JPS6141131A - 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 thermion based on the measured ambient temperature of the optical switch and power supplied to thermion. CONSTITUTION:Ambient temperature TL is read based on the detected signal by a temperature detecting device 26 and the power W supplied to a heating element 6 is calculated based on the detected signal by a voltage detecting device 24 and a current detecting device 25. Next, when the heating element 6 is supplied with power W at the ambient temperature equal to a reference temperature TLO, a temperature gradient ¦SO¦ to be made in a crystal 5 is calculated and the temperature gradient ¦S¦ to be made in the crystal 5 based on the temperature TL and power W. Then, the temperature gradients ¦S¦ and ¦SO¦ are compared with each other, and if gradient ¦S¦ is greater than gradient ¦SO¦, the resistance value of variable resistance device 23a is adjusted high by a constant value to reduce the power supplied to heating element 6 and the temperature on the lower surface of the crystal 5 is lowered to make the temperature gradient of the crystal 5 small. If the gradient ¦S¦ is less than ¦SO¦, the resistance value of variable resistance 23a is made low by a constant value to make the temperature gradient inside the crystal 5 great.

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 provided with a heating element such as Cr and a Vertier element, and changes the refractive index gradient formed in the optical material by switching the power supplied to the heating element and the Vertier element, thereby displacing the light output position. Are known. 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 or the Vertier element is constant, the temperature gradient formed within the optical material changes depending on the ambient temperature. Furthermore, even if the temperature gradient formed within the optical material is the same, if the surface temperature of the optical material changes due to a change in the ambient temperature, the refractive index gradient will change. 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 a switch.

[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 supply power switching means for switching power supply to multiple stages, the optical switch includes a temperature detector for detecting the temperature around the optical switch, a power measurement means for measuring the power being supplied to the thermal element, and the above-mentioned detection. 1. power control means for controlling the power supplied to the thermal element such that a predetermined refractive index gradient is formed in the optical material based on the measured temperature and the measured power; It is characterized by

The supplied power switched by the supply-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 invention, the temperature around the optical switch is measured as well as the power being supplied to the thermal element. Based on the measured temperature and power, the power supplied to the thermal element is controlled so that a predetermined refractive index gradient is formed. Therefore, a predetermined refractive index gradient is formed within the optical material regardless of the ambient temperature, and variations in the refractive index gradient due to changes in the ambient temperature can be compensated for. As a result, the optical switch can be operated stably.

DESCRIPTION OF THE EMBODIMENTS FIGS. 1 to 4 show a first embodiment of the present invention. The light transmitted by the input optical fiber (1) is collimated by the collimating lens (2) and then enters one end face of the optical deflector (3). Optical deflector (
If the incident light beam b is not deflected by 3), then
The emitted light beam b1 emitted from the other end face is guided to the output optical fiber (4a). When the incident light beam b is deflected by the optical deflector (3), the output light beam b2 is guided to the output optical fiber (4b) as shown by the chain line. If necessary, these optical fibers (4a) (
A condenser lens is arranged at the front end surface position of 4b).

The optical deflector (3) is made of a dielectric crystal having a thermo-optical effect, such as a lithium niobate (LtNbOa) crystal (5).
A heating element (6) is provided on the lower surface of the crystal (5), and radiation fins (7) are provided on the upper surface of the crystal (5). The heating element (6) is formed, for example, by vacuum-depositing Ni-Cr or T1 on the lower surface of the crystal (5).

Electric power is supplied to the heating element (6) from the drive circuit (20). The drive circuit (20) includes an output voltage (current) adjustment circuit (23) that includes a DC power supply (21), a switch (22), and a variable resistor (23a) for adjusting the output voltage of the drive circuit (20). It is composed of The drive circuit (20) also includes a voltage detector (24) and a current detector (25) for detecting the voltage and current supplied to the heating element (6).
) are provided for each.

When the switch (22) is off, no power is supplied to the heating element (6). Therefore, the temperature gradient and refractive index gradient within the crystal (5) are zero, and the incident light beam b is directed toward the crystal (5).
5), and its output light beam b1 is guided to the output optical fiber (4a). When the switch (22) is turned on, power is supplied to the heating element (6), and the heating element (6)
generates a fever. As a result, the lower surface of the crystal (5) is heated, a temperature gradient is generated inside the crystal (5) in the vertical direction, and this temperature gradient generates a refractive index gradient inside the crystal (5). In this optical deflector (3), a refractive index gradient occurs in which the refractive index of the lower part becomes relatively high and the refractive index of the upper part becomes relatively low (the refractive index of the crystal has a positive temperature dependence). case). Therefore, the incident light beam b is deflected downward, and the output light beam b2 is directed to the output optical fiber (4b
).

Note that if the crystal (5) has a negative temperature dependence in 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 be changed. It turns upside down.

FIG. 2 shows the distribution of temperature T in the vertical (X) direction that occurs in the crystal (5) when constant power is supplied to the heating element (6). The solid line shows the temperature distribution when the ambient temperature (which is considered to be approximately equal to the temperature of the upper surface of the crystal (5)) is the reference temperature TLO, for example, 25°C. The temperature THO is the concentration on the lower surface of the crystal (5) when the constant electric power is supplied to the heating element (6) when the ambient temperature is the reference temperature TSO. When the ambient temperature changes to a temperature TL1 higher than the reference temperature TLO by ΔT,
The temperature of the top surface of the crystal (5) will be approximately equal to TLI. The line representing the temperature gradient (change in temperature in the x direction) shifted to the high temperature side by ΔT is shown as a chain line, and the temperatures of the upper and lower surfaces of the crystal (5) are represented by TLl and THl, respectively. . When the ambient temperature rises by ΔT and the temperature of the top surface of the crystal (5) reaches TLI, the same power as above is applied to the heating element (6).
), the temperature at the bottom surface of the crystal (5) does not necessarily reach THL. Therefore, it is necessary to perform temperature compensation so that even if the ambient temperature changes, a temperature gradient approximately equal to the temperature gradient when the ambient temperature is at the reference temperature TLI is formed in the crystal (5).

FIG. 3 shows the temperature-refractive index characteristics of crystal (5). As can be seen from this figure, the change in the refractive index hole of the crystal (5) with respect to temperature T is not linear, so even if the temperature gradient (change in temperature in the x direction) is constant, the temperature T will vary. In this case, the refractive index gradient takes on different values. therefore,
In order to perform temperature compensation more accurately, it is preferable to always obtain a refractive index gradient that is equal to the refractive index gradient when the ambient temperature is the reference temperature TLO, even if the ambient temperature changes.

In order to perform such temperature compensation, the optical switch includes, in addition to the drive circuit (20), a concentration detector (26) for detecting the ambient temperature and the variable resistor (23a).
A power supply control device (27) is provided that controls the power supplied to the heating element (6) by controlling the resistance value of the heat generating element (6). The temperature detector (26) is, for example, a thermocouple, a thermistor, etc., and since it is used to measure the ambient temperature, it may be placed anywhere in the room, but if it is installed in the case of the optical deflector (3), , and the optical deflector (3) via a heat insulating material. The power supply unit Wl (27) is comprised of a central processing unit t (CPU), memory, etc. (not shown). The power supply control device (27) includes a switch (22).
input signal as well as voltage detector (24), current detector (
25) and the detection signals of the temperature detector (26) are respectively input.

FIG. 4 shows the temperature compensation processing procedure by the power supply control device (27). Based on the input signal of the switch (22), it is determined whether the switch (22) is turned on (step (41)).

If the switch (22) is not turned on, wait until the switch (22) is turned on. When the switch (22) is off, there is no need for temperature compensation.

If the switch (22) is turned on, it is determined whether the switch (22) has just been turned on by comparing the state of the switch (22) in the previous temperature compensation routine. (Step (42)
)). If the switch (22) has just been turned on, the temperature distribution within the crystal (5) is maintained until it reaches a steady state (step (43)). Judgment as to whether the temperature distribution within the crystal (5) has reached a steady state is based on the power being supplied to the heating element (6), for example, based on the detection signals of the voltage detector (24) and current detector (25). This is done depending on whether the integrated value of has reached a certain value. Preferably, this constant value also changes depending on the ambient temperature TL.

When the temperature distribution within the crystal (5) reaches a steady state, the ambient temperature TL is read based on the detection signal of the temperature detector (26) (step (44)). Above step (42)
If it is determined that the switch (22) has not just been turned on, the temperature distribution is already in a steady state, so the process immediately moves to step (44).
The ambient temperature TL is read. When the temperature TL is read, the electric power W being supplied to the heating element (6) is calculated based on the detection signals of the voltage detector (24) and the current detector (25) (step (45)'). Then, when the ambient temperature is the reference temperature TLO, step (
The power equal to the power W calculated in 45) is the heating element (6)
The temperature gradient +801 that should be formed within the crystal (5) when the crystal (5) is supplied is calculated (step (46)). Furthermore, the temperature gradient +81 formed in the crystal (5) is calculated based on the ambient temperature TL read in step (44) and the electric power W calculated in step (45) (step (47)). .

The temperature gradients l501 and +31 can be calculated by, for example, determining experimentally or computationally the relationship between the temperature gradient and the electric power supplied to the heating element (6), using the ambient temperature as a parameter. .

Next, both calculated temperature gradient positions sI and l5ol are compared (step (48)). If both temperature gradient positions sI and +801 are equal to each other, step (41)
Return to If the temperature gradient position 8+ is greater than 1801, the resistance value of the variable resistor (23a) is increased by a certain value (step (49)). This reduces the power supplied to the heating element (6) and lowers the temperature of the lower surface of the crystal (5). As a result, the temperature gradient in the crystal (5) becomes smaller.

If the temperature gradient +31 is smaller than 1801, the resistance value of the variable resistor (23a) is lowered by a certain value (step (50)). This increases the power supplied to the heating element (6) and raises the temperature of the lower surface of the crystal (5). As a result, the temperature gradient within the crystal (5) increases.

A variable resistance (
When the resistance value of 23a) is adjusted (step (49) (
50)) Since the temperature distribution of the crystal (5) is changed, a certain period of time required for the temperature distribution to reach a steady state is allowed to elapse (step (51)). After a certain period of time has elapsed, the process returns to step (41), and the series of processes (steps (41) to (51)) described above are repeated. This ensures that a temperature gradient is always formed in the crystal (5) that is equal to the temperature gradient that would be formed if the ambient temperature were the reference temperature TLO, regardless of the ambient temperature. Therefore, fluctuations in the temperature gradient (refractive index gradient) due to changes in ambient temperature are compensated for, and the emitted light beam b2 can always be efficiently incident on the output optical fiber (4b).

In step (46) above, when the ambient temperature is the reference temperature TLO, the refractive index gradient that should be formed in the crystal (5) when power equal to the power W is supplied to the heating element (6) is calculated. In step (47), the refractive index gradient formed in the crystal (5) is calculated based on the ambient temperature TL and the electric power W, and the variable resistor ( The resistance value of 23a) may be adjusted. Such calculation of the refractive index gradient can be performed by, for example, determining in advance the relationship between the refractive index gradient and the electric power supplied to the heating element (6) using the ambient temperature as a parameter.

In addition, in order to shorten the time required for the temperature gradient inside the crystal (5) to reach a steady state, a large current is passed through the heating element (6) for a short period of time when the switch (22) is turned on. Such a circuit may be provided in the drive circuit (20). Heating element (
6) It is preferable that the value of the current supplied for a short period of time is also controlled in accordance with the ambient temperature.

5 and 6 show a second embodiment of the invention. In FIG. 5, the same parts as in FIG. 1 are given the same reference numerals and their explanations will be omitted.

This optical switch consists of an optical deflector (3^), a drive circuit (20
Part A) and part of the processing of the power control device (27) are different from those of the first embodiment.

Optical deflector (3A) is lithium niobate (LiNb03)
Vertier elements (6A) are provided on the upper and lower surfaces of the crystal (5), respectively. As is well known, the Vertier element (6A) has at least one set of semiconductors (9) of different types of conductivity between a pair of heat exchanger plates (8), and these semiconductors (9) conduct heat transfer. The connecting conductor (
The P-type and N-type are alternately connected in series through the illustrated path (as shown in the figure). When a direct current is passed through the semiconductor (9), one of the pair of heat exchanger plates (8)
Heat is generated in the heat exchanger plate (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
) and the heat exchanger plate (8) where heat absorption occurs are reversed. The outer surface of the heat exchanger plate (8) is a heat generating/endothermic surface. Each Vertier element (6A) has a heat-generating and heat-absorbing surface of one heat exchanger plate (8) that is a crystal (
5) is fixed to the crystal (5) in close contact with the upper or lower surface of the crystal (5). A heat-radiating and heat-absorbing fin (7) is fixed to the heat-generating and heat-absorbing surface of the other heat exchanger plate (8) of each Vertier element (6A).

In the Bertier element (6A), when a positive voltage is applied to the terminal (A) of the input terminals (A) and (B), heat is generated in the heat transfer plate (8) on the crystal (5) side, and the terminal When a positive voltage is applied to (B), heat absorption occurs in the heat exchanger plate (8) on the crystal (5) side. Upper Vertier element (6A)
When a positive voltage is applied to the terminal (A) of the crystal (5) and a positive voltage is applied to the terminal (B) of the lower Vertier element (6A), the upper surface of the crystal (5) is heated and the lower surface is cooled. This creates a refractive index gradient inside the crystal (5) such that the refractive index in the upper part is high and the refractive index in the lower part is low. As a result, the incident light beam b is deflected upward while propagating within the crystal (5). When a positive voltage is applied to the terminal (B) of the upper Beltier element (6A) and a positive voltage is applied to the terminal (A) of the lower Beltier element (6A), the incident light beam is deflected downward. The magnitude of the deflection angle of the light beam changes depending on the refractive index gradient (temperature gradient) formed inside the crystal (5). The refractive index gradient can be changed by power supplied to the upper and lower Vertier elements (6A).

The drive circuit (20) includes a DC power supply (21), a DC power supply ('
21) and a voltage and polarity switching circuit (22B) for switching the generated voltage and its polarity, and an output voltage adjustment circuit (23). Each Belch element (6A
) are connected in parallel to the output terminals (C) and (D) of the switching circuit (22B) so that the directions of current flow are opposite to each other.

The switching circuit (22) switches the value and polarity of the power supply voltage based on the mode designation signal from the changeover switch (22^). The mode (M
l) is set, the output voltage ■ of the switching circuit (22B) becomes Vl (=O). In this case, the incident light beam b travels straight through the crystal (5), and the output light beam b1 is guided to the output optical fiber (4a). When mode (M2) is set by the changeover switch (22^), the output voltage V of the changeover circuit (22B) is +■2
becomes. 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 (4b). When mode (M3) is set by the changeover switch (22A), the changeover circuit (22A)
2B) output voltage V is +v3 whose value is smaller than V2.
becomes. In this case, the deflection angle of the incident light beam b becomes smaller than when the mode (M2) is set, and the output light beam b is guided to the output optical fiber (4C). When the mode (M4) is set by the changeover switch (22A), the changeover circuit (22B) (7) outputs 1 voltage VhaV4 (--V3), and the incident light beam b is deflected downward, The emitted light beam b4 is guided to an output optical fiber (4d). Changeover switch (22A
), the output voltage (2) of the switching circuit (22B) becomes V5 (--V2), and the output light beam b5 is guided to the output optical fiber (4e). The output voltages V1 to ■5 of the switching circuit (22B) in each mode (Ml) to (M5) are determined by the ambient temperature TL.
The values are set such that the output light beams b1 to b5 most efficiently enter the output optical fibers (4a) to (4e) when TLO is the reference temperature TLO.

For example, a switching device (30) as shown in FIG. 6 is used as the changeover switch (22A) and the changeover circuit (22B). This switching device (3o) consists of a rotary switch (30a) and a resistor (R1) or a resistor (R2) (R
1<R2). Rotary switch (30a) switching mode (Ml) to (M
5) is the changeover mode (Ml) of the changeover switch (22A).
) to (M5), respectively.

The temperature compensation process by this power control device (27A) is almost the same as the temperature compensation process by the power control device (27) of the first embodiment (steps (41) to (51), see FIG. 4). In the first embodiment, it was determined in step (41) whether the switch (22) was turned on, whereas in this embodiment, the changeover switch (22A) is set based on the mode designation signal. The current mode (Ml) to (M5) is determined. Further, in the first embodiment, it is determined in step (42) whether or not the switch (22) has just been turned on, whereas in this embodiment, it is determined whether or not the mode has just been switched. be done. Other steps (43) to (51)
) is exactly the same as that in the first embodiment, so its explanation will be omitted.

[Brief explanation of drawings]

Figures 1 to M4 show a first embodiment of the present invention, Figure 1 is a schematic diagram showing the configuration of an optical switch, Figure 2 is a graph showing the temperature distribution inside the crystal, and Figure 3 is the temperature of the crystal. - a graph showing the refractive index characteristics; FIG. 4 is a flowchart showing the temperature compensation processing procedure by the power supply control device; FIGS. 5 and 6 show the second embodiment of the present invention; FIG. A schematic diagram showing the configuration, FIG. 6 is a configuration diagram showing an example of a changeover switch and a changeover circuit. (5)...Crystal with thermo-optical effect, (6)...Heating element, (6A)...Bertier element, (22)...Switch, (22A)...Selector switch, (22B )・
... Voltage and polarity switching circuit, (23) ... Voltage adjustment circuit, (24) ... Voltage detector, (25) ... Current detector, (26) ... Temperature detector, (27 )(27＾
)...Power supply control device. Above 4 Figure 2 'n-IQ THI 1-T Temperature T- Figure 4

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 refraction element formed within the optical material. In an optical switch having a supply power switching means for switching the power supplied to the thermal element in multiple stages in order to switch the rate gradient in multiple stages, the optical switch includes a temperature detector for detecting the temperature around the optical switch, and power measuring means for measuring the power being applied to the thermal element such that a predetermined refractive index gradient is formed in the optical material based on the detected temperature and the measured power. An optical switch comprising power control means for controlling supplied power. (2) The supply power control means calculates a temperature gradient or a refractive index gradient formed within the optical material based on the temperature detected by the temperature detector and the power measured by the power measurement means. a second calculating means for calculating a temperature gradient or a refractive index gradient formed in the optical material when power equal to the measured power is supplied to the thermal element when the ambient temperature is a reference temperature; calculation means, and based on the comparison result between the temperature gradient or refractive index gradient calculated by the first calculation means and the temperature gradient or refractive index gradient calculated by the second calculation means, both temperature gradients or refraction are calculated. An optical switch according to claim 1, comprising means for increasing or decreasing the power supplied to the thermal element such that the deviation of the rate gradient is reduced.