JPH05323148A - Connecting fiber device - Google Patents

Abstract

PURPOSE:To provide the connecting fiber device which can be produced with good reproducibility with which specific fibers can be connected at circular sections with a standard size, are integrated to the circular section and are disposed so as to keep the cores of all the fibers free from flaws. CONSTITUTION:The connecting fiber device which uses a wavelength plane coupling or polished coupling is constituted by inserting plural pieces of the optical fiber 11 having the flat flanks tapered to wavelength planes and having the D-shaped sections including cores into a coupling ferrule (clamping ring) 12 so as to mate the respective flat flanks and positioning the cores of the respective optical fibers 11 at the center of the ferrule 12. The optical fibers 11 inserted therein are coupled by forming a nearly circular shape with the whole of the fibers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber device in which optical fibers are connected, such as a wavelength plane coupler or a polishing coupler used for optical communication and optical measurement.

[0002]

2. Description of the Related Art Optical fiber connection methods are roughly classified into permanent connection (splice), which is not removable, and connector connection, which is removable. Permanent connections are used when there is no need to re-separate once connected, and fused and adhesive connections are currently in practice. With either connection method,
Low connection loss, long-term stability of connecting portion, low cost, easy connection work and short working time are required, and these are important keys.

The method of fusing the end faces of the optical fibers to be spliced together is the most frequently used splicing method at present, because it ensures reliable splicing for a long period with low loss, but it is low loss and stable. In order to obtain the property, it is a condition that the cut state of the end face of the optical fiber before fusion is good, that is, the end face has no smoothness, chipping, or protrusion. It is not easy to obtain such a cut surface.

There is also a method in which the optical fibers are brought close to each other, and when they are heated and softened, they are pulled, stretched and welded and fixed, and the fiber is twisted by 90 ° and pulled.
There is a method in which two fibers are brought close to each other, sooted by MCVD, and then core-plus formed. Although these welding methods have few problems with aging and can be made to have good environmental resistance, they still have problems in controllability and reproducibility at the time of manufacture and have not been put to practical use yet.

In the structure of the connecting fiber device in which the wavelength planes are combined with each other or the polishing surfaces are combined with each other when the optical fibers are combined with each other, the fiber cladding portion and the core portion must be accurately arranged. It was difficult to construct.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention allows special fibers to be joined in a circular cross section with standard dimensions, such that the special fibers are integrated into the circular cross section so that the core of the entire fiber is intact. It is an object to provide a coupled fiber device that is arranged.

[0007]

SUMMARY OF THE INVENTION In order to solve the above technical problems, the present invention provides a connecting fiber device using a wavelength plane coupling or a polishing coupling.
A plurality of wavelength planes having tapered side surfaces,
An optical fiber having a D-shaped cross section including a core is inserted into a coupling ferrule (fitting ring) so that respective flat sides thereof are aligned with each other, and the core of each optical fiber is positioned at the center of the ferrule. In addition, all the inserted optical fibers are connected in a substantially annular shape.

Generally speaking, optical fiber devices form a "black box" having N input optical fibers and M output optical fibers, all optical fibers being equal. The optical fibers are equivalent because they must be coupled or spliced with compatible system fibers if they are not the same.

The concatenated fiber device of the present invention is "fiber based", that is, the black boxes described above consist of the fibers themselves, which have in some way been locally modified and treated. It is a thing. For example, a fused taper coupler could be 2N ports with N input ports and N output ports, locally fused to each other and tapered into N equivalent non-transformed. It consists of fibers.

Of particular interest in the concatenated fiber device of the present invention are (a) four-port wavelength plane fusion taper couplers, (b) four-port polished couplers, and (h) ) A mode shape converter. In case (a), one of the two identical single-mode fibers is locally transformed by polishing either one, fixing and tapering or etching the two fibers before tapering them together. Be combined.
In case (b), two identical single-mode or multimode fibers are both ground to a substantially semi-circular cross section and then bonded to each other by fusing or laminating. In the case of (c), the fiber is ground on the opposite side to form a square shape, and when flattened into a taper, between the circular core and the square mode shape, which are flattened taper,
It is a prism that acts as a mode adapter.

When circular fibers are planar ground to form the concatenated fiber arrangement of the present invention, the circular, dimensional integration of the remainder of the fiber is the planar ground fibers of the fiber arrangement. For some reason, they interfere with each other. In the reproducible manufacture of interconnected fiber devices, it is important that the amount of polished fiber can be manufactured one after the other within tight tolerances.
Such a need is difficult to secure and can be quite lengthy to assemble. Industrializing such an assembly relies on locally deforming a standard circular fiber as described.

As another method of constructing and assembling fiber-based devices, one or more fibers need to be deformed from their standard circular shape, which is not industrial use. That is, in order to make a specially deformed fiber at the fiber manufacturing stage, its tolerance is very easy to control. Deformed fibers with the same cross-section over the length should be able to be delivered on the order of kilometers. Special fibers have traditionally been used as an experimental tool to study the manufacture and properties of 4-port wavelength flat couplers and polished fiber couplers, but as mentioned above, they are used industrially. I didn't.

The reason for this lack of utilization is the need for interchangeability of the optical connections, either by splicing or by splicing between the fibers of the device and the system fibers, which are generally circular. .. That is, the interlocking fiber device of the present invention is a novel device for manufacturing a fiber-based device from a special fiber,
It is compatible with optical connections between device fibers and standard fibers and ensures reproducibility between devices.

A modification of the connecting fiber device according to the invention is as follows. When making interlocking fiber devices such as wavelength flat couplers and polishing couplers, the fiber cladding portion can be integrated without circular or dimensional integration of the remaining fibers.
It modifies the fiber so that it can be removed.
In that case, the rest of the fiber will contact more than half the circumference of the circle. According to the invention, optical fibers take advantage of the fact that special fibers can be combined as standard round fibers in exactly the same connecting fiber arrangement. This is a circular collection of fibers that provides the optical arrangement of the connecting fiber device, and need not be perfectly circular. The splice loss when splicing between a special fiber and a standard fiber is the same as between two standard fibers.

A standard optical fiber consists of a glass cylinder surrounded by a polymer jacket and other cable protection tubes. Another feature is a cylinder consisting of a core region with a higher index of refraction than the surrounding cladding region. The core diameter is approximately 10 when the fiber is single mode.
μm. And if the fiber is multimode,
It is about 50 to 100 μm. Standard communication fibers are those that have a cladding diameter of 125 μm, whether the fiber is single mode or multimode.

As described above, when assembling fibers in accordance with the inventive connecting fiber device, a modification of the fibers is required, which is the cladding portion, and the core always changes its size and shape. There is nothing. In one of the interlocking fiber devices of the present invention,
Two cylindrical ferrules (fitting rings) are precisely arranged in the longitudinal direction, and the ends of the fibers to be connected are inserted therein. Thereby, the fiber is held through the ferrule in a very precisely bare circular hole. The optical connection characteristics depend on the placement of the cores of the fibers in the connecting fiber arrangement and, conversely, on the fiber diameter and the tolerance of each of the ferrule holes.

In either case, the characteristics of the core placement do not depend on having a perfect circular fiber in the exact hole of the ferrule, but with a perfect circular periphery so that the fiber core is held centered. Depends on what you do. For a particular fiber, the perimeter of the fiber should be perfectly round, rather than the clean semi-circle being the allowed core placement.

In the case of coupling directional couplers, ie optical fibers, the electric field associated with energy propagation in one waveguide is arranged to overlap the energy propagating in the adjacent coupled waveguides. ,
Energy exchange takes place between the two waveguides. In optical waveguides, one of the optical cladding functions is perpendicular to the distance between what can interfere with it and the optical field (optical field), thus providing additional source loss. When manufacturing optical fiber directional couplers or Y-couplers, that is, when optical fibers are interconnected, this effect of cladding distance is partially suppressed over a length to provide a coupling area. Need that. Partial suppression of cladding is achieved by physically removing the cladding by polishing or etching, or tapering the fibers. That is, a joining method in which polished optical fibers are melted, joined together, buried under a thick protective cladding, and joined together. Thereby, by coupling the optical fibers and burying them under a thick protective cladding, the optical properties of such couplers are monitored and fusion is continued until the desired properties are obtained.

In accordance with the present invention, a method of making a splice having stable, low loss single mode fiber is described.
The two polished bare fiber cores can be brought together by a fusing method with the same convenience as tapering. D fiber (Dyott, RB and Belido,
J.'s “Polarisation-holding directional coupler mad”
e from elliptically cored fiber having a D-sectio
n ”, Electron. Lett. 1983, 19, pp. 601-602) and double core fiber (Scriffner, G., Schneider, H. and Schunfre, G.“ Double-core single-mode optical f
ibre as directional coupler ”Appl. Phys., 1980,2
Note that non-standard fiber-based damping couplers, such as 3, pp. 41-45;) are also not manufactured from standard fibers, like the present invention.

In the taper method, in which the ends of the fibers to be connected are made into tapers, the pulling process is conventionally used to reduce the fiber diameter. This reduction in diameter results in a smaller core and a wider optical field. Such a tapering process is allowed to continue until most of the energy can be taken up by the cladding interface. Unfortunately, the taper section of multimode fiber has low loss, but is inherently prone to loss due to the long connecting connections. Also, the taper in single mode fiber is
It is limited to fibers called "matched-cladding." Therefore, special single-mode fibers such as the important dispersion-averaging fibers and high birefringence fibers are due to low loss taper couplers. Cannot be used for.

The fiber connecting method by the fiber taper method is carried out by inserting two or more fibers to be combined into a frame and stretching it. Therefore, this method is an alternative method of polishing / etching and has been performed in the laboratory, and is therefore mainly used in the laboratory. The invention has the advantage that it can be used newly in the manufacture of polished fiber devices, is similar to the simplified version of the tapering process and is applicable to all fiber types.

Next, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1a shows the result of FIG. 2a according to the method of the present invention.
4 is a photograph of a cross section of a D-type fiber in a coupled ferrule (fit ring) made from the fiber having the cross section shown in FIG. This fiber is suitable for making wavelength plane couplers. FIG. 1b shows the result of FIG. 2b according to the method of the present invention.
3 is a photograph of a cross section of a special D-type fiber in a bonded ferrule made from the fiber of the cross section shown in FIG. This type of fiber is suitable for abrasive couplers.

In both of these, the coupling loss is less dangerous than the coupling loss between two annular fibers. In both of the above examples, the fibers to be joined, i.e. the special fibers and the annular fibers, are in every respect the same, but not in the non-annularity of the cladding.

FIG. 2 shows the cross sections of the respective optical fibers, and the cross section of the circular optical fiber has multiple faces so that a part of a polygon can be formed. The flat surfaces of the D-shaped optical fibers are connected to the respective polygonal surfaces. The connecting fiber device of the present invention connects special fibers with standard dimensions and circular cross section. The special fibers are integrated in a circular cross section and are arranged such that the core of the whole fiber is intact. This inserts a special fiber into the standard mating ferrule and the core of the fiber is precisely located at the center of the ferrule as the core of a full circle fiber. Although a typical fiber having a D-shaped cross section is shown in FIGS. 2A and 2B, the cross section shown in FIGS. 2C and 2D can also be used.
The cross section of FIG. 2d is suitable for a rectangular mode converter. Above, the permissible fiber shapes that are generally used in the connecting fiber device of the present invention have been shown.

FIG. 3 is a perspective view showing an example of an optical fiber connecting fiber device of the present invention. That is, it is possible to create a fusion taper coupler having 2 × 2 ports having two input ports and two output ports.
Locally, it consists of two equivalent non-transformed fibers that are fused together and tapered together. That is, two pieces of the taperized fibers 11 are inserted into the coupling ferrules (fitting rings) 12, and the coupling fiber processing is performed by the plane coupling. And ferrule 11
As shown in the drawing, each of the fibers 11 inserted in the core is placed with its core located at the center of the ferrule,
All the inserted optical fibers are connected in a substantially annular shape.

[0028]

As described above, the following remarkable technical effects were obtained by the fiber deformation for connection of the present invention. First, a structure of the interlocking fiber device was provided that could be reproducibly manufactured. Secondly, special fibers can be joined in a circular cross section with standard dimensions, the special fibers are integrated into a circular cross section, the core of the whole fiber is placed intact and inserted into a standard mating ferrule. And the fiber core is at the center of the ferrule,
An interconnected fiber device is provided that is accurately positioned as the core of an all-round fiber. Third, a D-shaped cross section of fiber has been shown to be a typical permissible fiber configuration in a coupled fiber arrangement suitable for rectangular mode converters.

[Brief description of drawings]

FIG. 1 is a photograph showing a crystal structure of a part of a cross section of a connecting fiber device for an optical fiber according to the present invention.

FIG. 2 shows a cross section of each of the optical fibers used in the optical fiber connecting fiber device of the present invention.

FIG. 3 is a perspective view showing an example of an optical fiber connecting fiber device of the present invention.

Front Page Continuation (72) Inventor Michael Odonchach Ireland, Limerick, Prassey Technological Park, Limerick University, Lightwave Technology Research Center (72) Inventor Taimon Burk Ireland, Limerick, Prassey Technological Park , University of Limerick, in the Lightwave Technology Research Center (72) Inventor Karam Crayan Ireland, Limerick, Prassey Technical Park, University of Limerick, in the Lightwave Technology Research Center (72) Inventor Conles Hesse Ireland, Limerick, Prassey Technical Park, Limerick University, Lightwave Technology Research Center

Claims (1)

[Claims] 1. A coupling fiber device using a wavelength plane coupling or a polishing coupling, comprising a plurality of wavelength plane tapered side surfaces.
An optical fiber having a D-shaped cross section including a core is inserted into a coupling ferrule (fitting ring) so that respective flat sides thereof are aligned with each other, and the core of each optical fiber is positioned at the center of the ferrule. 2. The coupled fiber device, wherein all the inserted optical fibers are coupled in a substantially annular shape.