JPH0518722Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a polished optical fiber coupler constructed using optical fibers.

<Prior Art> FIG. 4 shows a perspective view of a conventionally used optical fiber coupler. In the figure, reference numeral 1 denotes a pair of substrates made of, for example, fused silica glass, and each substrate is embedded with an optical fiber 2 consisting of a cladding and a core, so that, for example, light incident from the a side is split into predetermined directions to the b and c sides. Branched by ratio.

5a to 5c are diagrams schematically showing the manufacturing process of the optical fiber coupler, in which a groove 8 for embedding an optical fiber is formed in the substrate 1 with a radius of curvature r, and the optical fiber 2 is inserted along the curved surface of this groove. It is a perspective view showing the buried/fixed state. The width of the embedding groove 8 is the same as or slightly larger than the outer diameter of the optical fiber 2, and the depth is such that the top of the cladding 3 of the optical fiber buried along the groove 8 is slightly lower than the surface of the substrate 1. Process. b is a perspective view showing a state in which the portion of the surface of the substrate 1 indicated by the dotted line has been polished. Polishing is performed until the distance between the cladding of the optical fiber and the core 4 is several μm (note that this distance is difficult to measure in practice, so the final amount of polishing is determined while measuring the amount of transmitted light. c is It is a perspective view showing the state before fixing the two substrates manufactured in steps a and b above.In this case, the substrates are stacked and fixed so that the portion of the polished clad shown by e is in close contact with each other.

According to the above configuration, the two cores are fixed in close proximity to each other within several μm. When the cores approach each other in this manner, light does not propagate through each core independently, but propagates while exchanging optical power with each other. Therefore, when light is incident on one core, the light is coupled to the other core. Therefore, the required branching ratio can be obtained by adjusting the distance between the two cores and the length of the connecting portion.

<Problems to be solved by the invention> By the way, when fixing the optical fiber coupler with the above configuration, the substrates are brought into close contact with each other and liquid adhesive is soaked from the mating surfaces to fix them. In this bonding method, as shown in FIG. 6, the adhesive 5 penetrates into the spaces between the claddings 3 (the gaps are exaggerated in the figure).

Figure 7 shows the changes in crosstalk and branching ratio with respect to temperature changes in the optical fiber coupler fabricated in this way. According to the figure, as the temperature decreases, the crosstalk deteriorates, and the branching ratio decreases at low temperatures. It is increasing as time goes by. The cause of the decrease in crosstalk is shrinkage of the adhesive, and the deterioration of the branching ratio is due to a change in the refractive index of the adhesive.

The present invention has been made in view of the problems of the prior art described above, and an object of the present invention is to provide an optical fiber coupler that improves crosstalk and deterioration of branching ratio due to temperature changes.

<Means for solving the problems> The configuration of the present invention to solve the above problems is as follows: An optical fiber consisting of a cladding and a core part, and an optical fiber formed with a predetermined radius of curvature r in the depth direction of the substrate surface. The substrate has the optical fiber embedding groove, and the groove having the radius of curvature r has a depth such that when the optical fiber is buried/fixed, the top of the cladding along the curved surface is slightly lower than the surface of the substrate, and Polish the surface on the side where the optical fiber is buried together with the cladding to expose the core.
Remove up to m front, and make two of the substrates into a set,
In an optical fiber coupler in which the clads on the polished sides are brought into contact and fixed, an adhesive blocking groove is provided on at least one side of the substrate across the optical fiber embedding groove, and only the outer side of the adhesive blocking groove is provided. The two substrates are bonded together by applying an adhesive to the substrate.

<Example> Hereinafter, an example of the present invention will be described based on the drawings. FIG. 3 is a perspective view showing a state in which adhesive blocking grooves 9 are formed across an optical fiber embedded/fixed in the substrate. Note that the steps up to burying/fixing the optical fiber are the same as in the conventional example. Further, the position and width of the adhesive blocking groove are such that sufficient adhesive strength can be maintained in the area formed between the groove and the side surface, but the shape of the bottom surface of the groove is arbitrary.

FIG. 1 is a sectional view showing an embodiment of the optical fiber coupler of the present invention. In this example, grooves 9 for blocking adhesive are formed in both substrates (the gap is exaggerated in the figure). ing).

According to the above structure, even if the adhesive 5 is poured from the side surface of the two substrates together, the adhesive will be blocked by the adhesive blocking groove 9 and will not advance to the cladding side.

FIG. 2 is a sectional view showing another embodiment. In this embodiment, an adhesive blocking groove is formed only on one side of the substrate. However, in such a configuration, it is necessary to pour the adhesive with the substrate side where the adhesive blocking groove 9 is located facing downward.

<Effects of the Invention> As explained above in detail with the embodiments, according to the present invention, a groove for blocking the adhesive is provided on at least one side of the substrate, so that the adhesive does not penetrate into the cladding side. do not have. As a result, it is possible to realize an optical fiber coupler that is free from crosstalk and deterioration of branching ratio due to temperature changes.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing one embodiment of the present invention;
The figure is a cross-sectional view showing another embodiment, FIG. 3 is a perspective view showing a state in which adhesive blocking grooves are formed on the substrate, FIG. 4 is a perspective view showing a conventional example, and FIG. 5 is a schematic diagram of the conventional example. FIG. 6 is a perspective view showing the manufacturing process, FIG. 6 is a diagram showing a conventional example in which adhesive penetrates between the substrates, and FIG. 7 is a diagram showing changes in crosstalk and branching ratio with respect to temperature changes of the optical fiber coupler. DESCRIPTION OF SYMBOLS 1... Substrate (fused silica glass, etc.), 2... Optical fiber, 3... Clad, 4... Core, 8... Groove for embedding optical fiber, 9... Groove for blocking adhesive.

Claims (1)

[Scope of utility model registration request] consisting of an optical fiber consisting of a cladding and a core part, and a substrate having a groove for embedding the optical fiber formed with a predetermined radius of curvature r in the depth direction of the substrate surface,
the groove having the radius of curvature r embeds an optical fiber;
When fixed, the top of the cladding along the curved surface is at a depth slightly lower than the surface of the substrate, and the surface on the side where the optical fiber is buried is polished together with the cladding to remove it several μm before the core is exposed. In an optical fiber coupler in which the two substrates are fixed together with the polished clads in contact with each other, an adhesive blocking groove is formed in at least one of the substrates with the optical fiber embedding groove sandwiched therebetween. An optical fiber coupler characterized in that the two substrates are bonded together by attaching an adhesive only to the outside of the adhesive blocking groove.