JPH02183207A - Optical fiber polarizer - Google Patents

Abstract

PURPOSE:To obtain the stable optical fiber polarizer which is easy to handle and small in size and has a stable temp. characteristic by providing a stress imparting part having the coefft. of thermal expansion larger than the coefft. of thermal expansion of quartz in a clad in which a core is provided eccentrically near the outer side and further providing a metallic layer on the surface of the clad. CONSTITUTION:The core 1 consisting of Ge-doped SiO2 is disposed eccentrically in the clad 2 consisting of SiO2 and the stress imparting part 4 consisting of B-doped SiO2 is provided on the line connecting the center of the core 1 and the center of a coated fiber 3 and on the central side of the fiber 3. Further, the surface of the clad 2 of the fiber 3 is coated with a metallic layer 5. As a result, the distance from the core 1 to the clad 2 is long in a direction Y and, therefore, the linearly polarized light component having the oscillation component of an electric field in the direction Y hardly bleeds out to the outside of the clad 2 and is hardly absorbed in the metallic layer 5. The polarizer functions as the polarizer to allow the transmission of only the Y polarized light accordingly. The need for combining the polarizer with other optical elements is eliminated and the polarizer which is small in size and easy to handle and has the stable temp. characteristic is obtd. in this way.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an optical fiber polarizer used as a sensor for detecting changes in the external environment using polarized light, and particularly used in the field of optical interference measurement. It is.

(Prior Art) Polarizers using optical fibers have existed for a long time, and the main ones are shown in FIGS. 4 to 7.

The polarizer shown in FIG. 4 uses a birefringent crystal prism 20 in which calcite, which is a birefringent crystal, is cut diagonally. This method utilizes the principle that one of the two polarized waves is totally reflected and deviates from the optical axis.

The polarizer shown in Fig. 5 has a vapor-deposited film (polarization separation film) 24 deposited on a substrate 23 such as glass, and utilizes the fact that the reflection coefficient due to the vapor-deposited film 24 differs between two orthogonal polarized lights. It is.

The polarizer shown in FIG. 6 is made by bending the fixed polarization fiber 25 to increase the bending loss difference between the two orthogonal polarized lights, and the bending loss of the lowest order orthogonal two polarized lights propagating through the fixed polarization fiber 25 is increased. This takes advantage of the fact that it varies depending on the wavelength.

The polarizer shown in Fig. 17 is made by bending an optical fiber 26, polishing the curved part 27, and adhering a metal 28 to the curved part 27, so that the metal 28 absorbs light in unnecessary polarization modes. It is something.

Incidentally, 29 in FIGS. 6 and 7 is a core, 30 is a cladding, and 31 in FIG. 6 is a stress applying portion.

(Problems with the Prior Art) All conventional polarizers use optical fibers, but the optical fiber itself does not have the characteristics of a polarizer, so there are the following problems.

■In addition to the optical fiber, optical parts are required, so assembling them is troublesome. For example, in the case of Figures 4 and 5, the optical axis adjustment of the optical fiber and optical parts must be performed with a μm auto. In the case of Fig. 6, polarization fixed fiber 2
It was necessary to adjust the bending diameter and the number of bending turns in Fig. 5, and in the case of Fig. 7, it was necessary to polish the curved part 27.

(2) Since it is a combination of optical fibers and other optical components, it is inevitably large and difficult to miniaturize.

(2) Since an adhesive is used to fix the optical parts, the adhesive is easily affected by external temperature, resulting in unstable temperature characteristics.

(Objective of the Invention) An object of the present invention is to provide an optical fiber polarizer that is easy to handle, can be downsized, and has stable temperature characteristics by using the optical fiber itself as a polarizer.

(Means for Solving the Problems) The optical fiber polarizer of the present invention has a 1-mode optical fiber 3 consisting of a core l whose main component is quartz and a cladding 2, as shown in FIG. A stress applying portion 4 is provided in the clad 2 eccentrically toward the outside and has a tensile coefficient of IF larger than that of quartz, and a metal layer 5 is further provided on the surface of the clad 2. This is a characteristic feature.

(Function) In the optical fiber polarizer shown in FIG. 1, which is an embodiment of the present invention, since the distance from the core l to the cladding 2 is short in the X direction of FIG. A part of the linearly polarized light component, which has an electric field vibration component, seeps out of the cladding 2 and is absorbed by the metal layer 5, but since the distance from the core l to the cladding 2 is long in the Y direction of FIG. A linearly polarized light component having an electric field vibration component in the Y direction hardly leaks out of the cladding 2 and is hardly absorbed by the metal layer 5. Therefore, the optical fiber polarizer of the present invention functions as a polarizer that transmits only Y-polarized light.

By the way, the wavelength of this optical fiber polarizer of 10 m is 1.3
When the extinction ratio at 0 μm was measured, a value of 50 dB was obtained, confirming that it was a sufficient polarizer.

(Example) FIG. 1 shows an embodiment of the optical fiber polarizer of the present invention.

In this optical fiber polarizer, a Ge-doped 5in2 core l is eccentrically arranged in a cladding 2 made of SiO□, and is located on a line connecting the center of the core 2 and the center of the fiber 3 and on the center side of the fiber 3. In addition, B-doped S i O
A stress applying section 4 consisting of a is provided.

The outer diameter of the core 1 is 8.5 μmφ, and the core 2 on the core 1 is
The distance d between the outer circumferences of is 3.5 μm, and the diameter of cladding 2 is! 2
The distance between the outer circumference of the core I and the outer circumference of the stress applying part 3 is 8 μm, and the outer diameter of the stress applying part 3 is 40 μmφ. Further, the relative refractive index difference of the core 1 was 0.35%, and the 871 degree of the stress applying portion 4 was 20% by weight. LP of this optical fiber polarizer.

The cutoff wavelength of the mode is 1.2 μm, and the wavelength 1.
Single mode operation at 3 μm.

In this example, the surface of the cladding 2 of the optical fiber 3 obtained in this manner is coated with a metal layer 5 with a thickness of 5 μm. It can also be coated.

FIG. 2 shows another embodiment of the optical fiber polarizer of the present invention. In this case, there are two cores 1, and both cores 1 are provided eccentrically toward the outside in the cladding 2, and the diameter of the stress applying portion 4 is made larger than that in the case shown in FIG. In this case, compared to the optical fiber polarizer shown in FIG. 1, the power of the transmitted light propagated through the core I is doubled, which is effective in improving the S/N ratio.

For example, the optical fiber polarizer shown in FIG. 1 can be manufactured as follows.

An imaginary example of a single mode fiber base material 40 without eccentricity as shown in FIG. 3a, obtained by the VAD method, CVD method, etc. !
41 is cut out into a rod shape in the axial direction of the base material 40, and as shown in the figure, the part of the imaginary line 41 becomes the outer peripheral surface and the core l is eccentric, to obtain the material 42. Processed base material 4
2, insert a circular hole 4 parallel to the core l as shown in the same figure C.
3 is opened, a rod 44 having a coefficient of linear expansion larger than that of the cladding 2 is inserted into the hole 43 as shown in d of the same figure, and the processed door material 43 is heated to integrate the base material 43 and the rod 44, The rod-shaped red material 45 thus obtained is drawn while being heated, and the surface of the cladding 2 of the drawn fiber 3 is coated with metal by dipping, sputtering, or the like to form a metal layer 5.

Furthermore, if necessary, the outside of the metal layer 5 is coated with a resin for the purpose of protection.

(Effect of the invention) The optical fiber polarizer of the present invention has the following effects.

Since the CD or optical fiber itself has characteristics as a polarizer, there is no need to bend it or combine it with other optical elements. Therefore, there is no need for bending or combining other optical elements as in the conventional case, and the troubles and problems caused by this are completely eliminated.

■Compact, as there is no need to combine other optical elements;
It becomes easy to handle.

(2) Since there is no need to combine other optical elements, there is no need to use adhesives (therefore, the two-temperature characteristics are stable and less susceptible to external temperature effects).

[Brief explanation of the drawing]

Figures 1 and 2 are front views of different embodiments of the optical fiber polarizer of the present invention, Figure 3 a = d are illustrations for explaining the manufacture of the same polarizer, and Figures 4 and 5 are conventional polarizers. Fig. 6 shows a further different embodiment of the conventional polarizer, and Fig. 6 shows a further different embodiment of the conventional polarizer.
7 is a side view, FIG. 7 is a front view, FIG. 7 is a still different embodiment of a conventional polarizer, FIG. 7A is a side view, and FIG. l is the core 2 is the cladding 3 is the optical fiber 4 is the stress applying part 5 is the metal layer

Claims (1)

[Claims] In a single mode optical fiber 3 consisting of a core 1 and a cladding 2 mainly composed of quartz, the core 1 is eccentrically located toward the outside and is provided within the cladding 2, and has a linear expansion coefficient larger than that of quartz. A stress applying section 4 is provided,
An optical fiber polarizer further comprising a metal layer 5 on the surface of the cladding 2.