Optical communications – Transmitter and receiver system – Including compensation
Reexamination Certificate
2000-08-23
2004-08-24
Sedighian, M. R. (Department: 2633)
Optical communications
Transmitter and receiver system
Including compensation
C398S030000, C398S031000, C398S033000, C398S057000, C398S059000, C398S079000, C398S102000
Reexamination Certificate
active
06782210
ABSTRACT:
This application is based on Japanese Patent Application Nos 11-238794 (1999) filed Aug. 25, 1999 and 2000-70872 filed Mar. 14, 2000 in Japan, the contents of which are incorporated here into by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical packet routing system for routing an optical signal by using the optical label signal carrying the control information necessary for the routing of the optical signal, more particularly, to a multiple-wavelength optical source unit to be used for a network system whose a plurality of communication nodes are connected by the wavelength routing system and an optical communication unit and an optical communication method to be used for an optical communication system whose internode communication among the communication nodes is made through a routing unit.
2. Description of the Related Art
With the explosive spread of the internets, and portable personal telephones and the like, the research and development activities for the establishment of large-capacity network are under way both at home and abroad. With the communication nodes constituting each of the existing networks, an optical signal transmitted through an optical fiber transmission line is converted into an electric signal; an address information and the like carried by the signal is read out; the signal is electrically switched to a desired output port according to the information; the signal is converted into an optical signal at the output port; and the optical signal is then transmitted through the optical fiber transmission line. However, with the exponential-growth in the communication traffic, in the near future, the routing processing capacity by the electrical routing processes is considered to reach its limit. To overcome this problem, it is important for the communication nodes to establish a routing method for enabling the routing of the signal within the optical layer, that is, a routing method for enabling the routing without converting the optical signal into the electric signal.
As a technique for realizing the above goal, the wavelength routing technique is coming to the fore. In the case of the wavelength routing technique as schematically illustrated in
FIG. 1
, any optical signal fed into a given input port can be routed selectively to different output ports according to its wavelength without being converted into an electric signal, by using an optical device (e.g., arrayed-waveguide grating) having a wavelength selectivity.
FIG. 2
schematically illustrates the general composition of the network system interconnecting a plurality of communication nodes by utilizing the wavelength routing function of the cyclic-wavelength arrayed-waveguide grating. In the case of this network system, with a cyclic-wavelength arrayed-waveguide grating
60
having a wavelength routing processing function, the optical signal transmitted from a communication node is routed in the form of the light according to its wavelength without undergoing any electrical processing for routing, so that high-speed routing is possible.
To illustrate the composition of
FIG. 2
, the network system comprises N number of communication nodes
30
(communication nodes #
1
-N) and a cyclic-wavelength arrayed-waveguide grating
60
having a wavelength routing processing function. Each communication node
30
comprises transmitter equipment
40
and receiver equipment
50
. The transmitter equipment
40
comprises N number of optical sources
41
for transmitting optical signals having wavelengths &lgr;
1
-&lgr;n.
The optical signals (wavelength: &lgr;
1
-&lgr;n) transmitted from the transmitter equipment
40
of each communication node
30
are introduced into the input ports of the cyclic-wavelength arrayed-waveguide grating
60
having the wavelength routing processing function. The cyclic-wavelength arrayed-waveguide grating
60
routes the optical signals incoming from various communication nodes
30
to different output ports according to the wavelengths, &lgr;
1
-&lgr;n, of the optical signals. Since this routing processing of the optical signal is carried out according to the wavelength of the optical signal while maintaining the form of the light without being subjected to any electrical processing, the high-speed routing is possible.
The optical signals (wavelength: &lgr;
1
-&lgr;n) came out from the output ports of the cyclic-wavelength arrayed-waveguide grating
60
is introduced into the receiver equipment
50
in each communication node
30
.
The detail of the wavelength routing processing by the cyclic-wavelength arrayed-waveguide grating
60
will be described referring to FIG.
3
. Optical signals (wavelength: &lgr;
1
-&lgr;
4
) varying in wavelength transmitted from various communication nodes (#
1
-#
4
) are fed to the input ports
61
a
-
61
d
of the cyclic-wavelength arrayed-waveguide grating
60
. In this case, the optical signal transmitted from the communication node #
1
to the input node
61
a
is outputted from the output port
62
a
when its wavelength is &lgr;
1
, from the output port
62
b
when its wavelength is &lgr;
2
, from the output port
62
c
when the wavelength is &lgr;
3
and from
62
d
when the wavelength is &lgr;
4
.
The optical signal to be transmitted from the communication node #
2
to the input port
61
b
is outputted from the output port
62
d
when its wavelength is &lgr;
1
, from the output port
62
a
when its wavelength is &lgr;
2
, from the output port
62
b
when its wavelength is &lgr;
3
, and from the output port
62
c
when its wavelength is&lgr;
4
.
The optical signal to be transmitted from the communication node #
3
is outputted from the output port
62
c
when its wavelength is &lgr;
1
, from the output port
62
d
when its wavelength is &lgr;
2
, and from the output port
62
a
when its wavelength is &lgr;
3
, and from the output port
62
b
when its wavelength is &lgr;
4
.
The optical signal to be transmitted from the communication node #
4
to the input port
61
d
is outputted from the output port
62
b
when its wavelength is &lgr;
1
, from the output port
62
c
when its wavelength is &lgr;
2
, from the output port
62
d
when its wavelength is &lgr;
3
, and from the output port
62
a
when its wavelength is &lgr;
4
.
Thus, by the routing to be carried out as described above, the optical signals having the same wavelengths respectively transmitted from the communication nodes #
1
-#
4
will never be outputted from the same output port. In other words, the wavelength routing by using the cyclic-wavelength arrayed-waveguide grating as is shown in
FIG. 3
is characterized by that the optical signals having the same wavelengths fed to different input ports of the grating are outputted from different output ports of the grating respectively, so that the conflict among the data having the same wavelengths with respect to the output port can be prevented.
However, in the case of conventional network system as is shown in
FIG. 2
, especially in the case of the network comprising N number of communication nodes, it is necessary to provide N number of optical sources with wavelengths strictly adapted to the wavelength characteristic of the cyclic-wavelength arrayed-waveguide grating with respect to each of the communication nodes and thus requiring N×N number of optical sources, which is a problem to be resolved. Especially, providing N number of optical sources for each communication node not only results in the increase in the burdens such as the increase in the size and cost of the communication node but also results in the increase in total cost of the network system.
Next, a prior art relating to the second embodiment of the present invention will be described.
Conventionally, as an optical communication system for carrying out the optical communication among a plurality of communication nodes through a router, a system shown in
FIG. 4
has been available.
The communication nodes
100
a
-
100
d
are respectively provided with one of th
Kato Kazutoshi
Matsuoka Morito
Noguchi Kazuto
Okada Akira
Sakai Yoshihisa
Nippon Telegraph and Telephone Corporation
Sedighian M. R.
Workman Nydegger
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