JPS5934890Y2 - light switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical switch used in optical communications, and for example, to an optical switch that switches an optical waveguide such as an optical fiber between two directions.

Generally, in optical communications, an optical switch is used to switch optical waveguides such as optical fibers without performing optical/electrical conversion.

One type of conventional optical switch uses mechanical displacement.

For example, there are devices that couple a first optical fiber to a second or third optical fiber by moving it using the force of an electromagnet, but these have problems such as slow switching speed and large size. There is.

Furthermore, there are other conventional optical switches that switch the optical path by changing the refractive index of an electro-optic crystal by applying an applied voltage, but this has the problem of large loss even when using light of a single wavelength.

The purpose of this invention is to control the on/off voltage applied to the piezoelectric element based on the idea that a dielectric plate (simply referred to as a piezoelectric element) having a piezoelectric effect is coupled to a Fabry-Perot interferometer to form an optical switch. By switching the light transmission conditions and reflection conditions, the switching speed is increased, the shape is made smaller, and the loss is minimized by using light of a single wavelength, thereby solving the problems of the conventional type described above. The point is to solve the problem.

The present invention will be explained below with reference to the drawings.

FIG. 1 is a diagram illustrating transmission conditions and reflection conditions of a Fabry-Perot interferometer using a piezoelectric element.

In a typical Fabry-Perot interferometer, the bottom of the chamber is formed by two parallel glass plates having semi-reflective surfaces, and the interference conditions are controlled by adjusting the distance between them using a micrometer screw.

In the present invention, a piezoelectric element is used instead of the two glass plates, and the interference conditions are controlled by applying an electric field to the piezoelectric element and changing the thickness of the piezoelectric element.

In FIG. 1, a piezoelectric element 1 with a refractive index n and a thickness d has the following characteristics:
When an incident light beam (■) with a wavelength λ is incident at an incident angle i, it enters the dielectric plate 1 at a refraction angle θ.

In this case, reflected lights R,, R2, . T2?・
...is obtained.

By appropriately setting the thickness d of the piezoelectric element 1, it is possible to eliminate reflected light and only transmit light, or eliminate transmitted light and only transmit reflected light.

As is well known, such transmission conditions and reflection conditions are as follows.
It can be expressed by the following formula.

Transmission condition 2nd cosθ−□λ (
1) Reflection condition 2nbcosθ=(2m+1)λ,/
2 (2) (m=0, 1, 2...) Here, formula (1) is satisfied when no electric field is applied to piezoelectric element 1, and on the other hand, Apply an electric field of the same magnitude and change the thickness d to d+△d (2)
If the formula is satisfied, the thickness change Δd can be expressed as follows.

For example, λ=1.3 μm, θ=45°. When n"1.5, Δd is 0.3 pm.

By turning on and off the electric field that generates such a thickness change Δd, only transmitted light or reflected light can be generated.

FIG. 2 is a layout diagram showing an optical switch as an embodiment of the present invention.

In FIG. 2, transparent electrodes 2 and 3 are bonded to a piezoelectric element 1.

A voltage is applied between the electrodes 2 and 3 that satisfies the above-mentioned transmission and reflection conditions.

For example, assume that the transmission condition of equation (1) is satisfied when no voltage is applied, and the reflection condition of equation (2) is satisfied when a voltage is applied.

First, when no voltage is applied, the incident light (2) from the optical waveguide, for example, the optical fiber 4, enters the piezoelectric element 1 via the condensing lens 7, and the multiple transmitted light T passes through the condensing lens 8. The light enters the optical fiber 5 through the optical fiber.

On the other hand, when a voltage is applied, the incident light I from the optical fiber 4 reaches the piezoelectric element 1 via the condenser lens 7, but the light R that has been multiple-reflected on both sides of the piezoelectric element 1 passes through the condenser lens 9. The light enters the optical fiber 6 through the optical fiber.

In this way, by turning on and off the voltages applied to the electrodes 2 and 3, the optical path from the optical fiber 4 to one of the optical fibers 5.6 is changed from the optical path from the optical fiber 4 to the other optical fiber 5.6. can be switched to.

FIG. 3 is a layout diagram showing an optical switch as an embodiment of the present invention, and unlike the case in FIG. 2, optical fibers 4,
The case where 5 and 6 are arranged in parallel is shown.

Even in this case, by providing one large condensing lens 10 for the optical fibers 4 and 5, the piezoelectric element 1
It is possible to make light obliquely incident on the .

In Figures 2 and 3, the electrodes 2 and 3 are provided so that the direction in which the electric field is applied and the direction in which the thickness changes coincide, but the direction in which the electric field is applied is determined by the dielectric (piezoelectric element) If the direction of maximum thickness change is different from
It is preferable to provide the electrodes 2 and 3 in that direction.

Alternatively, for example, the electrode 2.3 may be an opaque electrode that does not block the optical path.

As explained above, according to the present invention, the optical path is switched by on/off control of the applied voltage, so the switching speed can be increased, and since there are few mechanical structures, the size can be made smaller. In addition, by using light of a single wavelength, the selection characteristics can be improved, so the loss can be reduced, which is useful for solving the problems with the conventional type described last week.

[Brief explanation of the drawing]

Figure 1 is a diagram explaining the transmission conditions and reflection conditions of a Fabry-Perot interferometer using a piezoelectric element, Figures 2 and 3
The figure is a layout diagram showing an optical switch on the family side of the present invention. 1... Dielectric plate (piezoelectric element), 2, 3...
...Electrode, 4°5.6... Optical waveguide (optical fiber), 7,8,9°10, 11... Condensing lens.

Claims (1)

[Scope of utility model registration request] 1. a Fabry-Perot interferometer, the bottom of which is a light-transmissive piezoelectric element having parallel first and second surfaces and an electrode that applies an electric field to the piezoelectric element;
a manual optical waveguide and a first output optical waveguide located on the surface side of the mold element, and a second output optical waveguide located on the second surface side of the mold element, and the voltage applied to the electrode is turned on.・
A single-wavelength optical switch characterized in that an optical path from the manual optical waveguide to the first output optical waveguide and an optical path from the manual optical waveguide to the second output optical waveguide are switched when turned off. . 2. The optical switch according to claim 1, wherein the optical waveguide is an optical fiber. 3. The optical switch according to claim 1, in which the electrodes are provided so that the direction in which the electric field is applied and the direction in which the thickness change of the piezoelectric element is greatest coincides with each other.