JPS58217917A - Optical transmission switch - Google Patents

Abstract

PURPOSE:To enable optical transmission at a bending place by making light beam incidence in two directions at the Bragg angle upon an optical deflecting element fixed in a housing, and connecting optical fibers to positions corresponding to its primary diffracted projection light and zero-order diffracted projection light. CONSTITUTION:The switch consisting of an optical deflecting medium element 5 made of tellurium dioxide, transducer 8, and ultrasonic wave absorber 9 is fixed in the housing 16. When the optical deflecting element is turned on by being applied with an ultrasonic wave, incident light from the optical fiber 14 strikes the optical deflecting element 5 at the Bragg angle theta to obtain the primary diffracted projection light diffracted at an angle 2theta, which is guided to an optical fiber 19 through a concave lens 17 and a reflecting mirror 18. The primary diffracted projection light obtained similarly from incident light from the other optical fiber 15 is guided to an optical fiber 20, thus spreading and separating the two light beams. Once the optical deflecting element 5 is turned off by an ultrasonic wave signal, the light from the optical fiber 14 is sent to the optical fiber 20 and that from the optical fiber 15 is sent to the optical fiber 19.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical transmission switch that performs switching of light in an optical fiber for optical transmission.

Conventionally, in order to switch or switch the optical path of an optical fiber used for optical communication, for example, (1) an electro-optic crystal such as lithium tantalate (LiTaO5), h-lue, or lithium niobate (LiNbO2) and a polarizer are used. However, since they use a deflection optical system, they are inefficient and have many drawbacks from a practical point of view. (2) Mechanically moving mirrors, prisms, etc.
Devices that switch the optical path have also been proposed, but they have the drawback of slow operation time and the impossibility of speeding up the operation time, as well as poor durability because they are mechanically operated.

The present invention is a novel invention that improves the conventional drawbacks as described above, and its purpose is to make it possible to switch the optical paths of two incident lights and to switch the optical path from a low speed range to a high speed range. The purpose of the present invention is to provide a 2×2 optical transmission switch.

Specifically, the response speed of the optical transmission switch of the present invention is as follows:
While the response speed of a conventional switch is about 60 Hz to 10 KHz, the response speed of the switch of the present invention is 0 to 40 KHz because an optical deflection element is used as an acousto-optic medium.
A surprisingly wide response speed of MHz can be obtained arbitrarily.

In addition, optical transmission switches that can obtain this response speed arbitrarily have a switching speed of approximately 100 to
Since it can respond up to 1000 times more, it has the advantage of having a wide range of applications.

In the present invention, light is incident on an optical deflection element, which is an acousto-optic medium fixed in a housing, from two directions at an angle defined as the Bragg angle, either directly or via a main optical fiber, and then the next precipitated light is and 0 linearly with respect to the angle of incidence of light
The method is characterized in that an optical fiber is connected to each position of the next precipitated light, making it possible to transmit light to complicated locations with bends, which is a characteristic of optical fibers, or to locations that require a long length. It is an optical transmission switch.

In the present invention, an optical deflection medium made of an ultrasonic light modulating material such as tellurium dioxide or lead molybdate is used as the optical deflection element.

Fig. 1 shows the switching state of the optical path when light is incident from two directions at an angle defined as the Bragg angle in the present invention. FIG. The ultrasonic wave applied to the optical deflection element (5) is turned on by an electrical signal.
Then, as shown in Fig. 1(a), the incident light (1) from the Bragg angle θ undergoes Bragg diffraction, and the -order diffraction
The output field is 0 output light (3). Then, the incident light (2) from another Bragg angle θ is similarly subjected to Bragg diffraction, and is outputted as -th order precipitated light (4).

On the other hand, if the ultrasonic wave applied to the optical deflection element (5) is turned off by an electric signal, the incident light (1) will not undergo Bragg diffraction, as shown in FIG. (4) and the incident light (2) t-,i
: Output to the o-th next precipitation light (3).

As in the present invention, the optical transmission switch that switches or switches between the -next precipitation light and the O-next direction light can be used for same-line switching, light duplication switching, video switching, optical sensor applications, and the like.

In addition, in the present invention, when light is incident from two directions at an angle defined by the Bragg angle into an optical deflection medium in which an optical deflection element is fixedly provided within a housing, the Bragg-next precipitated light has approximately 85 beams. It is diffracted to some extent and becomes diffracted outgoing light. and the remaining 1
5% h, the afterglow of the 0th order precipitated light is linear to the incident angle.

This is due to the influence of the beam diameter of the incident light and the material of the optical deflection element, and when used as the optical transmission switch of the present invention, there is a risk of switching malfunction depending on the application.

In order to perform a highly reliable switching operation between the 0th order precipitation light and the -th order precipitation light without malfunction,
For example, a transmission light signal received through an optical fiber is received by means such as a photodiode or a photomultiplier tube, and by using auto gain control (ABC) or auto threshold control (ATC), it is It is necessary to set up an optical transmission switch that can stably transmit the difference between the 0th-order precipitated light and the 1st-order precipitated emitted light to the terminal without any problems.

Furthermore, in the present invention, the difference in the emission angle between the 0th-order precipitated light and the 1st-order precipitated light is as small as 1 to 3 degrees. For this reason, the diffracted lights are very close to each other, and in order to accurately separate and receive each beam, it is necessary to connect an optical fiber at a certain distance from the diffraction point.

However, although there is no mechanical problem with this method,
If it were to be made into a system, it would be huge and of little practical value.

In order to efficiently connect each diffracted emitted light to an optical fiber and to make the switch smaller, the light is It is effective to expand the distance between the diffracted and emitted light beams.

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 2 is a diagram showing the configuration of an ultrasonic optical modulator using an optical deflection element, which is an acousto-optic medium, which has been proposed in the past. Note that all drawings are exaggerated for clarity. In FIG. 2, the optical deflection element is composed of an optical deflection medium element (5) made of, for example, tellurium dioxide or lead molybdate, a transducer (8) made of piezoelectric material, and an ultrasonic absorber (9). ) is fixed. The signal processor 02 driving the transducer (8) has an input signal C modulated with approximately 80 to 15
Outputs a high frequency pulse signal d of 0 MHz.

Light 1 enters the housing (G) through the entrance hole (6) and enters the element (5), which is an optical deflection medium, where it undergoes a Bragg rotation with respect to the 0th order diffracted light within the medium that vibrates ultrasonically. A first-order diffracted light is generated at the correct angle, and this -order diffracted light is emitted from the optical deflection medium, becomes an emitted light j, passes through the exit hole (7), and enters an optical path (not shown) in the apparatus. The conventional ultrasonic optical modulator configured in this manner utilizes only -order diffraction light, and is completely different from the 2×2 optical transmission switch of the present invention.

FIG. 6 is an explanatory diagram showing the configuration of an embodiment of the optical transmission switch of the present invention. As explained in Figure 1, the principle of the present invention is to use a medium such as tellurium dioxide or lead molybdate as an optical deflection element, and adhere a piezoelectric material (for example, lithium niobate or zinc oxide) to When a voltage of f is applied, an ultrasonic wave (contraction wave of the medium) with a sonic speed of V and a wavelength of (△-v/f) is generated in the medium.In other words, the medium has a diffractive index with a periodic change in refractive index in the interval. It becomes a grid.

If the lattice spacing equation is much longer than the wavelength of the light or the beam diameter of the incident light, the medium acts as a convex or concave lens for the incident light, and is applied to an optical modulator. As long as the length in one direction is not significantly larger than the wavelength of the light, the medium acts as a diffracting photon for the incident light and can be applied as a light deflector.

Among the phenomena of light diffraction caused by ultrasound, light is incident on the wavefront of the ultrasound at a Bragg angle of C, and is diffracted only in the direction that makes the same angle as the wavefront. At this time, the incident angle is reflected by the wavefront of the ultrasonic wave, and the reflected light (Bragg reflection) can be treated as incident light that is deflected by an angle of 2θ.

If the length of the ultrasonic wave interacting with light in the medium is L, and the refractive index of the medium is n, then the value of the parameter Q defined by is larger than 4π is a necessary condition for optical deflection due to Black diffraction. be. In other words, if L = 1cym, then approximately 80
Light deflection occurs due to ultrasonic waves with a frequency of MHz or higher υ,
The deflection angle Δθ is given by Δf and λ, and varies from 1 to 3°ti.

The configuration of an embodiment of the novel optical transmission switch using the above principle is exactly the same as that in FIG.
) and an ultrasonic absorber (9), and was fixed inside the housing, and optical fibers 04 and Q were installed at the part where light enters and exits the housing (g).

At this time, the optical fiber as the incident light is set so that the light enters the light deflection element (5) from two directions at angles θ corresponding to the respective Black angles.

When the ultrasonic wave applied to the optical deflection element (5) is turned on by an electric signal, the light incident from the optical fiber 04 is diffracted at an angle of 2θ with respect to the Bragg incident angle θ, and primary precipitated incident light is obtained. This emitted light can be connected to an optical fiber by a concave lens and a reflecting mirror. In addition, the light of the optical fiber (IFJ) is incident at an angle θ corresponding to the other Bragg angle, and a primary precipitated light is obtained at an angle of 20, and this output light is also reflected by the concave lens Q71 and the reflection mirror 01. The light transmitted from the optical fiber Q4 is connected to the optical fiber (He
The light transmitted from the optical fiber 0 is received and received by the optical fiber wire, and is expanded and separated by the combined use with an optical system mechanism.

On the other hand, if the ultrasonic waves applied to the optical deflection element (5) are turned off by an electric signal, the light transmitted from the optical fiber A4 will be transferred to the optical fiber (E), and the light transmitted from the optical fiber QF9 will be transferred to the optical fiber (E). It is sent to the OI and becomes an optical transmission switch. Incidentally, such a 2×2 optical transmission switch of this embodiment is a combination of a lens 00 and a lens 00 so that the light from the optical fibers 0 and OQ becomes parallel light in the form of a beam. Further, in order to perform light switching with high precision, the reliability of the switch can be increased by combining a photodiode with a multi-position adjuster incorporating an automatic gain control.

Note that the present invention is not limited to this embodiment, and for example, the light receiving position of the emitted light of the optical fiber and the separation mechanism of the 0th-order diffraction and the first-order precipitated light may be determined by using a plurality of convex mirrors, prisms, etc. A combination, such as a mechanism in which an optical fiber is inserted into the housing and directly adhered to a lens or prism, is also possible and is included in the present invention.

[Brief explanation of the drawing]

Fig. 1 is a drawing showing the switching state of the optical path of the optical transmission switch of the present invention, Fig. 2 is a drawing showing the configuration of an ultrasonic optical modulator using a conventional optical deflection element, and Fig. 3 is a drawing showing the optical path switching state of the optical transmission switch of the present invention. FIG. 2 is an explanatory diagram showing the configuration of an embodiment of a transmission switch. Symbols (1) and (2) in the drawing indicate the optical paths (3) and (
4) is the optical path of the emitted light, (5) i, i: optical deflection medium element, (8) is the tiger juicer, (9) is the ultrasonic absorber, 04) Of)
to H) L optical fiber, 0 to reflection mirror, (2υ(2
2+! 23 indicates a lens. Bottom 7"'(b> Act 2, Segment 3, 2

Claims (3)

[Claims] (1) An optical deflection element, which is an acousto-optic medium, is fixed inside the housing, and light is incident on this optical deflection element from two directions directly or via a trunk optical fiber at an angle corresponding to the Bragg diffraction angle. An optical fiber is connected to each output end of the zero-order precipitated light that is linear with respect to the incident angle of the light and the first-order precipitated light that is caused by Bragg diffraction, and the emitted light is switched or switched. optical transmission switch. (2) Auto gain control 4L< incorporates auto threshold control into the mechanism that switches or switches between the 0th-order precipitation light and the 1st-order precipitation light, and prevents malfunctions caused by the afterglow of the -next light and the 0th-order light. An optical transmission switch according to claim 1, which prevents the problem. (3) An optical system for expanding the interval between the 0th-order precipitation light and the 1st-order precipitation light is installed in the mechanism that switches or switches between the 0th-order precipitation light and the 1st-order precipitation light, and an optical fiber is connected to the output end of each light. Claim 1, which is connected to
Optical transmission switch described in section.