JPH06308354A - Package structural body of optical fiber - Google Patents

Abstract

PURPOSE:To provide the package structural body of an optical fiber which is capable of keeping the elongation and contraction of a silica coupler/base body apart from the elongation and contraction of an adhesive and is more surely enhanced in long-term stability and reliability. CONSTITUTION:Te fiber 3 is arranged so as to come into contact in parallel with the silica base body 7 on both cases of fusing of the fiber 3 in a transverse direction and fusing of the fiber 3 in the silica base body 7. The stress and strain in the fiber 3 are relieved and removed by heating and annealing before fusing. The fiber is directly fused and fixed near both ends of the silica base body, by which the package structural body having the extremely stabilized coupling property is obtd.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an optical fiber packaging structure comprising at least a single fiber splice. In particular, it relates to a packaging structure for an optical fiber of at least a primary packaging structure and its assembly, in which the fiber device is actually fusion-bonded to a silica substrate, so that it has a bond with ultimate stabilization.

[0002]

2. Description of the Related Art Optical fiber coupling methods are roughly classified into permanent couplings (splices) that are not removable and connector couplings that are removable. Permanent coupling is used when it is not necessary to separate it once it has been coupled, and fusion and adhesive couplings are currently in practice. In any of the coupling methods, low coupling loss, long-term stability of the coupling portion, low cost, simplicity of coupling work, and short working time are required, and they are important keys.

Also, the reliability of a single mode fused taper coupler depends on the method of packaging the fiber device. The tapered coupling region must be in air (or in a low refractive index encapsulant such as silicone rubber), but must not expand or contract due to, for example, thermal stress, or otherwise. , The coupling ratio fluctuates. Packaging of fused taper couplers is usually a two step process. The primary package is a silica substrate (tube or rod), to which the fiber leads are adhesively secured, so that the thermal expansion of the substrate is due to the silica fiber coupler. It matches. Besides retaining the coupler, a good primary package stabilizes the coupling area and is immune to temperature and vibration effects.
However, the long term reliability of the coupler, temperature stability and chemical resistance depend on the properties of the adhesive holding the fiber lead to the silica substrate in the primary package. The secondary package imparts ruggedness to the fiber device, typically made of stainless steel tubing or injection cast plastic, etc., and is further applied to an adhesive-bonded primary silica substrate.

Further, the fusion method in which the end faces of the optical fibers to be coupled are fused by arc discharge heat, and the coupling can be ensured with low loss and long-term reliability. As a way
Most commonly used, this is done for the cutting state of the optical fiber end face before fusion, that is, it requires smoothness, chipping, protrusions, etc. of the end face and stable low loss. To get it.

Also, fiber devices which generally require stabilization and protection after assembly have a stabilizing structure that varies with respect to the sensitivity of the device itself. The most stable arrangement is one in which the fibers are attached to a substrate of the same material. For example, for SiO ₂ glass fibers, a silica glass substrate is used to match the coefficient of thermal expansion. However, recently, fibers have been bonded to silica substrates with epoxy adhesives. Epoxy bonds can be bonded over specific temperature ranges and under other environmental conditions.
It can be stable. However, to date, fibers have been fixed to silica substrates with adhesives such as epoxy adhesives. Epoxy adhesives can be stable to some temperature range or other environmental conditions, but always have a limited range of conditions and integration with epoxy resin is relatively difficult for optical fibers and substrates. .

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention overcomes the above-mentioned drawbacks of conventional fiber device packaging structures and is competitive in performance with conventional adhesive-based commercial couplers. It aims at providing the fiber coupler which has. It is another object of the present invention to provide an optical fiber packaging structure capable of keeping the silica coupler / substrate elongation and contraction away from the adhesive elongation and contraction. It is another object of the present invention to provide an optical fiber package structure that has long-term stability and reliability enhanced more reliably than the adhesive package.

[0007]

SUMMARY OF THE INVENTION In order to solve the above technical problem, the present invention provides a package structure for an optical fiber device comprising a splice of at least a single fiber, the fiber being laterally fused. The fiber is placed in parallel contact with the silica substrate, both when fused and when the fiber is fused in a silica substrate, and the stress in the fiber prior to fusing , The strain is released and removed by heating annealing, the fiber is directly fused and fixed near both ends of the silica substrate, and the silica substrate is in the same order as the size of the fiber. If there is
The fiber and the silica substrate can be subjected to the heating anneal treatment and the fusion treatment at the same time. Further, when the silica substrate is too large, the silica substrate acts as a heating sink, which makes it difficult to remove stress, resulting in long heating furnace The fiber and the silica substrate arranged therein are put therein and subjected to stress relief treatment by heating anneal treatment, the silica substrate is directly fused and fixed to the fiber, and the silica component is bonded to the silica substrate by a silica component. The package structure is characterized in that it is actually fusion-bonded and thereby has ultimate stability binding properties.

[0008]

In the package structure of the present invention, "optical fiber or optical fiber device" means a single fiber, a taper in a single fiber, a polished and etched fiber, or a multi-fiber in a splice. It is comprised of a fiber structure, such as fused to each other and the fibers fused to each other into a taper. It also includes those made up of different combinations. Conventionally, a melt-tapered coupler consists of two input fibers and two output fibers, in the necked cutting region of which two bare fibers are fused together, stretched and glued together. By packaging the fiber between the fiber and the substrate, the coupler is stabilized by a primary reinforcing means, ie the bare fiber and its coupling area are not contaminated on the surface of the taperized fiber. As configured.

In the method of the present invention, the primary packaging method is to deposit the fiber leads onto the silica substrate. This can be accomplished without adhesive and without significantly increasing excess loss or variability in the coupling ratio of the fiber device. Therefore,
The primary package is made entirely of silica, ensuring long-term stability and reliability of the coupler.
The package is as durable as all-silica fiber. Secondary packages can be applied as well.

In general, the present invention has been described with a 4-port fused, tapered taper as the most precise example of a fiber device and as the most sophisticated example of a fiber device packaging structure. Also, the method of fused fiber substrate is described. The melt-tapered coupler consists of two input fibers and two output fibers, as shown in Figure 1a. In the narrowed colling region 4 shown, two bare fibers are fused and stretched together. It is necessary to stabilize this coupler with primary reinforcement means,
That is, the bare fiber and the coupling area are such that the surface of the tapped fiber is not contaminated,
Composed. Typically, this is accomplished as shown in Figure 1b, i.e. the coupler applies a fusion treatment to the bare and coated fiber sections to form a silica based tube or rod. On the one hand, while avoiding on the taper part. That is, generally, the taper portion is left in contact with neither the silica nor the substrate. The stability of this packaging structure can be enhanced by adding a low index material (ie, one with a lower index than silica) to the taper portion. It is also possible to hold the coupler in a stable manner in the primary reinforcing means and take a secondary package structure as shown in FIG.

The primary reinforcement of other fiber devices is very simple to assemble. For example, FIG. 2a schematically shows a fiber held in a groove in a silica block. There, the fibers and blocks are polished as shown. Such a block with polished fibers forms the basis of the polished coupling portion and also forms many tapering fiber devices. FIG. 2B schematically shows a fiber butting coupling package body. Two fibers were placed and glued onto a silica glass plate. FIG. 2c shows an example of a reinforcing structure for a fiber fusion coupling. The steel rod, opposite the silica rod, is used as a reinforcing structure, along with a heated shrink tube.

The optical fiber packaging method of the present invention takes advantage of the fact that under certain conditions, the fiber can undergo considerable lateral deformation without causing transmission loss.
Therefore, it is appropriate to fuse the silica fiber with the silica substrate in the package of the fiber device without causing transmission loss. This fusion eliminates material mismatches when the adhesive is introduced between the fiber and substrate in standard packaging. The main condition that must be met, both when fusing the fiber laterally and when fusing the fiber to the silica substrate, is to release the stress and strain therein before the fusing step. , It must be removed.

If the fiber must be fused to another fiber or substrate (eg, the silica structure is usually larger than the fiber), the fiber is firmly anchored on both sides of the fused region. I have to let you. Such a fixation does indeed stress the fiber in the region between the two fixtures. This stress is relieved over the fiber length between the two fixtures (typically about 1 cm) prior to fusion, which is generally a local method (which is done on the order of about 1 mm). This is very important. This stress relief is achieved by placing the fiber in a long heating source, about 1 c
A long heating source with an m-long flame (eg oxygen-butane) was used. When the fusion heat source is not localized as described above, it is possible to perform both the role of stress relief and the role of fusion at one time without causing a transmittance loss.

When fusing a fiber to another fiber or silica substrate, it must be in intimate contact at the fusing point. If the silica substrate is of the same order of magnitude as the fiber, the fiber and silica substrate can be placed in parallel contact prior to the stress relief treatment. However, if the substrate is too large, it will act as a heating sink and stress relief will not take place in the fiber. Therefore, for large silica substrates, it is necessary to relieve the stress in the fiber and then bring the silica substrate into intimate contact with the fiber and not interfere with the fixing conditions of the fiber. It is not always possible to have a silica substrate in intimate contact with the fiber when manufacturing a fiber device. Therefore, in this case, it is necessary to introduce the fiber into the substrate tube after manufacturing the fiber device, whether large or small, without disturbing the fixing conditions of the fiber.

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

[0016]

Example 1 Welding of coupler on silica tube substrate : A silica capillary tube (tube substrate) having an outer diameter of 2 mm and a wall thickness of 260 μm was used as a substrate. After the coupler was manufactured, the capillary was passed through the coupler, which was laid at its weight in the coupler substrate, spanning a minimum of 4 mm of untapered fiber leads on each side of the coupling area. The weight of the capillaries allowed them to come into intimate contact with the non-tapered fiber leads, but by holding the coupler taut the taper region was maintained in the required air.

The fiber leads were welded to the inner wall of the capillary using an electric arc. Electrodes were placed across the fiber / capillary and arced extending less than 4 mm along the fiber. The arc is applied a distance of 2 mm from the end of the capillary and protects the bare fiber from maximum heat. The arc was gradually reduced on the capillary tube so that only the portion in contact with the coupler reed was heated. This matched the specific heat capacity of the fiber and substrate. And, by this, good fusion was secured.

Even under a microscope, it was difficult to observe fusion during and after the application of the arc. Although it was possible to continue fusion bonding with little increase in transmittance loss, it was found necessary to rely on measurement of transmittance loss, and continuous fusion can be conveniently presented.
A loss increase of 0.01 dB was used as an indication of satisfactory fusion. After removing the arc, it was found that the coupling ratio did not change from the initial value.

A detailed description will be given below with reference to the drawings. Figure 1
1 is a schematic diagram showing a fiber device to be coupled to the present invention. That is, an example of producing a non-tapered fiber will be described. FIG. 1a shows the structure of the fibers to be bonded according to the invention. That is, the optical fiber 1 has a diameter of 125 .mu.m and comprises a central coupling region 4, a bare fiber portion 5 on both sides thereof, and a further coated fiber portion 3. Then, the fiber 1 is held between two arranged fiber holders, and for example, the fiber device 3 or 1 having a diameter of 300 μm is placed as a fiber in a straight groove so that the fibers are in parallel contact with each other. Is placed. In the prior art, the assembly between the retainers is placed in a stress relief frame (see Figure 2b). That is, as shown in FIG. 2A, the optical fiber 1 is a fiber which is placed in the same arrangement groove as a fiber so as not to interfere with the fiber holder, thereby forming a package structure. . On the other hand, in the present invention, with a very thin wall,
The slotted silica capillaries can be held at the top of the stress relief fiber, between the fiber retainers,
The length of the capillary can be maintained as long as possible.

Accordingly, as shown in FIG. 1a, a bare fiber portion 5 of the coated fiber 3 is placed in the middle and a thinned joining area 4 for bonding in the middle.
Then, such a joint region 4 is directly fusion-bonded to the ends of the silica base tube 7 on both sides, solidified, and held. The cross section near the end is similar to the drawing on the right side of FIG. 1b, but the structure of the bond between the fused silica tube substrate and the fiber is as shown in the micrograph of FIG. It has a coupling structure and becomes a primary coupler package. Further, as a secondary stabilizing structure, in the conventional technique, a structure similar to the structure shown in FIG. 1c is formed. It can be fixed, so that its cross section looks like the cross section shown on the right side of FIG. 1c.

The fiber and silica substrate are fused together at the ends of the span (or over the entire span) between the cages. Then, the cage is sufficiently isolated from the arc electrode so that the arc is not disturbed. We show such fusion with an electric arc, a very hot gas torch and a CO ₂ laser. In the form of a fiber device, the non-tapered fibers can be splices, abrasive fibers or fusion couplers while being tensioned between fiber retainers.

[0022]

Example 2 Another example of making a coupler by continuous fusion: There was one modification of the method of making a coupler in which continuous fusion of coupler leads was attached to a silica capillary. Prior to tapering, the two fibers were pre-melted over much longer than usual. This allows the fibers to be fused together at the point where the fibers should be fused to the capillaries at the same time as the stress relief, with a small amount of fusing between the two fiber leads, no matter what the capillaries are in the two fiber assemblies. I was able to ensure stability. FIG. 3 is a photomicrograph showing a cleaved cross section of one fusion point between the coupler reed and the capillary. It shows the advantage of pre-melting as described above.

Primary Package Stability : In conventional packages, an adhesive is applied to cover both the coated and bare fiber lead portions 4, 3 as shown in FIGS. 1 a and b. . Only the coated fiber part 3
Elevated from the primary package, and generally speaking, the coupler can be easily removed from the coupler manufacturing tool, without the risk of fiber breakage, and the secondary as shown in Figure 1c. Can be prepared for a targeted package. On the other hand, in the method of the present invention, once the fiber is fused to the capillary, the fusion point of the fiber is fusion of glass or silica,
Even a slight bend or twist tends to break. Therefore, the primary package cannot be immediately removed from the production tool. However, the primary package can be easily removable from the manufacturing tool by applying adhesive beads to each end of the capillary tube to serve as eyelets that release the fusing point from the fiber leads. The loss of transmission and the coupling ratio do not change during the coupler removal process.

The coupler with such a primary package was subjected to a temperature cycle test at -32 ° C to + 70 ° C for 7 hours. Transmission loss and coupling ratio were monitored during this period. The results are shown in a and b of FIG. The measurement results of each of a and b of FIG. 4 were based on the temperature cycle profile shown in c of FIG. The transmittance loss at -32 ° C is 0.01 dB compared to the room temperature value.
It decreased and increased by 0.01 dB at + 72 ° C. Similarly, the coupler ratio and its comparative value at room temperature are -32 ° C.
It decreased by 0.2% at + 72 ° C and increased by 0.2% at + 72 ° C.

Next, a method for producing a tapered fiber will be described. Tapered fibers require a substrate to be applied after being made. Automatic taperization requires the removal of stress in the taperized fiber. The subsequent substrate fusion treatment is similar to that shown in Example 1, but the fusion to the substrate is limited to only the non-tapered fiber region. 2a
Shows a conventional method 12 in which the fibers are fixed with an adhesive 11 in a silica block 13 and the areas to be joined of the fibers are polished. FIG. 2b also shows a conventional optical fiber packaging structure, in which a fiber 11 is stripped in a silica substrate 14 for bonding.
FIG. 7 is a perspective view showing a state in which is packaged with an adhesive 13.

Further, FIG. 2c shows a structure in which a steel rod 17 is used as a jacket structure and is packaged with a heat-shrinkable thermoplastic resin 16 using the package structure for an optical fiber of the present invention. 9 shows a joint structure for fusion bonding the bare fiber 5 provided in the silica substrate 18. That is, the package body having the bare fibers 5 joined by the fusion spliced portion 15 is fixed in the steel rod 17 via the heat shrinkable thermoplastic 16. This shows fusing a 4-port coupler to a thin-walled slotted capillary, which is done with an electric arc like the cross section of the photograph shown in FIG. A special characteristic of the coupler or its loss is that it is not disturbed.

The package coupler manufactured by the above method shows that the result of the temperature cycle test is comparable to the commercially available coupler using the adhesive. This is surprising in many studies conducted on packages of melt-tapered couplers. However, the fused package of the present invention allows the elongation and contraction of the silica coupler / substrate to be kept away from the elongation and contraction of the adhesive, thus, of course, providing long term stability and reliability. It is more secure than the drug package. Thus, it is clear that fusing fiber leads to silica substrates can be applied to the stabilization of many other fiber devices.

[0029]

As described above, the fiber device of the present invention has the following remarkable technical effects. First, it provided a fiber coupler with performance comparable to that of conventional adhesive-based commercial couplers. Secondly, there has thus been provided an optical fiber packaging structure in which the elongation and contraction of the silica coupler / substrate can be kept away from the elongation and contraction of the adhesive. Thirdly, it is an optical fiber package structure that has improved long-term stability and reliability more reliably than an adhesive package.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a coupling device of a fusion taper portion, a state of a package and a secondary coupling package body, which is performed for a conventional stabilizing package for an optical fiber.

FIG. 2 is an explanatory view showing a contraction structure of a glass block used in a package structure for an optical fiber of the present invention, a conventional abutment coupling package body and a fusion-bonding coupling package body of the present invention.

FIG. 3 is a photomicrograph of the particle structure of a cleaved cross section of one of fusion points between the coupler lead and the capillary in the coupler manufactured according to the present invention.

FIG. 4 is a graph showing the performance obtained as a result of a temperature cycle test of the coupler manufactured according to the present invention.

[Explanation of symbols] 1 optical fiber device 3 coated fiber part 4 thinned fiber part 5, 11 bare fiber part 7 silica substrate tube 8 flexible adhesive 9 outer stainless steel jacket structure 12 splice (joint) 13 Adhesive 14 Silica Block 15 Fusion Bonding Part 16 Heat Shrinkable Thermoplastic Resin 18 Silica Substrate

Front Page Continuation (72) Inventor Karam Crayan Ireland, Limerick, Prassey Technological Park, University of Limerick, Lightwave Technologie Research Center (No Address) (72) Inventor Karalene Fitzgerald Ireland, Limerick, Ireland Prashay Technological Park, University of Limerick, Lightwave Technological Research Center (no address) (72) Inventor Conres Hassey, Limerick, Prassey Technological Park, University of Limerick, Lightwave Technological Research Center (No address)

Claims (1)

[Claims] 1. A packaging structure for an optical fiber device comprising at least a single fiber splice, both when laterally fusing the fibers and when fusing the fibers in a silica substrate. The fibers are placed in parallel contact with the silica substrate, and prior to fusing, the stresses and strains in the fibers are released by heat anneal to remove them. When the silica substrate is directly fused and fixed in the vicinity of both ends, and the silica substrate has the same size as the size of the fiber, the fiber and the silica substrate are subjected to the heating annealing treatment and the fusion treatment at the same time. You can
Further, when the silica substrate is too large, the silica substrate acts as a heating sink, making it difficult to remove stress,
The fiber and the silica substrate are placed in a long heating furnace and subjected to stress relief treatment by a heating anneal treatment, the silica substrate is directly fused and fixed to the fiber, and a silica component is added. A package structure characterized in that it is actually fused and fixed to the silica substrate, and thereby has ultimate stability binding property.