JPH08149076A - Optical space communication device - Google Patents

Abstract

PURPOSE: To always monitor the operating state of an optical communication device by controlling the direction of a light beam by a simple operation. CONSTITUTION: The light beam received from an opposite party device is made incident on a collimating optical system 38 and separated into the main and auxiliary signals by an optical branching device 39 via a mobile mirror 37 and a deflected beam splitter 36. The main signal reflected by the device 39 is made incident on a photoelectric conversion part 43, detected by a main signal detector 46, and monitored by a level meter 50 via a switch 49. On the other hand, the auxiliary signal transmitted through the device 39 is made incident on four photodetectors of a photoelectric converter 41, undergoes the detection of its vertical/horizontal error signals through an auxiliary signal detector 47, and is monitored by the meter 50 via a switch 49. A mobile mirror driving circuit 48 drives the mirror 37 to control the direction of the light beam based on the detected error signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical space communication apparatus for propagating an optical signal modulated from an electric signal in free space for communication.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram of a conventional example in which a transmitter and a receiver are an integrated optical space communication device. The electric signal for transmission input from the input terminal 1 is amplified to an appropriate level by the amplifier 2, and after being combined with the auxiliary signal generated by the auxiliary signal generator 3 by the multiplexer 4, the electric-optical converter is provided. At 5, it is converted into an optical signal. The light emitted from the electro-optical converter 5 is once converted into parallel light by the lens 6, and the light whose polarization direction is horizontal to the paper surface passes through the polarization beam splitter 7 and the traveling direction is changed by the movable mirror 8 for collimating optics. The light beam L having a predetermined divergence angle is transmitted from the system 9 to the opposing device.

On the other hand, the light beam of the other device is incident on the collimating optical system 9 from the same direction as the transmission beam and is changed in direction by the movable mirror 8, and the light whose polarization direction is perpendicular to the paper surface is pasted on the polarization beam splitter 7. The light is reflected by the mating surfaces and separated from the transmitted light, and most of the received light is reflected by the optical branching device 10 and passes through the lens 11 to be condensed on the optical-electrical converter 12.

An electric signal obtained by the optical-electrical converter 12 is separated into a main signal and an auxiliary signal by a frequency by a demultiplexer 13, and the main signal is amplified by an amplifier 14 and output from an output terminal 15 to receive a received signal. Becomes Further, the level of the main signal is detected by the main signal detector 16 and fed back to the amplifier 14 for automatic gain control. On the other hand, the level of the auxiliary signal is detected by the auxiliary signal detector 17 and monitored by the level meter 18.

On the other hand, a part of the received light passes through the optical branching device 10, passes through the lens 19, and is condensed on the QPD (optical-electrical converter) 20 composed of four photodiodes, as shown in FIG. The spot S is imaged. The signal converted into the electric signal in each photodiode of the QPD 20 enters the auxiliary signal detector 21, and the position of the spot S can be obtained from the difference in the intensity of the received light.

Based on this signal, the mirror drive circuit 22 drives the movable mirror 8 so that the position of the spot S on the QPD 20 reaches the center, that is, the outputs of the photodiodes of the QPD 20 become equal. Change the angle. This changes the direction of the transmitted light beam,
When the position of the spot S on the QPD 20 is in the center,
The direction of the transmitted light beam matches the direction of the received light beam.
In this way, automatic tracking is performed so that the transmitted light beam always faces the opposite device.

[0007]

However, in the above-mentioned conventional example, in order to effectively utilize the high speed and wide band characteristics which are the features of optical communication, a light receiving element having a high speed response is used for the optical-electrical converter 12. In order to reduce the junction capacitance,
It is necessary to make the light receiving area extremely small, about 10 ^-2 mm ² . Therefore, the installation angle error of the device capable of receiving light becomes extremely small, and when adjusting the direction at the time of installation, the operator looks at the level meter 18 and manually adjusts until the start of swinging of the pointer is detected, and then The operation of activating automatic tracking is required.

However, the receivable angle range of the optical-electrical converter 12 is extremely narrow, and it becomes difficult to search for the deflection position of the pointer of the level meter 18. On the other hand, the light-receiving area of the QPD 20 is larger than the light-receiving area of the opto-electrical converter 12 by about two orders of magnitude, so when the opto-electrical converter 12 is not receiving light, the QPD 20 has already received light and the automatic tracking can be activated. However, there is a problem in that the operator has to continue the operation unnecessarily until the level meter starts to shake because the operator does not know it.

For this reason, if an attempt is made to monitor the output of the auxiliary signal detector 21 instead of the main signal detector 16, contrary to the above, the QPD 20 receives light and the level meter 18
The light-electricity converter 12
However, there is a problem that the main signal cannot be received because the light is not received.

Further, in this conventional example, since there is no function for checking whether or not this signal is normally modulated, when not only the received light intensity but also the level of this signal needs to be monitored, it is possible to cope with it. There is a problem that you can not.

An object of the present invention is to solve the above problems,
An object of the present invention is to provide an optical space communication device that improves the operability of direction adjustment and can monitor the operating state.

[0012]

An optical space communication apparatus according to the present invention for achieving the above object is an auxiliary signal generator for generating an auxiliary signal in a frequency band different from that of a main signal. A multiplexer for multiplexing signals, an electro-optical converter for converting a multiplexed signal output from the multiplexer into an optical signal, and a transmission optical system for converting the main signal into a light beam and transmitting the light beam. An optical space communication device comprising a transmitter and a receiving optical system for receiving an optical signal in the form of a light beam and a receiver having an optical-electrical converter for converting the optical signal into an electric signal, in which the receiving optical system is An optical branching device that branches the optical paths of the first optical-electrical converter and the second optical-electrical converter is provided, and the main signal converted into an electrical signal by the first optical-electrical converter is provided to the receiver. Converted to an electrical signal by the main signal detector for detection and the second optical-electrical converter Characterized in that provided an auxiliary signal detector for detecting the auxiliary signal.

[0013]

In the optical space communication device having the above-described structure, the auxiliary signal generator generates an auxiliary signal having a frequency band different from that of the main signal, and the multiplexer combines the main signal with the main signal. -It is converted into an optical signal by the optical converter, and is transmitted from the transmission optical system of the transmitter as a light beam to the partner device. The received light beam from the other device is received by the receiving optical system of the receiver, the main signal and the auxiliary signal are separated by the optical branching device provided in the receiving optical system, and the main signal is converted by the first optical-electrical converter. It is converted into an electrical signal and detected by the main signal detector, and the auxiliary signal is converted to the second optical signal.
The electric signal is converted into an electric signal by the electric converter and detected by the auxiliary signal detector. Optical space communication is performed by adjusting the direction while monitoring both signals.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 shows a block diagram of the first embodiment, in which an output of an input terminal 30 of a transmission electric signal which is a main signal is connected to a multiplexer 32 via an amplifier 31, and the multiplexer 32 is connected to the main signal. The output of an auxiliary signal generator 33 that generates an auxiliary signal set to a frequency lower than the frequency band of is connected. The output of the multiplexer 32 is connected to an electro-optical converter 34 including a semiconductor laser light source and a light emitting element such as a light emitting diode, and a lens 35, a polarization beam splitter 36, on the front optical path of the electro-optical converter 34. The movable mirrors 37 are sequentially arranged, and a collimating optical system 38 is arranged in the reflection direction of the movable mirror 37, so that transmission and reception with a light beam can be performed with an opposing device on the opposite side. The lens 35, the polarization beam splitter 36, the movable mirror 37, and the collimating optical system 38 form a transmission optical system.

In the reflection direction of the polarization beam splitter 36, an optical splitter 39 such as a half mirror, a lens 40, and a QPD 41 composed of four independently operating light receiving elements such as photodiodes are sequentially arranged. In the direction of reflection of the light, an optical-electrical converter 43 for converting a wideband optical signal into an electric signal by a lens 42 and a fast response type light emitting element such as an avalanche photodiode or a PIN photodiode.
Is arranged. The collimating optical system 38, the movable mirror 37, the polarization beam splitter 36, the optical splitter 43, and the lenses 40 and 42 form a receiving optical system.

The output of the optical-electrical converter 43 is connected to the output terminal 45 via the amplifier 44, the main signal detector 46 is connected between the amplifier 44 and the output terminal 45, and the signal of the main signal detector 46 is The gain is fed back to the amplifier 44 to perform automatic gain control. On the other hand, QPD41
The output of is an auxiliary signal detector 4 which detects a low frequency auxiliary signal.
7, the output of the auxiliary signal detector 47 is connected to the movable mirror 37 via the movable mirror drive circuit 48. The outputs of the main signal detector 46 and the auxiliary signal detector 47 are connected to the level meter 50 via the switch 49,
Both signals can be switched and monitored by the switch 49.

FIG. 2 is a block diagram of the auxiliary signal detector 47, showing four detectors 47a to 47d and seven calculators 51a.
It is formed from ˜51 g. The outputs of the four light receiving elements 41a to 41d of the QPD 41 are connected to the four detectors 47a to 47d of the auxiliary signal detector 47, respectively.
The output of the detection unit 47a is output to the calculation units 51a and 51b, and the output of the detection unit 47b is output to the calculation units 51b and 51c and the detection unit 47c.
Is connected to the calculation units 51c and 51d, and the output of the detection unit 47d is connected to the calculation units 51a and 51d.
The outputs of 1a and 51c are connected to the arithmetic unit 51e, and the outputs of the arithmetic units 51b and 51d are connected to the arithmetic units 51f and 51g. As a result, the output of the calculation unit 51e represents the vertical error signal, the output of the calculation unit 51f represents the horizontal error signal, and the output of the calculation unit 51g represents the light intensity signal, and these signals are the movable mirror drive circuit 48. It will be sent to.

When an electric signal for transmission is input from the input terminal 30, it is amplified to a predetermined level by the amplifier 31 and is added to the multiplexer 3.
Up to 2. An auxiliary signal is generated from the auxiliary signal generator 33, is combined with the main signal in the combiner 32, and this signal is converted into an optical signal in the electro-optical converter 34 and radiated. When a semiconductor laser light source is used for the electro-optical converter 34, the light is polarized, and if the polarization direction is set to be horizontal to the paper surface, the light is made parallel by the lens 35 and the polarization beam splitter 36 is used. Is transmitted to the collimating optical system 38, is reflected by the movable mirror 37, is converted into a light beam having a predetermined divergence angle, and is transmitted to the opposite device on the opposite side.

On the other hand, the received light beam from the other device enters the collimating optical system 38 from the same direction as the transmitted light beam, and if the polarization direction of this received light beam is set to be perpendicular to the paper surface, this light is polarized. The light is reflected by the bonding surface of the beam splitter 36, separated from the transmitted light, and reaches the optical splitter 39. Most of the received light beam is reflected by the optical branching device 39 as a main signal, and passes through the lens 42 to the opto-electric converter 4.
The light is condensed at 3, converted into an electric signal, amplified by the amplifier 44, and output from the output terminal 45. The main signal is detected by the main signal detector 46, and the level meter 50 is instructed by switching the switch 49. Then, a part of this light is fed back to the amplifier 44, and the amplifier 4 automatically
4 gain control is performed.

A part of the received light beam is an optical branching device 39.
To become an auxiliary signal, which is focused on the QPD 41 to form an image of the spot S. The spot S is divided into four independent light receiving elements 37a to 36d shown in FIG. 2 to be received, and the received light signal is detected by the detection section 47a of the auxiliary signal detector 47 connected to each of the light receiving elements 41a to 41d. ~
47d detects the detected values A to D, respectively. A + B, A + C, C + D, and B + D are respectively calculated from the detected values A to D in the calculation units 51a to 51d, and (A + B)-(C + D) is calculated in the calculation unit 51e to shift the lateral deviation of the spot S. The error signal shown is output and (A + C)-(B +
D) is calculated, an error signal indicating the vertical shift of the spot S is output, and (A + C) + at 51e.
(B + D) is calculated, and the optical signal intensity of the entire spot S is output. These shift signals are sent to the movable mirror drive circuit 48, and control is performed to rotate the movable mirror 37 so that the spot S reaches the center.

Instead of detecting each of the signals A to D and then performing addition and subtraction to obtain an error signal or the like, first, addition or subtraction is performed in the state of an AC signal, and then each signal is detected to obtain an error signal or the like. You can also do so.

The direction adjustment operation in the case where this apparatus is installed is manually performed after the level meter 50 is switched to the auxiliary signal detector 47 side by the switch 49. Since the light receiving elements 41a to 41d of the QPD 41 have a wide light receiving angle range, they can receive light relatively easily, and the operator can adjust the pointer of the level meter 50 up to the point where it moves. At this time, the light is not yet incident on the optical-electrical converter 43 and the main signal is not received, but if the QPD 41 receives the light, it becomes in a state where it can be automatically tracked. Therefore, a switch operation or the like is manually performed. If automatic tracking is activated, the direction of the transmitted light beam is automatically adjusted so that the angles of the transmitted light beam and the received light beam match, and the transmitted light beam points in the direction of the other device.
The optical-electrical converter 43 also enters a normal communication state for receiving light, and the direction adjustment is completed.

In this way, after the direction adjustment is completed, even if the angle of the device changes due to vibration, external force, etc., the automatic tracking function works to maintain this communication state, so that the main signal is reliably received. In order to confirm whether or not it is present, the switch 49 is switched to the main signal detector 46 side to check the reception level of the main signal. The switch 49 may be manually operated or may be linked with the automatic tracking function.

The monitor of the auxiliary signal by the auxiliary signal detector 47 shows the intensity of the light incident on the lens of the collimating optical system 38, and the received light beam mainly from the partner device normally reaches its own device. The main signal detector 46 monitors the main signal to determine whether or not the main signal is normally received.

For example, when the S / N ratio of the main signal is low and the reception condition is bad, the monitor from the auxiliary signal indicates that the arrival beam intensity from the partner device is a normal value, but When the monitor indicates that the reception level of the main signal is lower than the normal value, the optical adjustment may be performed due to the direction adjustment error of the device itself or the position adjustment error between the QPD 41 and the opto-electric converter 43. -The light is not normally incident on the electrical converter 43, or there is something wrong with the input of the main signal to the other party device, and the level of the transmitted main signal itself may be low.

As described above, the level meter 50 can be switched by the switch 49 to easily compare the instructions of these monitors, so that the operating state of the apparatus can always be evaluated accurately, and the diagnosis at the time of abnormality can be performed. It can be dealt with easily and the operability and reliability of the device are improved. Further, in this embodiment, the demultiplexer 13 and the auxiliary signal detector 17 used in the conventional example of FIG. 4 are not required, which is advantageous in terms of the cost and size of the device.

FIG. 3 shows a second embodiment, which is the same as the first embodiment except that the demultiplexer 13 and the auxiliary signal detector 17 shown in the conventional example are provided in the first embodiment. The same reference numeral indicates the same member. That is, a demultiplexer 52 that separates a main signal and an auxiliary signal according to frequency is provided between the opto-electric converter 43 and the amplifier 44 in the first embodiment of FIG. 1, and the output of the demultiplexer 52 is an auxiliary. It is connected to the switch 54 via the signal detector 53. The switch 54 is provided with an additional terminal from the auxiliary signal detector 53 in addition to the switch 49 of the first embodiment, so that the switch 54 is a three-point switch.

By doing so, the optical-electrical converter 43 is formed.
It becomes possible to monitor the intensity of light incident on
Even when the intensity of light incident on D41 is normal and the level of the main signal is lowered, there is a cause on the device side such that light is not normally incident on the optical-electrical converter 43 due to an adjustment error or the like. It is possible to determine the cause of the partner device such as an abnormality in the main signal, and more accurately evaluate the operation state.

In the first and second embodiments, the signals from the auxiliary signal detectors 47 and 53 and the main signal detector 46 are monitored by the level meter 50. You may monitor by the method using sound, sound, etc.

Instead of the operator watching or listening to the instruction on the monitor to operate, a device for automating the operation is equipped with a CPU or the like, and the monitor signal is used as a control signal for scanning. After automatically supplementing the received light with, for example, the automatic operation is performed according to the sequence programmed to move to the automatic tracking operation, or after the CPU determines the abnormality, the operation routine is moved to the automatic operation. Good.

Further, these monitor signals can be used not only in the apparatus but also as a control signal when transmitted to another place and operated manually or automatically by remote control.

[0032]

As described above, in the optical space communication device according to the present invention, the received light from the other device is separated by the optical branching device, and the main signal is detected by the first optical-electrical converter. By monitoring the main signal level and detecting the auxiliary signal by the second optical-electrical converter to monitor the error signal, the operability and the operability of direction adjustment are improved, and the operating state of the device can be easily monitored. This makes it possible to form a device that is more reliable in terms of cost and capacity.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 is a configuration diagram of an auxiliary signal detector.

FIG. 3 is a configuration diagram of a second embodiment.

FIG. 4 is a configuration diagram of a conventional example.

FIG. 5 is an explanatory diagram of spots on an optical-electrical converter.

[Explanation of symbols]

 32 multiplexer 33 auxiliary signal generator 34 electric-optical converter 36 polarization beam splitter 37 movable mirror 38 collimating optical system 39 optical splitter 41, 43 optical-electrical converter 46 main signal detector 47, 53 auxiliary signal detector 48 mirror drive circuit 49, 54 switching device 50 level meter 52 demultiplexer

Claims (5)

[Claims] 1. An auxiliary signal generator for generating an auxiliary signal in a frequency band different from that of a main signal, a multiplexer for combining the main signal and the auxiliary signal, and an optical combined signal output from the multiplexer. Electric-optical converter for converting into a signal, a transmitter having a transmitting optical system for converting the main signal into a light beam and transmitting the same, a receiving optical system for receiving a light beam-like optical signal, and an electric signal for the optical signal In an optical space communication device including a receiver having an optical-electrical converter for converting into a signal, an optical path of a first optical-electrical converter and a second optical-electrical converter is branched to the receiving optical system. An optical branching device is provided, and a main signal detector that detects a main signal converted into an electric signal by the first optical-electrical converter is provided in the receiver, and an electric signal is converted by the second optical-electrical converter. Optical space communication provided with an auxiliary signal detector for detecting an auxiliary signal apparatus. 2. The receiver includes a demultiplexer for separating the electric signal converted by the first optical-electrical converter into a main signal and an auxiliary signal, and the main signal separated by the demultiplexer. The optical space communication device according to claim 1, further comprising a main signal detector that detects the auxiliary signal and an auxiliary signal detector that detects the auxiliary signal. 3. The optical space communication device according to claim 1, wherein the transmitting optical system and the receiving optical system have a common collimating optical system. 4. The second optical-electrical converter comprises an optical deflector configured by a plurality of light receiving elements and changing the transmission direction of a light beam based on electric signals from the plurality of light receiving elements. Item 1. The optical space communication device according to Item 1. 5. The optical space communication device according to claim 1, further comprising a level meter for monitoring a detection output signal of either or both of the main signal detector and the auxiliary signal detector.