Abstract: Cross-layer information associated with a software defined networking-based (SDN-based) communication network is collected. One or more updates are sent to one or more network elements in the SDN-based communication network to control one or more local decisions made at the one or more network elements. The one or more updates are based on at least a portion of the collected cross-layer information. Preferably, the collecting and sending steps are performed by a controller implementing an SDN management plane associated with the SDN-based communication network.

Abstract: Various embodiments provide for detection of tapping of an optical signal. In one embodiment an optical fiber includes a cladding region and first and second core regions. The first core region has a first core medium having a first mode-dependent loss (MDL) figure of merit. The second core region has a second core medium having a second different MDL figure of merit. Tapping of the optical signal may be determined to occur when the MDL of the first and second optical signals differs by a predetermined threshold value.

Abstract: Methods and apparatus for managing the effects of dispersion in an optical transport system in which some of the system's nodes are connected to one another via inhomogeneous fiber-optic links. In one embodiment, an optical transmitter is configured to apply electronic and/or optical dispersion pre-compensation in the amount selected to cause the peak-to-average-power ratio of the optical signal in the lower-dispersion portion of the link to be relatively low (e.g., close to a minimum value). Advantageously, such dispersion pre-compensation tends to significantly reduce, e.g., in terms of the bit-error rate, the directional anisotropy exhibited by optical transmissions through the inhomogeneous fiber-optic links.

Abstract: An example apparatus includes a mode selective detector, a measurement module, a difference calculator and a threshold and alarm module. The mode selective detector detects a plurality of modes of a spatially multiplexed signal. The measurement module measures a parameter for the plurality of modes of the spatially multiplexed signal, wherein the parameter is a power or a signal to noise ratio (SNR). The difference calculator compares the measured parameter among a subset modes and/or among a known set of unperturbed parameters and determines a differential, the subset including at least one mode. The threshold and alarm module sets an alarm indicator when the differential is out of bounds.

Abstract: Various exemplary embodiments relate to a method, network node, and non-transitory machine-readable storage medium including one or more of the following: receiving a message at the network node; selecting a routing tree of a plurality of routing trees based on a plurality of weights associated with the plurality of routing trees; determining a next hop network node for the message based on the selected routing tree; and forwarding the message to the next hop network node.

Abstract: An optical receiver comprising an optical-to-electrical converter and a digital processor having one or more equalizer stages. The optical-to-electrical converter is configured to mix an optical input signal and an optical local-oscillator signal to generate a plurality of electrical digital measures of the optical input signal. The digital processor is configured to process the electrical digital measures to recover the data carried by the optical input signal. At least one of the equalizer stages is configured to perform signal-equalization processing in which the electrical digital measures and/or digital signals derived from the electrical digital measures are being treated as linear combinations of arbitrarily coupled signals, rather than one or more pairs of 90-degree phase-locked I and Q signals.

Abstract: An optical routing scheme in which an optical network having a mesh topology is configured to route optical packets through an optical routing layout superimposable with the mesh topology, but having a star-like topology. Using this routing layout, the optical network can be configured to transport optical packets from respective ingress nodes, through the hub node located at the star center, to respective egress nodes in a manner that enables a data throughput that approaches the theoretical capacity. No special hardware is required for implementing the hub functionality, and any node of the optical network can be configured to serve as the hub node. The latter feature enables relatively straightforward optimization of the optical routing layout and transmission schedule, e.g., by changing the identity of the hub node and adjusting the transmission schedule at the ingress nodes to synchronize packet arrivals to the hub node.

Abstract: The performance of randomized load balanced or selective, randomized load balanced networks is enhanced by using ingress traffic engineering in addition to randomized traffic splitting. By first using the capacity of all links leading to the final destination of traffic, the remaining capacity is freed up for best effort traffic. Traffic splitting rules that enhance the performance of randomized load balanced networks in terms of packet missequencing and other quality of service criteria are also described.

Abstract: An interferometer is provided that includes a first path and a second path. The first path is configured to propagate an electro-magnetic signal at a first wavelength. The second path is configured to convert a portion of the electro-magnetic signal from the first wavelength to a second wavelength for processing and is configured to convert the portion of the electro-magnetic signal from the second wavelength back to the first wavelength for interference with the electro-magnetic signal of the first path. The first wavelength may be an optical wavelength or any other suitable wavelength of the electro-magnetic spectrum. The second wavelength, which is different than the first wavelength, also may be any suitable wavelength of the electro-magnetic spectrum.

Abstract: In one embodiment, an optical receiver has a bulk dispersion compensator and a butterfly equalizer serially connected to one another to perform dispersion-compensation processing and electronic polarization de-multiplexing. The bulk dispersion compensator has a relatively large dispersion-compensation capacity, but is relatively slow and operates in a quasi-static configuration. The butterfly equalizer has a relatively small dispersion-compensation capacity, but can be dynamically reconfigured on a relatively fast time scale to track the changing conditions in the optical-transport link. The optical receiver has a feedback path that enables the configuration of the bulk dispersion compensator to be changed based on the configuration of the butterfly equalizer in a manner that advantageously enables the receiver to tolerate larger amounts of chromatic dispersion and/or polarization-mode dispersion than without the use of the feedback path.

Abstract: An example apparatus includes a mode selective detector, a measurement module, a difference calculator and a threshold and alarm module. The mode selective detector detects a plurality of modes of a spatially multiplexed signal. The measurement module measures a parameter for the plurality of modes of the spatially multiplexed signal, wherein the parameter is a power or a signal to noise ratio (SNR). The difference calculator compares the measured parameter among a subset modes and/or among a known set of unperturbed parameters and determines a differential, the subset including at least one mode. The threshold and alarm module sets an alarm indicator when the differential is out of bounds.

Abstract: Methods and apparatus for managing the effects of dispersion in an optical transport system in which some of the system's nodes are connected to one another via inhomogeneous fiber-optic links. In one embodiment, an optical transmitter is configured to apply electronic and/or optical dispersion pre-compensation in the amount selected to cause the peak-to-average-power ratio of the optical signal in the lower-dispersion portion of the link to be relatively low (e.g., close to a minimum value). Advantageously, such dispersion pre-compensation tends to significantly reduce, e.g., in terms of the bit-error rate, the directional anisotropy exhibited by optical transmissions through the inhomogeneous fiber-optic links.

Abstract: An optical transmitter configured to mitigate the adverse effects of fiber nonlinearity by altering the transmitted constellation symbols based on specific nonlinear characteristics of a fiber-optic link over which the optical transmitter is configured to transmit and on an a priori estimate of the nonlinear component of the optical-signal distortion in that fiber-optic link. In an example embodiment, each constellation symbol is altered by a respective perturbation amount determined using (i) a calculated or measured nonlinear transfer function corresponding to the fiber-optic link and (ii) a set of neighboring constellation symbols that are expected to contribute to the nonlinear distortion of the optical signal carrying the present constellation symbol due to the fiber nonlinearity. In various embodiments, different appropriate perturbation amounts can be selected to approximately pre-compensate nonlinear distortions caused by various nonlinear optical effects, such as four-wave mixing, etc.

Abstract: In a representative embodiment, a multipath channel and an optical subcarrier modulation scheme are designed in concert to cause different modulated subcarriers of the optical communication signal to become substantially uncorrelated over the aggregate signal bandwidth. Provided that the employed FEC code has sufficient error-correcting capability for average channel conditions, breakdowns in the operation of the FEC decoder and the corresponding system outages can substantially be avoided.

Abstract: An apparatus comprises an optical transmitter that comprises a processor and at least one optical modulator. The processor is configured to generate electronic representations of at least two pre-dispersion-compensated phase-conjugated optical variants carrying a same modulated payload data for transmission. The at least one optical modulator is configured to modulate the electronic representations, wherein an amount of dispersion induced on the pre-dispersion-compensated phase-conjugated optical variants depends on an accumulated dispersion (AD) of a transmission link through which the pre-dispersion-compensated phase-conjugated optical variants are to be transmitted. The amount of dispersion induced on the phase-conjugated optical variants may be approximately ?AD/2, where AD is the accumulated dispersion of the transmission link.

Abstract: An optical transmitter configured to perform digital signal equalization directed at mitigating the detrimental effects of a frequency roll-off in the transmitter's optical I-Q modulator. In various embodiments, a frequency-dependent spectral-correction function used for the digital signal equalization can be constructed to cause the spectrum of the modulated optical signal generated by the transmitter to have a desired degree of flatness in the vicinity of an optical carrier frequency and/or to at least partially mirror the frequency roll-off in the optical I-Q modulator.

Abstract: An optical-power-distribution (OPD) subsystem that provides means for supplying optical local-oscillator signals and optical-carrier signals to various optical line cards, without the need for each optical line card to have a corresponding individual laser source. In one embodiment, a single laser coupled to the OPD subsystem provides optical local-oscillator signals and optical-carrier signals to multiple optical line cards. In another embodiment, multiple lasers coupled to the OPD subsystem provide multiple optical local-oscillator signals and optical-carrier signals to a single line card. An OPD subsystem may provide significant power savings in the operation of the corresponding optical transport system, a reduction in the required equipment-cooling capacity, and an increase in the device-packing density within optical line cards and inside equipment cabinets that house optical line cards.

Abstract: An optical routing scheme in which an optical network having a mesh topology is configured to route optical packets through an optical routing layout superimposable with the mesh topology, but having a star-like topology. Using this routing layout, the optical network can be configured to transport optical packets from respective ingress nodes, through the hub node located at the star center, to respective egress nodes in a manner that enables a data throughput that approaches the theoretical capacity. No special hardware is required for implementing the hub functionality, and any node of the optical network can be configured to serve as the hub node. The latter feature enables relatively straightforward optimization of the optical routing layout and transmission schedule, e.g., by changing the identity of the hub node and adjusting the transmission schedule at the ingress nodes to synchronize packet arrivals to the hub node.

Abstract: One coherent optical receiver includes a 3×3 coupler for receiving a signal and a local oscillator into a first and a third input port respectively, and three detectors for detecting a respective output of the coupler to generate corresponding first, second and third detected signals. A detected signal is filtered by an Alternating Current (AC) coupler to generate a respective first, second or third filtered signal. An adder adds the first, the second and the third filtered signals to determine a directly detected signal term. A first subtractor subtracts the directly detected signal term from the first filtered signal to determine an in-phase signal. A second subtractor subtracts the directly detected signal term from the third filtered signal to determine a quadrature signal. A digital signal processor processes the in-phase signal and the quadrature signal to recover the optical signal.

Abstract: An optical transport system configured to transmit a set of two or more optical variants per bit-word, with the optical variants in the set being different from one another in one or more of the time of transmission, spatial localization, polarization of light, carrier wavelength, and subcarrier frequency. Differences between the optical variants may also be due to different respective constellation mapping. The optical variants of each set are detected and processed at the receiver in a manner that enables coherent summation of the corresponding electrical signals prior to constellation de-mapping. The coherent summation tends to average out the deleterious effects of linear and nonlinear noise/distortions imparted on the individual optical variants in the optical transport link because said noise/distortions are incoherent in nature. A BER reduction enabled by the use of optical variants may be implemented in addition to or instead of that provided by FEC coding.