JP2744533B2 - Optical coupler using polarization-maintaining optical fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical coupler using a polarization maintaining optical fiber.

[0002]

2. Description of the Related Art Semiconductor laser couplers used for optical communication include a type using a single mode fiber and a semiconductor laser (referred to as an LD), and a type using a polarization maintaining fiber and an LD. The latter two are used in coherent optical communication, light sources for exciting fiber optic amplifiers, light sources for measuring instruments, etc., and efficiently use the polarization extinction ratio (TE / TM ratio) characteristics of LDs with polarization maintaining fibers. They must be coupled and propagated.

A conventional example of an LD coupler using a polarization maintaining optical fiber will be described with reference to FIG.

1 is an LD, 2 is an LD header on which the LD 1 is mounted, 3 is a ball lens for converting light from the LD 1 into a parallel beam, 4 is a cap with a window for hermetically sealing the LD 1, 5 is a parallel lens A rod lens for efficiently coupling the beam to the polarization maintaining optical fiber, 6 a ferrule for bonding and holding the polarization maintaining optical fiber, 7 a polarization maintaining optical fiber, 8 a rod lens 5 and a ferrule 6
And a lens holder 9 for integrating the virtual fibers on the cap 3 after optical adjustment on the cap 3.

For fixing, the virtual fiber is rotated about the optical axis so that the LD-TE mode coincides with the slow axis 10 of the polarization maintaining optical fiber with respect to the parallel beam from the LD 1 as shown in FIG. After optical adjustment to maximize the fiber output, points A and B in FIG. 2 are welded by a YAG laser.

[0006]

However, in the optical coupler described above, the sleeve 9 after the optical adjustment shown in FIG.
As a result, distortion occurs in the rod lens 5 and the polarization maintaining optical fiber 7 due to residual stress caused by melting and solidification at the time of welding of the lens holder 8 and, as shown in FIG. In the case where the loss of the holding optical fiber 7 is incident or the polarization extinction ratio of the fiber output light is deteriorated, the polarization plane is rotated in the rod lens 5 as shown in FIG. As shown in FIG. 4 (c), the polarization maintaining optical fiber 7 is
There is a problem that the polarization extinction ratio may deteriorate after the incidence.

[0007] The present invention prevents the polarization extinction ratio from deteriorating due to the residual stress caused by the above-mentioned welding being applied to the rod lens and the polarization maintaining optical fiber, and provides a polarization maintaining light having good polarization extinction ratio characteristics. It is an object of the present invention to provide an optical coupler using a fiber.

[0008]

According to the present invention, there is provided an LD package having a semiconductor laser mounted thereon.
In the optical coupler virtual fiber bonding the ferrule for holding the lens holder and the polarization maintaining optical fiber for holding the rod lens fixed to a portion of the sleeve for coupling said semiconductor laser and polarization maintaining optical fiber, the Ba
The outer diameter of the lens holder of
Smaller than the diameter, the outer diameter of the ferrule fits into the sleeve
To be substantially the same as the inner diameter of the sleeve,
A part of the ferrule having an outer sheath for the polarization maintaining optical fiber
The part to be held in minutes and the part of the sleeve by welding
It was fixed .

[0009]

The optical coupler according to the present invention has a structure in which residual stress caused by melting and solidification generated when one end of the sleeve is welded to the rear part of the ferrule is hardly applied to the rod lens and the polarization maintaining optical fiber. The polarization extinction ratio does not deteriorate due to the residual stress.

[0010]

FIG. 1 is a sectional view showing an embodiment of the present invention.

In FIG. 1, 1 is an LD, 2 is an LD header on which the LD 1 is mounted, 3 is a ball lens for converting light from the LD 1 into a parallel beam, and 4 is a cap with a window for hermetically sealing the LD 1. Reference numeral 5 denotes a rod lens for efficiently coupling the parallel beam to the polarization maintaining optical fiber, 6 denotes a ferrule for bonding and holding the polarization maintaining optical fiber, and 7 denotes a polarization holding part of which is covered with an outer cover and partially exposed. Light
Fiber 8 is a lens holder for integrating rod lens 5 and ferrule 6 via solder or adhesive (this integrated product is referred to as a virtual fiber), and 9 is a virtual fiber integrated on cap 3 after optical adjustment. It is a sleeve for.

The outer diameter of the lens holder 8 is set slightly smaller than the inner diameter of the sleeve 9 so that a predetermined gap exists between the lens holder 8 and the sleeve 9. The ferrule 6 is made of a weldable metal (for example, SUS).
304), the outer diameter of which is substantially the same as the inner diameter of the sleeve 9 so that the ferrule 6 can be fitted into the sleeve 9. On the other hand, the length of the sleeve 9 is set so that when the ferrule 6 is fitted, the distal end is located at a position slightly away from the joint between the lens holder 8 and the ferrule 6, that is, at the rear of the ferrule 6. I have.

For fixing, the virtual fiber is rotated around the optical axis so that the LD-TE mode coincides with the slow axis 10 of the polarization maintaining optical fiber with respect to the parallel beam from the LD 1 as shown in FIG. After optical adjustment to maximize the fiber output, points A and B in FIG. 1 are welded by a YAG laser.

As described above in detail, according to the present invention, the virtual fiber and the sleeve are fixed by welding from the lens holder shown in FIG. 2 to the wave holding of the ferrule shown in FIG.
Since the structure is such that the optical fiber is held by the part having the outer sheath, the effect of welding to the rod lens and the polarization maintaining optical fiber is eliminated, and the difference in polarization extinction ratio characteristics between the optical adjustment and after welding is fixed. Is gone.

Further, it goes without saying that the present invention is effective not only when the ferrule holding the polarization-maintaining optical fiber and the sleeve are fixed by welding, as well as the virtual fiber.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing a conventional LD coupler.

FIG. 3 is an explanatory diagram of a virtual fiber adjustment method.

FIG. 4 is an explanatory diagram of polarization extinction ratio deterioration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 LD 2 LD header 3 Ball lens 4 Cap 5 Rod lens 6 Ferrule 7 Polarization holding fiber 8 Lens holder 9 Sleeve

Claims (1)

(57) [Claims] 1. A semiconductor laser and LD packages equipped with the lens holder and the ferrule and secured to the semiconductors laser virtual fiber in a part of the sleeve formed by joining to retain the polarization maintaining optical fiber for holding the lens In the optical coupler for coupling the optical fiber and the polarization maintaining optical fiber, the outer diameter of the lens holder of the virtual fiber is three.
The inner diameter of the ferrule is smaller than the inner diameter of the
Is approximately the same as the inside diameter of the sleeve so that it can fit
The ferrule has an outer sheath with the polarization maintaining optical fiber.
The part held by the part to be welded and the part of the sleeve are welded.
Uses a polarization-maintaining optical fiber that is more secure
Optical coupler.