JPH036885Y2 - - Google Patents

Description

[Detailed description of the invention] [Background and purpose of the invention] The invention relates to a light source for polarization preserving optical fiber.
Laser diodes (hereinafter abbreviated as LD) are particularly compact and are suitable for greatly stabilizing optical output.
This invention relates to a light source for polarization-maintaining optical fiber using a polarization-maintaining optical fiber.

FIG. 4 is a block diagram of a conventional LD light source for polarization-maintaining optical fiber. The diffused light emitted from the LD chip 11 is converted into parallel light by the spherical lens 12, this light is made linearly polarized by the polarizer 13 placed after it, and then condensed by the hemispherical lens 14. The light is then coupled to a polarization-maintaining optical fiber 15. At this time, the optical axis of the polarization-maintaining optical fiber 15 (in the case of a polarization-maintaining optical fiber with an elliptical jacket or an elliptical core, the direction of the long axis or short axis of the ellipse) is made to match the method of the incident linearly polarized light. Here, the polarizer 13 improves the linear polarization property (polarization ratio) of the light emitted from the LD chip 11, and thereby improves the polarization ratio to about -20 to -40 dB. On the other hand, when using a polarization-maintaining optical fiber LD light source, the polarization-maintaining optical fiber 15
Since a polarization ratio of about -30 dB is required at the output end of the light, the polarizer 13 can be said to be an essential element. However, by using the polarizer 13, the distance between the spherical lens 12 and the hemispherical lens 14 cannot be reduced (the dimensions of the LD light source become larger). In addition, PBS or the like is used as the polarizer 13, but if the polarizer 13 moves slightly on the micro-order (due to temperature, vibration, etc.), the coupling efficiency to the polarization-maintaining optical fiber 15 will fluctuate, and as a result, the polarization A problem arises in that the input to the storage fiber 15 varies.

The present invention has been made in view of the above, and its purpose is to provide a light source for a polarization-maintaining optical fiber that can be made compact and that can significantly stabilize the optical output.

[Summary of the invention] The feature of this invention is that a polarizing layer made of a dielectric multilayer film is provided in a plane passing through the center of the ball lens, and the plane of polarization is preserved in a structure that integrates a conventional ball lens and a polarizer. The point is that it is used as a light source for optical fibers.

[Example] The present invention will be described in detail below with reference to the embodiment shown in FIGS. 1 and 2 and FIG. 3.

FIG. 1 is a cross-sectional view showing an embodiment of a ball lens used in a light source for a polarization-maintaining optical fiber according to the present invention. In FIG. 1, a polarizer layer made of a dielectric multilayer film 3 is formed in a plane passing through the center of a spherical lens (actually made of hemispherical glasses 1 and 2) having an outer diameter of 0.8 to 3 mm. Specifically, 0.4 to 1.5
After forming a flat dielectric multilayer film 3 on hemispherical glasses 1 and 2 having a radius of curvature of mm,
The two planes are aligned and bonded together with an optical adhesive. At this time, anti-reflection coatings 4 and 5 are applied to the curvature surfaces of light input and output for the purpose of preventing reflection. Hereinafter, the ball lens shown in FIG. 1 will be referred to as a polarizer-attached ball lens.

In addition, as a specific example of this dielectric multilayer film 3,
Examples include those having a general film structure in which SiO ₂ and TiO ₂ are alternately laminated.

When the LD light source with the configuration shown in FIG. 4 is constructed using the polarizer-equipped ball lens shown in FIG. 1, the polarizer 13 in FIG.
1. It can be constructed from a spherical lens with a polarizer and a hemispherical lens 14, reducing the number of parts. In addition, the diffused light emitted by the LD chip 11 is converted into linearly polarized parallel light by a polarizer-equipped ball lens, and is condensed by a hemispherical lens 14 to a polarization-maintaining optical fiber 15.
join to. Therefore, it is possible to make the device compact and to significantly stabilize the optical output.

Note that FIG. 2 is a cross-sectional view showing another embodiment of a ball lens with a polarizer, and the same parts as in FIG. 1 are indicated by the same symbols. In FIG. 2, flat parts 6 and 7 for fixing the ball lens are provided on a part of the outer periphery of the ball lens with a polarizer, and by doing so, a new effect is produced in that the assembly of the LD module is facilitated.

Moreover, FIG. 3 is a cross-sectional view of a hemispherical lens showing a modification of the present invention. In FIG. 3, a dielectric multilayer film 8 and an anti-reflection coating 9 are formed on the plane of the hemispherical lens 14 shown in FIG. 4 to form a hemispherical lens with a polarizer. Even if a hemispherical lens with a polarizer as shown in FIG. 3 is used as the hemispherical lens 14 in FIG. 4, the polarizer 13 becomes unnecessary and the same effect can be obtained.

[Effects of the Invention] As explained above, according to the present invention, there is an effect that the device can be made smaller and the optical output can be significantly stabilized.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of a spherical lens used in a light source for a polarization-maintaining optical fiber according to the present invention;
Fig. 2 is a cross-sectional view showing another embodiment of a spherical lens with a polarizer, Fig. 3 is a cross-sectional view of a hemispherical lens showing a modification of the present invention, and Fig. 4 is a conventional polarization-maintaining optical fiber. FIG. 3 is a configuration diagram of an LD light source. 1, 2: hemispherical glass, 3: dielectric multilayer film (polarizer), 4, 5: anti-reflection coating, 6, 7: flat portion.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) The diffused light emitted from the laser diode is converted into parallel light using a ball lens, then linearly polarized using a polarizer, and then condensed using a hemispherical lens to produce polarization-preserving light. In a light source for a polarization-maintaining optical fiber that aligns and couples linearly polarized light with the optical axis of the fiber, the spherical lens has an outer diameter.
A spherical lens of 0.8 to 3 mm is used, and a polarizer layer made of a dielectric multilayer film is provided in a plane passing through the center of the spherical lens, which also functions as the polarizer. A light source for polarization maintaining optical fiber. (2) The light source for a polarization-maintaining optical fiber according to claim 1, wherein the spherical lens having the function of a polarizer has an anti-reflection coating applied to the curvature surface of light input and output. (3) The light source for a polarization-maintaining optical fiber according to claim 1 or 2, wherein the spherical lens having the function of a polarizer has a flat part for fixing on its outer periphery.