JPS629326A - Optical switch - Google Patents

Abstract

PURPOSE:To reduce crosstalk sufficiently by operating >=2 ultrasonic oscillators provided to an acoustooptic element alternately and outputting only generated diffracted light. CONSTITUTION:Parallel luminous flux from a rod lens 14 is diffracted by a diffraction grating formed by an ultrasonic oscillator 16 in the acoustooptic element 15 and propagates along an optical path 19 to enter an optical fiber 22 through a rod lens 21. Then, when the oscillator 16 is stopped and an oscillator 17 is put in operation, the diffracted light travels along an optical path 20 to enter an optical fiber 24. Therefore, the optical paths of the diffracted light are changed through the alternate operation of the oscillators and when there is not the diffracted light, no output is sent out, so the quenching ratio increases and crosstalk is made small.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to optical switches used in optical fiber communications.

BACKGROUND OF THE INVENTION Conventionally, this type of optical switch has had a configuration as shown in FIG. In Figure 4, 1.6.8 is an optical fiber, 2,
5.7 is a rod lens, ``C'' is an acousto-optic element, 4 is an ultrasonic oscillator, 9 is transmitted light, and 10 is diffracted light.

First, the light switching effect of the acousto-optic element will be explained. In Fig. 6, 3 is an acousto-optic element;
9 is an ultrasonic oscillator, 9 is transmitted light, 10 is diffracted light, 11 is incident light, and 12 is a diffraction grating.

When an ultrasonic wave is generated by the ultrasonic oscillator 4 into the acousto-optic element 3, parts where the refractive index becomes large and parts where the refractive index becomes small alternate in the acousto-optic element 3 at intervals of the wavelength of the ultrasonic wave in the direction of propagation of the ultrasonic wave. This forms the diffraction grating 12. The incident light 11 is directed at a Bragg angle with respect to the diffraction grating 12.
When the light is incident, the light is diffracted by the diffraction grating 11 and the diffracted light 10
becomes.

On the other hand, when the generation of ultrasonic waves by the ultrasonic oscillator 4 into the acousto-optic element 3 is stopped, the diffraction grating 12 disappears, so the incident light 11 becomes transmitted light 9. In this way, the ultrasonic oscillator 4
When the ultrasonic transducer 4 is in operation, the light emitted from the optical fiber 1 is converted into parallel light by the rod lens 2, and the light is converted into parallel light by the acousto-optic element 3. Zero incident light incident at the Bragg angle to the diffraction grating (not shown) is diffracted by the diffraction grating and becomes diffracted light 1
0, the light is focused by the rod lens 7, and enters the optical fiber 8. On the other hand, when the ultrasonic oscillator 4 stops, the incident light becomes transmitted light 9 without being diffracted, and the rod lens 5
The light is collected by the beam and enters the optical fiber 6.

Problems to be Solved by the Invention In such a conventional configuration, since the diffraction efficiency of the acousto-optic element is 99% at maximum, the first beam is always transmitted light. Therefore, the minimum crosstalk is 20dB (1/10o
), there was a problem of large crosstalk.

The present invention is intended to solve these problems, and aims to sufficiently reduce crosstalk.

Means for Solving the Problem In order to solve this problem, the present invention provides one acousto-optic element with two or more ultrasonic oscillators, and changes the direction of diffraction of light by operating each one alternately. It is designed to switch the light using the

Function: With this configuration, only the diffracted light is always received without transmitting the transmitted light, so the stray light when the diffracted light is not being received is extremely small, so crosstalk can be sufficiently reduced.

Embodiment FIG. 1 is a block diagram of an optical switch according to a first embodiment of the present invention. In Fig. 1, 13, 22, 24 are optical fibers, 14, 21, 23 are rod lenses, 16 are acousto-optic elements, 16, 17 are ultrasonic oscillators, 18 are optical paths, and 19 are optical fibers.
．． 20 is an optical path of diffracted light.

In the initial state, the ultrasonic oscillator 16 and the acousto-optic element 15
Assume that a diffraction grating is created inside.

The light emitted from the optical fiber 15 is converted into a parallel light beam by the rod lens 14, and passes through the acousto-optic element 16 on an optical path 18.
Proceed along. This light is diffracted by a diffraction grating generated by the ultrasonic oscillator 16, travels along an optical path 19, and then travels through a rod lens 21 and enters an optical fiber 22.

Next, when the ultrasonic oscillator 16 is stopped and the ultrasonic oscillator 17 is operated, the light traveling along the optical path 18 is diffracted by the diffraction grating generated by the ultrasonic oscillator 17, and travels along the optical path 20, passing through the rod. After being focused by the lens 23, the optical fiber 2
4. Therefore, by alternately operating the ultrasonic oscillators 16 and 17, the optical path is changed.

FIG. 2 is a block diagram of an optical switch according to a second embodiment of the present invention. In FIG. 2, the ultrasonic oscillators 16 and 17 are different from the first embodiment of the present invention in that they are arranged side by side on one side of the acousto-optic element 15, but their operation is the same as that of the first embodiment of the present invention. It is.

FIG. 3 is a block diagram of an optical switch according to a third embodiment of the present invention. The third embodiment is a waveguide version of the second embodiment. In fig.

26 is a waveguide thin film, 26 is a waveguide substrate, 27.28 is an electrode for ultrasonic oscillation, 29.30 is a diffraction grating generated by ultrasonic waves, 31 is an optical path, and 32.33 is an optical path for diffracted light. .

The light incident on the optical waveguide 26 travels along the optical path 31, and when only the electrode 27 is in operation, it is diffracted by the diffraction grating 29 and travels along the optical path 33. On the other hand, when only the electrode 28 is operating, the light is diffracted by the diffraction grating 30 and travels along the optical path 33.

Effects of the Invention As described above, according to the present invention, two or more ultrasonic oscillators are provided in an acousto-optic element, and each is operated alternately to generate a diffraction grating to receive diffracted light as output light. Additionally, when there is no diffracted light, no light is output, so the extinction ratio is high, and therefore the effect of reducing crosstalk can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an optical switch according to a first embodiment of the present invention, FIG. 2 is a block diagram of an original switch according to a second embodiment of the present invention, and FIG. 3 is a block diagram of a third embodiment of the present invention. Fig. 4 is a block diagram showing the conventional optical switch ÷.
FIG. 5 is an explanatory diagram illustrating the switching phenomenon of light by diffracting light due to the acousto-optic effect. 13, 22, 24... optical fiber, 15.
... Acousto-optic element, 16.17 ... Ultrasonic oscillator, 18 ... Optical path, 19.20 ...
...Optical path of diffracted light. Name of agent: Patent attorney Toshio Nakao and 1 other person
l Figure 1.3, 22
．． 24--1st Bua 18゛f8--9th Road 49.20-11th 141st 9E-Ll Fig. 2

Claims (4)

[Claims] (1) Two or more ultrasonic transducers are provided in one acousto-optic element, the ultrasonic transducers are operated alternately to generate a diffraction grating, and only diffracted light is received as output light. light switch. (2) The optical switch according to claim 1, wherein one or more ultrasonic transducers are provided on two or more different faces of the polygonal acousto-optic element. (3) The optical switch according to claim 1, characterized in that two or more ultrasonic transducers are provided on one surface of the polygonal acousto-optic element. (4) The optical switch according to claim 1, which uses an optical waveguide having an acousto-optic effect.