JPH0215228A - Optical fiber type fabry-perot resonator - Google Patents

Abstract

PURPOSE:To obtain high finesse and to easily make a frequency sweep with a piezoelectric force by providing a piezoelectric element, an optical fiber which is fixed to the piezoelectric element so that the electric field application direction of the piezoelectric element and the axial direction of the fiber are parallel to each other, and multi- layered reflecting mirrors which are arranged on both end surface of the optical fiber. CONSTITUTION:A groove 12 whose diameter is nearly equal to the diameter of the optical fiber 13 is formed by dicing from an end part of dummy piezoelectric ceramic 11a (11b) to an end part of ceramic 11b (11a) through the laminate type piezoelectric element 10, and fixed with an epoxy-based adhesive EA. Then both ends are polished together with the ceramic 11a and ceramic 11b so that the fiber 13 has specific length and then multi-layered reflecting films 14a and 14b which have constant transmissivity at specific wavelength are formed by vapor deposition. When respective electrodes T of the optical fiber type Fabry-Perot resonator are applied with a voltage from a signal generator 15, an electric field is applied in parallel to the axial direction of the fiber 13 to cause strain by piezoelectric effect, so that the length of the fiber 13 increases and the length of the resonator also increases. For the purpose, the applied voltage is varied to obtain desired frequency intervals easily and stably with small electric power.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to the structure of a swept type optical fiber type Fabry-Perot resonator whose resonator length changes depending on an applied voltage and which makes the wavelength of transmitted light variable. It is.

(Prior Art) A conventional optical fiber type Fabry-Perot resonator is designed as follows. First, the finesse f indicating the performance of the Fabry-Perot resonator is expressed by the following equation, where R is the reflectance of the reflecting mirror.

f-πF/2...(1)F
=4R/ (1-R) 2...(2)
The frequency interval Δf of the Fabry-Perot resonator is Δf=V/
2L...Represented by (3).

Here, ■ is the speed of light in the optical fiber, and L is the length of the optical fiber.

In the above, for example, in order to set the finesse f to 100, the reflectance R must be set to 96.7%.

Also, the speed of light in an optical fiber at a wavelength of 1.30 μm V
is 2.0078 x 101-m/see, so when the frequency interval Δf is 10 GHz, the optical fiber length is 10.039+nm. Therefore, the frequency interval Δf
In order to control the frequency on the order of 10 GHz, it is necessary to configure the length of the Fabry-Perot resonator with micron precision.

However, it is extremely difficult to configure the length of an optical fiber type Fabry-Perot resonator with micron precision.

Conventionally, in order to solve this problem, as shown in FIG.
The glass plates 3a and 3b on which evaporated glass is bonded and fixed with adhesive EA, and the plate-shaped piezoelectric element 4 is attached to optical fiber 1 with adhesive EA.
In this configuration, the signal generator 5 applies a voltage to the plate-shaped piezoelectric element 4 to apply bending displacement, and the length of the optical fiber 1 is changed to obtain a desired frequency interval Δf.

(Problems to be Solved by the Invention) However, according to the optical fiber type Fabry-Perot resonator having the above configuration, the amount of displacement is small, so the sweep frequency cannot be increased, and there are two bonding positions. However, there were problems in that it lacked long-term stability and long-term operation could not be guaranteed.

Furthermore, when connecting optical fibers to both ends of an optical fiber type Fabry-Perot resonator, since both end surfaces are reflective surfaces, it is difficult to find the position of the core of the optical fiber of the Fabry-Perot resonator. However, it is extremely difficult to align the optical fibers between the two and to fix the optical fibers between the two.

In view of the above problems, the object of claim (1) is to provide a swept type optical fiber type Fabry-Perot resonator that can increase the sweep frequency and operate stably for a long period of time with high efficiency with low power consumption. It's about doing.

In addition to the object of claim (1), the object of claim (2) is to provide a sweep type optical fiber that can operate stably for a long period of time and with low loss without performing connection processing between optical fibers. An object of the present invention is to provide a fiber type Fabry-Perot resonator.

(Means for Solving the Problems) In order to achieve the above object, in claim (1), a piezoelectric element is fixed to the piezoelectric element such that an electric field application direction of the piezoelectric element and a fiber axis direction are parallel to each other. optical fiber,
Multilayer film reflecting mirrors were arranged and fixed on both end faces of the optical fiber.

Further, in claim (2), a piezoelectric element, an optical fiber fixed to the piezoelectric element such that the electric field application direction of the piezoelectric element and the fiber axis direction are parallel to each other, and a predetermined interval between the optical fibers. It has two grooves formed perpendicular to the fiber axis and two multilayer film reflectors inserted and fixed in each groove.

(Function) According to claim (1), when a predetermined voltage is applied to the piezoelectric element, an electric field is applied in parallel to the fiber axis direction of the optical fiber, causing strain, and the length of the optical fiber is increased. That is, the optical fiber type Fabry-Perot resonator becomes longer. Therefore, by selecting various magnitudes of the applied voltage, the length of the optical fiber type Fabry-Perot resonator can be changed, and a desired frequency interval can be obtained.

According to claim (2), in addition to the effect of claim (1), the optical connection between the optical fiber of the Fabry-Perot resonator and the external optical fiber is automatically completed.

(Embodiment) FIG. 1 shows a first embodiment of a swept type optical fiber type Fabry-Perot resonator according to the present invention.
1 is a longitudinal side view thereof, and FIG. 1(b) is a sectional view taken in a direction perpendicular to the axis of the optical fiber. In the figure, 10 is a piezoelectric element 1
The piezoelectric element 10a is a laminated piezoelectric element in which ten 0a are stacked, and an electrode T is disposed between each piezoelectric element 10a so that an electric field is applied in the axial direction of an optical fiber 13, which will be described later. lla, ll
b is a dummy piezoelectric ceramic with no electrode, and a laminated piezoelectric element 10
are glued to both ends. Reference numeral 12 denotes a groove formed in a straight line across the laminated piezoelectric element 10 and the piezoelectric ceramics 11a and llb, and has a width approximately equal to the diameter of an optical fiber 13, which will be described later. 13 is the cutoff wavelength 1.12μm
A single mode optical fiber (hereinafter simply referred to as an optical fiber), 13a is the core of the optical fiber 13, 13b is the cladding of the optical fiber]3, the optical fiber 13 is inserted into the groove 12, and the groove 12 is filled with epoxy. It is fixed with adhesive EA. 14a and 14b are multilayer reflective mirrors with a transmittance of 0.5% at a wavelength of 1.307 zm, and are optical fibers] 3
It is formed by vapor deposition from both end faces of the piezoelectric ceramics 11a and llb to both end faces of each of the piezoelectric ceramics 11a and llb. 15 is electrode T
It is a signal generator that applies voltage to the

Next, a method for manufacturing an optical fiber type Fabry-Perot resonator having the above configuration and its operation will be explained.

First, a diameter that is approximately the same as the diameter of the optical fiber 13 is connected from the end of the dummy piezoelectric ceramic 11a, (1lb) to the end of the dummy piezoelectric ceramic 11b (lla) via the laminated piezoelectric element 10. A groove 12 is formed by dicing, and an optical fiber 13 is inserted into this groove 12 and fixed with an epoxy adhesive EA.

Next, both ends of the optical fiber 13 were connected to dummy piezoelectric ceramics 1 so that the length of the optical fiber 13 was 10.03 mm.
After polishing with 1a and llb, wavelength 1. ．． Multilayer film reflecting mirrors 14a, :l-4b having a transmittance of 0.5% at 30 μm are formed by vapor deposition to complete the fabrication.

Optical fiber type Fabry-Perot fabricated in this way
When a voltage is applied to each electrode T of the resonator by the signal generator] 5, an electric field is applied parallel to the axial direction of the optical fiber 13, causing distortion due to the piezoelectric effect, which causes the length of the optical fiber 13 to increase. , that is, the Fabry-Perot cavity length becomes longer.

Therefore, according to the embodiment of Mizui 1, by changing the magnitude of the voltage applied by the signal generator 15, various lengths of the optical fiber type Fabry-Perot resonator can be selected, and the desired frequency interval can be easily and stably set. Moreover, it can be obtained with low power consumption. In addition, the optical fiber] 3 is a laminated piezoelectric element 10
and a groove 12 formed across the piezoelectric ceramics 11a and llb.
Since it is fixed inside, stable operation is possible over a long period of time.

In fact, an optical fiber having the same structural parameters as the optical fiber 13 was connected to both ends of the Fabry-Perot resonator according to the embodiment of Mizui 1, with the axes aligned using a He-Ne laser, and a DFB semiconductor with a wavelength of 1.30 μm was connected. Laser 711
11, when the voltage applied to the electrode T by the signal generator 15 is zero, a finesse f of 300 can be obtained with a frequency interval Δf of 10 GHz, and a pruning loss of 0.2.
It was dB. In addition, the signal generator 15 applies ± to the electrode T.
As a result of applying a voltage of 100 μ, it was possible to obtain a frequency shift of ±2 MHz.

FIG. 3 is a longitudinal sectional side view showing a second embodiment of the optical fiber type Fabry-Perot resonator according to the present invention. The difference between the second embodiment and the first embodiment is that the optical fiber 1
3 and the end surfaces of the piezoelectric ceramics 11, a 1.1b, a multilayer reflective film is formed by vapor deposition.
Thin glass multilayer mirrors 16a and 16b having a transmittance of 0.5% at 0 μm and a thickness of 100 μm are bonded and fixed using an epoxy adhesive EA.

Optical fibers having the same structural parameters as the optical fiber 13 are connected to both ends of the optical fiber type Fabry-Perot resonator of the example of Sui-Tei 2 having such a configuration, with their axes aligned, and a DFB with a wavelength of 1.30 μm is connected. f with semiconductor laser
As a result of determining f1ll, if the voltage applied to the electrode T by the signal generator]5 is zero, the frequency interval Δf is 10 GHz.
The finesse f can be obtained as 100, and the insertion loss is 1.
, 1 dB.

Further, as a result of applying a voltage of ±100 V to the electrode T by the signal generator 15, as in the first embodiment, ±2 MH
We were able to obtain the frequency displacement of z.

FIG. 4 is a longitudinal sectional side view showing a third embodiment of the optical fiber type Fabry-Perot resonator according to the present invention. In the figure, 2
0 is a piezoelectric element 20a or a laminated piezoelectric element in which six piezoelectric elements 20a are laminated, and an electrode T is arranged between each piezoelectric element 2Oa so that an electric field is applied parallel to the axial direction of an optical fiber 23, which will be described later. There is. 2] a.

Reference numeral 21b denotes a dummy piezoelectric ceramic without an electrode, which is bonded to both ends of the laminated piezoelectric element 20. 22 is a laminated piezoelectric element 2
0 and piezoelectric ceramics 21a and 21b, and has a width approximately equal to the diameter of an optical fiber 13, which will be described later. 23 is a single mode optical fiber with a cutoff wavelength of 1.12 μm (hereinafter simply referred to as optical fiber);
23a is the core of the optical fiber 23, 23b is the optical fiber 2
The clad 23c of No. 3 is a coating for the optical fiber 23.

The portion of the optical fiber 23 from which the coating 23c is removed is the groove 2.
2, and is fixed in this groove 22 with an epoxy adhesive EA. 24a and 24b are piezoelectric ceramics 21a,
Grooves are formed in the optical fiber 21b at predetermined intervals, for example, 10 ynm, perpendicular to the axial direction of the optical fiber 23, and the width is 43 μm.
1 depth is set to 1 dragon. 25a and 25b are multilayer film reflecting mirrors made of thin glass having a transmittance of 0.5% at a wavelength of 1.30 μm and a thickness of 40 μm;
The reflecting surfaces are inserted into each of the grooves 24a and 24b so as to face each other, and fixed to the grooves 24a and 24b with an epoxy adhesive EA. 26 is a signal generator that applies a voltage to the electrode T.

Next, a method for manufacturing an optical fiber type Fabry-Perot resonator having the above configuration will be described.

First, the dummy piezoelectric ceramic 21b is passed from the end of the dummy piezoelectric ceramic 21a (21b) through the laminated piezoelectric element 20.
A groove 22 having a width approximately the same as the diameter of the optical fiber 23 is formed to reach the end of the optical fiber 23, and the coating 2 of the optical fiber 23 is formed.
The portion from which 3c has been removed (approximately the same length as the groove 22) is inserted into the groove 22 and fixed with an epoxy adhesive EA. At this time, both ends of the dummy piezoelectric ceramics 21a and 21b are coated.
A stepped portion is formed so that the optical fiber 23 with 23C attached thereto is fixed.

Next, using a special dicing device as shown in Figure 5 (see Tadao Saito, Junji Watanabe, “Micro Shape Processing,” 1959 Japan Society for Precision Engineering, preprint collection, 208 (October 1959)), a thin Sapphire blade 30 to air spindle 3
1 rotates at a high wind speed of 1300 rn/mjn, and the particle size is 0.24. cz m SiO2 abrasive grains 32
1a, 21b while spraying the grooves 24a with the numerical values and positional relationship described above.

24b. This makes the side surfaces of the grooves 24a and 24b nearly mirror-like. Next, the multilayer film reflecting mirror 25
grooves 24a and 25b so that their reflective surfaces face each other.
, 24b and fixed with epoxy adhesive EA to complete the fabrication. At the same time, the optical connection between the external optical fiber and the optical fiber of the optical fiber type Fabry-Perot resonator is achieved with high precision.

When a voltage is applied by the signal generator 26 to each electrode T of the optical fiber type Fabry-Perot resonator manufactured in this way, the optical fiber 23 is applied as in the first and second embodiments.
An electric field is applied parallel to the axial direction of the optical fiber 23, causing distortion due to the piezoelectric effect, which increases the length of the optical fiber 23.
That is, the Fabry-Perot resonator length becomes longer.

Therefore, according to the embodiment in bookcase 3, by changing the magnitude of the voltage applied by the signal generator 26, various Fabry-Perot resonator lengths can be selected, and the desired frequency interval can be easily and stably set. It can be obtained with low power, and there is no need to connect other optical fibers to both ends of the Fabry resonator, so there is no need for complicated labor.

In fact, the optical fiber type Fabry-Perot according to the third embodiment
The resonator has a diameter of 1.30 as in the first and second embodiments.
As a result of measurement using a μm DFB semiconductor laser, when the voltage applied to the electrode T by the signal generator 26 was zero, a finesse f of 85 could be obtained with a frequency interval Δf of 10 GHz. Moreover, the insertion loss was 0.6 dB. Further, as a result of applying a voltage of ±100 V to the electrode T by the signal generator 26, a frequency shift of ±2 MHz could be obtained.

FIG. 6 is a perspective view showing a fourth embodiment of an optical fiber type Fabry-Perot resonator according to the present invention.

In the embodiment of the bookcase 4, four optical fibers are used to form an array of the optical fiber type Fabry-Perot resonators according to the third embodiment. In the figure, 40 is a laminated piezoelectric element, 41a and 41b are dummy piezoelectric ceramics, and 42a to 4
2d is a groove for fixing an optical fiber, 43a to 43d are optical fibers, 44a and 44b are grooves, 4.5a and 45b are wavelength 1
．． A multilayer reflector made of thin glass having a transmittance of 0.5% at 30 μm and a thickness of 40 μm; 46 is a signal generator; T
are electrodes, and the structural parameters of the grooves 42a to 42d, 44a, 44b, and the optical fibers 43a to 43d are the same as in the third embodiment. Also, regarding the manufacturing method, the groove 4
The method is the same as that of the third embodiment except that the number of optical fibers 2a to 42d and the number of optical fibers 43a to 43d is different, so the description thereof will be omitted here.

Each optical fiber type Fabry-Perot resonator using each optical fiber 43a to 43d according to the embodiment of Section 4 has a diameter of 1.30 μm.
As a result of full determination using a DFB semiconductor laser of m, when the voltage applied to the electrode T by the signal generator 46 is zero,
The frequency interval Δf is 10 GHz±5 MHz, and the finesse f is 75.48. ko27.
95, insertion loss is 0.5dB and 0.8dB respectively
, 0.3dB, and 0.6dB.

Although the example in Section 4 describes an array configuration using four optical fibers, it is not limited to this.
Of course, it is also possible to construct a swept optical fiber type Fabry-Perot resonator using eight-core tape type optical fibers.

Further, in the first to fourth embodiments, the wavelength is 1.30.
Although we have explained the operation results at μm, the wavelength J, 5
Similar results can be obtained at 5 μm or at other wavelengths.

Furthermore, in the first to fourth embodiments, dummy piezoelectric ceramics] 1 are placed at both ends of the laminated piezoelectric elements 10 and 20.
a, ko, 1 b, 21 a, 2 l b.

41a and 41b are bonded together, but this serves as a reinforcing portion shrine, and is not limited to piezoelectric ceramics; for example, a glass substrate may of course be used. Furthermore, it goes without saying that the same effects as in each of the embodiments can be obtained without using these reinforcing members.

Further, in the first to fourth embodiments, the optical fiber 1
3. When bonding and fixing 23a to 23cl, 43a to 43d to the laminated piezoelectric element 10, 20.40, birefringence may occur due to the influence of lateral pressure, and side peaks may appear in the transmitted light in addition to the main peak. . To solve this problem, we used a polarization-maintaining optical fiber that already has large birefringence inside the optical fiber. As a result of using linearly polarized light as the incident light and injecting this linearly polarized light parallel to the main axis of polarization of the polarization-maintaining optical fiber, the optical fiber type Fabry-Perot
Only the main peak and no side peaks were observed in the output light from the resonator.

(Effects of the Invention) As explained above, according to claim (1), a piezoelectric element and an optical fiber fixed to the piezoelectric element such that the electric field application direction of the piezoelectric element and the fiber axis direction are parallel to each other. and,
Since the optical fiber is equipped with multilayer reflective mirrors arranged and fixed on both end faces, high finesse can be easily obtained.
Since the optical fiber is fixed to the piezoelectric element, there is an advantage that it is possible to provide a swept-type optical fiber-type Fabry-Perot resonator that can operate stably over a long period of time with low power for frequency sweeping.

] 7 According to claim (2), a piezoelectric element, an optical fiber fixed to the piezoelectric element such that the electric field application direction of the piezoelectric element is parallel to the fiber axis direction, and a predetermined In addition to the effect of claim (1), the present invention includes two grooves formed at right angles to the fiber axis at intervals and two multilayer film reflectors inserted and fixed in each groove. There is no need to connect external optical fibers to both ends, and extremely low loss can be achieved, and arrays can be constructed extremely easily and ultra-compact.

[Brief explanation of the drawing]

FIG. 1 shows a first embodiment of an optical fiber type Fabry-Perot resonator according to the present invention. FIG. 1(a) is a longitudinal side view, and FIG. 1(b) is a vertical side view of the optical fiber 2 is a configuration diagram of a conventional optical fiber type Fabry-Perot resonator, FIG. 3 is a vertical side view showing a second embodiment of the optical fiber type Fabry-Perot resonator according to the present invention, and FIG. 4 is a cross-sectional view. The third optical fiber type Fabry-Perot resonator according to the present invention
FIG. 5 is an explanatory diagram of a dicing apparatus, and FIG. 6 is a perspective view showing a fourth embodiment of an optical fiber type Fabry-Perot resonator according to the present invention. In the figure, 10, 20.40... laminated piezoelectric element, 11a
, llb, 21a, 21b, 41a, 41b...Dummy piezoelectric ceramic, 12, 22.42a-42d-...groove, 13.23.43a-43d--single mode optical fiber, 14a , 14b, 24a. 24 b, 44 a, 44 b---groove, 15
a, 15b. 45a, 45b...Multilayer film reflecting mirror, EA...Epoxy adhesive. Patent Applicant: Nippon Telegraph and Telephone Corporation Agent Patent Attorney: Yoshi Yoshi 1) Takashi Takashi Configuration diagram of a conventional optical fiber type Fabry-Perot resonator Cross-sectional view showing a second embodiment of the present invention

Claims (2)

[Claims] (1) A piezoelectric element, an optical fiber fixed to the piezoelectric element so that the electric field application direction of the piezoelectric element is parallel to the fiber axis direction, and a multilayer reflective film arranged and fixed on both end surfaces of the optical fiber. An optical fiber type Fabry-Perot resonator characterized by being equipped with a mirror. (2) a piezoelectric element, an optical fiber fixed to the piezoelectric element such that the electric field application direction of the piezoelectric element is parallel to the fiber axis direction, and an optical fiber formed at a predetermined interval at a right angle to the fiber axis. What is claimed is: 1. An optical fiber type Fabry-Perot resonator comprising: two grooves, and two multilayer reflectors inserted and fixed in each groove.