JPH11251674A - Optical transmitter and control method for optical output and wavelength in the optical transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly precisely control output power and a wavelength by monitoring driving current supplied to an optical output part and the temperature of the optical output part, controlling the temperature of the optical output part based on wavelength fluctuation quantity against driving current change quantity which is previously decided, and controlling the wavelength of output light. SOLUTION: A temperature control part 4 outputs a temperature control signal F controlling the temperature of the laser diode of a laser module 1 based on a temperature monitoring signal B outputted from the laser module 1 and a laser diode driving current monitoring signal E outputted from a laser diode driving part 3. When driving current D for keeping optical output power to be constant changes owing to the deterioration of the laser diode, the temperature control signal F changes the temperature of a Peltier element, the temperature of the laser diode is controlled, and an output light wavelength is controlled to be constant while the temperature of the laser diode is monitored based on wavelength fluctuation quantity against driving current change quantity which is previously measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmitter, and more particularly, to a technique for controlling the wavelength and output power of output light to be constant even when a drive current fluctuates due to deterioration of a laser diode or the like.

[0002]

2. Description of the Related Art In current optical transmission, a wavelength division multiplex transmission system using an optical amplifier has been put to practical use in order to increase the transmission distance and capacity. With the introduction of this system, the output power of each optical transmission signal and the accuracy of wavelength control have become important. For example, as for the optical wavelength, the wavelength interval becomes narrower with the expansion of the capacity, and the allowable range of the wavelength fluctuation becomes narrower. Therefore, highly accurate wavelength stability control is required.

As a device for controlling the output power and the wavelength, Japanese Patent Application Laid-Open No. 7-095159 (hereinafter referred to as prior art 1)
Technology). This prior art 1
In the optical transmitter, a light source drive unit that controls the intensity of output light of the light source is connected to a light source whose emission wavelength depends on temperature, and a temperature detection unit that detects the temperature of the light source and a temperature control unit that controls the temperature. Is provided. Then, the shift of the emission center wavelength is detected from the light intensity of some wavelengths of the output light. The temperature reference value is fed back to the temperature control unit based on the deviation, and the temperature is controlled to control the emission wavelength.

As a technique for controlling the output power and wavelength, there is a technique described in Japanese Patent Application Laid-Open No. 9-64825 (hereinafter referred to as prior art 2). In the prior art 2, in an optical transmitter, a predetermined channel is selected from the split light and the amplitude value of the selected signal is detected. And
The amplitude of the light is controlled so that the detected amplitude value is equal to a preset reference value.

Further, as a technique for controlling the output power and the wavelength, there is a technique described in Japanese Patent Application Laid-Open No. Hei 9-186654 (hereinafter referred to as prior art 3). This prior art 3
Is to detect the wavelength of the output light and to control the temperature of the laser so that this wavelength becomes constant.

[0006]

However, in the control of the prior arts 1, 2, and 3, since the output control and the temperature control are performed independently of each other, when the drive current for driving the light emitting element changes, Wavelength fluctuations occurred, and the resulting wavelength fluctuations could not be controlled. Therefore, an object of the present invention is to solve the above-mentioned problems and to provide an optical transmission technique capable of performing highly accurate output power and wavelength control.

[0007]

An optical transmitter according to the present invention comprises: an optical output section whose output power changes depending on a drive current and whose output light wavelength changes depending on a temperature; An output power control unit that monitors an output power from the unit and outputs a control signal that controls a drive current supplied to the optical output unit so that the output power is constant; and A drive unit that supplies a drive current to an output unit, and monitors the drive current and the temperature of the light output unit, and controls the temperature of the light output unit based on a wavelength fluctuation amount with respect to a predetermined drive current change amount. And a temperature controller for controlling the wavelength of the output light.

The optical output section monitors an optical output element whose output power changes depending on a drive current and a wavelength of output light changes depending on temperature, and an optical output from the optical output element. Monitoring means for detecting the temperature of the light output element, and temperature changing means for changing the temperature of the light output element. Further, the output power control unit stores a power value in advance, compares the stored power value with the power value of the current light output, and sets the current power value to the stored power value. It is a means for outputting a control signal for controlling the drive current.

The temperature control unit includes a storage unit that stores a wavelength variation with respect to a change in the drive current supplied to the light output unit, and a temperature control unit that controls the temperature of the light output unit in response to the change in the drive current. And a temperature controller for controlling the temperature of the light output unit based on the wavelength variation with respect to the drive current variation. The optical transmitter of the present invention includes:
A laser diode in which the output power changes depending on the drive current and the wavelength of the output light changes depending on the temperature, and a temperature changing unit that changes the temperature of the laser diode by changing the temperature by a temperature control signal, A laser module having light monitoring means for monitoring the output light from the laser diode, temperature detection means for detecting the temperature of the laser diode, storage means for storing a predetermined power value, and the light monitoring means And when the power value of the output light of the laser diode is different from the power value stored in the storage means, the power value of the output light becomes the stored power value. An output power control unit having control means for outputting a control signal for controlling the drive current of the laser diode; and A driving unit that supplies a driving current for driving the diode; and a monitor that monitors the driving current and, when the driving current changes, a wavelength fluctuation amount with respect to a predetermined driving current change amount and a temperature from the laser module temperature detection unit. And a temperature controller that outputs the temperature control signal to change the temperature of the temperature changing unit to control the wavelength of the output light of the laser diode.

In the method for controlling an optical output and a wavelength in an optical transmitter according to the present invention, a step of monitoring a power value of an optical signal output from an optical output element, and the power value of the optical signal is different from an initial value. Controlling the drive current of the light output element to return the power value to an initial value, monitoring the temperature of the light output element, monitoring a change in the drive current, and controlling a change in the drive current. Controlling the temperature of the light output element to control the wavelength of the output light based on the temperature of the light output element and the amount of wavelength change with respect to a predetermined amount of change in drive current. Features.

[0011]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of the optical transmitter according to the present embodiment. In FIG. 1, reference numeral 1 denotes a laser module that outputs an optical transmission signal. This laser module 1
An optical output monitor signal A, which is an optical output monitor signal, and a temperature monitor signal B for monitoring the temperature of the laser diode are output.

An output power control unit 2 monitors the output power of the laser module 1 and outputs a laser diode drive current control signal C for controlling the drive current of the laser diode when the power of the output light fluctuates. I do. Reference numeral 3 denotes a laser diode driving unit. The laser diode drive section 3 supplies a laser diode drive current D to the laser diode based on the laser diode current control signal C output from the output power control section 2. Further, it outputs a laser diode drive current monitor signal E for monitoring the drive current of the laser diode.

Reference numeral 4 denotes a temperature control unit. This temperature controller 4
Is a temperature control signal for controlling the temperature of the laser diode of the laser module 1 based on the temperature monitor signal B output from the laser module 1 and the laser diode drive current monitor signal E output from the laser diode drive unit 3. Output F. Next, each part will be described in detail.

First, the laser module 1 will be described. FIG. 2 is a block diagram of the laser module 1. In FIG. 2, reference numeral 21 denotes a laser diode that outputs an optical transmission signal. The laser diode 21 outputs an optical transmission signal in the front-rear direction, one for signal and the other for monitoring.

Reference numeral 22 denotes an optical output power monitoring unit having a built-in photodiode. This optical output power monitoring unit 22
The photodiode receives the optical signal for monitoring output from the laser diode 21 by the photodiode, converts it into a current, and outputs this value to the output power control unit 2 as the optical output monitor signal A. 23 is a temperature detector. The temperature detecting section 23 has a built-in temperature detecting element (thermistor element) having a property that the resistance value changes with temperature. Then, a change in the resistance value of the temperature detecting element is monitored, and a temperature monitor signal B indicating the temperature is output.

Reference numeral 24 denotes a Peltier element. The laser diode 21 is mounted on the surface of the Peltier device 24. Peltier element 24 is
The temperature of the surface can be changed. Therefore, the temperature of the Peltier element 24 is changed by the temperature control signal F input to the Peltier element 24 to control the temperature of the laser diode 21.

Next, the output power control unit 2 will be described. FIG. 3 is a block diagram of the output power control unit 2. FIG.
Reference numeral 31 denotes a current / voltage conversion circuit which receives the optical output monitor signal A and converts it into a voltage. 32 is a comparison circuit. The comparison circuit 32 stores a predetermined optical power value (initial value), and compares the stored power value with a power value based on the voltage output from the current / voltage conversion circuit 31. Then, a laser diode current control signal C is output to control the laser diode driving current D so as to have the stored power value.

Next, the temperature control section 4 will be described. FIG. 4 is a block diagram of the temperature control unit 4. In FIG. 4, reference numeral 41 denotes a temperature setting circuit. The temperature setting circuit 41 includes a temperature monitor signal B and a laser diode drive current monitor signal E.
Enter The drive current change is monitored by the laser diode drive current monitor signal, and when the drive current D changes to keep the optical output power constant due to deterioration of the laser diode, etc., the drive current change measured in advance is measured. The temperature of the laser diode 21 is controlled by changing the temperature of the Peltier element 24 by the temperature control signal F while monitoring the temperature of the laser diode 21 based on the amount of wavelength fluctuation with respect to the wavelength of the laser diode 21, and the output light wavelength is controlled to be constant.

Next, the operation of the above-described optical transmitter will be described.
FIG. 5 is a flowchart showing an operation for controlling the wavelength and output power of the output light of the optical transmitter. First, an optical output monitor signal A and a temperature monitor signal B are output from the laser module 1 (Step 100).

The output power controller 2 monitors the output power based on the optical output monitor signal A (Step 101). When the output power of the laser diode changes due to deterioration of the laser diode (Step 102), the laser diode driving current D is adjusted so that the output power becomes the initial value.
Is controlled by the laser diode drive current control signal C (Step 103).

On the other hand, the change amount of the laser diode drive current D is monitored by the laser diode drive current monitor signal E (Step 104). Then, when the temperature inside the laser diode element changes due to the change in the laser diode drive current D and an error occurs in the optical wavelength (Step
105) In order to correct the error, the laser diode 2 is controlled by the temperature control signal F based on the temperature monitor signal B indicating the current temperature and the wavelength variation with respect to the drive current variation.
1 and the output light wavelength is controlled to be constant (St).
ep106).

As described above, according to the present invention, in the optical transmitter, even when the driving current fluctuates due to deterioration of the laser diode or the like, the wavelength and output power of the output light can be controlled to be constant. In the embodiment, a case where a laser diode is applied as an example of an optical transmitter has been described. However, the present invention is not limited to a laser diode, and a semiconductor type optical modulator capable of outputting light by a drive current and controlling an optical wavelength by a temperature. It is also applicable to integrated light sources and the like.

[0023]

As described above, according to the present invention, it is possible to easily maintain the power and wavelength of output light constant, and it is possible to maintain stable light in a lightwave network system such as an NB-WDM system that requires wavelength accuracy. Transmission can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of an optical transmitter according to the present embodiment.

FIG. 2 is a block diagram of the laser module 1;

FIG. 3 is a block diagram of an output power control unit 2;

FIG. 4 is a block diagram of a temperature control unit 4;

FIG. 5 is a flowchart showing an operation for controlling the wavelength and output power of output light of the optical transmitter.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laser module 2 output power control unit 3 laser diode drive unit 4 temperature control unit 21 laser diode 22 optical output power monitor unit 23 temperature detection unit 24 Peltier element 31 current / voltage conversion circuit 32 comparison circuit 41 temperature setting circuit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04B 10/26

Claims (6)

[Claims] 1. An optical transmitter, comprising: an optical output unit whose output power changes depending on a drive current and a wavelength of output light changes depending on a temperature; and an output power from the optical output unit. And an output power control unit that outputs a control signal that controls a drive current supplied to the light output unit so that the output power is constant. Based on the control signal, a drive current is supplied to the light output unit. A drive unit that supplies the drive current, monitors the drive current and the temperature of the light output unit, and controls the temperature of the light output unit based on a wavelength variation amount with respect to a predetermined drive current change amount to control the output light. An optical transmitter, comprising: a temperature controller for controlling a wavelength. 2. An optical output device wherein an output power varies depending on a drive current and a wavelength of output light varies depending on a temperature, and an optical output from the optical output device is monitored. 2. The optical transmitter according to claim 1, further comprising: a monitor for detecting the temperature of the light output element; and a temperature changing means for changing the temperature of the light output element. 3. The output power control unit stores a power value in advance, compares the stored power value with a power value of a current optical output, and determines a current power value as a stored power value. 2. The optical transmitter according to claim 1, wherein said optical transmitter outputs a control signal for controlling a drive current. 4. A temperature control unit comprising: storage means for storing a wavelength variation with respect to a change in a drive current supplied to an optical output unit; and a temperature of the light output unit in response to a change in the drive current. 2. The optical transmitter according to claim 1, further comprising: a temperature controller configured to control a temperature of the optical output unit based on the wavelength variation with respect to the drive current variation. 5. An optical transmitter, wherein a laser diode whose output power changes depending on a drive current and a wavelength of output light changes depending on a temperature, and whose temperature changes by a temperature control signal, A laser module having temperature changing means for changing the temperature of the laser diode, light monitoring means for monitoring output light from the laser diode, and temperature detecting means for detecting the temperature of the laser diode; and a predetermined power value. Monitoring the monitor signal from the optical monitoring means, and when the power value of the output light of the laser diode is different from the power value stored in the storage means, An output power control unit having control means for outputting a control signal for controlling a drive current of the laser diode so that the power value becomes a stored power value; and A drive unit that supplies a drive current for driving the laser diode based on the control signal; and, when the drive current changes by monitoring the drive current, a wavelength variation amount with respect to a predetermined drive current change amount and the laser. A temperature control unit that outputs the temperature control signal based on the temperature from the temperature detection unit of the module and changes the temperature of the temperature change unit to control the wavelength of the output light of the laser diode. And an optical transmitter. 6. A method for controlling an optical output and a wavelength in an optical transmitter, the method comprising: monitoring a power value of an optical signal output from an optical output element; and when the power value of the optical signal is different from an initial value. Controlling the drive current of the light output element to return the power value to an initial value, monitoring the temperature of the light output element, monitoring the change in the drive current, and monitoring the change in the drive current. Controlling the temperature of the light output element to control the wavelength of the output light based on the temperature of the light output element and the amount of wavelength variation with respect to a predetermined amount of change in the drive current when detected. Control method of optical output and wavelength in an optical transmitter.