Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
2001-10-30
2004-03-02
Sanghavi, Hemang (Department: 2874)
Optical waveguides
With optical coupler
Input/output coupler
C385S033000, C385S024000, C385S047000
Reexamination Certificate
active
06701040
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to optical systems, and more particularly to a method and system for providing a dense wavelength division multiplexer.
BACKGROUND OF THE INVENTION
To meet the increasing demand for information transmission capacity, multiple wavelength transmission is required. Dense wavelength division multiplexers (DWDMs) are used in optical systems for functions of combining or separating optical signals with densely packed wavelengths. A thin file filter (TFF) and a micro-optics based DWDM can fulfill such a requirement and usually provide good optical performance and environmental stability.
FIG. 1
depicts a conventional DWDM
10
. The conventional DWDM
10
includes a filter
12
having a filter coating surface
14
, a graduated index (GRIN) lens
16
, a glass tube
18
holding a dual fiber capillary
20
with fibers
24
and
26
and a surrounding metal tube
22
. The conventional DWDM
10
also includes a single fiber collimator
30
with a fiber
31
. The fiber
24
provides an input optical signal, which is collimated by the GRIN lens
16
and provided to the filter
12
, which transmits the optical signal with desired wavelength and reflects the remainder of the optical signal containing all other wavelengths. The single fiber collimator
30
receives the transmitted, filtered optical signal and couples this optical signal into fiber
31
. The reflected optical signal is focused by GRIN lens
16
and coupled back to fiber
26
. Thus, the conventional DWDM
10
can be used to separate out a portion, such as one or several wavelengths, of the optical signal input to the conventional DWDM
10
.
Although the conventional DWDM
10
functions, one of ordinary skill in the art will readily recognize that the conventional DWDM has several drawbacks. First, the filter
12
is attached to the GRIN lens
16
at the filter coating surface
14
. Typically, the filter
12
is attached to the GRIN lens
16
using UV epoxy
15
to form a filter/GRIN assembly, which is further attached with dual fiber capillary
20
using UV epoxy
17
. Because the filter
12
is attached to the GRIN lens
16
at the filter coating surface, mechanical stress can be introduced into the coating by the epoxy curing process. As a result, the properties of the filter, such as the center wavelength, the bandwidth and the band shape are changed. Thus, these properties of the conventional DWDM
10
can be altered. This makes the conventional DWDM of less use in applications where the channel spacing is very narrow, such as 50 or 25 GHz. The conventional DWDM
10
is, therefore, not suitable for use with such densely packed optical signals.
In addition to being unable to be used for dense optical signals, the conventional DWDM
10
may also be unreliable in higher temperature and/or higher humidity environments. As discussed above, the filter
12
is affixed to the GRIN lens
16
using an UV epoxy
15
. The assembly made from the GRIN lens
16
/filter
12
and dual fiber capillary
20
are also affixed using UV epoxy
17
. Such an epoxy is prone to softening in high temperature and/or high humidity environments. When the UV epoxy
15
and
17
softens, the dual fiber capillary
20
, the GRIN lens
16
and filter
12
may move with respect to each other. As a result, the optical alignment critical to the functioning of the conventional DWDM
10
is compromised. Thus, the conventional DWDM
10
becomes unreliable in such environments.
Accordingly, what is needed is a system and method for providing a DWDM that is more reliable and suitable for dense optical signals. The present invention addresses such a need.
SUMMARY OF THE INVENTION
The present invention provides a method and system for providing a dense wavelength division multiplexer. The method and system include providing a dual fiber collimator, a filter and a filter holder. The dual fiber collimator includes a lens and a capillary. The capillary is for holding a plurality of fibers. The filter holder has an aperture therein. The filter is disposed between the dual fiber collimator and the filter holder. The filter has a first surface and a second surface opposite to the first surface. The first surface is covered with a filter coating. The filter is affixed to the filter holder by the second surface.
According to the system and method disclosed herein, the present invention provides a dens wavelength division multiplexer suitable for use with optical signals with densely packed wavelengths.
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patent: 5905827 (1999-05-01), Naganuma et al.
patent: 5917626 (1999-06-01), Lee
patent: 6185347 (2001-02-01), Zheng
patent: 6198858 (2001-03-01), Pan et al.
patent: 6246813 (2001-06-01), Zheng
patent: 6343166 (2002-01-01), Hellman et al.
patent: 6469847 (2002-10-01), Fan et al.
patent: 2002/0071630 (2002-06-01), Su et al.
patent: 2002072009 (2002-03-01), None
patent: WO 02/42816 (2002-05-01), None
Li Yiqiang
Wang Yongjian
AC Photonics, Inc.
Knauss Scott A
Sanghavi Hemang
Sawyer Law Group LLP
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