JP2000121820A - Manufacture of optical fiber grating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing optical fiber gratings suitable for manufacturing long-sized or various characteristic gratings. SOLUTION: A phase mask 30 of a planar body which is arrayed with a plurality of recessed parts at equal angle intervals in a radial form in its main surface is arranged in such a manner that its main surface is parallel and opposite to the longitudinal direction of the photosensitive optical fiber 20. The photosensitive optical fiber 20 is moved in its longitudinal direction 21 and the phase mask 30 is rotated in synchronization in such a manner that its moving speed and the circumferential speed of the rotating direction 38 of the phase mask in a light beam radiation section 16 are equalized to each other. The photosensitive optical fiber 20 is then irradiated with the light beam via the phase mask 30, by which the desired gratings are formed on the core of the optical fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical fiber grating. Optical fiber gratings are used in various optical devices such as reflection filters in wavelength division multiplexing transmission and dispersion compensators in optical fiber transmission.Single-period gratings or chirped gratings with a predetermined period are required depending on the application. (For example, Ref. 1 “Applied Physics Vol. 66, No. 1, pp.
33-36 (1997) ").

[0002]

2. Description of the Related Art Conventionally, a photosensitive optical fiber is irradiated with a light beam through a phase mask to cause a refractive index change in the core of the photosensitive optical fiber in accordance with a stripe pattern of diffracted light by the phase mask. A method for producing an optical fiber grating is known. In the manufacturing method using a phase mask, the light beam and the optical fiber are usually moved relative to each other in the longitudinal direction for irradiation (for example, see Reference 2 “ELECTRONICS LETTERS 12THM”).
ay 1994 Vol.30 No.10 pp811-812 "). In addition, a phase mask is a phase grating composed of convex portions and concave portions on a transparent substrate.
(Diffraction grating), which is usually manufactured by etching the surface of a quartz substrate by reactive ion etching to form parallel-arranged concave portions (for example, see Reference 3 “ELECTRONICS LETTERS 18th Mar. . 19
93 Vol.29 No.6 pp566-568 ").

[0003]

However, in such a conventional manufacturing method, first, there is a problem that the grating length is limited by the size of the phase mask. For example, the reflectivity of a Bragg grating filter directly depends on the length of the grating writing area, that is, the grating length, and a long one is required to obtain high reflectivity. However, phase masks usually require processing in a vacuum apparatus such as reactive etching for their production, and the size of the phase mask cannot be so large at present, and a grating length of about 100 mm is limited. Met. Thus, one object of the present invention is to
An object of the present invention is to provide a method of manufacturing an optical fiber grating that can manufacture an optical fiber grating having a long grating length without being limited by the size of a phase mask.

In addition, in such a conventional manufacturing method, there is a problem that basic characteristics such as the period of the refractive index modulation of the fiber are uniquely determined by the phase mask. That is, in order to manufacture an optical fiber grating corresponding to various reflection wavelengths λB, it is necessary to change the period of the refractive index modulation of the fiber. In order to change the period, it is necessary to re-create a phase mask having a diffraction grating corresponding thereto for each of various reflection wavelengths [lambda] B, and there has been a problem that the phase mask is cumbersome and cannot be cost-effective. Therefore, another object of the present invention is to provide a method of manufacturing an optical fiber grating that can cope with a plurality of periods of refractive index modulation with one phase mask.

[0005]

SUMMARY OF THE INVENTION The present invention is a method of manufacturing an optical fiber grating using a plate-shaped phase mask in which a plurality of concave portions are radially arranged at equal angular intervals. Then, by moving the photosensitive optical fiber in its longitudinal direction and rotating the phase mask in synchronization with the movement, irradiating the photosensitive optical fiber with a light beam through the phase mask, the photosensitive optical fiber This is to produce an optical fiber grating by causing a refractive index modulation in the core. Thereby, a desired grating length can be obtained according to the manufacturing time.

In one embodiment of the present invention, the photosensitive optical fiber can be moved in the orthogonal direction, and the mirror and lens of the light beam system can be moved in the orthogonal direction in conjunction therewith. The optical fiber set is moved in the orthogonal direction so as to correspond to a predetermined position in the radiation direction of the phase mask, that is, to correspond to a desired period of the diffraction grating formed in the circumferential direction of the phase mask. After setting, the optical fiber grating is manufactured by irradiating the photosensitive optical fiber with a light beam through a phase mask. Alternatively, irradiating the photosensitive optical fiber with a light beam through the phase mask while moving the set of the mirror, the lens, and the photosensitive optical fiber in the orthogonal direction corresponding to a predetermined range in the radiation direction of the phase mask. Thus, an optical fiber grating is produced. Accordingly, it is possible to produce gratings having various periods with a common phase mask, and to produce gratings having various characteristics such as chirp gratings.

In another embodiment of the present invention, the movement of the photosensitive optical fiber in the orthogonal direction is fixed, and the phase mask can be moved in the orthogonal direction of the photosensitive optical fiber. Move the phase mask so that the period of the diffraction grating formed in the direction becomes the desired period, or move the phase mask so that the period of the diffraction grating changes at the desired period, and move the phase mask to the photosensitive optical fiber. An optical fiber grating is manufactured by irradiating a light beam through a phase mask.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. First, a phase mask used in each embodiment of the present invention and an optical fiber grating manufacturing apparatus used in some embodiments will be described with reference to FIGS.
This will be described with reference to FIG. FIG. 1 is a conceptual diagram of an optical fiber grating manufacturing apparatus, in which 11 is a laser light source, 12 is an attenuator, 13 is a mirror, 14 is a cylindrical lens, 20 is a photosensitive optical fiber, and 30 is a phase mask. FIG. 2 is an enlarged explanatory view of a portion A in FIG. 3A and 3B are conceptual views of the phase mask in FIG. 1, FIG. 3A is a top view, FIG. 3B is a cross-sectional view, and FIG. 3C is an enlarged view of a portion B in FIG. is there.

Referring to FIG. 3, a phase mask 30 has a plurality of recesses 33 formed on a main surface 32 of a transparent quartz glass plate 31.
And projections 34 are radially arranged at equal angular intervals to form a radial diffraction grating array 35. As the position in the radiation direction, that is, the distance from the center 36 of the radiation state diffraction grating array increases, the width の of the concave portion 33 or the convex portion 34 increases, and the width の of the concave portion 33 or the convex portion 34 decreases as the position approaches the center. That is, the radiation state diffraction grating array 35
When a grating is formed by using a diffraction grating located far from the center 36 of the radiation state diffraction grating array,
A grating having a long grating interval (period or pitch) is formed, and a grating having a short grating interval is formed at a close position. In addition, the width の of the concave portion 33 and the convex portion 34 of the radiation state diffraction grating row 35 is the same at any location as long as the distance from the center 36 of the radiation state diffraction grating row is equal. On the other hand, a phase mask rotation axis 37 is provided at the center 36 of the radiation state diffraction grating on the side opposite to the main surface 32.

Referring to FIG. 1, in this optical fiber grating manufacturing apparatus, a phase mask 30 having a radiation state diffraction grating array formed on a main surface 32 is arranged in a longitudinal direction 21 of a photosensitive optical fiber 20. The main surfaces 32 are arranged so as to be parallel and opposed to each other. The phase mask 30 and the photosensitive optical fiber 20 are arranged so as not to directly contact each other. On the other hand, the laser light source 11 emits 244 nm ultraviolet light, and the light beam 15 emitted from the laser light source 11 passes through an attenuator (output adjuster) 12, changes its direction by a mirror 13, and has a cylindrical lens 14.
, The beam diameter is adjusted, and irradiation is performed perpendicularly to the back surface of the main surface 32 of the phase mask 30. The positional relationship between the light beam 15 and the photosensitive optical fiber 20 is such that the traveling direction of the light beam 15 and the longitudinal direction 21 of the photosensitive optical fiber 20 are always orthogonal. In addition, the light beam 15 is formed in the concave portion 3 radially formed in the longitudinal direction 21 of the photosensitive optical fiber 20 and the main surface 32 of the phase mask 30.
As shown in FIG. 2, the 3 and the projection 34 have a positional relationship of irradiating a substantially orthogonal portion (light beam irradiating section 16).

The phase mask 30 has a phase mask rotation axis 37.
It has a mechanism that rotates around the axis of rotation. The rotation speed of the phase mask 30 can be arbitrarily controlled by a controller (not shown). The photosensitive optical fiber 20 has a mechanism that moves in the longitudinal direction 21 and the same direction as the rotation direction 38 of the phase mask. This mechanism includes a delivery drum and a take-up drum (not shown). Further, the photosensitive optical fiber 20 has its longitudinal direction 2.
It also has a mechanism for moving in a direction orthogonal to 1 (hereinafter referred to as an orthogonal direction). The speed of the two movements of the photosensitive optical fiber 20 can be arbitrarily controlled by a controller (not shown). On the other hand, the mirror 13 for guiding the light beam 15 onto the phase mask and the cylindrical lens 14 are configured to be movable in conjunction with the movement of the photosensitive optical fiber 20 in the orthogonal direction 22. During this movement, the positional relationship among the light beam 15, the phase mask 30, and the photosensitive optical fiber 20 always keeps the above-mentioned state.

Next, a first embodiment of the present invention for producing a grating having a single period in which the period of the refractive index modulation is Λ, that is, a grating having a constant grating interval, is shown in FIGS. 1 to 3. I will explain. First,
The photosensitive optical fiber 20 is installed on a delivery drum and a winding drum having a moving mechanism. The photosensitive optical fiber 20 is obtained by adding Ge to the core and filling the core with hydrogen, and the refractive index of the core changes by ultraviolet irradiation. After the installation of the photosensitive optical fiber 20, the photosensitive optical fiber 20 is moved to the lower part of the phase mask 30 in which the radiation state diffraction grating array 35 is formed on the main surface 32. Here, the photosensitive optical fiber 20 is formed radially below the diffraction grating required to form a desired grating interval (refractive index modulation with a desired period), that is, on the main surface 32 of the phase mask 30. It is moved so that the width in the rotation direction 38 of the concave portion 33 and the convex portion 34 becomes 回 転 (the period is 2 Λ). In addition, the mirror 13 and the cylindrical lens 14 that guide the light beam 15 onto the phase mask 30 in conjunction with the photosensitive optical fiber 20 are also moved. Next, the phase mask 30 is rotated with the phase mask rotation axis 37 at the center 36 of the radiation state diffraction grating array as the rotation axis. In addition, the photosensitive optical fiber 20 is moved by a moving mechanism at a desired constant speed in the longitudinal direction 21 and thus in the same direction as the rotational direction 38 of the phase mask 30. The rotational speed of the phase mask 30 is such that the moving speed in the rotation direction 38 of the portion of the phase mask 30 (the light beam irradiation unit 16) directly above the photosensitive optical fiber 20 is the moving speed of the photosensitive optical fiber 20 in the longitudinal direction 21. Synchronize so as to be constant speed.

Next, a light beam 15 is emitted from the laser light source 11, and the light beam 15 having passed through the attenuator 12, the mirror 13, and the cylindrical lens 14 is incident on a phase mask 30 on the opposite surface of the main surface 32. The incident position of the light beam 15 is a portion where the longitudinal direction 21 of the photosensitive optical fiber 20 and the concave portion 33 or the convex portion 34 radially formed on the main surface 32 of the phase mask 30 are substantially orthogonal to each other. The portion where the fiber 20 and the phase mask 30 are moving at a constant speed. The light beam that has entered the phase mask 30 is concavo-convex 33 of a portion having a width Λ necessary to form a desired grating interval の of the above-described unevenness of the radiation state diffraction grating array 35.
And the convex portion 34) to generate a stripe-shaped diffracted light. The diffracted light is applied to the photosensitive optical fiber 20 disposed below the phase mask 30, and causes the core of the photosensitive optical fiber 20 to perform a refractive index modulation with a desired period Λ.

The photosensitive optical fiber 20 and the portion of the light beam irradiating section 16 of the phase mask 30 move and rotate at a constant speed and a constant speed, and a desired state of the radiation state diffraction grating array 35 generating the diffracted light. Since the widths of the concave portion 33 and the convex portion 34 are always constant, a grating having a constant grating interval (refractive index modulation with a constant period Λ) is formed on the photosensitive optical fiber 20 that has passed through the light beam irradiation section 16. . As described above, according to this embodiment, a required grating length can be obtained by lengthening the time for manufacturing the grating. Further, by changing the initial position of the mirror 13, the cylindrical lens 14, and the photosensitive optical fiber 20 in the orthogonal direction, a grating having a desired grating interval and a constant grating interval can be obtained. With the mask 30, gratings having various desired reflection wavelengths can be manufactured. In this embodiment, the moving speed of the photosensitive optical fiber in the longitudinal direction is constant.
By changing the moving speed, apodization of a single-period grating can be performed.

Next, a second embodiment of the present invention, in which a grating called a chirp grating whose grating interval changes continuously from large to small, here, a large period か ら a to a small period Λb, is manufactured. The form will be described. First, the photosensitive optical fiber 20, the mirror 13, and the cylindrical lens 14 are moved in the orthogonal direction in the same manner as in the above-described embodiment, and the phase mask 3 is moved.
The concave portion 33 and the convex portion 34 of the zero-emission state diffraction grating array 35
Is initially set so that the light beam irradiating section 16 comes to a portion where the width of .DELTA.a becomes .DELTA.a. Next, in the same manner as in the above-described embodiment, the photosensitive optical fiber 20 is moved in the longitudinal direction 21;
The rotation of the phase mask 30 synchronized with the rotation is started.

Next, in the same manner as in the above-described embodiment, the light beam 15 is made incident on the phase mask 30, and the preparation of the grating on the photosensitive optical fiber 20 is started.
Simultaneously with this start, the photosensitive optical fiber 20, the mirror 13, and the cylindrical lens 14 are linked to each other at a desired speed in the orthogonal direction 22 in which the widths of the concave portions 33 and the convex portions 34 of the radiation state diffraction grating array 35 are reduced. Move. Then, when the width of the concave portion 33 and the convex portion 34 of the radiation state diffraction grating becomes the width Δb of the concave portion 33 and the convex portion 34 of the diffraction grating necessary to form a desired period Δb, the fabrication of the grating is terminated. . At this time, the phase mask 30
The rotational speed of the phase mask 30 just above the photosensitive optical fiber 20, that is, the concave portion 33 or the convex portion radially formed in the longitudinal direction 21 of the photosensitive optical fiber 20 and the main surface 32 of the phase mask 30. The phase mask 30 is controlled so that the portion of the phase mask 30 (the light beam irradiating section 16), which is substantially orthogonal to the portion 34, has the same speed as the moving speed of the photosensitive optical fiber 20. Therefore, the rotation speed of the phase mask 30 increases as the photosensitive optical fiber 20 approaches the phase mask rotation axis 37. By performing this rotation speed control, the intensity of the diffracted light becomes uniform in the entire region of the manufactured grating, and uniform refractive index modulation can be obtained.

As described above, the movement of the photosensitive optical fiber 20 in the longitudinal direction 21 and the movement of the light beam
In the rotation direction 38 is performed at a constant speed and a constant speed, and at the same time, the photosensitive optical fiber 20 moves toward the rotation axis 37 of the phase mask 30. 35 concave portion 33 and convex portion 34
The width of the concave portion 33 and the convex portion 34 required to form the desired period Δa is determined by the width Δb of the concave portion 33 and the convex portion 34 necessary to form the desired period Δb.
Changes continuously. Therefore, the light beam irradiation unit 16
Is formed on the photosensitive optical fiber 20 that has passed through the grating, in which the grating interval changes continuously from the desired period Λa to the period Λb. Further, the dispersion amount of the chirp grating can be set to a desired value by changing the moving speed of the mirror 13, the cylindrical lens, and the photosensitive optical fiber in the orthogonal direction. That is, the variance is small when moved fast, and large when moved slowly. As described above, according to the present embodiment, a chirped grating having desired characteristics can be manufactured using the phase mask 30 common to the formation of the equal-period grating. In addition, also in this embodiment,
Apodization can be performed by changing the moving speed of the photosensitive optical fiber in the longitudinal direction. In addition, by changing the moving speed of the set of the mirror 13, the cylindrical lens, and the photosensitive optical fiber in the rotation axis direction according to a desired function, a grating that changes from the period Λa to the period Λb according to the desired function is created. Can also.

In the above-described embodiment, the light beam is irradiated by moving the mirror and the cylindrical lens, which guide the light beam onto the phase mask, and the photosensitive optical fiber in the orthogonal direction of the photosensitive optical fiber to irradiate the light beam. In the following, the mirror, the cylindrical lens, and the photosensitive optical fiber are fixed (the photosensitive optical fiber moves in the longitudinal direction), and the phase mask is moved in the direction perpendicular to the photosensitive optical fiber. An embodiment in which a grating is manufactured by irradiating a light beam will be described with reference to FIGS. 4A and 4B are conceptual diagrams of an optical fiber grating manufacturing apparatus. FIG. 4A is a side view, and FIG. 4B is a top view. Referring to FIG. 4, this optical fiber grating manufacturing apparatus includes a laser light source 11, an attenuator 12, and a mirror 1 similarly to the manufacturing apparatus shown in FIG.
3, the cylindrical lenses 14 and 30 are provided with a phase mask, and the mirror 13, the cylindrical lens 14 and the photosensitive optical fiber are fixed in the orthogonal direction 22 except for a fine adjustment mechanism. 22
The manufacturing apparatus shown in FIG. 1 is different from the manufacturing apparatus shown in FIG. The phase mask 30 has a mechanism for rotating around a phase mask rotation axis 37 at the center 36 of the radiation state diffraction grating array as a rotation axis, and a mechanism for moving the phase mask rotation axis 37 in the orthogonal direction 22 of the photosensitive optical fiber 20. ing. The rotational speed, the moving speed, and the moving amount of the phase mask 30 can be arbitrarily controlled by a controller (not shown).

Next, a third embodiment of the present invention for producing a single-period grating having a refractive index modulation period of Λa, that is, a grating having a constant grating interval, will be described with reference to FIG. . First, the photosensitive optical fiber 20 is set on a delivery drum and a take-up drum having a moving mechanism. Next, the phase mask 30 is set such that the portion where the width of the concave portion 33 and the convex portion 34 of the phase mask 30 becomes Δa comes to the portion that becomes the light beam irradiation portion 16.
Is moved to the upper part of the photosensitive optical fiber 20. Next, as in the above-described embodiment, the phase mask 30 is rotated, and the photosensitive optical fiber 20 is moved in the longitudinal direction 21 at a desired constant speed using a moving mechanism. The rotation speed of the phase mask 30 is the same as in the above-described embodiment, and the rotation direction 38
Is set to be equal to the moving speed of the photosensitive optical fiber 20.

Next, as in the above-described embodiment, a light beam 15 is emitted from the laser light source 11, and the light beam 15 having passed through the attenuator 12, the mirror 13, and the cylindrical lens 14 is made incident on the phase mask 30, and Is made. The laser light that has entered the phase mask 30 is diffracted by the radiation state diffraction grating array, and generates striped diffraction light. The diffracted light is applied to the photosensitive optical fiber 20 disposed below the phase mask 30 to cause the core of the photosensitive optical fiber 20 to have a desired period of refractive index modulation. Photosensitive optical fiber 20 and laser irradiation section 16
The phase mask 30 moves and rotates at a constant speed and a constant speed, and the period of the radiation state diffraction grating array 35 generating the diffracted light is always constant at 2Λa. On the photosensitive optical fiber 20, a grating having a constant grating interval is manufactured. That is,
A grating having a desired grating interval Δa and a constant grating interval is manufactured.

As described above, according to this embodiment, the required grating length can be obtained by lengthening the grating manufacturing time, as in the above-described embodiment. By changing the initial position in the radiation direction (the orthogonal direction 22), gratings having various desired reflection wavelengths can be manufactured with one phase mask 30. Further, according to this embodiment, since the optical path of the light beam can be fixed, there is no change in the laser characteristics (energy, polarization dependence, etc.), and the ultraviolet light is stable with respect to the photosensitive optical fiber. There is also obtained an effect that beam irradiation can be performed. In this embodiment, as in the above-described embodiment, the moving speed of the photosensitive optical fiber in the longitudinal direction is changed, and the rotation speed of the phase mask is changed in synchronization with the movement speed. Apodization of a one-period grating can be performed.

Next, a fourth embodiment of the present invention for producing a chirped grating which continuously changes from the period Λa to the period Λb.
An embodiment will be described. First, as in the third embodiment, the photosensitive optical fiber 20 is installed, and the width of the concave portion 33 and the convex portion 34 of the radiation state diffraction grating array 35 in the light beam irradiation unit 16 is set to Δa. The phase mask 30 is moved, and the lengthwise direction 2 of the photosensitive optical fiber 20 is moved.
1 and a rotation of the phase mask 30 synchronized with the moving speed is started.

Next, in the same manner as in the above-described embodiment, the light beam 15 is made incident on the phase mask 30, and the preparation of the grating on the photosensitive optical fiber 20 is started.
At the same time as this start, the phase mask 30 is moved to the phase mask rotation axis
The phase mask 30 is moved at a desired speed in a direction in which the phase mask 7 approaches the photosensitive optical fiber 20, that is, in a direction in which the widths of the concave portions 33 and the convex portions 34 of the radiation state diffraction grating array 35 that come above the photosensitive optical fiber 20 become narrower. Move. Then, when the width of the concave portion 33 and the convex portion 34 of the radiation state diffraction grating array 35 that comes to the upper part of the photosensitive optical fiber 20 becomes the width Δb necessary for forming the desired grating interval Δb, the grating fabrication is terminated. .

At this time, the rotation speed of the phase mask 30 is set such that the portion of the phase mask 30 immediately above the photosensitive optical fiber 20 (the portion of the phase mask 30 of the light beam irradiation unit 16) moves the photosensitive optical fiber 20. Control is performed so that the speed is always the same as the speed. Therefore, the rotation speed of the phase mask 30 increases as the phase mask rotation axis 37 approaches the photosensitive optical fiber 20. By performing this rotation speed control, the intensity of the diffracted light becomes uniform over the entire region when the grating is manufactured, and uniform refractive index modulation can be caused.

The movement of the photosensitive optical fiber 20 in the longitudinal direction 21 and the movement of the phase mask 30 in the rotation direction 38 of the light beam irradiation section 16 are performed at a constant speed and a constant speed.
Since the phase mask rotation axis 37 moves in the direction approaching the photosensitive optical fiber 20, the phase mask 30 has the concave portion 33 and the convex portion 34 of the radiation state diffraction grating array 35 that generates diffracted light coming to the upper part of the photosensitive optical fiber 20. Is continuously changed from the width Δa of the concave portion 33 and the convex portion 34 necessary for forming the desired period Δa to the width Δb of the concave portion 33 and the convex portion 34 necessary for forming the desired period Δb. Changes to Therefore, the photosensitive optical fiber 20 that has passed through the light beam irradiation unit 16 has a grating interval of a desired period 所 望.
A grating that continuously changes from “a” to period “b” is manufactured.

As described above, according to this embodiment, a chirped grating having desired characteristics can be manufactured by using the phase mask 30 common to the formation of the equal-period grating. Further, by changing the moving speed of the phase mask 30 (the speed at which the phase mask rotation axis 37 approaches the photosensitive optical fiber 20), the dispersion amount of the chirp grating can be set to a desired value. In this embodiment, apodization can be performed by changing the moving speed of the photosensitive optical fiber in the longitudinal direction, and the moving speed of the phase mask in the rotation axis direction can be changed according to a desired function. By changing, the period Λ
It is possible to create a grating that changes from a to a period Λb according to a desired function.

[0027]

As described above, according to the present invention, the phase mask 30 in which a plurality of concave portions are radially arranged at equal angular intervals is used, and in synchronization with the movement of the photosensitive optical fiber 20 in the longitudinal direction. By rotating the phase mask and irradiating a light beam to form a grating on the photosensitive optical fiber, a long grating length can be obtained, and various types of chirp gratings and the like can be obtained with a common phase mask. This has the effect that a grating having characteristics can be produced.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an optical fiber grating manufacturing apparatus used in an embodiment of the present invention.

FIG. 2 is an enlarged explanatory view of a portion A in FIG. 1 (b).

FIG. 3 is a conceptual diagram of a phase mask in FIG. 1;

FIG. 4 is a conceptual diagram of another optical fiber grating manufacturing apparatus used in the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 11 laser light source 12 attenuator 13 mirror 14 cylindrical lens 15 light beam 16 light beam irradiation unit 20 photosensitive optical fiber 21 longitudinal direction 22 orthogonal direction (rotation axis direction) 30 phase mask 31 quartz glass plate 32 main surface 33 concave portion 34 convex portion 35 Radiation state diffraction grating array 36 Center of radiation state diffraction grating 37 Phase mask rotation axis 38 Phase mask rotation direction

Claims (9)

[Claims] 1. A method of manufacturing an optical fiber grating by irradiating a photosensitive optical fiber with a light beam via a phase mask while moving the photosensitive optical fiber in a longitudinal direction thereof, wherein a plurality of the phase masks are provided. Using a phase mask in which concave portions and convex portions are radially formed at equal angular intervals, rotatably disposing the phase mask, and rotating the phase mask in synchronization with the longitudinal movement of the photosensitive optical fiber. And irradiating the photosensitive optical fiber with a light beam through a phase mask. 2. A method for producing an optical fiber grating by irradiating a light beam through a phase mask to a photosensitive optical fiber while moving the photosensitive optical fiber in a longitudinal direction thereof, wherein a plurality of the phase masks are provided. Using a phase mask in which the concave portions and the convex portions are radially formed at equal angular intervals, rotatably disposing the phase mask, and turning a mirror that turns the light beam and guides the light beam onto the phase mask. A lens for adjusting the beam diameter of the light beam, movably disposed in a direction perpendicular to the longitudinal direction, and a mirror, a lens, and a photosensitive optical fiber. After being moved in a direction orthogonal to the longitudinal direction so as to correspond to a predetermined position in the radiation direction of the phase mask, the photosensitive optical fiber in the longitudinal direction is moved. While in synchronization with movement by rotating the phase mask, said photosensitive optical fiber through the phase mask to a light beam, an optical fiber grating manufacturing method of which features a thing. 3. The method of manufacturing an optical fiber grating according to claim 2, wherein the moving speed of the photosensitive optical fiber in the longitudinal direction is constant. 4. A method for producing an optical fiber grating by irradiating a light beam through a phase mask to a photosensitive optical fiber while moving the photosensitive optical fiber in the longitudinal direction, wherein a plurality of the phase masks are provided. Using a phase mask in which the concave portions and the convex portions are radially formed at equal angular intervals, rotatably disposing the phase mask, and turning a mirror that turns the light beam and guides the light beam onto the phase mask. A lens for adjusting the beam diameter of the light beam, movably disposed in a direction perpendicular to the longitudinal direction, and a mirror, a lens, and a photosensitive optical fiber. Moving the photosensitive optical fiber in the longitudinal direction while moving the photosensitive optical fiber in a direction perpendicular to the longitudinal direction corresponding to a predetermined range in the radiation direction of the phase mask. And synchronously by rotating the phase mask, said photosensitive optical fiber through the phase mask to a light beam, an optical fiber grating manufacturing method of which features a thing. 5. The method of manufacturing an optical fiber grating according to claim 4, wherein the moving speed of the photosensitive optical fiber in a direction orthogonal to the longitudinal direction is changed. 6. A method for producing an optical fiber grating by irradiating a light beam through a phase mask to a photosensitive optical fiber while moving the photosensitive optical fiber in a longitudinal direction thereof, wherein a plurality of the phase masks are provided. Using a phase mask in which the concave and convex portions are radially formed at equal angular intervals, the phase mask is rotatably arranged and movably arranged in a direction orthogonal to the longitudinal direction of the photosensitive optical fiber, After moving the phase mask in a direction perpendicular to the longitudinal direction so that the light beam corresponds to a predetermined position in the radiation direction of the phase mask, the phase mask is moved in synchronization with the longitudinal movement of the photosensitive optical fiber. Irradiating the photosensitive optical fiber with a light beam through the phase mask while rotating the phase mask. A method for manufacturing a grayed. 7. The method of manufacturing an optical fiber grating according to claim 6, wherein the moving speed of the photosensitive optical fiber in the longitudinal direction is constant. 8. A method for producing an optical fiber grating by irradiating a photosensitive optical fiber with a light beam through a phase mask while moving the photosensitive optical fiber in the longitudinal direction, wherein a plurality of the phase masks are provided. Using a phase mask in which the concave and convex portions are radially formed at equal angular intervals, the phase mask is rotatably arranged and movably arranged in a direction orthogonal to the longitudinal direction of the photosensitive optical fiber, While moving the phase mask in a direction orthogonal to the longitudinal direction so that the light beam corresponds to a predetermined range in the radiation direction of the phase mask, and in synchronization with the longitudinal movement of the photosensitive optical fiber, Rotating the phase mask and irradiating the photosensitive optical fiber with a light beam through the phase mask. A method for manufacturing a grayed. 9. The method of manufacturing an optical fiber grating according to claim 7, wherein the moving speed of the phase mask is changed.