JPS6017083B2 - Method for manufacturing fiber polarizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a polarizer, and particularly to a method for manufacturing a fiber polarizer that can be easily connected to an optical fiber and has low insertion loss.

Conventionally, the method for manufacturing fiber polarizers has been to wear down only one side of the cladding of a single-mode optical fiber to the vicinity of the core, and then evaporate metal such as aluminum or gold at approximately 1500 A onto the cladding. .

The principle is in the following [1}, ■.

'1} By increasing the difference in the attenuation constant between the TEo mode in which the electric field vector is parallel to the metal surface and the TMo mode in which the electric field vector is perpendicular to the metal surface, the TEo
Propagate only the mode.

(Using the cutoff of the 2'TEo mode, only the TMo mode is propagated. Figure 1 shows the cross section of the fiber polarizer obtained by the above manufacturing method.
'b is a sectional view of the female side.

Reference “Electron.Le ratio., Vol.10
M. 20, P. 762, 1980'' In FIG. 1, 1 is the core, 2 is the cladding, and 3 is the metal. However, with this method, the roughness of the boundary between the metal and the glass poses a problem, making it difficult to reduce insertion loss.

Furthermore, since small dimensions such as optical fibers are processed, there are problems with accuracy and mass productivity. Another method is to use a birefringent crystal (KB508, 4 days 2
0), and by utilizing the difference in waveguide structure for TEo mode and TMo mode, only one of the TEo mode or TMo mode is radiated from the 0 fiber to the crystal, and only the other mode is propagated. A method was also implemented.

Reference book “Optics Lett., Vol.5 No.
．． 11, P. 479, 1 Group 0'' However, this method also had the drawback that the above-mentioned problems could not be solved.

In order to eliminate these drawbacks, the present invention provides a method for manufacturing a fiber polarizer that is easy to manufacture, can be mass-produced, and can be easily connected to fibers.
The present invention will be explained in detail below with reference to the drawings. FIG. 2 shows the steps for producing a matrix for a fiber polarizer according to the present invention.

FIG. 2a shows an optical fiber motherboard fabricated by the usual MCVD method or VAD method, with a core fiber o. 8 objects, about 16 outer walls, and a refractive index difference of 0.2%.

Here, core 1 is Si02+Ge02, and cladding 2 is Si02+Ge02.
It is 02. Next, this base material is processed to produce a semi-cylindrical base material.

Figure 2b shows the base material thus produced, with the cladding on one side being worn down to the vicinity of the core and the surface polished.

The distance between the core and the polished plane is on the 0.5 side. Second
Figure c shows Si020P2Q+ produced by VAD method.
The string 03 glass rod 4 is processed into a semi-cylindrical shape.

The radius is approximately 8 ribs and the refractive index is equal to that of Si02. Figure 2 d shows the base material in Figures 2 b and c with an outer diameter of 18 sails.
It is inserted into a jacket tube 5 made of a quartz tube with an inner diameter of 16.5 ribs, and heated to about 1900 qo with an oxyhydrogen burner to integrate it.

This becomes the final base material for the fiber polarizer. Next, this base material is drawn to produce a fiber.

The outer diameter of the fiber is about 187 French m, the core diameter is 9.35 French m, and it is coated with urethane and silicon. The fiber cross section is similar to FIG. 2d, only the dimensions are smaller. A portion of the fiber (approximately 3 arcs) is then stripped and etched using 49% HF.

Etching rate of Si02 glass and Si020P20
The etching rate ratio of 50 Sumi 03 glass is approximately (pine OA/
sec)/(5000A/sec), the Si020P230B203 portion on one side of the fiber is completely removed, resulting in a structure as shown in FIG. Etching is further continued, and the etching is terminated when the etching reaches the outer periphery of the core as shown in FIG. The outer diameter of the fiber after etching is approximately 7 mm, the core diameter is 9.35 mm, and the fiber is extremely eccentric. Next, Au is deposited to a thickness of about 0.1 m on this polarizing fiber portion. Vapor deposition is carried out using a conventional milling machine or sputtering equipment. Figure 5a
5 is a perspective view of the fiber polarizer produced in this manner, and FIG. 5b is a diagram showing the state in which the fiber polarizer and optical fibers are connected according to the present invention.

Since both ends of the fiber polarizer 7 according to the present invention are ordinary optical fibers 6 with the core at the center, connection with other optical components is easy. Note that in this example, etching was performed to the outer periphery of the core, but the etching is not necessarily limited to this, and it is also possible to leave a buffer layer between the core and the metal.

Further, the metal for vapor deposition is not limited to Au', and it is expected that a large extinction ratio can be obtained by using A. In addition, although 49% HF was used as the etching solution, using a mixed solution (buffered hydrofluoric acid) with a ratio of ammonium fluoride and 49% HF of 9:1 makes the etched surface flat.
Insertion loss can be reduced.

As explained above, the method for manufacturing a fiber polarizer according to the present invention is easy to manufacture because there is no step of wearing and polishing small dimensions such as fibers, which was conventionally done. There are advantages.

Furthermore, by using an appropriate etching solution such as buffered hydrofluoric acid, it is possible to suppress the roughness of the fiber surface after etching, which not only reduces insertion loss but also allows the core to be located at the center of the fiber at both ends of the polarizer. It has the advantage of being easy to connect with other fibers.

[Brief explanation of the drawing]

1a and 1b are joint cross-sectional views and side sectional views of a fiber-type polarizer produced by the follow-up method; FIGS. 2a-d are views showing the steps of manufacturing a glass base material for a polarizer according to the present invention; and FIG. The figure is a schematic diagram showing the etched state of the fiber, Figure 4 is a schematic diagram of an eccentric fiber before metallization, Figure 5a is a perspective view of a fiber polarizer according to the present invention, and Figure 5b is a diagram according to the present invention. FIG. 3 is a diagram showing a connection state between a fiber polarizer and an optical fiber. 1... Core, 2... Clad (Si02 glass), 3...
...Metal (Au) 4...Si020P2050B20
3 Glass, 5... Jacket tube, 6... Optical fiber, 7
...Fiber type polarizer. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1 A base material for a silica optical fiber consisting of a concentric core and a cladding is processed into a semi-cylindrical base material so that the core remains, and then the refractive index of the cladding of the semi-cylindrical base material is A glass base material whose etching rate is equal to the etching rate and which is faster than the cladding of the semi-cylindrical base material with a hydrofluoric acid etchant is combined, inserted into a quartz tube, drawn to form a fiber, and the fiber is etched with a hydrofluoric acid etchant. 1. A method for producing a fiber polarizer, which comprises etching the fiber until the core is exposed, and forming a metal film on the exposed core.