Abstract: An apparatus and method directed to testing and optimizing performance of an optical transmission system is disclosed, including at least one broadband dispersion compensation unit (DCU) or at least one depolarization device. The depolarization device may be used alone or in combination with the at least one broadband DCU. A method for optimizing performance of data channels in initial loading (IL) and full loading (FL) configurations of the optical transmission system is also disclosed.

Abstract: A system and method for loading unutilized channels of a WDM system with noise to improve system performance. A transmitter amplifier may impart noise to unutilized channels by reducing amplifier input or providing feedback of the amplifier output. Noise signals may also be looped back to the transmitter from received signals.

Abstract: An apparatus and method directed to testing and optimizing performance of an optical transmission system is disclosed, including at least one broadband dispersion compensation unit (DCU) or at least one depolarization device. The depolarization device may be used alone or in combination with the at least one broadband DCU. A method for optimizing performance of data channels in initial loading (IL) and full loading (FL) configurations of the optical transmission system is also disclosed.

Abstract: A system and method using differential loop gain for fault analysis in line monitoring equipment. Differential loop gain data is calculated from loop gain data, and fault analysis is conducted using differential loop gain data, e.g. by comparing the differential loop gain data to predefined fault signatures.

Abstract: A system and method using for wavelength monitoring and control in a WDM optical communication system. An aggregate channel monitor detects crosstalk between channels in the aggregate signal. Channel spacing may be modified by an element management system in response to the output of the aggregate channel monitor.

Abstract: A system for signaling between elements in an undersea optical communication system including a cable signal generator. The signal generator includes line current modulation circuitry configured to impart modulation in line current provided on a power conductor of the transmission cable. A method of signaling between elements in an undersea optical communication system includes modulating a line current through an element and detecting the modulated current.

Abstract: A system and method for time domain reflectometry (OTDR) using multi-resolution code sequences. One or more subsets of a set of predefined complementary code sequences may be transmitted as an OTDR signal to provide multi-resolution capability.

Abstract: A system and method for suppressing beat noise in line monitoring equipment. A wavelength dither generator wavelength modulates a carrier wavelength of a test signal laser transmitter. A test code is modulated on the dithered carrier wavelength to provide a test signal output of the line monitoring equipment.

Abstract: A method of adjusting a decision threshold in an optical signal receiver. A forward error correction (FEC) decoder provides a feedback signal representative of corrected errors. The decision threshold is adjusted in response to a polarity of the received signal and to balance a number of corrected ones and zeros.

Abstract: A monitoring system and method may be used to monitor an optical communication system. A monitoring system and method may be used to derive loop gain data sets from optical time domain reflectometry (OTDR) or coherent optical time domain reflectometry (COTDR) data. A monitoring system and method may also use differential monitoring techniques to obtain data representing gain tilt in the transmission system and to locate an anomalous loss or gain in the transmission system.

Abstract: A method of managing gain tilt in an optical transmission segment including providing an optical transmission segment having a plurality of fiber optic cable spans and a plurality of repeaters coupled to the fiber optic cable spans. Gain tilt in the optical transmission segment is monitored. If negative gain tilt is accumulated at a repeater location in the transmission segment, the repeater at the repeater location is replaced with a higher gain repeater having a higher nominal gain value than the nominal gain value of the repeater being replaced.

Abstract: An optical transmission system may include a combination of higher gain repeaters and lower gain repeaters, arranged to manage gain tilt. The higher gain repeaters and lower gain repeaters may be arranged to allow net gain to vary (e.g., above and below zero) within a predetermined acceptable net gain excursion. In one embodiment, the higher gain repeaters have a nominal gain value higher than a nominal span loss value and the lower gain repeaters have a nominal gain value lower than the nominal span loss value.

Abstract: Dispersion may be managed in a branched optical network by using transmission segments having a single period segment dispersion map. One or more of such segments may be coupled to network nodes such as terminals or branching units such that dispersion may be managed even when the network is reconfigured. In one embodiment, a single period segment dispersion map provides dispersion compensation at the ends of the segment. In another embodiment, a single period segment dispersion-map provides dispersion compensation at the middle of the segment.

Abstract: An apparatus and method for decision threshold control in an optical signal receiver. A forward error correction (FEC) decoder provides a feedback signal representative of corrected errors. The decision threshold is adjusted to balance a number of corrected ones and zeros.

Abstract: A receiver for a differentially phase shift keying formatted optical signal, such as an RZ-DPSK formatted optical signal. Dither control loops are provided for controlling path length in a demodulator and/or for controlling the center wavelength of an optical band pass filter. A feedback loop is provided for controlling the gain of a pre-amplifier, and a method of protecting against optical transients by disabling a pre-amplifier is also provided. A preset delay may be provided to compensate for the differential delay in paths associated with the demodulator arms. When the signal is an RZ-DPSK modulated signal, a clock for retiming data from the optical signal may be derived from a signal on the data path.

Abstract: A receiver for a differentially phase shift keying formatted optical signal, such as an RZ-DPSK formatted optical signal. Dither control loops are provided for controlling path length in a demodulator and/or for controlling the center wavelength of an optical band pass filter. A feedback loop is provided for controlling the gain of a pre-amplifier, and a method of protecting against optical transients by disabling a pre-amplifier is also provided. A preset delay may be provided to compensate for the differential delay in paths associated with the demodulator arms. When the signal is an RZ-DPSK modulated signal, a clock for retiming data from the optical signal may be derived from a signal on the data path.

Abstract: A system and method for method of managing a network. Each of a plurality of servers includes an element management system (EMS) function for managing network elements within the network and a network management system (NMS) function for managing ones of the plurality of servers running the EMS function. An NMS function is activated on one of the servers when the plurality of servers shares a one network domain. When the network domain is divided into multiple domains, e.g. by a network failure, an NMS function is activated on at least one other one of the plurality of servers whereby each of the multiple network domains has at least one associated active NMS function.

Abstract: A system and method for soft decision forward error correction (FEC) decoding may be used to determine a possible error in a differential detection signal, for example, in a DPSK system. The system and method uses the constructive and destructive signals from a demodulator to provide an error locating signal. Using the error locating signal, the system and method converts the differential detection signal into a soft decision signal including multi-level soft values.

Abstract: A method and apparatus for controlling bias and alignment in an optical signal transmitter for providing intensity modulation and DPSK modulation to an optical signal, e.g. in an RZ-DPSK modulation format. Output power in dither signals applied to the bias signals may be detected by a low speed photodetector. One or more of the bias signals may be adjusted in a low speed control loop in response to an error signal obtained by mixing the detected signal with the low frequency dither signals.

Abstract: A monitoring system and method may be used to monitor an optical communication system. A monitoring system and method may be used to derive loop gain data sets from optical time domain reflectometry (OTDR) or coherent optical time domain reflectometry (COTDR) data. A monitoring system and method may also use differential monitoring techniques to obtain data representing gain tilt in the transmission system and to locate an anomalous loss or gain in the transmission system.