JP3334417B2 - Method and apparatus for producing optical waveguide type diffraction grating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for forming an optical waveguide type diffraction grating in which a diffraction grating is formed on a core of an optical waveguide such as an optical fiber or a thin film slab waveguide by irradiating the core with ultraviolet light.

[0002]

2. Description of the Related Art An optical waveguide type diffraction grating has a Bragg diffraction grating formed on the core of an optical waveguide. For example,
In a glass optical fiber, a core doped with Ge etc.
It is known that irradiation with ultraviolet light having a wavelength of about 240 nm from the side in the axial direction of the core causes a GeE ′ defect and increases the refractive index of the core. Light propagating in the core is reflected at this portion. I do. By providing the portions to be irradiated with ultraviolet rays at equal intervals in the axial direction of the core, it is possible to form the refractive index increasing portions periodically in the axial direction of the core, and selectively reflect light having a wavelength corresponding to this period. Diffraction grating can be obtained.

The optical waveguide type diffraction grating can be used as a reflection filter that reflects only light of a specific wavelength, and is expected to be widely used for wavelength control elements, sensor elements, and the like. Above all, fiber gratings using optical fibers as optical waveguides are important because they have good connectivity with optical fibers used as transmission lines.

[0004] As a method of producing an optical waveguide type diffraction grating,
There is known a method of projecting an ultraviolet interference pattern from the side of a core to which Ge or the like is added and spatially forming a refractive index change at an arbitrary period, such as a two-beam interference method, a prism interference method, and a phase grating interference method. Have been.

When irradiating such a core with ultraviolet rays from the side, it is necessary to position the optical waveguide in order to irradiate the core with ultraviolet rays efficiently.

[0006] When ultraviolet rays are irradiated on a core to which Ge or the like is added, fluorescence is generated from the core. R.
Atkins, "Control of Defect
sin Optical Fibers-A Stud
y Using Cathodoluminescen
ce Spectroscopy ", IEEE, J. et al.
Of Lightwave Tech. , 11 [1
1], 1993-11, pp. 1793-1801. The spectrum distribution of the generated fluorescence is distributed in the range of 350 to 750 nm including the tail portion, and particularly in the region of high intensity is in the range of 350 to 550 nm.

[0007] In the prior art, utilizing this fluorescence,
When the operator irradiates ultraviolet rays from the side of the core, the operator observes the scattering pattern of the fluorescence on the side of the core, and arranges the optical waveguide at a position where the contrast of the pattern becomes maximum.

However, since the operator observes the contrast of the scattering pattern, the standard for arranging the scattering pattern at the optimum position is ambiguous, and a difference in judgment is likely to occur depending on the operator. I needed it.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and it is easy to position an optical waveguide for efficiently irradiating a core with ultraviolet rays, and it is possible to automate the optical waveguide type diffraction. It is an object of the present invention to provide a grid creation method and a creation device.

[0010]

According to the first aspect of the present invention, a plurality of refractive index changes in the optical axis direction of the core are provided by irradiating ultraviolet rays from the side of the core of the optical waveguide. In the method of forming an optical waveguide type diffraction grating that forms a portion, when irradiating the core with the ultraviolet light, the core receives the fluorescent light propagating along the core and positions the optical waveguide such that the amount of received light is maximized. It is characterized by the following.

According to a second aspect of the present invention, in the method of manufacturing an optical waveguide type diffraction grating according to the first aspect, the interval between the refractive index changing portions changes along the optical axis of the core. It is characterized by the following.

According to a third aspect of the present invention, in the method of manufacturing an optical waveguide type diffraction grating according to the first or second aspect, of the fluorescent light, the fluorescent light having a wavelength in a range of 350 to 750 nm is received. It is a feature.

According to a fourth aspect of the present invention, in the method of manufacturing an optical waveguide type diffraction grating according to the first or second aspect, of the fluorescent light, a fluorescent light having a wavelength in a range of 350 to 550 nm is received. It is a feature.

According to the fifth aspect of the present invention, by irradiating ultraviolet rays from the side of the core of the optical waveguide, a plurality of refractive index changing portions are formed in the optical axis direction of the core. An optical system that irradiates ultraviolet light, a photodetector that receives fluorescence from an end face of the core, a holding unit of the optical waveguide, and a moving mechanism unit that moves the holding unit according to an output of the photodetector. It is characterized by having.

According to a sixth aspect of the present invention, in the optical waveguide type diffraction grating forming apparatus according to the fifth aspect, the moving mechanism has a translation axis in a direction perpendicular to an optical axis of the core. It has a linear motion mechanism.

According to a seventh aspect of the present invention, in the apparatus for producing an optical waveguide type diffraction grating according to the fifth or sixth aspect, the moving mechanism section is configured to rotate around an axis perpendicular to an optical axis of the core. It has a rotating mechanism that rotates.

[0017]

According to the first aspect of the present invention, in the method of fabricating an optical waveguide type diffraction grating, when irradiating the core with ultraviolet rays, the core receives the fluorescence propagating along the core so that the amount of received light is maximized. Since the optical waveguide is positioned at
Positioning information can be quantitatively grasped, and the positioning of the optical waveguide for efficiently irradiating the core with ultraviolet rays can be easily performed.

According to the second aspect of the present invention, since the interval between the refractive index changing portions changes along the optical axis of the core, a chirped grating can be formed.

According to the third or fourth aspect of the present invention,
The wavelength is in the range of 350 to 750 nm,
By receiving light in the range of 550 nm, detection accuracy can be improved.

According to a fifth aspect of the present invention, in the optical waveguide type diffraction grating producing apparatus, an optical system for irradiating ultraviolet rays, a photodetector for receiving fluorescence from an end face of the core, a holding section for the optical waveguide, Since it has a moving mechanism that moves the holding part according to the output of the photodetector, positioning information can be quantitatively grasped, and positioning of the optical waveguide for efficiently irradiating the core with ultraviolet light is easy. Can do it.

According to the sixth aspect of the present invention, since the moving mechanism section has a linear motion mechanism having a linear motion axis in a direction perpendicular to the optical axis of the core, the moving mechanism section is perpendicular to the optical axis of the core. The distance between the holding unit and the optical system in the direction can be optimized.

According to the seventh aspect of the present invention, since the moving mechanism has a rotating mechanism that rotates around an axis perpendicular to the optical axis of the core, the moving mechanism has a direction perpendicular to the optical axis of the core. The angle formed by the holding portion and the optical system around the axis of the optical system can be optimized.

[0023]

FIG. 1 is a schematic structural view of a main part of an apparatus for producing an optical waveguide type diffraction grating according to the present invention. In the figure, 1 is an optical fiber, 2 is an optical system, 3 is a holder, 4 is a φ stage, and 5 is Y
A stage, 6 is an X stage, 7 is a θ stage, and 8 is a photodetector. The core of the optical fiber 1 is doped with Ge. An ultraviolet irradiator is disposed on the side of the optical fiber 1, and is composed of a laser light source (not shown) that generates ultraviolet light and an optical system 2 that is adjacent to the laser light source and generates a specific irradiation pattern. The optical fiber 1 is
The core is attached to and held by a holder 3 having a predetermined length in the optical axis direction. The illustrated Z-axis direction is the longitudinal direction of the core, that is, the direction of the optical axis, and the illustrated X-axis direction is the direction in which the optical system 2 is arranged.

The φ stage 4, Y stage 5, X stage and θ stage 7 constitute a stage system. This stage system is, for example, manually or electrically driven by a moving mechanism.
It moves linearly in the axial direction and can rotate at an arbitrary angle about two axes. The holder 3 is attached to the φ stage 4. The φ stage 4 rotates around the illustrated X axis, and is attached to the Y stage 5. The Y stage 5 moves linearly in the axial direction of the illustrated Y axis.
It is attached to the X stage 6. X stage 6
It moves linearly in the axial direction of the X-axis shown in FIG.
Attached to. stage 7 rotates around the illustrated Y axis.

On one end face of the optical fiber 1, a photodetector 8 such as an optical power meter is provided. Optical fiber 1
It is desirable that the other end face be a reflection end or a non-reflection end.

A method for producing an optical waveguide type diffraction grating using the above-described apparatus will be described. First, the stage system is linearly and / or rotationally moved for coarse adjustment so that the light source and the optical system 2 are positioned almost laterally of the optical fiber 1. Next, a laser beam is generated, and the core of the optical fiber 1 is irradiated with a specific irradiation pattern through the optical system 2. In this case, the intensity of the laser light is set to be weak enough that a diffraction grating is not substantially formed. The irradiation of the laser beam generates fluorescence in the core.

Of the generated fluorescent light, those having an angle smaller than the aperture angle of the optical fiber 1 propagate through the core. This fluorescence is received by a photodetector 8 such as an optical power meter provided on one end face of the optical fiber 1. Then, finely adjust the stage system by linear movement and / or rotational movement,
The holder 3, that is, the optical fiber 1 can be positioned so that the amount of light received by the photodetector 8 is maximized. Due to this fine adjustment of positioning, when forming a diffraction grating,
Ultraviolet rays can be efficiently irradiated to the core.

At the time of the fine adjustment, for example, the stage system can be moved in the Z-axis direction and rotated ω around the Z-axis. Even when the amount of light received by the photodetector 8 does not change even when the amount of light received by the core is maximized, fine adjustment is performed such that the optical axis direction of the core completely matches the Z-axis direction. May be performed. That is, linear movement is performed in the X-axis direction and Y-axis direction perpendicular to the optical axis direction of the core, or rotation is performed about these axes, so that the fine adjustment state is obtained. And the holder 3, that is, the optical fiber 1, so that the amount of light received by the photodetector 8 does not change even if it is rotated about the Z axis.
By positioning the core, the core can be efficiently irradiated with ultraviolet rays.

In this manner, after the position of the holder 3 is located at the optimum position with respect to the optical system 2, the position of the holder 3 is fixed, and the core is irradiated with a specific irradiation pattern for a predetermined time. A refractive index change portion where the refractive index has a sufficiently large value is formed. Note that the photodetector 8 such as an optical power meter can output the amount of received light as a numerical value, so that the positioning can be automated.

In the above-described embodiment, in the positioning step, the intensity of the ultraviolet light to be irradiated is reduced, and the intensity of the ultraviolet light to be irradiated is increased after being adjusted to the optimum position in a state where the refractive index change portion is not formed. If the time for fine adjustment does not matter with respect to the irradiation time for forming the refractive index change portion, the intensity of the ultraviolet light may be increased from the beginning.

Although the photodetector 8 may receive all the fluorescence, it passes through an optical filter (not shown) and has a wavelength of 350-7.
Fluorescence generated in the core can be detected by detecting light in the range of 50 nm. Further, by narrowing the wavelength range of the light to be detected to the range of 350 to 550 nm, it is possible to selectively receive the fluorescence in the wavelength region where the generated intensity is high, and it is possible to enhance the detection accuracy.

FIG. 2 is an explanatory diagram of an optical system using a cylindrical lens. In the figure, the same parts as those in FIG. 1a is a core, 11 is a laser beam, and 12 is a cylindrical lens. This figure is
This shows a case where a cylindrical lens 12 is provided on the exit side of the optical system 2. The cylindrical lens 12
It has an axis parallel to the optical axis of the core 1a, and focuses the interference pattern of the laser 11 passing therethrough on the core 1a. The cylindrical lens 12 may be provided on the incident side of the interference optical system. Further, it is not always necessary to provide a focusing optical system.

The laser beam 11 on which a specific irradiation pattern is formed in the optical system 2 is focused by a cylindrical lens 12 and enters the optical fiber 1 from the side. And
A refractive index change is caused in the Ge-added core 1a.

When the distance in the X-axis direction between the holder 3 on which the optical fiber 1 is mounted and the optical system 2 is appropriate, the laser beam 11 passing through the optical system 2 is focused at the position of the core 1a. Thus, the core 1a can be efficiently irradiated with the laser beam 11. At this time, the photodetector 8 shown in FIG.
The amount of received light of the fluorescent light detected by becomes the largest.

The laser beam 11 may be focused on the core 1a by using means other than the cylindrical lens 12, and it is not always necessary to focus the laser beam 11 on the core 1a. Even in such a case, it is necessary to position the optical waveguide for efficiently irradiating the core with the laser light,
The core 1a of the optical fiber 1 is positioned so that the amount of light received by the photodetector 8 is maximized.

FIG. 3 is a configuration diagram illustrating a two-beam interference method as an example of an optical system. In the figure, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof is omitted. 11 is a laser beam, 13 is a beam splitter, and 14 and 15 are mirrors. In addition, about the Ge addition core of the optical fiber 1,
The illustration is omitted, and the refractive index change portion of the core is the optical fiber 1
Are schematically described as partial vertical stripes.

Ultraviolet rays having a wavelength of about 240 nm causing a change in the refractive index to the Ge-doped core are irradiated as laser light 11. The laser beam 11 is split into two by a beam splitter 13 and reflected by mirrors 14 and 15, respectively.
The light is irradiated on the side surface of the optical fiber 1 via the cylindrical lens 12. The split laser light interferes at the core of the optical fiber 1 and irradiates the core with interference fringes. In the core portion of the optical fiber 1, the refractive index changes in a pattern corresponding to the interference fringes, and a diffraction grating is formed.

FIG. 4 is a configuration diagram illustrating a prism interference method as an example of an optical system. 1, 2 and 4 in the figure.
The same reference numerals are used for the same parts as those described above, and the description is omitted. 1
6 is a prism. The laser light 11 is applied to the prism 16
Irradiate the surface. The interference fringes generated by refraction in the prism 16 are transmitted through the cylindrical lens 12 to the optical fiber 1.
Irradiate the core part of In the core portion of the optical fiber 1, the refractive index changes in a pattern corresponding to the interference fringes, and a diffraction grating is formed.

FIG. 5 is a configuration diagram illustrating a phase grating interferometry as an example of an optical system. 1, 2 and 4 in the figure.
The same reference numerals are used for the same parts as those described above, and the description is omitted. 1
7 is a phase grating. The laser beam 11 passes through the phase grating 17 and the cylindrical lens 12 in order and irradiates the core of the optical fiber 1. The phase grating 17 causes a change in the refractive index of the core portion of the optical fiber 1 in a pattern corresponding to the grating interval, thereby forming a diffraction grating.

The optical system 2 described with reference to FIGS. 3 to 5 generates a specific pattern by using light interference. Of course, the present invention is not limited to the above-described optical system, and a diffraction grating can be formed in an optical waveguide using an appropriate optical system. The grating intervals of the diffraction gratings created in the above-described embodiments are equally spaced, and exhibit reflection characteristics at a specific wavelength.

With respect to such equally spaced diffraction gratings, the spacing between the above-mentioned refractive index changing portions is changed in the optical axis direction of the core, in other words, the grating spacing of the diffraction grating is shifted in the longitudinal direction of the fiber. That is, a chirped grating to be chirped has been proposed.
cal Fiber CommunicationCo
nreference '94, postdeadline
paper-2, known as PD2-1 to PD2-4.

According to this chirped grating,
The light reflection position can be shifted in the longitudinal direction of the fiber according to the reflection wavelength. Therefore, the time required for the signal light incident from one end face of the optical fiber to be reflected and returned can be varied according to the wavelength. Such a chirped grating can widen the wavelength region that can be reflected, and can be used for compensating chromatic dispersion of a transmission line.

In order to create a chirped grating, it is necessary to employ an optical system different from the optical systems illustrated in FIGS. 3 to 5, but the apparatus described with reference to FIG. Even when a chirped grating is produced, the optical waveguide can be used in the same manner, and the optical waveguide can be arranged at a position where the core can be efficiently irradiated with ultraviolet rays.

In the above description, the holder 3 is moved linearly and / or rotationally. However, the holder 3 and the optical system 2 may be moved relative to each other. Fixed, moving the optical system 2 side, or moving one of them as appropriate according to the axial direction and the rotation axis,
Both may be moved simultaneously.

In the above description, an optical fiber is used as the optical waveguide. However, the optical waveguide type diffraction grating according to the present invention can be used even when a diffraction grating is formed on a core such as a slab waveguide used in an optical IC circuit or the like. The method and apparatus for creating a grid can also be implemented.

[0046]

As is apparent from the above description, according to the present invention, positioning information can be quantitatively grasped, optimal positioning of the optical waveguide is easy, there is no difference in judgment by the operator, and automation is possible. The effect is that it is possible.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part of an apparatus for producing an optical waveguide type diffraction grating of the present invention.

FIG. 2 is an explanatory diagram of an optical system using a cylindrical lens.

FIG. 3 is a configuration diagram illustrating a two-beam interference method as an example of an optical system.

FIG. 4 is a configuration diagram illustrating a prism interference method as an example of an optical system.

FIG. 5 is a configuration diagram illustrating a phase grating interferometry as an example of an optical system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical fiber, 2 ... Optical system, 3 ... Holder, 4 ... φ stage, 5 ... Y stage, 6 ... X stage, 7 ... theta stage, 8 ... Photodetector, 11 ... Laser light, 12 ... Cylindrical lens.

Continuing from the front page Examiner Hideo Sasano (56) References JP-A-7-281043 (JP, A) WO 94/17448 (WO, A2) ATKINS, Graham R. et al. , Control of Defects in Optical Fibers-A Study Using Cathodolumines Sense Spectroscopy, JOURNAL OF LIGHT WAVE TECHNOLOGY, USA, 1993, USA, Japan, 1993. 11 NO. 11, p. 1793-1801 GALLAGHER, M et al. , Time resolved 3.10 eV luminescense in germanium-doped silica glass, Applied Physics Letters, USA, American Institution of Physics, 1993, 29/11, 1993. 63, p.p. 2987-2989 (58) Fields surveyed (Int. Cl. ⁷ , DB name) G02B 6/00-6/02 G02B 6/10 G02B 6/16-6/22 G02B 6/44 JICST file (JOIS) IEEE / IEEE Electronic Library

Claims (7)

(57) [Claims] 1. A method of producing an optical waveguide type diffraction grating in which a plurality of refractive index changing portions are formed in a direction of an optical axis of the core by irradiating ultraviolet rays from a side of the core of the optical waveguide. A method for producing an optical waveguide type diffraction grating, comprising: when irradiating ultraviolet rays, receiving fluorescence propagating along the core and positioning the optical waveguide so that the amount of received light is maximized. 2. An apparatus according to claim 1, wherein an interval between the refractive index changing portions changes along an optical axis of the core.
3. The method for producing an optical waveguide type diffraction grating according to 1. 3. The fluorescence has a wavelength of 350 to 750.
2. The method according to claim 1, wherein the fluorescent light in a range of nm is received.
Or the method for producing an optical waveguide type diffraction grating according to 2. 4. The wavelength of the fluorescence is 350 to 550.
2. The method according to claim 1, wherein the fluorescent light in a range of nm is received.
Or the method for producing an optical waveguide type diffraction grating according to 2. 5. An apparatus for producing an optical waveguide type diffraction grating which forms a plurality of refractive index changing portions in an optical axis direction of the core by irradiating ultraviolet rays from a side of a core of the optical waveguide. An optical system comprising: an optical system, a photodetector that receives fluorescence from an end face of the core, a holding unit of the optical waveguide, and a moving mechanism unit that moves the holding unit according to an output of the photodetector. Wave path type diffraction grating preparation device. 6. The apparatus according to claim 5, wherein the moving mechanism has a linear motion mechanism having a linear motion axis in a direction perpendicular to the optical axis of the core. . 7. The optical waveguide type diffraction grating according to claim 5, wherein the moving mechanism has a rotation mechanism that rotates around an axis perpendicular to an optical axis of the core. apparatus.