JPH05191361A - Optical space transmission system - Google Patents

Abstract

PURPOSE:To obtain the transmission system in which 2-way communication is attained with a single light emitting element. CONSTITUTION:An information signal entering a master set 1 is a modulation signal by a modulator 3, which drives a light emitting element 4 and it sends a signal light toward a light receiving element and a corner cube 7 of a slave set 2. Since the light striking with the corner cube 7 is reflected by a master set 1, the optical axis is adjusted by adjusting the direction of the master set so as to maximize the respectively level of the master set 1. On the other hand, the signal light made incident in the light receiving element 5 of the slave set 2 is detected by the light receiving element 5 and the information signal is reproduced by a demodulator 6. The information signal entering the slave set 2 is modulated by a modulator 8 to control an optical shutter 9. Since the light from the master set 1 is made incident in the corner cube 7, the modulation signal light is sent to the master set 1 by controlling the reflected light with the optical shutter 9. The master set 1 receives the light by the light receiving element 10 and the light is converted into an electric signal and a demodulator 11 reproduces the information signal.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical space transmission system, and more particularly to an optical space transmission system used for wireless communication and spread spectrum communication. For example, it is applied to wireless data transmission in a short distance.

[0002]

2. Description of the Related Art The conventional optical space transmission system has a problem that the device becomes large in size because each communication station is provided with a positioning device for a transmitting / receiving station when communicating with each other. In order to solve this point, for example, Japanese Patent Publication No. 3-65
The "optical space transmission system" proposed in Japanese Patent Publication No. 061 is
In order to control the azimuth, control is performed using the corner cube only in one direction, and in the other direction, azimuth control is performed by communication data. However, since data transmission still requires light emitting elements for both of them, there is a problem that power consumption increases.

[0003]

An object of the present invention is to provide a transmission method capable of bidirectional communication with a single light emitting element in an optical space transmission system, in view of the above circumstances.
Only the master unit has the optical axis adjustment function, and the slave unit does not need to adjust the optical axis, which simplifies the circuit configuration of the slave unit. The purpose of the present invention is to provide an optical space transmission system that is less likely to be affected by.

[0004]

In order to achieve the above object, the present invention provides (1)
A modulator for converting the information signal into a modulated signal, and a light emitting element for converting the modulated signal converted by the modulator into an optical signal,
A light receiving element that converts the reflected light into an electric signal, a master unit that includes a demodulator that demodulates an information signal from the signal of the light receiving element, and a corner cube that reflects the signal light from the master unit in the arrival direction. An optical shutter provided on the front surface of the corner cube for modulating signal light, and an optical modulator for generating a modulation signal for controlling the optical shutter from an information signal,
A light receiving element that converts the signal light from the master unit into an electric signal, and a slave unit that includes a demodulator that demodulates an information signal from the signal of the light receiving element, and from the slave unit to the master unit The transmission is controlled by the optical shutter when the signal light from the master unit is reflected, and (2) a spread spectrum modulator including a voltage controlled oscillator and a PN code generator is used as the modulator. As the demodulator, a PN code generator, a correlation unit for performing a correlation operation between a signal from the light receiving element and the PN code, a loop filter for converting a correlation output of the correlation unit into a control signal, and the PN code generation Using a spread spectrum demodulator consisting of a voltage controlled oscillator for controlling the clock frequency of the device and for synchronous tracking, and
(3) A spread spectrum modulator including a clock generator, a clock phase modulator and a PN code generator is used as the modulator, and a PN code generator, a signal from the light receiving element and a PN code are used as the demodulator. , A loop filter for converting the correlation output of the correlator into a control signal, a voltage controlled oscillator for controlling the clock frequency of the PN code generator for synchronous tracking, and the loop filter output. A spread spectrum demodulator comprising a comparator for reproducing an information signal from the optical receiver, and (4) in (2) or (3) above, in the demodulator of the slave unit, before the light receiving element. Provide an optical shutter, P
The received light is modulated by the output of the N code generator, and the modulated light is detected by the light receiving element to perform the correlation calculation. The oscillating frequency of the voltage controlled oscillator is controlled by using the loop signal for the correlation signal to perform PN code synchronous tracking, and further,
(5) In any one of the above (1) to (4), in the parent device, an optical signal from a light emitting element is reflected by a child device and is incident on a light receiving element, and the orientation is based on an output signal of the light receiving element. It is characterized by performing control. Hereinafter, description will be given based on examples of the present invention.

FIG. 1 is a block diagram for explaining an embodiment of an optical space transmission system according to the present invention, in which 1 is a master unit and 2 is a master unit.
Is a slave unit, 3 is a modulator, 4 is a light emitting element, 5 is a light receiving element, 6
Is a demodulator, 7 is a corner cube, 8 is a modulator, 9 is an optical shutter, 10 is a light receiving element, and 11 is a demodulator. First, consider a case where information is transmitted from the master unit to the slave unit. Base unit 1
The incoming information signal undergoes various modulations by the modulator 3 to become a modulation signal, which drives the light emitting element 4. The light emitting element 4 has a sharp directivity, and sends a signal light toward the light receiving element 5 and the corner cube 7 of the slave unit 2. Since the light of the signal light that hits the corner cube 7 is reflected by the base unit 1, the optical axis is adjusted by adjusting the direction of the base unit so that the reception level of the base unit 1 is maximized. On the other hand, the signal light incident on the light receiving element 5 of the slave unit 2 is detected by the light receiving element 5 and the information signal is reproduced by the demodulator 6. As the modulation / demodulation method used here, various methods such as frequency modulation, phase modulation, amplitude modulation, pulse modulation, spread spectrum modulation and the like can be considered.

Next, consider a case where information is transmitted from the child device to the parent device. The information signal that has entered the slave unit 2 is modulated by the modulator 8 and controls the optical shutter 9. Since the light from the base unit 1 (which may be continuous light or a continuous pulse train in the receiving state) is incident on the corner cube 7, the modulated signal light is controlled by the optical shutter 9 by controlling the reflected light. To transmit. In the parent device 1, the light receiving element 10 receives the light, converts it into an electric signal, and the demodulator 11 reproduces the information signal.

2 (a) and 2 (b) are views showing an embodiment (claim 2) in which a spread spectrum system is introduced into a modulator / demodulator, wherein FIG. 2 (a) is a modulator and FIG. 2 (b) is a demodulator. It is a block diagram of. In the figure, 21 and 25 are voltage controlled oscillators, 22 and 26 are PN code generators, 23 is a correlator, and 24 is a loop filter. The embodiment shown in FIG. 2 is an embodiment showing a method in which a driving clock frequency of a PN code has an information signal. In the modulator shown in FIG. 2A, the voltage control oscillator 21 is controlled by the information signal to generate an oscillation frequency. Of the clock signal, the PN code generator 22 is driven by the clock signal to generate a spread modulation signal. In the demodulator shown in FIG. 6B, a PN code generator 26 that generates a PN code that obtains the correlation characteristic required for synchronization with the PN code on the transmission side is prepared, and the correlation between the output of the PN code generator and the received signal is provided. Is obtained by the correlator 23, and the correlation output of the correlator 23 is calculated by the loop filter 2
4 is used as a control signal to control the voltage controlled oscillator 25 to follow the synchronization of the code, and the control signal is extracted and used as a demodulation signal.

3 (a) and 3 (b) are diagrams showing another embodiment (claim 3) in which a spread spectrum system is introduced into a modulator / demodulator, wherein FIG. 3 (a) is a modulator and FIG. It is a block diagram of a demodulator. In the figure, 31 is a clock generator, 32 is a clock phase modulator, 33 and 37 are PN code generators, 34 is a correlator, 35 is a loop filter, 36 is a voltage controlled oscillator, 3
Reference numeral 8 is a comparator. The embodiment shown in FIG. 3 is an embodiment showing a system in which a driving clock phase of a PN code is provided with an information signal. In the modulator shown in FIG. 3A, the clock phase modulator 32 is controlled by the information signal and the phase is changed. A modulated clock signal is generated, and PN is generated by this clock signal.
The code generator 33 is driven to generate a spread modulation signal. In the demodulator shown in FIG. 2B, a PN code generator 37 is provided which generates a PN code that provides a correlation characteristic required for synchronization with the PN code on the transmission side, and the output of the PN code generator 37 and the received signal are received. The correlation is obtained by the correlator 34, the correlation output of the correlator is used as the control signal through the loop filter 35, the voltage controlled oscillator 36 is controlled to follow the synchronization of the code, and the control signal is taken out to obtain the hysteresis comparator 3.
A demodulated signal is obtained by passing through 8.

FIG. 4 is a diagram showing another embodiment (claim 4) of the synchronization control loop section in the demodulator, in which 41 is an optical shutter, 42 is a light receiving element, 43 is a loop filter, and 4 is a loop filter.
Reference numeral 4 is a voltage controlled oscillator, and 45 is a PN code generator. In the embodiment shown in FIG. 4, the received light is turned on and off by the optical shutter 41 controlled by the PN code before being detected by the light receiving element 42.
Then, the logical product operation is performed, and thereafter, the light receiving element 42 detects the detected signal, which is used as a control signal through the loop filter 43, and the voltage controlled oscillator 44 is controlled to synchronize the PN code.

FIG. 5 is a diagram showing another embodiment of the master unit, in which 51 is the master unit, 52 is a light emitting element, 53 is a light receiving element, and 5 is a light receiving element.
Reference numeral 4 is a direction control device, and 55 is a slave. The embodiment shown in FIG. 5 relates to a method for controlling the direction so that the signal light from the master unit 51 strikes the slave unit 55 accurately, and the signal light emitted from the light emitting element 52 is reflected by the slave unit 55. When entering the light receiving element 53, the direction of the master unit is controlled by the direction control device 54 so that the light receiving level becomes maximum.

[0011]

As is apparent from the above description, the present invention has the following effects. (1) Effect corresponding to claim 1; Since the corner cube and the optical shutter are used, bidirectional communication is possible without using a light emitting element in the child device. Therefore, the power consumption of the slave unit can be reduced and the circuit can be simplified. In addition, there is almost no need to adjust the optical axis of the child device by the corner cube. (2) The effect corresponding to claim 2; Since the spread spectrum modulation of the type for modulating the drive clock frequency of the PN code is performed for modulation and demodulation, the confidentiality of information, the resistance to interference, and the multiplexing of communication are excellent. (3) Effect corresponding to claim 3; Since the spread spectrum modulation of the form of modulating the drive clock phase of the PN code is performed for modulation and demodulation, it is excellent in confidentiality of information, anti-interference property, and multiplexing of communication. In addition, all the transmitters can be digital circuits. (4) Effect corresponding to claim 4; Correlation calculation is performed by using the optical shutter in front of the light receiving element, and therefore, a correlator composed of a normal multiplier and an integrator is not required, so that the circuit configuration of the demodulation unit is easy. become. (5) Effect corresponding to claim 5: Since the bearing control device automatically controls the bearing of the master unit with respect to the slave unit, there is no need to adjust the optical axis, and the installation becomes easy.

[Brief description of drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of an optical space transmission system according to the present invention.

FIG. 2 is a diagram showing an embodiment in which a spread spectrum system is introduced into a modulator / demodulator.

FIG. 3 is a diagram showing another embodiment in which a spread spectrum system is introduced into a modulator / demodulator.

FIG. 4 is a diagram showing another embodiment of the synchronization control loop unit in the demodulator.

FIG. 5 is a diagram showing another embodiment of the parent device.

[Explanation of symbols]

1 ... Parent device, 2 ... Child device, 3 ... Modulator, 4 ... Light emitting element, 5 ...
Light receiving element, 6 ... Demodulator, 7 ... Corner cube, 8 ... Modulator, 9 ... Optical shutter, 10 ... Light receiving element, 11 ... Demodulator.

─────────────────────────────────────────────────── ───Continued from the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04B 10/10 10/22 H04J 13/00 A 7117-5K

Claims (5)

[Claims] 1. A modulator for converting an information signal into a modulated signal, a light emitting element for converting the modulated signal converted by the modulator into an optical signal, a light receiving element for converting reflected light into an electric signal, and the light receiving element. A master unit consisting of a demodulator that demodulates an information signal from the signal of the element, a corner cube that reflects the signal light from the master unit in the incoming direction, and the signal light provided in front of the corner cube An optical shutter for controlling the optical shutter, an optical modulator for generating a modulation signal for controlling the optical shutter from an information signal, a light receiving element for converting the signal light from the master unit into an electrical signal, and information from the signal of the light receiving element. A slave unit including a demodulator that demodulates a signal, and transmission from the slave unit to the master unit is controlled by the optical shutter when the signal light from the master unit is reflected. Optical space transmission method. 2. The voltage-controlled oscillator and P are used as the modulator.
A spread spectrum modulator including an N code generator is used, and as the demodulator, a PN code generator, a correlation unit that performs a correlation calculation between a signal from a light receiving element and a PN code, and a correlation output of the correlation unit are controlled. 2. The optical space transmission according to claim 1, wherein a spread spectrum demodulator comprising a loop filter for converting into a signal and a voltage controlled oscillator for controlling the clock frequency of the PN code generator to follow the synchronization is used. method. 3. A spread spectrum modulator including a clock generator, a clock phase modulator and a PN code generator is used as the modulator, and a PN code generator and a signal from a light receiving element are used as the demodulator. A correlator for performing a correlation calculation of a PN code, a loop filter for converting a correlation output of the correlator into a control signal, a voltage controlled oscillator for synchronously tracking the clock frequency of the PN code generator, and the loop. 2. The optical space transmission system according to claim 1, wherein a spread spectrum demodulator including a comparator for reproducing an information signal from a filter output is used. 4. In the demodulator of the slave unit, an optical shutter is provided in front of the light receiving element, the received light is modulated by the output of the PN code generator, and the modulated light is detected by the light receiving element to perform correlation calculation. Do it. 4. The optical space transmission system according to claim 2, wherein the correlation signal is controlled by a loop filter to control the oscillation frequency of the voltage controlled oscillator to follow the PN code synchronously. 5. The master unit, wherein an optical signal from a light emitting element is reflected by a slave unit and is incident on a light receiving element, and azimuth control is performed based on an output signal of the light receiving element. The optical space transmission system according to any one of 4 to 4.