JP2893507B2 - Optical communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication device using laser light used for cooperative communication between spacecraft such as artificial satellites.

[0002]

2. Description of the Related Art In various spacecraft such as artificial satellites and space stations, it is important to cooperate with each other in terms of operation. Therefore, cooperative communication between these spacecrafts is also required in communication. Have been. Conventionally,
Such cooperative communication between spacecrafts is performed using radio waves. However, as the activities in space such as earth observation satellites and space stations have increased, the amount of information to be transmitted between spacecraft has increased dramatically, and a data signal speed of about 1 to 10 Gbps is required. However, the conventional radio communication system has already reached the limit in practical use due to the problem of frequency allocation for preventing interference, the limit of the antenna aperture or the transmission output, and the like. For this reason, an optical communication system using a laser beam attracts attention, and an optical communication system between spacecrafts is expected to be particularly promising in outer space which is not affected by the atmosphere. By the way, when using this optical communication method by laser light for cooperative communication between spacecraft, the beam width of the laser light is very narrow, about 10 ^-12 to 10 ^-13 deg, and the laser beam is tens of thousands km. High-precision beam control on the order of μrad is required to perform transmission and reception with long-distance communication partners.

In order to easily perform such high-precision beam control, transmission and reception in cooperative communication between artificial satellites will be performed using a single large-diameter reflective telescope as shown in FIG. And In FIG. 4, reference numeral 101 denotes an eyepiece, which is disposed near a through-hole 102a formed in the center of the primary mirror 102. 103 is the eyepiece 101
This is a secondary mirror for reflecting the laser beam from the mirror toward the primary mirror 102. In a telescope configured in this way,
The laser signal light from the main oscillation laser is reflected by the sub-mirror 103 and the main mirror 102 through the eyepiece 101, and is transmitted to the communication partner. On the other hand, the laser signal light from the communication partner is reflected by the primary mirror 102 and the secondary mirror 103, passes through the eyepiece 101, and is detected by the laser signal light detector. The laser signal light to be transmitted and the laser signal light from the other party have slightly different wavelengths, and can be separated by a beam splitter having wavelength separation characteristics.

[0004]

By the way, the single large-aperture telescope is required to have extremely high manufacturing accuracy, and the manufacturing technology thereof is extremely difficult. In addition, there is a problem that it is necessary to reduce the weight required for the spacecraft while taking measures to prevent thermal deformation in a space environment and to withstand vibration during launching of the satellite.

As one method for avoiding the technical difficulty of the large-diameter telescope, a telescope having an optical phased array antenna-like configuration formed by bundling a plurality of small telescopes as shown in FIG. 5 can be considered. That is, a single main oscillation laser unit 201 and a splitter for splitting the laser signal light emitted from the main oscillation laser unit 201 into a plurality of laser signal lights.
An optical transmission unit is composed of 202, a phase controller 203 for controlling the phase of each branched laser signal light, and a plurality of small telescopes 204 for emitting each phase-controlled branched laser signal light. The output beam of the laser signal light emitted from the plurality of small telescopes 204 is combined into a transmission beam.

However, when the optical transmitter is configured in this manner, the loss caused at the time of optical branching, the single-mode optical fiber required for propagation along the way cannot withstand an excessively large input, and the single main oscillation laser Due to the power limitations of the unit and the technical difficulties of modulating high power lasers, it is difficult to significantly increase the transmission power.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the conventional or conceivable optical communication apparatus, and an object of the present invention is to provide an optical communication apparatus capable of obtaining a large output and reducing the weight. And

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention is directed to an optical communication system using a laser beam mounted on a spacecraft such as an artificial satellite for performing cooperative communication between the spacecrafts. In the apparatus, a single main oscillation laser section including a modulation section, a splitter for splitting a laser signal light emitted from the main oscillation laser section into a plurality of laser signal lights, and each split laser beam split A phase controller for controlling the phase of light, an optical amplifier for amplifying each phase-controlled branched laser signal light, and a plurality of small telescopes for emitting each amplified branched laser signal light. The output beam of each laser signal light emitted from each of the small telescopes is combined into a single transmission beam.

In the optical communication apparatus thus configured, each phase-controlled branched laser signal light is optically amplified by an optical amplifier to an output required for transmission. Therefore, even if a single main oscillation laser section having a large output is not used, the transmission output can be significantly increased and the weight can be reduced irrespective of the loss caused by the branching device.

[0010]

Next, an embodiment will be described. FIG. 1 is a schematic diagram showing one embodiment of the optical communication device according to the present invention.
In FIG. 1, reference numeral 1 denotes a single main oscillation laser unit including a modulation unit, and 2 denotes a splitter for splitting a laser signal light emitted from the main oscillation laser unit 1 into a plurality of signal lights. The optical fiber is formed by fusing each end of a plurality of optical fibers to the end of the optical fiber (the one branched into about eight is called a star coupler or the like and is commercially available). 3-1
Reference numerals 3-9 denote optical fibers, one end of which is connected to the output end of the splitter 2, and the other end of which has phase controllers 4-1 to 4-9, respectively.
Is connected. As a phase controller, for example, as shown in FIG. 2, an electrode 1 is connected to an optical waveguide 11 made of LiNbO ₃ crystal.
2 and 13 are provided, and a voltage of several volts is applied between the electrodes 12 and 13 to control the refractive index of the crystal, equivalently changing the optical path length, and controlling the phase. Can be. Reference numerals 5-1 to 5-9 denote optical amplifiers connected to the output terminals of the phase controllers 4-1 to 4-9, such as erbium-doped optical fiber amplifiers and semiconductor optical amplifiers. 6-1
Reference numerals 6-9 denote small telescopes connected to the output terminal of the optical amplifier for transmitting the amplified laser signal lights. The small telescopes include, for example, a concave lens 21 and a convex lens 22, as shown in FIG. Galileo-type refracting telescopes are sufficient.

Next, the operation of the space optical communication apparatus having the above-described configuration will be described. The laser signal light emitted from the main oscillation laser unit 1 is split into a large number of laser signal lights in the splitter 2, and each of the optical fibers 3-1 to 3-1
It is guided to the phase controllers 4-1 to 4-9 via 3-9, and the phase is controlled. At this stage, the branched laser signal lights are not signal lights having outputs necessary for communication. Each laser signal light controlled by the phase controllers 4-1 to 4-9 is guided to the optical amplifiers 5-1 to 5-9, and is optically amplified so as to be a required output signal light. Optical amplifier 5-1
Each of the laser signal lights optically amplified to predetermined outputs at ５−5-9 are guided to small telescopes 6-1 to 6-9, respectively.
Each laser signal beam emitted from the small telescope is synthesized
The signal is transmitted as a single transmission beam to the communication partner. The phase control performed using the phase controller 4 corrects a phase difference due to a difference in optical path length or the like in a distant place in order to minimize a decrease in light quantity due to interference between light beams due to a phase difference between optical antennas. The control for removing the phase difference so as to maximize the amount of light reaching a distant place is performed by fine adjustment after production / assembly.

[0012]

As described above with reference to the embodiments,
According to the present invention, since each phase-controlled branched laser signal light is optically amplified to an output required for transmission by an optical amplifier and transmitted from each small telescope, a single output having a large output is obtained. Even without using the main oscillation laser section, the transmission output can be significantly increased and the weight can be reduced irrespective of the loss due to the branching device.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of an optical communication device according to the present invention.

FIG. 2 is a schematic diagram showing a configuration example of a phase controller in the embodiment shown in FIG.

FIG. 3 is a schematic diagram showing a configuration example of a small telescope in the embodiment shown in FIG. 1;

FIG. 4 is a diagram showing a configuration of a conventional large-diameter telescope used for cooperative communication between artificial satellites.

FIG. 5 is a schematic diagram showing a configuration of an optical communication device using a small telescope having an optical phased array antenna configuration that has been conventionally considered.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main oscillation laser part 2 Branching device 3-1-3-9 Optical fiber 4-1-4-9 Phase controller 5-1-5-9 Optical amplifier 6-1-6-9 Small telescope

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04B 10/00-10/28

Claims (1)

(57) [Claims] An optical communication device mounted on a spacecraft such as an artificial satellite or the like and using a laser beam for performing cooperative communication between the spacecrafts , comprising: a single main oscillation laser unit including a modulation unit ; A splitter for splitting the laser signal light emitted from the oscillation laser unit into a plurality of laser signal lights, a phase controller for controlling the phase of each split laser signal light, and An optical amplifier for amplifying the branched laser signal light and a plurality of small telescopes for emitting the amplified branched laser signal light are provided, and the output beams of the laser signal lights emitted from the small telescopes are combined. Just
An optical communication device, wherein the optical communication device is configured to be one transmission beam.