Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2001-03-12
2004-04-20
Lee, John D. (Department: 2874)
Optical waveguides
With optical coupler
Switch
Reexamination Certificate
active
06724953
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical cross-connect apparatus for switching paths of light signals, and in particular, to an optical cross-connect apparatus for supervising quality and management information of light signals of which paths are switched and its signal supervising method.
2. Description of the Prior Art
An optical cross-connect system for switching paths of light signals transmitted into a system is equipped with an optical cross-connect apparatus (hereafter, abbreviated as OXC) having a light switch (Switch: hereafter, abbreviated as SW). It is possible to switch paths of large-capacity light signals by applying to this cross-connect system the wavelength division multiplex (hereafter, abbreviated as WDM) technology for multiplexing a plurality of signals of mutually different wavelength components. Various research and development on OXC equipped with optical SW are underway focusing attention on easiness of setting up a signal path, efficiency of protection and so on toward the information and communication age of increasingly larger-capacity (Chungpen Fan, “Examining an integrated solution to optical transport networking.”, Wavelength Division Multiplexing: (The first ever European meeting place for WDM Systems, Network, Marketing & Engineering Professionals), November 1997, London pp. 18-23).
FIG. 32
represents, as a concept, configuration of an optical cross-connect system to which such OXC is applied. An optical cross-connect system is equipped with a plurality of OXC, and is connected by an optical fiber transmission path on which light signals are mutually transmitted. Here, it has OXC
10
1
to
10
6
, and for instance, OXC
10
1
is connected with OXC
10
2
via optical fiber transmission path
11
1
, with OXC
10
5
via optical fiber transmission path
11
5
, and with OXC
10
6
via optical fiber transmission path
11
6
respectively. Also, OXC
10
4
for instance is connected with OXC
10
3
via optical fiber transmission path
11
3
with OXC
10
5
via optical fiber transmission path
11
4
, with OXC
10
6
via optical fiber transmission path
11
8
, and OXC
10
6
is connected with OXC
10
3
via optical fiber transmission path
10
7
respectively.
On operating an optical cross-connect system, in order to maintain the system reliability, it is necessary to supervise light signals that are switchable to various paths and manage transmission signals inside the system by each OXC as shown in FIG.
32
. For instance, there are many transmission paths for light signals transmitted from point A to point B. Therefore, each OXC supervises paths, quality states and so on of light signals, sets paths of light signals and avoids failure occurrence points. To be more specific, in OXC
10
1
,
10
6
,
10
3
and
10
4
, a service signal transmitted from point A to point B on path
12
indicated by dashed lines in
FIG. 32
supervises transmitted light signals as to their respective quality and management information
13
1
,
13
2
,
13
3
and
13
4
if included in them.
FIG. 33
represents an overview of conventional OXC for supervising quality and management information of such light signals. This OXC has light signal input terminals
20
1
to
20
n
(n is a natural number of 2 or more) to which light signals are inputted, n×n light SW
21
for having light signals inputted from n pieces of input port corresponding to each of these light signal input terminals
20
1
to
20
n
outputted from any one of n pieces of output port and switching their paths, light signal detecting section (hereafter, abbreviated as DET) for detecting quality of light signals outputted from n pieces of output port of n×n light SW
21
and management information included therein, light signal output terminals
23
1
to
23
n
to which light signals outputted from each of n pieces of output port of n×n light SW
21
are outputted, light signal supervising section (hereafter, abbreviated as SV)
24
for supervising quality and management information of light signals from the output ports detected by DET
22
1
to
22
n
and control section (hereafter, abbreviated as CNT)
25
for controlling path switching of n×n light SW
21
from supervising results of SV
24
.
n×n light SW
21
arbitrarily connects n pieces of input port with n pieces of output port according to a control signal from CNT
25
. DET
22
1
to
22
n
output light signals outputted from each output port of n×n light SW
21
as-is and detect various signal states by branching a part of them. Such detecting functions of DET are a light signal level detecting function, a signal-to-noise (hereafter, abbreviated as SN) ratio detecting function, a light reproduction and overhead (hereafter, abbreviated as OH) detecting function, and alight reproduction and OH terminating function. As prescribed by the Synchronous Digital Hierarchy (hereafter, abbreviated as SDH) and the Synchronous Optical Network (hereafter, abbreviated as SONET) for instance, this OH has information on frame synchronization, error supervising, maintenance, operation and so on inserted in a predetermined position of light signals composed in a frame of a predetermined format.
In conventional OXC of such configuration, light signals inputted from light signal input terminals
20
1
to
20
n
are inputted in n pieces of input port of n×n light SW
21
respectively, and as a result of path switching performed according to a control signal from CNT
25
, they are outputted from any one of n pieces of output port of n×n light SW
21
. And the light signals outputted from n pieces of output port of n×n light SW
21
have their quality and management information included in them detected at DET
22
1
to
22
n
respectively, and are also outputted from light signal output terminals
23
1
to
23
n
. Such detected information is supervised at SV
24
, and SV
24
instructs CNT
25
to change path setting for instance from the results of supervising. CNT
25
outputs a control signal responding to this instruction from SV
24
to n×n light SW
21
, and switches the path of light signals inputted from the input ports.
As a technology on OXC for supervising such light signals, in addition to this, the Japanese Patent Laid-Open No. 5-183509 “Light Switch and Optical Channel” for instance discloses a technology to perform path cutting or path setting for a light SW that supervises light signals branched on the one hand by a branching device provided per signal line and switches paths of light signals branched on the other hand by the branching device.
BRIEF SUMMARY OF THE INVENTION
Object of the Invention
However, the conventionally proposed OXC required DET for detecting information to be supervised from light signals for each one of n pieces of output port of a light SW, leading to larger size of OXC. Furthermore, as optical communication will increasingly spread and light signals will be of larger capacity, the number of ports of a light SW is destined to increase, and thus it becomes necessary to install additional DET to meet the increase, further leading to larger size and higher cost of OXC.
Thus, an object of the present invention is to provide OXC that is, even in the case where a light SW becomes large-seized, capable of supervising quality and management information of light signals passing through inside the apparatus with low-cost configuration.
SUMMARY OF THE INVENTION
In the present invention, an optical cross-connect apparatus includes: light switch means having n (n is a natural number of 2 or more) pieces of first port and at least (n+1) pieces of second port, which switches paths of light signals inputted from each of said first ports and has them outputted from any one of said second ports; light path control means for branching a path of said light switch means so as to have light signals inputted from any one of said first ports outputted from any two of said second ports; and light signal supervising means for supervising quality of light signa
Lee John D.
NEC Corporation
Song Sarah
Young & Thompson
LandOfFree
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