Optical waveguides – With optical coupler – Plural
Reexamination Certificate
2001-04-26
2003-04-29
Ngo, Hung N. (Department: 2874)
Optical waveguides
With optical coupler
Plural
C385S034000
Reexamination Certificate
active
06556743
ABSTRACT:
FIELD OF INVENTION
The present invention relates to an optical signal add/drop apparatus, and more particularly, to an optical signal add/drop apparatus capable of adding and dropping simultaneously optical signals having various wavelength bands.
The optical signal add/drop apparatus is generally used for the optical signal transmission from a major optical transmission line of a bi-directional optical transmission system to a local network or metro core network, or for the optical signal transmission from a metro core network to a access network. That is, by using this optical signal add/drop apparatus, some optical signals having several specific wavelengths, among the optical signals that are transmitted through an optical transmission system from a region A (source) to a region B (destination), can be dropped from a region C and can be used in the network of the region C, and signals having the same wavelength as the dropped signals can be added and can be transmitted to B region.
Particularly, when optical signals having various wavelengths have been inputted into the optical signal add/drop apparatus used in a wavelength division multiplexing optical transmission system, the apparatus can simultaneously add a plurality of desired optical signals thereto and drop the desired optical signals therefrom.
BACKGROUND OF INVENTION
FIG. 1
shows the constitution of a conventional optical signal add/drop apparatus that can simultaneously add and drop a plurality of optical signals.
As shown in
FIG. 1
, the conventional optical signal add/drop apparatus comprises a demultiplexer
10
, a multiplexer
20
and a switch module
30
.
The demultiplexer
10
divides multi-band optical signals &lgr;
1
to &lgr;
n
inputted through optical fibers (input channels) into optical signals having respective wavelength bands, and transmits the divided signals through n optical fibers of output channel. The multiplexer
20
multiplexes optical signals having different wavelength bands inputted through the n optical fibers, respectively; and transmits the multiplexed optical signals to the destination through the other optical fibers (output channels). The demultiplexer
10
and the multiplexer
20
using thin film technology comprise a plurality of optical unit devices (not shown) for combining and separating the optical signals.
The switch module
30
comprises n set of 2×2 switches for connecting respective optical signals received from the demultiplexer
10
with either of the optical fibers connected to the multiplexer
20
or the optical fibers connected to a local network
40
.
In the optical signal add/drop apparatus constructed as such, multiple optical signals &lgr;
1
to &lgr;
n
having n different wavelengths, inputted through the input channels, are separated in view of their wavelengths by the demultiplexer
10
and are transmitted through the respective optical fibers. According to connection state of 2×2 switch, the optical signal may be dropped to the local network
40
or transmitted to the multiplexer
20
. The optical signals may be inputted to the multiplexer
20
, combined with the other signals having different wavelengths, and transmitted to the output channels.
However, since the conventional optical signal add/drop apparatus comprises a plurality of optical unit devices including the multiplexer, the demultiplexer and a group of the 2×2 switches, there was a problem in that the size of the apparatus becomes larger. Further, since the expensive elements such as multiplexer, demultiplexer and the group of the 2×2 switches should be used, there was another problem in that high costs of manufacture thereof are consumed.
Furthermore, since n optical unit devices should be provided, respectively, to the optical fiber grating typed or micro optics typed multiplexer and demultiplexer in case that there are n optical signals having different wavelengths, total 2n optical unit devices are used. Thus, the whole size of the apparatus becomes larger and the production costs thereof are more increased.
SUMMARY OF INVENTION
Accordingly, it is an object of the present invention to provide an optical signal add/drop apparatus that is small in size and is low in production cost.
Further, it is another object of the present invention to provide an optical signal add/drop apparatus wherein a plurality of wavelengths can be simultaneously dropped and added by multiplexing/demultiplexing portion, including a plurality of optical unit devices for simultaneously performing multiplexing and demultiplexing functions.
The optical signal add/drop apparatus for achieving the objects according to the present invention comprises: a first dual-core ferrule having first and second optical fibers disposed to be symmetrical to each other at identical distances from an optical axis for transmitting at least one optical signal; a second dual-core ferrule having third and fourth optical fibers disposed to be symmetrical to each other at identical distances from the optical axis for transmitting at least one optical signal; a wavelength division thin film filter for selectively transmitting only an optical signal having a specific wavelength; a first lens for collimating the optical signal inputted thereto from one of the optical fibers of the first dual-core ferrule into a parallel ray and outputting the parallel ray to the wavelength division thin film filter, and for focusing the optical signal reflected thereto from the wavelength division thin film filter and outputting the optical signal to the other optical fiber of the first dual-core ferrule; and a second lens for focusing the optical signal transmitted thereto from the wavelength division thin film filter and outputting the optical signal to one of the optical fibers of the second dual-core ferrule, and for collimating the optical signal inputted thereto from the other optical fiber of the second dual-core ferrule into a parallel ray, collimating the parallel ray to the wavelength division thin film filter, and outputting optical signal to the second fiber through first lens. Further, the first lens, the wavelength division thin film filter, and the second lens are arranged on the optical axis.
Multiplexing/demultiplexing portion including a plurality of optical unit devices and a switch module including a plurality of 2×2 switches, connected correspondingly to the optical unit devices, respectively, for dropping the optical signal outputted from the optical unit device or adding the optical signal, identical to that dropped from the optical unit device, to the optical unit device.
The optical signal add/drop apparatus according to another aspect of the present invention comprises: an optical signal combining and separating portion including a plurality of optical unit devices which have a first dual-core ferrule having first and second optical fibers disposed to be symmetrical to each other at identical distances from an optical axis for transmitting optical signals, a second dual-core ferrule having third and fourth optical fibers disposed to be symmetrical to each other at identical distances from the optical axis for transmitting optical signals, a wavelength division thin film filter for selectively transmitting only an optical signal having a specific wavelength, a first lens for collimating the optical signal inputted thereto from one of the optical fibers of the first dual-core ferrule into a parallel ray and outputting the parallel ray to a first surface of the wavelength division thin film filter and for focusing the optical signal inputted thereto from the wavelength division thin film filter and outputting the optical signal to the other optical fiber of the first dual-core ferrule, and a second lens for focusing the optical signal inputted thereto from the wavelength division thin film filter and outputting the optical signal to one of the optical fibers of the second dual-core ferrule and for collimating the optical signal inputted thereto from the other optical fiber of the second dual-core ferrule into
Im Young Min
Kim Myoung Jin
Korea Electronics Technology Institute
Ngo Hung N.
Roylance Abrams Berdo & Goodman L.L.P.
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