Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
1998-06-17
2001-08-07
Spyrou, Cassandra (Department: 2872)
Optical waveguides
With optical coupler
Particular coupling structure
C385S024000, C385S037000, C359S199200, C359S199200, C359S199200
Reexamination Certificate
active
06272270
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical wave combining/splitting device that has a function to separate or demultiplex a wavelength-multiplexed optical signal into multiple optical signals in a specified selective wavelength band, and a function to combine or multiplex optical signals having various wavelengths.
2. Description of the Related Art
An example of a conventional optical wave combining/splitting device (that is, optical multiplexer/demultiplexer) is one disclosed in a document I (LEOS '95 Collection PD1.3). FIG.
6
(A) shows the general configuration of the optical wave combining/splitting device disclosed in the document I. The conventional optical wave combining/splitting device comprises the first input/output port
11
, a distributor
13
for distributing optical signal from the port
11
, an arrayed waveguide diffraction grating wavelength splitter
15
connected to the distributor
13
, and the second input/output port
17
comprised of multiple ports that is connected to the diffraction grating wavelength splitter
15
. The diffraction grating wavelength splitter
15
further comprises the first star coupler
15
a
, the first arrayed waveguide
15
b
comprised of multiple waveguides having different optical path lengths, and the second star coupler
15
c
, which are sequentially positioned from the distributor
13
side. The distributor
13
can be implemented by a Y branching waveguide or a multi-mode waveguide.
The optical wave combining/splitting device executes optical signal separation operation when wavelength-multiplexed optical signals are input into the first input/output port
11
. Among optical signals, each optical signal having a wavelength within the first selective wavelength band is output from the port
17
a
of the second input/output port
17
, each optical signal having a wavelength within the second selective wavelength band is output from the port
17
b
, and each optical signal having a wavelength within the third selective wavelength band is output from the port
17
c
. The optical wave combining/splitting device executes wave combining operation when an optical signal in each selective wavelength band is input. The combined optical signal is output from the first input/output port
11
.
In the optical wave combining/splitting device, optical signal which is input from the first input/output port
11
is broadened to 2
j
times by the distributor
13
and is input to the first star coupler
15
a
. Here “j” is a positive integer.
FIG. 6
indicates the case when j=1. As a consequence, optical signals in a state were the band is substantially broadened and light intensity is flat are input into the first star coupler
15
a
, as shown in
FIG. 6
(B). Therefore a selective wavelength band of the optical signal which is output from each port of the second input/output port
17
can be broadened, and also flatness of light intensity of each output optical signal having a wavelength within the respective selective wavelength band can be improved.
With the above described conventional optical wave combining/splitting device, however, light intensity (power) of each output optical signal having a wavelength within the same selective wavelength band drops because the distributor
13
broadens the optical signal which is input from the first input/output port
11
. Consequentially, excess loss of optical signals occurs causing a problem.
For example, in order to broaden a selective wavelength band of each output port to double, while keeping light intensity of each output optical signal within the band substantially the same, a method for increasing another stage in a Y branching waveguide or a method for broadening mode width of the multi-mode waveguide to double is available, but regardless what method is used, 3 dB power loss occurs. If the selective wavelength band is broadened to 2
j
times, then j×3 dB of power loss occurs.
An object of the present invention is to provide an optical wave combining/splitting device (i.e., optical multiplexer/demultiplexer) which can implement expansion of a selective wavelength band and flattening of light intensity within the selective wavelength band as good as or better than prior art, and also has less power loss than prior art.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the present invention, an optical wave combining/splitting device, that is, optical multiplexer/demultiplexer comprises the first input/output port, a period characteristic wavelength splitter that is connected to the first input/output port, a diffraction grating wavelength splitter comprised of arrayed waveguides that is connected to the above splitter, and the second input/output port comprised of multiple ports that is connected to the diffraction grating wavelength splitter. The diffraction grating wavelength splitter comprises the first star coupler, the first arrayed waveguide comprised of multiple waveguides having different optical path lengths, and the second star coupler, which are sequentially positioned from the period characteristic wavelength splitter side.
The period characteristic wavelength splitter comprises the third star coupler that is connected to the first input/output port, the second waveguide array comprised of multiple waveguides having different optical path lengths that is connected to the third star coupler, and the fourth star coupler of which one end is connected to the second arrayed waveguide and the other end is connected to the first star coupler. When optical signal is input from the first input/output port to the period characteristic wavelength splitter, separate optical signals which wavelengths are sequentially deviated with difference &dgr; are output from the multiple ports at the first star coupler side of the fourth star coupler respectively, and periodic optical signals with wavelength difference &Dgr;&lgr; are output from any one of the ports.
Functions of the optical wave combining/splitting device of the invention are now described using concrete examples. In this example, an optical signal whose central wavelength is &lgr;
0
is input to the first input/output port of the optical wave combining/splitting device of the invention as a wavelength-multiplexed optical signal, which includes each optical signal of &lgr;
1
, &lgr;
2
, &lgr;
3
and &lgr;
4
which wavelengths are sequentially deviated with the first wavelength interval &dgr;, and optical signal &lgr;
5
which wavelength is deviated from &lgr;
1
with the second wavelength interval &Dgr;&lgr;, optical signal &lgr;
6
which wavelength is deviated from &lgr;
2
with &Dgr;&lgr;, optical signal &lgr;
7
which wavelength is deviated from &lgr;
3
with &Dgr;&lgr;, and optical signal &lgr;
8
which wavelength is deviated from &lgr;
4
with &Dgr;&lgr;.
When this optical signal is input from the first input/output port to the period characteristic wavelength splitter, the period characteristic wavelength splitter outputs a set of optical signals having wavelength difference &Dgr;&lgr; from each port at the first star coupler side of the fourth star coupler using its function. In this configuration example, a set of optical signals, &lgr;
1
and &lgr;
5
, is output from one port, a set of optical signals &lgr;
2
and &lgr;
6
from another port, a set of optical signals &lgr;
3
and &lgr;
7
from another port, and a set of optical signals &lgr;
4
and &lgr;
8
from another port (the wavelength is split or demuliplexed).
Since the period characteristic wavelength splitter is a splitter using a star coupler, each optical signal &lgr;
1
~&lgr;
8
which was split as above is an optical signal which substantially maintains the peak level of the optical power when the optical signal was input to the first input/output port.
&lgr;
1
~&lgr;
4
, which were separated as above by the period characteristic wavelength splitter, are combined or multiplexed by the diffraction grating wavelength splitter which is comprised of arrayed waveguides (details are desc
Boutsikaris Leo
Burdett James R.
OKI Electric Industry Co., Ltd.
Spyrou Cassandra
Venable
LandOfFree
Optical wave combining/splitting device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical wave combining/splitting device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical wave combining/splitting device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2508442