JPH04291211A - Constant polarization laser diode module - Google Patents

Abstract

PURPOSE:To facilitate the adjustment of an optical axis and a polarization plane in the case of assembly, to improve the rate of quenching and to improve manufacture yield by fixing a polarizer to the end part of a polarization holding optical fiber. CONSTITUTION:A polarizer 7a is fitted to the end face of a ferrule 8 inserted the end part of a polarization holding optical fiber 9. At such a time, the polarizer 7a is joined to the ferrule 8 so that the polarization plane of the optical fiber 9 can be matched to the polarization plane of the polarizer 7a. On the other hand, a lens system composed of a lens 6 or the like is fixed while matching the optical axis of a laser diode with that of the lens system. Then, the ferrule 8 is fixed while matching the optical axis of the optical fiber 8 to those of this laser diode and the lens system and matching the polarization plane of the laser diode to that of the optical fiber 9.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a fixed polarization laser diode module that uses an optical fiber to transmit light output from a laser diode while maintaining its polarization plane, and relates to LN (LiNbO3) optical switches, coherent optical communications, etc. , relates to a constant polarization laser diode module used in optical fiber sensors such as optical fiber gyros and magnetic field sensors.

0002

2. Description of the Related Art FIG. 4 is a schematic sectional view showing a conventional polarized laser diode module, and FIG. 5 is a partially enlarged view showing the vicinity of the ferrule 8.

A laser diode 1 is disposed on the support member 3, and a predetermined voltage is applied to the laser diode 1 via an electrode 4. Above the laser diode 1 are a ball lens 2 and a lens 5.
A lens system 10 consisting of 6 lenses is provided. Further, a polarizer 7 is arranged on the lens 6. A ferrule 8 and a polarization-maintaining optical fiber 9 fixed to the ferrule 8 are arranged above the polarizer 7 and at a slight distance from the polarizer 7.

These laser diode 1, lens system 10, etc. are provided in cases 11, 12, 13,
The optical fiber 9 is led out from this case 13.

Although the oscillation light output from the laser diode 1 is polarized, the intensity of the polarized light is relatively low at about 20 dB. This laser diode 1 has lenses 2, 5, 6
It is not possible to obtain an extinction ratio higher than the polarized light intensity described above simply by incorporating the lens system 10 consisting of the above and optically coupling it with the polarization-maintaining optical fiber 9. Therefore, as described above, the polarizer 7 is disposed between the lens system 10 and the optical fiber 9. Thereby, the extinction ratio of the laser diode module can be improved.

Note that the lens system 10 is fixed to lens supporting members such as cases 11, 12, 13, etc. by laser welding, solder, or adhesive.

[0007]

However, the conventional polarization constant laser diode module described above has a problem in that optical axis adjustment and polarization plane adjustment during assembly are complicated. In other words, in the conventional polarized laser diode module, the laser diode 1
, the lens system 10, the polarizer 7, and the optical fiber 9 must be aligned, and the laser diode 1,
It is necessary to match each plane of polarization of the polarizer 7 and the optical fiber 9.

Furthermore, after completing these adjustments, for example, when fixing the lens system 10, the optical axis and plane of polarization may shift. If the optical axis or polarization plane shifts, the extinction ratio after assembly will be significantly worse than at the adjustment stage.

The present invention has been made in view of the above problems, and provides a constant polarization laser diode module that allows easy optical axis adjustment and polarization plane adjustment and avoids deterioration of extinction ratio during assembly. The purpose is to

0010

[Means for Solving the Problems] A constant polarization laser diode module according to the present invention includes a laser diode, a polarization-maintaining optical fiber into which light output from the laser diode enters, and a polarization-maintaining optical fiber in which the laser diode is connected to the polarization-maintaining optical fiber. It is characterized by comprising a polarizer fixed to the end on the diode side, and a lens that guides the light output from the laser diode to the end of the polarization-maintaining optical fiber via the polarizer.

[0011]

[Operation] In the present invention, a polarizer is fixed to the end of a polarization-maintaining optical fiber. Therefore, by fixing the polarizer to the end of the optical fiber in advance with the polarization planes of the polarizer and the optical fiber aligned, it becomes easier to adjust the optical axis and the polarization plane during assembly. That is, the optical axis adjustment when assembling the laser diode module according to the present invention only requires aligning the optical axes of the laser diode, lens system, and optical fiber, and the optical axis of the polarizer can be adjusted by aligning the optical axes of the optical fibers. Consistent with In addition, if the polarization plane of the polarizer and the optical fiber are precisely matched in advance, adjusting the polarization plane between the laser diode and the polarizer (or optical fiber) will result in a large loss of light (fiber end output). A rough adjustment (several degrees) is sufficient.

Furthermore, in the present invention, by fixing the polarizer to the end of the optical fiber in a state where the plane of polarization of the polarizer and the plane of polarization of the optical fiber are matched, deviations in the plane of polarization when the lens system is fixed can be avoided. can be avoided.

[0013] The polarizer is fixed to the end of the optical fiber, for example, by bonding it to the end face of a ferrule into which the end of the optical fiber is inserted.

[0014]

Embodiments Next, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic cross-sectional view showing a constant polarization laser diode module according to an embodiment of the present invention.

This embodiment is different from the conventional one in that a polarizer 7a is attached to the end face of the ferrule 8 into which the end of the optical fiber 9 is inserted.
Since the other components are basically the same as the conventional one, the same parts in FIG. 1 as in FIG. 5 are given the same reference numerals, and detailed explanation thereof will be omitted.

In this embodiment, the end of the polarization-maintaining optical fiber 9 is fixed to the ferrule 8, and the polarizer 7
a is joined to the lower end surface of this ferrule 8. Therefore, the polarizer 7a and the lens 6 are slightly separated from each other. Note that the polarizer 7a may be fixed together with the ferrule 8 and lens 6.

The constant polarization laser diode module according to this embodiment can be manufactured as follows. First, the polarizer 7a is attached to the end face of the ferrule 8 into which the end of the polarization-maintaining optical fiber 9 is inserted. At this time,
The polarizer 7a is joined to the ferrule 8 so that the polarization plane of the optical fiber 9 and the polarization plane of the polarizer 7a match.

On the other hand, the optical axes of the laser diode 1 and a lens system including the lens 6 and the like are aligned, and the lens system is fixed. Then, the optical axis of the optical fiber 9 is aligned with the optical axis of the laser diode 1 and the lens system, and the polarization plane of the laser diode 1 and the polarization plane of the optical fiber 9 are aligned, and the ferrule 8 is fixed. As a result, the laser diode module according to this example is completed.

FIG. 2 shows the polarization controlled laser diode module according to the embodiment, with the horizontal axis representing the angle (θ) between the polarization plane of the polarizer and the optical fiber, and the vertical axis representing the extinction ratio. FIG. 2 is a graph diagram showing extinction ratio characteristics of a conventional polarized laser diode module (Comparative Example 1) and a polarized laser diode module without a polarizer (Comparative Example 2). As is clear from FIG. 2, the extinction ratio of the laser diode module according to this embodiment is slightly improved compared to the conventional one.

FIG. 3 is a graph showing the results of examining the extinction ratio after each assembly process in the polarized laser diode module according to this embodiment and the conventional polarized laser diode module (Comparative Example 1). It is a diagram. As is clear from FIG. 3, in the conventional laser diode module, the extinction ratio tends to decrease as the assembly process progresses, whereas in this embodiment, the extinction ratio can easily be prevented from decreasing.

As described above, in this embodiment, since the polarizer 7a is fixed to the optical fiber 9, optical axis adjustment and polarization plane adjustment are facilitated, and manufacturing yield is improved.

[0023]

Effects of the Invention As explained above, in the constant polarization laser diode module according to the present invention, since the polarizer is fixed to the end of the polarization-maintaining optical fiber, the optical axis adjustment and polarization plane adjustment during assembly are easy. This method is easy, and it is possible to obtain the effect that the extinction ratio is improved compared to the conventional method. Moreover, manufacturing yield is also improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing a polarization-controlled laser diode module according to an embodiment of the present invention.

FIG. 2 is a graph showing a change in extinction ratio depending on the plane of polarization angle of a polarizer and an optical fiber in an example of the present invention and a comparative example.

FIG. 3 is a graph showing extinction ratios after each assembly process in Examples and Comparative Examples of the present invention.

FIG. 4 is a schematic cross-sectional view showing a conventional polarization controlled laser diode module.

FIG. 5 is a partially enlarged view showing the vicinity of a ferrule of a conventional polarized laser diode module.

[Explanation of symbols]

1; Laser diode 2, 5, 6; lens 7; Polarizer 8; Ferrule 9; Optical fiber 10; Lens system

Claims (1)

[Claims] 1. A laser diode, a polarization-maintaining optical fiber into which light output from the laser diode enters, a polarizer fixed to an end of the polarization-maintaining optical fiber on the laser diode side, and the laser diode. a lens for guiding light output from the polarization-maintaining optical fiber to an end of the polarization-maintaining optical fiber via the polarizer.