JPH10221660A - Wavelength selection filter and resonance wavelength selection control method used for the filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength selection filter capable of attaining the temp. stabilization of a resonance wavelength in a Fabry-perot etalon type resonator without correctly maintaining a parallel flat plate structure in an etalon structure with an optical accuracy with respect to a temp. change, and to provide a resonance wavelength selection control method used for the filter. SOLUTION: A driving means 30(40) for executing a control holding a resonance wavelength λ1 constantly by impressing a wavelength selection voltage holding the capacitance of a Fabry-perot etalon type resonator 20 constantly on an etalon medium 208 interposed between electrodes for controlling a refractive index is provided and at the time of the capacitance of the resonator 20 is fluctuated, a resonance wavelength selection process executing a control holding the resonance wavelength λ1 constantly by selecting an impression voltage in an inductive resonance area in the resonance characteristic of an electric resonance system and by impressing it as a wavelength selection voltage on the medium is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device and a method for adjusting the same, and more particularly, to a wavelength selection filter having a spectral function capable of selectively emitting an optical signal of a desired wavelength from incident optical signals, and The present invention relates to a resonance wavelength selection control method used for this.

[0002]

2. Description of the Related Art FIG. 7 is a layout diagram for explaining a conventional wavelength selection filter. Conventionally, this type of wavelength selection filter 9 has a TN (Twisted Nema) in the etalon medium.
tic) It had a Fabry-Perot etalon resonator 3 using a liquid crystal material having an alignment structure, an incident side optical fiber 4A, and an outgoing side optical fiber 4B.

[0003] Fabry-Perot etalon resonator 3
Is, as shown in FIG. 7, an ITO transparent electrode B, a dielectric multilayer reflective film C, and a rubbed polyimide alignment film D.
Are formed on each of the pair of transparent substrates A, A in this order, and the pair of transparent substrates A, A are further interposed via spherical spacers F, F (sphere diameter = about 10 [μm]). An etalon structure having a resonance length (optical path length nd1) has been realized by being accurately arranged on a parallel plate with optical precision.

A transparent substrate A and an incident side optical fiber 4A
And an interface between the transparent substrate A and the emission side optical fiber 4B, an AR coat film (antireflection film) E was provided. The rubbed polyimide (P
I) Between the alignment films D, D, a TN liquid crystal G in which the twist angle ψ between the polyimide alignment films D, D is precisely 90 degrees with optical precision is injected as a birefringent etalon medium. I was

The incident side optical fiber 4A propagates an optical signal (incident light 1, wavelength λ in FIG. 7) and has a center in the Fabry-Perot etalon type resonator 3 perpendicular to the plane of incidence of the resonator 3. The optical signal (incident light 1) was arranged to be incident along the axis (that is, precisely parallel to the central axis with optical precision).

The output side optical fiber 4B is made of
Along the central axis perpendicular to the exit plane (the exit plane that is exactly parallel to the entrance plane with optical precision) from the Perot etalon resonator 3 (that is, exactly parallel to the central axis with the optical precision) Outgoing light signal (outgoing light 2 in the figure, resonance wavelength λ1)
(Unit: [μm])), and was arranged to propagate the received optical signal (outgoing light 2).

The wavelength selection filter 9 having such a configuration controls the refractive index of the TN liquid crystal material by using a driver H to control the resonance length between the dielectric reflection films C (determined based on the refractive index and the wavelength). The optical signal having a predetermined resonance wavelength λ1 is selectively transmitted from the optical signal (incident light 1) perpendicularly incident from the incident side optical fiber 4A to the emitting side optical fiber by selecting the optical path length to be emitted. A method of controlling the selection of the resonance wavelength to be emitted has been used.

[0008]

In the wavelength selection filter 9 having such a structure and the resonance wavelength selection control method used in the filter, the temperature stabilization of the resonance wavelength λ1 in the optical path A of the Fabry-Perot etalon resonator 3 is performed. In order to achieve this, it is required that the parallel plate structure in the etalon structure shown in FIG. 7 be accurately maintained with optical precision against a temperature change.

That is, the thermal expansion and thermal contraction of the birefringent etalon medium G and the spacer F in the etalon structure, or the resonance length between the dielectric reflective films C and C caused by such thermal expansion and thermal contraction ( That is, it is required to compensate for a change in the resonance length (optical path length nd1) (that is, thermal expansion or thermal contraction).

However, in such a conventional wavelength selection filter 9 and the resonance wavelength selection control method used in the conventional filter, the dielectric material is caused by thermal expansion and contraction of the birefringent etalon medium G and the spacer F. When the resonance length between the reflection films C (ie, the resonance length (optical path length nd1)) changes (ie, expands and contracts), there is no means for compensating the resonance wavelength for these changes. There is a technical problem that it is difficult to stably maintain the selected state of one resonance wavelength λ1 (that is, to maintain the temperature stability of the resonance wavelength).

Further, since the refractive index of the birefringent etalon medium G (that is, the ordinary light refractive index no and the extraordinary light refractive index ne) has temperature dependence, the resonance length (optical path length nd1)
Has the same temperature dependence, and as a result, there is a technical problem that it is difficult to realize a wavelength selection characteristic stable with respect to a temperature change (that is, a wavelength selection characteristic having temperature independence).

SUMMARY OF THE INVENTION An object of the present invention is to solve such a conventional problem. In particular, the present invention is intended to electrically control a refractive index of a birefringent etalon medium to select a predetermined resonance wavelength. In a wavelength selection filter having a Perot etalon resonator, a wavelength selection voltage for maintaining a constant capacitance of a Fabry-Perot etalon resonator is applied to an etalon medium between electrodes for controlling a refractive index, and a resonance wavelength is applied. A drive means for executing control to keep the voltage constant is selected, and when the capacitance of the Fabry-Perot etalon type resonator fluctuates, the applied voltage is selected within the inductive resonance region in the resonance characteristics of the electric resonance system. The parallel plate structure in the etalon structure is subjected to the temperature change by executing the resonance wavelength selection step of controlling the resonance wavelength to be kept constant by applying it as a wavelength selection voltage. And a wavelength selection filter capable of stabilizing the temperature of a resonance wavelength in a Fabry-Perot etalon type resonator without accurately maintaining the optical accuracy with the optical precision, and a resonance wavelength selection control method used in the filter. The task is to

That is, the thermal expansion and thermal contraction of the birefringent etalon medium and the spacer in the etalon structure, or the change of the resonance length (resonance length) between the dielectric reflective films due to such thermal expansion and thermal contraction. (Thermal expansion and thermal contraction) can be compensated, and a wavelength selection filter capable of stabilizing the temperature of a resonance wavelength in a Fabry-Perot etalon resonator and a resonance wavelength selection control method used for the filter are provided. The task is to

More specifically, the resonance length (ie, resonance length) between the dielectric reflective films changes (ie, expansion and contraction) due to thermal expansion and contraction of the birefringent etalon medium, spacers, and the like. In this case, by providing a drive unit and a resonance wavelength selection step for compensating the resonance wavelength for these changes, it is possible to stably maintain the selected state of one resonance wavelength (maintain the temperature stability of the resonance wavelength). And a resonance wavelength selection control method used for the wavelength selection filter.

Further, the resonance length (resonance length) of the birefringent etalon medium has the same temperature dependence due to the temperature dependence of the refractive index (ordinary refractive index no and extraordinary refractive index ne) of the birefringent etalon medium. Provided is a wavelength selection filter capable of realizing a wavelength selection characteristic (wavelength selection characteristic having temperature independence) that is stable against temperature changes even when it has a filter, and a resonance wavelength selection control method used for the filter. Make it an issue.

[0016]

According to a first aspect of the present invention, there is provided a Fabry-Perot etalon type resonance apparatus capable of electrically controlling a refractive index of a birefringent etalon medium 208 to select a predetermined resonance wavelength λ1. In the wavelength selection filter having the device 20, a wavelength selection voltage for keeping the capacitance of the Fabry-Perot etalon type resonator 20 constant is applied to the etalon medium 208 between the electrodes for controlling the refractive index to thereby set the resonance wavelength λ1. The wavelength selection filter 10 includes a driving unit 30 (40) for executing control for keeping the wavelength selection filter constant.

According to the first aspect of the present invention, by providing such a driving means 30 (40), the parallel plate structure in the etalon structure is accurately maintained with optical accuracy against a temperature change. Without this, there is an effect that the temperature of the resonance wavelength λ1 in the Fabry-Perot etalon resonator 20 can be stabilized.

That is, by controlling the wavelength selection voltage so as to keep the capacitance of the Fabry-Perot etalon type resonator 20 constant, the birefringent etalon medium 208 and the spacer 207 in the etalon structure are controlled. It is possible to compensate for thermal expansion or thermal contraction or a change (thermal expansion or thermal contraction) in the resonance length (optical path length nd1) between the dielectric reflective films 205 due to such thermal expansion or thermal contraction. There is an effect that the temperature of the resonance wavelength λ1 in the Perot etalon type resonator 20 can be stabilized.

Specifically, the birefringent etalon medium 208
Length (that is, resonance length (optical path length nd) between dielectric reflection films 205 due to thermal expansion and thermal contraction of spacers 207 and the like.
1)) changes (that is, expands or contracts), and the selection state of one resonance wavelength λ1 is stably maintained by controlling the wavelength selection voltage so as to compensate the resonance wavelength λ1 for these changes. (Maintaining the temperature stability of the resonance wavelength λ1).

Further, since the birefringent etalon medium 208 has a temperature dependence of the refractive index (ordinary refractive index no and extraordinary refractive index ne), the resonance length (optical path length nd1) has the same temperature dependence. Even in the case of having a characteristic, by controlling the wavelength selection voltage so as to keep the capacitance of the Fabry-Perot etalon type resonator 20 constant, the wavelength selection characteristic ( This has the effect of realizing a wavelength selection characteristic having temperature independence.

According to a second aspect of the present invention, there is provided the wavelength selecting filter according to the first aspect, wherein the driving means includes:
Is connected to the Fabry-Perot etalon resonator 20 and forms an electric resonance system together with the resistance and the capacitance of the Fabry-Perot etalon resonator 20; An AC power supply 302 for applying an applied voltage according to the resonance characteristic of the electric resonance system as the wavelength selection voltage when the capacitance fluctuates;
And a wavelength selection filter 10 having the following.

According to the invention described in claim 2, according to claim 1,
In addition to the effects described in the above, by providing such an inductive element 306 in the driving means 30 (40), the parallel plate structure in the etalon structure is not accurately maintained with optical accuracy against a temperature change. Furthermore, there is an effect that the temperature stabilization of the resonance wavelength λ1 in the Fabry-Perot etalon type resonator 20 can be realized with a simple circuit configuration.

That is, control of the wavelength selection voltage is performed according to the resonance characteristics of the Fabry-Perot etalon resonator 20 based on the capacitance of the Fabry-Perot etalon resonator 20 and the inductive element 306. , The thermal expansion and thermal contraction of the birefringent etalon medium 208 and the spacer 207 in the etalon structure, or the resonance length (optical path length nd1) between the dielectric reflective films 205 due to such thermal expansion and thermal contraction. The change (thermal expansion or thermal contraction) can be compensated for with a simple circuit configuration, and the effect that the temperature stabilization of the resonance wavelength λ1 in the Fabry-Perot etalon resonator 20 can be realized with a simple circuit configuration is achieved. Play.

Specifically, the birefringent etalon medium 208
Length (that is, resonance length (optical path length nd) between dielectric reflection films 205 due to thermal expansion and thermal contraction of spacers 207 and the like.
1)) changes (that is, expands or contracts), the wavelength selection voltage can be controlled with a simple circuit configuration so as to compensate for the resonance wavelength λ1 with respect to these changes. Can be stably maintained (the temperature stability of the resonance wavelength λ1 can be maintained).

Further, since the birefringent etalon medium 208 has a temperature-dependent refractive index (ordinary refractive index no and extraordinary refractive index ne), the resonance length (optical path length nd1) has the same temperature dependence. Even in the case of having the inductive property, the capacitance of the Fabry-Perot etalon type resonator 20 and the inductive element 30
6 and Fabry-Perot etalon resonator 20
Since the wavelength selection voltage can be controlled with a simple circuit configuration in accordance with the resonance characteristics of (1) and (2), there is an effect that a wavelength selection characteristic (wavelength selection characteristic having temperature independence) that is stable against a temperature change can be realized.

According to a third aspect of the present invention, there is provided the wavelength selecting filter according to the second aspect, wherein the inductive element is provided.
Numeral 6 is a wavelength selection filter 10 characterized in that it is connected to the Fabry-Perot etalon resonator 20 in parallel and constitutes the electric resonance system.

According to the invention of claim 3, according to claim 2,
It has the same effect as. According to a fourth aspect of the present invention, in the wavelength selective filter according to the first aspect, the driving unit is connected to the Fabry-Perot etalon type resonator 20 in a state where the Fabry-Perot etalon is connected. A variable capacitive element 404 that can change the capacitance forming the electric resonance system together with the resistance and the capacitance of the resonator 20, and connected to the Fabry-Perot etalon resonator 20, The fabric
A variable resistance element 402 that can change the amount of resistance forming the electric resonance system together with the resistance and the capacitance of the Perot etalon resonator 20 and the Fabry-Perot etalon resonator 20 are connected. In this state, the inductance of the Fabry-Perot etalon type resonator 20 can be changed by forming an electric resonance system together with the resistance and the capacitance of the Fabry-Perot etalon type resonator 20 and the transformer 406 having a predetermined inductance. An AC power supply 302 for electromagnetically coupling to the electric resonance system and applying an applied voltage according to the resonance characteristic of the electric resonance system as the wavelength selection voltage when the capacitance fluctuates. A wavelength selection filter 10 characterized by having:

According to the invention described in claim 4, according to claim 1 of the present invention,
In addition to the effects described in the above, the resonance characteristics of the Fabry-Perot etalon type resonator 20 are improved by using a simple circuit configuration using the variable capacitive element 404, the variable resistance element 402, and the inductive element 306 with respect to the capacitance of the resonator 20 The resonance wavelength in the Fabry-Perot etalon type resonator 20 can be obtained without providing the parallel plate structure in the etalon structure accurately with optical accuracy with respect to a temperature change by providing an electric resonance system capable of changing the resonance wavelength. This has the effect of stabilizing the temperature of λ1 more easily.

Further, by changing the capacitance value of the variable capacitance element 404, the capacitance of the Fabry-Perot etalon type resonator 20 can be selected. Further, by changing the resistance value of the variable resistance element 402, the resonance sharpness of the electric resonance system can be selected, and as a result, the applied voltage −
The inclination of the capacitance characteristic can be adjusted. In addition, as a result of being able to adjust the slope of the applied voltage-capacitance characteristic, it is possible to adjust the accuracy of the capacitance of the variable capacitance element 404.

Also, by applying electromagnetic coupling to the electric resonance system via the transformer 406, the voltage applied to the AC power supply 302 can be applied to the Fabry-Perot etalon type resonance without disturbing the resonance characteristics of the electric resonance system. Can be given to the vessel 20. That is, according to the resonance characteristics of the Fabry-Perot etalon resonator 20 based on the capacitance of the Fabry-Perot etalon resonator 20, the variable capacitance element 404, the variable resistance element 402, and the inductive element 306,
By controlling the wavelength selection voltage, the birefringent etalon medium 208 and the spacer 20 in the etalon structure are controlled.
7 or a resonance length (optical path length nd) between the dielectric reflection films 205 due to such thermal expansion or thermal contraction.
1) (thermal expansion and thermal contraction) can be compensated for with a simple circuit configuration, and the temperature stabilization of the resonance wavelength λ1 in the Fabry-Perot etalon resonator 20 can be realized with a simple circuit configuration. The effect that can be performed.

Specifically, the birefringent etalon medium 208
Length (that is, resonance length (optical path length nd) between dielectric reflection films 205 due to thermal expansion and thermal contraction of spacers 207 and the like.
1)) changes (that is, expands or contracts), the wavelength selection voltage can be controlled with a simple circuit configuration so as to compensate for the resonance wavelength λ1 with respect to these changes. Can be stably maintained (the temperature stability of the resonance wavelength λ1 can be maintained).

Further, the birefringent etalon medium 208 has a temperature dependence of the refractive index (ordinary refractive index no and extraordinary refractive index ne), so that the resonance length (optical path length nd1) has the same temperature dependence. Even when the resonator has a characteristic, the Fabry-Perot etalon resonator 20 based on the capacitance of the Fabry-Perot etalon resonator 20, the variable capacitance element 404, the variable resistance element 402, and the inductive element 306 is used. Since the wavelength selection voltage can be controlled with a simple circuit configuration in accordance with the resonance characteristics of (1) and (2), there is an effect that a wavelength selection characteristic (wavelength selection characteristic having temperature independence) that is stable against a temperature change can be realized.

According to a fifth aspect of the present invention, in the wavelength selective filter according to the fourth aspect, the variable capacitive element 404 includes the Fabry-Perot etalon type resonator 2.
The wavelength selection filter 10 is characterized in that the electrical resonance system is formed in a state where the wavelength selection filter is connected in parallel with the zero.

According to the invention described in claim 5, according to claim 4,
In addition to the effects described in the above, the capacitance of the Fabry-Perot etalon resonator 20 can be selected by changing the capacitance of the variable capacitive element 404. Claim 6
In the wavelength selection filter 10 according to the fourth or fifth aspect, the variable resistance element 402 is connected to the Fabry-Perot etalon type resonator 20 in parallel with the electric resonance element. A wavelength selection filter 10 which forms a system.

According to the invention described in claim 6, according to claim 4,
Or, in addition to the effect described in 5, the resonance sharpness of the electric resonance system can be selected by changing the resistance value of the variable resistance element 402. As a result, the slope of the applied voltage-capacitance characteristic is reduced. Be able to adjust. In addition, as a result of being able to adjust the slope of the applied voltage-capacitance characteristic, it is possible to adjust the accuracy of the capacitance of the variable capacitance element 404.

The invention according to claim 7 is the invention according to claims 4 to 6
, The inductive element 306 forms the electrical resonance system in a state where the inductive element 306 is connected in parallel to the Fabry-Perot etalon resonator 20. The selection filter 10.

According to the invention of claim 7, according to claim 4,
The same effects as the effects described in 1 to 6 are achieved. According to an eighth aspect of the present invention, in the wavelength selection filter according to any one of the fourth to seventh aspects, the transformer 406 is electromagnetically connected to the electrical resonance system while being connected in series with the inductive element 306. The wavelength selection filter 10 is coupled to the wavelength selection filter 10.

According to the invention described in claim 8, according to claim 4,
In addition to the effects described in any one of (1) to (7), the voltage applied to the AC power supply 302 can be controlled by the electromagnetic coupling with the electric resonance system via the transformer 406 without disturbing the resonance characteristics of the electric resonance system. This can be applied to the Perot etalon type resonator 20.

The ninth aspect of the present invention is the first aspect of the present invention.
In the resonance wavelength selection control method used in the wavelength selection filter 10 according to the above, the wavelength selection voltage for keeping the capacitance of the Fabry-Perot etalon resonator 20 constant is applied between the electrodes for controlling the refractive index. Etalon medium 208
A resonance wavelength selection control method for use in the wavelength selection filter 10, comprising a resonance wavelength selection step of executing control for keeping the resonance wavelength λ1 constant by applying the control to the resonance wavelength λ1.

According to the ninth aspect of the present invention, a first aspect is provided.
In addition to the effects described in Nos. 1 to 8, the Fabry-Perot etalon type without maintaining the parallel plate structure in the etalon structure accurately with optical accuracy with respect to a temperature change by providing a resonance wavelength selecting step. There is an effect that the temperature stabilization of the resonance wavelength λ1 in the resonator 20 can be more easily realized.

That is, according to the resonance characteristics of the Fabry-Perot etalon type resonator 20 based on the resonance wavelength selecting step,
By controlling the wavelength selection voltage, the birefringent etalon medium 208 and the spacer 20 in the etalon structure are controlled.
7 or a resonance length (optical path length nd) between the dielectric reflection films 205 due to such thermal expansion or thermal contraction.
1) (thermal expansion and thermal contraction) can be compensated for with a simple circuit configuration, and the temperature stabilization of the resonance wavelength λ1 in the Fabry-Perot etalon resonator 20 can be realized with a simple circuit configuration. The effect that can be performed.

Specifically, the birefringent etalon medium 208
Length (that is, resonance length (optical path length nd) between dielectric reflection films 205 due to thermal expansion and thermal contraction of spacers 207 and the like.
1)) changes (that is, expands or contracts), the wavelength selection voltage can be controlled with a simple circuit configuration so as to compensate for the resonance wavelength λ1 with respect to these changes. Can be stably maintained (the temperature stability of the resonance wavelength λ1 can be maintained).

Further, since the birefringent etalon medium 208 has temperature dependence of the refractive index (ordinary refractive index no and extraordinary refractive index ne), the resonance length (optical path length nd1) has the same temperature dependence. Even if it has a characteristic, the wavelength selection voltage can be controlled with a simple circuit configuration in accordance with the resonance characteristics based on the resonance wavelength selection step, so that the wavelength selection characteristics (which have temperature independence Wavelength selection characteristics)
Is achieved.

According to a tenth aspect of the present invention, in the resonance wavelength selection control method according to the ninth aspect, when the capacitance fluctuates, the resonance wavelength falls within an inductive resonance region in a resonance characteristic of the electric resonance system. A resonance wavelength selecting step of performing a control of selecting the applied voltage and applying the selected voltage as the wavelength selection voltage to keep the resonance wavelength λ1 constant.

According to the tenth aspect of the present invention, in addition to the effect of the ninth aspect, it is possible to execute the resonance wavelength selecting step in the inductive resonance region in the resonance characteristics of the electric resonance system. As a result, a negative feedback effect using an applied voltage is obtained with respect to a change in capacitance of the Fabry-Perot etalon type resonator 20. As a result, the parallel plate structure in the etalon structure can be accurately adjusted with optical accuracy with respect to a temperature change. There is an effect that the temperature stabilization of the resonance wavelength λ1 in the Fabry-Perot etalon resonator 20 can be realized more easily without maintaining the temperature.

In other words, by performing negative feedback control of the wavelength selection voltage in accordance with the resonance characteristics in the inductive resonance region of the Fabry-Perot etalon type resonator 20 based on the resonance wavelength selection step, the etalon structure has multiple Refractive etalon medium 208 and spacer 207
Or the thermal expansion or contraction of the dielectric reflection film 205 due to such thermal expansion or contraction (optical path length nd)
1) (thermal expansion and thermal contraction) can be compensated for with a simple circuit configuration, and the temperature stabilization of the resonance wavelength λ1 in the Fabry-Perot etalon resonator 20 can be realized with a simple circuit configuration. The effect that can be performed.

Specifically, the birefringent etalon medium 208
Length (that is, resonance length (optical path length nd) between dielectric reflection films 205 due to thermal expansion and thermal contraction of spacers 207 and the like.
When 1)) changes (that is, expands and contracts), the wavelength selection voltage can be controlled with a simple circuit configuration so that the resonance wavelength λ1 can be compensated for these changes by using a negative feedback effect. This has the effect of stably maintaining the selected state of the resonance wavelength λ1 (maintaining the temperature stability of the resonance wavelength λ1).

Further, since the birefringent etalon medium 208 has a temperature dependence of the refractive index (ordinary refractive index no and extraordinary refractive index ne), the resonance length (optical path length nd1) has the same temperature dependence. Even in the case of having a characteristic, the wavelength selection voltage can be negatively controlled with a simple circuit configuration in accordance with the resonance characteristic based on the resonance wavelength selection step in the inductive resonance region of the electric resonance system, so that the temperature change In addition, it is possible to achieve more stable wavelength selection characteristics (wavelength selection characteristics having temperature independence).

[0049]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an arrangement diagram for explaining a basic configuration of a wavelength selection filter 10 of the present invention.

The wavelength selection filter 10 has a spectral function of selectively emitting outgoing light 12a (unit: [nm]) having a desired wavelength from the incident light 11a.
As shown in the figure, the Fabry-Perot etalon resonator 2
0 and torsion angle ψ (unit is [degree or radian (ra
d) The driving unit 30 (40) for performing the voltage control of [1]
And an incident optical fiber 11 as an optical transmitting means and an output optical fiber 12 as an optical receiving means, and a refractive index n of a birefringent liquid crystal material (etalon medium) 208
e, no, and the torsion angle 光 in the optical path A
(The unit is [degree (or rad)]) and the resonance wavelength λ1 (the unit is [n]) in the predetermined optical path A from the incident light 11a vertically incident from the incident side optical fiber 11.
m]) is emitted to the output-side optical fiber 12.

Such a wavelength selection filter 10 is an effective component for configuring a wavelength division multiplexing transmission system in the field of optical communication (in particular, in the field of optical fiber communication). The Fabry-Perot etalon resonator 20 has a birefringence (specifically, an ordinary refractive index no and an extraordinary refractive index n).
e) using the etalon medium 208 having the refractive index n
This is a variable wavelength filter capable of continuously and electrically controlling e and no.

As the etalon medium 208, as a material whose refractive index changes when a voltage is applied, a liquid crystal material (for example, a TN liquid crystal material which is a liquid crystal material having a homogeneous alignment, TN: Twisted Nemati) is used.
It is desirable to use c) and electro-optical materials such as LiNbO3 and PLZT.

Here, the TN alignment structure means the transparent substrate 20
By subjecting the polyimide alignment films 206 and 206 to a surface treatment so that the molecules of the liquid crystal material 208 between the liquid crystal materials 3 and 203 are twisted by 90 degrees (x-axis direction and y-axis direction), the liquid crystal molecules inside the liquid crystal cell are formed. Are structures that are uniformly twisted and distributed in the thickness direction of the etalon resonator 20.

Fabry-Perot etalon resonator 20
As shown in FIG. 1, the first transparent electrode 204A (or the second transparent electrode 204B) (film thickness = 0.5 μm or less, sheet resistance several kΩ / □ to several MΩ / □), dielectric multilayer reflective film 205
(Specifically, the reflectance is 80 to 99.9% or more), and the rubbed polyimide (PI) alignment film 206
(Film thickness = several μm or less) in this order.
3, 203, and the pair of transparent substrates 203, 203 are formed into parallel flat plates with optical precision (specifically, sub-μm-μm precision) via spacers 207, 207. The optical resonator 20 is formed according to the etalon structure arranged in the above.

An AR coating film (anti-reflection coating film) 202 is provided on each of the interface between the transparent substrate 203 and the incident side optical fiber 11 and the interface between the transparent substrate 203 and the output side optical fiber 12. Further, the twist angle in the optical path A between the polyimide alignment films 206, 206 between the rubbed polyimide alignment films 206, 206 is set.
A TN liquid crystal 208 having a birefringent property in which (the unit is [degree (or rad)]) is oriented at approximately 90 degrees is injected.

By using such a TN liquid crystal,
A wavelength selective filter having features such as high finesse and low power consumption and capable of electrically controlling the birefringence can be easily realized. The driving means 30 (40) applies a wavelength selection voltage for keeping the capacitance of the Fabry-Perot etalon type resonator 20 constant to the etalon medium 2 between the electrodes for controlling the refractive index.
08 to perform control to keep the resonance wavelength λ1 constant.

Next, a specific fabrication process of the Fabry-Perot etalon resonator 20 will be described. Assuming that the fibers are integrated, the incident side optical fiber 1
In order to reduce the diffraction loss between 1 and the output side optical fiber 12, the structure of the wavelength selection filter 10 is required to have a short element length.

An SiO 2 film is formed on the transparent substrate 203 by a sputtering method, and subsequently, a spacer 207 is formed by photolithography. The first transparent electrode (second transparent electrode) 204A (or 204B) (film thickness = 0.5 μm or less, sheet resistance several kΩ /
□ to several MΩ / □), dielectric multilayer reflective film 205 (film thickness = 1)
0 μm or less), a polyimide (PI) alignment film 206 is formed in this order, and a rubbing process is performed on the surface of the polyimide alignment film 206. The two pieces thus produced are bonded so as to be parallel to each other.
08 (for example, manufactured by Merck & Co.) to produce the wavelength selection filter 10.

Next, the operation of the Fabry-Perot etalon resonator 20 will be described. The selection wavelength of the wavelength selection filter 10 (that is, the resonance wavelength λ1 in the optical path A) is proportional to the optical path length (= thickness × refractive index). Will also differ greatly.

The electric field of the driving means 30 (40) is
When applied to the 08 layer, the liquid crystal molecules at the center of the cell farther from the surface of the transparent substrate 203 inside the resonator 20 are more affected by the electric field, and the inner product of the director and the electric field vector is increased. Lean. And the twist which was uniform in the thickness direction concentrates on the cell central region where the anisotropy becomes small.

If the electric field applied to the liquid crystal material 208 layer is further increased, the transition region becomes narrower, so that the refractive index felt by extraordinary light (extraordinary refractive index ne) can be reduced, and the resonance wavelength λ1 in the optical path A of the filter becomes shorter. It changes to the wavelength side.
In the wavelength selection filter 10 having the structure and function as described above, the transmittance = 60 to 70%, the finesse =
9.4, tuning width = 14 [nm] (however, applied voltage ≧ 3.
5 [Vrms]) and the polarization dependence = 3 [nm] (provided that the applied voltage ≧ 3.5 [Vrms]).

Next, an embodiment of the driving means 30 will be described with reference to the drawings. FIG. 2 is a circuit diagram for explaining a first embodiment of a drive circuit used in the wavelength selection filter 10 of FIG. The driving means 30 includes an inductive element 306 and an AC power supply 302 as shown in FIG.

Fabry-Perot etalon resonator 20
The electrical equivalent circuit of the capacitance (unit: [pF]) is a series circuit of a capacitive element (C [F]) 308 and a resistive element (R [Ω]) 304 as shown in FIG. Can be expressed. The inductive element (L 1 [H]) 306 is connected in parallel to the electrical equivalent circuit of the Fabry-Perot etalon resonator 20 and has a resistance (unit) of the Fabry-Perot etalon resonator 20. Has a function of forming an electrical resonance system with [Ω]) and capacitance (unit is [F]). Specifically, it is desirable to be realized by a coil.

When the capacitance of the Fabry-Perot etalon-type resonator 20 fluctuates due to a temperature change or the like, the AC power supply 302 applies an applied voltage (unit: [ Vrms]) as a wavelength selection voltage.

Specifically, it is desirable that the waveform of the applied voltage output from AC power supply 402 be a sine waveform or a pulse waveform. Next, the operation of the driving means 30 will be described with reference to the drawings. FIG. 3 is a graph for explaining the resonance wavelength λ 1 -capacitance characteristic in the wavelength selection filter 10 of FIG. FIG. 4 is a graph for explaining the resonance characteristics of the wavelength selection filter 10 of FIG. FIG.
2 is a graph for explaining an applied voltage-capacitance characteristic in the wavelength selection filter 10 of FIG.

Fabry-Perot etalon resonator 20
Has a capacitance of 152 as shown in the resonance characteristics of FIG.
1530 in the range of [pF] to 160 [pF].
Since the resonance wavelength λ1 in the range of [nm] to 1560 [nm] has a substantially linear function, the resonance wavelength λ1 is uniquely maintained at a constant value by controlling the capacitance to a constant value. be able to.

Fabry-Perot etalon resonator 20
As shown in the applied voltage-capacitance characteristic in FIG. 4, the applied voltage and the capacitance applied to the EMI have a resonance characteristic in which the applied voltage value has a peak at a certain capacitance. The driving means 30
A wavelength selection voltage (applied voltage) for keeping the capacitance of the Fabry-Perot etalon type resonator 20 constant is applied to the etalon medium 208 between the electrodes for controlling the refractive index, and the resonance wavelength λ
The control that keeps 1 constant is executed.

Specifically, the driving means 30
When the capacitance of the Perot etalon type resonator 20 fluctuates due to a temperature change or the like, in the inductive resonance region in the resonance characteristics of the electric resonance system (see the use region indicated by an arrow in FIG. 4). The control is performed to select the applied voltage and apply it as a wavelength selection voltage to keep the resonance wavelength λ1 constant.

For example, when the capacitance of the Fabry-Perot etalon resonator 20 becomes small (that is, C [p
F] is reduced to C-ΔC [pF]), and as shown in the resonance characteristic of FIG. 4, the applied voltage of the driving means 30 is V1 [V
rms] (> V2 [Vrms]). When the applied voltage increases to V1 (> V2), as shown in the applied voltage-capacitance characteristics in FIG. 5, a force (that is, a negative force) at which the capacitance of the Fabry-Perot etalon type resonator 20 increases. (The amount of feedback) acts to return to the original state (that is, C
-Return from C to C).

For the same reason, when the capacitance of the Fabry-Perot etalon type resonator 20 is increased (that is,
When C is increased to C + ΔC [pF]), the applied voltage of the driving means 30 is V2 (> V
Decreases to 1). As the applied voltage decreases to V2, FIG.
As shown in the applied voltage-capacitance characteristics, a force (that is, a negative feedback amount) that reduces the capacitance of the Fabry-Perot etalon type resonator 20 acts to return to the original state (that is, C + ΔC). Back to C).

As described above, according to the driving means 30 of the first embodiment, by providing such an inductive element 306 in the driving means 30, the parallel plate structure in the etalon structure can be changed with respect to temperature change. Without maintaining the optical precision accurately, the temperature of the resonance wavelength λ1 in the Fabry-Perot etalon resonator 20 can be stabilized with a simple circuit configuration.

That is, the control of the wavelength selection voltage is performed in accordance with the resonance characteristics of the Fabry-Perot etalon resonator 20 based on the capacitance of the Fabry-Perot etalon resonator 20 and the inductive element 306. , The thermal expansion and thermal contraction of the birefringent etalon medium 208 and the spacer 207 in the etalon structure, or the resonance length (optical path length nd1) between the dielectric reflective films 205 due to such thermal expansion and thermal contraction. The change (thermal expansion or thermal contraction) can be compensated for with a simple circuit configuration, and the effect that the temperature stabilization of the resonance wavelength λ1 in the Fabry-Perot etalon resonator 20 can be realized with a simple circuit configuration is achieved. Play. Specifically, the resonance length (that is, resonance length (optical path length nd1)) between the dielectric reflective films 205 changes due to thermal expansion and thermal contraction of the birefringent etalon medium 208, the spacer 207, and the like ( In other words, when it expands and contracts, the resonance wavelength λ
Depends on the fact that the wavelength selection voltage can be controlled with a simple circuit configuration so as to compensate for 1 so that the selected state of one resonance wavelength λ1 can be maintained stably (temperature stability of the resonance wavelength λ1 can be maintained). To play.

Further, since the birefringent etalon medium 208 has a temperature dependence of the refractive index (ordinary refractive index no and extraordinary refractive index ne), the resonance length (optical path length nd1) has the same temperature dependence. Even in the case of having the inductive property, the capacitance of the Fabry-Perot etalon type resonator 20 and the inductive element 30
6 and Fabry-Perot etalon resonator 20
Since the wavelength selection voltage can be controlled with a simple circuit configuration in accordance with the resonance characteristics of (1) and (2), there is an effect that a wavelength selection characteristic (wavelength selection characteristic having temperature independence) that is stable against a temperature change can be realized.

Next, the wavelength selection filter 10 will be described with reference to the drawings.
An embodiment of the second embodiment will be described. FIG. 6 is an arrangement diagram for explaining a second embodiment of the wavelength selection filter 10 of the present invention. Note that the same parts as those already described in the first embodiment are denoted by the same reference numerals, and redundant description will be omitted.

The Fabry-Perot etalon resonator 20
The electrical equivalent circuit of the capacitance (unit: [pF]) is a series circuit of a capacitive element (C [F]) 308 and a resistance element (R [Ω]) 304 as shown in FIG. Can be expressed. The driving means 40 has a variable capacitance element 404, a variable resistance element 402, an inductive element 306, a transformer 406, and an AC power supply 302.

The variable capacitive element 404 shown in FIG. 6 is connected in parallel to the electrical equivalent circuit of the Fabry-Perot etalon resonator 20 and is connected to the Fabry-Perot etalon.
It is a capacitive electronic element that forms an electrical resonance system with the electrical equivalent circuit of the etalon-type resonator 20, the variable resistance element 402, and the inductive element 306, and its capacitance (capacitance) (unit: [F] ) Can be changed from outside at any time. Specifically, it is desirable to realize this by a capacitor (variable capacitance = Cv).

By changing the capacitance value of the variable capacitance element 404, the capacitance of the Fabry-Perot etalon type resonator 20 can be selected. Further, as will be described later, by controlling the variable capacitance Cv of the variable capacitive element 404, it is possible to control to keep the capacitance of the Fabry-Perot etalon resonator 20 constant.

The variable resistance element 402 shown in FIG. 6 is connected in parallel to the electrical equivalent circuit of the Fabry-Perot etalon type resonator 20 and is electrically connected to the Fabry-Perot etalon type resonator 20. An electronic element that forms an electrical resonance system together with the equivalent circuit, the variable capacitive element 404, and the inductive element 306, and has a configuration in which the resistance can be changed from the outside at any time. Specifically, it is desirable to realize this using a resistive element (variable resistance = Rv).

By changing the resistance value of the variable resistance element 402, the resonance sharpness of the electric resonance system can be selected, so that the slope of the applied voltage-capacitance characteristic can be adjusted. In addition, as a result of being able to adjust the slope of the applied voltage-capacitance characteristic, it is possible to adjust the accuracy of the capacitance of the variable capacitance element 404.

Further, the variable resistance R of the variable resistance element 402
By controlling v, the resonance sharpness of the electric resonance system shown in the resonance characteristic of FIG. 4 can be adjusted, and as a result, the capacitance of the Fabry-Perot etalon type resonator 20 becomes temperature-dependent. It becomes possible to adjust stability against changes and the like and the above-described amount of negative feedback.

The inductive element 306 shown in FIG. 6 is connected in parallel to an electrical equivalent circuit of the Fabry-Perot etalon type resonator 20 and is electrically connected to the Fabry-Perot etalon type resonator 20. Equivalent circuit and variable capacitive element 4
This is an inductive electronic element that forms an electrical resonance system together with the variable resistance element 04 and the variable resistance element 402, and has a configuration in which its inductance (unit: [H]) can be changed from the outside at any time.
Specifically, it is desirable to be realized by a coil.

The transformer 406 shown in FIG. 6 has a predetermined inductance (L 2 [H]), and is connected in series with the inductive element 306. Applying the voltage applied to the AC power supply 302 to the Fabry-Perot etalon type resonator 20 without disturbing the resonance characteristics of the electric resonance system by electromagnetically coupling with the electric resonance system via the transformer 406 Will be able to

The AC power supply 302 is electromagnetically coupled to the electric resonance system via the transformer 406, and the capacitance of the electric equivalent circuit of the Fabry-Perot etalon type resonator 20 is changed due to a temperature change or the like. This is an AC signal source for applying an applied voltage according to the resonance characteristics of the electrical resonance system as a wavelength selection voltage to the electrical equivalent circuit of the Fabry-Perot etalon type resonator 20 when it fluctuates.

Next, the driving means 4 will be described with reference to FIGS.
The operation of 0 will be described. The capacitance of the Fabry-Perot etalon resonator 20 is, as shown in the resonance characteristics of FIG.
In the range of 152 [pF] to 160 [pF], 15
Resonance wavelength λ1 in the range of 30 [nm] to 1560 [nm]
, The resonance wavelength λ1 can be uniquely maintained at a constant value by controlling the capacitance to a constant value.

Fabry-Perot etalon resonator 20
As shown in the applied voltage-capacitance characteristics in FIG. 5, the applied voltage and the capacitance applied to the IGBT have a resonance characteristic in which the applied voltage peaks at a certain capacitance. The driving means 40
A wavelength selection voltage (applied voltage) for keeping the capacitance of the Fabry-Perot etalon type resonator 20 constant is applied to the etalon medium 208 between the electrodes for controlling the refractive index, and the resonance wavelength λ
The control that keeps 1 constant is executed.

Specifically, in the driving means 40, when the capacitance of the Fabry-Perot etalon type resonator 20 fluctuates due to a temperature change or the like, the variable capacitance element 40
By adjusting the capacitance value Cv of FIG. 4, the applied voltage selected within the inductive resonance region in the resonance characteristics of the electric resonance system (see the use region indicated by the arrow in FIG. 4) is applied as the wavelength selection voltage. Control is performed to keep the resonance wavelength λ1 constant.

For example, when the capacitance of the Fabry-Perot etalon type resonator 20 becomes small (that is, C [p
F] is reduced to C-ΔC [pF]), the voltage applied to the driving means 40 is adjusted to V1 by adjusting the capacitance value Cv of the variable capacitance element 404 as shown in the resonance characteristics of FIG.
Control to increase to [Vrms] (> V2 [Vrms]) is performed. When the control for increasing the applied voltage to V1 (> V2) is executed, as shown in the applied voltage-capacitance characteristics in FIG. 5, the Fabry-Perot etalon type resonator 2
A force (that is, a negative feedback amount) at which the electrostatic capacitance of 0 increases acts to return to the original state (that is, return from C-ΔC to C).

For the same purpose, when the capacitance of the Fabry-Perot etalon type resonator 20 is increased (that is,
When C increases to C + ΔC [pF]), the voltage applied to the driving means 40 is adjusted to V2 by adjusting the capacitance value Cv of the variable capacitance element 404 as shown in the resonance characteristics of FIG.
(> V1). When the control for reducing the applied voltage to V2 is executed, as shown in the applied voltage-capacitance characteristics in FIG.
A force that reduces the capacitance of the etalon-type resonator 20 (that is, the amount of negative feedback) acts to return to the original state (that is, return from C + ΔC to C).

As described above, Fabry-Perot
For the electrical equivalent circuit of the etalon resonator 20, the variable capacitance element 404, the variable resistance element 402, and the inductive element 3
In addition, by providing an electric resonance system capable of changing the resonance characteristics with a simple circuit configuration using the driving circuit 40, and controlling the resonance system using the driving means 40, the parallel plate structure in the etalon structure can be changed with respect to temperature change. Without maintaining optical precision, the Fabry-Perot etalon resonator 20
In this case, the temperature of the resonance wavelength λ1 can be more easily stabilized.

By changing the capacitance value of the variable capacitance element 404, the capacitance of the Fabry-Perot etalon type resonator 20 can be selected. Further, by changing the resistance value of the variable resistance element 402, the resonance sharpness of the electric resonance system can be selected, and as a result, the applied voltage −
The inclination of the capacitance characteristic can be adjusted. In addition, as a result of being able to adjust the slope of the applied voltage-capacitance characteristic, it is possible to adjust the accuracy of the capacitance of the variable capacitance element 404.

Further, by applying electromagnetic coupling to the electric resonance system via the transformer 406, the voltage applied to the AC power source 302 can be changed without disturbing the resonance characteristics of the electric resonance system by the Fabry-Perot etalon type resonance. Can be given to the vessel 20. That is, according to the resonance characteristics of the Fabry-Perot etalon resonator 20 based on the capacitance of the Fabry-Perot etalon resonator 20, the variable capacitance element 404, the variable resistance element 402, and the inductive element 306,
By controlling the wavelength selection voltage, the birefringent etalon medium 208 and the spacer 20 in the etalon structure are controlled.
7 or a resonance length (optical path length nd) between the dielectric reflection films 205 due to such thermal expansion or thermal contraction.
1) (thermal expansion and thermal contraction) can be compensated for with a simple circuit configuration, and the temperature stabilization of the resonance wavelength λ1 in the Fabry-Perot etalon resonator 20 can be realized with a simple circuit configuration. The effect that can be performed.

Specifically, the birefringent etalon medium 208
Length (that is, resonance length (optical path length nd) between dielectric reflection films 205 due to thermal expansion and thermal contraction of spacers 207 and the like.
1)) changes (that is, expands or contracts), the wavelength selection voltage can be controlled with a simple circuit configuration so as to compensate for the resonance wavelength λ1 with respect to these changes. Can be stably maintained (the temperature stability of the resonance wavelength λ1 can be maintained).

Further, since the birefringent etalon medium 208 has temperature dependence of the refractive index (ordinary refractive index no and extraordinary refractive index ne), the resonance length (optical path length nd1) has the same temperature dependence. Even when the resonator has a characteristic, the Fabry-Perot etalon resonator 20 based on the capacitance of the Fabry-Perot etalon resonator 20, the variable capacitance element 404, the variable resistance element 402, and the inductive element 306 is used. Since the wavelength selection voltage can be controlled with a simple circuit configuration in accordance with the resonance characteristics of (1) and (2), there is an effect that a wavelength selection characteristic (wavelength selection characteristic having temperature independence) that is stable against a temperature change can be realized.

As described above, according to the present wavelength selection filter 10, by providing such a driving means 30 (40), the parallel plate structure in the etalon structure can be formed with optical accuracy with respect to temperature change. There is an effect that the temperature of the resonance wavelength λ1 in the Fabry-Perot etalon resonator 20 can be stabilized without maintaining it accurately.

That is, by controlling the wavelength selection voltage so as to keep the capacitance of the Fabry-Perot etalon type resonator 20 constant, the birefringent etalon medium 208 and the spacer 207 in the etalon structure are controlled. It is possible to compensate for thermal expansion or thermal contraction or a change (thermal expansion or thermal contraction) in the resonance length (optical path length nd1) between the dielectric reflective films 205 due to such thermal expansion or thermal contraction. There is an effect that the temperature of the resonance wavelength λ1 in the Perot etalon type resonator 20 can be stabilized.

More specifically, the birefringent etalon medium 208
Length (that is, resonance length (optical path length nd) between dielectric reflection films 205 due to thermal expansion and thermal contraction of spacers 207 and the like.
1)) changes (that is, expands or contracts), and the selection state of one resonance wavelength λ1 is stably maintained by controlling the wavelength selection voltage so as to compensate the resonance wavelength λ1 for these changes. (Maintaining the temperature stability of the resonance wavelength λ1).

Further, since the birefringent etalon medium 208 has temperature dependence of the refractive index (ordinary refractive index no and extraordinary refractive index ne), the resonance length (optical path length nd1) has the same temperature dependence. Even in the case of having a characteristic, by controlling the wavelength selection voltage so as to keep the capacitance of the Fabry-Perot etalon type resonator 20 constant, the wavelength selection characteristic ( This has the effect of realizing a wavelength selection characteristic having temperature independence.

Next, an embodiment of a resonance wavelength selection control method used in the above-described wavelength selection filter 10 will be described.
The same portions as those already described are denoted by the same reference numerals, and duplicate description will be omitted. The present resonance wavelength selection control method uses the Fabry-Perot etalon type resonator 20.
Is applied to the etalon medium 208 between the electrodes for controlling the refractive index by applying a wavelength selection voltage for keeping the capacitance of
A resonance wavelength selecting step of executing control for keeping 1 constant.

In the resonance wavelength selection step, when the capacitance fluctuates due to a temperature change or the like, an applied voltage is selected within the inductive resonance region (see FIG. 4) in the resonance characteristics of the electric resonance system. It is possible to execute control for maintaining the resonance wavelength λ1 constant by applying the same as a wavelength selection voltage.

By providing such a resonance wavelength selecting step, the Fabry-Perot etalon type resonator 20 can be used without maintaining the parallel plate structure in the etalon structure accurately with optical accuracy against a temperature change. This has the effect of stabilizing the temperature of the resonance wavelength λ1 more easily.

Furthermore, as a result of obtaining a negative feedback effect using an applied voltage with respect to a change in the capacitance of the Fabry-Perot etalon type resonator 20, the parallel plate structure in the etalon structure is optically affected by a change in temperature. There is an effect that the temperature stabilization of the resonance wavelength λ1 in the Fabry-Perot etalon-type resonator 20 can be more easily achieved without maintaining the accuracy accurately.

That is, according to the resonance characteristics of the Fabry-Perot etalon resonator 20 based on the resonance wavelength selection step,
By controlling the wavelength selection voltage, the birefringent etalon medium 208 and the spacer 20 in the etalon structure are controlled.
7 or a resonance length (optical path length nd) between the dielectric reflection films 205 due to such thermal expansion or thermal contraction.
1) (thermal expansion and thermal contraction) can be compensated for with a simple circuit configuration, and the temperature stabilization of the resonance wavelength λ1 in the Fabry-Perot etalon resonator 20 can be realized with a simple circuit configuration. The effect that can be performed.

Specifically, the birefringent etalon medium 208
Length (that is, resonance length (optical path length nd) between dielectric reflection films 205 due to thermal expansion and thermal contraction of spacers 207 and the like.
1)) changes (that is, expands or contracts), the wavelength selection voltage can be controlled with a simple circuit configuration so as to compensate for the resonance wavelength λ1 with respect to these changes. Can be stably maintained (the temperature stability of the resonance wavelength λ1 can be maintained).

Furthermore, the resonance length (optical path length nd1) has the same temperature dependence due to the temperature dependence of the refractive index of the birefringent etalon medium 208 (ordinary refractive index no and extraordinary refractive index ne). Even if it has a characteristic, the wavelength selection voltage can be controlled with a simple circuit configuration in accordance with the resonance characteristics based on the resonance wavelength selection step, so that the wavelength selection characteristics (which have temperature independence Wavelength selection characteristics)
Is achieved.

[0105]

According to the first aspect of the present invention, by providing such a driving means, the parallel plate structure in the etalon structure is not accurately maintained with optical accuracy against a temperature change. In addition, there is an effect that the temperature of the resonance wavelength λ1 in the Fabry-Perot etalon resonator can be stabilized.

That is, by controlling the wavelength selection voltage so as to keep the capacitance of the Fabry-Perot etalon type resonator constant, the thermal expansion and the expansion of the birefringent etalon medium and spacers in the etalon structure can be prevented. It is possible to compensate for thermal shrinkage or a change (thermal expansion or shrinkage) in the resonance length (optical path length nd1) between the dielectric reflective films due to such thermal expansion or thermal shrinkage, and it is possible to compensate for the Fabry-Perot etalon type. This has the effect of stabilizing the temperature of the resonance wavelength λ1 in the resonator.

Specifically, the resonance length (that is, the resonance length (optical path length nd1)) between the dielectric reflective films changes due to the thermal expansion and contraction of the birefringent etalon medium and the spacer. In other words, when it expands and contracts, the resonance wavelength λ
By controlling the wavelength selection voltage to compensate for 1, there is an effect that the selected state of one resonance wavelength λ1 can be stably maintained (temperature stability of the resonance wavelength λ1 can be maintained).

Furthermore, the resonance length (optical path length nd1) has the same temperature dependence due to the temperature dependence of the refractive index (ordinary refractive index no and extraordinary refractive index ne) of the birefringent etalon medium. Even in the case of having a wavelength selection characteristic, by controlling the wavelength selection voltage so as to keep the capacitance of the Fabry-Perot etalon type resonator constant, stable wavelength selection characteristics against temperature changes (temperatureless Dependent wavelength selection characteristics)
Is achieved.

According to the invention described in claim 2, according to claim 1
In addition to the effects described in the above paragraph, by providing such an inductive element in the driving means, it is possible to maintain the parallel plate structure in the etalon structure accurately with optical accuracy with respect to temperature changes without using the Fabry-Perot structure. The temperature of the resonance wavelength λ1 in the etalon resonator can be stabilized with a simple circuit configuration.

That is, by controlling the wavelength selection voltage according to the resonance characteristics of the Fabry-Perot etalon resonator based on the capacitance of the Fabry-Perot etalon resonator and the inductive element, Thermal expansion or thermal contraction of the birefringent etalon medium or spacer in the etalon structure, or change in the resonance length (optical path length nd1) between the dielectric reflective films due to such thermal expansion or thermal contraction (thermal expansion or thermal expansion) Shrinkage) can be compensated for with a simple circuit configuration, and there is an effect that temperature stabilization of the resonance wavelength λ1 in the Fabry-Perot etalon resonator can be realized with a simple circuit configuration.

More specifically, the resonance length (that is, the resonance length (optical path length nd1)) between the dielectric reflection films changes due to the thermal expansion and contraction of the birefringent etalon medium and the spacer. In other words, when it expands and contracts, the resonance wavelength λ
Depends on the fact that the wavelength selection voltage can be controlled with a simple circuit configuration so as to compensate for 1 so that the selected state of one resonance wavelength λ1 can be maintained stably (temperature stability of the resonance wavelength λ1 can be maintained). To play.

Furthermore, the resonance length (optical path length nd1) has the same temperature dependence due to the temperature dependence of the refractive index of the birefringent etalon medium (ordinary refractive index no and extraordinary refractive index ne). Even in the case of having, according to the resonance characteristics of the Fabry-Perot etalon type resonator based on the capacitance and the inductive element of the Fabry-Perot etalon type resonator,
Since the wavelength selection voltage can be controlled with a simple circuit configuration, there is an effect that a wavelength selection characteristic (wavelength selection characteristic having temperature independence) that is stable against a temperature change can be realized.

According to the invention described in claim 3, according to claim 2
It has the same effect as. According to the fourth aspect of the present invention, in addition to the effect of the first aspect, the variable capacitance element, the variable resistance element, and the inductive element with respect to the capacitance of the Fabry-Perot etalon resonator are provided. By providing an electrical resonance system that can change the resonance characteristics with a simple circuit configuration using the etalon structure, the parallel plate structure in the etalon structure can be accurately maintained without optical accuracy with respect to temperature changes. The effect that the temperature stabilization of the resonance wavelength λ1 in the Perot etalon type resonator can be more easily realized.

By changing the capacitance value of the variable capacitance element, the capacitance of the Fabry-Perot etalon resonator can be selected. Further, by changing the resistance value of the variable resistance element, the resonance sharpness of the electric resonance system can be selected, so that the slope of the applied voltage-capacitance characteristic can be adjusted. In addition, as a result of being able to adjust the slope of the applied voltage-capacitance characteristic, the accuracy of the capacitance of the variable capacitive element can be adjusted.

Further, by applying electromagnetic coupling to the electric resonance system via a transformer, the applied voltage of the AC power supply can be applied to the Fabry-Perot etalon type resonator without disturbing the resonance characteristics of the electric resonance system. Will be able to give. That is, control of the wavelength selection voltage is performed according to the resonance characteristics of the Fabry-Perot etalon resonator based on the capacitance of the Fabry-Perot etalon resonator, the variable capacitance element, the variable resistance element, and the inductive element. Depending on what you do,
Thermal expansion or thermal contraction of the birefringent etalon medium or spacer in the etalon structure, or change in the resonance length (optical path length nd1) between the dielectric reflective films due to such thermal expansion or thermal contraction (thermal expansion or thermal expansion) Shrinkage) can be compensated for with a simple circuit configuration, and there is an effect that temperature stabilization of the resonance wavelength λ1 in the Fabry-Perot etalon resonator can be realized with a simple circuit configuration.

More specifically, the resonance length (that is, the resonance length (optical path length nd1)) between the dielectric reflection films changes due to the thermal expansion and contraction of the birefringent etalon medium and the spacer. In other words, when it expands and contracts, the resonance wavelength λ
Depends on the fact that the wavelength selection voltage can be controlled with a simple circuit configuration so as to compensate for 1 so that the selected state of one resonance wavelength λ1 can be maintained stably (temperature stability of the resonance wavelength λ1 can be maintained). To play.

Furthermore, the resonance length (optical path length nd1) has the same temperature dependence due to the temperature dependence of the birefringent etalon medium refractive index (ordinary refractive index no and extraordinary refractive index ne). Even if it has, according to the resonance characteristics of the Fabry-Perot etalon resonator based on the capacitance of the Fabry-Perot etalon resonator, the variable capacitance element, the variable resistance element, and the inductive element, Since the selection voltage can be controlled with a simple circuit configuration, there is an effect that a wavelength selection characteristic that is stable against a temperature change (a wavelength selection characteristic having temperature independence) can be realized.

According to the invention set forth in claim 5, according to claim 4,
In addition to the effects described in the above, the capacitance of the Fabry-Perot etalon type resonator can be selected by changing the capacitance of the variable capacitive element. According to the invention described in claim 6, in addition to the effect described in claim 4 or 5, the resonance sharpness of the electric resonance system can be selected by changing the resistance value of the variable resistance element. As a result, the slope of the applied voltage-capacitance characteristic can be adjusted. In addition, as a result of being able to adjust the slope of the applied voltage-capacitance characteristic, the accuracy of the capacitance of the variable capacitive element can be adjusted.

According to the invention of claim 7, according to claim 4,
The same effects as the effects described in 1 to 6 are achieved. According to the eighth aspect of the invention, in addition to the effects of the fourth to seventh aspects, the resonance characteristic of the electric resonance system is obtained by electromagnetically coupling to the electric resonance system via the transformer. Voltage can be applied to the Fabry-Perot etalon resonator without disturbing the power supply.

According to the ninth aspect of the present invention, the first aspect is provided.
In addition to the effects described in (8) to (8), by providing a resonance wavelength selecting step, the Fabry-Perot etalon type can be used without maintaining the parallel plate structure in the etalon structure accurately with optical precision against a temperature change. This has the effect of stabilizing the temperature of the resonance wavelength λ1 in the resonator more easily.

That is, by controlling the wavelength selection voltage in accordance with the resonance characteristics of the Fabry-Perot etalon type resonator based on the resonance wavelength selection step, the heat of the birefringent etalon medium and spacers in the etalon structure can be improved. It is possible to compensate for expansion (thermal expansion) or a change in the resonance length (optical path length nd1) between the dielectric reflective films (thermal expansion or thermal contraction) due to such thermal expansion or thermal contraction with a simple circuit configuration. Wavelength in a Fabry-Perot etalon resonator
This has the effect that the temperature can be stabilized with a simple circuit configuration.

More specifically, the resonance length (that is, the resonance length (optical path length nd1)) between the dielectric reflection films changes due to the thermal expansion and contraction of the birefringent etalon medium and the spacer. In other words, when it expands and contracts, the resonance wavelength λ
Depends on the fact that the wavelength selection voltage can be controlled with a simple circuit configuration so as to compensate for 1 so that the selected state of one resonance wavelength λ1 can be maintained stably (temperature stability of the resonance wavelength λ1 can be maintained). To play.

Further, since the refractive index of the birefringent etalon medium (ordinary refractive index no and extraordinary refractive index ne) has temperature dependence, the resonance length (optical path length nd1) has the same temperature dependence. Even in the case of having a wavelength selection characteristic, the wavelength selection voltage can be controlled with a simple circuit configuration in accordance with the resonance characteristics based on the resonance wavelength selection step, so that the wavelength selection characteristics (wavelength having temperature independence) (Selection characteristics).

According to the tenth aspect of the present invention, in addition to the effect of the ninth aspect, it is also possible to execute the resonance wavelength selecting step in the inductive resonance region in the resonance characteristics of the electric resonance system. Obtains a negative feedback effect using applied voltage for changes in the capacitance of Fabry-Perot etalon resonators. As a result, the parallel plate structure in the etalon structure is accurately maintained with optical accuracy against temperature changes. Without doing so, there is an effect that the temperature stabilization of the resonance wavelength λ1 in the Fabry-Perot etalon type resonator can be more easily realized.

That is, by performing negative feedback control of the wavelength selection voltage in accordance with the resonance characteristics in the inductive resonance region of the Fabry-Perot etalon resonator based on the resonance wavelength selection step, birefringence in the etalon structure is obtained. Thermal expansion and thermal contraction of the conductive etalon medium and spacers, or a change (thermal expansion and thermal contraction) of the resonance length (optical path length nd1) between the dielectric reflective films caused by such thermal expansion and thermal contraction. Compensation can be made by the circuit configuration, and the temperature can be stabilized at the resonance wavelength λ1 in the Fabry-Perot etalon type resonator with the effect of being able to be realized with a simple circuit configuration.

Specifically, the resonance length (that is, the resonance length (optical path length nd1)) between the dielectric reflection films changes due to the thermal expansion and thermal contraction of the birefringent etalon medium, the spacer, and the like. In other words, when it expands and contracts, the resonance wavelength λ
Because the wavelength selection voltage can be controlled with a simple circuit configuration so that 1 is compensated for using the negative feedback effect, the selected state of one resonance wavelength λ1 is maintained stably (maintaining the temperature stability of the resonance wavelength λ1 ) Can be performed.

Further, since the birefringent etalon medium has a temperature dependence of the refractive index (ordinary refractive index no and extraordinary refractive index ne), the resonance length (optical path length nd1) has the same temperature dependence. Even in the case of having, the wavelength selection voltage can be negatively controlled with a simple circuit configuration in accordance with the resonance characteristics based on the resonance wavelength selection step within the inductive resonance region of the electric resonance system. Further, there is an effect that stable wavelength selection characteristics (wavelength selection characteristics having temperature independence) can be realized.

[Brief description of the drawings]

FIG. 1 is an arrangement diagram for explaining a basic configuration of a wavelength selection filter of the present invention.

FIG. 2 is a circuit diagram for explaining a first embodiment of a drive circuit used in the wavelength selection filter of FIG.

FIG. 3 is a graph for explaining a resonance wavelength-capacitance characteristic in the wavelength selection filter of FIG. 1;

FIG. 4 is a graph for explaining resonance characteristics of the wavelength selection filter of FIG. 1;

FIG. 5 is a graph for explaining applied voltage-capacitance characteristics in the wavelength selection filter of FIG. 1;

FIG. 6 is a layout diagram for explaining a second embodiment of the wavelength selection filter of the present invention.

FIG. 7 is a layout diagram for explaining a conventional wavelength selection filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Wavelength selection filter 11 Incident side optical fiber 11a Incident light (optical signal) 12 Outgoing optical fiber 12a Outgoing light (optical signal) 20 Fabry-Perot etalon type resonator 202 AR coat film 203 Transparent substrate 204A First transparent electrode 204B Second transparent electrode 205 Reflective film 206 Alignment film 207 Spacer 208 Etalon medium (liquid crystal material) 30 Driving means 302 AC power supply 304 Resistance element 306 Inductive element 308 Capacitive element 40 Driving means 402 Variable resistance element 404 Variable capacitance element 406 Trans d1 Resonance length between transparent electrodes in optical path A λ1 Resonant wavelength in optical path A

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasutaka Hasegawa 1500 Yazaki Sogyo Co., Ltd., Susono-shi, Shizuoka Prefecture (72) Inventor Takashi Kurokawa 3-2-1-2 Nishishinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Tetsuo Yoshizawa 3-2-1-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (10)

[Claims] 1. A wavelength selecting filter having a Fabry-Perot etalon type resonator capable of selecting a predetermined resonance wavelength by electrically controlling a refractive index of a birefringent etalon medium. A driving means for applying a wavelength selection voltage for maintaining the capacitance of the vessel constant to the etalon medium between the electrodes for controlling the refractive index to execute control for maintaining the resonance wavelength constant. Selection filter. 2. The driving unit, when connected to the Fabry-Perot etalon resonator, forms an electrical resonance system with the resistance and the capacitance of the Fabry-Perot etalon resonator. An inductive element, comprising: an AC power supply for applying an applied voltage according to a resonance characteristic of the electric resonance system as the wavelength selection voltage when the capacitance fluctuates. Item 2. The wavelength selection filter according to Item 1. 3. The electric resonance system according to claim 2, wherein the inductive element is connected to the Fabry-Perot etalon resonator in parallel with the electric resonance system. Wavelength selection filter. 4. The driving means, when connected to the Fabry-Perot etalon resonator, controls the electric resonance system together with the resistance and the capacitance of the Fabry-Perot etalon resonator. A variable capacitive element capable of changing a capacitance to be formed; and the electric capacity together with the resistance and the capacitance of the Fabry-Perot etalon resonator connected to the Fabry-Perot etalon resonator. A variable resistance element capable of changing the amount of resistance forming a resonance system, and connected to the Fabry-Perot etalon type resonator while being connected to the Fabry-Perot etalon type resonator, together with the resistance and the capacitance of the Fabry-Perot etalon type resonator. An inductive element capable of changing an inductance forming an electric resonance system; and a transformer having a predetermined inductance. And an AC power supply for applying an applied voltage according to a resonance characteristic of the electric resonance system as the wavelength selection voltage when the capacitance fluctuates. The wavelength selection filter according to claim 1. 5. The variable capacitive element according to claim 1, wherein:
While connected in parallel to a Perot etalon resonator,
The wavelength selection filter according to claim 4, wherein the electrical resonance system is formed. 6. The electric resistance system according to claim 4, wherein the variable resistance element forms the electric resonance system in a state where it is connected in parallel to the Fabry-Perot etalon resonator. Wavelength selection filter. 7. The electric resonance system according to claim 4, wherein the inductive element is connected to the Fabry-Perot etalon resonator in parallel to form the electric resonance system. Wavelength selection filter. 8. The wavelength selector according to claim 4, wherein the transformer is electromagnetically coupled to the electric resonance system while being connected in series with the inductive element. filter. 9. The wavelength selection voltage for maintaining the capacitance of the Fabry-Perot etalon resonator constant is applied to an etalon medium between electrodes for controlling the refractive index to maintain the resonance wavelength constant. The resonance wavelength selection control method used for the wavelength selection filter according to claim 1, further comprising a resonance wavelength selection step of performing control. 10. When the capacitance fluctuates, the applied voltage is selected within the inductive resonance region in the resonance characteristics of the electric resonance system and applied as the wavelength selection voltage to keep the resonance wavelength constant. The resonance wavelength selection control method according to claim 9, further comprising a resonance wavelength selection step of executing control to hold.