JP2011217165A - Optical transmitter, optical transmission component and method for controlling optical transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption of an optical transmitter which performs optical wavelength multiplex communication.SOLUTION: The optical transmitter 10 includes: a plurality of light emitting elements 22A-22D which receive supply of current from drive circuits 50A-50D to emit laser light with different oscillation wavelengths, respectively; optical modulation parts 24A-24D which modulate the laser light emitted by each of the plurality of light emitting elements 22A-22D according to transmitted data, respectively; an optical multiplexer 30 which outputs multiplexing light obtained by multiplexing the laser light modulated, respectively by the optical modulation parts 24A-24D; an oscillator 60 which oscillates the current to be supplied from the drive circuits 50A-50D to at least one of the light emitting elements 22A-22D with a predetermined frequency; and a control circuit 40 which controls the current to be supplied from the drive circuits 50A-50D to the light emitting elements 22A-22D based on a signal obtained by transmitting a frequency band according to the predetermined frequency among signals to be obtained by receiving the multiplexing light output by the optical multiplexer 30.

Description

  The present invention relates to an optical transmitter, an optical transmission component, and an optical transmitter control method.

  Optical communication is used to construct a high-speed data communication network. In optical communication, in order to stabilize the output of a transmitted optical signal, the light output from a light emitting element is controlled (see, for example, Patent Document 1). In addition, in order to increase the communication speed, an optical wavelength multiplex communication technique for performing communication by multiplexing not only one wavelength of laser light but also a plurality of laser lights having different wavelengths has been developed.

Japanese Patent No. 3828706

  In optical wavelength division multiplexing communication, it is necessary to control output for each of a plurality of light emitting elements to be multiplexed. If a light receiving element and a control circuit for that purpose are provided for each wavelength, the power consumption and size of the optical transmitter will increase. There was a problem.

  The present invention has been made in view of the above problems, and one of its purposes is to control an optical transmitter, an optical transmission component, and an optical transmitter capable of reducing power consumption when performing optical wavelength division multiplexing communication. It is to provide a method.

  In order to achieve the above object, an optical transmitter according to one embodiment of the present invention includes a plurality of light-emitting elements that emit laser beams having different oscillation wavelengths when supplied with current from a driver circuit, and the plurality of light-emitting elements. A light modulator that modulates the laser light emitted by each of the elements according to transmission data, a light output unit that outputs combined light obtained by combining the laser light modulated by the light modulator, and Among the signals obtained by receiving the combined light output from the light output unit, an oscillation unit that oscillates current supplied to at least one of the plurality of light emitting elements from the drive circuit at a predetermined frequency, And a control unit that controls a current supplied from the drive circuit to the light emitting element based on a signal obtained by transmitting a frequency band corresponding to the predetermined frequency.

  Further, in the optical transmitter according to another aspect of the present invention, the oscillating unit includes a switching unit that switches connection to one of the current supply paths to the plurality of light emitting elements, and the switching unit includes: The connection is switched to the current supply path connected to the drive circuit controlled by the control unit.

  Further, in the optical transmitter according to another aspect of the present invention, the oscillating unit includes a plurality of oscillators connected to the respective current supply paths to the plurality of light emitting elements and having different oscillation frequencies, and the control unit For each of the plurality of light emitting elements, the current supplied to the light emitting element is determined according to the oscillation frequency superimposed on the current supplied to the light emitting element among the signals obtained by receiving the combined light. Control is performed based on a signal obtained by transmitting the frequency band.

  In addition, in the optical transmitter according to another aspect of the present invention, the division unit that divides the combined light output from the optical output unit in two directions and one combined light that is divided by the division unit are received. A light receiving element, wherein the control unit is based on a signal obtained by transmitting a frequency band corresponding to the predetermined frequency among signals obtained by receiving light from the light receiving element. The current supplied to the light emitting element is controlled.

  In addition, an optical transmission component according to one embodiment of the present invention is supplied with a current from a driver circuit and emits light from a plurality of light-emitting elements that emit laser beams having different oscillation wavelengths, and the plurality of light-emitting elements. An optical modulator that modulates the laser light according to transmission data, and an optical output unit that outputs combined light obtained by combining the laser light modulated by the optical modulator, from the drive circuit A current supplied to at least one of the plurality of light emitting elements oscillates at a predetermined frequency, and a signal obtained by receiving the combined light output from the light output unit corresponds to the predetermined frequency. The current supplied from the driving circuit to the light-emitting element is controlled based on a signal obtained by transmitting the transmitted frequency band.

  The method for controlling an optical transmitter according to one embodiment of the present invention is supplied to at least one of a plurality of light-emitting elements that emit laser beams having different oscillation wavelengths by receiving a current from a driving circuit. A step of oscillating a current at a predetermined frequency; a light modulation step of modulating laser light emitted by each of the plurality of light emitting elements according to transmission data; and a laser modulated in the light modulation step. Obtained by transmitting a frequency band corresponding to the predetermined frequency out of a signal obtained by receiving the combined light output in the light output step, and outputting the combined light obtained by combining the light And a control step of controlling a current supplied from the driving circuit to the light emitting element based on a signal.

  According to one embodiment of the present invention, power consumption can be reduced by selectively performing output control of a light emitting element in an optical transmitter that performs optical wavelength division multiplexing communication.

  According to one aspect of the present invention, output control of all light emitting elements can be performed by a set of at least one oscillation unit and a control unit in an optical transmitter that performs optical wavelength division multiplexing communication.

  According to one embodiment of the present invention, output control of all light emitting elements can be performed simultaneously in an optical transmitter that performs optical wavelength division multiplexing communication.

  According to one aspect of the present invention, the number of light receiving elements can be reduced to one in an optical transmitter that performs optical wavelength division multiplexing communication.

It is a block diagram of the optical transmitter which concerns on 1st Embodiment. It is a flowchart of the output control process of the light emitting element in the optical transmitter which concerns on 1st Embodiment. It is a block diagram of the optical transmitter which concerns on 2nd Embodiment. It is a figure which shows the example of 1 structure of the optical transmitter in an optical wavelength division multiplexing system.

  Before describing a mode for carrying out the present invention (hereinafter referred to as an embodiment), a configuration generally used in optical wavelength division multiplexing communication will be described first.

  FIG. 4 shows a configuration example of the optical transmitter 510 in the optical wavelength division multiplexing communication system. The optical transmitter 510 shown in FIG. 4 is a four-wavelength multiplexing optical transmitter 510. The optical transmitter 510 has four optical assemblies 520A, 520B, 520C, and 520D that modulate and output laser beams having different wavelengths. Is installed. Hereinafter, the contents common to the optical assemblies 520A, 520B, 520C, and 520D will be described in a format excluding the symbols A, B, C, and D. The same rules apply to other codes.

  The optical assembly 520 transmits a light emitting element 522 (522A to 522D) that emits laser light according to a driving current (laser current) supplied from the driving circuit 550 (550A to 550D), and a laser beam emitted from the light emitting element 522. It is an optical transmission component including a modulator 524 (524A to 524D) that modulates according to data and a light receiving element 526 (526A to 526D) that receives the laser light emitted from the light emitting element 522. As the modulator 524, an electrolytic absorption type optical modulator (EA) may be used. For example, the front emission light from the light emitting element 522 may be modulated at 25 Gbit / s. The light receiving element 526 may receive backward emitted light from the light emitting element 522.

  The light emitting elements 522 are laser diodes (LDs) that oscillate at different wavelengths. For example, the oscillation wavelength of the light emitting elements 522 may be selected from four wavelengths at intervals of 800 GHz in the 1.3 μm band.

  The laser beams output from the four optical assemblies 520 are input to the optical multiplexer 530 and combined, and then the combined light is connected to the external device via the optical fiber 5 connected to the optical transmitter 510. Is output.

  The drive circuit 550 is a driver (LDD) provided for each light emitting element 522, and the magnitude of the drive current supplied from the drive circuit 550 to the corresponding light emitting element 522 is controlled by the control circuit 540.

  Based on the light output signal received by the light receiving element 526 of each light assembly 520, the control circuit 540 emits light corresponding to each drive circuit 550 so that the light output from each light assembly 520 has a predetermined intensity. The magnitude of the drive current supplied to the element 522 is changed.

  In the optical transmitter 510 shown in FIG. 4, the set of the optical assembly 520, the control circuit 540, and the drive circuit 550 increases according to the number of wavelengths to be multiplexed. Is difficult and power consumption increases.

  Next, an optical transmitter according to the first embodiment of the present invention that solves the problems of the optical transmitter 510 of the optical wavelength multiplexing communication system shown in FIG. 4 will be described.

  FIG. 1 shows a configuration diagram of an optical transmitter 10 according to the first embodiment. As shown in FIG. 1, the optical transmitter 10 includes an optical assembly 20, a bandpass filter 34, a control circuit 40, a drive circuit 50 (50 </ b> A to 50 </ b> D), and an oscillator 60.

  The optical assembly 20 includes light emitting elements 22 (22A to 22D) that emit laser beams having different wavelengths, and light modulators 24 (24A to 24A) that modulate the laser light emitted by the light emitting elements 22 according to transmission data. 24D), an optical combiner 30 that combines the modulated laser beams, a beam splitter 32 (half mirror) that divides the combined light combined by the optical combiner 30 in two directions, and a beam splitter 32. The optical transmission component includes a light receiving element 26 (photodiode) that receives one of the divided combined lights.

  The light emitting element 22 is a laser diode (LD) that oscillates different wavelengths. For example, the oscillation wavelength of the light emitting element 22 is selected as a wavelength of multiple wavelengths (for example, four) at 800 GHz intervals in the 1.3 μm band. Good. A drive current is supplied from the corresponding drive circuit 50 to each light emitting element 22.

  The drive circuit 50 is a circuit (LD driver) that supplies a drive current to the corresponding light emitting element 22 according to the setting by the control circuit 40. Mixers 70 (70 </ b> A to 70 </ b> D) that mix and oscillate the wavelength signal generated by the oscillator 60 and the drive current are provided in the current supply path for supplying the drive current from the drive circuit 50 to the light emitting element 22. Yes.

  The oscillator 60 is a circuit that outputs a signal having a predetermined wavelength different from the modulation wavelength by the optical modulator 24. For example, the oscillation wavelength of the oscillator 60 may be longer than the modulation wavelength of the optical modulator 24. The oscillator 60 has a switch 62 for switching the connection with the mixer 70, and is connected to the mixer 70 selected based on a control signal from the control circuit 40.

  The light emitting element 22 emits laser light in accordance with the drive current supplied from the drive circuit 50. At this time, the drive current supplied from the current supply path to which the oscillator 60 is connected is in a state of oscillating at an oscillation wavelength unique to the oscillator 60. A voltage is applied to the optical modulator 24 from a driving unit (not shown) according to transmission data, and the laser light emitted forward from the light emitting element 22 is absorbed and modulated.

  The laser beams modulated by the optical modulator 24 are multiplexed by the optical multiplexer 30 and then split by the beam splitter 32 in two directions, the optical fiber side and the light receiving element 26 side. Here, the optical output signal received by the light receiving element 26 is input to the band pass filter 34. The optical signal output from the optical assembly 20 is superimposed with the modulation period by the optical modulator 24 and the oscillation period by the oscillator 60, but the modulation period and the oscillation period have different spectral centers. Compared with the case where the drive current is not oscillated, the signal characteristic of the optical output is not inferior.

  The bandpass filter 34 is a filter that selectively transmits a signal in a band corresponding to the oscillation wavelength of the oscillator 60. For example, the band pass filter 34 may be configured to transmit a signal with the oscillation wavelength of the oscillator 60 as a peak. In the present embodiment, among the electric signals obtained by receiving the optical signal multiplexed with four wavelengths by the band pass filter 34, the optical signal output based on the drive current oscillated by the oscillator 60 is supported. An electrical signal is selectively transmitted. The signal that has passed through the bandpass filter 34 is input to the control circuit 40.

  The control circuit 40 is a circuit that performs output control of the light emitting element 22 based on a signal input from the bandpass filter 34. In the present embodiment, the control circuit 40 selects the light emitting element 22 to be output controlled, switches the switch 42 so as to be connected to the driving circuit 50 that supplies a driving current to the selected light emitting element 22, and supplies the oscillator 60 with the above described A control signal is output to switch the switch 62 to the mixer 70 corresponding to the selected drive circuit 50. Then, the control circuit 40 compares the signal input from the bandpass filter 34 after the switching of the switches 42 and 62 with the target value, and is supplied from the drive circuit 50 to the light emitting element 22 so as to compensate for the difference. It controls the magnitude of the drive current.

  For example, when the optical coupling efficiency changes due to deterioration of the laser efficiency of the light emitting element 22 or the change of the component mounting state in the optical assembly 20 and the output from the optical multiplexer 30 fluctuates, the bandpass filter 34 is used. The output amplitude of the signal input to the control circuit 40 is considered to have a linear relationship with the laser efficiency degradation of the light emitting element 22 and the optical coupling efficiency within the optical assembly 20. For example, when the laser efficiency deteriorates, the output amplitude of the signal input to the control circuit 40 via the band pass filter 34 decreases. In this case, the control circuit 40 may control the drive circuit 50 so as to increase the light output of the light emitting element 22 by an amount corresponding to the amplitude decrease of the input signal. Similarly, when the optical coupling efficiency changes due to a change in the component mounting state in the optical assembly 20 and the output from the optical multiplexer 30 decreases, the control circuit 40 corresponds to the amplitude variation of the input signal. The drive circuit 50 may be controlled so as to increase the light output of the light emitting element 22 by the amount. Conversely, the control circuit 40 may control the drive circuit 50 so as to decrease the light output of the light emitting element 22 when the amplitude of the input signal increases. Of course, in addition to the oscillation period of the oscillator 60, the modulation period of the optical modulator 24 is superimposed on the output of the light receiving element 26 input from the band pass filter 34. Since the spectrum of the transmission period of the oscillator 60 is different from the center of the spectrum, the influence of the modulation period of the optical modulator 24 can be ignored in the signal transmitted through the band pass filter 34.

  The control circuit 40 may sequentially switch the light emitting elements 22 that are the targets of output control according to a predetermined condition. For example, the control circuit 40 may switch the light emitting element 22 to be output controlled at predetermined time intervals, and the difference between the output of the light emitting element 22 to be output controlled and the target value is within a predetermined range. The light emitting element 22 that is the target of output control may be switched when it falls within the range.

  FIG. 2 shows a flowchart of the output control process of the light emitting element 22 in the optical transmitter 10 according to the first embodiment.

  As shown in FIG. 2, the control circuit 40 selects the light emitting element 22 whose output is to be controlled (S101), and connects the driving circuit 50 that supplies a driving current to the selected light emitting element 22 and the control circuit 40. At the same time, the switches 42 and 62 are switched so as to connect the oscillator 60 and the mixer 70 so as to oscillate the drive current supplied to the selected light emitting element 22 (S102).

  Each drive circuit 50 outputs a drive current to the light emitting element 22 (S103), and the oscillator 60 oscillates the drive current output from the selected drive circuit 50 (S104). The light emitting elements 22 emit laser beams having different wavelengths according to the input drive currents (S105), and the optical modulator 24 absorbs and modulates the laser beams according to the transmission data (S106). The optical multiplexer 30 combines and outputs the laser beams having different wavelengths modulated by the optical modulator 24 (S107).

  The light receiving element 26 receives the combined light output from the optical multiplexer 30 (S108), and transmits a signal based on the optical output to the band pass filter 34 (S109). The control circuit 40 controls the amount of drive current supplied to the controlled light emitting element 22 based on the signal corresponding to the light output from the controlled light emitting element 22 that is extracted through the bandpass filter 34 ( S110). The control circuit 40 determines whether or not to change the control target based on conditions such as whether or not the timing for changing the light emitting element 22 to be controlled has arrived (S111), and determines to change the control target. If so (S111: Y), the process returns to step S101 to select a new light-emitting element 22 to be controlled, and the subsequent processing is repeated to determine that the control target is not to be changed (S111: N). It is also possible to return to the process S103 and repeat the subsequent processes.

  According to the optical transmitter 10 according to the first embodiment described above, the number of the control circuits 40 and the light receiving elements 26 can be reduced as compared with the optical transmitter 510 illustrated in FIG. This is advantageous in terms of downsizing, and is also advantageous in reducing power consumption.

  Next, a second embodiment for carrying out the present invention will be described with reference to the drawings.

  FIG. 3 shows a configuration diagram of the optical transmitter 10 according to the second embodiment. As shown in FIG. 3, the optical transmitter 10 includes an optical assembly 20, a bandpass filter 34 (34A to 34D), a control circuit 40 (40A to 40D), a drive circuit 50 (50A to 50D), and an oscillator 60 ( 60A-60D). The difference from the optical transmitter 10 according to the first embodiment is that the optical transmitter 10 according to the second embodiment includes an oscillator 60, a control circuit 40 (40A to 40D), and a bandpass filter 34 (34A to 34D). ) Is provided for each light emitting element 22 (22A to 22D). Since the optical assembly 20 is the same as that in the optical transmitter 10 according to the first embodiment, the description thereof is omitted.

  The drive circuit 50 is a circuit that supplies a drive current to the corresponding light emitting element 22 according to the setting by the control circuit 40. Mixers 70 (70 </ b> A to 70 </ b> D) that mix and oscillate the wavelength signal generated by the oscillator 60 and the drive current are provided in the current supply path for supplying the drive current from the drive circuit 50 to the light emitting element 22. Yes.

  The oscillator 60 (60A to 60D) is a circuit that outputs a signal having a predetermined wavelength different from the modulation wavelength by the optical modulator 24 (24A to 24D), and the oscillation wavelength of each oscillator 60 is different from each other. . For example, the oscillation wavelength of the oscillator 60 may be longer than the modulation wavelength of the optical modulator 24.

  The light emitting element 22 emits laser light based on the drive current supplied from the drive circuit 50. At this time, the drive current supplied from each drive circuit 50 is in a state of oscillating at the oscillation wavelength unique to the corresponding oscillator 60. A voltage is applied to the optical modulator 24 from a driving unit (not shown) according to transmission data, and the laser light emitted forward from the light emitting element 22 is absorbed and modulated.

  The laser beams modulated by the optical modulator 24 are combined by the optical multiplexer 30 and then split by the beam splitter 32 into two directions, the optical fiber 5 side and the light receiving element 26 side. Here, a signal based on the optical output received by the light receiving element 26 is input to the band pass filter 34. Note that the optical output from the optical transmitter 10 is in a state in which the modulation period by the optical modulator 24 and the oscillation period by the oscillator 60 are superimposed, but the modulation center and the oscillation period have different spectral centers. Compared with the case where the drive current is not oscillated, the signal characteristic of the optical output is not inferior.

  The band pass filter 34 is a filter that selectively transmits a signal in a band corresponding to the oscillation wavelength of each oscillator 60. Each band pass filter 34 corresponds to the oscillation wavelength of one of the oscillators 60. For example, the band pass filter 34 may be configured to transmit a signal with the oscillation wavelength of the oscillator 60 as a peak. In the present embodiment, the signals obtained by receiving the multiplexed optical signals for each wavelength are selectively transmitted by the respective band pass filters 34 and input to the corresponding control circuits 40.

  The control circuit 40 is a circuit that controls the output of the light emitting element 22 based on the signal input from the band pass filter 34. For example, when the output amplitude of the bandpass filter 34 input to the control circuit 40 decreases, the control circuit 40 is driven to increase the light output of the light emitting element 22 by an amount corresponding to the decrease in the amplitude of the input signal. When the circuit 50 is controlled and the amplitude of the input signal increases, the drive circuit 50 may be controlled so as to reduce the light output of the light emitting element 22.

  According to the optical transmitter 10 according to the second embodiment described above, the number of the light receiving elements 26 can be reduced as compared with the optical transmitter 510 illustrated in FIG. This is advantageous in terms of downsizing, and is also advantageous in terms of reducing power consumption.

  The present invention is not limited to the above embodiment. For example, in the first embodiment, one oscillator 60 and one control circuit 40 are provided. However, a plurality of oscillators 60 and control circuits 40 (numbers less than the number of multiplexed optical wavelengths) are provided, and the oscillator 60 and the control circuit 40 are controlled. The switches 42 and 62 of the circuit 40 may be switched in synchronization with each other. In addition to the above, it is a matter of course that various changes, modifications, and substitutions can be made by those skilled in the art having ordinary knowledge in this field without departing from the spirit of the present invention.

  5 Optical fiber, 10 Optical transmitter, 20 Optical assembly, 22 (22A to 22D) Light emitting element, 24 (24A to 24D) Optical modulator, 26 (26A to 26D) Light receiving element, 30 Optical multiplexer, 32 Beam splitter, 34 (34 to 34D) Bandpass filter, 40 (40A to 40D) Control circuit, 42 switch, 50 (50A to 50D) Drive circuit, 60 (60A to 60D) Oscillator, 62 switch, 70 (70A to 70D) Mixer, 510 Optical transmitter, 520 (520A to 520D) Optical assembly, 522 (522A to 522D) Light emitting element, 524 (524A to 524D) Optical modulator, 526 (526A to 526D) Light receiving element, 530 Optical multiplexer, 540 (540A) ˜540D) Control circuit, 550 (550A˜550D) drive circuit .

Claims (6)

A plurality of light emitting elements that receive laser currents of different oscillation wavelengths in response to the supply of current from the drive circuit;
A light modulator that modulates laser light emitted by each of the plurality of light emitting elements according to transmission data;
A light output unit that outputs combined light obtained by combining the laser light modulated by the light modulation unit;
An oscillating unit that oscillates a current supplied to at least one of the plurality of light emitting elements from the driving circuit at a predetermined frequency;
Based on a signal obtained by transmitting a frequency band corresponding to the predetermined frequency among signals obtained by receiving the combined light output by the light output unit, the light is supplied from the drive circuit to the light emitting element. An optical transmitter comprising: a control unit that controls current. The oscillating unit has switching means for switching connection to any of current supply paths to the plurality of light emitting elements,
The optical transmitter according to claim 1, wherein the switching unit switches the connection to a current supply path connected to a drive circuit controlled by the control unit. The oscillation unit is connected to each current supply path to the plurality of light emitting elements, and includes a plurality of oscillators having different oscillation frequencies,
The control unit, for each of the plurality of light emitting elements, an oscillation frequency superimposed on a current supplied to the light emitting element among signals obtained by receiving the combined light. The optical transmitter according to claim 1, wherein the optical transmitter is controlled based on a signal obtained by transmitting a frequency band corresponding to the frequency band. A dividing unit that divides the combined light output by the light output unit in two directions;
A light receiving element that receives one of the combined lights divided by the dividing unit, and
The control unit generates a current supplied from the drive circuit to the light emitting element based on a signal obtained by transmitting a frequency band corresponding to the predetermined frequency among signals obtained by receiving light from the light receiving element. The optical transmitter according to claim 1, wherein the optical transmitter is controlled. A plurality of light emitting elements that receive laser currents of different oscillation wavelengths in response to the supply of current from the drive circuit;
A light modulator that modulates laser light emitted by each of the plurality of light emitting elements according to transmission data;
A light output unit that outputs combined light obtained by combining the laser light modulated by the light modulation unit, and
A current supplied from the drive circuit to at least one of the plurality of light emitting elements is oscillated at a predetermined frequency;
Based on a signal obtained by transmitting a frequency band corresponding to the predetermined frequency among signals obtained by receiving the combined light output by the light output unit, the light is supplied from the drive circuit to the light emitting element. An optical transmission component characterized in that current is controlled. Oscillating a current supplied to at least one of a plurality of light emitting elements that emit laser beams having different oscillation wavelengths by receiving a current from the driving circuit at a predetermined frequency;
A light modulation step of modulating the laser light emitted by each of the plurality of light emitting elements according to transmission data;
A light output step of outputting combined light obtained by combining the laser light modulated in the light modulation step;
Based on a signal obtained by transmitting a frequency band corresponding to the predetermined frequency among signals obtained by receiving the combined light output in the light output step, the light is supplied from the drive circuit to the light emitting element. And a control step for controlling current. A control method for an optical transmitter, comprising:

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