Note: Descriptions are shown in the official language in which they were submitted.
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WAVELENGTH DIVIDING CIRCUIT
WITH ARRAYED-WAVEGUIDE GRATING MONITOR PORT
Background of the Invention
1. Field of the Invention
The present invention relates to a wavelength multiplexing
optical communication technology, in particular, to a wavelength
multiplexer and divider optical circuit with an arrayed-waveguide
suitable for a wavelength multiplexing optical communication and
a wavelength dividing optical communication.
2. Description of the Related Art
A wavelength multiplexers are key devices in optical
wavelength division multiplexing (WDM) systems for high density
telecommunication.
Technologies of this type are disclosed in the following
references.
The first reference is "Arrayed-waveguide grating wavelength
multiplexers fabricated with flame hydrolysis deposition",
Hiroshi Takahashi and Yoshinori Hibino, Fourth Opto-electronics
Conference (OEC '92), Technical Digest, July 1992.
Fig. 2 shows an example of the structure of a conventional
wavelength dividing optical circuit by the first reference.
Referring to Fig. 2, an optical input signal of which optical
signals with wavelengths A1 to An have been multiplexed is
received from an input port 101. The input optical signal is
sent to an input port 121 of an arrayed-waveguide grating module
111. The arrayed-waveguide grating module 111 divides the input
optical signal into optical signals with wavelengths A1 to An and
outputs the resultant optical signals to output modules 141 to
-- 1 --
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14n of the arrayed-waveguide grating module 111. The arrayed-
waveguide grating module, for example, composes of SiO2-Ta2O3
waveguides performed with a 1 nm channel spacing. For detail of
the arrayed-waveguide grating wavelength multiplexer, refer to
the first reference.
Optical signals with wavelengths Al to An that are sent from
the output ports 141 to 14n of the arrayed-waveguide grating
module 111 to photo-couplers 151 to 15n, respectively. The
photo-couplers 151 to 15n each branch the received optical
signals with wavelengths Al to An to two paths. In other words,
the optical signals with wavelengths Al to An are sent to output
ports 161 to 16n and monitor optical signal photo-detecting
devices 171 to 17n. With the monitor optical signal photo-
detecting devices 171 to 17n, the optical signals with
wavelengths Al to An are monitored.
The second reference is "Optical fiber communication
technology", by Takaya Yamamoto, Multimedia transmission
technology series, Nikkan-kogyo Shinbun-sha, pp. 272-273, June
26, 1995.
Fig. 3 shows an example of a star coupler as a real example
of the arrayed-waveguide grating module 131 corresponding to the
input port 121. In Fig. 3, a hatched portion 10 is composed of
a material similar to that of a core portion of an optical fiber.
A peripheral portion 11 is composed of a material similar to that
of a clad portion of an optical fiber. The refractive index nl
of the hatched portion 10 is larger than the refractive index n2
of the peripheral portion 11. In reality, a structure of which
an optical fiber is branched to 128 paths and the average
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insertion loss is 23.7 dB has been proposed.
In a wavelength multiplexing optical communication, before
and after a wavelength-multiplexing/dividing operation is
performed, each optical signal should be monitored. In the
conventional wavelength multiplexer optical circuit, when optical
signals with respective wavelengths are monitored, they are sent
to photo-couplers. Thus, when the number of multiplexing
wavelengths is n, as in the photo-couplers 151 to 15n shown in
Fig. 2, n photo-couplers are required.
Thus, in the conventional wavelength multiplexer optical
circuit, the circuit scale is increased. The number of
fabrication steps of the optical circuit is increased. The power
loss of the optical signals is inevitable.
Summary of the Invention
The present invention is made from the above-described point
of view. An object of the present invention is to provide a
wavelength multiplexer optical circuit that allows the circuit
scale of an optical circuit thereof to be decreased, the
structure thereof to be simplified, and the number of fabrication
steps thereof to be decreased.
To accomplish the above-described object, a first aspect of
the present invention is a wavelength dividing optical circuit,
comprising an input port for inputting an optical signal of which
optical signals have been wavelength-multiplexed, an arrayed-
waveguide module, connected to said input port, for dividing the
wavelength of the optical signal received from said input port,
N output ports for outputting optical signals with respective
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wavelengths divided by said arrayed-waveguide module, and N
monitor output ports for outputting main signals with respective
wavelengths divided by the next order of the primary order of
interference of an arrayed-waveguide grating of said arrayed-
waveguide module.
A second aspect of the present invention is a wavelength
multiplexing circuit, comprising N input ports for inputting a
plurality of optical signals with respective wavelengths that are
multiplexed, an output port for outputting an optical signal that
has been wavelength-multiplexed by an arrayed-waveguide module
connected to said N input ports, and N monitor output ports for
outputting main signals that have been wavelength-divided by the
next order of the primary order of interference of an arrayed-
waveguide grating module of the arrayed-waveguide module.
These and other objects, features and advantages of the
present invention will become more apparent in light of the
following detailed description of a best mode embodiment thereof,
as illustrated in the accompanying drawings.
Brief Description of Drawings
Fig. 1 is a schematic diagram showing the structure of a
wavelength dividing portion according to an embodiment of the
present invention;
Fig. 2 is a schematic diagram showing the structure of a
wavelength dividing portion according to a related art reference;
and
Fig. 3 is a schematic diagram showing an example of the
structure of a stair coupler according to a related art
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reference.
Description of Preferred Embodiment
Next, an embodiment of the present invention will be
described. According to the embodiment of the present invention,
the internal structure of an arrayed-waveguide grating module is
changed. In a wavelength multiplexer transmitting system,
desired monitor optical signals are extracted in a arrayed-
waveguide grating module. Thus, the circuit scale of the
resultant apparatus can be decreased. The loss of the optical
signals can be decreased. The number of fabrication steps of the
apparatus can be decreased.
In other words, in the structure according to the present
invention, optical signals with respective wavelengths can be
separated only with a conventional arrayed-waveguide grating
circuit. Thus, the circuit scale of the resultant apparatus can
be decreased. The loss of the optical signals can be decreased.
The number of fabrication steps of the apparatus can be
decreased.
A wavelength dividing optical circuit according to the
embodiment of the present invention comprises an input port 101,
an arrayed-waveguide module 111, N output ports 141 to 14n, and
N monitor output ports 181 to 18n. The input port 101 receives
an optical signal of which optical signals with respective
wavelengths have been multiplexed. The arrayed-waveguide module
111 is connected to the input port 101. The arrayed-waveguide
module 111 divides the optical signal received from the input
port 101 into optical signals with respective wavelengths. The
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N output ports 141 to 14n output the optical signals with
wavelengths divided by the arrayed-waveguide grating module 131.
The N monitor output ports 181 to 18n output main signals with
respective wavelengths divided by the next order of the primary
S order of interference of an arrayed-waveguide grating module 131.
Output signals of the N monitor output ports 181 to 18n are sent
to monitor optical signal photo-detecting devices 171 to 17n,
respectively.
A wavelength multiplexing optical circuit according to an
embodiment of the present invention comprises N input ports, an
output port, and N monitor output ports. The N input ports
receive optical signals with respective wavelengths that are
multiplexed. The output port outputs an optical signal that has
been wavelength-multiplied by an arrayed-waveguide connected to
the N input ports. The N monitor output ports output main
signals with respective wavelengths that have been divided by the
next order of the primary order of interference of an arrayed-
waveguide grating module. The relation between the wavelength
dividing optical circuit and the wavelength multiplexing optical
circuit is in that the input port(s) and the output port(s) are
reversely disposed.
Preferred Embodiment
Next, with reference to Fig. 1, a preferred embodiment of
the present invention will be described. Fig. 1 shows the
structure of a preferred embodiment of the present invention.
Referring to Fig. 1, an optical signal of which optical signals
with respective wavelengths A1 to ~n have been multiplexed is
received from the input port 101. The optical signal received
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from the input port 101 is sent to the input port 121 of the
arrayed-waveguide module 111. The arrayed-waveguide grating
module 131 divides the optical signal into optical signals with
wavelengths A1 to ~n and branches the divided optical signals to
the optical signal output ports 141 to 14n of the arrayed-
waveguide module 111 and the monitor optical signal output ports
181 to 18n thereof.
The optical signal output ports 141 to 14n output optical
signals of the primary order of interference received from the
arrayed-waveguide grating module 131. The monitor optical signal
output ports 181 to 18n output optical signals of the next order
of the primary order of interference received from the arrayed-
waveguide grating module 131.
Signals with respective wavelengths A1 to ~n received from
the optical signal output ports 141 to 14n are sent to the output
ports 161 to 16n, respectively. Monitor optical signals received
from the monitor optical signal output ports 181 to 18n are sent
to the monitor optical signal photo-detecting devices 171 to 17n,
respectively.
According to the above-described embodiment, when the number
of multiplexing wavelengths of the wavelength dividing optical
circuit is n, since n photo-couplers can be reduced from the
conventional structure, the number of connections of optical
parts can be decreased and the physical size thereof can be
decreased.
As described above, according to the present invention, in
consideration of a wavelength dividing optical circuit of which
the number of multiplexing wavelengths is n, n photo-couplers can
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be reduced from the conventional structure. Thus, the number of
connections of optical parts can be decreased. The physical size
of the optical circuit in the resultant apparatus can be
decreased. In addition, since the size of the optical circuit is
decreased and no photo-couplers are used, the loss of optical
signals can be suppressed.
Although the present invention has been shown and described
with respect to a best mode embodiment thereof, it should be
understood by those skilled in the art that the foregoing and
various other changes, omissions, and additions in the form and
detail thereof may be made therein without departing from the
spirit and scope of the present invention.
