JP3231238B2 - Optical fiber and method of manufacturing optical fiber 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 for manufacturing an optical waveguide used as an identification code for identifying an optical line used for optical communication at an end thereof, and a method for manufacturing an optical waveguide type diffraction grating.

[0002]

2. Description of the Related Art As a method for identifying an optical line, the refractive index of a core of the optical line is partially changed, and the position of this change is referred to as OTDR.
A method of detecting at the end of a line using a measuring method is known (The 1991 Autumn Meeting of the Institute of Electronics, Information and Communication Engineers, Document B-59).
1 "Remote fiber identification method for optical line database").

[0003]

However, according to this method, the identification code portion provided on the optical line extends over several hundred meters. For example, in the example in the above-mentioned document, recording an 8-bit identification code on an optical line requires 50 m per bit and a total length of 400 m. Therefore, it is difficult to attach an identification code to an optical line having a short length. Also, in order to record an identification code over several hundred meters on an optical line, this must be performed during the manufacturing process of the optical line, which is not practical.

In order to solve such a problem, it is conceivable to use an optical waveguide type diffraction grating as an identification code. As a method of manufacturing an optical waveguide type diffraction grating, there is, for example, Japanese Patent Application Publication No. Sho 62-500052. This method irradiates an optical waveguide with first and second coherent ultraviolet coplanar beams at an appropriate angle of incidence. As an example, two beams are irradiated from a UV source by a beam splitter. And splitting each beam on an optical waveguide using a mirror is disclosed. By superimposing on the optical waveguide, a stripe pattern is formed, and the refractive index of the optical waveguide changes corresponding to the stripe pattern to form an optical waveguide type diffraction grating.

However, in this method, it is difficult to obtain a desired lattice constant because the angle adjustment of each of one beam splitter and two mirrors is very delicate.
Not practical. Further, in order to obtain an optical waveguide type diffraction grating having complicated reflection characteristics as shown in FIG. 4A, the surface shape of the beam splitter or the mirror is processed into a curved surface according to the desired reflection characteristics. It is necessary to precisely control the intervals between the stripes generated by the superposition of the ultraviolet beams on the optical waveguide at irregular intervals. However, it is difficult to actually perform complicated shape processing on a beam splitter or a mirror.

[0006]

The method of manufacturing an optical waveguide type diffraction grating of the present invention has been made in order to solve such a problem, and irradiates a hologram pattern with light to form a light beam from the hologram pattern. By projecting the diffracted light onto the optical waveguide, a refractive index changing portion corresponding to the intensity of the diffracted light is formed on the optical waveguide to form a diffraction grating.

Further, an optical waveguide according to the present invention is characterized by having an optical waveguide type diffraction grating manufactured in this manner.

[0008]

It has been confirmed that the refractive index increases when an optical waveguide, for example, a silica glass optical fiber in which a core is doped with germanium is irradiated with ultraviolet rays. On the other hand, when the hologram pattern is irradiated with light, a diffraction light having a stripe pattern corresponding to the hologram pattern is obtained. Therefore, by projecting the diffracted light from the hologram pattern onto the optical waveguide,
A stripe-shaped refractive index change portion corresponding to the intensity of the diffracted light is formed on the optical waveguide. The optical waveguide is not limited to a silica glass optical fiber having a core doped with germanium. By selecting the wavelength and intensity of the light to be irradiated according to the material of the optical waveguide, the refractive index of the irradiated portion can be changed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing an embodiment of a method of manufacturing an optical waveguide type diffraction grating according to the present invention, an application example of an optical waveguide type diffraction grating will be described.

FIG. 1 is a configuration diagram showing an optical line facility management system using an optical waveguide type diffraction grating as an identification code of an optical line. A terminal box 2 for switching connection of an optical line is provided between the station building 1 and the subscriber's house 3. A plurality of optical lines, one ends of which are connected to the transmission device 4 in the office 1, are bundled as an optical fiber cable 9 as an optical waveguide and extend to the terminal box 2. The other end of each optical line is connected to one end of the optical line extending to each subscriber's home 3 via an optical connector 10 in the terminal box 2, whereby the transmission device 4 in the office building 1 is connected to each end. This means that each of the subscriber homes 3 is connected by one optical line.

In the optical connector 10, the connection can be manually switched arbitrarily. When this switching is performed, first, the identification sign reader (code reader) 5 placed in the station 1 checks the route information of the optical line by an identification method described later, and the route information is checked by the controller 6. To the local controller 11 in the terminal box 2, and the display device 12 notifies the worker at the site of the information. The operator performs desired connector switching based on the route information. After the switching work is completed, the code reader 5 reads the identification mark of the optical path again, confirms the route information on the side of the station 1, and displays this route information on the display device 12 from the control device 6 via the local controller 11. Thus, the operator confirms whether or not the switching has been performed.

FIG. 2 is a block diagram showing the internal configuration of the code reading device 5 and its peripheral devices. The code reading device 5 includes a light emitting unit 20 and a light receiving unit 21. The operation of these units is controlled by a computer 22 and a timing control circuit 23 that constitute the control circuit 6.

The light emitting section 20 includes a light source 24 that emits light having an appropriate spectral width such as white light, an acousto-optic device 25 that controls on / off of light emitted from the light source 24, and an input / output of the acousto-optic device 25. The light emitted from the light source 24 is transmitted through the lens 26, the acousto-optic device 25, and the lens 27.
, And is incident on one end of the optical fiber 40 as inspection light. The optical fiber 40 is connected to the measured optical line 50 via the connecting means 38. The connection means 38 is for selectively connecting the optical fiber 40 to any one of a number of optical paths 50 to be measured.

The light receiving section 21 includes a Fabry-Perot etalon 32, which is an interference spectroscope, and an etalon controller 33 for controlling the distance between two resonance flat plates in the etalon 32.
And a lens system 3 provided in the input / output unit of the etalon 32
0, 31, a light receiving element 34 for converting the light intensity of the output light of the etalon 32 into an electric signal, and a box car integrator 35 for temporally cutting out the output signal of the light receiving element 34 by a signal from the timing control circuit 23. A / D for converting the output signal of the boxcar integrator 35 into a digital signal
And a conversion circuit 36. The etalon 32 inputs the light from the optical fiber 41 connected to the optical fiber 40 by the optical fiber coupler 37, and disperses the light.
At that time, the etalon controller 33 controls the interval between the resonance surfaces in the etalon 32 based on a command from the computer 22 to change the spectral wavelength. Computer 22
Analyzes the reflected light spectrum by taking in data from the A / D conversion circuit 36 while controlling the etalon 32.

Each optical line 50 has a unique identification mark (code) 39 written in the line. The identification mark 39 is a reflection part whose reflectance depends on the wavelength. This reflection part is a stripe in which the refractive index of the optical line 50 is locally changed,
That is, it is constituted by an optical waveguide type diffraction grating, and by appropriately setting the magnitude of the refractive index and the spatial frequency of the change in the refractive index, it is possible to obtain a reflected light spectrum unique to the reflecting portion. This reflected light spectrum becomes the content of the identification mark 39. The identification mark 39 is provided on each of the optical line between the station building 1 and the terminal box 2 and the optical line between the terminal box 2 and the subscriber's house 3 in FIG. When a plurality of terminal boxes are interposed between the office building 1 and the subscriber's house 3, an identification mark is also provided on the optical line between the terminal boxes.

FIG. 3 shows an embodiment of a method of manufacturing an optical fiber type diffraction grating according to the present invention.
FIG. 5 is a view showing a method of forming a reflection portion, which is an optical fiber type diffraction grating used as a device. UV light (ultraviolet light) to optical path 5
By irradiating the light locally to 0, the refractive index of the irradiated part is changed, and a reflecting part having a desired reflected light spectrum is formed.

FIG. 3 shows a recording method using a hologram, in which a hologram 61 is irradiated with UV light 62,
The diffracted light 63 based on the hologram pattern recorded on the hologram 61 is projected on the optical path 50. This diffracted light 63
The refractive index of the optical line 50 is locally changed according to the pattern formed by the light emitting device, and stripes due to the change in the refractive index, that is, the reflecting portion 64 composed of an optical waveguide type diffraction grating is formed on the optical line 50. The pattern created by the diffracted light 63 can be freely set by changing the hologram pattern.

Next, a method of reading the identification mark 39 will be described. FIG. 4A is a characteristic diagram illustrating an example of a reflected light spectrum at the identification marker 39 when the inspection light is applied from the light emitting unit 20 to the optical line 50. In this characteristic diagram, the horizontal axis represents wavelength, and the vertical axis represents light intensity. Reflected light spectrum 91
, Set an appropriate threshold level 92,
A binary code is assigned to each wavelength depending on whether the light intensity at each wavelength from λ1 to λn is larger or smaller than the threshold level 92. FIG. 9B shows a correspondence table, in which the light intensity is set to the threshold level 9.
When the value is larger than 2, "1" is set. When the value is smaller than 2, "0" is set. Thus, the reflected light spectrum is 2
It can be easily coded into a value code. As a method of setting the threshold level 92, in addition to a method of determining an appropriate level in advance, a method of setting the light intensity of a specific wavelength in the reflected light to the threshold level can be considered.

In this application example, the optical line connecting the station building 1 and the subscriber's house 3 is composed of two sectioned optical lines connected by a terminal box 2. Since the identification signs are provided on each of the divided optical lines, it is necessary to distinguish and recognize these. The boxcar integrator 35 is used for that purpose. That is, the timing control circuit 23
As a result, the pulse-like inspection light is incident on the measured optical line,
The reflected light for each identification marker is temporally cut out based on the incident timing of the inspection light. As a result, it is possible to distinguish reflected light from identification marks at different points on the same optical path. The computer 22 can measure the reflected light spectrum for each identification mark by taking in the light intensity data for each wavelength while distinguishing the reflected light for each identification mark. The cut-out of the reflected light can also be achieved by using an optical gate (optical deflector) instead of the boxcar integrator 35.

As shown in FIG. 5, instead of directly writing an optical waveguide type diffraction grating as an identification marker in the optical line, a branch optical line 101 having an identification marker 100 is added using a fiber coupler 102 or the like. You may.

[0021]

As described above, the method of manufacturing an optical waveguide type diffraction grating according to the present invention provides an optical waveguide type diffraction grating by irradiating an optical waveguide such as an optical fiber with diffracted light by a hologram pattern. In each method, an optical waveguide type diffraction grating having a desired lattice constant, in particular, an optical waveguide type diffraction grating having complicated reflection characteristics as shown in FIG. It can be easily manufactured as compared with the method.

The optical waveguide type diffraction grating manufactured as described above can be used as an identification code of an optical line.
That is, if the reflected light wavelength characteristic of the reflecting section is set to be different for each optical line and the spectrum of the reflected light is measured,
The optical path can be easily and accurately identified from the measurement result. Therefore, it is very effective for confirming the connection at the time of the switching operation in the terminal box.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an optical line facility management system using an optical waveguide type diffraction grating as an identification code of an optical line.

FIG. 2 is a block diagram showing the internal configuration of the code reading device and its peripheral devices.

FIG. 3 is a perspective view showing one embodiment of a method for manufacturing an optical waveguide type diffraction grating of the present invention.

FIG. 4 is an explanatory diagram of a method of converting a reflected light spectrum into binary code information.

FIG. 5 is a diagram showing a branch optical path for an identification sign.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuji Hattori 1-chome, Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Katsuya Yamashita 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Fumio Otsuki 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Yutaka Katsuyama 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation Telephone Co., Ltd. (56) References JP-A-2-58284 (JP, A) JP-A-60-241287 (JP, A) JP-A-3-3285 (JP, A) JP-T-62-500052 (JP) , A)

Claims (3)

(57) [Claims] 1. A hologram pattern is irradiated with light, and a diffracted light from the hologram pattern is projected onto an optical fiber, whereby a refractive index changing portion corresponding to a light intensity pattern generated by the diffracted light is formed on the optical fiber. A method for manufacturing an optical fiber type diffraction grating, comprising forming a diffraction grating. 2. The method according to claim 1, wherein the light applied to the hologram pattern is ultraviolet light. 3. An optical fiber that irradiates a hologram pattern with light and projects a diffracted light from the hologram pattern onto an optical fiber, the refractive index changing portion corresponding to a light intensity pattern formed by the diffracted light. An optical fiber characterized by having as a diffraction grating.