JPH02242204A - Optical fiber coupler - Google Patents

Abstract

PURPOSE:To form optical fiber couplers with slight unevenness in characteristics by connecting optical fibers each having a Y-shaped tapered branching part to both ends of a waveguide. CONSTITUTION:Two optical fibers are adhered parallel to each other, melt- bonded by heating and drawn. The central part of the resulting drawn fiber is cut to form a Y-shaped tapered branching part 1. Such parts 1 are connected to both ends of a waveguide 2 having a prescribed shape to produce an optical fiber coupler. Such characteristics as a desired branching ratio can be obtd. independently of conditions in production in accordance with the shape of the waveguide 2 and optical fiber couplers with slight unevenness in characteristics are produced.

Description

[Detailed Description of the Invention] Summary Regarding optical fiber couplers, with the aim of providing optical fiber couplers with small variations in characteristics, the tips of optical fibers arranged in parallel are fused and stretched to form a Y-shaped taper branch, and The above Y is attached to both ends of the shaped waveguide.
FIELD OF THE INVENTION The present invention relates to optical fiber couplers.

In the field of optical communication or optical transmission, which uses optical fibers as transmission paths, multiplexed signal light from multiple channels is transmitted through a single optical fiber in order to distribute transmitted optical signals to multiple devices or for multiplex transmission. An optical coupler is used to introduce the This type of optical coupler includes a micro-optical type that uses optical elements such as lenses and half mirrors, a waveguide type, and a type that uses multiple (for example, two) optical fibers fused and stretched. A fiber fused type (optical fiber coupler) is known. In particular, when the optical transmission line is a single-mode optical fiber, if it is a micro-optical type or a waveguide type, there will be a large loss when converting the optical beam or when connecting to the optical transmission line, so it is not suitable for such applications. It is said that an optical fiber coupler that can be directly connected to an optical transmission line is advantageous. It is known that the shape of the fused/stretched portion of an optical fiber coupler directly affects properties such as branching ratio and loss, and there is a demand for an optical fiber coupler with small variations in properties.

Conventional technology FIG. 6(a) is a diagram for explaining the structure and function of an optical fiber coupler in a film, and FIG.
b) A cross-sectional view along the line.

This optical fiber coupler consists of a light input section 22.24, a fusing/stretching section 26, and a light output section 28.30. In the fusion/stretching section 26, the diameters of portions 26a and 26b corresponding to the core of each optical fiber are smaller than the original core diameter, and these portions 26a and 26b are sufficiently close to each other, so that fusion is not possible. Mode coupling occurs depending on the length of the connecting/extending portion 26, etc., and a predetermined branching ratio can be obtained. That is, the optical power from the optical input section 22 or 24 is P. When the signal light of
Optical powers P, , P, respectively from 0 at predetermined branching ratios.
An optical signal of 1 is output. With this configuration, it is possible to connect directly to a single-mode optical fiber, so the loss of optical power is small, and since the only component is the optical fiber, it is highly reliable against usage environmental conditions such as temperature and humidity. be able to. Note that the excess loss of the future fog is calculated as 10 using the above input and output optical powers.
It is expressed as Log ((P++P2)/P'o), and the branching ratio is expressed as P,/(P,+P,) or P2/(Pl+P2).

Problems to be Solved by the Invention The most common conventional manufacturing method for the optical fiber coupler shown in FIG. The fused/stretched portion is formed by fusion bonding and stretching the fused portion. Properties such as branching ratio are controlled by actually guiding light through the optical fiber during fusion and stretching, and by monitoring in real time. For this reason, there was a problem in that constant properties could not always be obtained due to distortion during the cooling process after completion of fusing and stretching.

The present invention was created in view of these problems.
The purpose is to provide an optical fiber coupler with small variations in characteristics.

In other words, instead of forming a coupling section, a separate coupling section (waveguide section) is prepared in advance, and Y-shaped taper branch sections are connected to both ends of this waveguide section. Depending on the shape of the waveguide, desired characteristics such as branching ratio can be obtained without being influenced by manufacturing conditions. Therefore, when a plurality of optical fiber couplers are provided, variations in their characteristics are small.

Means to solve problems FIG. 1 is a diagram showing the basic configuration of the present invention.

This optical fiber coupler forms a Y-shaped taper branch 1 by fusing and stretching the tips of optical fibers arranged in parallel, and the Y-shaped taper branch 1 is attached to both ends of a waveguide 2 having a predetermined shape. They are connected and configured.

Function: In the optical fiber coupler of the present invention, unlike the conventional one, the optical fiber serving as the branch part is directly touched and stretched.

FIG. 2 is a block diagram of an optical fiber coupler showing an embodiment of the present invention. In this embodiment, an optical fiber coupler is constructed by forming a waveguide section 3 from a quartz fiber having a -like refractive index, and fusion-splicing Y-shaped taper branch sections 4 to both ends of the waveguide section 3. The shape of the waveguide section 3 is a cylindrical shape with a diameter of 15 μm and a length of about 3.5 μm when this optical fiber coupler is a 1.3 μm band OdB coupler, and
In the case of a multiplexer/demultiplexer for the 1°3 μm band and 1.55 μm band, it has a cylindrical shape with a diameter of 15 μm and a length of about 9.5 mm. Note that the refractive index of the waveguide section 3 is desirably made equal to the refractive index of the core section of the optical fiber constituting the Y-shaped taper branch section 4 in order to prevent an increase in reflection loss.

There are two methods for creating the Y-shaped taper branch 4. The first method is a method in which two optical fibers are brought into close contact with each other at the side surfaces, heated, fused and stretched, and then cut approximately at the center of the fused and stretched portion.

According to this method, two Y-shaped taper branches can be created in one operation. The second method is to bring two optical fibers into close contact with each other at their ends, and heat the fibers while gripping them with a suitable gripper to fuse and stretch them. This method provides one Y-shaped taper branch in one operation.

FIG. 3 is a diagram for explaining a method of connecting the Y-shaped taper branch section 4 and the waveguide section 3. The end faces of the Y-shaped taper branch 4 and the waveguide 3 are brought into close contact with each other, and the contact portion is connected to the discharge electrode 5.
6 and generates an arc discharge between the discharge electric fields 5 and 6 to perform fusion splicing. According to this method, since the change in shape of the connecting portion is minute, changes in characteristics due to change in shape are suppressed and variations in characteristics are reduced. Note that the taper ratio (rate of change in core diameter in the fiber axial direction) of the Y-shaped taper branch portion 4 is desirably small in order to improve loss characteristics.

FIG. 4 is a block diagram of an optical fiber coupler showing another embodiment of the present invention. In this embodiment, a waveguide section 8 made of a quartz-based waveguide is formed on a substrate 7, and Y-shaped taper branch sections 4 having the same configuration as in the previous embodiment are connected to both ends of the waveguide section 8. Reference numeral 9 denotes a guide formed on the substrate 7 in the same manner as the waveguide section 8, and determines the position of the Y-shaped taper branch section 4.

An optical adhesive can be used to fix the Y-shaped taper branch 4 to the substrate 7 and to connect the Y-shaped taper branch 4 and the waveguide 8.

FIG. 5 is a diagram for explaining a method of forming the waveguide section 8 and the guide 9 on the substrate 7. As shown in FIG. First, as shown in FIG. 3A, a quartz film 10 having a uniform thickness is formed on a substrate 7 made of Si by, for example, the CVD method. Next, as shown in FIG. 4B, a mask M is applied to leave the portions that will become the waveguide section 8 and the guide 9. Then, a portion of the quartz film 10 where the mask M is not formed is etched to form a waveguide section 8 and a guide 9 made of quartz having a predetermined shape, as shown in FIG. According to this method,
Since the thickness, width and length of the waveguide section 8 can be freely set,
Optical couplers with arbitrary characteristics can be provided without variations in characteristics.

According to the embodiment described above, it is possible to provide an optical coupler with arbitrary characteristics depending on the shape of the waveguide section 3 or 8, so by setting these shapes with high precision, it is possible to reduce the variation in characteristics. We can provide optical fiber bacabula.

As described in detail, according to the present invention, a separate waveguide section is prepared in advance, and Y-shaped Tenoscopic branch sections are connected to both ends of the waveguide section, so that light with small characteristic variations can be obtained. This has the effect of making it possible to provide a free vacabula.

[Brief explanation of drawings]

Figure 1 is a diagram showing the principle of the present invention; Figure 2 is a diagram showing the configuration of an optical fiber coupler showing an embodiment of the present invention; Figure 3 shows the waveguide section and Y-shaped taper in the optical fiber coupler shown in Figure 2. An explanatory diagram of a connection method with a branch part, FIG. 4 is a configuration diagram of an optical fiber coupler showing another embodiment of the present invention, and FIG. 5 is a diagram showing a waveguide section and guide on a substrate in the optical fiber coupler shown in FIG. 4. FIG. 6 is a diagram showing the configuration of a general optical fiber. 1.4... Y-shaped taper branch, 2.3.8... Waveguide, 7... Substrate.

Claims (1)

[Claims] A Y-shaped taper branch part (1) is formed by fusing and stretching the tips of optical fibers arranged in parallel, and the Y-shaped taper branch part (1) is formed at both ends of a waveguide part (2) having a predetermined shape. An optical fiber coupler characterized by connecting taper branch parts (1).