a transmission function in the optical module. It can be applied without any changes.

  While the principles of the invention have been illustrated and described in the preferred embodiments, it will be appreciated by those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. The present invention is not limited to the specific configuration disclosed in the present embodiment, and the control in the optical module of the present embodiment is mainly realized using software. It can also be realized using wear. We therefore claim all modifications and changes that come within the scope and spirit of the following claims.

FIG. 1 is a schematic diagram illustrating an optical transmission apparatus. FIG. 2 is a drawing schematically showing an example of an optical module. FIG. 3 is a schematic diagram illustrating an example of the control unit. FIG. 4 is a flowchart showing the start-up operation of the optical module. FIG. 5A is a diagram illustrating current waveforms of individual optical modules in the optical transmission apparatus according to the present embodiment. FIG. 5B is a diagram illustrating current waveforms of individual optical modules in the optical transmission device of the comparative example. FIG. 6 is a schematic diagram illustrating an optical transmission apparatus. FIG. 7 is a flowchart showing the start-up operation of the optical module. FIG. 8 is a schematic diagram illustrating an optical transmission apparatus. FIG. 9 is a diagram illustrating waveforms of external signals on the control lines Mod_Desel1 to Mod_Desel8. FIG. 10 is a flowchart showing the start-up operation of the optical module.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical transmission apparatus, 3a-3h ... Optical module, 5 ... Host control apparatus, 7 ... Mounting board, 11 ... Optical module, 13 ... Laser diode, 15 ... Thermoelectric element, 17 ... Current drive circuit, 19 ... Memory element, DESCRIPTION OF SYMBOLS 20 ... Control part, 21 ... Control circuit, 25 ... CPU, 27 ... A / D converter, 29 ... Bus interface, 31 ... Control interface, 33 ... Output interface, 35 ... Input interface, 37 ... Monitor Interface 39 ... Internal bus 41 ... Memory unit 43 ... Read only memory (ROM) 45 ... Random access memory (RAM) 47 ... Non-volatile memory (EEPROM) electrically erasable / erasable 47a, 47b ... Information, 51 ... Laser diode driver, WG1, WG2 ... Optical fiber, 57 ... Photo diode, 59 ... F Toda diode bias circuit, 61 ... post amplifier, 63 ... memory element writing means, 67 ... terminal, 81 ... optical transmission device, 83a-83h ... optical module, 91 ... optical transmission device, 93a-93h ... optical module, 95 ... host Control device

Claims (4)

A laser diode;
A laser driver for driving the laser diode;
A thermoelectric element for adjusting the temperature of the laser diode;
A current controller for driving the thermoelectric element;
Including a memory element storing oscillation wavelength information and delay time information of the laser diode, and comprising a control unit for controlling the current control unit ,
The control unit reads the oscillation wavelength information and the delay time information, and determines a delay time for delaying the start of driving of the thermoelectric element in order to adjust a timing at which an inrush current starts to flow through the thermoelectric element,
Together with the control unit is in the delay time to control the current control unit so as not to operate the thermoelectric element, the current control unit after the delay time is characterized that you initiate control of the thermoelectric element Optical module. After the delay time, the current control unit controls the thermoelectric element so that the temperature of the laser diode is in a desired range,
The optical module according to claim 1, further comprising a temperature monitor that monitors a temperature of the laser diode. The control unit includes memory element writing means for writing the oscillation wavelength information and the delay time information into the memory element,
The optical module according to claim 2, wherein the laser diode is not driven before the temperature of the laser diode enters a desired range. The first optical module according to any one of claims 1 to 3 , wherein the driving start of the thermoelectric element is delayed by a first delay time;
The second optical module according to any one of claims 1 to 3 , wherein the driving start of the thermoelectric element is delayed by a second delay time;
A host controller connected to the first and second optical modules;
The first and second optical modules emit light having different wavelengths,
The optical transmission apparatus in which the first delay time is different from the second delay time.

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