JPS6012532A - Optical signal processing device - Google Patents

Abstract

PURPOSE:To improve an error rate by diffracting a waveguide light by the mutual action of a waveguide light guided in wave by an optical waveguide means and a surface acoustic wave excited by a surface acoustic wave transducer, also thinning out partially electrode fingers for forming a comb-shaped electrode, and diffracting it to plural discontinuous directions. CONSTITUTION:A waveguide light 12 sent out of a semiconductor laser 10 to an optical waveguide 2 formed on an elastic body substrate 1 is diffracted by a surface acoustic wave 14 sent out by a surface acoustic wave transducer 13 constituted of comb-shaped electrodes 3, 4, and the light is guided in wave to four separated diffracted angle directions and converted to diffracted lights 121, 122, 123 and 124, and when photodetectors 111, 112, 113 and 114 are installed so as to react to these respective waveguide lights, electric signal outputs 151, 152, 153 and 154 are obtained. When such an optical signal processing device is used, four frequencies of four FSK communicating systems are separated, and a spurious signal can be eliminated. Also, by processing digitally an electric output, four FSK codes can be demodulated by a small error rate.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical control device that forms a diffraction grating on an optical waveguide using surface acoustic waves and controls guided light.

Conventional configuration and its problems If the two-page method is used for surface acoustic waves to perform optical deflection, optical modulation, etc., the diffraction angle of the guided light can be changed by changing the frequency of the surface acoustic wave. By driving the surface acoustic wave transducer with various signals, the frequency components included in these signals can be detected as changes in the position of the guided light. Using this principle, a real-time spectrum analyzer can be created. If this is applied, for example, FSK communication system (Frequency 5hi
ft Keying ) demodulator can be constructed. In this method, multiple frequencies, usually around 4, are transmitted simultaneously, but if frequencies other than these are input, unnecessary diffraction of light occurs, which becomes noise, and light that is diffracted at the main frequency is transmitted at the same time. Since the intensity is reduced, the influence of noise is reduced to 3.
This has the disadvantage that the demodulation error rate increases as the signal strength increases. In this way, when all input signals are converted into surface acoustic waves by the surface acoustic wave converter, unnecessary frequencies become noise, which impedes accurate signal processing.

OBJECTS OF THE INVENTION It is an object of the present invention to improve the error rate of signal processing by removing unnecessary signals in the optical control signal processing device as described above by devising a surface acoustic wave converter.

Structure of the Invention The present invention provides an optical waveguide formed on the surface of an elastic substrate;
The surface acoustic wave transducer includes a comb-shaped electrode formed on the surface of the elastic substrate, and the surface acoustic wave converter includes a surface acoustic wave transducer including a comb-shaped electrode formed on the surface of the elastic substrate, and the surface acoustic wave In addition to diffracting the guided light, the electrode fingers forming the comb-shaped electrode are partially thinned out, and the guided light is diffracted in a plurality of discontinuous diffraction angle directions.

DESCRIPTION OF THE EMBODIMENTS The basic configuration of the present invention is shown in FIG. The surface acoustic wave 7 transmitted onto the elastic substrate 1 by the surface acoustic wave transducer consisting of the comb-shaped electrodes 3 and 4 causes periodic unevenness formed on the substrate surface or periodic refractive index changes near the surface. The surface state acts as a diffraction grating on light, causing black diffraction. At this time, the incident light 6 that enters the diffraction grating due to the surface wave is reflected by the diffraction grating and becomes reflected light 6'.

At this time, the reflection angle of the reflected light 6' with respect to the diffraction grating is determined by the periodic length of the grating caused by the surface acoustic wave, so the reflected light can be deflected by changing the signal frequency to the surface acoustic wave converter.0 This principle can be used to analyze the spectrum of the signals input to the comb-shaped electrodes 3 and 4, and a real-time spectrum analyzer has been realized as an optical spectrum analyzer. However, in normal communication systems, a limited number of frequencies are often used. Therefore, if a filter that passes only the necessary frequencies in a surface acoustic wave transducer can be realized and unnecessary signals can be removed, the noise characteristics of the communication system can be improved.

Page 6 On the other hand, the frequency characteristics of a regular electrode in which the overlapping lengths of the electrode fingers of the two comb-shaped electrodes are all equal are -X/X. Here, X=Nπ(f-fo)/f0, f is the frequency, f
o is the maximum response frequency of the electrode, and 2N is the number of electrode fingers.

Electrode fingers 3a of the regular type electrodes 3 and 4.

When the structure of the present invention as shown in FIG. 2 is obtained by thinning out 4a periodically, the frequency response thereof has a discontinuous and periodic frequency response as shown in FIG. If a signal with discontinuous frequency components is input to a surface acoustic wave converter in response to such a response, unnecessary spurious signals will not be removed, and a high-performance optical signal processing device will be required. realizable.

FIG. 4 is a diagram showing an optical signal processing device according to an embodiment of the present invention. Guided light 1 is transmitted from a light source such as a semiconductor laser 10 to an optical waveguide 2 formed on an elastic substrate 1.
2 is diffracted by a surface acoustic wave 14 sent out by a surface acoustic wave transducer 13 composed of multiple comb-shaped electrodes 3 and 4 shown in detail in FIG. The light is guided to form diffracted lights 121, 122, 123°6 Page 124. The light receiving element 1 corresponds to each of these guided lights.
If 11, 112, 113, and 114 are installed, electrical signal outputs 151, 162, 153, and 164 will be obtained. If such an optical signal processing device is used, for example, it is possible to separate the four frequencies of the 4FSX communication system and remove spurious signals. By digitally processing the electrical output, the 4FSX code can be demodulated with a small error rate. In addition, when four frequency signals each having an amplitude modulation are given as input, each diffracted light becomes an optical signal whose intensity is modulated, and the electric output terminal 1
61 to 164 can obtain different modulated signals at the same time. In this way, the present optical signal processing device can also be applied to a multiplex communication system, and in this case as well, unnecessary signals other than the desired signal are removed and an output signal with less noise can be obtained.

Effects of the Invention By using the optical signal processing device of the present invention, it is possible to use a communication system that separates frequencies and transmits signals at very high speed.
It is possible to perform demodulation with 7 pages with excellent noise characteristics, and in systems that transmit frequency multiplexed signals, multiplexed signals can be separated in real time into parallel signals. By modulating the signals, the signals of each channel can be switched, modified, or demodulated at high speed. In addition, by appropriately controlling the temporal period of the input signal to the light source and the surface acoustic wave transducer, it becomes possible to realize various signal processing elements, and the field of industrial application is extremely wide, making it an effective signal processing means. It provides:

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the present invention in detail, FIG. 2 is a diagram for explaining the main parts of a surface acoustic wave transducer according to an embodiment of the present invention, and FIG. 3 is a diagram for explaining the surface acoustic wave transducer according to an embodiment of the present invention. FIG. 4 is a diagram showing the frequency response characteristics of a wave transducer, and is a schematic diagram of a surface acoustic wave transducer according to an embodiment of the present invention. 1... Elastic substrate, 2... Optical waveguide,
3... Comb-shaped electrode, 1o... Semiconductor laser, 12... Waveguide light, 13... Surface acoustic wave converter, 14... Surface acoustic waves, 111-1
14... Light receiving element, 121-124...
・Diffraction light. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 M-1 Number of people

Claims (1)

[Claims] It is composed of an optical waveguide formed on the surface of an elastic substrate, and a surface acoustic wave converter including a comb-shaped electrode formed on the surface of the elastic substrate, and the guided light guided through the optical waveguide and the converter. The guided light is diffracted by interaction with a surface acoustic wave excited by the comb-shaped electrode, and the electrode fingers forming the comb-shaped electrode are partially thinned out to diffract the guided light in a plurality of discontinuous diffraction angle directions. An optical signal processing device characterized by: