Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
2001-04-18
2003-12-30
Kim, Robert H. (Department: 2871)
Optical waveguides
With optical coupler
Input/output coupler
C385S014000, C385S129000, C385S130000, C385S131000
Reexamination Certificate
active
06671433
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an arrayed waveguide grating type optical multiplexer/demultiplexer used in at least either one of the optical multiplexer, the optical demultiplexer or the optical multiplexer/demultiplexer.
BACKGROUND OF THE INVENTION
In recent years, in the field of optical communications, research and development in wavelength division multiplexing (WDM) transmission systems as a method for increasing the transmission capacity drastically has been actively pursued and the practical application is now advancing. The wavelength division multiplexing transmission systems performs wavelength division multiplexing for transmission, for example, a plurality of lights each having a different wavelength from each other. In such wavelength division multiplexing transmission systems, an optical multiplexer/demultiplexer is required for demultiplexing a plurality of lights each having a different wavelength from each other from the light which has undergone wavelength division multiplexing or for multiplexing a plurality of lights each having a different wavelength from each other.
As an example of the optical multiplexer/demultiplexer, an arrayed waveguide grating (AWG) type optical multiplexer/demultiplexer is known. The arrayed waveguide grating type optical multiplexer/demultiplexer is composed by forming on a substrate
11
an optical waveguide unit
10
having a waveguide such as shown for example in FIG.
7
A.
The waveguide construction of the arrayed waveguide grating type optical multiplexer/demultiplexer comprises one or more optical input waveguides
12
arranged side by side, a first slab waveguide
13
connected to the output ends of the optical input waveguides
12
, an arrayed waveguide
14
connected to the output end of the first slab waveguide
13
, a second slab waveguide
15
connected to the output end of the arrayed waveguide
14
, a plurality of optical output waveguides
16
connected to the output end of the second slab waveguide
15
arranged side by side. And the arrayed waveguide
14
consists of a plurality of channel waveguides
14
a
arranged side by side.
Each of the aforementioned channel waveguides
14
a
, which propagates the light outputted from the first slab waveguide
13
, is formed of a predetermined different length from each other.
The optical input waveguide
12
or the optical output waveguide
16
is, for example, provided corresponding to the number of the signal lights each having a different wavelength from each other, for example, demultiplexed by arrayed waveguide grating type optical multiplexer/demultiplexer. The channel waveguides
14
a
are generally provided so many as for example 100 waveguides. But for the purpose of simple illustration the number of the waveguides of each waveguide
12
,
14
a
,
16
is shown informally in FIG.
7
A. In addition, the arrayed waveguide grating type optical multiplexer/demultiplexer is formed approximately symmetrical with respect to the broken line C in the drawing.
FIG. 7B
shows the enlarged schematic view within the frame A depicted by dotted line in FIG.
7
A. As shown in this figure, in the conventional arrayed waveguide grating type optical multiplexer/demultiplexer, the output ends of the optical input waveguides
12
of a rather curved shapes are directly connected to the input side of the first slab waveguide
13
. In addition, the input ends of the optical output waveguides
16
of rather curved shapes are directly connected to the output side of the second slab waveguide
15
likewise.
The optical input waveguides
12
are, for example, connected to the optical fibers of the transmitting side so that the light which has undergone wavelength division multiplexing can be introduced therein. The light introduced to the first slab waveguide
13
through one of the optical input waveguides
12
is diffracted by means of the diffraction effect, inputs into each of the plurality of channel waveguids
14
a
and propagates through the arrayed waveguide
14
.
The light propagating through the arrayed waveguide
14
reaches the second slab waveguide
15
and further condensed into the optical output waveguide
16
thereby being outputted. As the length of each channel waveguide
14
a
differs with each other by a predetermined length, a phase shift is generated in each light after having propagated through each channel waveguide
14
a
and so the phasefront of the lights inclines corresponding to the predetermined length. As the condensing position of the light is determined in accordance with the angle of the inclination, the condensing position of the light having different wavelength differs with each other. Hence, by forming the optical output waveguide
16
at the condensing position of the light of each wavelength, it is made possible to output lights each having a different wavelength from each other by a predetermined design wavelength spacing from the respective optical output waveguide
16
corresponding to each wavelength.
For example as shown in
FIG. 7A
, when the light which has undergone wavelength division multiplexing having a different wavelength &lgr;
1
, &lgr;
2
, &lgr;
3
. . . &lgr;n (n is a integer more than 1) from each other by a predetermined design wavelength spacing is inputted from one optical input waveguide
12
, the light is diffracted by the first slab waveguide
13
and reaches the arrayed waveguide
14
. Then, it propagates further through the arrayed waveguide
14
and slab waveguide
15
and condenses as described above to the different positions depending on their wavelengths thereby the lights having the different wavelengths input into the optical output waveguides
16
respectively. Further, they propagate through the respective optical output waveguides
16
and outputted from output end of the optical output waveguides
16
. By connecting an optical fibers to the output ends of each optical output waveguide
16
, the aforementioned lights of each wavelength can be taken out through the optical fiber.
In addition, as the arrayed waveguide grating makes use of the light reciprocal (reversibility) principle, it has not only a function as an optical demultiplexer but also has a function as an optical multiplexer. In other words, in case of inputting a plurality of different lights each having a different wavelength from each other by a predetermined wavelength from respective optical output waveguide
16
corresponding to each wavelength, to the contrary as shown in
FIG. 7A
, these lights are multiplexed through the propagating path reverse to the aforementioned path so that a light having the different wavelengths is outputted from the single optical input waveguide
12
.
In this arrayed waveguide grating type optical multiplexer/demultiplexer, the improvement in the wavelength resolution of the arrayed waveguide grating is proportional to the different length (&Dgr;L) between the adjacent channel waveguides
14
a
composing the arrayed waveguide grating. Consequently, by designing &Dgr;L a greater value, an optical multiplex/demultiplex of a light which has undergone wavelength division multiplexing having a narrow wavelength spacing becomes possible which the conventional optical multiplexer/demultiplexer could hardly realize. For example, by designing &Dgr;L a greater value thereby the design wavelength spacing for multiplexing or demultiplexing equals to or less than 1 nm, a multiplex/demultiplex function of a plurality of light signals having a wavelength spacing of 1 nm or less can be achieved so that the optical multiplex/demultiplex function of a plurality of lights required for the realization of a high density wavelength division multiplexing communications can be accomplished.
SUMMARY OF THE INVENTION
The arrayed waveguide grating type optical multiplexer/demultiplexer according to the present invention comprises one or more optical input waveguide arranged side by side, a first slab waveguide connected to the output ends of the optical input waveguides, an arrayed waveguide connected to the output end o
Kashihara Kazuhisa
Nara Kazutaka
Kim Richard
The Furukawa Electric Co. Ltd.
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