Abstract: An apparatus and method for performing joint equalization and timing recovery in coherent optical systems. The method includes equalizing signals to generate compensated polarization signals, wherein timing error in a distorted optical signal is calculated based on one of the compensated polarization signals. The method further includes performing resampling polarization signals to correct timing offset in an optical signal based on the calculated timing error. The calculated timing error may also be used to adaptively control one or more operating parameters of an external device.

Abstract: A method for performing an optical line analysis of continuous data signals transmitted in a passive optical network (PON). The method comprises determining, from an optical signal of the optical line, at least one of a phase early/late indicator based on a phase position of an input continuous data signal relative to sampling clock signals, a difference phase indicator based on an input phase control code, and a low frequency jitter indicator based on an input phase control code; computing a plurality of statistical measures regarding frequency and amplitude components of a jitter of the input continuous data signal, wherein the statistical measures are computed based on one of the phase early/late information indicator, the difference phase indicator, and the low frequency jitter indicator; and analyzing the plurality of statistical measures to detect optical failures in the PON and determining a root cause of each of the detected failures.

Abstract: The present invention provides a communication apparatus on a subscriber side that, in a point to multi-point communication system, transmits upstream data transmitted from a lower-level device to a station-side device based on a data transmission start time and a transmission duration time notified from the station-side device. The communication apparatus includes a logical-link control unit that determines number of links to be used, which is number of logical links to be used for an upstream data transmission in a next bandwidth update cycle, based on an accumulated data amount in an upstream buffer unit that accumulates upstream data to be transmitted to the station-side device.

Abstract: The present disclosure provides dynamic performance monitoring systems and methods for optical networks to ascertain optical network health in a flexible and accurate manner. The present invention introduces accurate estimations for optical channel performance characteristics based either on existing channels or with a dynamic optical probe configured to measure characteristics on unequipped wavelengths. Advantageously, the dynamic performance monitoring systems and methods introduce the ability to determine physical layer viability in addition to logical layer viability.

Abstract: An optical communication system has a receiver that includes a plurality of photon counting sensors that each receive photons and generate pulses based on the received photons, and an electronic circuit that aggregates the number of pulses from the plurality of photon counting sensors into a merged pulse count. A demodulator samples the merged pulse count at predetermined time intervals to determine a number of photons received by the plurality of photon counting sensors during different sampling time intervals.

Abstract: A method and apparatus for detecting Passive Optical Network (PON) failures, and a PON system are provided to obtain the monitoring information of a peer device before a PON system failure occurs. The method includes: obtaining monitoring information of an Optical Line Terminal (OLT) and an Optical Network Unit (ONU); and determining a failure of a passive ONU according to the obtained monitoring information of the OLT and the ONU. The monitoring information of the peer device is obtained before a PON system failure occurs. Thus the failure is discovered in time, quick troubleshooting is ensured, and the costs of system maintenance are reduced.

Abstract: The exchange device groups PON branches into PON branch groups based on the amount of communication data traffic that has arrived via a communication network with a plurality of optical network units (ONUs) respectively belonging to one of a plurality of PON branches as a transmission destination, multiplexes the communication data for each PON group, and transmits the multiplexed data. The exchange device has an unit configured to transmit each piece of communication data from the ONUs to one output port selected from among a plurality of output ports based on the transmission wavelength of the communication data. The exchange device groups a plurality of PON branches into PON branch groups based on the required bandwidth of each of the ONUs, and designates the transmission wavelength for each of the ONUs so that each piece of the communication data from one PON branch group is transmitted to one port.

Abstract: In a representative embodiment, a disclosed receiver of an optical multicarrier offset-quadrature-amplitude-modulated (MC-OQAM) signal is configured to track and compensate for the phase error in the local-oscillator (LO) signal with respect to a carrier wave of a modulated subcarrier of the optical MC-OQAM signal by tracking a minimum of a cost function that is sensitive to crosstalk between in-phase and quadrature components of the modulated subcarrier and/or crosstalk between the modulated subcarrier and at least one other modulated subcarrier of the optical MC-OQAM signal. The receiver can operate based on pure feed-forward processing and compensate the phase error in real time and without relying on pilot symbols or a PLL circuit coupled to the LO source.

Abstract: The present invention is to provide a method applicable to a fiber-optic transceiver including a transmitter optical subassembly (TOSA) provided therein with a laser diode, but without a monitoring photodiode, a laser driver controlled by a controller IC for driving the laser diode to generate a laser beam, and a thermal sensor for sensing temperature of the laser diode. The method includes executing an approximation process to characteristic data, i.e.

Abstract: The embodiments relate to a method and an apparatus for compensating nonlinear damage. The method and apparatus being used in a dual-polarization communication system, the method comprising: calculating, according to input time-domain signals, a plurality of multiplicative parameters indicative of nonlinear damages to the input signals; constructing a plurality of multiplicators by using the plurality of multiplicative parameters; and compensating the input time-domain signals by using the plurality of multiplicators.

Abstract: A photodiode array includes a plurality of monitoring photodiodes capable operating in a voltage mode configuration each able to provide a voltage indicating an intensity of an incident light. Integrated with the monitoring photodiodes is a reference diode configured to produce reference voltages in response to reference currents supplied to that diode. The monitoring photodiodes and the reference diode may be integrated and have the same current-voltage characteristics and the same temperature, for example by fabricating them on the same substrate. The reference diode is supplied with the reference currents in dark manner, meaning without incident light impinging on the reference diode. The resulting reference voltages, the reference source currents, and the measured photo-voltage from the monitoring photodiodes are than used to determine an optical power value at any temperature within the operation temperature range.

Abstract: The path selection and wavelength assignment to a selected path are performed by mapping the wavelength reach to the demand distribution (agile reach) resulting in a 50-60% increase in the network reach. The network reach is further increased (about 2.2 times) when on-line measured performance data are used for path selection and wavelength assignment. The connections may be engineered/upgraded individually, by optimizing the parameters of the entire path or of a regenerator section of the respective path. The upgrades include changing the wavelength, adjusting the parameters of the regenerator section, controlling the launch powers, mapping a certain transmitter and/or receiver to the respective wavelength, selecting the wavelengths on a certain link so as to reduce cross-talk, increasing wavelength spacing, etc.

Abstract: A device and method for device association, interference mitigation and channel selection for use in a visible light communication (VLC) network. The method includes transmitting on every one of a plurality of supported color channels of a first device to estimate an ambient interference on each supported color channel. The method also includes receiving a transmission on at least some of the supported color channels, where the number of receiving color channels is less than or equal to the number of supported color channels of the transmitter. The method further includes calculating a channel quality index for each of the receiving color channels. The method still further includes selecting at least one of the receiving color channels of the first device to be used as a communication channel. The method also includes reporting the at least one communication channel to a second device in the VLC network.

Abstract: A method of closed loop control for an optical link is presented, utilizing a copper feedback connection between the optical transmitter and optical receiver, suitable for short distance applications. An architecture is provides that may be used to define and maintain an optimum optical launch power for a defined bit error rate, guaranteeing extinction ratio and absolute optimum operating power. The invention also includes the use of such a loop in achieving fast link initialization and dynamic optimization to compensate for all effects of time and temperature for all components within the link.

Abstract: Embodiments of the present disclosure relate to a method and a device for compensating for a time path. In the embodiments of the present disclosure, on the basis of not changing implemented 1588 synchronization architecture, a compensation unit is added on a service board unit, the compensation unit calculates a compensation time value for asymmetrical reception and transmission of fiber links and transfers the compensation time value into the service board unit, and the service board unit implements automatic compensation according to a port status. The method and the device for compensating for a time path according to the embodiments of the present disclosure may implement automatic compensation for receiving and sending fiber links without manually testing the asymmetry of links node by node, so that the embodiments of the present disclosure can be widely applied in time synchronization networks.

Abstract: An apparatus includes a first estimator that estimates a signal quality based on an error correction number of an electrical signal obtained by photoelectrically converting a received optical signal; a second estimator that estimates a signal quality from which the influence of nonlinear effects is removed based on signals upstream and downstream of an identification calculator identifying the electrical signal; and a calculator that calculates the difference between the signal qualities estimated by the first and second estimators to calculate the amount of nonlinear effects.

Abstract: A method for processing bandwidth is disclosed to improve the bandwidth assignment accuracy. The method for processing bandwidth includes: obtaining the buffered data amount reported by an optical network unit (ONU) at this time and the previous time; determining difference between the buffered data amount reported at this time and the buffered data amount reported at the previous time; and assigning bandwidth according to the difference of the buffered data amount and previously assigned bandwidth. A network device and a network system are also provided.

Abstract: Methods and apparatus for providing distance extension and other transport functions such as error monitoring, provisioning, and link/service management in a fiber channel path are disclosed. According to one aspect of the present invention, a transport node includes a processing arrangement and an output interface. The processing arrangement creates a first ordered set that includes information associated with an ability for the transport node to receive a first fiber channel frame, and inserts the first ordered set between a second ordered set and a third ordered set of a fiber channel stream. The output interface transmits the fiber channel stream, which includes the information regarding whether the transport node is capable of receiving the first fiber channel frame.

Abstract: A fiber optic system includes a transmitter configured to utilize a plurality of modulation formats and a receiver communicatively coupled to the transmitter and configured to utilize a plurality of modulation formats. The transmitter and the receiver are cooperatively configured to set a modulation format of the plurality of modulation formats based upon optical signal-to-noise ratio associated therewith. A flexible bandwidth adaptation method includes monitoring at least one aspect of an optical link at a network element, responsive to the at least one aspect, computing a new modulation scheme for the optical link, and, if a solution is found for the new modulation scheme, changing to the new modulation format.

Abstract: Methods, architectures, circuits, and/or systems for monitoring operating parameters and/or generating status indications associated with electronic device operation are disclosed. The method can include (i) monitoring a first operating parameter related to operation of the electronic device to determine a first parameter value, (ii) calculating a difference between the first parameter value and a predetermined value for the first operating parameter, (iii) monitoring a second operating parameter on which thresholds for operational warnings and/or alarms are based to determine a second parameter value, (iv) updating or changing the thresholds based on a predetermined change or event in the second parameter value, (v) comparing the difference to the updated or changed thresholds, and (vi) generating a corresponding one of the operational warnings and/or alarms when the difference crosses at least one of the thresholds in a predetermined direction.

Abstract: Methods, architectures, circuits, and/or systems for monitoring operating parameters and/or generating status indications associated with electronic device operation are disclosed. The method can include (i) monitoring a first operating parameter related to operation of the electronic device to determine a first parameter value, (ii) calculating a difference between the first parameter value and a predetermined value for the first operating parameter, (iii) monitoring a second operating parameter on which thresholds for operational warnings and/or alarms are based to determine a second parameter value, (iv) updating or changing the thresholds based on a predetermined change or event in the second parameter value, (v) comparing the difference to the updated or changed thresholds, and (vi) generating a corresponding one of the operational warnings and/or alarms when the difference crosses at least one of the thresholds in a predetermined direction.

Abstract: A transmitter in an optical communications system includes a digital signal processor for processing a data signal to generate a sample stream encoding successive symbols in accordance with a constrained phase modulation scheme having a constellation of at least two symbols and a modulation phase constrained to a phase range spanning less than 4?. A digital-to-analog converter converts the sample stream into a corresponding analog drive signal. A finite range phase modulator modulates a phase of a continuous wavelength channel light in accordance with the analog drive signal, to generate a modulated channel light for transmission through the optical communications system. A receiver in the optical communications system includes an optical stage for detecting phase and amplitude of the modulated channel light and for generating a corresponding sample stream, and a digital signal processor for processing the sample stream to estimate each successive symbol of the modulated channel light.

Abstract: [Problem] This invention aims at solving the problem of how a subscriber premises-side optical network unit can be switched to an evaluation mode without the use of a jig board. [Means for Solving the Problem] The invention refers to a subscriber premises-side optical network unit (ONU 10) which is connected to a center-side optical network unit (OLT 1a) via an optical transmission line (optical fiber 2, 4) and to an external device (switch 6) via an electric signal line (electric signal line 5); comprising a memory (memory switch 15a) the stored content of which can be directly or indirectly rewritten by the external device; a detection part (CPU 15) for detecting that the content of the memory has been rewritten; and a control part (CPU 15) for performing, when the detection part detects that the stored content of the memory has been rewritten, a control whereby the optical sending part which sends optical signals to the optical transmission line is put into a continuous light emission state.

Abstract: A method for measuring asymmetry in propagation delay of first and second links which connect a first node to a second node of a communication network. The method comprises measuring (101) a round trip delay of the first link. The round trip delay can be measured by transmitting (102) a test signal from the first node to the second node over the first link and receiving a reply to the test signal from the second node over the first link. The method further comprises measuring (105) a round trip delay of the second link. The round trip delay can be measured by transmitting (106) a test signal to the second node over the second link and receiving a reply to the test signal from the second node over the second link. A difference in the propagation delay of the first link with respect to the second link is determined (109) using the measured round trip delays of the first link and the second link.

Abstract: A transmission device transmits a frame to a correspondent device and receives a frame from the correspondent device. The transmission device includes: a measurement unit configured to perform a delay measurement that measures a period of time from when a frame is transmitted to the correspondent device until when a corresponding frame is received from the correspondent device; and a delay decision unit configured to determine a transmission delay between the transmission device and the correspondent device based on a plurality of target measurement results obtained from a plurality of delay measurements except for at least a first delay measurement among delay measurements performed by the measurement unit.

Abstract: The present disclosure provides a time synchronization method, including: acquiring, by a slave device, a first optical fiber transmission delay from a master device to the slave device, and a second optical fiber transmission delay from the slave device to the master device; exchanging a time synchronization signal with the master device, and calculating an initial time offset; adjusting the initial time offset by using the first optical fiber transmission delay and the second optical fiber transmission delay to obtain a corrected time offset; and adjusting a local clock according to the corrected time offset. Embodiments of the present disclosure further provide a corresponding device and system.

Abstract: A receiver for a communications link includes a receiver module and a host receiver. These two components can be tested independently. In one embodiment, the receiver module is characterized with respect to noise and distortion. The noise performance can be determined by comparing input and output signals of the receiver module, to determine the relative noise of the receiver module. The distortion performance can be determined by comparing the distortion of input and output signals of the receiver module, using a reference host receiver that includes an equalizer. The host receiver can be tested by using a reference receiver module.

Abstract: One embodiment provides a system for power saving in an Ethernet Passive Optic Network (EPON). The system includes an optical line terminal (OLT), an optical network unit (ONU), a traffic-detection module configured to detect status of traffic to and from the ONU, and a power-management module configured to place the ONU in sleep mode based on the detected traffic status. The ONU includes an optical transceiver that includes an optical transmitter configured to transmit optical signals to the OLT and an optical receiver configured to receive optical signals from the OLT.

Abstract: A binary intensity-modulated light signal to be monitored is split into three signal beams. The first and third beams are converted into electric signals. Frequencies of the first electric signal corresponding to a bit rate pass a filter bank. The intensity of the filtered signal is detected by an RF intensity detector. A delaying interferometer makes the second beam interfere with a light signal obtained by delaying the second beam by a predetermined delay time. One of the resulting interference signals is converted into an electric signal. The intensities of the amplified signal are detected by another RF intensity detector. The third electric signal is smoothed by the filter bank, and its average intensity is detected by a power detector. The intensities of the detected, amplified signals are found relative to the detected average intensity to determine wavelength dispersion and optical SNR or the tendency of their changes.

Abstract: A network comprising: (a) a fiber having first and second ends; (b) a transmitter connected to the first end of the fiber and configured to launch a test signal having a first wavelength down the fiber; and (c) a thin-film selective reflector configured to reflect the first wavelength, the thin-film selective reflector optically connected to the second end of the first fiber.

Abstract: A data transmission device may include: a transmitter unit; a receiver unit; an optical transmission path that connects the transmitter unit to the receiver unit and transmits an optical signal; and an electrical transmission path that connects the transmitter unit to the receiver unit and transmits an electrical signal. The transmitter unit may include: a light source unit that converts an input electrical signal from an exterior into an optical signal, and outputs the optical signal to the optical transmission path; and a transmitter-side control unit that outputs information on a physical quantity having a relation to intensity of the optical signal, which is output from the light source unit, to the electrical transmission path. The receiver unit may include: a light detecting unit that receives the optical signal transmitted through the optical transmission path and converts the optical signal into an electrical signal; and a receiver-side control unit.

Abstract: A virtual network operating center and a virtual command interface synchronize events occurring on a wavelength division multiplexed network with processing events in a connected server. Should a disaster or other interruption of the network occur, the virtual command interface synchronizes events which occur on the network and any attached servers or server clusters with a reference clock coupled to the server. An event queue connected to the virtual command interface preserves the order of messages having a time stamp and compares the timestamps with the reference clock coupled to the server which is used to determine data integrity. The queued events may be encoded as XML device call to update the representation of the network or portions thereof in the virtual network operation center.

Abstract: Integrated performance monitoring (PM); optical layer operations, administration, maintenance, and provisioning (OAM&P); alarming; amplification, and the like is described in optical transceivers, such as multi-source agreement (MSA)-defined modules. An optical transceiver defined by an MSA agreement can include advanced integrated functions for carrier-grade operation which preserves the existing MSA specifications allowing the optical transceiver to operate with any compliant MSA host device with advanced features and functionality. The optical transceiver can include CFP and variants thereof (e.g., CFP2, CDFP, CXP), OIF-MSA-100GLH-EM-01.0, CCRx (Compact Coherent Receiver), Quad Small Form-factor Pluggable (QSFP) and variants thereof (e.g., QSFP+, QSFP2), 10X10 MSA, XFP, XPAK, XENPAK, X2, XFP-E, SFP, SFP+, 300-pin, and the like.

Abstract: Methods, algorithms, architectures, circuits, and/or systems for determining the status of parameters associated with optical transceiver operation are disclosed. The method can include (a) accessing and/or monitoring parametric data for each of a plurality of parameters that are related to operation of the optical transceiver; (b) storing the parametric data in one or more memories; (c) comparing the parametric data for each of the plurality of parameters against at least one of a corresponding plurality of predetermined thresholds; and (d) generating one or more states indicating whether the parametric data for a unique one of the parameters has crossed one or more of the corresponding plurality of predetermined thresholds. The invention also relates to an optical triplexer, comprising the described optical transceiver.

Abstract: The disclosure provides a process method and apparatus for preventing an alarm jitter, which are applied to an ASON system. The method comprises: obtaining a time interval weight T between generation and recovery of an alarm of a device through a pretest (S202); comparing the time interval weight T with a predetermined standard time interval W of the device, and determining an alarm jitter processing policy to be adopted according to a magnitude relation between the time interval weight T and the standard time interval W, wherein the alarm jitter processing policy comprises performing a jitter preventing process for alarm information reported by a lower layer according to a priority and/or a type of an alarm (S204); and performing the jitter preventing process by using the alarm jitter processing policy (S206). The solution improves stability of a control plane, and increases flexibility and process capability of the system.

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: There is provided a communications system (10) comprising a plurality of base stations (12), a central station (16) and a fibre optic communications network (14). Each base station (12) comprises a shelter (20) for a passenger awaiting transport, the shelter (20) having a wireless network access point (22). The central station (16) is arranged to facilitate communication between each base station (12) and a communications network (18) and the fibre optic communications network (14) is arranged to facilitate communication between each base station (12) and the central station (16).

Abstract: Coherent optical receiver performance is optimized and made adaptable to changing optical channel conditions by providing feedback loops to adjust receiver parameters based on measured receiver performance.

Abstract: A method and apparatus for monitoring and controlling an optical node 100. The optical node 100 including one or more optical components 120, 121 or 122 connected by optical fibre carrying an optical signal 102. The optical signal 102 including a plurality of optical channels. A set of measurement sequences is determined, each measurement sequence defining a set of optical channels from the plurality of optical channels and a measuring sequence for measuring an optical property of the set of optical channels. A measurement sequence is selected from the set of measurement sequences based on the operating conditions of the optical node 100. The optical properties of the set of optical channels of the selected measurement sequence are measured. The measured optical properties are analysed to determine whether one or more optical components 120, 121 or 122 are causing the optical node 100 to operate outside the tolerance of a defined set of operating conditions.

Abstract: A three-way handshake method for optical messaging in a multi-domain optical network that includes a first pass from a source domain to a destination domain through intermediate domains on candidate working paths, collecting information identifying available routing resources for each working path, calculating a working path metric and storing each of the metrics at the respective border node, determining a path key of the topology of each domain working path and using the path key to identify the path outside its domain and determining the best working paths and border nodes to use. A second pass using the path keys for identifying the working path in each domain and reserving the identified routing resources and selecting which routing resources to use. A third pass identifying the selected routing resources and establishing an optical signaling message path between the source node and the destination node.

Abstract: The present application describes methods and systems that improve the optical signal to noise ratio performance of an optical network without the need to vary the free spectral range associated with a differential interferometer. This is achieved by varying an electrical bandwidth of an electronic device associated with the receiver. For example, the electrical bandwidth may vary in inverse proportion to the combined effective optical bandwidth of the transmission line carrying the optical signal. The techniques described herein a applicable to a wide variety of modulation formats, including mPSK, DPSK, DmPSK, PDmPSK, mQAM, ODB, and other direct-detection formats. Using the techniques described herein, the optical signal to noise ratio and bit error ratio performance of the optical network is improved without the need to provide costly and complex differential interferometers whose free spectral range is variable.

Abstract: One example embodiment includes an optical subassembly (OSA). The OSA includes a flex circuit, an optical port, and an active optical component subassembly. The flex circuit is constructed of at least one electrically-conductive layer and at least one electrical insulator layer. The optical port defines a barrel cavity and is mechanically coupled to the flex circuit at a flex connection. The active optical component subassembly is positioned within the barrel cavity and electrically coupled to the flex circuit.

Abstract: Reliable data transmission is secured without inviting large design changes by means of configuring an optical data transmission device in a manner so as to be provided with: data conversion units and optical communication control units that transmit to each of a first communication unit and a second communication unit disposed movably relative to one another an optical signal modulated in response to wired-line data input from a wired line, and that output wired-line data demodulated from the received optical signal to the wired line; a bit data input unit that receives input of bit data for emergency stops; a bit data output unit that outputs bit data for emergency stops; and bit data communication control units that control in a manner so as to transmit/receive input bit data via the optical communication control units using optical signals that are isolated from the optical signal corresponding to the wired-line data.

Abstract: Increasing data rates in next-generation optical networks requires a change in the type of optical modulation used to encode optical signals carried by the optical networks. Different types of optical modulation incur different optical impairments, which may degrade the fidelity of the optical signals by reducing the optical signal-to-noise ratio (OSNR). A method or corresponding apparatus in an example embodiment of the present invention provides a planning tool for deploying an optical network in a manner based on the optical modulation that reduces the cost and complexity of the deployed network. In one embodiment, the disclosed planning tool may adjust a model of the optical network to be deployed by changing the topology and/or the number and/or type of optical network elements in response to optical impairments for a given optical modulation.

Abstract: A method for monitoring a passive optical network (1), PON, having a tree-like structure with a main line (3) and at least two branches (6.1 to 6.3), comprising: transmitting a wake-up signal (10) from the main line (3) to at least two monitoring units (DPM1 to DPM3) arranged in the at least two branches (6.1 to 6.3), in each of the monitoring units (DPM1 to DPM3), detecting the wake-up signal (10) and transmitting a response signal (A, B, C) back to the main line (3), each of the monitoring units (DPM1 to DPM3) generating a pre-defined time delay (?tA to ?tC) between the detection of the wake-up signal (10) and the start of the transmission of the response signal (A, B, C), and receiving the response signals (A, B, C) at the main line (3), the receiving times (R1 to R3) of the response signals (A, B, C) being different from each other, the difference between the receiving times (R1 to R3) being adjusted by the pre-defined time delays (?tA to ?tC) of the monitoring units (DPM1 to DPM3).

Abstract: Modular kit of devices for variable distribution, mixing and monitoring of optical signals in the Internet and other networks is formed by an optical module interconnected with a control electronic module of the electronic system with two redundant power supply sources, which is subsequently interconnected with the communication computer module equipped with the user communication interface and the machine communication interface. Optical module has N optical inputs and M optical outputs where N and M are non-zero natural numbers, and in total the optical module contains N×M of 2×2 type Mach-Zender interferometer optical switching elements. Each of them has two optical inputs, two optical outputs and one electric input. Optical switching elements are mutually interconnected in a grid. Control electronic module is formed by N×M pulse-width modulators connected via an interface module to the communication computer module and to the power supply distribution block.

Abstract: One embodiment relates to an integrated circuit which includes a transmitter buffer circuit, a duty cycle distortion (DCD) detector, correction logic, and a duty cycle adjuster. The DCD detector is configured to selectively couple to the serial output of the transmitter buffer circuit. The correction logic is configured to generate control signals based on the output of the DCD detector. The duty cycle adjuster is configured to adjust a duty cycle of the serial input signal based on the control signals. Another embodiment relates to a method of correcting duty cycle distortion in a transmitter. Other embodiments and features are also disclosed.

Abstract: A method and apparatus for performing a path based quality check for a specified bit rate in a wavelength division multiplexing optical network is described. According to one embodiment of the invention, a method selects from a database one of the available paths as a currently selected path. The database stores a representation of the available paths from an access node of the optical network to other access nodes of the optical network. The method further determines a cumulative noise, cumulative chromatic dispersion, and a maximum allowable chromatic dispersion for the currently selected path. In addition, the method determines whether the currently selected path passes the path based quality check based on whether the cumulative noise is less than the maximum allowable noise at a specific bit rate and whether the chromatic dispersion is less than the maximum allowable chromatic dispersion at the specified bit rate.

Abstract: A PDL compensation technique is provided that reduces the number of and the number of types of the PDL compensators even if it is uncertain to determine which of the two polarization principal axes of an optical device has a larger loss. The PDL compensator according to the present invention is configured to, before an optical signal input from a first or a second input/output terminal enters a PDL compensation device, switch between the first polarization principal axis and the second polarization principal axis of the optical signal depending on which of the first and the second polarization principal axes has a larger loss or gain.

Abstract: A method of configuring a path between an ingress node and an egress node in an optical communications network, the path comprising a first hop and a subsequent hop. The method includes: a) selecting a candidate hop for the first hop of the path; b) obtaining a value of a signal feasibility parameter for the candidate hop; c) determining whether said value lies within an acceptable value range and if one is, accepting said candidate hop for the first hop of the path, and if one is not, repeating steps a. to c.; d) selecting a candidate hop for the subsequent hop of path; e) obtaining a value of a signal feasibility parameter for a combined path comprising the first hop and the candidate hop for the subsequent hop of the path; f) determining whether said value lies within an acceptable value range, if one is, acceptable value range accepting said candidate hop for the subsequent hop of the path, and if one is not, repeating steps d. and e.