JPH0827411B2 - Optical fiber type Fabry-Perot resonator - Google Patents

Description

The present invention relates to the structure of an optical fiber type Fabry-Perot resonator using an optical fiber.

(Prior Art) In a conventional optical fiber type Fabry-Perot resonator, as shown in FIG. 2 (a), an optical fiber 2 is linearly fixed to a substrate 1, and a multilayer film is formed on both ends of the optical fiber 2. The reflecting mirror 3 is vapor-deposited, or as shown in FIG. 2B, the reflecting mirror 3 having a multilayer film is formed on both ends of the optical fiber 2 fixed to the substrate 1.
The glass plate 4 on which was vapor-deposited was adhered. In addition,
In the figure, 2a is a core of the optical fiber 2, and 2b is a clad.

The optical fiber type Fabry-Perot resonator having such a configuration is designed by the following method. First, the finesse f indicating the performance of the Fabry-Perot resonator is the reflection mirror 3
When the reflectance of R is R, it is expressed by the following equation.

f = πF / 2 (1) F = 4R / (1-R) ² (2) The frequency interval Δf of the Fabry-Perot resonator is represented by Δf = v / 2L (3). Where v is the speed of light in the optical fiber, L
Is the optical fiber length. Thereby, for example, finesse f
To obtain 100, the reflectance R must be 96.7%. Also, the speed of light v in the optical fiber at a wavelength of 1.30 μm
Is 2.0078 × 10 ¹¹ mm / sec, the frequency interval Δf is 10
For GHz, the optical fiber length is 10.039 mm.

(Problems to be Solved by the Invention) Although the above-mentioned conventional optical fiber type Fabry-Perot resonator can be manufactured relatively easily, the reflecting mirror 3 or the glass plate 4 is provided at both ends of the optical fiber type Fabry-Perot resonator. Since it is provided, it is extremely difficult to connect the external optical fiber. Further, since both end surfaces thereof are reflective surfaces, it is difficult to find the position of the core 2a of the optical fiber 2. .

In view of the above problems, an object of the present invention is to provide an optical fiber type Fabry-Perot resonator in which an external optical fiber is easily and stably connected to both ends of the Fabry-Perot resonator with low loss.

(Means for Solving the Problems) In order to achieve the above-mentioned object, in the claim (1), a substrate, an optical fiber fixed to the substrate, and a predetermined distance from the optical fiber are provided at right angles to the fiber axis. Two grooves formed, and having a thickness almost the same as the width of the groove, and inserted into each groove,
And two fixed multilayer mirrors.

Further, in claim (2), the substrate is made of a liquid crystal polymer.

(Operation) According to claim (1), the optical connection between the optical fiber of the Fabry-Perot resonator and the external optical fiber is made in advance.

Further, according to claim (2), the substrate is made of a liquid crystal polymer to prevent the influence of ambient temperature.

(Embodiment) FIG. 1 shows a first embodiment of an optical fiber type Fabry-Perot resonator according to the present invention. FIG. 1 (a) is a perspective view thereof, and FIG. 1 (b) is a longitudinal side view. FIG. 1 (c) is a sectional view taken along line AA of FIG. 1 (a). In the figure, 10 is a glass substrate having a convex portion 10a formed in the center in the longitudinal direction, 11 is a long groove linearly formed on the upper surface of the convex portion 10a of the substrate 10 along the longitudinal direction, and the long groove 11 will be described later. It has a width slightly larger than the diameter of the optical fiber 12. Reference numeral 12 is a single-mode optical fiber having a cutoff wavelength of 1.12 μm (hereinafter, simply referred to as an optical fiber), 12a is a core of the optical fiber 12, 12b is a cladding of the optical fiber 12, and 12c is a coating of the optical fiber 12. A portion of the optical fiber 12 from which the coating 12c is removed is inserted into the long groove 11, and the long groove 11 is formed by the epoxy adhesive EA.
It is fixed inside.

13a, 13b are a pair of grooves formed in the convex portion 10a of the glass substrate 10, each groove 13a, 13b is perpendicular to the axial direction of the optical fiber 12 and has a predetermined interval, for example, 10 mm, each The width of the groove is set to 43 μm and the depth is set to 1 mm. Reference numerals 14a and 14b are multilayer 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, and are inserted so that the reflecting surfaces face each of the grooves 13a and 13b, and are bonded by an epoxy adhesive EA. It is fixed to the grooves 13a and 13b.

Next, a method of manufacturing the optical fiber type Fabry-Perot resonator having the above structure will be described.

First, in the long groove 11 previously formed in the convex portion 10a of the substrate 10,
The portion of the optical fiber 12 from which the coating 12c has been removed (substantially the same as the length of the long groove 11) is inserted and fixed with an epoxy adhesive EA. Next, using a special dicing device as shown in Fig. 3 (Tadao Saito, Junji Watanabe: "Micro-shape processing", 59 Japan Society for Precision Engineering, Preprints, 208 (October 59)) The sapphire blade 20 is rotated by the air spindle 21 at a high wind speed of 1300 m / min, and the particle diameter of SiO _{2 is} 0.24 μm.
While the abrasive grains 22 are sprayed on the substrate 10, the grooves 13a and 13b having the above-mentioned numerical values and positional relationships are formed. Thereby, the grooves 13a, 1
The side surface of 3b is close to a mirror surface. Then, the multilayer film reflecting mirrors 14a and 14b under the above-mentioned numerical conditions are inserted into the grooves 13a and 13b so that their reflecting surfaces face each other, and fixed with the epoxy adhesive EA, thereby completing 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 was made with high accuracy.

The optical fiber type Fabry-Perot resonator manufactured in this way was measured with a DFB semiconductor laser of 1.30 μm, and as a result, a finesse f of 55 could be obtained at a frequency interval Δf of 10 GHz. The insertion loss was 0.6 dB.

As described above, according to the first embodiment, a high finesse optical fiber type Fabry-Perot resonator can be easily constructed, and it is necessary to connect both ends of the Fabry-Perot resonator to another optical fiber. There is no need for complicated work.

FIG. 4 is a perspective view showing a second embodiment of the optical fiber type Fabry-Perot resonator according to the present invention. In the second embodiment, an optical fiber type Fabry-Perot resonator according to the first embodiment is arrayed by using four optical fibers. In the figure, 30 is a glass substrate having a convex portion 30a in the longitudinal direction, 31a to 31d are four parallel long grooves, 32a to 3
2d is an optical fiber, 33a and 33b are grooves formed orthogonal to the long grooves 31a to 31d, and 34a and 34b are 0.5% transmittance at a wavelength of 1.30 μm,
A multi-layered film mirror made of thin glass with a thickness of 40 μm.
Structural parameters and manufacturing methods of 31a to 31d, 33a, 33b and optical fibers 32a to 32d are similar to those of the first embodiment.

As a result of measuring each optical fiber type Fabry-Perot resonator using each optical fiber 32a to 32d with a DFB semiconductor laser of 1.30 μm, the frequency interval Δf is 10 GHz ± 5 MHz, and the finesse f is 68,45,105,88, respectively. The insertion loss was 0.5 dB, 0.8 dB, 0.3 dB, and 0.6 dB, respectively.

In the first and second embodiments, the substrate 1
Although the glass materials 0 and 30 are used, the invention is not limited thereto, and the same optical fiber type Fabry-Perot resonator can be realized by using a metal substrate or a ceramic substrate. In particular, when it is desired to perform frequency tuning by temperature, it is preferable to provide a heat source such as a heater on the substrate and use a material having a large expansion coefficient as the substrate material.

On the other hand, in order to prevent the influence of ambient temperature, it is effective to use a liquid crystal polymer having a small linear expansion coefficient (coefficient of linear expansion 3 × 10 ⁻⁶ ). When this material is applied, the optical fiber is arranged so that its axial direction is parallel to the long glass fiber direction of the liquid crystal polymer. In the optical fiber type Fabry-Perot resonator using the liquid crystal polymer as a substrate and having a frequency interval Δf of 10 GHz, the output light hardly changed when the temperature was between −10 ° C. and 80 ° C.

In addition, in the first and second embodiments, when the optical fibers 12, 32a to 32d are bonded and fixed to the substrates 10 and 30, birefringence occurs due to the influence of lateral pressure, and transmitted light has a side peak in addition to the main peak. A peak may appear, and in order to solve this, a polarization-maintaining optical fiber having a large birefringence was used in advance in the optical fiber section. As a result, linearly polarized light is used for the incident light, and this linearly polarized light is incident parallel to the main axis of the polarization of the polarization-maintaining optical fiber.As a result, the output light from the optical fiber Fabry-Perot resonator has only the main peak and the side peak. No peak was seen.

(Effect of the Invention) As described above, according to claim (1), the substrate, the optical fiber fixed to the substrate, and the optical fiber are formed at a predetermined interval and at right angles to the fiber axis direction. Since it is equipped with two grooves and two multilayer film reflecting mirrors inserted and fixed in each groove, a high finesse can be obtained,
There is an advantage that an optical fiber type Fabry-Perot resonator connected to an external optical fiber can be provided easily and stably without a work for connecting another optical fiber to both ends thereof and with low loss. Further, since the optical fiber is fixed to the substrate, there is an advantage that it operates stably and can be miniaturized.

Further, according to claim (2), since the substrate is made of a liquid crystal polymer, it is possible to prevent the influence of a change in ambient temperature.

[Brief description of drawings]

FIG. 1 shows a first embodiment of an optical fiber type Fabry-Perot resonator according to the present invention. FIG. 1 (a) is a perspective view, FIG. 1 (b) is a longitudinal side view, and FIG. 1C is a sectional view taken along the line AA of FIG. 1A, FIG. 2 is a sectional view of a conventional optical fiber type Fabry-Perot resonator, FIG. 3 is an explanatory view of a dicing device, and FIG. The drawing is a perspective view showing a second embodiment of an optical fiber type Fabry-Perot resonator according to the present invention. In the figure, 10,30 ... substrate, 10a, 30a ... convex portion, 11, 31a to 31d
...... Long groove, 12,32a to 32d …… Single mode optical fiber, 13
a, 13b, 33a, 33b ... groove, 14a, 14b, 34a, 34b ... multilayer mirror, EA ... epoxy adhesive.

Front page continued (72) Inventor Junji Watanabe 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corp. (72) Inventor Tadao Saito 1-1-6 Uchiyuki-cho, Chiyoda-ku, Tokyo Nihon Telegraph Telephone Corporation (72) Inventor Shinsuke Matsui 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A substrate, an optical fiber fixed to the substrate, two grooves formed in the optical fiber at a predetermined interval and at right angles to the fiber axis, and 2 inserted and fixed in each groove. An optical fiber type Fabry-Perot resonator characterized by comprising a plurality of multilayer film reflecting mirrors. 2. The optical fiber type Fabry-Perot resonator according to claim 1, wherein the substrate is made of liquid crystal polymer.