Abstract: An apparatus comprising a path computation element (PCE) configured for at least partial impairment aware routing and wavelength assignment (RWA) and to communicate with a path computation client (PCC) based on a PCE protocol (PCEP) that supports path routing, wavelength assignment (WA), and impairment validation (IV). Also disclosed is a network component comprising at least one processor configured to implement a method comprising establishing a PCEP session with a PCC, receiving path computation information comprising RWA information and constraints from the PCC, establishing impairment aware RWA (IA-RWA) based on the path computation information and a private impairment information for a vendor's equipment, and sending a path and an assigned wavelength based on the IA-RWA to the PCC. Disclosed is a method comprising establishing impairment aware routing and wavelength assignment for a plurality of network elements (NEs) in an optical network using routing and combined WA and IV.

Abstract: An optical transmission system includes multiple multiplexers connected in series and each multiplexing an optical signal and given signal light. Each of the multiplexers includes a multiplexing unit that multiplexes the given signal light that is subject to multiplexing and a second optical signal of a frequency that is adjacent to the frequency of a first optical signal that is included in the given signal light; a monitoring unit that monitors deviation between timings of the first optical signal that is included in the signal light multiplexed with the second optical signal by the multiplexing unit, and the second optical signal; and an adjusting unit that based on a result of monitoring by the monitoring unit, adjusts the timing of the second optical signal that is to be multiplexed with the given signal light, by the multiplexing unit.

Abstract: A service provisioning enabled management in Service Interoperability in Ethernet Passive Optical Network (SIEPON) switching subsystem. The delivery of network services to each of a plurality of subscribers coupled to an optical network unit (ONU) can be defined individually by the service provider. The service-specific functions within the ONU can be configured based on knowledge of the levels of provisioning of network services.

Abstract: The present invention discloses a method, device and system for managing information of an optical node in an optical distribution network, relates to management of information of an optical node in an optical distribution network, is capable of solving the problem of manual entry of information of an optical node being cumbersome, and is not limited by installation locations of the optical node. The method for managing information of an optical node in an optical distribution network includes: obtaining an identity code of an optical node; querying a pre-established optical node information table according to the identity code of the optical node, wherein the optical node information table comprises the identity code of the optical node and the installation location information of the optical node. The present invention is suitable for management of information of an optical node in an optical distribution network.

Abstract: An optical line terminal (OLT) includes an optical receiving assembly and a processor (4). A current mirror (1), a current-voltage conversion circuit (2) and a switching circuit (3) are connected in sequence between the optical receiving assembly and the processor (4). An energy storage circuit connected to ground is connected between the switching circuit (3) and the processor (4). The optical receiving assembly generates a response current according to the optical signal received. The current mirror (1) processes the current and then transmits it to the current-voltage conversion circuit (2). The conversion circuit (2) converts the current into a voltage signal and transmits the voltage signal to the switching circuit (3). The switching circuit (3) transmits the voltage signal outputted by the conversion circuit (2) to the energy storage circuit. The voltage signal is sampled and held by the energy storage circuit and then outputted to the processor (4).

Abstract: A system and method are provided for carrier frequency offset (CFO) estimation for coherent optical orthogonal-frequency-division-multiplexing (CO-OFDM) broadband systems. The method includes obtaining an initial estimate of a normalized CFO with an estimation range equal to ±L/2 subcarrier subspacing using a single training symbol with L identical portions. The method further includes obtaining a maximum likelihood (ML) estimate of the CFO by performing a local grid search based on the initial estimate.

Abstract: A Fiber Channel switch is provided for a relative addressing scheme for domain values to avoid losing portions of a Fiber Channel identifier. At a Fiber Channel switch, data is stored that assigns a relative domain field value to a run-time domain. The relative domain field value used for a Fiber Channel identifier is determined for devices connected to the switch based on the run-time domain of the devices and the virtual storage area network in which the devices are active. A Fiber Channel identifier is stored in a memory of the switch that comprises the relative domain field value determined for the device together with area and port values for the device. The relative domain value is either a reserved domain field value for an existing virtual storage area network or any of the regular domain field values for a new virtual storage area network.

Abstract: A wavelength division multiplexer terminal with a multiplexer arrangement with a first switching matrix, and a demultiplexer arrangement with a second switching matrix allows flexibility for connection transceivers to ports of the wavelength division multiplexer and wavelength division demultiplexer respectively. Optical monitoring receivers are connected upstream the wavelength division multiplexer and downstream the wavelength division demultiplexer for managing and supervising connections.

Abstract: The invention relates to a system and method of dispersion measurement in an optical fiber network. The invention provides means for transmitting from a transmitting node, using a single tunable laser transmitter, two consecutive bursts of data at different wavelengths ?1 and ?2 to a receiver node, wherein each burst of data comprises a unique sequence of amplitude modulated data, and wherein the two sequences are injected with a fixed known delay. The delay between the two consecutive bursts of data is maintained by selective switching of the tunable laser, such that clock recovery circuitry at the receiver node remains locked during the delay between the two bursts. The dispersion measurements method of the present invention is based on walk off and bit position detection between two wavelengths suitable for fast optical burst switching network is described. This method does not require an operator, extra equipment, or traffic interruption on the network.

Abstract: A system comprises a source of entangled photon pairs. The source is to place a signal photon and an idler photon in individual unknown quantum states but in a known entangled quantum state. One or more transmission channels are connected to the source. Each of the one or more transmission channels transmits one of the signal photon or the idler photon. Each of the one or more transmission channels is to substantially balance an instantaneous transmission loss with an instantaneous transmission gain distributed over a transmission distance. Analysis interferometers are configured to receive a corresponding one of the signal photon or the idler photon. Each of the one or more analysis interferometers is to perform a basis measurement on one of the signal photon or the idler photon. Single-photon detectors detect one of the signal photon or the idler photon.

Abstract: An emulated Optical Network Unit (ONU) platform executes the functions of multiple emulated ONUs to enable traffic emulation in a Gigabit-capable Passive Optical Network (GPON) for data traffic, control traffic and management traffic. The emulated ONU platform generates OMCI messages, PLOAM messages, DBRu messages, data traffic and control traffic according to respective statistical specifications in respective profiles of the emulated ONUs. The emulated ONU platform formats and encapsulates the emulated traffic for upstream transmission to an OLT system according to dynamic bandwidth allocation instructions received from the OLT system. The emulated ONU platform then sends the emulated traffic upstream to the OLT system, and receives downstream traffic from the OLT system.

Abstract: An Optical Network Unit (ONU) emulator enables traffic emulation in a Gigabit-capable Passive Optical Network (GPON) that couples an Optical Line Termination (OLT) system to the ONU emulator and carries mixed types of emulated ONU traffic and real ONU traffic. The ONU emulator includes one or more emulated ONU platforms; each emulated ONU platform includes multiple ONU emulator blocks, and each ONU emulator block includes circuitry to emulate multiple emulated ONUs simultaneously. An emulated ONU platform generates upstream GPON frames according to respective profiles of the emulated ONUs, and sends the upstream GPON frames to the OLT system. At least a subset of the upstream GPON frames reach the OLT system via one or more passive optical splitters that couple the emulated ONU platform and a set of real ONUs to the OLT system. The emulated ONU platform also receives downstream GPON frames from the OLT system.

Abstract: Methods and systems for decoding a signal include compensating for impairments in a received signal using at least carrier phase estimation, where residual phase error remains after compensation; calculating symbol log-likelihood ratios (LLRs) for symbols in the compensated signal using Monte Carlo integration; demapping the symbols in the compensated signal using the symbol LLRs and extrinsic information from signal decoding to produce one or more estimated codewords; and decoding each estimated codeword with a decoder that generates a decoded codeword and extrinsic information.

Abstract: A method of statistical sharing in an optical communications network is disclosed. The method includes identifying a peak transmission rate and a base transmission rate for each of a plurality of client interface cards of an optical node. The method further includes provisioning a set of universal transceivers of a plurality of universal transceivers for a particular client interface card of the plurality of client interface cards such that the combined bandwidth of the set of universal transceivers is greater than or equal to the base transmission rate of the particular client interface card. The method also includes reserving one or more shared universal transceivers of the plurality of universal transceivers for the particular client interface card, when a transmission rate of the particular client interface card exceeds the base transmission rate of the particular client interface card.

Abstract: A light transmitter transmits multiple light packets, each formatted to include a same message comprising a series of bits, each bit represented as light that is intensity modulated over a bit period at a frequency indicative of the bit. The light packets are transmitted at different start-times to establish different phases, one for each of the light packets, to permit a light receiver to sample each message at a different phase of a fixed sample timeline that is asynchronous to the bit period and the frequency. The light receiver samples the multiple light packets based on the sample timeline, to sample each received message at one of the different sample phases, then constructs a best series of bits based on the multiple demodulated messages.

Abstract: Optical Transport Network (OTN) High Order (HO) mapping systems and methods utilize pointer processing to map one HO signal into another similarly sized HO signal. An OTN HO mapping method and circuit include receiving a first HO signal at a first rate, asynchronously mapping the first HO signal into a second HO signal at a second rate, wherein the first rate and the second rate are substantially similar, translating a portion of overhead from the first HO signal to overhead of the second HO signal, utilizing pointers in the overhead of the second HO signal for frame alignment of the first HO signal, and transmitting the second HO signal containing the first HO signal.

Abstract: Exemplary embodiments of the invention relates to an optical transceiver module having a diagnostic assembly, wherein the diagnostic assembly is configured to visually display the operational status of the transceiver transmitter and receiver components while optically transmitting diagnostic information. The transceiver operational status is accessible while the transceiver operates in conjunction with an external host and may be ascertained in real time without interrupting normal transceiver operation or suspending the transmission of data over optical fibers.

Abstract: Compensation for in-phase (I) and quadrature (Q) timing skew and offset in an optical signal may be achieved based on the correlation between derivatives of I and Q samples in the optical signal. The magnitude of the correlation between derivatives is measured to determine the presence of skew. Correlation between derivatives may be coupled with frequency offset information and/or with trials having additional positive and negative skew to determine presence of skew. Correlations are determined according to pre-defined time periods to provide for continued tracking and compensation for timing skew that may result from, for example, thermal drift.

Abstract: An intelligent optical module to restart itself according to a command sent from the host system is disclosed. The optical module may distinguish the first state, where no optical signal is received, from the second state, where a substantial optical signal but unmodulated is received. The optical module is restarted when the second state appears with a preset pattern.

Abstract: A method of distinguishing a wavelength-dependent reflective element (HRD) from wavelength-independent events in an optical network, the reflective element (HRD) being highly-reflective at a first predetermined wavelength (?1) and significantly less reflective at least one other predetermined wavelength (?2), comprising the steps of: connecting the wavelength-dependent reflective element (HRD) to said optical path at a first position, and, using an optical time domain reflectometer (22) connected to said optical path at a position remote from said reflective element, launching into said optical path light at said first wavelength (?1) and at said second wavelength (?2), detecting corresponding backreflected light from said optical paths and obtaining therefrom first and second OTDR traces (OTDR-?1, OTDR-?2) corresponding to said first (?1) and second (?2) wavelengths, respectively, of detected backreflected light as a function of optical distance from said point; comparing the first and second OTDR traces to

Abstract: A computer device may include logic configured to receive a selection of a start node and an end node in an optical network and obtain network topology information relating to the optical network. The logic may be further configured to determine link latencies for particular links in the optical network; determine a least latency path between the start node and the end node based on the obtained network topology information and the determined link latencies, and wherein the least latency path includes one or more of the particular links; determine one or more alternate paths to the determined least latency path; determine channel availability for the least latency path and the one or more alternate paths; and generate a user interface that relates the least latency path and the one or more alternate paths to the determined channel availability.

Abstract: An optical communication system supporting detection and communication networks. A communication network transmission path and the detection network transmission path are provided as separate paths established by separate fibers or fiber pairs of the same optical fiber cable. All of the elements coupled to the communication network transmission path and the detection network transmission path may be powered by the same power feed equipment through the same optical fiber cable power conductor.

Abstract: In one example embodiment, an optoelectronic communications assembly having an optical receiver or an optical transmitter includes an optical interface disposed at an end thereof and through which optical signals are communicated by the optical receiver or optical transmitter. The optoelectronic communications assembly also includes an electronic component and a first electrical interface disposed at the optical interface end of the optical communications assembly and communicatively coupled to the electronic component.

Abstract: The invention provides an optoelectronic processing apparatus and methods for processing constraint information. The optoelectronic processing apparatus is applied to the optical transport network OTN device, and comprises: a 3R regeneration unit for reamplifying, reshaping and retiming a signal; a wavelength conversion unit for performing wavelength conversion to the signal; an interlayer adapting unit for converting the signal between the OCh layer and the ODUk layer; and a dispatching unit for dispatching the 3R regeneration unit, the wavelength conversion unit and the interlayer adapting unit according to a function identification parameter of the optoelectronic processing apparatus so as to process the signal. By the present invention, the management of the OTN device is simplified, and the 3R regeneration, wavelength conversion and optoelectronic interlayer adaptation information are managed uniformly.

Abstract: A method and system for adaptive quantum information processing can be provided by determining a state of a quantum channel governing an environment with a tomography module. Next a scope of the quantum channel can be calculated with a scope algorithm module. Finally, an optimization module can be utilized to optimize the way to quantum mechanically represent information to be transmitted through the quantum channel based on the scope.

Abstract: In an optical communication network that includes a plurality of interconnected network nodes, a method includes storing in each network node one or more cross-talk margins of respective communication channels that traverse the node. A potential communication channel that traverses a subset of the nodes in the network is identified. A quality of the potential communication channel is evaluated by processing the cross-talk margins stored in the nodes in the subset.

Abstract: A universal optical receiver may include an optical channel monitor configured to acquire spectral data for an optical signal on at least one selected optical channel, a tunable local oscillator configured to be tuned to a center frequency of the optical signal on the at least one selected optical channel, a storage device configured to store data associated with the optical signal responsive to acquisition of the spectral data and tuning of the tunable local oscillator, and processing circuitry configured to execute an algorithm that employs a plurality of binary distinctions based on physical characteristics of the optical signal and employs at least one calculation of figure of merit associated with a series of parameter values of the optical signal to identify a format of the optical signal.

Abstract: A receiving device includes: an amplification fiber configured to include properties to amplify signal light when pumping light is supplied to the amplification fiber and to attenuate the signal light when the pumping light is stopped supplying to the amplification fiber; a receiver configured to receive the signal light output from the amplification fiber; a pumping light source configured to supply the pumping light to the amplification fiber; and a controller configured to control supplying and stopping of the pumping light from the pumping light source to the amplification fiber, so that a level of the signal light input to the receiver is contained within a dynamic range of the receiver.

Abstract: In one embodiment, a one-way delay is measured between optical devices in an optical transport network based on roundtrip times of request and corresponding response frames. A first optical device sends a sequence of delay measurement request frames to a second optical device, which varies a local delay before responding to a request frame, thus causing a slippage in the sequence of reply frames received by the first device. The point at which the request frames are received in relation to the stream of frames sent by the optical device can be identified based on the frame slippage. Therefore, the delay measurement can be adjusted by a corresponding offset to the beginning of a frame in order to increase the accuracy of the one-way delay measurement.

Abstract: The invention provides a system and method for measuring optical signal-to-noise-ratio (OSNR) in an optical communication system. A channel filter is adapted to select one specific optical communication channel from a wavelength-division-multiplexing (WDM) optical communication system, wherein the channel comprises an optical signal carrying digital bit information and noise from associated optical power amplifiers in the system. At least one optical delay interferometer is adapted to measure at least two interferograms of the noisy signal. The invention provides a mechanism for calculating the in-band OSNR from extinctions of the interferograms measured at different optical delays by referring to each other, wherein said optical delays are selected to be substantially less than a bit period of the optical channel.

Abstract: There is provided an optical transmitting device including a detector to detect a transmission rate of a transmission signal, a transmission method selector to determine a transmission method of the transmission signal, based on the transmission rate detected by the detector, a modulation signal generator circuit to generate a modulation signal from the transmission signal, based on the transmission method determined by the transmission method selector, and an optical modulator to generate a modulated optical signal from the modulation signal generated by the modulation signal generator circuit.

Abstract: Consistent with the present disclosure, based on system requirements or in response to an increase in optical signal-to-noise level of an optical channel, such as a WDM channel, additional FEC bits are inserted into and replace selected data payload bits in each frame carried by the channel. The replaced data payload bits may then be transmitted in subsequent frames on the same channel. As a result, the transmitted frames have a reduced data payload rate, but a higher coding gain. Alternatively, the replaced data payload bits may be included in frames transmitted on another optical channel. In that case, the frames carried by the two channels typically have the same bit length or number of bits and may thus be compliant with the frame length requirements of G.709, for example. Preferably, the number of coding bits may be changed dynamically to obtain different coding gains.

Abstract: An OSNR monitor device includes an optical receiver including a delay interferometer which inputs an optical signal in accordance with a given bandwidth and outputs two optical signals and causes the optical signals to interfere with each other and optical detectors which outputs currents in accordance with optical powers of the optical signals output from the interferometer, an optical power monitor configured to obtain the optical powers of the optical signals received by the optical detectors included in the optical receiver, and an OSNR calculator configured to calculate an optical signal-to-noise ratio in accordance with the optical powers obtained from the optical power monitor and the reception bandwidth.

Abstract: Optical fiber-based wireless systems and related components and methods are disclosed. The systems support radio frequency (RF) communications with clients over optical fiber, including Radio-over-Fiber (RoF) communications. The systems may be provided as part of an indoor distributed antenna system (IDAS) to provide wireless communication services to clients inside a building or other facility. The communications can be distributed between a head end unit (HEU) that receives carrier signals from one or more service or carrier providers and converts the signals to RoF signals for distribution over optical fibers to end points, which may be remote antenna units (RAUs). A microprocessor-based control system or systems may also be employed.

Abstract: A computerized system and method for managing a passive optical network (PON) is disclosed. The system includes a detection and analysis module adapted for receiving uploaded measurement data from an optical line terminal (OLT) and at least one optical network terminal (ONT), and at least one of technical tools data, service failure data, and outside plant data. The detection and analysis module is adapted for determining a source of failure or potential failure in the PON by correlating the uploaded measurement data and the at least one of technical tools data and service failure data with information stored in a memory medium for the OLT and each ONT.

Abstract: In accordance with an embodiment of the present disclosure a method for adaptively spacing channels of an optical network comprises determining a first desired power level of a first channel of an optical network. The method further comprises determining a second desired power level of a second channel of the optical network, the second desired power level being less than the first desired power level. Additionally, the method comprises determining a first spectral space between the first channel and one or more channels neighboring the first channel based at least on the first desired power level. The method also comprises determining a second spectral space between the second channel and one or more channels neighboring the second channel based at least on the second desired power level, the second spectral space less than the first spectral space.

Abstract: A receiver receives a predetermined pattern over an optical link from a transmitter. In response to detecting that the predetermined pattern satisfies at least one criterion, indicating that a synchronization point has been reached to allow link training of the optical link to be performed between the transmitter and receiver.

Abstract: One embodiment provides a system for controlling flow rate in an EPON. The system includes an OLT, an ONUs coupled to the OLT via a passive optical splitter, a switch coupled to a port located on the ONU, and a flow-control mechanism. The ONU includes one or more queues corresponding to one or more classes of Services, and one or more ports. The switch includes a plurality of UNI ports, and the switch is configured to switch one or more upstream traffic flows belonging to the one or more classes of services from the plurality of UNI ports. The flow-control mechanism is configured to set a flow rate of an upstream traffic flow of certain class of service originated from a UNI port. The flow-control mechanism sets the flow rate based on status of an ONU queue corresponding to the class of service of the upstream traffic flow.

Abstract: A computer system and method for transmitting LAN signals over transport systems. LAN signals are generated in any client LAN compliant interface. A transceiver receives the client LAN signal in the LAN format. The client LAN signals are not converted to a SONET transmission format at any time before reaching the transceiver. The transceiver then converts the client LAN signal to an internal electrical LAN signal before re-clocking the internal electrical LAN signal. The re-clocked internal electrical LAN signal is then re-modulated into a second LAN signal. The second LAN signal is then transmitted to a transport system.

Abstract: A transmitter for a communications link is tested by using a (software) simulation of a reference channel and/or a reference receiver to test the transmitter. In one embodiment for optical fiber communications links, a data test pattern is applied to the transmitter under test and the resulting optical output is captured, for example by a sampling oscilloscope. The captured waveform is subsequently processed by the software simulation, in order to simulate propagation of the optical signal through the reference channel and/or reference receiver. A performance metric for the transmitter is calculated based on the processed waveform.

Abstract: An optical receiving apparatus includes: a compensator configured to compensate an amount of change in a characteristic; a controller configured to obtain, based on a first amount of change in the characteristic with respect to a first optical signal with a first wavelength, the first wavelength, and a wavelength characteristic in the characteristic, a second amount of change in the characteristic made when a second optical signal with a second wavelength is propagated in an optical path, the second wavelength being different from the first wavelength, and obtain a compensation amount based on the second amount of change; and a first setting unit configured to set the compensation amount for the compensator so that the compensator compensates the amount of change in the characteristic.

Abstract: The present disclosure relates to the field of network communication and particularly discloses a method for monitoring performance of a wavelength path. The method includes: receiving, by a second node, a path request message of a wavelength path from an upstream neighboring node, where the path request message includes at least a path identifier of the wavelength path and second wavelength identifier information; obtaining, by the second node, a wavelength identifier according to the second wavelength identifier information, and recording a mapping relationship between the wavelength path and the wavelength identifier; and determining, by the second node according to the wavelength identifier, a low frequency signal modulated at a working wavelength of the wavelength path, and obtaining performance of the wavelength path by monitoring the low frequency signal. A system for monitoring performance of a wavelength path and a node device are also disclosed in embodiments of the present disclosure.

Abstract: Digital timing error detection systems and techniques are described. The described techniques are independent of polarization and differential-group-delay and are used to perform timing recovery of polarization-multiplexed coherent optical systems.

Abstract: A method for extracting admin information from a modulated optical signal. A coherent optical receiver receives the modulated optical signal, where a nominal carrier frequency of the modulated optical signal was modulated using a first slow frequency and second slow frequency associated with an electronic admin signal. The receiver converts the modulated optical signal to an electronic signal, and estimates estimating a plurality of carrier phases of the electronic signal. The receiver determines a plurality of offset values by calculating the time derivative of at least some of the estimated carrier phases, wherein each of the plurality of offset values are proportional to an associated frequency offset component, and the frequency of each offset value corresponds to the first slow frequency or the second slow frequency. The receiver extracts information corresponding to the electronic admin signal using the determined plurality of offset values.

Abstract: A coherent optical receiver measures a portion of a spectra of a multi-channel optical signal that includes at least one signal adjacent to a selected signal. The coherent optical receiver determines structure and bandwidth information for the measured portion of spectra, and determines one or more filter parameters for the selected signal based on the structure and bandwidth information of the at least one signal adjacent to the selected signal. The coherent optical receiver adjusts one or more active filter parameters of a carrier phase estimator in the optical coherent receiver to have values corresponding to the determined one or more filter parameters.

Abstract: Techniques are disclosed that relate to synchronizing a clock on a network interface device with a clock on an optical line terminal (OLT). In one example, the technique to synchronizing the clocks may include monitoring one or more instances when the network interface device transmits information to the OLT and determining when a frame should be received by the network interface device based on the monitored one or more instances when the network interface device transmits information the OLT.

Abstract: An optical transmitter includes: a modulator; an output light monitoring unit; and a control unit. The modulator includes a dividing unit dividing light inputted to the modulator into first and second branch lights; first and second modulation units performing phase modulation for the first and second branch lights, respectively; a rotator which rotates the polarization plane of one of the first and second modulated lights; and a polarization combining unit combining the first and second modulated lights. The output light monitoring unit monitors light intensity of the output of the polarization combining unit. The control unit controls at least one of the first and second modulation units, on the basis of a monitoring result by the output light monitoring unit. The control includes a light intensity control making the light intensity of the first and/or second modulated light smaller than a maximum value of a modulation curve light intensity.

Abstract: A scheduling method, apparatus, and system for avoiding a dual-end monitoring conflict for a submarine cable optical line are provided, where the method includes: sending a wavelength occupation request message to a peer-end equipment via a selected submarine cable optical line to be monitored, and receiving a wavelength occupation response message returned by the peer-end equipment; parsing the wavelength occupation response message to determine whether a requested wavelength is occupied by the peer-end equipment; and if the requested wavelength is occupied by the peer-end equipment and the wavelength can be switched, monitoring the selected submarine cable optical line to be monitored by using another wavelength after switching; and if the requested wavelength is not occupied by the peer-end equipment, monitoring the selected submarine cable optical line to be monitored by using the requested wavelength.

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: A router comprising an interface module (IM), having an optical path and an electrical path and a speed sensor coupled between an input of the router and an input of the IM. The speed sensor is adapted to receive a packet and detect a speed of the IM connection and in response to the speed of the IM connection being above a threshold value, the speed sensor provides the packet to the optical path of the IM and in response to the relative speed being below the threshold value, the speed sensor provides the packet to the electrical path of the IM.