Optical collimator and method for making same

Details Optical collimator and method for making same Optical collimator and method for making same

2002-03-11

2004-03-30

Palmer, Phan T. H. (Department: 2874)

Optical waveguides

With optical coupler

Input/output coupler

C385S033000, C385S060000, C385S078000

Reexamination Certificate

active

06714703

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to optical collimators and methods for making them, and more particularly to optical collimators assembled by means of gluing and welding.
2. Description of the Prior Art
An optical collimator with a Graded Index (GRIN) lens is used for collimating scattered light emitting from an output end of an optical fiber. The collimated light may then be efficiently and controllably utilized for transmission or testing.
As shown in
FIG. 1
, a conventional optical collimator
100
comprises an optical fiber
110
, a ceramic ferrule
120
, a GRIN lens
130
and an outer glass tube
140
. The ferrule
120
has an inner end
122
, an outer end
124
, and a through hole
126
defined between the inner and outer ends
122
,
124
. A diameter of the through hole
126
is slightly greater than a diameter of the optical fiber
110
. A cone-shaped opening (not labeled) is defined in the outer end
124
, in communication with the through hole
126
. The optical fiber
110
is typically sealed in the through hole
126
with UV-cured epoxy and 353-ND epoxy. To improve optical performance, the inner end
122
of the ferrule
120
and an inner end
112
of the optical fiber
110
are ground and polished to an oblique angle relative to an imaginary line that is perpendicular to respective longitudinal axes of the ferrule
120
and the optical fiber
110
. The angle is typically between 6 and 8 degrees. The GRIN lens
130
has an inner end
132
and an outer end
134
. The inner end
132
of the GRIN lens
130
is adjacent the inner end
122
of the ferrule
120
, and is obliquely ground and polished to be parallel to the inner end
122
. The longitudinal axis of the GRIN lens
130
is aligned with the longitudinal axis of the optical fiber
110
. The ferrule
120
and the GRIN lens
130
are positioned and aligned in the glass tube
140
, so that output light from the GRIN lens
130
can be accurately focused on the inner end
112
of the optical fiber
110
. The ferrule
120
and the GRIN lens
130
are then fixed in place in the glass tube
140
with UV-cured epoxy and 353-ND epoxy.
When the optical fiber
110
is epoxied to the ferrule
120
, and when the GRIN lens
130
and the ferrule
120
are epoxied to the glass tube
140
, excess epoxy may contaminate the inner ends
112
,
132
of the optical fiber
110
and GRIN lens
130
. Such contamination reduces the output of the optical fiber
110
, and diminishes the performance of the GRIN lens
130
. The optical collimator
100
is prone to have large insertion loss. In addition, such contamination is difficult to remove. Furthermore, it is difficult to readjust the relative positions of the optical fiber
110
and the GRIN lens
130
after they have been secured in position. Moreover, typical epoxies need baking to be cured. These epoxies have a coefficient of thermal expansion several times larger than that of the GRIN lens
130
. During baking of the epoxy, the accurate relative positions of the optical fiber
110
and the GRIN lens
130
are frequently altered. Accurate focusing of light from the GRIN lens
130
to the optical fiber
110
is accordingly diminished.
An improved optical collimator is needed to overcome the above-described numerous disadvantages of conventional optical collimators.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an inexpensive optical collimator having low insertion loss.
Another object of the present invention is to provide an optical collimator free from contamination caused by excess glue.
A further object of the present invention is to provide an optical collimator which allows easy and precise adjustment of components thereof.
To solve the problems of the prior art and achieve the objects set out above, an optical collimator of the present invention comprises an optical fiber, a ferrule, a GRIN lens, a metal sleeve and an outer metal tube. The optical fiber has an exposed end which is inserted into the ferrule and glued thereinto. The GRIN lens is glued into the sleeve. Opposite ends of the GRIN lens protrude from opposite ends of the sleeve. The outer tube includes first and second receiving portions. The ferrule is glued into the first receiving portion, and the sleeve is secured in the second receiving portion. A plurality of soldering holes is defined in a periphery of the outer tube. Solder is applied to the sleeve through the holes to firmly connect the outer tube and the sleeve together. After assembly, if a position of the GRIN lens relative to the optical fiber is found to be inaccurate, the sleeve can be easily readjusted and re-soldered.
Other objects, advantages and novel features of the present invention will be apparent from the following detailed description of a preferred embodiment thereof with reference to the attached drawings, in which:


REFERENCES:
patent: 5555330 (1996-09-01), Pan et al.
patent: 5706371 (1998-01-01), Pan
patent: 5734762 (1998-03-01), Ho et al.
patent: 5815614 (1998-09-01), Pan
patent: 6168319 (2001-01-01), Francis
patent: 6343166 (2002-01-01), Hellman et al.
patent: 6353691 (2002-03-01), Li et al.
patent: 6454465 (2002-09-01), Uschitsky et al.
patent: 2002/0186915 (2002-12-01), Yu et al.
patent: 2002/0191881 (2002-12-01), Chen et al.

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