Optical communications – Multiplex – Optical switching
Reexamination Certificate
2000-06-21
2003-11-04
Pascal, Leslie (Department: 2633)
Optical communications
Multiplex
Optical switching
C398S068000, C398S087000
Reexamination Certificate
active
06643463
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a full-mesh optical wavelength division multiplexing transmission network system for transmitting a plurality of wavelength-multiplexed optical signals between a plurality of transmitting/receiving apparatuses.
BACKGROUND ART
In an optical wavelength division multiplexing (WDM) transmission system for transmitting a plurality of optical signals through a single optical fiber by assigning different wavelengths to each optical signal, it is possible not only to remarkably increase the capacity of the transmission path, but also to perform the “wavelength-addressing” operation in which information about the addressee of the relevant signal corresponds to each wavelength itself.
A star-topology WDM system includes an arrayed-waveguide grating type multiplexing/demultiplexing circuit (or arrayed-waveguide grating type multi/demultiplexer) in the center of the system, where this multiplexing/demultiplexing circuit has a wavelength response having a cyclic input/output relationship, and makes it possible to connect N transmitting/receiving apparatuses with each other. According to such a star-type WDM system, it is possible to realize a full-mesh WDM transmission network system only by using optical signals of N wavelengths, in which each of N×N signal paths for connecting the apparatuses with each other can be independently connected.
FIG. 4
is a schematic diagram showing the structure of a conventional full-mesh WDM transmission network system.
In the figure, reference numerals
1
to
7
indicate the 1st to Nth transmitting/receiving apparatuses (the 7th to (N−1)th apparatuses are not shown) for transmitting and receiving a WDM (wavelength-division-multiplexed) signal (of wavelengths &lgr;
1
to &lgr;
n
), reference numeral
8
indicates an N×N arrayed-waveguide grating type multiplexing/demultiplexing circuit (AWG) having N input and N output ports and having a wavelength response which has a cyclic input/output relationship.
FIG. 5
is a diagram showing the general structure of the full-mesh WDM transmission network system in FIG.
4
.
In
FIG. 5
, reference numerals
9
to
12
indicate the 1st to Nth transmitting/receiving apparatuses (the ith apparatus indicates any of the omitted apparatuses in the figure), reference numeral
13
indicates a receiver for receiving a WDM signal (of wavelengths &lgr;
1
to &lgr;
n
), reference numeral
14
indicates a transmitter for transmitting a WDM signal (of wavelengths &lgr;
1
to &lgr;
n
), reference numeral
15
indicates a demultiplexer for demultiplexing a WDM signal transmitted through a single optical fiber, reference numeral
16
indicates a multiplexer for multiplexing a plurality of optical signals having different wavelengths transmitted from the transmitter
14
so as to transmit a signal through a single optical fiber, reference numeral
17
indicates an N×N arrayed-waveguide grating type multiplexing/demultiplexing circuit (AWG), and reference numerals
18
to
21
indicate optical fibers for optically connecting the transmitting/receiving apparatuses
9
to
12
and the input and output ports of AWG
17
. Here, the structure of each transmitting/receiving apparatus (
10
to
12
) is the same as the transmitting/receiving apparatus
9
.
FIG. 6
is a diagram showing the wavelength response having a cyclic input/output relationship, and the connection relationship between the transmitting/receiving apparatuses and the AWG ports in the conventional full-mesh WDM transmission network system. For a simple explanation, the case using an 8×8 AWG is shown in FIG.
6
.
Between 8 input ports and 8 output ports of the AWG, (8×8=) 64 paths can be established; however, the cyclic characteristic as shown in
FIG. 6
makes it possible to independently establish 64 paths using the minimum 8 wavelengths. The above input and output ports of the AWG are connected to each relevant transmitting/receiving apparatus, so that each signal can be independently transmitted via any possible path between the eight transmitting/receiving apparatuses. Here, a specific wavelength &lgr;
i
is assigned to each path. Therefore, it is possible to perform the wavelength addressing operation in which when the wavelength corresponding to a target receiver is selected at the transmitter side, a signal is automatically transmitted to the target receiver.
FIG. 7
is a diagram for explaining the wavelength addressing operation. In the figure, reference numerals
22
to
29
indicate 8 transmitting/receiving apparatuses, and reference numeral
30
indicates an 8×8 AWG. The wavelength response of the AWG and the connection relationship between the AWG ports and each transmitting/receiving apparatus are the same as those shown in FIG.
6
.
The optical signal of wavelength &lgr;
7
transmitted from the 1st transmitting/receiving apparatus
22
is introduced to input port
1
of AWG
30
, and is output from output port
2
to the 2nd transmitting/receiving apparatus by switching the optical signal in the AWG
30
according to its wavelength. Similarly, the response signal of wavelength &lgr;
7
transmitted from the 2nd transmitting/receiving apparatus
23
is transmitted to the 1st transmitting/receiving apparatus
22
via AWG
30
. In addition, the optical signals having wavelengths &lgr;
2
and &lgr;
8
are respectively and automatically transmitted to the 5th transmitting/receiving apparatus
26
and the 3rd transmitting/receiving apparatus
24
.
However, in the above conventional full-mesh WDM transmission network system, the addressee of the target signal one-to-one corresponds to a wavelength; therefore, if the transmitter relating to the relevant wavelength or the semiconductor laser used as a light source is damaged, a signal cannot be transmitted to a target receiver. Also if the receiver relating to the relevant wavelength is damaged, a similar problem occurs. These problems are serious for suitably operating and managing the system. Furthermore, in a conventional system, it is impossible to temporarily increase the transmission capacity between specific transmitting/receiving apparatuses.
DISCLOSURE OF THE INVENTION
In consideration of the above problems, an objective of the present invention is to provide a full-mesh optical wavelength division multiplexing transmission network system for suitably coping with a damaged transmitter or receiver corresponding to a specific wavelength, and for temporarily increasing the transmission capacity between specific transmitting/receiving apparatuses in case of need.
To achieve the above objective, the present invention provides an optical wavelength division multiplexing transmission network system comprising:
an arrayed-waveguide grating type multiplexing/demultiplexing circuit having N input ports and N output ports, where N is a plural number; and
N transmitting/receiving apparatuses, each apparatus being optically connected to a predetermined input port and a predetermined output port of the arrayed-waveguide grating type multiplexing/demultiplexing circuit, wherein:
the arrayed-waveguide grating type multiplexing/demultiplexing circuit has a wavelength response having a cyclic input/output relationship; and
each transmitting/receiving apparatus comprises:
a demultiplexer for demultiplexing an optical signal input from the predetermined output port of the arrayed-waveguide grating type multiplexing/demultiplexing circuit into signals of N wavelengths, and respectively outputting the demultiplexed optical signals from N output ports;
a transmitter for respectively transmitting optical signals of N wavelengths from N output ports;
a receiver for respectively receiving optical signals of N wavelengths from N input ports;
a multiplexer for multiplexing optical signals of N wavelengths input from N input ports, and outputting the multiplexed signal to the predetermined input port of the arrayed-waveguide grating type multiplexing/demultiplexing circuit; and
N 2-input and 2-output optical path switching elements correspondin
Akahani Junichi
Akatsu Yuji
Fukami Kennosuke
Harada Mitsuru
Kato Kazutosi
Krebs Robert E.
Nippon Telegraph and Telephone Corporation
Pascal Leslie
Thelen Reid & Priest LLP
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