Optical: systems and elements – Collimating of light beam
Reexamination Certificate
2001-12-21
2004-03-09
Sugarman, Scott J. (Department: 2873)
Optical: systems and elements
Collimating of light beam
C385S093000
Reexamination Certificate
active
06704146
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to optical collimating devices and methods for making them, and more particularly to collimating devices that use epoxy and a tube to join components thereof.
2. Description of the Prior Art
Demand for higher transmission capacity and speed in optical communications systems is unrelenting. Optical transmission technology is constantly developing to satisfy such demand. Dense Wavelength Division Multiplexing (DWDM) technology has been an important development, and is now in widespread use in optical communications systems throughout the world. A DWDM system multiplexes a plurality of signals of different wavelengths into a single optical fiber at an initiating end of the optical fiber. The multiplexed signals are then demultiplexed into a plurality of signals at a terminal end of the optical fiber. Each demultiplexed signal is then output to an end recipient. DWDM systems can increase optical transmission capacity by up to ten times or even more.
A collimating device incorporating a filter is a basic wave division device deployed in many optical modules used in DWDM systems, such as Optical Add-Drop Multiplexers (OADMs) and Dense Wavelength Division Multiplexers (DWDMs).
FIG. 1
shows a conventional collimating device
10
comprising a Graded Index (GRIN) lens
12
and a filter
14
. Typically, the filter
14
is adhered on an end face (not labeled) of the GRIN lens
12
using two types of epoxy. One type is UV Epoxy
16
, and the other type is 353 NDT Epoxy
18
. UV Epoxy
16
has less fluidity and viscosity than 353 NDT Epoxy
18
. In assembly, UV Epoxy
16
is first applied at an interface (not labeled) between the GRIN lens
12
and the filter
14
. A UV gun temporarily cures the UV Epoxy
16
. This process sometimes results in contamination of the corresponding end faces of the GRIN lens
12
and the filter
14
. Such contamination reduces optical performance of the collimating device
10
. Then the 353 NDT Epoxy
18
is applied around an outer surface of the UV Epoxy
16
. A relatively large amount of 353 NTD Epoxy
18
is required to cover the entire expanse of the interface. The collimating device
10
is baked to permanently cure the 353 NTD Epoxy
18
and the UV Epoxy
16
. The GRIN lens
12
and filter
14
are thus fastened to each other.
Coefficients of thermal expansion of UV Epoxy
16
and 353 NTD Epoxy
18
are respectively 4.3×10
−5
/° C. and 4.7×10
−5
/° C., both of which are several times greater than coefficients of thermal expansion of the GRIN lens
12
and the filter
14
. Therefore, baking can result in asymmetric thermal stress. As a result, optical characteristics of the collimating device
10
may vary according to the prevailing operating temperature of the collimating device
10
at any given time. Unstable operation of the collimating device
10
adversely affects signal transmission. Moreover, the procedure for obtaining precise alignment and positioning of the filter
14
relative to the GRIN lens
12
is complicated. This increases production costs.
An improved collimator device is needed to overcome the many disadvantages of conventional collimating devices.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an inexpensive collimating device having low insertion loss.
Another object of the present invention is to provide a collimating device free from contamination caused by excess glue.
A further object of the present invention is to provide a collimating device which allows easy and precise adjustment of components thereof.
To achieve the objects set out above, a collimating device of the present invention comprises a GRIN lens, a filter and an outer tube. The GRIN lens and the filter are both secured in the outer tube. The outer tube is made of stainless steel, and has a first receiving portion and a second receiving portion. The first receiving portion is cylindrical, and defines a cylindrical cavity therein for receiving the GRIN lens. The second receiving portion is also cylindrical, and defines a generally rectangular cavity therein for receiving the filter. The GRIN lens and the filter are glued in the outer tube with relatively little epoxy, and with no excess epoxy contaminating optical faces thereof.
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: 5845023 (1998-12-01), Lee
patent: 6347170 (2002-02-01), Zheng
patent: 6382841 (2002-05-01), Ryall
Chen Chih-Yi
Wu Kun-Tsan
Chung Wei Te
Collins Darryl J.
Hon Hai - Precision Ind. Co., Ltd.
Sugarman Scott J.
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