JP2000267053A - Driving method and driving circuit for optical subcarrier modulator - Google Patents

Abstract

[PROBLEMS] To suppress unnecessary side lobes superimposed on an output optical subcarrier modulated by an optical subcarrier modulator,
Further, the present invention provides a driving method and a driving circuit of an optical subcarrier modulator that can suppress noise due to interference in an optical region. SOLUTION: A phase shifter or a frequency shifter is provided in one optical path of a bifurcated optical subcarrier, an optical path is selected by a drive signal according to input data, and a shift amount thereof is controlled to perform phase modulation or frequency modulation. In the driving method and the driving circuit of the optical subcarrier modulator to be performed, the optical subcarrier modulator is driven using the driving signal in which the pulse time width is compressed from the input data signal and the harmonic component is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving an optical subcarrier modulator which superimposes data in an optical domain on an unmodulated optical subcarrier in an optical subcarrier transmission system for transmitting a high frequency signal superimposed on light. And a drive circuit.

An optical subcarrier modulator includes an optical subcarrier frequency modulator that performs frequency modulation by complementarily controlling the frequency shift amount of a bifurcated optical subcarrier in accordance with an input data signal. Nippon 10-1440
65) An optical subcarrier phase modulator that performs phase modulation by controlling the amount of phase shift of a bifurcated optical subcarrier in a complementary manner in accordance with an input data signal (Japanese Patent Application No. Hei 10-1998).
153078), an optical subcarrier multi-level phase modulator (Japanese Patent Application No. 10-271929), an optical subcarrier phase modulator, and an optical spread spectrum transmitter using the same (Japanese Patent Application No. Hei 10-271929)
1-062724), and the present invention is applicable to these drive circuits.

[0003] Such an optical subcarrier modulator can easily transmit a high-frequency electric signal over a long distance due to a low loss property of an optical fiber transmission line, and can be used for a microwave / millimeter wave wireless communication system. Applications are being considered.

[0004]

2. Description of the Related Art An optical subcarrier modulator is provided with a phase shifter and a frequency shifter on one optical path of a bifurcated optical subcarrier, and the shift amount is controlled by an optical switch for selecting an optical path according to input data. Configuration. When a phase shifter is provided, a phase modulation operation is performed, and when a frequency shifter is provided, digital modulation is performed to perform a frequency modulation operation. Compared with the method of superimposing data on a high-frequency signal in the electric domain, electric processing such as frequency conversion and amplification can be omitted, and superimposition at a high bit rate can be easily performed.

FIG. 12 shows a configuration example of an optical subcarrier phase modulator and a driving circuit. Here, an example is shown in which a Mach-Zehnder interferometer type intensity modulator (hereinafter, referred to as “MZ modulator”) is used as an optical intensity modulator (optical switch) used in the optical subcarrier phase modulator.

In the figure, an optical subcarrier phase modulator 1
0 is the Y branch waveguide 11, delay line 12, MZ modulator 13
a, 13b, and a Y-branch waveguide 14, and the drive circuit is a branch 1, an inverter 2, biases T3a, 3b,
It is constituted by bias power supplies 4a and 4b.

The optical subcarrier input to the optical subcarrier phase modulator 10 is split into two optical paths by a Y branch waveguide 11, one of which is input to an MZ modulator 13 a, and the other is input via a delay line 12. Input to the MZ modulator 13b. The delay line 12 gives a phase difference of π between both optical signals. The outputs of the MZ modulators 13a and 13b are coupled by a Y-branch waveguide 14. On the other hand, the input data is split into two by the splitter 1, one of which is connected to the MZ modulator 13a via the bias T3a, and the other is connected to the inverter 2 and the bias T3.
It is connected to the MZ modulator 13b via 3b.

Here, the extinction characteristic of the MZ modulator is shown in FIG.
As shown in the figure, it is assumed that the driving voltage V1 turns on (transmittance 1) and the driving voltages V2 and 2V1-V2 turn off (transmittance 0). The voltages of the input data "1" and "0" are set to be (V1-V2) / 2 and (V2-V1) / 2, respectively, and the voltages of the bias power supplies 4a and 4b connected to the biases T3a and 3b. Are both set to (V1 + V2) / 2.

Thus, when the input data is "1", the input voltages of the biases T3a and 3b are (V1-V2) /
2, (V2-V1) / 2, and the MZ modulators 13a, 13b
Become V1 and V2, and only the MZ modulator 13a is turned on. On the other hand, when the input data is "0", the input voltages of the biases T3a and 3b are (V2-V1) / 2, (V1
−V2) / 2, the driving voltages of the MZ modulators 13a and 13b become V2 and V1, and only the MZ modulator 13b is turned on. That is, the MZ modulators 13a and 13b perform switching operations complementarily according to the input data.

Therefore, when the input data is "1", the optical subcarrier of the reference phase is output from the MZ modulator 13a, and when the input data is "0", the optical subcarrier delayed by π phase by the delay line 12 is the MZ modulator. 13b. The two optical subcarriers are multiplexed by the Y branch waveguide 14, and
It is output as a two-phase modulated optical subcarrier.

If the periodicity of the extinction characteristic of the MZ modulator is used, it is possible to adjust the bias voltage and not use an inverter for inverting the input data. FIG. 14 shows a configuration example in this case. Bias T3
a, 3b connected to bias power supplies 4a, 4b
(V1 + V2) / 2 and (3V1-V2) / 2 are set.

Thus, when the input data is "1", the driving voltages of the MZ modulators 13a and 13b are V1 and 2V1.
−V2, and only the MZ modulator 13a is turned on. On the other hand, when the input data is "0", the MZ modulator 13a,
The drive voltage of the MZ modulator 13b becomes V2 and V1.
Only b is turned on. That is, the MZ modulators 13a, 13
3b performs a switching operation complementarily according to input data by adjusting a bias voltage without using an inverter,
The input optical subcarrier is output as a two-phase modulated optical subcarrier.

The M of the optical subcarrier phase modulator 10
In place of the Z modulators 13a and 13b, an electro-absorption type optical modulator (hereinafter referred to as "EA modulator") can be used. In this case, it is necessary to drive with an inverter shown in FIG. There is. As shown in FIG. 16, the extinction characteristic of the EA modulator is, as shown in FIG. 16, when the drive voltage V1 turns on (transmittance 1) and the drive voltage V2 turns off (transmittance 0). Complementary switch operations can be performed according to data.

FIG. 15 shows a configuration example of an optical subcarrier frequency modulator and a driving circuit. Here, an example in which an EA modulator is used as an optical intensity modulator (optical switch) used for an optical subcarrier frequency modulator will be described. Note that the EA modulator can be replaced with an MZ modulator.

In the figure, an optical subcarrier frequency modulator 20 includes a wavelength filter 21, an optical frequency shifter 22, an EA
The modulators 23a and 23b are constituted by three-to-one couplers 24, and the driving circuit includes a splitter 1, an inverter 2, a bias T3.
a, 3b and bias power supplies 4a, 4b.

The optical subcarrier input to the optical subcarrier frequency modulator 20 is split by the wavelength filter 21 into optical frequency components f0 and f1, and one of the optical frequency components f1 and f1.
Is input to the optical frequency shifter 22 of the frequency shift + fs. The optical frequency shifter 22 outputs two frequency components f1 and f1 + fs by frequency modulation, and inputs them to the EA modulators 23a and 23b. Each EA modulator 23a,
The output of 23 b and the other optical spectrum demultiplexed by the wavelength filter 21 are combined by a three-to-one coupler 24. The configuration of the drive circuit is the same as that of the optical subcarrier phase modulator 10 shown in FIG.

The extinction characteristic of the EA modulator is, as shown in FIG. 16, turned on (transmittance 1) at the drive voltage V1 and turned off (transmittance 0) at the drive voltage V2. The voltages of the input data “1” and “0” are (V1−V2) / 2,
(V2−V1) / 2, and the bias T3a,
The voltages of the bias power supplies 4a and 4b connected to 3b are set so as to be both (V1 + V2) / 2.

Thus, when the input data is "1", the input voltages of the biases T3a and 3b are (V1-V2) /
2, (V2-V1) / 2, and the EA modulators 23a and 23b
Become V1 and V2, and only the EA modulator 23a is turned on. On the other hand, when the input data is "0", the input voltages of the biases T3a and 3b are (V2-V1) / 2, (V1
−V2) / 2, the drive voltages of the EA modulators 23a and 23b become V2 and V1, and only the EA modulator 23b is turned on. That is, the EA modulators 23a and 23b perform the switching operation complementarily according to the input data.

Therefore, when the input data is "1", the optical subcarrier of the optical frequency f1 is output from the EA modulator 23a, and when the input data is "0", the optical subcarrier of the optical frequency f1 + fs modulated by the optical frequency shifter 22 is outputted. The subcarrier is output from EA modulator 23b. The two optical subcarriers and the optical subcarrier of the optical frequency f0 demultiplexed by the wavelength filter 21 are multiplexed by the three-to-one coupler 24, and the optical frequency f
It is output as a binary frequency-modulated optical subcarrier of 1−f0 and f1 + fs−f0.

[0020]

FIG. 17 shows a pulse waveform of each part in a conventional configuration (FIGS. 12 and 15) using an inverter as a drive circuit. (1) is the input data "101
1 ”, (2) is the inverted input data“ 0100 ”, and (3) is the MZ
The drive voltage of the modulator 13a (EA modulator 23a), (4) the drive voltage of the MZ modulator 13b (EA modulator 23b),
(5) indicates the phase (frequency) of the output optical subcarrier of the optical subcarrier phase modulator 10 (optical subcarrier frequency modulator 20). The horizontal axis is time.

FIG. 18 shows a pulse waveform of each section in a conventional configuration (FIG. 14) in which an inverter is not used in a drive circuit. (1) is the input data "1011", (2) is the drive voltage of the MZ modulator 13a, (3) is the drive voltage of the MZ modulator 13b, and (4) is the output optical subcarrier of the optical subcarrier phase modulator 10. Shows the phase of The horizontal axis is time.

The waveform of the input data signal is generally the waveform shown in FIG.
It has a rectangular shape as shown in FIG. Since the conventional drive circuit that branches this into two and superimposes a predetermined bias voltage does not have a function of shaping the pulse waveform, the drive voltage waveform of the MZ modulators 13a and 13b (EA modulators 23a and 23b) is also changed. It becomes a rectangular type. Therefore, when data is superimposed on the optical subcarrier, unnecessary side lobes occur in the spectrum around the subcarrier frequency.
In the case of digital modulation, only the main rope has a meaning and transmission of side lobes is unnecessary. Therefore, it is necessary to suppress side lobes from the viewpoint of effective use of frequency.

The suppression of the side lobe can be achieved by inserting a low-pass filter. However, as the harmonic component of the pulse is removed, the complementary sub-switching operation of the optical subcarrier phase modulator (optical subcarrier frequency modulator) causes 2 in the region where data “1” and “0” are switched.
The noise due to the interference of the light region of the light (the overlapping portion shown in FIGS. 17 (5) and 18 (4)) increases, which causes the waveform of the output optical subcarrier to deteriorate.

The present invention relates to an optical subcarrier modulator capable of suppressing unnecessary side lobes superimposed on an output optical subcarrier modulated by an optical subcarrier modulator and further suppressing noise due to interference in an optical region. It is an object of the present invention to provide a driving method and a driving circuit.

[0025]

According to the present invention, a phase shifter or a frequency shifter is provided in one optical path of a bifurcated optical subcarrier, an optical path is selected by a drive signal corresponding to input data, and the shift amount is selected. In the driving method of the optical subcarrier modulator that performs phase modulation or frequency modulation, the pulse time width is compressed from the input data signal, and the optical subcarrier modulator is driven using the driving signal in which the harmonic component is suppressed. Drive.

A second aspect of the present invention provides a branching device for bifurcating an input data signal, an inverter for inverting one input data signal, and a predetermined bias voltage applied to the other input data signal and the inverted input data signal output from the inverter. And a bias circuit for generating a complementary drive signal for controlling the amount of phase shift or frequency shift of the optical subcarrier modulator, the other input data signal and A series circuit of a pulse compressor for compressing the pulse time width of the inverted input data signal and a low-pass filter for suppressing harmonic components is connected to a stage preceding each bias circuit.

A third aspect of the present invention provides a splitter for bifurcating an input data signal, and a complementary device for superimposing a predetermined bias voltage on each input data signal and controlling the amount of phase shift or frequency shift of the optical subcarrier modulator. In a drive circuit of an optical subcarrier modulator having a bias circuit for generating a dynamic drive signal, a pulse compressor for compressing a pulse time width of each input data signal and a low-pass filter for suppressing harmonic components are provided. A series circuit is connected before each bias circuit.

According to a fourth aspect of the present invention, there is provided a pulse compressor comprising a low-pass filter for suppressing harmonic components of a pulse, and a discriminator for discriminating "1" and "0" of input data based on a predetermined threshold. It is configured to be connected in series, and is used for a drive circuit of an optical subcarrier modulator according to claim 2 or 3.

One of the pulse compressors according to the fifth aspect includes a delay unit for giving a predetermined delay to the input data signal, and an AND circuit for outputting a logical sum of the input data signal and the input data signal delayed by the delay unit. The other of the pulse compressors is constituted by a delay unit for giving a predetermined delay to the inverted input data signal, and an AND circuit for outputting a logical sum of the inverted input data signal and the input data signal delayed by the delay unit,
It is used for a drive circuit of an optical subcarrier modulator according to claim 2.

One of the pulse compressors according to a sixth aspect of the present invention includes a delay unit that applies a predetermined delay to the input data signal, and an AND circuit that outputs a logical sum of the input data signal and the input data signal delayed by the delay unit. The other of the pulse compressor is configured to provide a predetermined delay to the input data signal,
An OR circuit for outputting a logical product of the input data signal and the input data signal delayed by the delay unit is used for the drive circuit of the optical subcarrier modulator according to the third aspect.

[0031]

(First Embodiment) FIG. 1 shows a first embodiment of a drive circuit of the present invention applied to an optical subcarrier phase modulator. In the figure, a feature of the present embodiment is that a driving circuit including an inverter of the conventional optical subcarrier phase modulator shown in FIG. 12 includes pulse compressors 5a and 5b and low-pass filters (LPFs) 6a and 6b. There. Other configurations are the same as the conventional one.

The input data is split into two by a splitter 1, one of which is a pulse compressor 5a, an LPF 6a, a bias T3.
a, the other is connected to the MZ modulator 13a, the other is the inverter 2, the pulse compressor 5b, the LPF 6b, the bias T3
b to the MZ modulator 13b. The splitter 1 and the inverter 2 may use an amplifier having two outputs, a non-inverted output and an inverted output.

FIG. 2 shows a pulse waveform of each part in the first embodiment. Input data (1) and inverted input data
In (2), the pulse time width is compressed by the pulse compressors 5a and 5b, the harmonic components of the pulse are suppressed by the LPFs 6a and 6b, and the predetermined bias voltage (V1 + V2) / 2 is applied.
Are superimposed, and the driving voltage (3) of the MZ modulator 13a and MZ
The driving voltage of the modulator 13b is (4). Pulse compressor 5
The configuration and operation of a and 5b will be described again with reference to FIGS. The optical subcarriers (5) output from the MZ modulators 13a and 13b do not overlap as shown in FIG. 17 (5) in the complementary switching operation due to the compression of the pulse time width of each drive voltage. The intensity modulation due to the interference in the optical domain is suppressed. Also, unnecessary side lobes superimposed on the output optical subcarrier (5) are suppressed by suppressing the harmonic components of the pulse.

The configuration of the driving circuit of this embodiment is M
The same applies when an EA modulator is used instead of the Z modulators 13a and 13b. Further, the present invention is similarly applicable to the drive circuit of the optical subcarrier frequency modulator shown in FIG.

FIG. 3 shows a first configuration example of the pulse compressors 5a and 5b. In the figure, pulse compressors 5a, 5b
Has a configuration in which a low-pass filter (LPF) 51 and a discriminator 52 are connected in series.

FIG. 4 shows a pulse waveform of each part in the first configuration example of the pulse compressor 5a. The LPF 51 is shown in FIG.
As shown in (2), it has the effect of suppressing the harmonic components of the input data pulse and making the rising and falling edges of the pulse gentle. The discriminator 52 determines “1” or “0” of the input data based on a predetermined threshold, and a voltage higher than the threshold is the highest voltage (V1−V2) / 2, and a voltage lower than the threshold is the lowest voltage (V2−V).
It has the function of shaping the pulse waveform so as to output V1) / 2. By changing this threshold, the compression ratio of the pulse can be changed. The same applies to the pulse compressor 5b.

FIG. 5 shows a second configuration example of the pulse compressors 5a and 5b. In the figure, the pulse compressor 5 has a configuration in which a delay device 53 is provided on one of two branched lines, and the output and the other line are connected to an AND circuit 54.

FIG. 6 shows a pulse waveform of each part in the second configuration example of the pulse compressor 5a. FIG.
As shown in (2), it has the effect of delaying the time of the input data pulse. The AND circuit 54 outputs the voltage when the two inputted pulses simultaneously indicate the maximum voltage (V1 -V2) / 2. By adjusting the amount of delay in the delay device 53, the pulse compression ratio can be changed. The same applies to the pulse compressor 5b.

With the structure and operation of the pulse compressors 5a and 5b, the input data of "1" can be controlled by the configuration shown in FIG.
The drive voltage waveform of the MZ modulator 13a shown in (3) is obtained,
The drive voltage waveform of the MZ modulator 13b shown in FIG. 2 (4) can be obtained for the input data of "0".

(Second Embodiment) FIG. 7 shows a drive circuit according to a second embodiment of the present invention applied to an optical subcarrier phase modulator. In the figure, the feature of this embodiment is that FIG.
Is provided with pulse compressors 5a and 5b and low-pass filters (LPFs) 6a and 6b in a drive circuit of the conventional optical subcarrier phase modulator which does not include an inverter. Other configurations are the same as the conventional one.

FIG. 8 shows a pulse waveform of each part in the second embodiment. The input data (1) is input to the pulse compressor 5
a, 5b, the pulse time width is compressed, and the LPF 6
The harmonic components of the pulse are suppressed by a and 6b, and predetermined bias voltages (V1 + V2) / 2 and (3V1-V2) / 2 are superimposed on each other, and the driving voltage (2) of the MZ modulator 13a and the MZ modulator 13b Drive voltage (3). MZ modulator 13a,
The optical subcarrier (4) output from 13b does not overlap as shown in FIG. 18 (4) in its complementary switch operation due to the compression of the pulse time width of each drive voltage.
The intensity modulation due to the interference in the optical domain is suppressed. Also, by suppressing the harmonic components of the pulse, the output optical subcarrier
Unnecessary side lobes superimposed on (4) are suppressed.

FIG. 9 shows a pulse waveform of each part in the drive circuit of the second embodiment. Each of the pulse compressors 5a and 5b of the present embodiment can be constituted by a series circuit of the LPF 51 and the discriminator 52 shown in FIG. The threshold value of the pulse compressor 5a shown in FIG. 9 (2) is set higher than the threshold value of the pulse compressor 5b shown in FIG. 9 (5). Thereby, the discriminator 52 of the pulse compressor 5a corresponding to the input data "1"
The pulse voltage of the output voltage is compressed as shown in FIG. 9 (3). The pulse voltage of the output voltage of the discriminator 52 of the pulse compressor 5b corresponding to the input data "0" is compressed as shown in FIG. 9 (6). Note that, in this configuration, each LPF 51 of the pulse compressors 5 a and 5 b may be arranged such that one LPF is disposed before the splitter 1.

Further, the pulse compressor 5 of the second embodiment
a and 5b can be constituted by the delay unit 53 and the AND circuit 54 shown in FIG. 10 and the delay unit 53 and the OR circuit 55.

FIG. 11 shows a pulse waveform of each section in the second configuration example of the pulse compressor 5b. The delay unit 53 has a function of delaying the time of the input data pulse as shown in FIG. The OR circuit 55 outputs the voltage when one of the two input pulses indicates the maximum voltage (V1 -V2) / 2. By adjusting the amount of delay in the delay device 53, the pulse compression ratio can be changed. Note that the pulse compressor 5a operates as shown in FIG.

With the configuration and operation of the pulse compressors 5a and 5b, the input data of "1" is output as shown in FIG.
The drive voltage waveform of the MZ modulator 13a shown in (2) is obtained,
The drive voltage waveform of the MZ modulator 13b shown in FIG. 8C can be obtained for the input data of "0".

[0046]

As described above, according to the present invention, the harmonic component of the drive signal for driving the optical subcarrier modulator is suppressed, so that unnecessary side lobes superimposed on the output optical subcarrier are suppressed. be able to. Further, since the pulse time width of the drive signal for driving the optical subcarrier modulator is compressed, it is possible to suppress noise due to interference in the optical region generated when the optical subcarrier modulator performs a complementary switching operation. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a drive circuit of the present invention applied to an optical subcarrier phase modulator.

FIG. 2 is a diagram showing a pulse waveform of each unit according to the first embodiment.

FIG. 3 is a block diagram showing a first configuration example of pulse compressors 5a and 5b.

FIG. 4 is a diagram showing a pulse waveform of each unit in a first configuration example of the pulse compressor 5a.

FIG. 5 is a block diagram showing a second configuration example of the pulse compressors 5a and 5b.

FIG. 6 is a diagram showing a pulse waveform of each unit in a second configuration example of the pulse compressor 5a.

FIG. 7 is a block diagram showing a second embodiment of the drive circuit of the present invention applied to an optical subcarrier phase modulator.

FIG. 8 is a diagram showing a pulse waveform of each unit according to the second embodiment.

FIG. 9 is a diagram showing a pulse waveform of each unit in the drive circuit according to the second embodiment.

FIG. 10 shows a pulse compressor 5a according to a second embodiment.
FIG. 5 is a block diagram showing a second configuration example of 5b.

FIG. 11 is a diagram showing a pulse waveform of each unit in a second configuration example of the pulse compressor 5b.

FIG. 12 is a block diagram showing a conventional configuration of an optical subcarrier phase modulator and a driving circuit.

FIG. 13 is a diagram showing the extinction characteristics of the MZ modulator.

FIG. 14 is a block diagram showing a conventional configuration of an optical subcarrier phase modulator and a driving circuit.

FIG. 15 is a block diagram showing a conventional configuration of an optical subcarrier frequency modulator and a driving circuit.

FIG. 16 is a diagram showing the extinction characteristics of the EA modulator.

FIG. 17 is a diagram showing a pulse waveform of each section in a conventional configuration using an inverter for a drive circuit.

FIG. 18 is a diagram showing a pulse waveform of each section in a conventional configuration in which an inverter is not used in a drive circuit.

[Explanation of symbols]

Reference Signs List 1 branch device 2 inverter 3 bias T 4 bias power supply 5 pulse compressor 6 low-pass filter (LPF) 10 optical subcarrier phase modulator 11, 14 Y branch waveguide 12 delay line 13 Mach-Zehnder interferometer type intensity modulator (MZ) Modulator) 20 optical subcarrier frequency modulator 21 wavelength filter 22 optical frequency shifter 23 electroabsorption optical modulator (EA modulator) 24 3-to-1 coupler 51 low-pass filter (LPF) 52 discriminator 53 delay unit 54 AND Circuit 55 OR circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) H04B 10/02 10/18 (72) Inventor Tetsuichiro Ohno 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Japan Within Telegraph and Telephone Corporation (72) Inventor Hiroshi Matsuoka 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo F-Term within Telegraph and Telephone Corporation (reference) 2H079 AA02 AA13 BA01 BA03 CA05 EA05 EB04 FA03 GA03 HA13 KA20 5K002 AA02 BA02 BA04 CA02 CA17 DA05 FA01

Claims (6)

[Claims] 1. A phase shifter or a frequency shifter is provided on one optical path of a bifurcated optical subcarrier, an optical path is selected by a drive signal according to input data, and a shift amount thereof is controlled to perform phase modulation or frequency modulation. A driving method of the optical subcarrier modulator, wherein a pulse time width is compressed from the input data signal, and the optical subcarrier modulator is driven using a driving signal in which a harmonic component is suppressed. A driving method of the optical subcarrier modulator. 2. A branching device for bifurcating an input data signal, an inverter for inverting one of the input data signals branched by the branching device, and a second input data signal branched by the branching device and the inverter. A bias circuit that superimposes a predetermined bias voltage on the output inverted input data signal and generates a complementary drive signal for controlling the amount of phase shift or frequency shift of the optical subcarrier modulator. A driving circuit of the device, a series circuit of a pulse compressor for compressing the pulse time width of the other input data signal and the inverted input data signal branched by the branching device, and a low-pass filter for suppressing harmonic components. A driving circuit for an optical subcarrier modulator connected to a stage preceding each of the bias circuits. 3. A splitter for splitting an input data signal into two, and a predetermined bias voltage is superimposed on each of the input data signals split by the splitter, and a phase shift amount or a frequency shift amount of an optical subcarrier modulator is provided. A drive circuit for an optical subcarrier modulator, comprising: a bias circuit for generating a complementary drive signal for controlling a pulse signal; a pulse compressor for compressing a pulse time width of each of the input data signals; and a harmonic component being suppressed. A drive circuit for an optical subcarrier modulator, wherein a series circuit of a low-pass filter is connected to a stage preceding each bias circuit. 4. The pulse compressor includes a low-pass filter for suppressing a harmonic component of a pulse, and a discriminator for discriminating “1” and “0” of input data based on a predetermined threshold in series. The drive circuit for an optical subcarrier modulator according to claim 2 or 3, wherein the drive circuit is connected. 5. One of the pulse compressors includes a delay unit that applies a predetermined delay to the input data signal, and an AND circuit that outputs a logical sum of the input data signal and the input data signal delayed by the delay unit. The other of the pulse compressors is a delay unit that applies a predetermined delay to the inverted input data signal, and an AND circuit that outputs a logical sum of the inverted input data signal and the input data signal delayed by the delay unit 3. The driving circuit for an optical subcarrier modulator according to claim 2, comprising: 6. One of the pulse compressors includes a delay unit that applies a predetermined delay to the input data signal, and an AND circuit that outputs a logical sum of the input data signal and the input data signal delayed by the delay unit. The other one of the pulse compressors is a delay unit that gives a predetermined delay to the input data signal, and an OR that outputs a logical product of the input data signal and the input data signal delayed by the delay unit
4. The driving circuit for an optical subcarrier modulator according to claim 3, comprising a circuit.