JPS62218922A - Laser diode module - Google Patents

Abstract

PURPOSE:To reduce noise and to stabilize the operation of a laser diode module by disposing a polarized light separating plate, thin film Faraday rotor which rotates the polarization plane of light 45 deg. by a magnetic field and optical isolator formed of a polarizing lens to the exit end of a polarization plane maintaining optical fiber. CONSTITUTION:The exit end of the laser diode module consisting of the polarization plane maintaining optical fiber 2 for leading the exit light from the laser diode 10 to the outside is provided with a connector 1 consisting of a metal, for example, stainless steel, etc., and contg., the polarized light separating plate 4, the thin film type Faraday rotor 5 which is housed in a magnet 3 consisting of a samarium cobalt, etc. capable of generating a powerful magnetic field and consists of a ferromagnetic crystal such as GdBiIg having large Faraday rotating power and the optical isolator which is constituted of the polarizing lens 6. Light 7 emitted from the polarization plane maintaining optical fiber 2 is separated by the polarized light separating plate 4. The separated exit light 7 is rotated by the thin film type Faraday rotor 5 and is condensed by the polarizing lens 6.

Description

[Detailed Description of the Invention] [Summary] A laser diode module used in a transmitting device for optical fiber communication, which uses a polarization-maintaining optical fiber, has an optical isolator configured at the output end of the laser diode module to provide remote control. Eliminate edge reflections and improve the characteristics of the transmitter.

[Industrial application field]

The present invention relates to a laser diode module used in a transmitter for optical fiber communication, and particularly to a laser diode module in which an optical isolator is provided at the output end of a polarization-maintaining optical fiber.

As optical communication technology becomes more widespread, there is an urgent need to develop various components that make up optical communication systems.

For example, it is an optical isolator that suppresses noise caused by light returning to the transmitter of a communication device using a polarization-maintaining optical fiber. Since this returned light causes fluctuations in the optical output of the laser diode module, resulting in noise, there is a strong demand for an optical isolator that suppresses the noise caused by this returned light.

[Conventional technology]

Conventional laser diode modules with polarization-maintaining optical fibers either do not include an isolator and are vulnerable to the return of reflected light from the end of the optical fiber, or have an optical isolator built into the junction between the laser diode and the optical fiber. It has a strong structure.

[Problem that the invention seeks to solve]

In the above-mentioned conventional laser diode module with polarization-maintaining optical fiber, far-end reflection (return light) to the extent required for a laser diode (approximately 4%) cannot be avoided, resulting in unstable operation and increased noise. In addition, built-in isolators have their own problems, such as limited coupling methods.

[Means for solving problems]

In order to solve the above problems, the present invention provides a laser diode module attached to the output end of a laser diode module using a polarization maintaining optical fiber.

That is, in a laser diode module consisting of a polarization maintaining optical fiber for guiding the emitted light from the laser diode to the outside, at the output end of the polarization maintaining optical fiber,
This problem is solved by providing an optical isolator consisting of a polarization splitting plate, a thin film Faraday rotator that rotates the plane of polarization of light by 45 degrees using a magnetic field, and a polarizing lens.

[Effect]

The optical isolator connector described above is attached to the output end of a laser diode module that uses a polarization-maintaining optical fiber to eliminate light returning to the transmitter, which causes noise, and to stabilize the operation of optical fiber communication equipment. Become.

〔Example〕

FIGS. 1 and 2 are diagrams for explaining one embodiment of the present invention, with FIG. 1 being a side sectional view and FIG. 2 being an enlarged view of the optical system.

In the figure, a laser diode 1
At the output end of a laser diode module consisting of a polarized optical fiber 2 for guiding the output light from 0 to the outside,
Consists of a polarization splitting plate 4, a thin film Faraday rotator 5 made of a ferromagnetic crystal such as GdB11G with a large Faraday rotation ability, housed in a magnet 3 made of samarium cobalt or the like that can obtain a strong magnetic field, and a polarizing lens 6. The optical isolator is assembled into a fully bendable connector 1 made of, for example, stainless steel. The light 7 emitted from the polarization-maintaining optical fiber 2 is separated by a polarization separation plate 4, and the separated emitted light 7 is rotated by a thin-film Faraday rotator 5 and condensed by a polarizing lens 6.

Figure 3 is a diagram explaining the operating principle of an optical isolator.
In the figure (al is a beam of forward direction light, (b) is a beam when backward light is shifted, and (C) is a beam when backward light is spread.

As shown in FIG. 3(a), the forward emitted light 7 from the polarization-maintaining optical fiber 2 is a uniaxial beam that faces the Rochon polarizing prism or the end face of the polarization-maintaining optical fiber 2 and forms an inclined surface. Although the incident light is incident on the polarization separation plate 4 made of crystal, the incident light is not polarized. This unpolarized light is then rotated and deflected by 45° by a Faraday rotator 5 and condensed by a polarizing lens 6.

The polarizing lens 6 is made of a uniaxial crystal, and its optical axis is perpendicular to the polarization plane of the light after passing through the Faraday rotator 5, so that the light passes through the polarizing lens 6 with the refractive index n of ordinary light.
The light is focused at o and tied to a single point.

As shown in Figure 3 (bl), the feedback light 8 having the same polarization as the forward light from the polarization maintaining optical fiber 2 is condensed by the polarizing lens 6.The refractive index at that time is n, o. The polarization of this focused feedback light 8 is rotated by the Faraday rotator 5,
Since the beam is polarized perpendicularly to the forward direction by the polarization separation plate 4, the direction of the beam is shifted, so that it is not focused on the core portion of the polarization-maintaining optical fiber 2.

As shown in FIG. 3(C), the feedback light 9 having a polarization orthogonal to the forward light from the polarization-maintaining optical fiber 2 is transmitted through a polarizing lens 6.
The light is focused. Since the light is focused at the refractive index ne (≠no) at that time, it is not focused on the core portion of the polarization-maintaining optical fiber 2 even though the focal lengths are different.

〔Effect of the invention〕

As is clear from the above description, the present invention prevents coupling of light in the opposite direction at the far end, which is extremely effective in reducing noise and stabilizing the operation of the laser diode module.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams explaining one embodiment of the present invention. Figure 1 is a side sectional view, Figure 2 is an enlarged view of the optical system, and Figure 3 illustrates the operating principle of the optical isolator. In the diagram to explain,
In the figure, (a) shows a beam of forward light, (b) shows a beam of backward light that is shifted, and (C) shows a beam of backward light that spreads. In the figure, 1 is a connector, 2 is a polarization maintaining optical fiber, 3 is a magnet, 4 is a polarization separation plate, 5 is a thin film type Faraday rotator, 6 is a polarizing lens, 7 is an output light, 8.9 is a return light,
10 indicates a laser diode, respectively. ) 1 shi direction 1 shi direction 1 mu otoshi inre 7 ri weight l (FτJ! Figure 3 (b) 81 years old poem katsuun p, > 1. /11azu7ua [@3 Figure

Claims (1)

[Claims] A laser diode (10);
In a laser diode module comprising a polarization-maintaining optical fiber (2) for guiding the emitted light from the polarization-maintaining optical fiber (2) to the outside, a polarization splitting plate (4) is provided at the output end of the polarization-maintaining optical fiber (2); A laser diode module equipped with an optical isolator composed of a thin-film Faraday rotator (5) that rotates the plane of polarization of light by 45 degrees using a magnetic field, and a polarizing lens (6).