JPH02259704A - Wide wavelength optical fiber coupler - Google Patents

Abstract

PURPOSE:To accomplish a wide wavelength optical fiber coupler by fusing and connecting an optical fiber having the same clad outside diameter as an optical fiber A, one of two optical fibers A and B having different clad outside diameters, to the optical fiber B and fusing and drawing both fibers A and B in the vicinity of the fusing and connecting point of both fibers A and B. CONSTITUTION:The single mode optical fiber 43 whose clad outside diameter is 110mum and the single mode optical fiber 41b whose clad outside diameter is 125mum are fused and connected at the fusing and connecting point 45. Thereafter, the optical fiber 43 whose clad outside diameter is 110mum and the optical fiber 41a whose clad outside diameter is 125mum are fused and drawn in the vicinity of the fusing and connecting point 45 to form a fused and drawn part 46, and the wide wavelength optical fiber coupler whose wavelength is 1.30mum-1.55mum and coupling degree is 50%+ or -3% is produced. In this optical fiber coupler, the optical fiber whose clad outside diameter is 125mum is easily connected to both optical fibers on one end. Then, the optical fiber coupler with 1X2 terminals where the optical fiber 43 of clad outside diameter 110mum is not needed in substance is obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is an optical fiber coupler used for branching optical signals in optical communication systems, sensors, etc., which has a small wavelength dependence of the optical branching ratio. This invention relates to a wide wavelength optical fiber coupler.

(Prior art) In optical transmission systems such as subscriber systems, optical signals propagating through one transmission path are branched into multiple propagation paths, or optical signals from multiple transmission paths are transmitted through one transmission path. The demands superimposed on roads are rapidly increasing. One of the parts that performs this function is an optical fiber cambra. Optical fiber couplers have the characteristics of low loss, excellent connectivity with optical fibers that are light transmission lines, and low cost. Several methods have been considered for producing optical fiber couplers, but the method of fusing and drawing is the most productive, and the price is expected to continue to drop rapidly in the future.

Among optical fiber couplers, a wide wavelength optical fiber coupler whose optical branching ratio has little wavelength dependence is particularly important. Broad wavelength optical fiber coupler has international application number PCT/GB8610044
As shown in Figure 5, mainly one of the two optical fibers
This is achieved by pre-stretching the book (hereinafter referred to as pre-stretching). For example, the curve (a
), in a basic symmetric optical fiber coupler, the optical branching ratio changes periodically between 0% and 100% depending on the wavelength of the optical signal. On the other hand, broadband optical fiber couplers make the propagation constants of two optical fibers asymmetric by pre-stretching one optical fiber, and as a result, the coupling characteristics become as shown in curve (b) in Figure 4. , the 50% coupling becomes almost flat between wavelengths of 1.3 μm and 1.5 μm. However, the production of a wide wavelength optical fiber coupler by this pre-stretching has problems such as difficulty in uniform pre-stretching and the tendency for the optical fiber to bend during fusion. For this reason, it is more difficult to control the branching ratio and suppress excess loss than with symmetrical optical fiber couplers, and the production yield is low.

As another manufacturing method for realizing a wide wavelength optical fiber coupler more easily and with higher yield than the conventional pre-stretching method, there is a method of using two optical fibers with different cladding outer diameters as shown in FIG. Here, 21a and 21b are cores and have the same parameters, and 22a and 22b are claddings that have different outer diameters. As a result, when two optical fibers are fused and stretched, asymmetry appears in the propagation constant of the optical fiber at the stretched portion.

Unlike the pre-stretching method, this method is characterized by the ability to accurately control asymmetry. However, the drawback of this method is that it is difficult to connect optical fibers of the same diameter because the implementation is as shown in FIG. Here, 31 is an optical fiber coupler, 32a and 32b are optical fibers with different clad outer diameters, 33a, 33b, 33c, and 33d are adhesives, and 3
4 (the board, 35 is the case).

(Problems to be Solved by the Invention) The present invention provides the ability to connect optical fibers of the same diameter to both ends of the optical fiber coupler when producing a wide wavelength optical fiber coupler using two optical fibers with different clad outer diameters. The purpose of the present invention is to provide a wide wavelength optical fiber cambra with a structure.

(Means for Solving the Problems) In the wide wavelength optical fiber coupler of the present invention, when producing a wide wavelength optical fiber coupler using two optical fibers having different cladding outer diameters, the same cladding as one optical fiber is used. By fusion splicing the outer diameter optical fibers near the fusion splicing/stretching, the optical fibers from both ends after mounting are made to have the same diameter.

That is, in an optical fiber coupler manufactured by mutually fusing and stretching two single-mode optical fibers A and B with different cladding outer diameters, an optical fiber with the same cladding outer diameter as optical fiber A is used in advance. Fusion splicing is performed on fiber B, and optical fibers A and B are fused and stretched near the fusion splicing.

(Example) The present invention will be specifically described in detail below with reference to the drawings. The examples disclosed below are merely illustrative of the invention and are not intended to equally limit the scope of the invention.

Fig. 1 is a structural diagram of an embodiment of the present invention, in which 41a,
41b is an optical fiber with a cladding outer diameter of 125 μm, 43
42a is an optical fiber with a cladding outer diameter of 110 μm.

42b, 44 are cores with a relative refractive index Δ=0.3% and a cut-off wavelength of 1.201 tm, 45 is a fusion splicing point, 4
6 is a fused and stretched portion.

As shown in FIG. 1(a), after fusion splicing the single mode optical fiber 43 with a cladding outer diameter of 110 μm and the single mode optical fibers 41a and 41b with a cladding outer diameter of 125 μm, as shown in FIG. ), the cladding outer diameter 110
An optical fiber 43 with a wavelength of 1.3 μm and optical fibers 41a and 41b with a clad outer diameter of 125 μm are fused and stretched.
After producing a wide wavelength optical fiber coupler with a coupling degree of 50%±3% at 0 μm = 1.55 μm, it was mounted in a case as shown in FIG. The loss of the manufactured optical fiber coupler was 0.20 dB. This optical fiber coupler has a crand outer diameter of 125 μm on both optical fibers at one end.
Optical fibers can be easily connected.

In this invention, it is not possible to connect optical fibers with the same diameter to both ends of the optical fiber coupler, but since there is generally a stronger demand for optical fiber couplers with 1 x 2 terminals than with 2 x 2 terminals, optical fibers with different cladding outer diameters cannot be connected. Practically unnecessary.

Embodiment 1 FIG. 3 shows an embodiment in which optical fibers having the same diameter can be connected to both 2×2 terminals. Here, 51a.

51b and 51c are optical fibers with a cladding outer diameter of 125 μm, 53 are optical fibers with a cladding outer diameter of 110 μm, and 52
a.

52b, 52c, 54 are cores having a relative refractive index Δ-0.3% and a cut-off wavelength of 1.20 μm; 55a, 5
5b is a fusion splicing point, and 56 is a fusion extension part.

As shown in Fig. 3(a), the cladding outer diameter is 110 μm,
After fusion splicing single mode optical fibers with a cladding outer diameter of 125 μm7 to both ends of a single mode optical fiber 53 having a length of 2C11, the optical fiber 53 with a cladding outer diameter of 110 μm is formed as shown in FIG. 3(b). and cladding outer diameter 125μm
The optical fibers 51a, 51b, and 51c are fused and stretched, and the wavelength is 1.3011 m - 1.60 pm with a wavelength of 50% ±
After producing a 4% coupling wide wavelength optical fiber coupler, it was mounted in a case as shown in FIG. The loss of the manufactured optical fiber coupler was 0.15 dB.

To this optical fiber coupler, an optical fiber having a cladding outer diameter of 125 μm can be easily connected to both ends.

In the present invention, an optical fiber coupler with a cladding outer diameter of 125 μm and 110 μm is used as an example, but an optical fiber coupler with a cladding outer diameter of 125 μm and 135 μm is also possible.Furthermore, the cladding outer diameters of both optical fibers are different. (Effects of the Invention) As described above, the wide wavelength optical fiber coupler of the present invention is a wide wavelength optical fiber coupler that uses two optical fibers with different cladding outer diameters. When manufacturing, an optical fiber with the same cladding outer diameter as one optical fiber is fusion spliced near the fusion/stretching area and then mounted, so it is different from a normal optical fiber coupler made from standardized optical fiber. Similarly, standardized optical fibers can be easily connected.

[Brief explanation of drawings]

Fig. 1 is a structural diagram of one embodiment of the present invention, Fig. 2 is a mounting configuration diagram of an optical fiber coupler used in the present invention, Fig. 3 is a structural diagram of another embodiment of the present invention, and Fig. 4 is a conventional FIG. 5 is a diagram showing the cross-sectional structure of the optical coupling part of the broadband optical fiber coupler. 2]a, 21b...core 22 with the same parameters
a, 22b... Cladding 31 with different outer diameters... Optical fiber coupler 32a, 32b... Optical fibers 33a, 33b, 33c, 33d with different cladding outer diameters - Adhesive 34
... Substrate 35 ... Case 41a, 41b ... Optical fiber 43 with cladding outer diameter of 125 μm... Optical fiber 42a, 42b, 44 with cladding outer diameter 110 μm = Core 45 ... Fusion splicing point 46. ...Fused extension parts 51a, 51b, 51cm cladding outer diameter 125p
Optical fiber 53 of m...optical fiber 52a with cladding outer diameter of 110 μm
, 52b, 52c; 54-core 55a, 55b
...Fusion splicing point 56...Fusion extension part Fig. 1 (a) 4fa, 4fh ------- Crut outer diameter/25/J
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Crack F Tato diameter! fOpmo light flyer 46---
-----------Kon's low-grade part 2nd figure 3f--1-----------Child 7 end Ibekatsuara 32a 32f)-------------Krat' 3 optical fiber I with a diameter of 0 / 33a, 33j, 3:3c, 33d-+94 agent 34-
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Claims (1)

[Claims] 1. In an optical fiber coupler produced by mutually fusing and stretching two single mode optical fibers A and B with different cladding outer diameters, an optical fiber with the same cladding outer diameter as optical fiber A is prepared in advance. Optical fiber B
A wide wavelength optical fiber coupler characterized in that optical fibers A and B are fused and stretched in the vicinity of the fusion spliced.