Optical communications – Multiplex – Broadcast and distribution system
Reexamination Certificate
2000-08-09
2004-04-06
Chan, Jason (Department: 2633)
Optical communications
Multiplex
Broadcast and distribution system
C398S072000, C398S082000
Reexamination Certificate
active
06718140
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a full-mesh optical wavelength division multiplexing transmission network transmission device for transmitting a plurality of optical signals wavelength-division multiplexed among a plurality of transmitting and receiving apparatuses.
This specification is based on Japanese Patent Application (No. 11(1999)-229174) to Japan Patent Office, and contents described in this Japanese Patent Application will be incorporated as a part of this specification.
2. Descriptions of the Related Art
An optical wavelength division multiplexinging (WDM) transmission system, which transmits a plurality of optical signals on one optical fiber by allocating the signals to different wavelengths, can increase significantly the capacity of its transmission path. In addition, the optical WDM transmission system can perform wavelength addressing which is capable of allocating the destination information relating to the optical signals to the respective wavelengths. Furthermore, a star-type WDM system, in which an N×N wavelength multi/demultiplexer having a periodic wavelength demultiplexing property in input/output combination is arranged in the center so as to connect N transmitting and receiving apparatuses therebetween, can realize a full-mesh WDM transmission network device capable of interconnecting the apparatus through independent N×N signal paths by using only N wavelengths optical signals.
FIG. 25
is a block diagram for explaining a schematic constitution of a conventional full-mesh WDM transmission network device. Referring to
FIG. 25
, reference numerals
1
to
4
denote transmitting and receiving apparatuses;
5
to
8
, transmitters for sending WDM signals (wavelength &lgr;
K
:K=1, 2, . . . , N);
9
to
12
, receivers for receiving the WDM signals (wavelength &lgr;
K
:K=1, 2, . . . , N);
13
to
16
, 1×N wavelength multiplexers for multiplexing optical signals having different N wavelengths onto one optical fiber,
17
to
20
, 1×N wavelength demultiplexing circuits for demultiplexing the WDM signals wavelength-multiplexed on one optical fiber, into signals having N wavelengths;
21
, an N×N wavelength multi/demultiplexer having a periodic wavelength demultiplexing property in input/output combination, which has a first I/O port group (
1
,
2
, . . . , N on the left side) composed of N ports and the opposing second I/O port group (
1
,
2
, . . . , N on the right side) composed of N ports; and
22
to
29
, optical fibers for optically connecting the transmitting and receiving apparatuses
1
to
4
, to the I/O ports of the N×N wavelength multi/demultiplexer
21
. In the optical fibers
22
to
29
, the wavelengths &lgr;
K
(K=1, 2, . . . , N) of the WDM signals propagating on the optical fibers, the signals being wavelength-multiplexed, and the directions of the WDM signals to be transmitted, which are indicated by arrows, are shown.
In this prior art 1×N AWGs (arrayed-waveguide grating wavelength multi/demultiplexer) each having a first I/O port composed of one port and a second I/O port group composed of N ports facing the one first I/O port are used as the 1×N wavelength multiplexers
13
to
16
and the 1×N wavelength demultiplexing circuits
17
to
20
. An N×N AWG having a first I/O port group composed of N ports and a second I/O port group composed of N ports facing the first I/O port group and having a periodic wavelength demultiplexing property in input/output combination is used as the N×N wavelength multi/demultiplexer
21
.
FIG. 26
is a table showing a periodic wavelength demultiplexing property in input/output combination for N×N AWG (N=8), and a port connection rule between the transmitting and receiving apparatus and the AWG in the conventional full-mesh WDM transmission network device. The N×N AWG having the wavelength demultiplexing property of the periodic input/output relation can be realized by a method recorded in Japanese Patent Application No. 10(1998)-210679, and the like. The wavelength demultiplexing property between eight ports of the first input/output group of the N×N AWG and eight ports of the second input/output group thereof is periodic as shown by the wavelength &lgr;
K
(K=1, 2, . . . , 8) in FIG.
26
.
The N×N AWG is a circuit symmetrical with respect to the first I/O port group and the second I/O port group. For example, the multiplexed WDM signal wavelength &lgr;
K
(K=1, 2, . . . , 8) input from a predetermined port of the first I/O port group is wavelength-demultiplexed and output to each port of the second I/O port group. In contrast, the multiplexed WDM signal wavelength &lgr;
K
(K=1, 2, . . . , 8) input from a predetermined port of the second I/O port group is wavelength-demultiplexed and output to each port of the first I/O port group.
The arrows shown above the each wavelength &lgr;
K
in
FIG. 26
express the relation of the input/output among the ports. The arrows toward the right mean that the first I/O port group side is used as an input port and the second I/O port group side is used as an output port, and the arrows toward the left mean that second I/O port group side is used as an input port and the first I/O port group is used as an output port. To be more specific, in the conventional full-mesh WDM transmission network device, the whole of the first I/O port group side is used as the input port, and the whole of the second I/O port group side is used as the output port. Although there are 64 (8×8) paths among 8×8 AWG ports, the 64 paths can be independently established at only 8 wavelengths by using of the periodic wavelength demultiplexing property as shown in FIG,
26
.
By connecting the I/O ports of the AWG to each transmitting and receiving apparatus, signals can be transmitted independently therebetween through all the paths which can be established among the eight transmitting and receiving apparatuses. Moreover, since a specified wavelength &lgr;
K
is allocated to the respective path, if a wavelength corresponding to a receiver is selected on the transmitter side, a wavelength addressing function to transmit the signal automatically to an objective receiver can be realized.
FIG. 27
is a diagram for explaining the wavelength addressing. In
FIG. 27
, reference numerals
31
to
38
denote eight transmitting and receiving apparatuses (
1
) to (
8
), and
39
denotes a 8×8 AWG. The wavelength demultiplexing property of the 8×8 AWG and the port connection rule between each of the transmitting and receiving apparatuses and the 8×8 AWG are described in FIG.
26
. An optical signal having a wavelength &lgr;
2
transmitted from the transmitting and receiving apparatus (
1
)
31
is guided to the port
1
of the first I/O port group of the 8×8 AWG
39
, and switched within the 8×8 AWG
39
. The optical signal is then sent to the transmitting and receiving apparatus (
2
)
32
from the port
2
of the second I/O port group thereof. Similarly, a return signal &lgr;
2
sent back from the transmitting and receiving apparatus (
2
)
32
is transmitted to the transmitting and receiving apparatus (
1
)
31
via the 8×8 AWG
39
. For example, optical signals &lgr;
3
and &lgr;
5
transmitted from the transmitting and receiving apparatus (
1
)
31
are automatically delivered to the transmitter (
3
)
33
and the transmitting and receiving apparatus (
5
)
35
, respectively.
FIG. 28
is a graph showing atypical transmission spectrum property between certain input and output ports of the AWG fabricated as a silica-based planar lightwave circuit. Although a wavelength of an optical signal to be transmitted between the input and output ports is equal to &lgr;
K
, other than this optical signal also an optical signal (&lgr;
1
, &lgr;
2
, . . . , &lgr;
K−1
, &lgr;
K+1
, . . . , &lgr;
N
) input from the same port can be scarcely transmitted therebetween. This is t
Kamei Shin
Kaneko Akimasa
Kato Kuniharu
Suzuki Sen-ichi
Chan Jason
Nippon Telegraph and Telephone Corporation
Thelen Reid & Priest LLP
Tran Dzung
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