Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2000-04-25
2002-06-11
Lee, John D. (Department: 2874)
Optical waveguides
With optical coupler
Switch
C385S024000, C359S199200
Reexamination Certificate
active
06404940
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to an optical cross connect apparatus or system and an optical network, to which the WDM (Wavelength Division Multiplex) transmission technique is applicable.
(2) Description of the Related Art
So far, optical communications have principally employed point-to-point TDM (Time Division Multiplex) transmission. However, with the spread of the Internet or the like, the communication traffic volume (information communication volume) is on the explosive increase and an expectation or possibility exists that the information communication volume further increases afterwards; therefore, two approaches, that is, the speed-up of the TDM transmission and the high-density multiplexing in the WDM transmission, have taken place in the recent years.
Of these, the WDM transmission is expected as a technique to increase the communication volume without gaining the signal rate by utilizing the optical broadband characteristics effectively. The WDM transmission has been introduced initially for the purpose of increasing the number of wavelengths to be multiplexed in the field of the existing point-to-point transmission. Additionally, the configuration of a high-flexibility high-reliability optical network (such as a ring network) has started through the employment of the optical ADM (Add Drop Multiplexer) capable of dropping/adding optical signals in units of wavelengths.
In such a technical background, for example, an optical cross connect system (OCCS), designated generally at reference numeral
100
in
FIG. 63
, is expected as a next-generation system capable of constructing a higher-flexibility higher-reliability optical network.
In
FIG. 63
, the OCCS
100
, in contrast with the existing systems, can accommodate a large number of input/output optical fibers and, additionally, can accept optical signals different in transmission rate from each other, such as an OC (Optical Carrier)-
192
(STM (Signal Transfer Module)-
64
≈(almost equal) 10 Gb/s) and an OC-
48
(STM-
16
≈2.5 Gb/s) and an OC-
12
(STM-
4
≈620 Mb/s), through proper optical interfaces
300
to
600
so that the setting [exchange (cross connect)] of optical paths in units of wavelengths is feasible in a manner that an optical routing section (cross connect section)
200
conducts switching (routing) among output paths or performs wavelength conversion for or on these optical signals in units of wavelengths.
Accordingly, for example, if, as shown in
FIG. 63
, the OCCS
100
accommodates optical fibers constituting a trunk line system for a ring network or the like to form optical links (Inter-Office Link)
700
A and
700
B and additionally accommodates optical fibers organizing a different network to establish an optical link (Intra-Office Link) with the different network, it becomes possible to add an optical signal from the different network to the trunk line system in units of wavelengths or to drop a portion of an optical signal running on the aforesaid trunk line system to the different network.
In consequence, the OCCS
100
is capable of setting up a connection between the existing ring networks put individually in operation or of making a connection of the existing network other than ring networks to a ring network, thus constructing a new large-capacity optical network. For this reason, as a system which plays most important role in a future optical network, much attention has been focused on this OCCS
100
.
A detailed description will be given hereinbelow of the aforesaid routing section
200
constituting an essential part of the OCCS
100
.
FIG. 64
is a block diagram showing one example of principle configuration of the optical routing section
200
. In
FIG. 64
, the optical routing section
200
employs a typical non-blocking type switch circuit (three-stage switch configuration), referred to as a cross (Clos) type.
Furthermore, as
FIG. 64
shows, the first-stage switch unit
200
A comprises k n-input 2n-output (n×2n) type switch circuits
201
, the second-stage (intermediate-stage) switch unit
200
B comprises 2n k-input k-output (k×k) type switch circuits
202
, and the third-stage switch unit
200
C comprises k 2n-input n-output (2n×n) type switch circuits
203
.
Incidentally, the “M×M switch circuit” taken here signifies a switch which exhibits an ability to switch (selectively establish an output path) any one of M inputs (M denotes an integer being two or more) to any one of the M outputs. Furthermore, the aforesaid k corresponds to the number of input ports (output ports), for example, one optical fiber is connected (accommodated) to one port. Still furthermore, the aforesaid n is equivalent to the number of wavelengths multiplexed (the number of input wavelength types), for example, if an optical signal to be transmitted through the one optical fiber forms a 16-wavelength multiplexed optical signal, n=16, and if it forms a 32-wavelength multiplexed optical signal, n=32. That is, the number N of input/output channels of the optical routing section
200
shown in
FIG. 64
becomes N=n×k.
FIG. 65
shows a detailed configurational example of the optical routing section
200
based upon the foregoing three-stage cross type switch circuit arrangement. This configuration shown in
FIG. 65
is such that the number of input ports (output ports) is set at k=8 and the number of wavelengths to be multiplexed per port assumes n=32 (&lgr;
1
to &lgr;
32
), that is, the total number of input/output channels assumes N=8×32=256, while the first-stage switch unit
200
A employs 16 16×32 switch circuits
201
, the second-stage switch unit
200
B uses 32 16×16 switch circuits
202
and the third-stage switch unit
200
C uses 16 32×16 switch circuits
203
.
In addition, each of the 16=32 switch circuits
201
of the first-stage switch unit
200
A and each of the 32×16 switch circuits
203
of the third-stage switch unit
200
C are constructed using two 16×16 switch circuits
211
and 16 1×2 switch circuits
210
. That is, in the configuration shown in
FIG. 65
, the basic size of the switch circuits (basic switch size) becomes 16×16.
Furthermore, in
FIG. 65
, reference numeral
204
depicts each of
8
optical demultiplexer (filters) provided with each of the input ports. Each of these optical demultiplexers
204
demultiplexes a wavelength multiplexed optical signal from the corresponding input port according to each of wavelengths &lgr;
1
to &lgr;
32
so that, for example, the optical signals respectively having wavelengths of &lgr;
1
to &lgr;
16
are inputted to the 16×32 switch circuits
201
in odd numbers while the remaining optical signals respectively having wavelengths of &lgr;
17
to &lgr;
32
are inputted to the even-numbered 16=32 switch circuits
201
.
Still furthermore, reference numeral
205
denotes each of wavelength converters, whose number equals the total number of input/output channels (namely,
256
), for converting a wavelength &lgr;x (where x=1 to 32) of an optional input optical signal after subjected to the switching (routing) by the switch units
201
to
203
into a predetermined wavelength to an output port, and the wavelength converters
205
allow the optical routing section
200
to output an optical signal with an optional wavelength to an optical input port as an optical signal with a desired wavelength (idle channel) at a desired output port.
Moreover, reference numeral
206
designates each of 8 optical multiplexers provided with each of the output ports, and each of the optical multiplexers
206
multiplexes (wavelength-multiplexes) the optical signals, respectively converted in wavelength in the wavelength converters
205
, at every output wavelengths (&lgr;
1
to &lgr;
32
) to each of the output ports, and outputs the multiplexed optical signal to the corresponding output port.
Still moreover, reference numeral
207
(
208
) rep
Kuroyanagi Satoshi
Nakajima Ichiro
Tsuyama Isao
Fujitsu Limited
Lee John D.
Rahll Jerry T
Staas & Halsey , LLP
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