Sycamore Networks, Inc.

Massachusetts Institute of Technology

Richard A Barry

Naimish Patel

Steven G Finn

Eric Arthur Swanson

Jianying Zhou

Murat Azizoglu

Muriel Medard

John D Moores

Kristin A Rauschenbach

Naimish S Patel

Paolo L Narvaez

Derek E Spock

Anthony Chi-Kong Kam

Robert G Gallager

Suresh Subramaniam

Marc Robidas

John Z Jiang

Indicia are provided to a client of Out-of-Frame errors and message bit parity errors that occur during the transmission of a message through a network, wherein the message includes the client data multiplexed with other data and formatted into a message that includes a plurality of transport overhead bytes. The transport overhead bytes of the multiplexed can include both defined bytes and undefined bytes. Predetermined bytes in the transport overhead may be used to store indicia of errors that are detected during the message transmission. These predetermined bytes are read by the client at the egress of the network. The transport overhead may contain both a section overhead portion and a line overhead portion and the predetermined bytes may be encoded in either a subset of the section or line overhead bytes. In addition, the indicia of errors may be encoded in an undefined portion of the section or line overhead. Alternatively, a portion of the section or line overhead that is defined may be redefined and used to store the encoded error indicia

Method for transparent multiplexing of SONET/ SDH streams

A Bi-directional Link Self-healing Network (BLSN) for implementing bi-directional link automatic protection switching (APS) for an arbitrary edge or node redundant network and a technique for implementing APS recovery in response to an edge or node failure in a network is described. The BLSN technique does not require permanent allocation of spare capacity for each connection and allows sharing of capacity among many network connections by allocating capacity for use only in the event of a failure. The described technique allows loopback protection to be performed over node or edge redundant networks and operates such that the remains connected after the failure of a node or an edge in the network. The technique makes use of connected directed subgraphs of the network. Also described are techniques for generating the directed subgraphs on node and edge redundant networks having an arbitrary network topology.

Method and apparatus for automatic protection switching

An optical bit rate for communication systems. The optical bit rate converter converts an ultra-high speed optical data stream to a lower rate optical data stream. In one embodiment, the optical bit rate converter converts the ultra-high speed optical data stream to a lower rate optical data stream that can be detected and processed electronically. The optical rate converter includes a buffer presenting a repeating optical data bit pattern, an optical sampler presenting an optical sampling bit stream, and an optical correlator. The optical correlator has a first input in communication with the output of the buffer and a second input in communication with the output of the optical sampler. The optical correlator produces a rate-converted optical data bit stream at its output in response to the repeating optical data bit pattern produced by the buffer and the optical sampling bit stream produced by the optical sampler. In one embodiment, the buffer has a data input and stores an optical data bit stream received from a high speed optical data source. In another embodiment, the optical bit rate converter time dilates the repeating optical data bit pattern received from the buffer. In yet another embodiment, the optical bit rate converter demultiplexes the repeating optical data bit pattern received from the buffer. The invention also relates to a method for rate-converting an ultra-high speed optical data stream to a lower rate optical data stream.

Optical bit rate converter

A method of allocating channels and paths to connections along candidate channel-paths in a network, where a candidate channel-path comprises a candidate path and candidate channel along the candidate path, is performed by determining individual effects, on the network, of selecting candidate channel-paths. These include effects on at least one channel-path, other than a candidate channel-path, which shares links with the candidate path. Candidate channel-paths are selected based on the determined effects and allocated. In a preferred embodiment, determination of the effects on the network is based on path capacity. The embodiment can be used where a single connection has been requested, or alternatively, where multiple connections have been requested. A max-sum embodiment selects candidate channel-paths by first calculating a sum of path capacity-dependent values of a set of affected paths in the network for each of plural network states resulting from candidate channel-path allocations, and then selecting the candidate channel-paths yielding a maximum sum.

Method for establishing connections by allocating links and channels

A network including a control channel source node and a plurality of control channel destination nodes is interconnected by communications media in the form of a ring. The control and control channel destination nodes transfer information over a plurality of channels using wavelength-division multiplex techniques. The control channel source node transmits control information to all of the control channel destination nodes over a unitary control channel, and each of the control channel destination nodes drains off a portion of the energy of the signal comprising the control channel to facilitate decoding and processing of the control information contained therein. Each of the aspects, the control channel destination nodes can also generate status information for transfer to the control channel source node over the control channel. The control channel source node drains off the energy of the signal comprising the control channel to facilitate decoding and processing of the status information contained therein.

System and method providing control channel for wavelength-division multiplexed network

A Dense Wavelength Division Multiplexed (DWDM) optical transmission system that compensates for unequal channel performance over an extended fiber transmission distance. The DWDM optical transmission system includes optical transmitters at a transmitter end of a transmission path for transmitting respective channels of information at different wavelengths, a first pre-emphasis device for performing a first pre-emphasis technique on the respective channels, an optical multiplexor for combining the respective channels into a multi-wavelength optical signal for transmission on a single transmission fiber, at least one optical amplifier for amplifying the optical signal along the path, at least one second pre-emphasis device disposed along the path for performing a second pre-emphasis technique on the respective channels, an optical de-multiplexor for separating the optical signal into its component channels, and optical receivers at a receiver end of the path for receiving and detecting the information carried by the respective channels. The first and second pre-emphasis techniques performed by the respective first and second pre-emphasis devices compensate for unequal channel performance along the transmission path over a desired fiber transmission distance.

Method and apparatus for extending fiber transmission distance with multiple pre-emphases in optically amplified DWDM system

A high speed DWDM optical transmission system that reduces a fiber dispersion limit without reducing the total channel count of a multi-wavelength optical signal. The system achieves such reduction in the fiber dispersion limit by employing a multi-wavelength optical signal comprising a gap-free band structure, and performing per-band dispersion compensation on the optical signal by adjusting residual dispersion values associated with one or more of the bands. In one embodiment, the system includes a first dispersion compensation module (DCM) that provides a dispersion-compensated multi-wavelength optical signal containing wavelength-dependent residual dispersion to a band splitter. The band splitter separates the dispersion-compensated optical signal into a plurality of bands such that no band gaps are formed between adjacent bands, and provides each band to a respective second DCM configured to reduce the residual dispersion associated with that band to a predetermined range of residual dispersion values.

Method and apparatus for per-band compensation with gap-free band structure for high speed DWDM transmission

Data transmission apparatus includes first and second optical transmitters coupled to an optical link. A forward error correction (FEC) coder is coupled to the input of the second optical transmitter. A first information signal having a first information rate is provided to the first optical transmitter, and a second information signal having a second information rate is provided to the second optical transmitter. The use of the FEC coder enables the second information signal to have a higher information rate than the first information signal, while simultaneously enabling the respective output power levels of the first and second optical amplifiers to be substantially equal. The data transmission apparatus achieves higher data transmission capacity while retaining compatibility with pre-existing fiber spans and amplifier nodes. An optical transmission system incorporates an optical transmitter and an optical receiver having certain transmission characteristics, such as output power level, decision threshold level, etc., that are adjustable in response to bit error rate information. A bit error rate estimator is provided at the receiving end of the optical link. The bit error rate estimator estimates the bit error rate of the received information signal, and provides bit error rate information to the optical receiver, and/or the optical transmitter, and/or the optical link, based on the estimated bit error rate, in order to optimize the performance of the transmission system.

Method and apparatus for improving transmission performance over wavelength division multiplexed optical communication links using forward error correction coding

A wavelength-division multiplexed (WDM) system includes an optical communications link with one or more optical amplifiers cascaded from an input end to an output end. Each amplifier has a predetermined optical gain throughout a pass band, and passes optical signals in the pass band along the link. Transmitting optical communications equipment is coupled to the input end of the link and provides a WDM optical communications signal to the link. The WDM optical signal includes a number of spaced-apart optical signals, including data optical signals and at least one management optical signal, that reside in the pass band of the optical amplifiers. Receiving optical communications equipment coupled to the output end of the link receives the WDM optical communications signal, separates the management optical signal from the data optical signals, recovers management information from the separated management optical signal, and uses the recovered management information to carry out management functions. In one case, the management optical signal resides at an edge of the pass band of the optical amplifiers, for example at nm or nm in a system having optical amplifiers specified to operate from to nm.

Optical management channel for wavelength division multiplexed systems

A wavelength division multiplexed (WDM) optical communications network is configured and operated to enable transmitter output power for a given wavelength channel to be adjusted to achieve a desired optical signal-to-noise ratio (OSNR) for the channel independently of the power levels of other optical signals carried on the same path. Optical amplifiers in the optical links extending between the transmitter and an optical receiver are configured to operate with constant gain over a specified range of input optical signal power, and the links are configured such that the power level of the signal provided to each optical amplifier is within the specified range of input signal power to prevent the deep saturation of the optical amplifiers due to optical amplifier cascading. When a channel is being added or adjusted, the OSNR of the optical communications signal received by the receiver is measured, and the power of the signal transmitted by the transmitter is adjusted to attain a desired OSNR at the receiver. Due to the constant-gain operation and input power control of the optical amplifiers, the OSNRs of other signals carried on the path are not affected, so that it is unnecessary to adjust the output power of other transmitters providing signals to the path.

Optical power balancer for optical amplified WDM networks

A method and apparatus for generating first and second tree topologies for any source node in a network which can be represented as a node or an edge redundant graph, such that any node in the graph remains connected to the source node via at least one tree even after the failure of a node or an edge. This technique provides a recovery mechanism upon detection of a failure in a network.

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Brookline, MA, United States of America

Richard A Barry