Abstract: Briefly, in accordance with one or more embodiments, a band of signal carriers is divided into a first band of carriers and a second band of carriers. The carriers in the first band comprise shorter wavelength carriers, and carriers in the second band comprise longer wavelength carriers. Each of the optical sources in the first and second bands of carriers are modulated with an input signal and coupled together via a polarization maintaining coupler. These signals are then combined via a polarization beam combiner wherein the first band has a polarization state that is orthogonal, or nearly orthogonal, to a polarization of the second state.

Abstract: Polarization multiplexing with different differential phase shift keying (DPSK) schemes generally uses DPSK modulated signals modulated using different DPSK modulation schemes and combined with orthogonal polarizations relative to each other. The different DPSK modulation schemes may use different DPSK phase shifts to represent data, such as a regular DPSK modulation scheme and a ?/2 DPSK modulation scheme. By using different DPSK modulation schemes to represent data on the orthogonally polarized signals, the DPSK demodulators may effectively separate the orthogonally polarized signals using the property of the DPSK receivers. To optimize performance, the DPSK modulated signals may also be bit-interleaved when combined with orthogonal polarization.

Abstract: In general, optical communication systems and methods may implement a vestigial phase shift keying (PSK) modulation format to enable relatively high transmission rates with closer channel spacing and improved signal detection in a WDM optical communication system. A PSK modulated signal may be correlated with a phase shift, for example, using a delay line interferometer (DLI), to generate a vestigial PSK signal, which may be pre-filtered, combined, and transmitted in the WDM system. The correlation with a phase shift compresses and shifts the signal spectrum such that intersymbol interference (ISI) length may be reduced with minimal increase in the bit error rate (BER) when the vestigial PSK signal is detected.

Abstract: In general, optical communication systems and methods may generate higher-level nmQAM from nQAM signals using one or more delay line interferometers (DLIs) arranged in various configurations. The nQAM signals may be generated by a lower-level modulator, such as a BPSK modulator, QPSK modulator or lower-level QAM modulator, with binary driving signals. Different parameters of the DLIs, such as free spectral range (FSR), phase shift, and amplitude imbalance, may be selected to accomplish the desired higher-level nmQAM depending upon the nQAM signal.

Abstract: Communication from a component in an optical communication system may be effected by modulating a system power voltage across the component to generate voltage signals representing the information to be communicated. The voltage signals generated by the component are detectable in the power feed equipment (PFE) in the optical communication system. Signature analysis may be performed on the system voltage data to identify the voltage signals and determine the information being communicated.

Abstract: A system and method for monitoring an optical communication system. The system may include trunk terminals coupled through a trunk path and a branch terminal coupled the trunk path. A monitoring signal routing device within the branch terminal routes a monitoring signal from a branch-drop path to a branch-add path.

Abstract: Dispersion may be managed in an optical network by allowing accumulation of dispersion to at least ten thousand ps/nm, and several tens of thousands of ps/nm in some embodiments. The accumulated dispersion may be returned to zero or near zero at a receiver and/or at one or more branch paths coupled to the transmission path.

Abstract: A system and method for generating soft decision reliability information from hard decisions in an optical signal receiver. The receiver may include a digital signal processor including a symbol reliability function for generating symbol reliability information associated with symbols encoded on optical signal. The symbol reliability information may be generated as a function of the symbols and hard decision outputs associated with the symbols.

Abstract: A distributed messaging system and method allows servers in a network to share data, such as network status data associated with all of the servers in the network. In one embodiment, the distributed messaging system and method may be used in element management system (EMS) servers in a distributed network management system (NMS). The servers in the network share the data in a distributed manner by transmitting messages including the network status data, for example, using a star/broadcast method or a circular message queue (CMQ) method.

Abstract: An optical transmitter utilizing a multi-level data modulator to produce a PDM-QPSK signal, a one-bit delay interferometer configured to correlate the multi-level data modulated signal and an optical filter configured to combine the correlated multi-level data modulated signal with one or more neighboring signals prior to transmitting over one of a plurality of optical channels. The PDM-QPSK correlated signal is configured to reduce the signal spectrum thereby increasing spectral efficiency of the transmitted signal.

Abstract: Methods and systems for processing an optical signal in a communication system are disclosed. The disclosed methods yield benefits for estimation and tracking of carrier phase of received signals at a digital coherent receiver without the use of differential coding. Specifically, phase ambiguity is removed by calculating the slope of the CPE at a location where the CPE begins to lose track of the received carrier phase signal. As such, a CPE offset adjustment may be applied in accordance with the calculated slope to reduce the number of ones and zeros corrected by a FEC decoder. Thus, the FEC aided CPE scheme may be a feed forward scheme that requires no training.

Abstract: In general, a wavelength division multiplexed (WDM) communication system may use wavelength selective switching to simultaneously pre-filter and combine groups of channel wavelengths with orthogonal polarizations to provide a pre-filtered, pair-wise orthogonal aggregate WDM optical signal. An orthogonally-combining wavelength selective switch (WSS) multiplexer may route channel wavelengths individually from different sets of channels to a common output. The orthogonally-combining WSS multiplexer may also provide substantially orthogonal polarizations for the wavelengths in the different sets of channels. The different sets of channels may include odd channels and even channels.

Abstract: In general, wavelength division multiplexed (WDM) communication systems may use wavelength selective switching to aggregate and/or deaggregate groups or bands of channel wavelengths. A wavelength selective switch (WSS) band aggregator may combine a plurality of channel band aggregate optical signals to produce a combined aggregate optical signal (i.e., a transmitted WDM or DWDM signal). The WSS band aggregator may also combine one or more spectral portions of broadband noise with the bands of channel wavelengths such that the spectral portion(s) of the broadband noise occupies unutilized channels in the combined aggregate optical signal. A WSS band deaggregator may separate a combined aggregate optical signal (i.e., a received WDM or DWDM signal) to produce a plurality of channel band aggregate optical signals.

Abstract: A system and method for fault identification in optical communication networks. One or more repeaters in the system includes a loop back path that couples an output a first amplifier for amplifying signals carried in a first direction through a repeater to an input of a second amplifier for amplifying signals carried in a second direction through said repeater. Fault analysis is conducted using loop gain data associated with test signals transmitted on the first or second paths and returned on the opposite path through the loop back paths.

Abstract: In general, a wavelength division multiplexed (WDM) communication system simultaneously pre-filters and combines groups of wavelengths with orthogonal polarizations to provide a pre-filtered, pair-wise orthogonal aggregate WDM optical signal. In particular, an orthogonally-combining interleaving filter multiplexer provides substantially orthogonal polarizations for odd and even channel wavelengths and simultaneously pre-filters and combines the orthogonally polarized odd and even channel wavelengths using interleaver optics. The orthogonal polarizations may be provided by orientation of PM input fibers or by a polarization rotator in the orthogonally-combining interleaving filter multiplexer.

Abstract: An apparatus, system and method wherein a polarization multiplexed differential phase shift keying format (POLMUX-DPSK) is provided with offset and bit-interleaved frequency channels and demodulated using a DPSK demodulator.

Abstract: The present disclosure is directed to managing dispersion compensation in optical transmission line utilizing single mode fiber with no in-line dispersion compensation. A communication system terminal includes one or more dispersion compensation modules configured to compensate for at least a portion of optical dispersion associated with optical data signals supplied from the transmission line. A receiver communicatively coupled to the transmission line includes a digital signal processor configured to compensate for an additional portion of dispersion associated with the optical data signals converted to electrical signals by the receiver.

Abstract: A system and method for spectral loading unutilized channels of a partially loaded WDM system may be used to suppress spectral hole burning (SHB). Dummy tones may be loaded at different loading wavelengths within the band of system wavelengths such that the loading wavelengths are associated with a subset of unutilized channels in the WDM system. The loading wavelengths may be selected and spaced based on a distortion in the gain spectrum of the partially loaded WDM system such that the dummy tones alter the distortion to provide a desired gain spectrum.

Abstract: Methods and systems for processing an optical signal in a communication system are disclosed. The disclosed methods yield benefits for estimation and tracking of carrier phase of received signals at a digital coherent receiver. Specifically, phase ambiguity is removed by the insertion of pilot symbols into a transmitted data stream. Pilot symbols are detected from a received signal, and carrier phase is estimated for the detected pilot symbols. If carrier phase track of received data symbols was lost, a correction is applied to recover the track. Coherent symbol decoding may be used which has not been possible with prior art techniques due to the possibility of phase tracking loss.

Abstract: An inverse multiplexing communication path is established in at least one direction between nodes connected by a plurality of lower bandwidth bearing channels between the nodes, on which the content of a higher bandwidth signal is distributed and from which the original high bandwidth signal is recovered at the receiving node. During preliminary configuration, for example when selecting a subset of bearer channels from among a number of potential bearer channels, the bearer channels are chosen or are altered by signal processing to make the members of the subset perform similarly, thereby improving operations as compared to having the bearer channels bound to perform according to the performance of the least-performing member of the subset.