Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
2001-01-02
2001-10-23
Pascal, Leslie (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200
Reexamination Certificate
active
06307654
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical ring architectures in general and, more particularly, to an optical node system for an optical ring architecture.
2. Description of the Related Art
Fiber optic systems have increasingly taken over the functions of their copper counterparts in the trunk network and between central offices due to their inherent low loss and high bandwidth. A typical central office ring configuration
100
is depicted in FIG.
1
and includes a plurality of central offices
101
a-d
. Each central office (CO)
101
a-d
is capable of transmitting calls to any of the other COs, either directly via direct connections
103
a-d
or indirectly through other COs as shown by logical connections
105
a-b
. Typically, a CO
101
a
includes an add/drop multiplexer (not shown) which adds calls to the ring
103
a-d
destined for another CO
101
b-d
or drops calls from the ring
103
a-d
for the CO
101
a.
FIG. 2
depicts a more detailed diagram of a ring architecture
106
of COs
101
a-c
. As shown, each CO
101
a-c
is capable of receiving and transmitting information over a plurality of optical fibers
107
. Typically, each fiber
107
operates at a predetermined optical wavelength or wavelength band, but a single optical fiber
107
could carry traffic having multiple wavelengths. The optical fibers
107
can be unidirectional in either direction or bi-directional. Some of the optical signals on the optical fibers
107
will terminate at the CO
101
a-c
in that terminal equipment (not shown) in the CO
101
a-c
converts the optical signal to electronic form, while other optical signals will continue through the ring
106
. In a typical example, an optical signal on a path
107
for destination equipment
110
is “dropped” from the ring by an add/drop multiplexer (not shown) in the CO
101
a
to terminal equipment (not shown) in the CO
101
a
The terminal equipment (not shown) in the CO
101
a
may convert the optical signal to an electrical signal and pass the electrical signal along path
112
to destination equipment
110
. The path
112
could be copper lines, and the destination equipment
110
is typically a terminal.
Calls can be “added” to the ring from source equipment for destination equipment
118
. Source equipment
114
produces a signal along path
116
to the CO
101
a
. The path
116
could be copper lines for carrying electrical signals. In the CO
101
a
, the terminal equipment (not shown) receives the electrical signal and converts it to an optical signal. The add/drop multiplexer (not shown) in the CO
101
a
receives the optical signal and adds it onto a path
107
. The optical signal added is routed along one or more of the paths
107
interconnecting one or more of the other COs
101
a-c
and is eventually “dropped,” for instance, by an add/drop multiplexer (not shown) of the CO
101
c
which is connected to the destination equipment
118
. The add/drop multiplexer (not shown) passes the optical signal to terminal equipment (not shown) in the CO
101
c
. As described above, the terminal equipment (not shown) in the CO
101
c
passes the signal along path
120
to the destination equipment
118
. Each of the optical signals not being dropped at a particular CO
101
a-c
can be amplified and passed along to the next CO.
FIG. 3
shows a more detailed diagram of a CO
130
in a ring architecture. A CO
132
transmits over a path
134
a plurality of optical signals as a wavelength division multiplexed optical signal with wavelengths &lgr;
n
. . . &lgr;
n
. Instead of using spatial multiplexing where one wavelength is in each fiber, wavelength division multiplexing (WDM) can increase capacity or decrease costs because multiple wavelengths can be put on a single fiber. The optical signal is received by the CO
130
, and a pre-amplifier
138
might be used to amplify the optical signal. In particular, an erbium-doped fiber amplifier (EDFA) can be used to simultaneously amplify all of the optical signals having a plurality of wavelengths in a linear fashion. In this particular embodiment, an add/drop multiplexer
140
receives the optical signal. The add/drop multiplexer
140
includes wavelength selection devices
142
and
144
, such as a wavelength grating routers (WGRs). An example of a WGR is disclosed in “Integrated Optics N×N Multiplexer On Silicon”,.Dragone et al., IEEE Phot. Technol. Lett., Vol. 3, pages 896-899 (1991).
The WGR
142
routes the incoming optical signals as a function of wavelength, to a particular output port of the WGR
142
. For example, an optical signal at a wavelength of &lgr;
1
applied over the path
134
to WGR
142
is routed by the WGR
142
to path
146
. Moreover, an optical signal at a wavelength of &lgr;
2
applied over the path
134
to the WGR
142
is routed by the WGR
142
to path
148
. Optical signals having particular wavelengths can be “dropped” by the WGR
142
. In this particular example, an optical signal having a particular wavelength &lgr;
n
is routed onto path
150
by the WGR
142
and thereby dropped to terminal equipment
152
. The terminal equipment
152
includes a receiver
156
that receives the optical signal from the path
150
and converts the optical signal to an electrical signal, thereby terminating the optical path for that particular wavelength. The receiver
156
outputs the electrical signal to electrical circuitry
158
for routing the electrical signal to the proper destination equipment
160
. The electrical circuitry
158
can include a host digital terminal, switches and other electronic processors and circuitry. The destination equipment
160
can include subscriber telephones
162
a-b
, remote terminal equipment
164
connected to subscriber telephones
162
c-d
, or other local data networks.
If a call is placed by a subscriber telephone
162
a
, the electrical signal representing the call passes over path
166
to the CO
130
. At the CO
130
, the electrical circuitry
158
processes the call and sends the electrical signal to transmitter
170
. The transmitter
170
outputs an optical signal having the wavelength &lgr;
n
by using the electrical signal to modulate a laser that can produce light having the wavelength &lgr;
n
. The transmitter
170
transmits the optical signal via path
172
to WGR
144
, which multiplexes the optical signal onto the wavelength division multiplexed signal on path
174
. On the path
174
, the optical signal can be amplified by amplifier
176
, such as an EDFA, before being output from the CO
130
.
In current ring architectures, optical fibers corresponding to optical signals dropped at an add/drop multiplexer on the ring terminate at the add/drop multiplexer. For example, in
FIG. 3
, if an optical signal having wavelength &lgr;
n
is dropped at the add/drop multiplexer
140
, the optical fiber terminates at the terminal equipment
152
where the optical signal is converted to an electrical signal. For the add/drop multiplexer
140
to add the optical signal from the path
172
onto the path
174
, tile transmitter
170
must provide light having wavelength &lgr;
n
from an optical source. As such, a relatively costly and accurately tuned laser and its supporting electronics is used for each wavelength of optical signals dropped at each add/drop node on the ring. Thus, current ring architectures can be costly and inflexible.
Accordingly, a node configuration is needed for a more flexible ring architecture which reduces costs associated with current ring architectures.
SUMMARY OF THE INVENTION
The present invention relates to an optical node system for an optical ring network that reduces certain costs associated with current ring architectures by using at least a portion of the light from an incoming optical signal to transmit an outgoing optical signal. In accordance with certain embodiments, the node includes an add/drop multiplexer which receives optical signals having a plurality of wavelengths. The add/drop multiplexer can be configured to output optical signals hav
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Lucent Technologies - Inc.
Pascal Leslie
Singh Dalzid
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