JP2000081547A - Laser diode module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a laser diode module which is free from the scattered light returning from an optical isolator to a laser diode by using a polarizer of the first optical isolator and a reflection type polarizer for an analyzer. SOLUTION: The reflection type polarizer 17 placed on the optical path of the laser beam transmitted through a first lens 3, a rotator 5 which rotates the polarization direction of the light 45 deg., the reflection type analyzer 19 which is fixed by aligning the transmitted polarized light direction to the rotating direction of the rotator 5 and a magnet 10 constitute the first optical isolator. The absorption type polarizer 7, the rotator 8, the absorption type analyzer 9 and the magnet 10 constitute the second optical isolator. The laser beam scattered by the absorption type polarizer 7 constituting the second optical isolator is largely attenuated by the first optical isolator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a laser diode module mainly used in optical fiber communication.

[0002]

2. Description of the Related Art In a laser diode module, which is a key device of optical fiber communication, when scattered light transmitted through an optical fiber returns to the laser diode, the operation of the laser diode becomes unstable, resulting in an increase in noise and disturbance of a transmitted signal. Cause. Therefore, a laser diode module that requires particularly high-quality signal transmission may need to be provided with a two-stage optical isolator for removing return light. FIG. 2 is a cross-sectional view of a laser diode module equipped with a two-stage optical isolator having the same optical configuration as, for example, the Institute of Electronics, Information and Communication Engineers Autumn National Conference, B-732, 1990. In the figure, 1 is a laser diode, 2 is a case, 3 is a first lens that converts the laser light emitted from the laser diode 1 into parallel light, 4
Is an absorption polarizer placed on the optical path of the laser beam transmitted through the first lens 3, 5 is a rotator for rotating the polarization direction of the light transmitted through the absorption polarizer 4 by 45 degrees, and 6 is a transmitted polarization direction. Is an absorption analyzer fixed in accordance with the rotation direction of the rotator 5; 7 is an absorption polarizer fixed in accordance with the polarization direction of transmitted light in accordance with the polarization direction of laser light transmitted through the absorption analyzer 6;
Is a rotator for rotating the polarization direction of the light transmitted through the absorption polarizer 7 by 45 degrees, 9 is an absorption analyzer fixed so that the transmission polarization direction matches the rotation direction of the rotator 8, and 10 is the rotator 5 And magnets 11 arranged so as to surround the circumference of the magnets 8 and 8 and acting to change the polarization direction of light transmitted by the rotors 5 and 8 by the magneto-optical effect.
, A magnet holder supporting the absorption type polarizer 4, the rotor 5, the absorption type analyzer 6, and the magnet 10, and the absorption type polarizer 7, the rotator 8, the absorption type analyzer 9, and the magnet 10, one by one. Of optical isolators. 1
2 is a second lens for condensing the laser light transmitted through the absorption analyzer 9, 13 is a lens holder for supporting the second lens 12, and 14 is the laser light condensed by the second lens 12. Are the optical fibers arranged so as to be coupled to each other, 15 is a ferrule holding the optical fiber 14, and 16 is a ferrule holder holding the ferrule. In a conventional laser diode module having such a two-stage optical isolator, the laser light emitted from the laser diode 1 can be coupled to the optical fiber 14, and the return light from the optical fiber 14 to the laser diode 1 can be transmitted. It can be greatly attenuated by the two-stage optical isolator.

[0003]

In the above-described laser diode module, since the absorption type polarizer has a property of generating minute scattered light, the scattered light returns to the laser diode, and the operation of the laser diode is stopped. Was unstable.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a laser diode module having stable operation without scattered light returning from an optical isolator to a laser diode.

[0005]

Means for Solving the Problems In the first invention,
The polarizer and analyzer of the first optical isolator of the two-stage optical isolator are of a reflection type.

In the second invention, the polarizer and analyzer of the first optical isolator of the two-stage optical isolator are of a reflection type, and the second optical isolator is composed of a second lens and an optical fiber. There is as a configuration placed between.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 shows a laser diode module according to Embodiment 1 of the present invention. In the figure, reference numerals 1 to 16 are the same as those of the above-described conventional apparatus, and thus the description thereof is omitted. 17 is a reflective polarizer placed on the optical path of the laser beam transmitted through the first lens 3, 18 is a polarizer holder that holds the reflective polarizer 17, and 19 is the transmitted polarization direction of the rotator 5. Reference numeral 20 denotes an analyzer holder that holds the reflection analyzer 19 fixed in accordance with the above. In the laser diode module configured as described above, the laser light scattered by the absorption polarizer forming the second optical isolator is greatly attenuated by the first optical isolator.

Embodiment 2 FIG. 2 shows a second embodiment of the present invention, in which laser light scattered by an absorption polarizer constituting a second optical isolator transmits through a second lens, but is transmitted through a first lens. Greatly attenuated by the optical isolator.

[0009]

According to the invention described above, even if there is scattered light returning from the second optical isolator to the laser diode, the return light is attenuated by the first optical isolator, so that a stable operation of the laser is achieved. A diode module can be obtained.

Further, by arranging the second optical isolator between the second lens and the optical fiber, the size of the second optical isolator can be reduced, and the second optical isolator can be formed by the first optical isolator. Since the scattered light is attenuated, a laser diode module with stable operation can be obtained at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of a laser diode module according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a laser diode module according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a conventional laser diode module.

[Explanation of symbols]

Reference Signs List 1 laser diode, 2 case, 3 first lens, 4 absorption polarizer, 5 rotator, 6 absorption analyzer, 7 absorption polarizer, 8 rotator, 9 absorption analyzer, 10 magnet, 11 magnet Holder, 12
Second lens, 13 lens holder, 14 optical fiber, 15 ferrule, 16 ferrule holder, 17
Reflective polarizer, 18 polarizer holder, 19 reflective analyzer, 20 analyzer holder.

Claims (2)

[Claims] 1. A laser diode, a first lens disposed on an optical path of laser light emitted from the laser diode so as to make the laser light parallel, and light of the laser light transmitted through the first lens. A first optical isolator composed of a polarizer, a rotator, and an analyzer placed on an axis; and a polarizer, a rotator, and an analyzer placed on the optical axis of laser light transmitted through the first optical isolator. A second optical isolator composed of photons, a second lens for condensing the laser light transmitted through the second optical isolator, and an optical fiber for coupling the laser light condensed by the second lens A laser diode module comprising: a reflection type polarizer used as a polarizer and an analyzer of the first optical isolator. 2. A laser diode, a first lens placed on an optical path of laser light emitted from the laser diode so as to make the laser light parallel, and a light of the laser light transmitted through the first lens. A first optical isolator composed of a polarizer, a rotator, and an analyzer placed on an axis, a second lens for condensing laser light transmitted through the first optical isolator, and a second lens The second is composed of a polarizer, a rotator, and an analyzer placed on the optical axis of the transmitted laser light.
In the laser diode module including the optical isolator of (1) and an optical fiber for coupling the laser light transmitted through the second optical isolator, a reflective polarizer is used as a polarizer and an analyzer of the first optical isolator. A laser diode module characterized by the above-mentioned.