JPS6141130A - Optical switch - Google Patents

Abstract

PURPOSE:To achieve accurate optical switching function regardless of the change in ambient temperature by controlling the power supply to a thermal element so as to form a prescribed gradient of refractive index based on the temperature detected on both the upper and lower surfaces of optic material. CONSTITUTION:Temperatures TU and TD on the upper and lower surfaces of the dielectric crystal 16 having the temperature optical effect are read based on the detected signal in the 1st and 2nd temperature detecting devices 13 and 14 and the difference DELTAT in temperature between TU and TD, that is, ¦DELTAT¦=¦TU- TD¦ is calculated. Next, the reference temperature difference ¦DELTATn¦ corresponding to the discriminated mode is read from the memory and compared with the temperature difference ¦DELTAT¦, and if those temperature differences are the same, the resistance value of variable resistance 23a is not adjusted. However, if difference DELTAT is greater than difference ¦DELTATn¦, the resistance value of resistance 23a is adjusted upward by a constant value, thereby reducing the power supplied to Peltier element 7 to make the angle of deflection of incident light beam (b) small. If difference DELTAT is less than difference ¦DELTATn¦, the resistance value of resistance 23a is made low by a constant value to enlarge the angle of deflection of beam (b).

Description

BACKGROUND OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical switch using an optical material whose refractive index changes depending on temperature.

[Description of Prior Art] Ni is deposited on the surface of an optical material whose refractive index changes depending on temperature.
An optical switch is known in which a heating element such as -0R or a Bertier element is provided, and the refractive index gradient formed within the optical material is changed by switching the power supplied to the heating element or the Bertier element, thereby displacing the light output position. It is being Switching the power supplied to the heating element or the Vertier element changes the temperature gradient generated within the optical material, and therefore the refractive index gradient. Then, the deflection angle of the light beam incident from the end face of the optical material changes, and the exit position of the light emitted from the opposite end face is displaced, so that an optical switch function is achieved.

In such an optical switch, a refractive index gradient is formed in the optical material by heating (or cooling) the surface of the optical material, so that it is easily influenced by the surrounding temperature. Even if the power supplied to the heating element and Bertier element is constant,
The ambient temperature changes the refractive index gradient formed within the optical material. There is a problem in that the refractive index gradient fluctuates due to changes in ambient temperature, making the operation of the optical switch unstable.

Summary of the Invention [Object of the Invention] The present invention provides an optical switch that uses an optical material whose refractive index changes depending on temperature, and that can always achieve an accurate optical switching function even when the ambient temperature changes. The purpose is to provide.

[Structure, operation, and effects of the invention] The present invention provides an optical material whose refractive index changes depending on temperature;
A thermal element provided on at least one of the upper and lower surfaces of the optical material for heating or cooling the optical material, and power supplied to the thermal element for switching the refractive index gradient formed within the optical material into multiple stages. In an optical switch having a power supply switching means for switching the power supply to multiple stages, first and second temperature detectors detect the temperature of the upper surface and the lower surface of the optical material, respectively, and the temperature detected by the first and second temperature detectors. The invention is characterized by comprising power supply control means for controlling the power supplied to the thermal element so that a set refractive index gradient is formed in the optical material based on the temperatures of the upper and lower surfaces of the optical material. . The supplied power switched by the supplied power switching means includes a case where the supplied power is zero, that is, the refractive index gradient formed in the optical material is zero.

In the optical switch according to the present invention, the temperatures of the upper and lower surfaces of the optical material are detected by the first and second temperature detectors, respectively. Based on the detected temperatures of the upper and lower surfaces of the optical material, the power supplied to the thermal element is controlled so that a predetermined refractive index gradient is formed within the optical material.

Therefore, a refractive index gradient having the same magnitude as the set refractive index gradient can be formed in the optical material regardless of the ambient temperature. That is, it is possible to compensate for variations in the refractive index gradient due to changes in ambient temperature. As a result,
It becomes possible to operate the optical switch stably.

DESCRIPTION OF THE EMBODIMENTS FIGS. 1 to 3 show a first embodiment of the present invention. The light transmitted through the input optical fiber (1) is collimated by a collimating lens (2) and then condensed by a condensing lens (3). The focused light beam (incident light beam) b is incident on one end face of the optical deflector (4), travels straight through the optical deflector (4), and is emitted from the other end face as an output light beam b1, or Alternatively, depending on the refractive index gradient formed in the optical deflector (4), the output light beam is emitted as an emitted light beam b2, b3, b4, or b5 as shown by the chain line. The output light beam is transmitted through output optical fibers (5a), (5b), (5c), and (5d) depending on the output position.
) or (5C). If necessary, condenser lenses are arranged at the front end faces of these optical fibers (5a) to (5e).

The optical deflector (4) is made of a dielectric crystal with a thermographic effect, such as a lithium niobate (l i Nb03) crystal (6
), Vertier elements (7) are provided on the upper and lower surfaces of each. As is well known, the Bertier element (7) consists of semiconductors (9) of different conduction types between a pair of heat exchanger plates (8).
) are provided, and these semiconductors (9
) are connected in series so that the P type and N type are alternately connected by connecting conductors (paths shown in the figure) fixed to the heat exchanger plate (8). Direct current is passed through the semiconductor (9). and 1
Heat is generated in one of the pair of heat exchanger plates (8), and heat is absorbed in the other heat exchanger plate (8). When the direction of the current is reversed, the heat exchanger plate (8) where heat is generated and the heat exchanger plate (8) where heat is absorbed are reversed. The outer surface of the heat exchanger plate (8) is a heat generating and heat absorbing surface. Each Vertier element (7) is
One of the heat transfer plates (8) is fixed to the crystal (6) in a state in which the heat-generating and endothermic surface is in close contact with the upper or lower surface of the crystal (6). A heat-radiating and heat-absorbing fin (10) is fixed to the heat-generating and heat-absorbing surface of the other heat exchanger plate (8) of each Vertier element (7).

The Bertier element (7) has input terminals (A>(B)),
When a positive voltage is applied to the terminal (A>), heat is generated in the heat transfer plate (8) on the crystal (6) side, and when a positive voltage is applied to the terminal (B), heat is generated on the crystal (6) side. Heat absorption occurs in the hot plate (8).A positive voltage is applied to the terminal (A>) of the upper Beltier element (7), and at the same time, a positive voltage is applied to the terminal (B) of the lower Beltier element (7). When a positive voltage is applied, the crystal (6
) is heated and the bottom surface is cooled. This creates a refractive index gradient inside the crystal (6) such that the refractive index in the upper part is high and the refractive index in the lower part is low (in the case of a crystal whose refractive index has a positive temperature dependence). As a result, the incident light beam b is deflected upward in the course of propagation within the crystal (6). When a positive voltage is applied to the terminal (B) of the L-side Beltier element (7) and a positive voltage is applied to the terminal (A>) of the lower Beltier element (7), the incident light beam b is deflected downward. The magnitude of the deflection angle of the light beam b changes depending on the refractive index gradient (temperature gradient) formed inside the crystal (6).The refractive index gradient changes depending on the power supplied to the upper and lower Vertier elements (7). can be changed by

If the crystal (6) has a negative temperature dependence on its refractive index, such as titanium oxide (rutile structure), a refractive index gradient opposite to the above will be formed, and the direction of deflection of the light beam will change. It turns upside down.

The heat exchanger plate (8) of each Bertier element (7>) has a vertical through hole (
11) is open. In addition, each fin (10) has a through hole (12) that is continuous with the through hole (11) that is formed in the heat exchanger plate <8> to which the fin (10) is fixed. The upper Vertier element (7) Through holes (11) (
12), a probe (13a) of a first temperature detector (13) for detecting the temperature of the upper surface of the crystal (6) is inserted and fixed. The through holes (11) and (12) made in the heat exchanger plate (8) and the lower fins (10) of the lower Vertier element (7) have holes for detecting the temperature of the lower surface of the crystal (6). The probe (14a) of the second temperature sensor (14) is inserted and fixed. probe(
As 13a) (14a), for example, a thermocouple, a thermistor, or the like is used. The first and second temperature detectors (13) (14) are, for example, probes (13).
a') (14a) to measure the induced voltage of the thermocouple.

Power is supplied to each Vertier element (7) from a drive circuit (20). The drive circuit (20) includes a DC power supply (21),
A voltage and polarity switching four-way (22) for switching the output voltage of the DC circuit (20) and its polarity, and a variable resistor (2) for adjusting the output voltage of the switching circuit (22).
It consists of an output voltage (current) adjustment circuit (23) equipped with 3a).

Each Bertier element (7) is connected to the output terminal (
C) They are connected in parallel to (D) so that the directions of current flow are opposite to each other. Voltage adjustment circuit (23
) is connected between the output terminal (D) of the switching circuit (22) and the Vertier element (7).

The switching circuit (22) switches the output voltage (2) and polarity based on the mode designation signal from the changeover switch (24). When the mode (Ml) is set by the changeover switch (24), the output voltage of the changeover circuit (22)
becomes zero. In this case, since no current is supplied to the Bertier element (7), no refractive index gradient is formed in the crystal (6), and the incident light beam b travels straight through the crystal (6), and its output light beam b1 is guided to an output optical fiber (5a). When the mode (M2) is set by the changeover switch (24), the output voltage V of the changeover circuit (22) becomes +■2. In this case, the incident light beam b is largely deflected upward, and the output light beam b2 is guided to the output optical fiber (5b). Changeover switch (24)
When the mode (M3) is set, the output voltage ■ of the switching circuit (22) has a value of +v3, which is smaller than vl. In this case, the deflection angle of the incident light beam b is smaller than when the mode (M2) is set, and the output light beam b3 is connected to the output optical fiber (5C).
guided by. The mode (M
4), the output voltage V of the switching circuit (22) becomes -V3, the incident light beam b is deflected downward, and the output light beam b4 is connected to the output optical fiber (5d
). The mode (
M5) is set, the output voltage V of the switching circuit (22) is 1.2, and the output light beam b5 is guided to the output optical fiber (5e).

As the changeover switch (24) and the changeover circuit (22), for example, a changeover device (30) as shown in FIG. 2 is used. This switching device (30) consists of a rotary switch (30a) and a resistor (R1) or a resistor (R2) (R1<
R2>. Rotary switch (30a) switching mode (Ml) to (M5>
is the changeover mode (Ml) of the changeover switch (24) ~ (
M5) respectively.

The resistance value of the variable resistor (23a) of the voltage adjustment circuit (23) is controlled by the power supply control device (25). The power supply control system (25) is a central processing unit (not shown).
It consists of a CPU (CPU), memory, etc. The power supply control device (25) includes first and second temperature detectors (13) that detect the temperatures of the upper and lower surfaces of the crystal (6), respectively.
) (14) detection signal and changeover switch (24)
) mode designation signal is input. The supply power control device (25) compensates for variations in the refractive index gradient in the crystal (6) due to changes in the ambient temperature, i.e. variations in the deflection angle of the incident light beam b, so as to adjust the power at which the output light beam is to be guided. This is to ensure that the light enters the optical fiber correctly.

Output light beams (b2) to (b5) are connected to output optical fibers (
5b) - (5e) Temperature difference between the upper and lower surfaces of the crystal (6) to obtain a deflection angle for correct incidence (reference temperature difference) 1
ΔT21 to 1ΔT51 are determined in advance. Then, the reference temperature difference is 1△ for each mode (M2) to (M5).
T21 to 1ΔT51 are stored in the memory.

FIG. 3 shows the temperature compensation processing procedure by the CPU of the power control device @ (25). Based on the mode designation signal,
Mode (Ml) set in the changeover switch (24)
~(M5) is determined and stored in memory (step (
31)). [Step (32)
)). If it is determined that there has been a mode switch, the crystal (
Since the temperature distribution within the crystal (6) changes, a certain period of time required for the temperature distribution within the crystal (6) to reach a steady state is waited for (step (33)). After a certain period of time has elapsed, based on the detection signals of the first and second lagoon detectors (13) (14), the temperature TU of the upper surface of the crystal (6) and the temperature of the lower surface -l-D'/)< (Step (3)
4)). If it is determined in step (32) that the mode has not been switched, the process moves to step (34) without waiting for the predetermined time to elapse, and the temperature TU, T
D is read.

When the temperatures TU and TD of the upper and lower surfaces of the crystal (6) are read (step (34)), the difference between these temperatures 1ΔK1=lT
U-TD+ is extracted (step (35)). Next, the reference temperature difference 1ΔTnl (n is 2.3.4 and 5) corresponding to the mode determined in step (old) above is read from the memory, and the temperature difference ΔT calculated in step (34) and are compared (step (36)). If the calculated temperature difference Δd and the reference temperature difference 1Δlnl are equal,
Since the deflection angle of the incident light beam b is set by the changeover switch (24) and is equal to the appropriate deflection angle in the "mode", step (31) can be performed without adjusting the resistance value of the variable resistor (23a). ).If the calculated temperature difference ΔT is larger than the reference temperature difference IT01, the deflection angle of the incident light beam b is greater than the appropriate deflection angle in the mode set by the changeover switch (24). Since the deflection angle is also large, the resistance value of the variable resistor (23a) is increased by a certain value (step (37)).As a result, the power supplied to the Bertier element (7) is reduced, and the incident light is The deflection angle of the beam b becomes smaller. If the calculated temperature difference ΔT is smaller than the reference temperature difference 1ΔTnl, the deflection angle of the incident light beam b becomes smaller.
Since the deflection angle is smaller than the appropriate deflection angle in the mode set by the variable resistor (23a
) is lowered by a certain value (step (38)
). This increases the power supplied to the Beltier element (7) and increases the deflection angle of the incident light beam b.

When the resistance value of the variable resistor (23a) is adjusted according to the magnitude of the calculated temperature difference 1ΔT1 and the reference temperature difference 1ΔTnl (steps (37,) (38)), the crystal (6)
Since the temperature distribution within is changed, a certain period of time required for the temperature distribution to reach a steady state is waited for (step (39)). Then, after a certain period of time has passed, the process returns to step (31) and the above series of processes (steps (31) to
(39)) is repeated. This makes the deflection angle of the incident light beam b equal to the appropriate deflection angle in the mode set by the changeover switch (24), regardless of the ambient temperature. Therefore, the output light beam b
1 to b5 are the output optical fibers (5
The light is always efficiently incident on a) to (5e).

FIG. 4 shows a second embodiment of the invention. Components in FIG. 4 that are the same as those in FIG. 1 are given the same reference numerals, and their explanations will be omitted. Optical deflector (4A
) is a heating element (
7A) is provided on the top surface of the crystal (6).
0) is provided. The heating element (7A) is formed by, for example, vacuum-depositing Ni-0r or Ti on the lower surface of the crystal (6).

When the selector switch (24A> is off, the heating element (7
A) is not supplied with current. Therefore, the incident light beam b travels straight through the crystal (6), and the output light beam b6 is guided to the output optical fiber (5[). Changeover switch (
24A) is turned on, current is supplied to the heating element (7A) and the heating element (7A) generates heat. This heats the lower surface of the crystal (6), creating a refractive index gradient inside the crystal (6) such that the refractive index in the upper part is relatively low and the refractive index in the lower part is relatively high.

Therefore, the incident light beam b is deflected downward, and its output light beam b7 is guided to the output optical fiber (5g).

The temperature compensation process by the power supply control device (25) in this optical switch is different from the temperature compensation process in the first embodiment (
This step is almost the same as steps (31) to (39) (see FIG. 3). In the first embodiment, the modes (Ml) to (M
5), whereas in this embodiment it is determined whether the changeover switch (24A) is turned on. Further, in the first embodiment, it is determined in step (32) whether or not the mode has been switched, whereas in this embodiment, it is determined whether or not the changeover switch (24A> has just been turned on). .Then, if the changeover switch (24A is immediately turned on, the crystal (6)
After waiting for a certain period of time required for the temperature distribution inside the device to reach a steady state, the process moves to step (34). Determine whether the temperature distribution within the crystal (6) has reached a steady state by, for example, calculating the integrated value of the power being supplied to the heating element (7A), and when it is determined that the temperature distribution has reached a steady state, step It is also possible to move to (34).

Steps (34) to (39) are the same as in the first embodiment, so their explanation will be omitted.

In the second embodiment, in order to shorten the paralysis time when the m-degree distribution in the crystal (6) reaches a steady state after the switch (24A> is turned on), heat is generated when the switch (24△> is turned on). A circuit (driving a circuit that causes a large current to flow through the body (7A) for a short period of time) may be provided in the circuit (2OA>).

In the above embodiment, no matter what the ambient temperature is,
It is assumed that if the temperature difference between the upper and lower surfaces of a crystal with a thermo-optic effect is constant, the same refractive index gradient will always be formed within the crystal, but even if the temperature difference is constant, if the absolute temperature is different, If the refractive index gradient changes slightly, temperature compensation may be performed in consideration of absolute temperature.

[Brief explanation of the drawing]

1 to 3 show a first embodiment of the present invention, FIG. 1 is a schematic diagram showing the configuration of an optical switch, FIG. 2 is a configuration diagram showing an example of a changeover switch and a changeover circuit, and FIG. 4 is a flow chart showing the temperature compensation processing procedure of the power control device, and FIG. 4 shows a second embodiment of the present invention, and is a schematic diagram showing the configuration of an optical switch. (6)... Crystal with thermo-optical effect, (7>... Peltier element, <7A>... Heating element, (13) (1
4...? fillf detector, (22)... Voltage and polarity switching circuit, (23)... Voltage adjustment circuit, (24
) (24A>... selector switch, (25>...
Supply power control I device. 4 people other than above

Claims (2)

[Claims] (1) An optical material whose refractive index changes depending on temperature, a thermal element provided on at least one of the upper and lower surfaces of the optical material for heating or cooling the optical material, and a refractive index gradient formed within the optical material. In an optical switch having a power supply switching means for switching power supply to a thermal element in a plurality of stages in order to switch the power to a thermal element in a plurality of stages, the optical switch includes first and second temperature detectors for respectively detecting the temperature of the upper surface and the lower surface of the optical material. , and the temperatures of the upper and lower surfaces of the optical material detected by the first and second temperature detectors, the power supplied to the thermal element is adjusted so that a set refractive index gradient is formed in the optical material. An optical switch comprising supply power control means for controlling. (2) The supply power control means determines in advance the difference between the detected temperature of the first temperature detector and the detected temperature of the second temperature detector, and the difference between the upper and lower surfaces of the optical material to obtain a set refractive index gradient. The optical switch according to claim (1), wherein the optical switch increases or decreases the power supplied to the thermal element based on the comparison result between the two temperature differences so that the deviation between the two temperature differences decreases. .