JP2004198766A - Fiber grating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a fiber grating which can be mass-produced and whose installation place is not restricted. <P>SOLUTION: A plane plate 17 formed by laminating a plurality of layers with different refractive indexes in a process of manufacturing a polymer waveguide is inserted and fixed between opposite end surfaces of optical fibers 1 to obtain the same structure having refractive index variation along the axes of the optical fibers 1 with a conventional fiber grating. When the plane plate 17 is manufactured, values of refractive indexes of respective layers of the plane plate and thickness of the layers are optionally set to obtain desired characteristics, and consequently the manufacturing efficiency of the fiber grating is much higher than that of a conventional manufacturing method of a series of flow processes. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fiber-type optical component used in fields such as optical communication and optical sensing.
[0002]
[Prior art]
2. Description of the Related Art In recent years, fiber gratings have attracted attention as a new type of fiber-type optical component in fields such as optical communication and optical sensing. Fiber gratings have the features of fiber-type optical components, such as good connectivity with transmission fibers (low insertion loss) and miniaturization of components, and also provide various functions not found in conventional optical components. There are many that have been vigorously developed and put into practical use.
[0003]
The functions of fiber gratings are mainly (1) wavelength filters that selectively reflect only specific wavelengths from broadband wavelengths, and (2) wavelengths that accumulate on transmission lines in long-distance / high-speed optical communication. To compensate for the effects of dispersion, chromatic dispersion compensation using the characteristic that the delay time varies depending on the reflected wavelength, and (3) temperature sensors and strain sensors that use the fact that the reflection center wavelength has temperature dependence and tension dependence Is mentioned.
[0004]
Hereinafter, a conventional fiber grating will be described with reference to the drawings.
[0005]
In a conventional fiber grating, as shown in FIG. 1, a refractive index changing portion 3 is formed on a core of an optical fiber 1 at a predetermined grating pitch (period) 2 along the axial direction of the fiber (see FIG. 1). For example, Non-Patent Document 1). The fiber grating has a function of selectively acting on light having a specific wavelength corresponding to the period of the change in the refractive index of light guided through the optical fiber, and coupling the light to another mode.
[0006]
Explaining with reference to the example of FIG. 1, the fiber grating selectively reflects only light 5 of a specific wavelength from the incidence of light 4 of a wide band wavelength, and light 6 of other wavelengths. It can be transmitted. A fiber grating having this function is expected as a key component of a WDM (Wavelength division multiplexing) system that will attract attention in optical communication in the future.
[0007]
In general, a method of fabricating a fiber grating is to remove a coating of an optical fiber, irradiate a UV (ultraviolet) laser having a periodic intensity distribution from the side of the optical fiber, and periodically change a refractive index. (For example, Non-Patent Document 1). This method can also be divided into two types: a short period type having a period of 1 μm or less, and a long period type having a period of 100 to 500 μm.
[0008]
In the short-period fiber grating, since the period of the refractive index change is as short as 1 μm or less, a periodic intensity distribution is realized by interference fringes due to light interference, and a fiber grating is formed.
[0009]
FIG. 2 shows a typical method for producing a fiber grating.
[0010]
FIG. 2A shows a two-beam interference method produced by interference of two light beams. When an ultraviolet light 7 of a certain wavelength is irradiated on the optical fiber 1 from two directions through a beam splitter 8 and a mirror 9, the light interference 10 This is based on the principle that a periodic refractive index changing portion 3 is generated in the longitudinal direction (axial direction) of the core.
[0011]
FIG. 2B shows a phase mask method. By irradiating the phase grating 11 with ultraviolet light 7, the same thing as the phase grating 11 can be written in the optical fiber 1. Here, 12 and 13 are diffracted lights after irradiation of the optical fiber. Previously, the two-beam interference method was mainly used, but the phase mask method is now the mainstream from the viewpoints of stability and reproducibility during fabrication.
[0012]
On the other hand, in a long-period fiber grating, the period of change in the refractive index is as long as several hundred μm, so that it can be manufactured without using interference. As a manufacturing method, a step exposure method or the like in which a grating as shown in FIG. 2C is written step by step using a moving stage 14 with a mirror 9 and a focusing lens 15 is used.
[0013]
Fiber gratings are currently manufactured by the above-described method, and are used in many fields such as optical communication and optical sensing.
[0014]
[Non-patent document 1]
Ryozo Yamauchi, "Latest Technology Trend of Fiber Grating", IEICE Technical Report, May 1999, OFT99-8, 43-48
[0015]
[Problems to be solved by the invention]
However, the conventional fiber grating has the following disadvantages. That is, the process of removing the coating of the optical fiber, irradiating the light, changing the refractive index of the optical fiber, and then fixing the fiber to, for example, a glass substrate for the purpose of reinforcing the part in the fabrication. is necessary. For this reason, there is a problem that the production efficiency is poor and it is not suitable for mass production. Further, in the structure in which the fiber is fixed to the substrate, there is a problem that the installation place is limited because the fiber grating portion becomes relatively large.
[0016]
SUMMARY OF THE INVENTION An object of the present invention is to provide a fiber grating having a new structure that eliminates the above-mentioned conventional disadvantages and enables mass production.
[0017]
Another object of the present invention is to provide a fiber grating which eliminates the above-mentioned drawbacks of the related art and is not limited in installation location.
[0018]
[Means for Solving the Problems]
To achieve the above object, according to claim 1 of the present invention, there is provided a fiber grating having a plurality of layers having different refractive indices along an axial direction of an optical fiber, wherein the opposing optical fiber has a plurality of layers having different refractive indices. A flat plate having layers laminated thereon, the flat plate is inserted between the end faces of the optical fiber, and each optical fiber and the flat plate are fixed mechanically or with an adhesive or the like, along the axial direction of the optical fiber. It is characterized in that an arbitrary change in the refractive index is given.
[0019]
According to a second aspect of the present invention, in the fiber grating according to the first aspect, a flat plate manufactured by a process of manufacturing a polymer waveguide is used.
[0020]
According to a third aspect of the present invention, in the fiber grating according to the first aspect, a flat plate is inserted and fixed between optical connector plugs respectively attached to ends of the optical fibers facing each other.
[0021]
Hereinafter, the operation and principle of the present invention will be described in detail.
[0022]
According to the first aspect of the present invention, a structure in which a flat plate having a change in refractive index is inserted and fixed between end faces of optical fibers facing each other is adopted. As compared with the manufacturing method of the flow step, manufacturing can be performed simply by inserting and fixing a flat plate between the end faces of the optical fiber, so that manufacturing efficiency is greatly increased. Further, a grating function can be added simply by inserting a flat plate at an arbitrary position in the longitudinal direction of the optical fiber. Also, if the flat plate is removed, the function of the grating can be removed and the function of the general fiber transmission can be restored. The operation of adding or removing the function of the grating arbitrarily in the optical fiber network can be performed. Becomes possible.
[0023]
According to the second aspect, by manufacturing a flat plate in which a plurality of layers having different refractive indices are stacked by using a manufacturing process of a polymer waveguide, mass production of the flat plate becomes possible, and the efficiency of the fiber grating is improved. Production becomes possible.
[0024]
According to the third aspect, if the optical fiber is mounted on the optical connector plug, the connector connection mechanism can be used almost as it is, and the function of the fiber grating can be provided. It is possible to additionally provide a grating function in the fiber.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
[0026]
FIG. 3 shows a first embodiment of the fiber grating of the present invention. In the figure, reference numeral 1 denotes an optical fiber, 16 denotes a core of the optical fiber 1, 17 denotes a flat plate, and 18, 19 denote a plurality of refractions in the flat plate 17. The layers with different rates are shown. A flat plate 17 in which a plurality of layers having different refractive indexes are laminated in advance is prepared, and the flat plate 17 is inserted between the end faces of the two optical fibers 1 and fixed mechanically or with an adhesive. Thus, the optical fiber has a refractive index change in the longitudinal direction (axial direction) of the optical fiber as shown in FIG. 4, and has the same refractive index change as the conventional fiber grating shown in FIG. When the flat plate 17 is manufactured, desired characteristics can be obtained by arbitrarily setting the value of the refractive index and the thickness of each layer of the flat plate 17.
[0027]
FIG. 5 shows a process for producing a polymer optical waveguide suitable for producing the above-mentioned flat plate.
[0028]
A polymer material 21 having a certain refractive index is applied and laminated on a silicon substrate 20 for a certain period of time to form a refractive index layer 22 (a lower cladding layer) having a certain refractive index and a thickness (FIG. 1A). (b)). Next, a polymer material 23 having a different refractive index from the above is applied and laminated in the same manner, and a layer 24 having a certain refractive index and a certain thickness is overlaid (FIG. 3 (c)). Thereafter, unnecessary portions are removed by using reactive ion etching 25 to form a ridge-shaped core portion 26 (FIG. 4D). Thereafter, the polymer material 21 is applied and laminated again, and the core portion 26 is covered with the refractive index layer 27 (upper cladding layer) to form an optical waveguide having a buried structure (FIG. 3E). By cutting out to a predetermined size (FIG. 1F), a polymer optical waveguide is produced.
[0029]
FIG. 6 illustrates a process of manufacturing a flat plate in the fiber grating of the present invention by the process of manufacturing the polymer optical waveguide.
[0030]
In the manufacturing process, a polymer material 21 having a certain refractive index is applied and laminated on a substrate 20 such as a silicon wafer for a certain period of time to form a layer 22 having an arbitrary refractive index and thickness (FIG. )). Next, a polymer material 23 having a different refractive index from the above is applied and laminated in the same manner, and a layer 24 having a certain refractive index and a certain thickness is overlaid (FIG. 2B). By repeating the above steps, a plurality of layers having different refractive indices can be arbitrarily multi-layered. After the layers are deposited, the layers are cut out to a predetermined size by a dicing saw 28 (FIG. 3C), and the laminated portions are separated from the silicon substrate 20 using hydrochloric acid, so that a plurality of layers having different refractive indices are provided. It is possible to produce a flat plate.
[0031]
FIG. 7 shows an example of an optical fiber connector suitable for the fiber grating of the present invention, here a well-known MT connector.
[0032]
FIG. 3A is an exploded perspective view. The MT connector includes two MT connector plugs 29, two guide pins 30, and a clamp spring 31. Used for connection.
[0033]
FIG. 4B is an enlarged view of the end face of the MT connector plug 29. The MT connector plug 29 has two guide pin holes 32 and a plurality of optical fiber holes 33, and a plurality of optical fibers included in an optical fiber tape 34. 1 is bonded and fixed to the MT connector plug 29 while being inserted into the optical fiber hole 33.
[0034]
The connection between the MT connector plugs 29 is performed by inserting two guide pins 30 into the guide pin holes 32 of each plug 29, butting them together, and fastening them with the clamp spring 31. By this fastening, the end faces of the plurality of optical fibers in the opposing plug 29 are axially aligned, and the multi-core optical fiber tapes 34 are connected together.
[0035]
FIG. 8 shows a fiber grating according to a second embodiment of the present invention, in which the above-described MT connector is attached to an end of an optical fiber facing each other.
[0036]
Here, a flat plate, for example, a flat plate 17 manufactured by the process shown in FIG. 6 is provided with a hole for inserting a guide pin, and a guide pin 30 is passed through the flat plate 17 with the guide pin. , And then mechanically fixed with a clamp spring 31 similarly to the MT connector (however, a clamp spring 31 having a length considering the thickness of the flat plate 17 is used).
[0037]
In the connection mode using the MT connector, the fiber gratings can be collectively realized by the number of optical fibers in the optical fiber tape.
[0038]
【The invention's effect】
As described above, according to the fiber grating according to the first aspect, the fiber grating includes opposing optical fibers and a flat plate in which a plurality of layers having different refractive indexes are stacked, and the flat plate is inserted between end faces of the optical fibers. Since each optical fiber and the flat plate are mechanically or fixed with an adhesive or the like to provide a structure in which an arbitrary refractive index change is provided along the axial direction of the optical fiber, a conventional one or several pieces are used. Compared with the production method of a series of flow steps, the production can be performed only by inserting and fixing the flat plate between the end faces of the optical fiber, and the production efficiency is greatly increased. Furthermore, at any position in the longitudinal direction of the optical fiber, the function of the grating can be added simply by inserting a flat plate, and if the flat plate is removed, the function of the grating is removed, and the function of general fiber transmission is performed. It is also possible to return to the normal state, and operations such as adding or removing a grating function arbitrarily in the optical fiber network become possible.
[0039]
According to the fiber grating of the second aspect, the use of the flat plate manufactured by the manufacturing process of the polymer waveguide makes it possible to mass-produce the flat plate and, consequently, the mass production of the fiber grating.
[0040]
According to the fiber grating of the third aspect, a structure is employed in which a flat plate is inserted and fixed between the optical connector plugs attached to the ends of the optical fibers facing each other, so that the optical fiber is mounted on the optical connector plug. If this is the case, it is possible to make use of the connector connection mechanism as it is, and to provide the function of a fiber grating, so that it is possible to add the function of a grating to the already installed optical fiber. Become.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a function of a fiber grating. FIG. 2 is an explanatory view showing a conventional method of manufacturing a fiber grating. FIG. 3 is a structural view showing a first embodiment of a fiber grating of the present invention. FIG. 5 is an explanatory view showing a change in the refractive index in the axial direction of the optical fiber according to the first embodiment. FIG. 5 is a process chart showing a process for producing a polymer optical waveguide. FIG. FIG. 7 is a structural view showing an example of an optical fiber connector. FIG. 8 is a structural view showing a second embodiment of the fiber grating of the present invention.
1: optical fiber, 2: grating period, 3: refractive index change portion, 4: incident light of a wide range of wavelengths, 5: light selectively reflected by the grating, 6: light after passing through the grating, 7: ultraviolet light, 8 : Beam splitter, 9: mirror, 10: interference light, 11: phase grating, 12, 13: diffracted light, 14: moving stage, 15: lens, 16: optical fiber core, 17: flat plate, 18, 19: refraction Index layer, 20: silicon substrate, 21, 23: polymer material, 22, 24, 27: refractive index layer, 25: reactive ion etching, 26: waveguide core, 28: dicing saw, 29: MT connector plug, 30: guide pin, 31: clamp spring, 32: guide pin hole, 33: optical fiber hole, 34: multi-core optical fiber tape.

Claims (3)

A fiber grating having a plurality of layers with different refractive indices along an axial direction of an optical fiber,
It consists of opposing optical fibers and a flat plate in which a plurality of layers having different refractive indices are laminated. The flat plate is inserted between the end faces of the optical fibers, and the optical fibers and the flat plate are fixed mechanically or with an adhesive or the like. A fiber grating having an arbitrary refractive index change provided along the axial direction of the optical fiber. The fiber grating according to claim 1,
A fiber grating using a flat plate manufactured by a manufacturing process of a polymer waveguide. The fiber grating according to claim 1,
A fiber grating, wherein a flat plate is inserted and fixed between optical connector plugs attached to ends of optical fibers facing each other.

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