Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
1999-03-01
2001-06-12
Spyrou, Cassandra (Department: 2872)
Optical waveguides
With optical coupler
Input/output coupler
C385S033000
Reexamination Certificate
active
06246813
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to a method and system for use in optical fiber technology. More particularly, this invention relates to a method and system for manufacturing an improved dual fiber optical collimator.
BACKGROUND OF THE INVENTION
As optical fiber technology is being more broadly applied in the telecommunications, data communications and CATV industries, the fiber optic component industry is now confronted with increasing requirements for good performance and high reliability of fiber optic components. In particular, the optical components are required to maintain substantially constant performance characteristics and reliability under wide ranges of temperature variations. High humidity resistance is also required. Currently, most of in-line fiber optic components are designed and manufactured based on optical collimators which provide low-loss light transmission from the input fiber to the output fiber through an optical element. As a basic building block of the fiber optic components, the reliability and level of performance of the fiber optic components depend heavily on the reliability and the performance characteristics of the optical collimators. Dual fiber optical collimators are one type of collimators widely employed in making the fiber optic components. For example, the dual fiber optical collimators are employed to make thin film filter based wavelength division multiplexers and hybrid optical isolators.
FIG. 1A
shows the structure of a typical dual fiber optical collimator that includes a dual fiber pigtail
30
, a GRIN lens
15
, a glass tube
40
and a stainless steel holder
50
. In a typical manufacturing process, the relative position of the GRIN lens
15
to the fiber pigtail
30
is adjusted to achieve a lowest transmission loss from the input fiber
20
to output fiber
25
. The GRIN lens
15
and the dual fiber pigtail
30
are fixed together by applying an ultraviolet (UV) curing epoxy
35
. Then the fiber pigtail
30
is fixed to a glass tube
40
by applying an UV curing epoxy
45
and the glass tube
40
is fixed to a stainless steel holder
50
by a heat curing epoxy
55
. The typical method and system provides the dual fiber optical collimators with fair performance and reliability suitable for some types of applications. However, the dual fiber optical collimators manufactured with the conventional processes often fail and perform poorly when they are implemented in fiber optic components that demand long term operation in a high temperature, e.g., 85° C., and high humidity, e.g., 85% humidity, environment. The UV curing epoxy bonding, e.g., epoxy
35
, is often broken when subject to such operation conditions and then optical signal transmission becomes very poor. Thus, further development and reliable fiber optic components with high level of performance is limited to these difficulties. In a pending patent, entitled
Dual Fiber Optical Collimator
, filed recently by the present inventor, improvements are achieved for the reliability of the dual fiber optical collimators. In the improved manufacturing process as shown by
FIG. 1B
, for the pending application, the GRIN lens
15
and the dual fiber pigtail
30
are first sealed by applying tiny amount of an ultraviolet (UV) curing epoxy
35
. After the relative position of the GRIN lens
15
to the fiber pigtail
30
is adjusted to achieve a lowest transmission loss from the input fiber
20
to output fiber
25
, the GRIN lens
15
and the fiber pigtail
30
are fixed together by applying a heat curing epoxy
40
. Since heat-curing epoxy bonding is much stronger than UV curing epoxy bonding, the improved dual fiber optical collimators have much better reliability as compared to the typical ones. However, due to the use of sealing UV curing epoxy, the dual fiber optical collimators, even with improved reliability, still cannot fully meet the more stringent application requirements. The small quantity UV epoxy often causes reliability problems due to an observed characteristic that the performance of UV curing epoxy demonstrates too much temperature dependence. Further reliability concerns are caused by the fact that the UV curing epoxy has low humidity resistance. Thus, the improved dual fiber optical collimators can only prove a partial solution.
Therefore, a need still exists in the art of design and manufacturing of the dual fiber optical collimators to provide new material compositions, device structure, and manufacturing processes to overcome the difficulties discussed above. Specifically, a technique to provide the collimators without use of any UV curing epoxy is required. Since production costs have been an important factor prohibiting practical implementation of fiber optical technology, it is also highly desirable that the cost of such technology would be as low as possible.
SUMMARY OF THE PRESENT INVENTION
It is therefore an object of the present invention to provide a new design and process for fabricating a dual fiber optical collimator with improved temperature dependence and humidity resistance. Therefore, the aforementioned difficulties and limitations in the prior arts can be overcome.
Specifically, it is an object of the present invention to provide a design and process to fix a dual fiber pigtail to a GRIN lens by applying only the heat curing epoxy. Two short glass tubes are used to prevent the heat curing epoxy from contaminating the central optical path. As a result, the need for using UV curing epoxy is eliminated according to the new method and configuration of the dual fiber optical collimators of this invention. The collimators produced according to the presently improved design and process have significantly minimized the temperature dependence of collimator performance and increased the humidity resistance. Therefore, the collimators of this invention can be employed in fiber optic components for broaden applications without being limited by the performance and reliability problems of the collimators as that encountered in the prior arts.
Briefly, in a preferred embodiment, the present invention discloses a dual fiber optical collimator. The collimator includes a dual fiber pigtail disposed at a gap distance from a GRIN lens with the gap distance adjusted for achieving a lowest transmission loss. The collimator further includes two short glass tubes. The fiber pigtail is inserted into and held by the first glass tube and the GRIN lens is inserted into and held by the second glass tube. The fiber pigtail, the GRIN lens and the short glass tubes are fixed together by a first heat curing epoxy. The collimator further includes a long glass tube containing and fixing the fiber pigtail in the long glass tube with a second heat curing epoxy. The collimator further includes a stainless steel holder containing and permanently fixing the long glass tube by a third heat curing epoxy. In a preferred embodiment, the short glass tubes have a length of about 2 mm, an outer diameter of about 2.8 mm, and an inside diameter as the same as those of the fiber pigtail and the GRIN lens. In another preferred embodiment, the first heat curing epoxy for fixing the fiber pigtail, the GRIN lens and the short glass tubes is the 353ND epoxy. In another preferred embodiment, the GRIN lens is a GRIN lens of 0.23 pitch.
The present invention further discloses a method to fabricate an improved dual fiber optical collimator. The method includes the steps of: a) Inserting a GRIN lens into a short glass tube and a dual fiber pigtail into another short glass tube; b) adjusting the position of the GRIN lens relative to the dual fiber pigtail on an alignment stage to achieve a lowest transmission loss; c) adjusting the positions of the two short glass tubes so that their end surfaces are in contact with each other; d) fixing the fiber pigtail, the GRIN lens and the two short glass tubes together by applying a heat curing epoxy; e) permanently fixing the fiber pigtail to a long glass tube by applying a heat curing epoxy; f) permanently fixing the long glass tube to a
Boutsikaris Leo
JDS Uniphase Corporation
Lin Bo-In
Spyrou Cassandra
LandOfFree
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