Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
1999-03-08
2001-01-16
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
With optical coupler
Input/output coupler
C385S013000, C385S147000
Reexamination Certificate
active
06175674
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to an adjus compensation device for fiber Bragg gratings.
2. Description of the Related Art
Fiber Bragg gratings (FBGs) are very important elements widely used in the fabrication of various functional devices for dense WDM networks, for example FBG stabilized laser sources and various FBG-based WDM devices for multiplexers, demultiplexers and add/drop filters. In the practical application of FBGs, however, a problem arising from changes in the surrounding temperature has been noticed. Because the pitch of the FBGs determines the central frequency of the reflected optical signal transmitted in an optical fiber, the FBGs are carefully designed and accurately manufactured. The problem is that the optical fibers elongate in a raised surrounding temperature so that the pitches of the FBGs deviate from the design value. Such a situation is not desirable.
FIG. 1A
shows a temperature compensation device for fiber Bragg gratings using a bi-metal structure which includes two arms
13
,
13
′ and two metal plates
14
,
15
. The two metal plates
14
,
15
are welded together while the two arms
13
,
13
′ are welded at the sides of the metal plates
14
,
15
. The thermal expansion coefficient of the metal plate
14
is smaller than that of the metal plate
15
.
In operation, an optical fiber
11
provided with FBGs
12
are glued onto the arms
13
,
13
′. The optical fiber
11
tends to elongate in a raised surrounding temperature. However, the temperature compensation device bends, as shown in
FIG. 1B
, due to different thermal expansion coefficients between the two metal plates
14
,
15
, so as to prevent the optical fiber
11
from elongating. By this arrangement, the change in the pitches of the FBGs
12
arising from the raised temperature can be greatly reduced.
The above-mentioned temperature compensation device for fiber Bragg gratings does lessen the influence of temperature change on the FBGs. However, the compensation in such a way is not very accurate because of the tolerances arising from manufacturing and packaging (In operations, the temperature compensation device is packaged by a box with the ends of the optical fiber fixed to the box. This can prevent an external force, such as a careless pull at the optical fiber, from destroying the temperature compensation device). For example, the tolerances may arise from over-stretching the optical fiber when: (1) gluing the optical fiber onto the bi-metal structure; (2) attaching the ends of the optical fiber to the box for packaging. It is understood that tolerances are not considered in design. However, tolerances do influence the control over the changes of the length of the optical fiber so that the compensation of the change of pitches of the FBGs is not accurate.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an adjustable compensation device for fiber Bragg gratings that solves the above-mentioned problem.
In accordance with the object of the present invention, an adjustable compensation device for fiber Bragg gratings is provided. The device includes a bimetal structure and a fixture. An optical fiber provided with fiber Bragg gratings is connected to the bimetal structure. The fixture firmly holds the bimetal structure so that the bimetal structure behaves like cantilever beams to compensate pitches of the fiber Bragg gratings. Furthermore, a shim can be inserted between the bimetal structure and the fixture so as to incline the bimetal structure. The compensation for the change of the length of the optical fiber can be adjusted by changing the fixture and/or shim.
REFERENCES:
patent: 5841920 (1998-11-01), Lemaire et al.
patent: 6044189 (2000-03-01), Miller
Bednarek Michael D.
Palmer Phan T. H.
Pittman Shaw
Uconn Technology Inc.
LandOfFree
Adjustable compensation device for fiber bragg gratings does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Adjustable compensation device for fiber bragg gratings, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Adjustable compensation device for fiber bragg gratings will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2508390