Cisco Technology, Inc.

Cisco Photonics Italy S.r.l.

Mauro Macchi

Ornan A Gerstel

Stefano Piciaccia

Mauro Rudi Casanova

Ronald Johnson

Gianpaolo Barozzi

Paolo Ottolenghi

Emanuela Grandi

Andrea Marchio

Ornan Gerstal

Gainluca Bonato

Switching architectures for WDM mesh and ring network nodes are presented. In mesh networks, the switching architectures have multiple levels&#x2014;a network level having wavelength routers for add, drop and pass-through functions, an intermediate level having device units which handle add and drop signals, and a local level having port units for receiving signals dropped from the network and transmitting signals to be added to the network. The intermediate level device units are selected and arranged for performance and cost considerations. The multilevel architecture also permits the design of reconfigurable optical add/drop multiplexers for ring network nodes, the easy expansion of ring networks into mesh networks, and the accommodation of protection mechanisms in ring networks.

Optical switching architectures for nodes in WDM mesh and ring networks

A reconfigurable WDM add/drop multiplexer and its method of operation at an add/drop node on an optical fiber carrying a plurality of WDM signals is described. The WDM add/drop multiplexer has a coupler and a demultiplexer element dropping WDM signals from the optical fiber to a plurality of drop terminals, and a wavelength-selective switch adding WDM signals from a plurality of add terminals onto the optical fiber. The coupler splits the WDM signals received from the optical fiber and passes the split WDM signals to the first and second output terminals. The demultiplexer element separates the split WDM signals at the plurality of drop terminals. The wavelength-selective switch, which has an input terminal for connection to the second coupler output terminal and an output terminal for connection to the optical fiber, selectively adds WDM signals on the plurality of add terminals to the optical fiber responsive to control signals.

Optical add/drop multiplexer with reconfigurable add wavelength selective switch

Systems and methods for verifying performance at an intermediate point in an optical link are provided by virtue of one embodiment of the present invention. One application is locating a fault along a long optical link while minimizing the need for trained personnel to inspect and monitor the link at numerous widely separated locations. At an intermediate point in the link, a portion of the optical signal present is tapped off and demodulated. By use of error correction decoding techniques on the demodulated data, the performance of the link up until that intermediate point may be verified.

Optical link performance monitoring

An optical receiver threshold may be optimized in real time based on a forward error correction (FEC) error statistics. A relative number of corrected ones as compared to corrected zeros is tracked. The threshold is shifted in response to an imbalance between the two types of errors.

Optimum threshold for FEC transponders

An optical transmission system and method for reducing non-linear distortion caused by the interaction of Self-Phase Modulation and Group Velocity Dispersion is disclosed. An optical link includes a transmitter for providing signals at a first optical wavelength, a transponder for converting the first optical wavelength to a second optical wavelength, a plurality of spans of optical transmission fiber and optical fiber amplifiers, a dispersion compensating device, and a receiver. The system operates at a relatively high input power level. The transponder includes a device for smoothing edges of the rise and fall times of optical pulses, such as an electrical attenuator and low pass filter, so that sharp-edged pulses received from the transmitter are transformed to a Gaussian shape. A dispersion compensating device, such as an optical fiber grating, also helps to improve the bit error rate as a function of receiver sensitivity despite an overall link length less than 600 km.

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Varese, Italy

Mauro Macchi