JPH01138542A - Direct injecting method for light information of pulse modulation optical communication - Google Patents

Abstract

PURPOSE:To improve the reliability of a communicating function by interposing an optical separator and an acoustooptic effect element in the middle of a pulse modulation optical communication path, applying an ultrasonic wave to the acoustooptic effect element in synchronism with the synchronizing signal of a light signal extracted by the optical separator, deflecting the pulse modulation optical signal and injecting new information. CONSTITUTION:The optical separator 9 and acoustooptic effect element 7 are interposed in the middle of the pulse modulation optical communication path, and the ultrasonic wave 5 is applied to the acoustooptic effect element 7 in synchronism with the synchronizing signal of the light signal extracted by the optical separator 9. The acoustooptic element 7 functions to deflect light, so a compressional standing wave is generated in the acoustooptic element 7 and incident light is diffracted primarily in a reflection angle direction like mirror surface reflection, so that a pulse-modulated light signal is absent only while the signal 5 is inputted to the acoustooptic element 7. Namely, part of the pulse-modulated light signal in the process of transmission is made absent to discard an unnecessary signal or vary the light signal, thereby sending the signal as a new signal. Consequently, the reliability of the communicating function is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an information relay/processing method that is effective when a part of information is not extracted or new information is not injected in the middle of a pulse modulated optical communication path.

(Prior technology) With the advancement of optoelectronic technology and the practical use of low-loss optical fibers, optical communication methods have become popular for long-distance, large-capacity information transmission, and for information transmission in strong electromagnetic fields because they are not affected by electromagnetic fields in the middle of the transmission path. 9 For example, optical fiber transmission lines are installed in places where high-voltage transformers are installed, along railway lines, along power lines, etc. A relay is being carried out.

In such optical communications, if you want to extract some information or inject new information midway through the communication path, conventionally,
As shown in FIG. 4, first, all optical information is converted into electrical quantities by a photoelectric converter 102, and then necessary information 104 is extracted by a demodulator 103, and a signal 105 to be injected is extracted by a demodulator 103.
The signals are mixed and modulated by a mixer 106 and a transducer 107, and then converted into optical information by an electro-optical converter 108 and sent out.

Note that 101 is an input optical fiber, and 109 is an output optical fiber. Incidentally, FIG. 5 shows an example of signal waveforms at various parts of the apparatus shown in FIG. 4, where ■ indicates an input signal, ■ indicates signal extraction, ■ indicates signal extraction, and ■ indicates an output signal.

(Problems to be Solved by the Invention) However, according to the conventional signal injection method, all information is once converted into electrical quantities before extraction and injection, and many electronic circuits 102, 103... ....

108, if one of these electronic circuits fails or the power supply circuit that drives these electronic circuits fails, all communication functions will stop.

Therefore, in order to improve the reliability of these electronic circuits, complicated guarantee circuits are added to these circuits or circuits are duplicated, making the equipment large-scale, complex, and expensive. ing.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a direct optical information injection method that can extract information and inject new information without performing photoelectric conversion at any location along a pulse modulated optical communication path. do.

(Means for Solving the Problems) In order to achieve the above object, the optical information direct injection method of the present invention inserts an optical separator and an acousto-optic effect element in the middle of a pulse modulated optical communication path, and Inject new information without photoelectrically converting the main communication information by applying ultrasonic waves to the acousto-optic effect element in synchronization with the synchronization signal of the optical signal extracted by the device and deflecting the pulse modulated optical signal. I try to do that.

(Function) The acousto-optic element has the function of redirecting light, and as shown in Fig. 3, the light is incident on the acousto-optic element 7 at a fixed angle, which is determined by the material and dimensions of the acousto-optic element. When an electrical signal 5 of a certain frequency is applied through the electrode 8, a dense standing wave is generated in the acousto-optic element 7, and the incident light is first-order diffracted in the direction of the reflection angle, like specular reflection. Of course, if there is no signal 5, the incident light will be transmitted in the same direction.

Therefore, the pulse modulated optical signal is lost only during the time that the signal 5 is input to this acousto-optic element. That is, by dropping a part of the pulse modulated optical signal that is being transmitted, unnecessary signals can be discarded or the optical signal can be changed and transmitted as a new signal.

(Example) Hereinafter, the configuration of the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 shows an example of a pulse modulated optical information direct injection device for implementing the method of the present invention. In the isolation system, 1 is an input optical fiber, 2 is a photoelectric converter, 3 is a demodulator, 4 is an extraction signal, 5 is an injection signal, 6 is an output optical fiber, 7 is an acousto-optic element, 8 is an electrode, and 9 is an optical fiber. Separator 10 is a transparent optical medium.

The optical separator 9 has a lens function and a half mirror function,
A part of the pulse modulated light information, for example about 10%, is extracted. Optoelectrical converter (0/E) 2 and demodulator (D
M) 3 converts the signal extracted by the optical separator 9 into an electrical signal and then extracts the original signal wave. This extracts the synchronization signal and the necessary signals.

The acousto-optic element 7 has an acousto-optic effect in which a refractive index change occurs in accordance with the wavelength of the ultrasound due to the photoelastic effect caused by the propagation of the ultrasound, and light that crosses the change is diffracted, that is, an acousto-optic effect. This acousto-optic material is generally Te
O2, Te, AsySe55Ge33, Ag3 Ss
Glasses such as , Ag3 Sea, and amorphous Se are known, but are not limited to these and include all those having an acousto-optic effect.TeO2 is usually suitable as a medium for visible light. In addition, when using an infrared laser beam as a light source, As-8e-Ge glass, G
Optical deflector media of E, Te, and GaAs are suitable. In addition, the comb-like shape of the acousto-optic element 7! Ultrasonic waves are generated by applying signal 5 to @8.

The transparent optical medium 10 is used to prevent interference between the transmitted light that has passed through the acousto-optic element 7 and the first-order diffracted light, and provides a certain distance between the acousto-optic element 7 and the output optical fiber 6. Any material may be used as long as it is optically transparent.For example, a material such as quartz glass is generally used, but an air layer may be used instead.

That is, the acousto-optic element 7 and the output optical fiber 6 may be installed at a certain interval. In this case, in order to suppress connection loss, the input end face of the optical fiber 6 and the end face of the acousto-optic element are parallel to each other. It is necessary to install it as follows.

The optimum incident angle (θi), signal frequency (fs), etc. for the acousto-optic element 7 are determined by the material and dimensions of the acousto-optic element 7, and the wavelength (λ) of the incident light.
When using e-Ne gas laser light (λ=632.8 nl), in a normal acousto-optic element, the incident angle is about several nrad and the signal frequency is about several 108H7. In addition, in order to prevent interference between the transmitted light and the first-order diffracted light, the observation point of the transmitted light, for example, the attachment point of the output side fiber 6, is separated by about 10 cm from the acousto-optic element 7, and pulse modulated light information of about 1 ONb is injected. is possible. Therefore, the thickness of the transparent optical medium 10 is preferably about 10 am.

According to the device configured as described above, information can be extracted and new information can be injected at any location along the optical communication path.

For example, when a PCM modulated optical signal as shown in FIG. A part (approximately 10%) of the
Then, the demodulator 3 extracts the 11 synchronization signal and the necessary signals [Fig. 2 (■)]. On the other hand, most of the signals (the remaining approximately 90
%) is incident on the acousto-optic element 7. Here, the signal 5 to be injected (■ in FIG. 2) is applied to the acousto-optic element 7 via the electrode 5 after a predetermined time delay from the previous synchronization signal. Then, the refractive index of the acousto-optic element 7 changes to cause first-order diffraction, causing the electrical signal passing through it to drop out of the optical communication path. That is, only unnecessary signals and information are extracted. Further, the unpolarized light passes through the transparent optical medium 10 and enters the transmitted light into the output optical fiber 6. By doing this, the signal in the output optical fiber 6 is converted into a digital signal different from the original signal, that is, an injection signal is added to the input signal, as shown in FIG. Sent as new status information.

(Effects of the Invention) As is clear from the above explanation, the present invention provides a method for inserting an optical separator and an acousto-optic effect element in the middle of a pulse modulated optical communication path, and synchronizing optical signals extracted by the optical separator. Ultrasonic waves are applied to the acousto-optic effect element in synchronization with the signal, and new information is injected by deflecting the pulse modulated optical signal, without converting the pulse modulated optical signal into an electrical signal. Information can be extracted or new information can be injected at any point during transmission without change. Moreover, compared to conventional devices, the number of active electronic circuits is reduced, and the main optical signal path is comprised of integrated passive optical elements.

Therefore, its reliability is high, and even if a failure occurs in the electronic circuit or the power supply circuit that drives it, it will simply become impossible to extract or inject the signal at that point, and the main optical communication signal will not be affected in any way. It has no effect. In other words, it is thought that the reliability of the entire optical communication system will be significantly improved, and devices can be expected to be smaller, simpler, and lower in price.

Note that the optical propagation loss within an acousto-optic element is about 10%, so assuming that there is a loss of about 20% each time this device is inserted in the middle of the optical communication path, the amount of light emitted from the initial Assuming that the sensitivity of each photoelectric converter and demodulator is up to 1% of that, up to 10 of this device can be inserted in series.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an optical information extraction/injection device according to the present invention, and FIG. 2 is an example of signal waveforms at various locations in the device. FIG. 3 is a diagram illustrating the optical function of the acousto-optic device. FIG. 4 is a block diagram of a conventional optical communication relay/processing system, and FIG. 5 is an example of signal waveforms in each device. 1... Input side optical fiber, 2... Photoelectric converter,
3... Demodulator, 4... Extraction signal, 5... Injection signal, 6... Output side optical fiber, 7... Acousto-optic element, 9... Optical separator. 1WI Figure 2 Figure 5 ■ Input signal period signal i

Claims (1)

[Claims] An optical separator and an acousto-optic effect element are inserted in the middle of a pulse-modulated optical communication path, and an ultrasonic wave is applied to the acousto-optic effect element in synchronization with a synchronization signal of the optical signal extracted by the optical separator. A method for directly injecting optical information in pulse modulation optical communication, characterized by injecting new information by deflecting a modulated optical signal without photoelectrically converting main communication information.