At+t Corp.

At&t Intellectual Property I, L.p.

Vello Systems, Inc.

Cedric F Lam

Nicholas J Frigo

Patrick P Iannone

Kenneth Charles Reichmann

Martin Birk

Sheryl Leigh Woodward

Mark David Feuer

Alan H Gnauck

Aleksandra Smiljanic

Winston I Way

Mikhail Boroditsky

Techniques and apparatus for optical communication networks including fiber ring networks with protection switching to maintain optical communications when an optical failure occurs and to automatically revert to normal operation when the optical failure is corrected. Implementations include use of a circulating optical probe signal at an optical probe wavelength within the gain spectral range of optical amplifiers used in a fiber ring network to detect an optical failure.

Optical ring networks using circulating optical probe in protection switching with automatic reversion

A system and method for simultaneous delivery of a plurality of independent blocks of 500 MHz digital broadcast television services, stacking a plurality of RF blocks on a plurality of spectrally sliced WDM optical bands. The method for delivering a plurality of video blocks to a user terminal serviced by a remote node comprises the steps of receiving, by a first WDM, a broadband signal from a broadband signal source, separating, by the first WDM, the broadband signal into a plurality of optical hands, modulating each of the plurality of optical bands with a composite signal representing data in a plurality of independent RF blocks to form a plurality of modulated signals, forwarding the plurality of modulated signals to a second WDM to form a combined broadcast signal, transmitting the combined broadcast signal over feeder fiber to a remote node, selecting a RF block for distribution over a distribution fiber to a conventional satellite set-top box at a user's site and forwarding the selected RF block to the user's site. A novel method and system for reducing spontaneous beat noise is also described.

System for flexible multiple broadcast service delivery over a WDM passive optical network based on RF block-conversion, of RF service bands within wavelength bands

A system and method for simultaneous delivery of a plurality of independent blocks of 500 MHz digital broadcast television services, stacking a plurality of RF blocks on a plurality of spectrally sliced WDM optical bands. The method for delivering a plurality of video blocks to a user terminal serviced by a remote node comprises the steps of receiving, by a first WDM, a broadband signal from a broadband signal source, separating, by said first WDM, said broadband signal into a plurality of optical bands, modulating each of the plurality of optical bands with a composite signal representing data in a plurality of independent RF blocks to form a plurality of modulated signals, forwarding said plurality of modulated signals to a second WDM to form a combined broadcast signal, transmitting said combined broadcast signal over feeder fiber to a remote node, selecting a RF block for distribution over a distribution fiber to a conventional satellite set-up box at a user's site and forwarding said selected RF block to said user's site. A novel method and system for reducing spontaneous beat noise is also described.

Method for flexible multiple broadcast service delivery over a WDM passive optical network based on RF block-conversion of RF service bands with wavelength bands

A system and method for simultaneous delivery of a plurality of independent blocks of 500 MHz digital broadcast television services, stacking a plurality of RF blocks on a plurality of spectrally sliced WDM optical bands. The method for delivering a plurality of video blocks to a user terminal serviced by a remote node comprises the steps of receiving, by a first WDM, a broadband signal from a broadband signal source, separating, by the first WDM, the broadband signal into a plurality of optical bands, modulating each of the plurality of optical bands with a composite signal representing data in a plurality of independent RF modulated signals to form a plurality of modulated signals, forwarding the plurality of modulated signals to a second WDM to form a combined broadcast signal, transmitting the combined broadcast signal over feeder fiber to a remote node, selecting a RF block for distribution over a distribution fiber to a conventional satellite set-to box at a user's site and forwarding the selected RF block to the user's site. A novel method and system for reducing spontaneous beat noise is also disclosed.

Wavelength assignment schemes that provide full-connectivity in RANs with fixed-tuned OADMs. In the first scheme, wavelengths are assigned to nodes according to Hadamard code, and in the second scheme, bands of contiguous wavelengths are assigned to nodes. Simulation results show that on the average, the Hadamard wavelength assignment schemes approach the performance of RANs with OADMs that add-drop all wavelengths, while saving 50% of the TDM terminals. The saving of TDM terminals by using wavelength tunable OADMs vary in different cases. Tunable OADMs are advantageous for lower traffic granularity and more interactions of a RAN with the outside network.

Wavelength allocation in regional access network with optical add-drop multiplexers

A method and a system in which selected wavelengths of a wavelength division multiplexed (WDM) signal are modulated with multicast data for multicasting data services on an optical network. The WDM signal is received from a hub node of the optical network, such as a unidirectional ring network or a bi-directional ring network. A four-port wavelength crossbar switch (4WCS) selectably switches selected wavelengths from the optical network to a modulator loop. The modulator loop includes a multicast modulator that modulates the selected plurality of wavelengths with the multicast data. Each modulated wavelength is then switched back to the optical network by the 4WCS switch, and sent to a plurality of subscriber nodes of the optical network. This architecture allows a facility provider to be physically separated from a content provider, and affords the flexibility of selectively delivering multicast content to individual subscribers.

Delivering multicast services on a wavelength division multiplexed network using a configurable four-port wavelength selective crossbar switch

A system and method for simultaneous delivery of a plurality of independent blocks of 500 MHz digital broadcast television services, stacking a plurality of RF blocks on a plurality of spectrally sliced WDM optical bands. The method for delivering a plurality of video blocks to a user terminal serviced by a remote node comprises the steps of receiving, by a first WDM, a broadband signal from a broadband signal source, separating, by the first WDM, the broadband signal into a plurality of optical bands, modulating each of the plurality of optical bands with a composite signal representing data in a plurality of independent RF blocks to form a plurality of modulated signals, forwarding the plurality of modulated signals to a second WDM to form a combined broadcast signal, transmitting the combined broadcast signal over feeder fiber to a remote node, selecting a RF block for distribution over a distribution fiber to a conventional satellite set-up box at a user's site and forwarding the selected RF block to the user's site. A novel method and system for reducing spontaneous beat noise is also disclosed.

Method of flexible multiple broadcast service delivery over a WDM passive optical network based on RF Block-conversion of RF service bands within wavelength bands

Link robustness, chromatic dispersion and polarization mode dispersion (PMD) immunity can be improved in fiber optical system by using a method for receiving an optical double sideband signal over an optical fiber system, comprising the steps of splitting the received optical double sideband signal into an upper sideband signal and a lower sideband signal, photodetecting the upper sideband and the lower sideband, equalizing the photodetected upper sideband signal and the lower sideband signal, and combining the equalized upper sideband signal with the equalized lower sideband signal. While PMD compensation is envisioned as a major application, one may also use the method and system for chromatic dispersion compensation or dispersion slope compensation in high bit rate systems, i.e. using dispersion compensation fiber (DCF) for coarse compensation and diversity receiver with electrical equalizer for fine tuning.

System for mitigating the effects of fiber dispersion by separate detection of two transmitted sidebands

System for flexible multiple broadcast service delivery over a WDM passive optical network based on RF block-conversion of RF service bands within wavelength bands

Link robustness, chromatic dispersion and polarization mode dispersion (PMD) immunity can be improved in fiber optical system by using a method for receiving an optical double sideband signal over an optical fiber system, comprising the steps of splitting the received optical double sideband signal into an upper sideband signal and a lower sideband signal, photodetecting the upper sideband and the lower sideband, equalizing the photodetected upper sideband signal and the lower sideband signal, and combining the equalized upper sideband signal with the equalized lower sideband signal. While PMD compensation is envisioned as a major application, one may also use the method and system for chromatic dispersion compesation or dispersion slope compensation in high bit rate systems, i.e. using dispersion compensation fiber (DCF) for coarse compensation and diversity receiver with electrical equalizer for fine tuning.

Diversity receiver for mitigating the effects of fiber dispersion by separate detection of the two transmitted sidebands

A power spectrum measurement system and a method monitor a power spectrum of N-channels in an M-channel wavelength division multiplexed optical communication network, where N is less than or equal to M. An add-drop node in the network drops a channel and adds a channel for transmitting data on the network. The added channel has the same wavelength as the dropped channel. The power of the added channel is controlled to minimize crosstalk. The power spectrum measurement system includes a detection circuit and a processing circuit. The detection circuit is an inexpensive, scalable circuit for detecting the power of each channel. The processing circuit is connected to the detection circuit and calculates the power of each channel based upon the power detected by the detection circuit. The processing circuit also calculates power of the added channel for minimizing crosstalk. The calculated power of the added channel is a function of the powers measured for the N-channels, including but not limited to the average power of the N-channels or the powers of the channels adjacent the added channel. The calculated power is transmitted to the node adding the channel for controlling the power of the added channel.

Power spectrum monitoring and management in a wavelength division multiplexed network

A four-port wavelength-selective crossbar switch generates an add/drop wavelength signal from a wave division multiplexed (WDM) signal using a plurality of double-sided reflectors that selectively reflects a selected wavelength channel signal of the WDM signal through optical circulators to provide low crosstalk between the dropped and added wavelength signals. The switch also reduces the number of WDM MUX-DEMUX required to one half that compared to a traditional approach. Furthermore, the switch can be designed to be wavelength cyclic with individual free spectral ranges that can be independently set to either through or add/drop states.

Four-port wavelength-selective crossbar switches (4WCS) using reciprocal WDM MUX-DEMUX and optical circulator combination

An optical telecommunications network suitable for carrying broadcast and switched services. The network includes a wavelength division multiplexing (WDM) coupled to a waveguide grating router (WGR). In accordance with the invention, an adjacent input port is connected with the same optical content. Thus, its outputs are adjacent (or wrapped around). According, the optical power in each of the broadcast bands at the outputs remains the same but is reduced by a factor of two in power for each channel but occupying twice as many channels. This has the effect of increasing the SNR by a factor of two.

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Middletown, NJ, United States of America

Cedric F Lam