JPH03269408A - Optical switch - Google Patents

Abstract

PURPOSE:To realize an optical switch which allows easy and exact optical axis alignment by using a specific flexuous displacement piezoelectric actuator. CONSTITUTION:This optical switch is disposed with two pieces of output side optical fibers 2-1, 2-2 and one piece of an input side optical fiber 1 to face each other and changes over optical paths by moving the light from the input side optical fiber 1. The input side optical fiber 1 is mounted on the side of the flexuous displacement piezoelectric actuator 10 having a polarization inversion layer where the actuator is flexuously displaced. The input side optical fiber 1 is changed over from the output side optical fiber 2-1 to 2-2 to which the input side optical fiber is opposed by the flexuous displacement of the actuator 10 when a DC voltage is instantaneously impressed from a voltage source 9 to the piezoelectric actuator 10. The piezoelectric actuator 10 returns to its home position and the input side optical fiber 1 faces again the output side optical fiber 2-1 when the DC voltage is removed. The changing over without hysteresis is executed in this way.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to an optical switch in which optical path switching for optical transmission is performed without hysteresis, and provides an optical switch that can easily and accurately align optical axes by using a specific bending displacement piezoelectric actuator. In an optical switch that is composed of two output side optical fibers and one input side optical fiber facing each other, and switches the optical path by moving light from the input side optical fiber, the input side optical fiber is attached to the bending displacement side of a bending displacement piezoelectric actuator having a polarization inversion layer.

[Industrial application field]

The present invention relates to an optical switch that performs optical path switching for optical transmission without hysteresis.

Various methods for switching optical paths in optical transmission lines using optical fibers have been studied. Research has been published on optical switches using prisms and optical switches using ceramics, but they have many problems such as being expensive and having large hysteresis. It was desired to develop a low-cost optical switch without hysteresis.

[Conventional technology]

Technologies such as optical transmission using optical LAN have progressed. Optical switches for switching optical transmission lines require high precision because they use minute optical fibers. Examples of optical switches are as follows.

The first method uses a prism and is shown in FIG. Fifth
In the figure, 1 is an input optical fiber, 2-2 and 2-2 are two output optical fibers, and 3 is a prism. The light that enters the optical fiber l is connected to the prism 3 and the optical fiber 1.2-
1 is in contact, it is reflected twice inside the prism 3 and output from the optical fiber 2-1. When the prism 3 is moved or rotated to remove contact with the optical fiber 1.2-1 and bring the optical fibers 1 and 2-2 closer together, the light incident on the optical fiber 1 is emitted from the optical fiber 2-2.

Next, FIG. 6 shows a second example of an optical switch using a reflecting mirror. In FIG. 6, l is the input optical fiber, 2-1
．． 2-2 is an output side optical fiber, and 7 is a reflecting mirror. The light from the input optical fiber 1 is reflected by the reflecting mirror 7 and exits from the output optical fiber 2-1. Next, the reflecting mirror 7 is moved to cause the light from the optical fiber 1 to be emitted from the optical fiber 2-2.

FIG. 7 shows a third example, which is an optical switch using an actuator using ceramic. What is shown in Figure 7 is the Research and Practical Application Report, Vol. 30, No. 11 (1981).

ppH 7 to 130 (published by Nippon Telegraph and Telephone Public Corporation/Telecommunications Research Institute). In Fig. 7, 1 is a movable input optical fiber, 2-1.2-2 is a fixed output optical fiber, 8 is a ceramic bimorph,
9 indicates an applied voltage source. The bimorph holds a metal plate between two
Two pieces of ceramic are bonded together with their faces with different polarization directions, and the side to which voltage is applied is fixed. An optical fiber 1 is attached to the side opposite to the side to which a voltage is applied, and is opposed to the middle of the two output side optical fibers. When the voltage from the voltage source 9 is applied in a pulsed manner, the ceramic 8 bends at that moment, and instantaneously switches the optical fiber 1 to a position facing the optical fiber 2-1, for example. In addition, if the voltage values are applied with opposite positive and negative values, the optical fiber 1 is connected to the optical fiber 2-2.
It is switched to the position facing the

[Problem to be solved by the invention]

Conventional optical switches each have their own drawbacks.

In the example of the use of a prism in FIG. 5, it is difficult to align the optical axes of the optical fibers, and the prism requires high machining accuracy, and must be sufficiently polished, that is, expensive.

Furthermore, since the prism itself has a considerable weight, it requires a large amount of force to instantaneously rotate or move it, requiring at least 20 milliseconds to switch the optical fibers.

In the example shown in FIG. 6 in which a reflecting mirror is used, it is necessary to manually move screws in order to adjust the inclination of the reflecting mirror so that the optical fiber forms a predetermined transmission path. It was also necessary to make fine adjustments each time the optical fiber was switched. In order to maintain good reflectivity, the reflective surface of the mirror had to be coated with a reflective film material and constantly polished. Therefore, it became expensive.

In the example of using ceramic in Fig. 7, when the applied voltage is returned to zero after the ceramic is bent, as shown in Fig. 8, which shows the relationship between the applied voltage and the displacement of the ceramic tip,
The tip does not return to the base point. Therefore, when the same voltage is applied the next time, the previous displacement position is not reached, making it impossible to repeatedly switch and connect in a short time. For example, displacement 2
When 50 microns was obtained and returned, the hysteresis was 25 microns, which is about half the core diameter of an optical fiber, which is 50 microns, and it cannot be used as it is as an optical transmission switch.

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks and to provide an optical switch that can easily and accurately align the optical axis by using a specific bending displacement piezoelectric actuator.

[Means to solve the problem]

FIG. 1 is a diagram showing the basic configuration of the present invention. In FIG. 1, l indicates an input optical fiber, 2-1.2-2 two output optical fibers, 9 a voltage source, and lO a bending displacement piezoelectric actuator.

Two output side optical fibers 2-1, 2-2 and the opposing 1
Consists of input end optical fiber 1, input end optical fiber 1
The present invention has the following configuration in an optical switch that switches the optical path by moving light from the main body.

That is, the input optical fiber 1 is attached to the bending displacement side of the bending piezoelectric actuator IO having a polarization inversion layer.

[Effect]

In the configuration shown in FIG. 1, when a DC voltage from the voltage source 9 is instantaneously applied to the piezoelectric actuator 10, the input side optical fiber 1 is bent to the opposite output side optical fiber 2-1 due to the bending displacement of the actuator IO. It is switched from 2-2 to 2-2. When the DC voltage is removed, the piezoelectric actuator 10 remains at the initial position, so that the input optical fiber 1 again faces the output optical fiber 2-2. At this time, the relationship between the displacement of the piezoelectric actuator lO on the side to which the input optical fiber l is bonded and the voltage value of the voltage source 9 is as shown in FIG. That is, if the initial position of the input optical fiber 1 is the base point ○, and the position displaced to face the output optical fiber 2-2 is D, the position displaced by voltage application and erasure is ○ → D → O becomes. Therefore, since hysteresis does not occur when the bending side of the actuator is displaced in response to voltage changes, optical axis alignment can be performed with high precision.

Here, the term "polarization inversion layer" refers to a crystal plate formed in a special state by heat treatment in order to obtain a bending type actuator. That is, when heat treatment is performed at a temperature slightly lower than the Curie point of the crystal plate material, a layer with spontaneous polarization is formed without applying an electric field. The inversion layer is formed on the ten-face side of the plate with respect to spontaneous polarization, and its thickness increases as the heat treatment temperature increases and the treatment time increases. In the reverse polarization, the Y and Z axes of the crystal are in the opposite direction to those of the original crystal, and the signs of all piezoelectric constants are opposite to those of the original crystal. When electrodes are attached to the upper and lower surfaces of this plate and a voltage is applied, the sign of the longitudinal stretching strain that occurs in reversed polarization and non-reversed polarization becomes opposite, resulting in bending displacement. In this way, a bending displacement actuator can be realized using a single piezoelectric plate without an adhesive layer or an intermediate metal plate. It was found that hysteresis does not occur when this actuator is used.

〔Example〕

FIG. 3 shows the configuration of an embodiment of the present invention. In FIG. 3, numeral 10 is an actuator, in particular a lithium niobate whose polarization is inverted by a Y-plate rotated by 140 degrees. Here, the molecular formula of lithium niobate is LiNb○, and rLN
(lithium niobate)". LN
is a single crystal with great piezoelectricity and a high Curie point of 1200 degrees Celsius.

The direction in which elements are cut out from this material is approximately 14 mm from the Y axis.
When set to 0 degrees, the piezoelectric constant is larger, that is, the amount of displacement for a constant applied voltage is larger. -30,3X 10-”C for effective piezoelectric strain constant d22
/H value was obtained. In FIG. 3, reference numeral 11 indicates a holder, which holds one end of the LNIO in a fixed manner.

When a DC voltage from voltage source 9 is applied to LNlo, optical fiber 1 is switched to optical fiber 2-2.

Figure 4 is a diagram showing the relationship between the cutting angle and the strain constant.
The maximum value was obtained as above at 40 degrees. At that time, the electromechanical coupling coefficient, which represents energy conversion efficiency, was 51%.
This is a much larger value than ceramic.

〔Effect of the invention〕

In this way, according to the present invention, since the polarization-inverted bending displacement actuator is used, the switching of the optical fiber can be easily controlled by the applied voltage.
At that time, switching is possible without hysteresis. That is, even if the optical fibers are repeatedly switched, it is not necessary to make fine adjustments to the axis alignment.

Therefore, an optical switch with good performance can be obtained at low cost.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle configuration of the present invention. FIG. 2 is a diagram showing the relationship between voltage and displacement in the piezoelectric actuator of FIG. 1. FIG. 3 is a diagram showing the configuration of an embodiment of the present invention. Figure 4 is LN
FIG. 5, FIG. 6, and FIG. 7 are diagrams showing the conventional optical wave formation, and FIG. 8 is an explanatory diagram of the operation of FIG. 7. l...Input side optical fiber 2-2.2-2...Output side optical fiber 9...Voltage source lO...Bending displacement piezoelectric actuator touch structure

Claims (1)

[Claims] I, consisting of two output side optical fibers (2-1) (2-2) and one input side optical fiber (1) facing each other, the input side optical fiber (1) An optical switch that switches the optical path by moving light from the input side, characterized in that the input side optical fiber (1) is attached to the bending displacement side of a bending displacement piezoelectric actuator (10) having a polarization inversion layer. . II. An optical switch according to claim 1, wherein the piezoelectric actuator in the optical switch is made of lithium niobate whose polarization is inverted by a Y-plate rotated by 140 degrees.