JPS60107617A - Optical modulator - Google Patents

Abstract

PURPOSE:To realize an optional frequency shifter by using an acoustooptic medium provided with transducers consisting of two channels independent of each other and introducing an output light to an optical fiber by a lens to obtain one optical beam. CONSTITUTION:An acoustooptic medium 1 is provided with transducers 2a and 2b having electrodes of two channels (CH) independent of each other. When electrical signals whose frequencies and amplitudes are set are inputted to these two CHs from high frequency signal sources 3a and 3b, they go as ultrasonic signals in the medium 1. At this time, diffracted lights 6a and 6b are generated from a laser light 6 which is made incident at a certain angle of incidence. This light is introduced to an optical fiber 5a by a lens 4a to obtain an optical output 7a. When the frequency of the input light is denoted as F0 and driving frequencies of two CHs are denoted as fa and fb, frequencies of diffracted lights 6a and 6b are F0+fa and F0+fb by the Doppler effect. These lights interfere when going in the optical fiber 5a, and a beat light is obtained as the optical output 7a, and the diffracted light and non-diffracted light can be separated from each other, and the device is made small-sized and low-cost.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical modulator as a so-called frequency amplifier in which the frequency of light changes to 771.degree. due to the Doppler effect of ultrasound in the diffraction phenomenon caused by ultrasound.

Conventional Structure and Problems Conventional optical modulators as frequency 7 filters using acousto-optic light modulators have used one, one channel, or two one-channel devices. However, due to the operating principle of the acousto-optic light modulator, it is not possible to achieve a drive frequency of less than a few M14 when using a single acousto-optic light modulator. can't get it. Unfortunately, if two units are used, the entire system becomes mechanically large, which is extremely disadvantageous in terms of downsizing and cost reduction.

OBJECTS OF THE INVENTION The present invention eliminates these conventional drawbacks, and aims to provide an optical modulator that can be made smaller and lower in cost.

Structure of the Invention In order to achieve this object, an acousto-optic medium equipped with a tranosunter consisting of two mutually independent channels is used, and the output light is introduced into an optical fiber by a lens to form one optical beam. It's something you get.

With this configuration, it is possible to obtain any frequency/ft and degree of modulation by arbitrarily setting the driving frequency θU number of the acousto-optic medium and the amplitude of the electric power (C>5). can direct the optical output in any direction or medium.

Description of examples An embodiment of the present invention will be described below with reference to the drawings.

In the figure, a toe/stripe user 2a consisting of a piezoelectric vibrator having two independent channels of electrodes on an acousto-optic medium 1
, 2b are provided to constitute an acousto-optic light modulation element. Each of these two channels receives a high frequency electric signal source 3.
When an electric signal with a set frequency and amplitude is inputted from a and 3b, it becomes an ultrasonic signal and propagates in the acousto-optic medium 1. At this time, the light (laser light) 6 that is incident at a constant angle of incidence is diffracted by each channel, producing diffracted lights 6a and 6b. This light is introduced into the optical fiber 5a that passes through the lens 4a, and the cuff a is obtained. Here, the frequency of the incident light is fa and the driving frequency of the FO92 channel is fa and f, respectively.
b, the frequencies of the diffracted lights ea and eb are Fo+fa and Fo+f due to the Doppler effect of the ultrasound, respectively.
It becomes b. This light interferes as it travels through the optical fiber 6a, and beat light with frequencies lJ'a and fbl is obtained at the first cuff a.

In addition, a part of the diffracted light 6a is re-diffracted within the acousto-optic medium 1 to obtain re-diffracted light 6C of frequency Fo+fa-fb, so this re-diffracted light 6C and the undiffracted light (transmitted light) 6d are 4b into the optical fiber 5b, the first cuff b of the frequency a-fbl is obtained in the same manner as described above.

Effects of the Invention As described above, according to the optical modulator of the present invention, an arbitrary frequency shifter can be realized simply by setting electrical signals.

Furthermore, separation of diffracted light and undiffracted light in an acousto-optic medium is possible with a distance of several tens of millimeters, and the entire system can be housed in one case, making it compact, low cost, and extremely easy to handle. .

[Brief explanation of drawings]

The drawing is a configuration diagram showing an embodiment of the optical modulator of the present invention. 1... Acousto-optic medium, 2a, 2b... River transducer, 3a, 3b... High frequency electric signal source, 4a
. 4b・Lens, 5a, 5b---Optical fiber, 6a. 6b... Diffracted light, 6c... Re-diffracted light, 6d
・・River・Non-diffracted light, 6・・・・Incoming light, 7a, 7b
...Light output. Name of agent: Patent attorney Toshio Nakao and one other person

Claims (1)

[Claims] The first two are independent of each other. The diffracted light by the first channel and the diffracted light by the second channel of the acousto-optic medium having the transducer comprising the second channel are introduced into the first optical fiber by the first lens, and the diffracted light by the second channel is introduced into the first optical fiber by the first lens. An optical modulator in which light diffracted by a channel is re-diffracted by a second channel and undiffracted light is introduced into a second optical fiber by a second lens.