JPH11119029A - Manufacture of fiber grating, support member, mask and optical filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fiber grating which is longer than a diffraction grating by performing exposure while moving a mask and rotating a support member around its axis so that parts of the diffraction grating and parts of an optical fiber pass through an irradiation area of exposure light one after another. SOLUTION: The mask 15 and columnar support member 13 are set opposite to each other in such position relation that the length of the diffraction grating of the mask 15 is along the tangent of the exposure optical fiber 11 wound spirally around the columnar support member 13. Then the movement of the mask 15 and the rotation of the columnar support member 13 around its axis (ab) are performed so that the parts of the diffraction grating along the length and the parts of the exposure optical fiber 11 wound around the columnar support 13 pass through the irradiation area 19 of the exposure light one after another respectively. Those movement and rotation are performed by necessary distance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a fiber grating that can be used as an optical filter or the like,
The present invention relates to an optical fiber support member and an exposure mask suitable for the implementation, and an optical filter suitable for miniaturization.

[0002]

2. Description of the Related Art In the field of optical communication, fiber gratings are expected as a means for realizing a wavelength filter, a dispersion compensator, and the like (for example, reference 1 “Applied Physics, Vol. page"). The fiber grating is obtained by periodically changing the refractive index of the core of an optical fiber (for example, Reference 1). The periodic refractive index change (refractive index modulation) can be formed by, for example, a phase mask method (for example, the above-mentioned document 1 or document 2 “US Pat. No. 53
No. 67588 ”).

In the phase mask method, an optical fiber is irradiated with ultraviolet light through a phase mask (hereinafter, also referred to as a mask). The phase mask is a plate-like body capable of transmitting ultraviolet light. A plurality of recesses are formed on the surface of the plate. Each recess is linearly arranged at a predetermined interval. Ultraviolet light is diffracted by these concave portions. The intensity of the diffracted light is increased or decreased at a position corresponding to the arrangement interval (pitch) of the concave portions. On the other hand, the core of the optical fiber is formed of a material whose refractive index changes by ultraviolet light (such an optical fiber is called a photosensitive optical fiber). Since the above-described diffracted light is applied to the optical fiber, a periodic refractive index modulation, that is, a grating is formed on the core along the extending direction (longitudinal direction, light guiding direction) of the optical fiber. .

The above-mentioned mask is disclosed in, for example, Reference 3 “ELEC
TRONICS LETTERS 18th Mar 1
993 Vol29 No. 6 ". Further, when it is desired to widen the reflection wavelength band in the fiber grating, the structure of the chirp grating disclosed in the above document 1 may be used.

[0005]

However, the filter characteristics of the fiber grating, such as the reflection wavelength band and the flatness of the top of the reflection spectrum, depend on the length of the grating writing area of the fiber grating, that is, the grating length.

For example, when a dispersion compensator is constituted by a fiber grating, the reflection wavelength band △ λ is expressed by the following equation (1) (for example, Reference 4, “Advanced Electronics 1-16, Optical Fiber and Fiber Device, Baifukan, 1996. 7.10 ", p. 197).

△ λ = 2L / (C · D) (1) where symbol L represents the grating length, symbol C represents the speed of light, and symbol D represents the dispersion value.

According to the above equation (1), when the dispersion value D is fixed, the longer the grating length L, the wider the reflection wavelength band Δλ. However, at present, the size of the phase mask cannot be so large. This is because, for example, in order to form a phase mask, processing in a vacuum apparatus is required, but a relatively large plate-like body cannot be introduced into the vacuum apparatus. Therefore, the grating length L cannot be so large. In the conventional method, only a fiber grating having a grating length L of at most about 100 mm could be formed.

Therefore, it is longer than the conventional one, specifically, 10
It has been desired to develop a method capable of manufacturing a fiber grating having a grating length longer than 0 mm.

When a fiber grating having a long grating can be manufactured and an optical filter is constructed using the fiber grating, an optical filter having a structure suitable for miniaturization is desired.

[0011]

[Means for Solving the Problems]

(1) Therefore, according to the fiber grating manufacturing method of the present invention, a photosensitive optical fiber is exposed to light through a mask having a diffraction grating to form a refractive index modulation section on the optical fiber. In the manufacturing method, the photosensitive optical fiber is spirally wound around a cylindrical support member. Next, the mask and the support member are opposed to each other in a positional relationship such that the diffraction grating of the mask is along the tangent of the wound optical fiber. Then, the movement of the mask and the support member, so that successive portions of the diffraction grating and successive portions of the optical fiber wound on the support member pass through the irradiation area of the exposure light. The exposure is performed while performing rotation about the axis as a rotation center.

According to this manufacturing method (hereinafter, referred to as a first manufacturing method), the width of the optical fiber wound spirally and the width equal to or more than m turns of the optical fiber and the supporting member are used as a mask. A mask having a diffraction grating having a length equal to or longer than the distance L of the optical fiber that travels when rotated once around the axis is used, and only the distance L corresponds to the successive portions of the diffraction grating and the support member. While moving the mask and rotating the support member so that successive portions of the optical fiber being wound pass through the irradiation area of the exposure light,
The exposure can be performed. Here, m is an integer of 2 or more.

[0013] For this reason, each of the turns of the optical fiber for m turns is exposed in parallel via the diffraction grating. Therefore, a fiber grating having a length of m × L can be formed. Therefore, according to this manufacturing method, a longer fiber grating can be manufactured using a diffraction grating having a length of L. Specifically, it is assumed that the longest diffraction grating that can be formed by the conventional technique is, for example, 100 mm. According to the invention of the first manufacturing method, this 10
A mask having a diffraction grating in which m diffraction gratings each having a length of 0 mm are arranged in parallel can be used. Therefore, m × 100 m using a diffraction grating having a length of 100 mm
m fiber gratings can be manufactured.

In the first manufacturing method, when the diffraction grating of the mask to be used is a single-period grating, a single-period fiber grating having a length of m × L can be manufactured using a diffraction grating having a length of L. .

In the first manufacturing method, the diffraction grating of the mask to be used is the first to m-th parallel diffraction gratings prepared for an optical fiber for each of the m windings. When each of the first to m-th diffraction grating single-period gratings has an individual chirp grating so as to be a continuous chirp grating as the whole diffraction grating, the length is determined using a diffraction grating having a length of L. Can produce a m × L chirped fiber grating.

In the above description, the width of the diffraction grating is
It has been described that the width is equal to or greater than the width of m turns of the optical fiber, and the length of the diffraction grating is equal to or greater than the length L. This is because even if the length of the diffraction grating is longer than the length L, a diffraction grating equivalent to the distance L can be realized by controlling the rotation angle of the support member and the moving distance of the mask. However, when a chirped grating is used as the diffraction grating, the length of the diffraction grating is preferably L. This is because connection of the chirp gratings of the first to m-th diffraction gratings is facilitated.

Further, in carrying out the first manufacturing method, the following may be performed. That is, as an exposure mask, a mask having a plurality of diffraction gratings having a length of s × L or more arranged in parallel with an interval corresponding to s turns of the spirally wound optical fiber is prepared. Next, the mask and the support member are opposed to each other in such a positional relationship that the diffraction grating of the mask follows the tangent line of the wound optical fiber. Then, the mask is moved such that successive portions of the diffraction grating and successive portions of the optical fiber wound around the support member pass through the exposure light irradiation region by the distance of s × L. Exposure is performed while rotating the support member about its axis as a rotation center. In this case, exposure is performed in parallel in units of s windings of optical fiber. Therefore, it is possible to use a diffraction grating having a length of s × L and manufacture a fiber grating having a multiple of the length of the diffraction grating.

(2) In this application, the following method (referred to as a second manufacturing method) is also claimed as a method for manufacturing a fiber grating.

That is, in a method of manufacturing a fiber grating in which a photosensitive optical fiber is exposed through a mask having a diffraction grating to form a refractive index modulation section on the optical fiber, the photosensitive optical fiber is formed into a cylindrical shape. It is spirally wound around the support member. Further, as the mask, a mask having a single-period grating and a diffraction grating having a length of X is prepared. Then, insist on a method in which the mask is opposed to the optical fiber in a positional relationship such that the diffraction grating is along the tangent of the wound optical fiber, and thereafter, the following first and second processes are repeated as many times as necessary. .

(A) In such a manner that successive portions of the diffraction grating and successive portions of the optical fiber wound on the support member pass through the irradiation area of the exposure light by the length of the diffraction grating. While the movement of the mask and the rotation of the support member about the axis of rotation are performed, the width of the irradiation area along the axis is equivalent to two turns of the optical fiber wound in the spiral. With the exposure light squeezed so that it is less than the width,
A first process of performing the exposure;

(B) After finishing the first processing, the support member is rotated by 180 degrees relative to the mask around a line passing through the exposure end point position and perpendicularly intersecting the axis. Second processing to be performed.

According to the second manufacturing method, when the exposure through the diffraction grating having the length X is completed, the above-described rotation by 180 degrees is performed. For this reason, the next portion of the optical fiber spirally wound around the supporting member can be exposed through the diffraction grating having the length X. Therefore, according to the second manufacturing method, a single-period fiber grating longer than the diffraction grating having the length X can be manufactured.

(3) In this application, the following method (referred to as a third manufacturing method) is also claimed as a method for manufacturing a fiber grating.

That is, in a method of manufacturing a fiber grating in which a photosensitive optical fiber is exposed through a mask having a diffraction grating to form a refractive index modulation portion on the optical fiber, the photosensitive optical fiber is formed into a cylindrical shape. It is spirally wound around the support member. The masks may include first to m-th diffraction gratings arranged in parallel to each other and having a length of X, and each chirp grating may be an individual chirp grating so as to form a continuous chirped grating as a whole. A mask having first to m-th diffraction gratings having a grating is prepared. Then, the mask is opposed to the optical fiber in a positional relationship such that any one of the first to m-th diffraction gratings is along the tangent line of the wound optical fiber. Insist on how to repeat the process as many times as necessary. However, the order of the second processing and the third processing may be any order.

The mask is arranged so that successive portions of the diffraction grating and successive portions of the optical fiber wound on the supporting member pass through the irradiation area of the exposure light by the length of the diffraction grating. And the rotation of the support member around the axis of the support member, while the width of the irradiation area along the axis is equal to the width of the two spirally wound optical fibers. A first process of performing the above-mentioned exposure in a state where the exposure light is narrowed so as to be less than

After the first processing is completed, the support member is moved relative to the mask by a line segment passing through the exposure end point position and perpendicularly intersecting the axis with respect to the mask.
Second processing for rotating 0 degrees.

After the completion of the first processing, the mask and the support member are relatively moved so that the diffraction grating located next to the diffraction grating used so far for exposure faces the exposure end position. Third processing to be performed.

According to the third manufacturing method, when the exposure through the diffraction grating having the length X is completed, the above-described rotation by 180 degrees and the relative movement of the mask and the support member are performed. For this reason, exposure of the next appearing part of the optical fiber spirally wound on the support member can be performed using the first to m-th diffraction gratings in that order. Each of the first to m-th diffraction gratings may have a length of X. Therefore, this third
According to the manufacturing method described above, a longer chirped fiber grating can be manufactured using a diffraction grating having a length of X.

(4) In this application, the above-described first to first embodiments
The following supporting members are claimed as supporting members for easily implementing the third manufacturing method.

That is, a support member on a cylinder having a spiral groove for spirally winding a photosensitive optical fiber, the surface of which is substantially non-reflective with respect to exposure light for exposing the optical fiber. Claim the support member with the coating.

In order to carry out the above-described first to third manufacturing methods, it is necessary to spirally wind the photosensitive optical fiber around the support member at a predetermined lead angle. In such a case, according to the support member of the present invention, the above-mentioned winding can be easily realized.

Further, the support member is provided with a predetermined anti-reflection coating. Therefore, reflected light that does not contribute to the formation of the periodic refractive index modulation can be substantially eliminated.

In practicing the invention of the supporting member, it is preferable that the depth of the groove is larger than the diameter of the photosensitive optical fiber. This can prevent the photosensitive optical fiber from coming into contact with the mask. Therefore, the mask and the optical fiber can be protected. In addition, since the photosensitive optical fiber does not easily protrude from the groove, desired winding can be performed more favorably.

(5) In this application, a support member and
An optical filter comprising a fiber grating spirally wound around the support member.

According to this optical filter, an optical filter capable of storing a long fiber grating in a compact manner can be realized. Therefore, even when an optical filter using a long fiber grating is configured to realize characteristics such as the reflection wavelength band and the flatness of the top of the reflection spectrum, the size can be easily reduced.

The supporting member to be used is preferably of an elongated shape and a shape in which the fiber grating can be easily wound. A columnar support member or a polygonal columnar support member is preferable as the support member used.

In practicing the optical filter, it is preferable to use a support member having a spiral groove for winding the fiber grating as the support member. By doing so, the fiber grating can be wound along the groove, and advantages such as easy positioning and fixing of the fiber grating can be obtained.

The depth of the spiral groove provided in the support member is not particularly limited as long as the depth allows the positioning and fixing of the fiber grating. However, when the depth of the groove is made larger than the diameter of the fiber grating, an optical filter having a structure in which the fiber grating is hidden in the supporting member can be realized. If the fiber grating has a structure hidden in the support member, the protection of the fiber grating can be easily achieved. Further, for example, since a cylindrical cover that includes the support member can be mounted,
An advantage that the exterior of the optical filter can be completed easily can be obtained.

[0039]

Embodiments of the present invention will be described below with reference to the drawings. It should be noted that the drawings used in the description merely schematically show the structure, size, and positional relationship so that the present invention can be understood. Further, the conditions and materials such as numerical values described below are merely examples. Therefore, the present invention is not limited to this embodiment. In each drawing, the same components are denoted by the same reference numerals, and redundant description will be omitted.

1. Description of First Manufacturing Method An embodiment of a first manufacturing method of a fiber grating will be described. First, the photosensitive optical fiber 11 and the support member 13 will be described. FIG. 1 shows a cylindrical support member 13 and a photosensitive optical fiber 11 attached to the support member 13.
It is a figure explaining the state which wound each.

As the photosensitive optical fiber 11, for example, a photosensitive optical fiber called SMF28 (trade name) manufactured by Corning Incorporated is used. Of course, other photosensitive optical fibers may be used.

The coating layer (not shown) of the photosensitive optical fiber 11 is peeled off in advance to expose the cladding layer. The coating layer can be peeled off, for example, by using a jig such as a fiber stripper, or by immersing the fiber itself in dichloroethane to dissolve the coating layer. The peeling of the coating layer may be performed on the photosensitive optical fiber alone or after the optical fiber 11 is wound around the support member 13.

The support member 13 has a spiral groove 13a having a predetermined lead angle. The lead angle is a spiral groove 1
3a and the axis ab of the support member 13
(See FIG. 1).

The surface of the support member 13 is provided with a coating (not shown) which is substantially non-reflective to exposure light for producing a fiber grating. This coating can be realized by, for example, baking a black paint on the surface of the support member 13.

The width w and the depth d of the spiral groove 13a (see FIG. 2) can be arbitrarily set as long as the photosensitive optical fiber 11 can be positioned. However, the width of the groove 13a is preferably approximately the diameter of the optical fiber 11 (the diameter including the coating layer). Also, the depth of the groove 13a is preferably
The value is in the range of more than half the diameter of the optical fiber and less than the diameter. For example, if the diameter of the optical fiber 11 is 125 μm, the width of the groove 13a is set to 120 to 130 μm, and the depth of the groove 13a is set to 60 to 120 μm. FIG. 2 (A)
FIG. 4 is a diagram showing such a relationship between the groove 13a and the optical fiber 11.

If it is desired to reduce the risk of direct contact between the optical fiber 11 and the mask (see FIG. 3), the groove 13 is used.
The depth a is set to a value larger than the diameter of the optical fiber 11. FIG. 2B is a diagram showing such a relationship between the groove 13 a and the optical fiber 11.

The optical fiber 11 is wound around the support member 13 while the optical fiber 11 is inserted into the spiral groove 13a. The length of one turn of the wound optical fiber 11 (the length from P1 to P2 in FIG. 1) is L. That is, the distance traveled by the optical fiber 11 when the support member 13 is rotated once about the axis ab is L.

Next, the exposure mask will be described.
FIG. 3 is a plan view illustrating an example of the mask 15.

In this case, the mask 15 is composed of a substrate 15a transparent to exposure light and a diffraction grating 17 provided on this substrate.

The substrate 15a is made of any suitable substrate such as a synthetic quartz substrate.

The axis ab of the support member 13 of the diffraction grating 17
The width W0 along (see FIG. 1) is equal to or larger than the width of m turns of the optical fiber 13 spirally wound around the support member 13 (this width may be the same). In addition, the length of the diffraction grating 17 is set to be equal to or longer than the distance L, and in the case of this embodiment, the same length L as the distance L.

In addition, the diffraction grating 17 in this embodiment is composed of the first through the first parallel optical fibers 11 prepared for the optical fiber for each turn of the optical fiber 11 wound spirally.
The m-th diffraction gratings 17a to 17m each include a first to m-th diffraction gratings 17a to 17m having a length L. Here, each winding means that the support member 13 has its axis a
One turn when b makes one rotation around the rotation center,
In FIG. 1, it is a portion corresponding to a portion between P1 and P2.

Each of the first to m-th diffraction gratings 17a to 17m has an individual chirp grating so that the entire diffraction grating becomes a continuous chirp grating. Specifically, the first diffraction grating 17a
Is composed of, for example, n parts 17a1 to 17an. Here, n is an arbitrary integer. The first portion 17a1 has a structure in which a periodic structure having a length of Λ1 is repeated S1 times. Also, the second portion 17a2 is
The periodic structure having a length of Λ2 (Λ1 <Λ2) is repeated S2 times. The n-th portion 17an has a structure in which a periodic structure having a length of Λn (Λn-1 <Λn) is repeated Sn times. S1 to Sn may be the same or different.

Each of the above-described periodic structures is, for example, a structure in which concave portions and convex portions are connected so that the lengths are in a one-to-one ratio, as in the conventional case. This periodic structure can be formed by a known lithography technique and an etching technique. Hereinafter, the second diffraction grating 17b to the m-th diffraction grating 17m are configured by sequentially varying the length of the periodic structure.

The widths w1 to wm of the first to m-th diffraction gratings 17a to 17m are so narrow that no more than two turns of the helically wound optical fiber are opposed to the fiber. .

Next, how to arrange the support member 13 around which the optical fiber 11 is spirally wound and the mask 15 will be described.
These moving methods and the procedure of exposure will be described. FIG. 4 is an explanatory diagram thereof.

The mask 1 is positioned so that the longitudinal direction of the diffraction grating 17 of the mask 15 extends along the tangent (same as M in FIG. 1) of the optical fiber 11 spirally wound around the support member 13.
5 and the support member 13 are opposed to each other (see a plan view in FIG. 4). In addition, one end of the diffraction grating 17 in the longitudinal direction is opposed to the support member 13.

When one end of the diffraction grating 17 is opposed to the supporting member, in the example of FIG. 4, P1 and P2 shown at the right end of the mask 15 in FIG. 3 or the mask 15 in FIG. 3 is rotated by 180 degrees in the plane of the paper, and P3 and P4 shown on the left end of the mask 15 in FIG. 3 are the positions of the exposure region 19 in FIG. Any method may be used. Either method results in a chirped fiber grating.

Next, the mask 15 is moved so that successive portions of the diffraction grating 17 in the longitudinal direction and successive portions of the optical fiber 11 wound around the support member 13 pass through the exposure light irradiation area 19. Of the support member 13 and its axis a
and rotation about b as the center of rotation. In addition, these movements and rotations are such that successive portions of the diffraction grating 17 in the longitudinal direction and successive portions of the optical fiber 11 wound on the support member 13 pass through the irradiation area 19 by the distance L described above. Do as you do. Then, the optical fiber 11 is exposed through the mask 15 while performing such movement and rotation.

Successive portions of the diffraction grating 17 in the longitudinal direction;
In order to allow the successive portions of the optical fiber 11 wound around the support member 13 to pass through the irradiation area 19, the mask 15 must be parallel to the right in the figure in the initial state of the plan view of FIG. The support member 13 may be moved and rotated (rotated clockwise) in the direction of the arrow in FIG. However, by moving the mask 15, the diffraction grating 1
A mask moving device (not shown) and a support member rotating device (not shown) so that the distance traveled by 7 and the distance traveled by optical fiber 11 by rotating support member 13 are the same.
And are synchronized.

The width Wx of the exposure light irradiation area 19 in the direction along the axis ab of the support member 13 is set to be equal to or larger than the width of m optical fibers.

The optical system for performing the above exposure can be any suitable optical system. In this embodiment, a laser light source 21, an attenuator 23, a mirror 25, a beam expander 27, and a cylindrical lens 29 are provided.

As a laser light source 21, a KrF excimer laser manufactured by Lambda Physics Co., Ltd. is used. Laser light source 2
The beam diameter of the laser light emitted from 1 is expanded by the beam expander 27. Further, the light becomes the light indicating the desired irradiation area 19 described above by the cylindrical lens.

When the movement of the mask 15 and the rotation of the support member 13 around which the optical fiber 11 is wound are performed as described above, each wound portion of the spirally wound optical fiber becomes the first.
Exposure is performed in parallel by laser light via the corresponding one of the to the m-th diffraction gratings 17a to 17m.
For this reason, the diffraction fringes formed by the first to m-th diffraction gratings are irradiated onto the optical fiber 11 at one time, so that chirp gratings of Λ1 to Λmn are formed on the optical fiber 11. Therefore, a chirped fiber grating having a length of m × L can be manufactured despite the use of a diffraction grating having a length of L. FIG.
FIG. 3 is a diagram schematically illustrating a chirped fiber grating 30 manufactured in this manner.

Since the anti-reflection coating is applied to the surface of the support member 13 as described above, the extent to which the exposure light is reflected by the support member 13 in the above exposure step can be reduced. Therefore, it is possible to prevent the light reflected on the surface of the support member 13 from causing a useless change in the refractive index on the optical fiber.

Further, according to the manufacturing method of the present invention, since the operation can be performed with the optical fiber wound around the support member, the handling from the manufacturing process of the fiber grating to the process of obtaining the target element, for example, the wavelength filter, becomes easy. The effect is also obtained. In addition, there is an effect that packaging can be performed in a state where the support member and the optical fiber are integrated.

In the above description, an example in which a chirped fiber grating is manufactured has been described. However, the above-described manufacturing method can be applied to the case of manufacturing a single-period fiber grating. In that case, the first to m-th diffraction gratings 17a to 17m of the mask described with reference to FIG.
Each of them may be changed to a single-period grating.
Specifically, the periodic structures # 1 to #mn may have the same structure.

In the case of manufacturing a single-period fiber grating, the diffraction grating 17 is not divided into the first to m-th diffraction gratings 17a to 17m, but as shown in FIG. In some cases, an integrated diffraction grating having a width of? In this case, it is considered that the structure of the mask can be simplified as compared with the case of dividing into the first to m-th diffraction gratings.

In the above description, an example has been described in which any one of the first to m-th diffraction gratings is opposed to each turn of the optical fiber spirally wound around the support member. However, as shown in FIG. 7, a plurality of diffraction gratings 1 having a length of s × L or more, which are arranged in parallel with an interval corresponding to s turns of the optical fiber 11 spirally wound on the support member 13, are provided.
A mask 171 having 71a to 171j is prepared. Next, the mask 171 is attached to the tangent line of the wound optical fiber 11.
The mask 171 and the support member 13 are opposed to each other in such a positional relationship that the diffraction grating along the mask 171 follows. Then, the mask is moved such that successive portions of the diffraction grating and successive portions of the optical fiber wound on the supporting member pass through the irradiation area of the exposure light by the distance of s × L. Exposure may be performed while rotating the support member about the axis thereof as a rotation center. Rotation of support member 13 and mask 1
The movement of 71 may be performed in the same procedure as described with reference to FIG.

In such a case, a plurality of spirally wound portions of the optical fiber can be exposed in parallel, so that a fiber grating longer than the length of the diffraction grating can be manufactured.

2. Description of Second Manufacturing Method In the above description, a manufacturing method in which the length of the diffraction grating is equal to the length of one spirally wound optical fiber (FIG. 3) or longer (FIG. 7). Was explained. However, when the bendable radius at which the optical fiber can be bent without damaging it is small, it is necessary to use a cylindrical support member 13 having a large diameter. Then, the length of the diffraction grating may be shorter than the length of one spirally wound optical fiber. In such a case, the first manufacturing method described above cannot manufacture a desired fiber grating. This second manufacturing method is a method for manufacturing a fiber grating in which the measures are taken.

FIG. 8 shows a mask 3 used in the second manufacturing method.
FIG. 1 is a diagram illustrating a structure of a photosensitive optical fiber 11 and the like. 9 and 10 are manufacturing process diagrams.

The photosensitive optical fiber 11 is spirally wound around a cylindrical support member 13. However, optical fiber 1
The first coating layer (not shown) is peeled off to expose the cladding layer. Further, as the mask 31, a mask 31 having a diffraction grating 33 having a single period grating and a length of X is prepared.

Next, as shown in FIG. 9A, the tangential line of the optical fiber wound spirally around the support member 13 is
In a positional relationship such that the longitudinal direction of the diffraction grating 33 is along,
The mask 31 faces the optical fiber 11. Of course, one end of the diffraction grating 33 is located at the irradiation area (beam 3) of the exposure light.
The mask 31 is placed on the optical fiber 1 so as to match the position of 5).
1

However, the width of the region to be irradiated with the exposure light (irradiation region) along the axis is smaller than the width of two spirally wound optical fibers. That is, the diameter of the exposure light beam 35 is set to be slightly larger than, for example, the diameter of the optical fiber 11. In order to obtain such a beam, for example, an optical system in which the beam expander 27 is removed from the optical system described with reference to FIG.

Next, successive portions of the diffraction grating 33 and successive portions of the optical fiber 11 wound around the support member 13 by the length X of the diffraction grating 33 form an irradiation area (beam 3).
The movement of the mask 31 and the rotation about the axis line ab of the support member 13 are performed so as to pass through the region (the area hit by 5). In the case of this example, these movements and rotations are performed from right to left in FIG. 9A for the mask 31 and about the axis ab for the support member 13 in FIG.
(A) is rotated (clockwise) in the direction indicated by the arrow.

After the movement of the mask 31 and the rotation of the support member 13 are performed as described above, the exposure end point position P (FIG. 9)
The support member 13 is rotated by 180 degrees relative to the mask 31 about a line segment passing through the axis line ab and passing through the line perpendicular to the axis ab (see FIG. 10B) (FIG. 10A).

Next, successive portions of the diffraction grating 33 and new portions of the optical fiber 11 wound around the support member 13 are successively opposed by the length X of the diffraction grating 33. , The movement of the mask 31 and the axis a of the support member 13
Rotation is performed with b as the center of rotation (FIG. 10B). In the case of this example, these movements and rotations of the mask 31 move from left to right in FIG.
Is rotated about the axis ba in the direction of the arrow in FIG.

When such operations are repeated as many times as necessary, successive portions of the optical fiber can be exposed using one diffraction grating having a length of X. Therefore, a single-period fiber grating having a longer length than this diffraction grating can be manufactured.

3. Description of Third Manufacturing Method Next, an embodiment of the third manufacturing method will be described.
This third manufacturing method is a method particularly suitable for manufacturing a chirped fiber grating. 11 to 13 are explanatory diagrams thereof. FIG. 11 mainly shows the mask 41 and the diffraction grating 4.
3 and FIG. 12 and FIG. 13 are manufacturing process diagrams of the fiber grating.

The optical fiber 11 is spirally wound around the support member 13 in the same manner as in the previous embodiments.

As shown in FIG. 11, first to m-th diffraction gratings 43 arranged in parallel to each other are used as the mask 41.
A mask having a to 43 m is prepared. Each of the first to m-th diffraction gratings 43a to 43m has a length X, and
The width is less than the width of two turns of the spirally wound optical fiber. Needless to say, each of the diffraction gratings 43a to 43m has an individual chirp grating so as to be a continuous chirp grating.

The first to m-th diffraction gratings 43a to 43m are
Basically, it may be the same as the diffraction gratings 17a to 17m described in the embodiment of the first manufacturing method. However, the arrangement of the periodic structure is different from that of the first embodiment.

Specifically, the first diffraction grating 43a is composed of, for example, n parts 43a1 to 43an.
Here, n is an arbitrary integer. And the first part 4
3a1 is a structure in which a periodic structure having a length of Λ1 is repeated S1 times. The second portion 43a2 has a length of $ 2
The periodic structure (Λ1 <Λ2) is repeated S2 times. The n-th portion 43an has a length of Λn (Λn-
The periodic structure of 1 <周期 n) is repeated Sn times. S1 to Sn may be the same or different.

The second diffraction grating 43b is, for example,
It is composed of n parts 43b1 to 43bn. Here, n is an arbitrary integer. Then, the n-th part 43b
n is a structure in which a periodic structure having a length of Λn + 1 is repeated Sn + 1 times. The n-1st part 43bn-1 is
The periodic structure having a length of Λn + 2 is repeated Sn + 2 times. The first portion 43b1 has a structure in which a periodic structure having a length of Λ2n is repeated. That is, the first
Tracing the diffraction gratings 43a to 43m in a zigzag manner, such as tracing the diffraction grating from the left end to the right end and then tracing the second diffraction grating 43b from the right end to the left end, the chirped grating arrangement is obtained. , A periodic structure is arranged.

Next, as shown in FIG. 12A, the mask is placed in a positional relationship such that the longitudinal direction of the diffraction grating 43a extends along the tangent of the optical fiber spirally wound around the support member 13. 41 faces the optical fiber 11. Of course, one end of the diffraction grating 43a is the beam 35 of the exposure light.
The mask 41 is made to face the optical fiber 11 so as to coincide with the position.

Next, successive portions of the diffraction grating 43 and successive portions of the optical fiber 11 wound on the support member 13 pass the position of the beam 35 by the length X of the diffraction grating 43. Thus, the movement of the mask 41 and the rotation about the axis ab of the support member 13 as the center of rotation are performed. In the case of this example, the movement and rotation of the mask 41 are performed from right to left in FIG. 12A, and the support member 13 is rotated about the axis ab in the direction indicated by the arrow in FIG. Clockwise).

After the movement of the mask 41 and the rotation of the support member 13 are performed as described above, the exposure end point position P (FIG. 12)
(B), the support member 13 is rotated by 180 degrees relative to the mask 41 about a line segment that intersects the axis ab perpendicularly to the axis ab (FIG. 12C, FIG. 13).
(A)).

Next, the diffraction grating 43a used for the exposure
, Ie, in this case, the second diffraction grating 43b is located at the exposure end position P of the optical fiber 11.
The mask 41 and the support member 13 are relatively moved in the y-direction (FIG. 13B) so as to face.

Next, successive portions of the diffraction grating 43b and successive portions of the optical fiber 11 wound around the support member 13 pass the position of the beam 35 by the length X of the diffraction grating 43b. As described above, the movement of the mask 41 and the rotation about the axis ba of the support member 13 are performed. In the case of this example, these movements and rotations are performed from the left to the right in FIG. 13B for the mask 41, and the direction of the arrow in FIG. Rotate to.

When such operations are repeated as many times as necessary,
Successive new portions of the optical fiber can be exposed by using the to m-th diffraction gratings 43a to 43m one after another. Therefore, a chirped fiber grating having a longer length than the diffraction grating can be manufactured using the diffraction grating having the length X.

The third manufacturing method can be applied to a case where a single-period fiber grating is manufactured. In that case, each of the first to m-th diffraction gratings 43a to 43m is changed to a single-period grating. That is, the periodic structures # 1 to #mn have the same structure.

[0093]

According to the fiber grating manufacturing method of the present invention, the photosensitive optical fiber is spirally wound around the cylindrical support member. Then, the mask and the support member are opposed to each other in such a positional relation that the diffraction grating of the exposure mask follows the tangent line of the wound optical fiber. And
The movement of the mask and the axis of the support member, with the axis of rotation being the center of rotation so that successive portions of the diffraction grating and successive portions of the optical fiber wound on the support member pass through the irradiation area of the exposure light. The optical fiber is exposed through a mask while performing a rotation.

Therefore, m turns of the optical fiber can be exposed in parallel by using a mask having a width greater than or equal to the width of the m turns of the optical fiber and having a diffraction grating having a length of L. In such a case, a fiber grating having a length of m × L can be manufactured with a diffraction grating having a length of L.

Further, the optical fibers can be exposed in parallel using a mask in which diffraction gratings having a length of s × L are arranged in parallel at intervals corresponding to s turns of the optical fibers. In such a case, a fiber grating having a length of s × L and a length several times that of a diffraction grating can be manufactured.

Further, the optical fiber spirally wound around the support member is exposed for a length X using a diffraction grating having a length X, and then the relative position between the support member and the diffraction grating is determined. Is changed by 180 degrees and exposure for the length X is performed again (second and third manufacturing methods). In these cases,
A fiber grating having a length longer than X can be manufactured with a diffraction grating having a length X.

Therefore, according to each manufacturing method of this application, a fiber grating longer than the length of the diffraction grating can be easily manufactured.

Further, according to each method of manufacturing the fiber grating of the present application, the effect that the optical filter including the supporting member and the fiber grating spirally wound around the supporting member can be easily manufactured is further obtained. Can be

Further, according to the invention of the optical filter of the present application, the optical filter includes the support member and the fiber grating spirally wound around the support member. Therefore, even when an optical filter using long fiber grating is configured to realize characteristics such as the reflection wavelength band and the flatness of the top of the reflection spectrum, the size can be easily reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a photosensitive optical fiber and a support member.

FIG. 2 is an explanatory diagram of a spiral groove provided in a support member.

FIG. 3 is an explanatory diagram of a mask and a diffraction grating used in the embodiment of the first manufacturing method.

FIG. 4 is an explanatory diagram of a positional relationship between a mask and a support member.

FIG. 5 is an explanatory diagram of a fiber grating manufactured by the manufacturing method of the present invention.

FIG. 6 is an explanatory diagram of a first modification of the first manufacturing method.

FIG. 7 is an explanatory view of a second modification of the first manufacturing method.

FIG. 8 is an explanatory diagram of a mask and the like used in a second manufacturing method.

FIG. 9 is a process chart of an embodiment of the second manufacturing method.

FIG. 10 is a process drawing following the FIG. 9 of the embodiment of the second manufacturing method;

FIG. 11 is a diagram illustrating a mask and a diffraction grating used in a third manufacturing method.

FIG. 12 is a process chart of an embodiment of a third manufacturing method.

FIG. 13 is a process drawing following the FIG. 12 of the embodiment of the third manufacturing method.

[Explanation of symbols]

 11: photosensitive optical fiber 13: cylindrical support member 13a: spiral groove 15: mask 17: diffraction grating 17a to 17m: first to m-th diffraction grating 19: exposure light irradiation area 31: mask 33: Length X diffraction grating 35: Irradiation area (beam) of exposure light P: Exposure end position 41: Mask 43a to 43m: First to mth diffraction grating 171: Mask 171a to 171j: Diffraction grating

Claims (22)

[Claims] 1. A method of manufacturing a fiber grating, comprising exposing a photosensitive optical fiber through a mask having a diffraction grating to form a refractive index modulation section on the optical fiber. Spirally wound around the supporting member, and the mask and the supporting member are opposed to each other in a positional relationship such that the diffraction grating of the mask follows the tangent line of the wound optical fiber, and successive portions of the diffraction grating The mask is moved and the support member is rotated about its axis so that the successive portions of the optical fiber wound around the support member pass through the irradiation area of the exposure light. A method of manufacturing the fiber grating, wherein the exposure is performed while performing the exposure. 2. The method for manufacturing a fiber grating according to claim 1, wherein the mask has a width not less than a width corresponding to m turns of the spirally wound optical fiber, and the support member is centered on an axis thereof. A mask having a diffraction grating having a length equal to or longer than the distance L of the optical fiber that advances when rotated once is prepared in a positional relationship such that the diffraction grating of the mask follows the tangent of the wound optical fiber. The mask and the supporting member are opposed to each other, and the successive portion of the diffraction grating and the successive portion of the optical fiber wound on the supporting member pass through the irradiation area of the exposure light by the distance L. A method of manufacturing a fiber grating, wherein the exposure is performed while moving the mask and rotating the support member about the axis thereof as a rotation center (where m is 2 or more). Is an integer.). 3. The method for manufacturing a fiber grating according to claim 2, wherein the diffraction grating is a first to m-th parallel diffraction grating prepared for an optical fiber for each of the m windings. A method for manufacturing a fiber grating, comprising: first to m-th diffraction gratings each having an individual chirp grating so that the entire diffraction grating becomes a continuous chirp grating. 4. The method for manufacturing a fiber grating according to claim 2, wherein the diffraction grating is a first to m-th parallel diffraction grating prepared for an optical fiber for each of the m windings. A method of manufacturing a fiber grating, comprising first to m-th diffraction gratings each having a single-period grating. 5. The method of manufacturing a fiber grating according to claim 2, wherein the diffraction grating has a single-period grating, and has a width equal to or greater than the width of the m turns, and is an integral type. A method for manufacturing a fiber grating, comprising a diffraction grating. 6. The method for manufacturing a fiber grating according to claim 1, wherein the mask has a length of s × arranged in parallel with an interval corresponding to s turns of the spirally wound optical fiber. A mask having a plurality of L or more diffraction gratings is prepared, and the mask and the support member are opposed to each other in such a positional relationship that the diffraction grating of the mask follows the tangent line of the wound optical fiber. Moving the mask so that successive portions of the diffraction grating and successive portions of the optical fiber wound on the support member pass through the irradiation area of the exposure light by a distance of L; A method of manufacturing the fiber grating, wherein the exposure is performed while rotating about the axis of the support member (L is one rotation about the axis of the support member). Distance of the optical fiber traveling at a, s is an integer of 2 or more.). 7. The method of manufacturing a fiber grating according to claim 6, wherein each of the plurality of diffraction gratings is a diffraction grating having a single period grating. 8. The method of manufacturing a fiber grating according to claim 6, wherein each of the plurality of diffraction gratings has an individual chirp grating so that the entire diffraction grating becomes a continuous chirp grating. A method for manufacturing a fiber grating. 9. A method of manufacturing a fiber grating, comprising exposing a photosensitive optical fiber through a mask having a diffraction grating to form a refractive index modulation section on the optical fiber. Spirally wound around the supporting member, a mask having a single-period grating and a diffraction grating having a length of X is prepared as the mask, and the diffraction grating is arranged along the tangent of the wound optical fiber. A method for manufacturing a fiber grating, wherein the mask is opposed to the optical fiber in a suitable positional relationship, and thereafter the following first and second processes are repeated as many times as necessary. (A) The mask so that successive portions of the diffraction grating and successive portions of the optical fiber wound around the support member pass through the irradiation area of the exposure light by the length of the diffraction grating. And the rotation of the support member around the axis of the support member, while the width of the irradiation area along the axis is smaller than the width of two turns of the optical fiber wound around the spiral. A first process of performing the exposure with the exposure light being narrowed so that (B) after completing the first processing, rotating the support member by 180 degrees relative to the mask around a line segment passing through the exposure end point position and perpendicularly intersecting the axis. Processing. 10. A method of manufacturing a fiber grating, comprising exposing a photosensitive optical fiber through a mask having a diffraction grating to form a refractive index modulation section on the optical fiber. The first to m-th diffraction gratings arranged in parallel with each other and each having a length of X as the mask, and chirped gratings continuous as a whole of the diffraction gratings. A mask having first to m-th diffraction gratings each having an individual chirped grating is prepared so that any one of the first to m-th diffraction gratings is tangent to the wound optical fiber. The mask is made to face the optical fiber in such a positional relationship as to be aligned, and then the first
And a method of manufacturing a fiber grating characterized by repeating the third to the required number of times (however, the order of the second and third processes may be any order). Movement of the mask by the length of the diffraction grating so that successive portions of the diffraction grating and successive portions of the optical fiber wound around the support member pass through the irradiation area of the exposure light. While rotating the support member about its axis as a rotation center, the width of the irradiation area along the axis is smaller than the width of the optical fiber wound around the spiral by two turns. A first process of performing the above-mentioned exposure with the exposure light being narrowed down. After the first process, a second process of rotating the support member by 180 degrees relative to the mask around a line segment passing through the exposure end point position and intersecting the axis perpendicular to the axis. After finishing the first process, the mask and the support member are relatively moved so that the diffraction grating located next to the diffraction grating used for the exposure is opposed to the exposure end position. Processing. 11. A cylindrical support member having a spiral groove for spirally winding a photosensitive optical fiber, the surface of which is substantially non-reflective for exposure light for exposing the optical fiber. A support member having a coating. 12. The support member according to claim 11, wherein a depth of the groove is larger than a diameter of the optical fiber. 13. A mask used for exposing a photosensitive optical fiber through a mask having a diffraction grating to form a refractive index modulation section on the optical fiber, wherein the diffraction grating is an optical fiber. Is spirally wound around a cylindrical support member, the width of the wound optical fiber is equal to or greater than the width of m turns, and the distance of the optical fiber that travels when the support member is rotated once around its axis. A mask characterized by having a diffraction grating having a length of L or more. 14. The mask according to claim 13, wherein the diffraction gratings are first to m-th parallel diffraction gratings prepared for an optical fiber for each of the m windings. A mask comprising: first to m-th diffraction gratings each having an individual chirp grating so that the entire diffraction grating becomes a continuous chirp grating. 15. The mask according to claim 13, wherein the diffraction gratings are first to m-th parallel diffraction gratings provided for an optical fiber for each of the m windings. Comprises a first to an m-th diffraction grating having a single-period grating. 16. The mask according to claim 13, wherein the diffraction grating has a single-period grating, and has a width equal to or greater than the width W of the m turns, and is formed from an integral diffraction grating. A mask characterized in that: 17. A mask used for exposing a photosensitive optical fiber through a mask having a diffraction grating to form a refractive index modulation section on the optical fiber, wherein the diffraction grating comprises the optical fiber. Characterized by comprising a plurality of diffraction gratings having a length of s × L or more arranged in parallel with an interval of s windings when spirally wound around a cylindrical support member. 18. The mask according to claim 17, wherein each of the plurality of diffraction gratings is a diffraction grating having a single period grating. 19. The mask according to claim 17, wherein each of the plurality of diffraction gratings is a diffraction grating having an individual chirp grating so that the entire diffraction grating becomes a continuous chirp grating. The featured mask. 20. An optical filter, comprising: a support member; and a fiber grating spirally wound around the support member. 21. The optical filter according to claim 20, wherein the support member has a spiral groove for winding the fiber grating, and the fiber grating is wound along the groove. An optical filter characterized by the above-mentioned. 22. The optical filter according to claim 21, wherein the depth of the groove is larger than the diameter of the optical fiber.