JPH054646B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical/acoustic signal processing device in which a plurality of surface acoustic wave electrodes and a plane lens are provided on a plane optical waveguide.

[Conventional technology]

Optical/acoustic signal processing devices that use the interaction of surface acoustic waves and light on optical waveguides (plug diffraction) are capable of high-speed processing, small size, and light weight, so they have been realized as spectrum analyzers and optical correlators, and are being put into practical use. transformation is actively taking place.

Optical correlators are used as high-speed correlators that instantly correlate two signals, and are usually used to correlate signals such as radar signals.
It is applied to deciphering unknown RF signals. Conventionally,
This type of device was developed by Professor Tsai of the University of California in the magazine ``I.I.I.
IEEE Transaction on Circuit Systems
He wrote an article on p. 1072 of the December 1979 issue of ``Guided Wave Acoustoscopic Plug Modulators for Wideband Integrated Optics, Communications and Signal Processing''.
Bragg Modulation for Wide−Band
Integrated Optics Communications and
Signal Processing).

FIG. 2 is a plan view of an optical correlator called a spatial integration type shown in this paper. In the figure, 1 is a ferroelectric material such as lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), silicon (Si),
The substrate is made of a semiconductor such as gallium arsenide (GaAs). On this substrate 1, an optical waveguide layer 2 corresponding to each substrate is formed, for example, a Ti diffused optical waveguide layer in the case of a LiNbO ₃ substrate, and as shown in the figure. Plane lenses 4 and 5 and surface acoustic wave electrodes 6 and 9 are provided. As the plane lenses 4 and 5, geo-digital lenses with depressions formed on the substrate 1 are usually used, but chive grating lenses with grooves or metal strips forming a non-periodic grating on the substrate can also be used. Each of these optical elements is arranged to perform the following functions. That is, light emitted from a light source 3 (usually composed of a semiconductor laser, LED, etc.) connected to the end surface of the substrate 1 propagates through the waveguide 2 and becomes parallel light by the plane lens 4. This parallel light is first deflected by the surface acoustic wave 12 emitted from the electrode 6, then deflected again by the surface acoustic wave 15 emitted from the electrode 9, and then condensed by the plane lens 5 and detected by the photodetector 18. Light is received and converted into an electrical signal. In this case, surface acoustic waves 12,
Unnecessary lights 21 and 22 that are not deflected by the photodetector 15 are spatially separated from the photodetector 18 and condensed, so that they can be removed. When an electric signal S ₁ (t) is applied to the electrode 6 of such an optical correlator and an electric signal S ₂ (t) is applied to the electrode 9, the photodetector 18 detects a correlation signal u(τ) of the following equation. Ru.

u(τ)=∫ ^T0 ₀ s ₁ (t)s ₂ (τ−t) ^dtHere , T ₀ is a constant given by T ₀ = W/V, where the optical beam width W and the surface acoustic wave velocity V are be.

[Problem that the invention seeks to solve]

With such a conventional optical correlator, it is possible to quickly correlate the electric signals S ₁ (t) and S ₂ (t) applied to each surface acoustic wave electrode, but in this case, the integration time has an upper limit determined by the propagation time T ₀ of the surface acoustic wave across the optical beam width. Normally, in a correlator, the larger the constant T ₀ , the higher the accuracy of the correlation signal.
Although resolution improves, conventional optical correlators
Considering the manufacturing limits of plane optical lenses 4 and 5, the constant
T ₀ is only possible for about 2 μs at most.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical/acoustic signal processing device that can effectively extend the integration time when correlating two electrical signals and improve the accuracy and resolution of the correlation signal.

[Means for solving problems]

The configuration of the optical/acoustic signal processing device of the present invention includes a first optical means that converts light emitted from a light source into parallel light, and a first optical means that includes two or more optical deflection elements that deflect the parallel light. a light deflection means; a second light deflection means comprising two or more light deflection elements that further polarizes the output light of the first light deflection means; and a second light deflection means for condensing the output light of the second light deflection means. The first and second
It is characterized in that the positions of the optical deflection elements constituting the optical deflection means are shifted from each other by a length corresponding to the width of each of the parallel lights.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the optical/acoustic signal processing device of the present invention. In this embodiment, an optical waveguide 2 corresponding to each substrate 1 is formed on a substrate 1 made of ferroelectric material, semiconductor, glass, etc. For example, if the substrate is made of lithium niobate (LiNbO ₃ ), Ti
Form a diffused optical waveguide. Next, this optical waveguide 2
A first optical deflection path consists of two plane lenses 4, 5 and three surface acoustic wave electrodes 6, 7, 8 on the top, and a second optical path consists of three surface acoustic wave electrodes 9, 10, 11. Provide a deflection path.

The arrangement of these optical elements is as follows. That is, light emitted from a light source 3 such as a semiconductor laser propagates through a waveguide 2, and is further converted into parallel light by a plane lens 4. This parallel light is deflected by the surface acoustic waves 12, 13, 14 emitted from the surface acoustic wave electrodes 6, 7, 8, and further by the surface acoustic waves 15, 16 emitted from the surface acoustic wave electrodes 9, 10, 11. , 17, is focused by a plane lens 5, and projected onto a plurality of photodetectors 18, 19, and 20.

In addition, each surface acoustic wave generation electrode 6, 7, 8,
9, 10, and 11 are arranged at intervals of a distance W along the surface acoustic wave propagation direction. Note that the distance W indicates the width of the light beam converted into parallel light by the plane lens 4.

When electrode signals S ₁ (t) are simultaneously applied to electrodes 6, 7, and 8 in this configuration, the signal S ₁ (t) is always separated by time T ₀ (W/V) in the light beam. Multiple signal parts can exist. That is, at a certain moment, the first time T ₀ minutes of S ₁ (t) is caused by the surface acoustic wave excited by the electrode 6, the next time T ₀ minutes is caused by the electrode 7, and the next time T ₀ minutes is caused by the surface acoustic wave excited by the electrode 8. The surface acoustic waves excited by the light beam are present in the light beam. Therefore, 3T ₀ time signals of the signal S ₁ (t) can be simultaneously present in the light beam. Similarly, electric signals are sent to electrodes 9, 10, and 11.
This also occurs when S ₂ (t) is applied simultaneously.

Furthermore, in this embodiment, it is necessary that the light beam deflected by the surface acoustic wave 12 be deflected only by the surface acoustic wave 15 and not be deflected by other surface acoustic waves. Similarly, surface acoustic wave 1
The light beam deflected by the surface acoustic wave 14 must be deflected only by the surface acoustic wave 17.

Therefore, as shown in FIG. 1, when input signals are modulated at different frequencies ₁ , ₂ , ₃ , ₄ , ₅ , and ₆ and applied to the surface acoustic wave electrodes 6-8, 9-11, the elastic Just as the light beam deflected by the surface acoustic wave 12 is deflected only by the surface acoustic wave 15, the light beam deflected by the surface acoustic wave 13 is deflected by the surface acoustic wave 16 only, and the light beam deflected by the surface acoustic wave 14. It becomes possible to arrange the beam so that it is deflected only by the surface acoustic wave 17.

This can be achieved because the deflection angles (plug angles) of the light beams due to each surface acoustic wave are different. Detection of optical signals is performed using surface acoustic waves 15, 16, 1
The light beams deflected by 7 are condensed by a plane lens 5 and delivered to a photodetector 10. However, since the optical deflection angles of each light beam are different, they are spatially separated at the focal plane and are detected by each photodetector. vessel 20,1
Detected at 9,18.

The electrical signals detected by these detectors 18, 19, and 20 are later added together and taken out from the output terminal 24 as a single electrical signal output.

Although this embodiment shows an example in which each of the focused beams is received by each photodetector, it may be received by a single detector with a large light-receiving area. However, in this case, it is necessary to particularly select a high-speed and large-area photodetector. In addition, isotropic plug diffraction is considered as the plug diffraction condition because of ease of design, but if anisotropic plug diffraction is used, the angle that satisfies the plug condition is not allowed as much as isotropic plug diffraction. Therefore, by designing the surface acoustic wave electrodes 6 to 11 under anisotropic plug conditions, unnecessary mutual deflection of the light beams will hardly occur.

〔Effect of the invention〕

As explained above, according to the present invention, by increasing the number of electrodes of the optical correlator and shifting each electrode by the width of the parallel light beam, the input electric signal S ₁
(t), S ₂ (t) is N times the time T ₀ determined by the light beam width W and surface acoustic wave velocity V within the light beam (N is the number of surface acoustic wave electrodes, in the example, N = 3) exists for a period of time, and the correlation between them can be taken. That is, among the signals S ₁ (t) and S ₂ (t) existing in the light beam, the signals for the first time T ₀ time, the signals for the next time T ₀ time, and the signals for the next time T ₀ time Since each surface acoustic wave electrode is arranged so that the product of the signals can be calculated for the time period, the correlation of the signals S ₁ (t) and S ₂ (t) for N·T ₀ hours can be determined. Conventional optical correlators could only take T ₀ time, but with the present invention, correlation can be taken for N times longer than before, which means that the integration time of the optical correlator can be extremely long, and the accuracy and resolution of the correlation signal can be improved. It is possible to measure the improvement of

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of the present invention, and FIG. 2 is a perspective view of an example of an optical correlator as a conventional optical/acoustic signal processing device. 1...Substrate, 2...Optical waveguide, 3...Light source,
4, 5...Plane lens, 6, 7, 8, 9, 10,
11...Surface acoustic wave electrode, 12, 13, 14, 1
5, 16, 17...Surface acoustic wave, 18, 19, 2
0...Photodetector, 21, 22, 23...Unnecessary light.

Claims (1)

[Claims] 1. A first optical means for converting light emitted from a light source into parallel light, a first light deflection means comprising two or more light deflection elements for deflecting the parallel light, and this first light deflection means. further deflecting the output of 2
a second optical deflection means composed of one or more optical deflection elements, a second optical means for condensing the output light of the second optical deflection means, and an electric light condensed by the second optical means. and a photodetecting means consisting of a single or a plurality of photodetecting elements for converting into a signal, and the position of the optical deflection element constituting the first and second optical deflection means corresponds to the width of each of the parallel lights. An optical/acoustic signal processing device characterized by being offset from each other in length.