JPH114196A - Optical communication system and optical transmitter therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical communication system and an optical transmistter which can improve the receiving sensitivity to increase the non-relay transmission range and also to miniaturize the optical antennas of both transmitter and receiver sides. SOLUTION: The continuous beams which are outputted from a laser light source 1 are turned into the impulsive forms via the modulation of intensity undergone by the clock signal synchronous with the data signal and then inputted to an optical phase modulator 2. Meanwhile, the data signal is converted into a DPSK code by an encoder (NRZ/DPSK) 4 and applied to the modulator 2 as a drive signal. Thus, an optical signal of an impulsive form that undergone the phase modulation based on the data signal is generated. This optical signal is amplified by an EDFA 5 and radiated into a space through an optical antenna 6. The radiated optical signal is received an optical antenna 7, amplified and formed into a waveform. Then the phase change of the optical signal is converted into the intensity change by an optical interferer 10. The converted optical signal undergoes the photoelectric conversion and the data are reproduced by 8 receiving circuit 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical communication system used in, for example, inter-satellite optical communication and an optical transmission device thereof.

[0002]

2. Description of the Related Art With the recent development of optical communication technology, optical communication systems in various environments are being developed. In such a situation, for example, a system for transmitting an optical signal between artificial satellites by directly emitting an optical signal to outer space without using an optical fiber has been considered. FIG. 11 shows a conventional configuration of this type of optical communication system.

[0003] The optical communication system shown in FIG. 11 includes an optical transmitting device 100 and an optical receiving device 200. In the optical transmitter 100, continuous light (coherent light) output from the laser light source 1 is guided to an input port of the optical phase modulator 2. The output of the encoder (NRZ / DPSK) 4 whose gain has been adjusted by the amplifier 3 is given to the optical phase modulator 2 as a drive signal. This encoder (NRZ
/ DPSK) 4 converts DPSK (Differential Phase Shift Keying) from a data signal represented by the NRZ code based on a clock signal bit-synchronized with the data signal.
The output light of the laser light source 1 is converted into a code (differential synchronous phase shift keying) code. The phase-modulated optical signal is amplified by an erbium-doped optical fiber amplifier (hereinafter, abbreviated as EDFA) 5 and then emitted from the optical antenna 6 into outer space.

[0004] The emitted optical signal propagates through outer space and is received by the optical antenna 7 of the optical receiver 200. The received weak optical signal is amplified by the EDFA 8, the optical noise is attenuated by the narrow band optical band pass filter 9, and then guided to the optical interferometer 10. The optical interferometer 10 includes optical couplers 101 and 102 and a 1-bit optical delay unit 103. After an input optical signal is branched into two by the optical coupler 101, one optical signal is converted to a 1-bit optical delay unit. 103, the signal is delayed by one bit.
Re-combining in step 2 converts the change in phase of the input optical signal into a change in intensity. The output of the optical interferometer 10 is photoelectrically converted by a photoelectric converter 11 and guided to a receiving circuit 12.

The receiving circuit 12 includes a preamplifier 121, a discriminator 122, and a clock extracting circuit 123. The output of the photoelectric converter 11 is amplified by the preamplifier 121, then branched into two, and the output of the discriminator 122 and the clock extracting circuit, respectively. Circuit 123. In the clock extracting circuit 123, a clock signal is extracted from the input signal, and this clock signal is output to the outside and also supplied to the discriminator 122. Then, the data signal is discriminated and reproduced by the discriminator 122,
The received data is output to the outside.

The operation of the optical communication system will be described in more detail with reference to FIG. Here, description will be made assuming that "0100110" is transmitted as a data signal.
The data signal (a) is input to the encoder (NRZ / DPSK) 4 together with the clock signal (b), and is converted into a DPSK code (c) synchronized with the clock signal. This DPS
The K code is a code having the property of being inverted each time "1" appears in the input data, and the optical phase modulator 2 is driven by this DPSK code. As a result, the continuous light (d) from the laser light source 1 becomes DPSK as shown in (e).
The signal is modulated into an optical signal having two phases corresponding to the code.
Here, 0 is described when the phase is not inverted, and π when inverted. The modulated optical signal (e) is amplified by the EDFA 5 and then emitted from the optical antenna 6 into outer space.

The radiated optical signal is transmitted to an optical receiver 20.
The signal is received by the optical antenna 7, amplified by the EDFA 8, and guided to the optical bandpass filter 9. Here, after the noise component is attenuated, the received optical signal is input to the optical interferometer 10.

Here, an output optical signal of the 1-bit optical delay unit 103 of the optical interferometer 10 is shown in FIG. When the optical signals of the waveforms (e) and (f) are combined by the optical coupler 102, they cancel each other out when the phases of both waveforms are opposite to each other, that is, when “π” and “0” or “0” and “π”. . On the other hand, when the phases of both waveforms are the same, that is, “π” or “0”, they reinforce each other. Therefore, at the output stage of the optical interferometer 10, an intensity-modulated waveform as shown in FIG. 12 (g) is obtained. The intensity-modulated optical signal is converted into an electric signal by the photoelectric converter 11 and clock recovery and identification reproduction are performed by the receiving circuit 12 to reproduce the original data signal. Further, by inverting this waveform, the original code string (h) is obtained.

[0009] It is known that the above-mentioned conventional optical communication system can obtain a receiving characteristic with a sensitivity of about 3 dB higher than that of the IM-DD (intensity modulation / direct detection) system usually used in terrestrial optical fiber communication. Have been.

When an optical fiber is used as a communication medium, for example, in an optical communication system in a terrestrial system, an optical repeater is provided in the middle of a transmission line to amplify a deteriorated optical signal, thereby extending a communication distance. be able to. However, in a system for transmitting an optical signal by directly radiating the optical signal to the space as described above, an optical repeater cannot be provided in the middle of the transmission path. For this reason, it is necessary to improve the sensitivity of the system in order to further increase the transmission distance, and the development of an optical communication system with higher sensitivity is awaited. In particular, in the inter-satellite optical communication system, the size of the optical antenna mounted on the artificial satellite can be reduced by increasing the sensitivity of the system, which is a great advantage in reducing the weight of the satellite.

[0011]

As described above, in an optical communication system for transmitting an optical signal by radiating the optical signal directly to the space, the development of an optical communication system with further improved reception sensitivity has been developed. I have been waiting.

The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide an optical communication system and an optical transmission device capable of improving reception sensitivity, thereby increasing a non-repeated transmission distance, and reducing the size of an optical antenna on a transmission side and a reception side. It is in.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an optical communication system according to the present invention is an optical communication system for transmitting information via an optical signal radiated into space. Means are provided to convert a data signal represented by a predetermined code such as an NRZ code into a binary differential synchronous phase shift keying code based on a clock signal bit-synchronized with the data signal. Then, the continuous light output from the light source is intensity-modulated based on the clock signal to form an optical pulse, and the optical pulse is modulated at two phases of, for example, 0 and π based on the output of the code conversion means. The light is amplified to a predetermined intensity by an optical amplifier and emitted to space.

In the optical receiver, the optical signal radiated into this space is amplified, noise is removed, the optical signal is branched into two, one optical signal is delayed by one bit, and both optical signals are combined. The change in phase of the received optical signal is converted into a change in intensity. This optical signal is converted into an electric signal by a photoelectric converter, and the data signal is identified and reproduced by the data reproducing means.

With this configuration, an optical signal that has been phase-modulated in accordance with the data signal is emitted in a pulsed manner. For this reason, the average transmission power can be reduced as compared with the related art, and the reception sensitivity can be increased as compared with the related art when compared at the same transmission power. Further, by using, for example, an erbium-doped optical fiber amplifier as the optical amplifier, the peak power of the transmission optical signal can be increased as compared with the conventional case. This makes it possible to extend the transmission distance.

In the optical transmitter, the continuous light may be phase-modulated and then intensity-modulated to generate an optical pulse. Also, by converting the data signal into a ternary differential synchronous phase shift keying code and driving, for example, a Mach-Zehnder type optical interferometer, an optical pulse directly phase-modulated from the continuous light output from the light source is obtained. It may be generated. By doing so, the number of components can be reduced, and the weight can be reduced when the optical communication system is mounted on an artificial satellite.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment) FIG. 1 is a diagram showing a configuration of an optical communication system according to a first embodiment of the present invention. In FIG. 1, the same parts as those in FIG.
Detailed description is omitted.

The optical communication system shown in FIG. 1 includes an optical transmitting device 300 and an optical receiving device 200. The optical transmission device 300 includes the optical intensity modulator 21 and the amplifier 31 as a driving circuit thereof.

That is, in the optical transmitter 300, the output light of the laser light source 1 is guided to the input port of the light intensity modulator 21. A clock signal that is bit-synchronized with the data signal is supplied to the light intensity modulator 21 via the amplifier 31 as a drive signal.
Outputs a pulsed optical signal synchronized with the clock signal.

The output of the light intensity modulator 21 is guided to the optical phase modulator 2. The output of the encoder (NRZ / DPSK) 4 is given as a drive signal to the optical phase modulator 2 via the amplifier 3. Therefore, the optical phase modulator 2 outputs a phase according to the DPSK code. A modulated pulsed optical signal is output. Then, the output of the optical phase modulator 2 is amplified by the EDFA and radiated from the optical antenna 6 to outer space.

This will be described in more detail with reference to FIG. The data signal (a) is encoded together with the clock signal (b) by the encoder (N
RZ / DPSK) 4 and converted into a DPSK code (c) synchronized with the clock signal. The level of the DPSK-encoded data signal is adjusted by the amplifier 3 and is supplied to the optical phase modulator 2 as a drive signal.

The clock signal (b) is also input to the amplifier 31 and the level thereof is adjusted, and is supplied to the light intensity modulator 21 as a drive signal. As a result, the continuous light output from the laser light source 1 is intensity-modulated into a pulsed optical signal synchronized with the clock signal as shown in FIG. The intensity-modulated light is input to the optical phase modulator 2, and as a result, as shown in FIG. 2E, the optical phase modulator 2 outputs pulse light whose phase is inverted according to the DPSK code. Here, the phases of the pulse light are described as “0” and “π” corresponding to “L” and “H” of the DPSK code. The phase-modulated pulse light (e) is amplified by the EDFA 5 and then emitted from the optical antenna 6 into outer space. Here, the EDFA 5 has the property that its saturated output is limited by the average power, not the peak power of the input optical signal. That is, by making the optical signal input to the EDFA 5 into a pulse shape and reducing its duty, a higher peak power can be obtained on the output side.

The radiated optical signal is transmitted to the optical receiver 20
0 is received by the optical antenna 7, amplified and suppressed by the EDFA 8 and the optical bandpass filter 9, and input to the optical interferometer 10. In the optical interferometer 10, an input optical signal is branched into two by an optical coupler 101, and one optical signal is delayed by one bit by a one-bit optical delay device 103. This delayed waveform is shown in FIG. The waveform (f) is recombined with the other branched optical signal by the optical coupler 102, and is output as intensity modulated light shown in the waveform (g). The intensity-modulated light (g) is converted into an electric signal by the photoelectric converter 11 and then input to the receiving circuit 12, where it is clock-reproduced and discriminated and reproduced, and the original data is reproduced by inverting the waveform. This inversion operation is performed by providing an inverter (not shown) in the receiving circuit 12. This output waveform is shown in (h).

Thus, in the present embodiment, the continuous light output from the laser light source 1 is intensity-modulated by a clock signal that is bit-synchronized with the data signal, and is input into the optical phase modulator 2 in the form of a pulse. Further, the data signal is encoded by an encoder (NRZ / DP).
SK) 4 to convert the signal into a DPSK code, which is supplied to the optical phase modulator 2 as a drive signal. This generates a pulse-shaped optical signal phase-modulated based on the data signal,
This optical signal is amplified by the EDFA 5 and emitted from the optical antenna 6 into space. The radiated optical signal is received by the optical antenna 7, amplified and shaped, and then the optical interferometer 10 converts the phase change of the optical signal into a change in intensity. After the optical signal is photoelectrically converted, the data is reproduced by the receiving circuit 12.

As a result, optical transmission between the optical transmitting device 300 and the optical receiving device 200 via the space becomes possible.
In addition, since the transmission optical signal is pulsed, the reception sensitivity can be higher than in the past when compared at the same transmission power. Further, by amplifying and outputting an optical signal with an erbium-doped optical fiber amplifier in the optical transmitter 300, the peak power of the output light can be increased,
This makes it possible to extend the transmission distance.

(Second Embodiment) FIG. 3 is a diagram showing a configuration of an optical communication system according to a second embodiment of the present invention.
In FIG. 3, the same parts as those in FIG. 11 are denoted by the same reference numerals, and detailed description will be omitted.

The optical communication system shown in FIG. 3 includes an optical transmitting device 400 and an optical receiving device 200. The optical transmitter 400 includes a ternary code generator 41 and a Mach-Zehnder optical interferometer 22 (hereinafter, abbreviated as an MZ optical interferometer 22).

That is, in the optical transmitter 400, the output light of the laser light source 1 is transmitted through the MZ optical interferometer 22 to the ED.
The light is guided to the FA, amplified, and radiated from the optical antenna 6 to outer space.

The output of the ternary code generator 41 is supplied to the MZ optical interferometer 22 as a drive signal via the amplifier 3. Further, the output of the encoder (NRZ / DPSK) 4 is given to the ternary code generator 41 together with the clock signal.

Encoders (NRZ / DPSK) 4 and 3
FIG. 4 shows the configuration of the value code generator 41. Encoder (NR
Z / DPSK) 4 includes an AND gate 401 and a T-type flip-flop 402, inputs a data signal represented by an NRZ code together with a clock signal to the AND gate 401, and inputs an output of the data signal to the T-type flip-flop 402. Obtains a binary DPSK code. The ternary code generator 41 includes an AND gate 403, a NOT gate 40
4, an OR gate 405 and a voltage adder 406. The binary DPSK code output from the encoder (NRZ / DPSK) 4 is branched into two, and an AND gate 403 and an O
It is provided to the R gate 405. The clock signal is also branched into two, one of which is supplied to an AND gate 403 and the other is supplied to an OR gate 405 after being inverted by a NOT gate 404. Then, the output of the AND gate 403 and the output of the OR gate 405 are added by the voltage adder 406, so that the ternary code generator 41 outputs the ternary DPSK synchronized with the clock signal.
The sign is output. The ternary DPSK code is intensity-adjusted in accordance with the characteristics of an MZ-type optical interferometer 22, which will be described later.
The signal is supplied to the Z-type optical interferometer 22 as a drive signal. This drive signal is 3/2 Vπ, Vπ, 1/2 as shown in FIG.
It takes three values of Vπ.

FIG. 6 shows the configuration of the MZ type optical interferometer 22.
The MZ type optical interferometer 22 is made of, for example, a LiNbO ₃ (lithium niobate) crystal, and divides an input optical signal into two and leads them to optical waveguides 11 and 12, respectively, and refracts these optical waveguides 11 and 12. The transmittance and the phase of the input optical signal are controlled by changing the rate difference by the driving voltage and re-coupling.

FIG. 7 shows the input / output characteristics (applied voltage-transmittance) of the MZ type optical interferometer 22. As the drive voltage is increased, the phase difference between the branched optical signals changes continuously, and the transmittance also changes sinusoidally. Assuming that the drive voltage at which the phase difference is π, that is, the transmittance becomes 0%, is Vπ, at the points where the drive voltages are Ｖ Vπ and 3/2 Vπ,
An optical output having a transmittance of 50% and a phase difference of π [rad] is obtained. That is, 1 / 2Vπ, V
By applying a voltage having a value of π, 3 / 2Vπ to the MZ optical interferometer 22, an optical pulse that is directly phase-modulated can be obtained.

FIG. 8 shows a signal waveform in this embodiment. The data signal (a) and the clock signal (b) are first input to an encoder (NRZ / DPSK) 4 to generate a binary DPS.
The ternary code is converted into a K code and input to the ternary code generator 41 together with a clock signal to become a ternary DPSK code (c). The ternary DPSK code (c) is １ ／ Vπ,
The level is adjusted so as to take the values of Vπ and 3 / 2Vπ, and supplied to the MZ optical interferometer 22 as a drive signal. Then
The MZ-type optical interferometer 22 directly generates and outputs a phase-modulated optical pulse as shown in (d) from the continuous light output from the laser light source 1. This output light is amplified by the EDFA 5 and emitted from the optical antenna 6 toward the space. on the other hand,
In the optical receiving device 200, the same process as in the first embodiment is followed, and the received optical signal is branched into two, and one optical signal is delayed by one bit (FIG. 8 (e)) and combined. The light becomes the intensity-modulated light of (f), is photoelectrically converted and then inverted to reproduce the original data (g).

Thus, in the present embodiment, the data signal is converted into a ternary DPSK code based on the clock signal, and the data signal is level-adjusted to have values of 1/2 Vπ, Vπ, and 3/2 Vπ, and the MZ optical interferometer 22 Give to. As a result, an optical pulse signal that has been binary-phase-modulated can be directly obtained from the continuous light output from the laser light source 1. Therefore, it is possible to provide an optical communication system having a further simplified configuration. For example, when the optical communication system is mounted on an artificial satellite and used, the weight and size of the system can be reduced.

The present invention is not limited to the above embodiments. For example, in the first embodiment, the output light of the laser light source 1 is intensity-modulated and then phase-modulated. However, the order may be arbitrarily determined. For example, the phase-modulated optical signal may be intensity-modulated. . That is, the output light of the laser light source 1 may be phase-modulated by the optical phase modulator 2 and then intensity-modulated by the light intensity modulator 21 and output. FIG. 9 shows a configuration example of such a system.

That is, the optical transmission device 500 shown in FIG. 9 inputs the output light of the laser light source 1 to the optical phase modulator 2 to phase-modulate the binary light, and inputs the output to the light intensity modulator 21. Thus, pulsed output light is obtained. Here, a binary DPSK code is given to the optical phase modulator 2 and a clock signal is given to the optical intensity modulator 21 as a drive signal. Even with this configuration,
The same effects as in the first embodiment can be obtained.

In each of the embodiments described above, the case where one-way communication is performed has been described as an example. However, it is needless to say that the present invention can be applied to a two-way communication system. FIG. 10 shows a configuration example of such a system. That is, the optical receiving device 200 and the optical transmitting device 300 (or 400, 50
The present invention can be applied to a wavelength division multiplexing system in which communication is performed with different optical wavelengths f1 and f2 by providing two systems in which the optical system 0) and the optical system 0) are connected via an optical coupler 50. .

In each of the above embodiments, the description has been made on the assumption that the optical communication system is mounted on an artificial satellite and communication is performed between the satellites through outer space. -Communication may be performed between satellites. Alternatively, the present invention can be applied to an optical communication system that does not pass through an optical fiber on the ground.
In addition, various modifications can be made without departing from the scope of the present invention.

[0039]

As described above in detail, according to the present invention, since the phase-modulated optical signal is output in the form of a pulse, the average transmission power can be reduced as compared with the prior art.
When compared at the same transmission power, the receiving sensitivity can be increased as compared with the conventional case. Further, by using, for example, an erbium-doped optical fiber amplifier as the optical amplifier, the peak power of the transmission optical signal can be increased more than before, and the transmission distance can be extended.

As described above, an optical communication system and an optical transmission device that can improve the receiving sensitivity and thereby increase the non-repeated transmission distance and can reduce the size of the optical antennas on the transmitting and receiving sides. Can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an optical communication system according to a first embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of the optical communication system according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of an optical communication system according to a second embodiment of the present invention.

FIG. 4 is a logic circuit diagram showing a configuration example of an encoder (NRZ / DPSK) 4 and a ternary code generator 41.

FIG. 5 shows a DPS as a drive signal of the MZ optical interferometer 22.
FIG. 7 is a waveform chart showing a K code.

FIG. 6 is a conceptual diagram showing a configuration of an MZ optical interferometer 22.

FIG. 7 is a characteristic diagram showing input / output characteristics of the MZ optical interferometer 22.

FIG. 8 is a waveform chart for explaining an operation of the optical communication system according to the second embodiment of the present invention.

FIG. 9 is a block diagram showing another example of the embodiment of the present invention.

FIG. 10 is a conceptual diagram showing an example of application of the present invention to a two-way communication system.

FIG. 11 is a block diagram showing a configuration of a conventional optical communication system.

FIG. 12 is a waveform chart for explaining the operation of a conventional optical communication system.

[Explanation of symbols]

100, 300, 400, 500 optical transmitter 200 optical receiver 1 laser light source 2 optical phase modulator 3 amplifier 4 encoder (NRZ / DPSK) 5, 8 erbium-doped optical fiber amplifier (EDF)
A) 6, 7 optical antenna 9 optical bandpass filter 10 optical interferometer 101, 102 optical coupler 103 1-bit optical delay device 11 photoelectric converter 12 reception circuit 121 preamplifier 122 identification device 123 ... Clock extraction circuit 21 ... Light intensity modulator 31 ... Amplifier 41 ... Ternary code generator 401,403 ... AND gate 402 ... T type flip-flop 404 ... NOT gate 405 ... OR gate 406 ... Voltage adder 22 ... Mach-Zehnder type light Interferometer (MZ type optical interferometer) 50 ... Optical coupler 60 ... Optical antenna

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04B 10/105 10/10 10/22

Claims (8)

[Claims] 1. An optical communication system for transmitting information via an optical signal radiated into space, wherein a data signal represented by a predetermined code is converted into a binary signal based on a clock signal bit-synchronized with the data signal. Code conversion means for converting into a differential synchronous phase shift keying code, a light source for generating and outputting continuous light, and an optical pulse generation for generating an optical pulse by intensity-modulating the output light of the light source based on the clock signal. Means, an optical phase modulator for phase-modulating an optical pulse output by the optical pulse generation means, an optical phase modulator driving means for driving the optical phase modulator based on an output of the code conversion means, and the light An optical amplifier comprising: an optical amplifier that amplifies the output of the phase modulator to a predetermined intensity; and an optical signal output unit that emits the output of the optical amplifier to a space. An optical signal receiving means for receiving an optical signal emitted by the stage; an optical signal received by the optical signal receiving means being split into two, one of the optical signals being delayed by one bit, and then combined to form the received optical signal An optical interferometer for converting a phase change of the optical interferometer into an intensity change, a photoelectric converter for photoelectrically converting an output of the optical interferometer, and a data reproducing means for identifying and reproducing a data signal from an output of the photoelectric converter. An optical communication system comprising: a device; 2. An optical communication system for transmitting information via an optical signal radiated into space, wherein a data signal represented by a predetermined code is converted into a binary signal based on a clock signal bit-synchronized with the data signal. Code conversion means for converting into a differential synchronous phase shift keying code, a light source for generating and outputting continuous light, an optical phase modulator for phase modulating the output light of the light source, and the code conversion means Optical phase modulator driving means for driving based on the output of the optical phase modulator; optical pulse generating means for generating an optical pulse by intensity-modulating the output light of the optical phase modulator based on the clock signal; An optical amplifier for amplifying the output of the unit to a predetermined intensity; an optical transmission device comprising: an optical signal output unit for emitting the output of the optical amplifier to a space; Optical signal receiving means for receiving the received optical signal; splitting the optical signal received by the optical signal receiving means into two, delaying one of the optical signals by one bit, and then combining them to change the phase of the received optical signal An optical interferometer that converts the output of the optical interferometer into an intensity change, an optical receiver that includes a photoelectric converter that photoelectrically converts an output of the optical interferometer, and a data reproducing unit that identifies and reproduces a data signal from an output of the photoelectric converter. An optical communication system, comprising: 3. An optical communication system for transmitting information via an optical signal radiated into space, wherein a data signal represented by a predetermined code is converted into a ternary value based on a clock signal bit-synchronized with the data signal. Code converting means for converting into a differential synchronous phase shift keying code, a light source for generating and outputting continuous light, and an output light from the light source is split into two, based on a drive signal provided with the phase of the split optical signal. A first optical interferometer that combines and outputs the first optical interferometer; an optical interferometer driving unit that drives the first optical interferometer based on an output of the code conversion unit; and an output of the optical interferometer. An optical amplifier that amplifies the optical signal to a predetermined intensity; an optical transmitter that includes an optical signal output unit that emits an output of the optical amplifier to a space; and a light that receives an optical signal emitted by the optical signal output unit. Signal reception A second light for splitting the optical signal received by the optical signal receiving means into two, delaying one of the optical signals by 1 bit, and then combining them to convert a phase change of the received optical signal into a change in intensity; An interferometer, an optical receiver that includes a photoelectric converter that photoelectrically converts the output of the second optical interferometer, and a data reproducing unit that identifies and reproduces a data signal from the output of the photoelectric converter. Characteristic optical communication system. 4. An optical transmitter used in an optical communication system for transmitting information via an optical signal radiated into space, wherein a data signal represented by a predetermined code is converted into a bit by the data signal. Code conversion means for converting to a binary differential synchronous phase shift keying code based on a synchronized clock signal; a light source for generating and outputting continuous light; and intensity modulation of output light from the light source based on the clock signal. An optical pulse generating means for generating an optical pulse, an optical phase modulator for phase modulating the optical pulse output from the optical pulse generating means, and a light for driving the optical phase modulator based on an output from the code converting means. Phase modulator driving means, an optical amplifier for amplifying the output of the optical phase modulator to a predetermined intensity, and optical signal output means for emitting the output of the optical amplifier to space. Optical transmitter according to symptoms. 5. An optical transmission device used in an optical communication system for transmitting information via an optical signal radiated into space, comprising: a data signal represented by a predetermined code; Code conversion means for converting into a binary differential synchronous phase shift keying code based on a synchronized clock signal; a light source for generating and outputting continuous light; an optical phase modulator for phase modulating the output light of the light source; An optical phase modulator driving unit that drives an optical phase modulator based on an output of the code conversion unit; and a light that generates an optical pulse by intensity-modulating the output light of the optical phase modulator based on the clock signal. Pulse generating means; an optical amplifier for amplifying the output of the optical pulse generating means to a predetermined intensity; and an optical signal output means for radiating the output of the optical amplifier to space. The transmission device. 6. An optical transmission device used in an optical communication system for transmitting information via an optical signal radiated into space, comprising: a data signal represented by a predetermined code; Code conversion means for converting into a ternary differential synchronous phase shift keying code based on a synchronized clock signal; a light source for generating and outputting continuous light; An optical interferometer that changes the phase based on a given drive signal and then combines and outputs; an optical interferometer driving unit that drives the optical interferometer based on the output of the code conversion unit; and the optical interference An optical transmission device comprising: an optical amplifier that amplifies an output of an optical amplifier to a predetermined intensity; and an optical signal output unit that emits an output of the optical amplifier to a space. 7. The optical transmission device according to claim 6, wherein the optical interferometer is a Mach-Zehnder type optical interferometer. 8. The optical amplifier according to claim 4, wherein the optical amplifier is an erbium-doped optical fiber amplifier.
7. The optical transmission device according to any one of 6.