JPS6039849Y2 - optical switch - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a compact and highly stable optical switch that is suitable for optical communication systems.

Recent performance improvements in optical semiconductor devices and optical fibers for communication have been remarkable, and research and development for the practical application of optical communication systems is progressing in various places.

One of the optical devices essential to optical communication systems is an optical switch.

For example, when performing unidirectional communication using two optical fibers, if one optical fiber becomes disconnected or otherwise unable to communicate, the signal generator will transfer the transmission signal to the other optical fiber. An optical switch is used to switch and transmit the signals.

Conventionally, a reflecting mirror that can be inserted into and removed from an optical transmission system has been used as this type of optical switch.

In addition, as laboratory-grade devices, optical deflectors using electro-optic effects and optical switches using acousto-optic effects have been proposed.

However, the above-mentioned various optical switching devices lack mechanical stability, are large in size, and have high manufacturing costs.

An object of the present invention is to eliminate the above-mentioned drawbacks and provide an inexpensive optical switching device that is small, resistant to external disturbances, and suitable for optical fiber communication systems.

According to the present invention, a light-converging transparent body whose refractive index in a cross section perpendicular to the central axis gradually decreases as it moves away from the central axis is used to connect a plane (first surface) including the central axis and a plane perpendicular to the central axis. Prepare two transparent bodies cut on two parallel planes (second surface and third surface), and make sure that the first surfaces of these two transparent bodies (first transparent body and second transparent body) are parallel to each other. a composite transparent body arranged such that they face each other in parallel and have their central axes within the same plane perpendicular to the first surface, and a first transparent body and a second transparent body that constitute this composite transparent body. An optical switching device is obtained that includes a gap variable means capable of changing the gap and a polarization selection element disposed close to the second surface of the first transparent body.

Next, the present invention will be explained using the drawings.

FIG. 1 shows a first embodiment of the present invention, and 1 and 2 indicate a light-converging transparent body whose curvature in a cross section perpendicular to the central axis decreases as the distance from the central axis increases. A pair of transparent bodies cut along a plane constitute a composite transparent body arranged so that the cut surfaces face each other.

3 is a mechanical variable means for adjusting the size of the gap between opposing surfaces of the composite transparent bodies 1 and 2; 4 is a prism made of a birefringent substance.

Further, 6 is incident light, and 7 and 8 are output lights.

In this configuration, by adjusting the mechanical variable means, the transparent body 1
Let us first consider the case where the gap between the transparent body 1 and the transparent body 1 is made sufficiently large so that the incident light 6 is totally reflected inside the transparent body 1 and travels.

As is widely known, when light traveling from a material with a large curvature index toward a material with a small curvature index is totally reflected, the light undergoes a phase change.

The phase difference δ between the electric field component of light parallel to the incident plane and the electric field component of light perpendicular to the incident plane is expressed by the following equation.

a.

a = cosθ5ma...(1)2
5in2θ where θ is the angle of incidence of light incident on the reflective surface (see Figure 1)
, n''r12/nl.

However, nl and n2 indicate the curvature index of the transparent body and external medium in the vicinity of the reflective surface, respectively.

Now, by setting n1 = 1.51, n2 = 1.0 (air), and θ = 54°37', δ = 7 is obtained.

That is, by totally reflecting the incident light 6 four times inside the transparent body 1, the phase difference π radial between the electric field component parallel to the plane of incidence and the electric field component perpendicular to the incident plane of the incident light 6 is obtained and the beam is emitted, so the deflection plane is 90
°It becomes a rotated linear polarization and enters the prism and the outgoing light 7
becomes.

On the other hand, if the mechanical variable means 3 makes the gap between the transparent bodies 1 and 2 sufficiently small so that the incident light 6 travels without being totally reflected (the optical path indicated by the broken line), the difference between the two military disciplines of the incident light 6 is The light is emitted as emitted light 8 without undergoing any phase change.

Here, since the incident light 6 is linearly polarized light whose polarization plane makes an angle of 45° to the above-mentioned plane of incidence, the phase difference between the electric field component parallel to the plane of incidence and the electric field component perpendicular to the plane of incidence of the incident light 6 is π radian. Alternatively, as the light is converted into O radians, the light emitted from the birefringent prism 4 is switched to linearly polarized light that is orthogonal to each other.

FIG. 2 shows a second embodiment of the invention.

1 and 2 are the aforementioned transparent bodies, 3 is a mechanical variable means, 5 is a birefringent plate made of a birefringent material whose principal axis is not perpendicular to the incident end surface, 6 is incident light, and 7 and 8 are output lights. be.

As in the case of the first embodiment, by adjusting the mechanical variable means 3, the incident light 6 passes through the transparent bodies 1 and 2 or the transparent body 1, so that the phase difference between the electric field component parallel to the plane of incidence and the electric field component perpendicular to the plane of incidence is They receive π radians or O radians and are switched to linearly polarized light that is orthogonal to each other.

In the above embodiment, the dimensions of the gap between the transparent bodies 1 and 2 were changed by a mechanical method, but an electro-optic material whose refractive index changes by an electric field is provided in the gap to change the effective dimension by electrical means. Of course, you can let them do so.

Further, in the above embodiment, a configuration was shown in which the light undergoes a phase difference of 17 jian with one total reflection, but the present invention is not limited to this.
It is obvious that total reflection can be performed an arbitrary number of times to form a phase difference of a total of π radians.

Finally, the feature of the present invention is that, as is clear from equation (1), even if the temperature of the transparent body 1 changes, the phase change due to the change in refractive index is extremely small, so the optical switching device is stable against external disturbances. is obtained.

Since the transparent bodies 1 and 2 are made of light-converging transparent bodies, the light beams propagating inside them proceed without divergence, and in principle a lossless optical switch can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a first embodiment of the present invention, Fig. 2 is a sectional view showing a second embodiment of the invention, 1 and 2 are transparent bodies, 3 is a mechanical variable means, and 4 is a sectional view showing a second embodiment of the present invention. Prism, 5 is a birefringent plate,
6 is the incident light, and 7 and 8 are the outgoing lights.

Claims (1)

[Scope of utility model registration request] It has a refractive index distribution in which the refractive index in a cross section perpendicular to the central axis gradually decreases as it moves away from the central axis, and a first surface consisting of a plane including the central axis and a first surface perpendicular to the central axis and parallel to each other. a first surface having second and third surfaces, respectively;
and a composite transparent body in which a second light-focusing transparent body is arranged such that their respective first surfaces are parallel to each other and face each other;
the first surface of the first transparent body and the first surface of the second transparent body
and a polarization selection element disposed in close proximity to the second surface of the first transparent body, the polarization selecting element for changing the gap between the first transparent body and the third surface of the first transparent body. When the gap is small, the light travels through the first transparent body and the second transparent body and exits from the second surface of the first transparent body, and when the gap is large, the light travels through the first transparent body and the second transparent body and exits from the second surface of the first transparent body. The incident light propagates by repeating total reflection on the first surface of the first transparent body, and the electric field component parallel to the incident plane and the electric field component perpendicular to the incident plane undergo a phase change during this total reflection, resulting in a polarization plane. An optical switching device characterized in that the light changes and the light is emitted from the second surface of the first transparent body.