Abstract: Signal format conversion apparatus and methods involve converting data signals between a first signal format associated with a first reference clock rate and a second signal format that is different from the first signal format and is associated with a second reference clock rate different from the first reference clock rate. A period of the second signal format is changed to match a period of a third signal format by controlling a synchronized second reference clock rate that is applied in converting data signals between the first signal format and the second signal format. The synchronized second reference clock rate is different from the second reference clock rate and is synchronized with a third reference clock rate. The third reference clock rate is associated with the third signal format. Such synchronization simplifies conversion of signals between the second and third signal formats.

Abstract: A synchronous optical signal generation device includes: an optical phase detector that compares the phase of a reference optical signal with a phase of an optical beat signal to generate a phase error signal; a shaping mechanism that shapes the phase error signal; and a voltage controlled optical signal generator that generates an optical beat signal based on the shaped phase error signal and that outputs the optical beat signal while feeding the optical beat signal back to the phase detector.

Abstract: In an access network using optical switches, communications between an OLT and ONUs are established without a photoelectric conversion performed at an optical switching unit. The OLT controls the downlink optical switch SW(DOWN) to sequentially select each ONU in slots arranged in a discrete manner, and transmits a Discovery Gate message. Upon receipt of the Discovery Gate message, each ONU consecutively transmits Register Request messages. The uplink optical switch SW(UP) sequentially switch signals from ONU#1 through ONU#128 in the slots arranged in a discrete manner, and outputs the signals to the OLT, Some of the Register Requests transmitted from the respective ONUs pass through the SW(UP), and reach the OLT. Based on the received Register Requests, the OLT determines the timing of transmission for the ONUS, and notifies the ONUS of the timing of transmission through a Gate message.

Abstract: A phase detection and decision feedback equalization circuit is provided. A first latch and a second latch are coupled to an input of the circuit. A third latch and a fourth latch are respectively coupled in series to outputs of the first latch and second latch. The first and fourth latches are enabled by a clock signal, and the second and third latches are enabled by a complement of the clock signal. A first feedback circuit is configured to provide a signal output from the first latch and a first feedback signal derived from the output of the fourth latch to an input of the third latch. A second feedback circuit is configured to provide a signal output from the second latch and a second feedback signal derived from the output of the third latch to an input of the fourth latch.

Abstract: A method and system for a estimating a most likely location of a periodic SYNC burst within an optical signal received through an optical communications system. A cross-correlation is calculated between a multi-bit digital signal derived from the optical signal and a known symbol sequence of the SYNC burst. The cross-correlation is logically partitioned into sub-blocks. A candidate sub-block in which the SYCN burs is mot likely located is identified, and analysed to estimate a location of the SYNC burst.

Abstract: A method and apparatus for sending timing information using an optical signal. A first electrical signal comprising a pseudorandom binary sequence is generated. The first electrical signal comprising the pseudorandom binary sequence is modulated with a second electrical signal to form a modulated electrical signal. The second electrical signal includes timing data in a format used for global positioning systems. An optical carrier signal is modulated with the modulated electrical signal to form the optical signal using an optical transmitter.

Abstract: A network device includes a substitutor and a transmitter. The substitutor receives input columns of concurrently received input symbols. Each of the input columns includes one input symbol from each of a plurality of parallel input lanes. The substitutor generates output columns corresponding to the input columns, wherein each of the output columns includes one output symbol for each of a plurality of parallel output lanes. The substitutor replaces the output symbols of a selected column of the output columns with alignment symbols. The selected column is immediately followed by a second column, and the second column is immediately followed by a third column. The substitutor replaces the output symbols of the second column with disposable symbols, and replaces the output symbols of the third column with boundary symbols. The transmitter drives data onto a communications medium in response to the output symbols generated by the substitutor module.

Abstract: The embodiments of the present invention pertaining to a method for distributing time between a first and a second Synchronous Ethernet “SyncE” domain, said first and second domains being interconnected by a third, Synchronous Optical Networking/Synchronous Digital Hierarchy “SDH-SONET” domain in which a time-associated reference parameter is distributed, through Synchronous Ethernet “SyncE” domains, by means of at least one additional Type Length Value “TLV” field of an Ethernet Synchronization Messaging Channel “ESMC” message and a corresponding time-associated reference parameter is distributed, through the Synchronous Optical Networking/Synchronous Digital Hierarchy “SONET-SDH” domain by means of at least one additional Type Length Value “TLV” field within a message of the IEEE 1588 V2 protocol.

Abstract: A system and method for regenerating a client clock signal for use in optical communications is disclosed. The system and method involves using a carrier clock signal and a client clock signal to calculate quantities of data that are received and transmitted at an edge node and then adjusting a clock source in response to the difference between the calculated quantities of received and transmitted data.

Abstract: Disclosed by way of exemplary embodiments, a 40/50/10 Gb/s Optical Transceivers/transponders which use opto-electronic components at data rates collectively that are lower than or equal to half the data rate, using two optical duobinary carriers. More specifically, the exemplary embodiments of the disclosed optical transceivers/transponders relate to a 43 Gb/s 300 pin MSA and a 43˜56 Gb/s CFP MSA module, both include a two-carrier optical transceiver and the appropriate hardware architecture and MSA standard interfaces. The two-carrier optical transceiver is composed of a pair of 10 Gb/s optical transmitters, each using band-limited duobinary modulation at 20˜28 Gb/s. The wavelength channel spacing can be as little as 19˜25 GHz. The same principle is applied to a 100 Gb/s CFP module, which is composed of four tunable 10 Gb/s optical transmitters, with the channel spacing between optical carriers up to a few nanometers.

Abstract: I/Q data skew in a QPSK modulator may be detected by sending identical or complementary data streams to I and Q channel PSK modulators, setting the relative carrier phase between I and Q to zero or ?, and monitoring the average QPSK output power, where the data streams sent to the I and Q channels include pseudorandom streams of ones and zeroes.

Abstract: In one example embodiment, an optoelectronic module includes an optical receiver and a post-amplifier. The optical receiver is configured to receive an optical signal and generate an electrical data signal corresponding to the optical signal. The post-amplifier is electrically connected to the optical receiver and is configured to amplify the electrical data signal. The optoelectronic module further includes means for quantifying a quality of the optical signal from which the amplified electrical data signal is derived.

Abstract: The subject matter disclosed herein relates to synchronizing network timing. In one particular example, network timing may be synchronized using reflected signals.

Abstract: A method of synchronizing with a data transmission in a passive optical network, wherein the data transmission includes a plurality of data transmission frames each having i) a known transmission duration, and ii) a start boundary identified by a predetermined synchronization pattern. The method includes comparing a plurality of data patterns within the data transmission to at least part of a predetermined synchronization pattern; providing a comparison result for each comparison having a match between a data pattern and the at least part of the predetermined synchronization pattern; assigning a frame tracking signal to each one of the plurality of comparison results occurring within the known transmission duration; comparing one or more subsequent data patterns occurring in the data transmission to at least part of the predetermined synchronization pattern for each assigned frame tracking signal; and generating a synchronization signal associated with a selected one of the frame tracking signals.

Abstract: An optical receiver, within a first device, may receive first configuration information from an optical transmitter, also within the first device. While receiving the first configuration information, the optical receiver may operate according to a clock. Later, the optical receiver may receive optical data from a second device according to the first configuration. While receiving the optical data from the second device, the optical receiver does not operate according to the clock, wherein the optical receiver not operating according to the clock allows the optical receiver to receive the optical data with greater sensitivity.

Abstract: Provided is an optical access system, including: an optical line terminal, a plurality of optical network units and an optical switching unit. The optical line terminal sends to the optical switching unit a control frame including a switching time when the optical switching unit is to make a switch from one of the optical communication paths between the optical line terminal and the plurality of optical network units to another, and an identifier of an optical communication path to which the switch is made in order to switch the optical communication paths between the optical line terminal and the plurality of optical network units. The optical switching unit switches the optical communication paths between the optical line terminal and the plurality of optical network units based on the switching time and the identifier of the optical communication path after switching which are included in the control frame.

Abstract: A frame transmitting unit divides a payload area of an upper-layer frame into a plurality of slots, maps a lower-layer frame to one or more of the slots, and transmits the upper-layer frame including connection information that indicates which one or more of the slots the lower-layer frame of a same type is mapped to. The frame synchronization detection unit identifies, as one or more allocated slots, the one or more slots to which the lower-layer frame of the same type is mapped, on the basis of the connection information, and detects the frame synchronization by identifying a frame head signal of the lower-layer frame of the same type that is mapped to the one or more allocated slots.

Abstract: An optical sensor system comprises one or more optical sensor devices, a master device and an electrical bus connecting the sensor devices to the master device. The bus comprises a signal daisy chain for the transmission of synchronization events. The sensor devices are adapted to detect a synchronization event at a signal input terminal, to time an optical activity based on this synchronization event and to provide at a signal output terminal a synchronization event delayed by an offset time with respect to the detected synchronization event. A property of the synchronization events provided by the sensor devices is indicative of an output value of the respective sensor device, corresponding to a state of an optical section to which the sensor is sensitive.

Abstract: An optical receiver comprising a frame detector configured to receive a polarized signal comprising a first bit stream and a second bit stream, and further configured to identify a plurality of frames in the first bit stream and the second bit stream using a composite header, and a time-domain equalizer (TDEQ) configured to separate the first bit stream and the second bit stream using a portion of the composite header.

Abstract: To reduce emission of an unintentional electromagnetic wave even if a frequency of a clock signal being output is high, a printed circuit board (10) includes: a substrate (101); signal output circuits (102 and 103) formed on the substrate (101), for outputting a clock signal; power supply wirings (109 and 110) for connecting the signal output circuits (102 and 103) and a power source; and trap filters (107 and 108) provided to the power supply wirings (109 and 110), for attenuating a frequency component corresponding to a frequency of the clock signal.

Abstract: A circuit for end-of-burst detection in a portion of a received bit stream is disclosed. The circuit comprises: a first counter for counting the number of bits in the portion, a second counter for counting the number of bit value transitions in the portion, and a circuit for comparing the counted number of bits in the portion and the counted number of bit value transitions therein with preset values, the circuit for comparing is further arranged for generating a signal indicative of end-of-burst detection based on the result of the comparison.

Abstract: A method and apparatus for allocating resources of a Visible Light Communication (VLC) terminal in a VLC system. The VLC terminal receives a beacon message from a base station, coordinates time synchronization with the base station, searches for an available wavelength channel, constructs available wavelength channel information, and transmits an initial access request using a basic time slot channel and a basic wavelength channel. The base station considers the available wavelength channel information and a current channel allocation condition, allocates an appropriate channel, and transmits channel allocation information to the VLC terminal. The VLC terminal and the base station communicate data with each other using an allocated time slot channel included in the channel allocation information and an allocated wavelength channel included in the channel allocation information.

Abstract: An apparatus comprising a data framer configured to frame a data stream into a plurality of frames each comprising a plurality of fields sized to align the frames with a word boundary greater than or equal to about four bytes long, and an optical transmitter coupled to the data framer and configured to transmit the frames. Included is an apparatus comprising at least one component configured to implement a method comprising encapsulating a data stream with at least one Gigabit Passive Optical Network (GPON) Encapsulation Method (GEM) payload aligned with a word boundary at least about four bytes long, encapsulating the GEM payload with a GPON Transmission Convergence (GTC) frame aligned with the word boundary, and transmitting the GTC frame.

Abstract: A light transmission system has a light transmission module having a light transmission path that transmits a data signal as an optical signal, wherein the light transmission module converts the optical signal transmitted through the light transmission path to an electrical signal and outputs the converted optical signal as a binarization signal, an electrical transmission path that outputs a clock signal as a binarization signal, a reception processing unit that performs a reception process on each of the data signal and the clock signal, and a first delay unit that delays a rise start time of the clock signal with respect to a rise start time of the data signal for the binarization signal. A delay amount of the clock signal by the first delay unit is a time less than or equal to a maximum value of a data dependency jitter (DDJ).

Abstract: A quantum communication system comprising a receiver and a plurality of transmitters, said receiver comprising a detector sub-system, each of said transmitters being configured to emit pulses of radiation, said detector subsystem comprising at least one detector, said detector being configured to detect said light pulses, the system comprising a timing control module, said timing control module being configured to control the number of light pulses received by the detector sub-system, such that just one light pulse from one transmitter reaches the detector sub-system at any one time, the timing control module also allowing the transmitter which sent said pulse to be identified.

Abstract: The present invention relates to a system and method that enable transmission of multiple data packet lines as an optical time-division multiplexed signal. The invention provides a method and system that can synchronize data packet signals to a clock and convert them into return-to-zero signals. When multiple data packet lines are converted, they can be multiplexed together and transmitted according to well-known methods.

Abstract: According to particular embodiments, a signal communicated from a transmitter to a receiver is received. A frequency offset estimate of the signal is determined. The frequency offset estimate indicates a frequency difference between the transmitter and the receiver. The frequency offset estimate is provided as feedback. A next frequency offset is compensated for according to the feedback.

Abstract: A time synchronization method and a time synchronization device in a passive optical network (PON), and a PON are provided. The method includes receiving a synchronization packet sent after time synchronization of an optical line terminal (OLT) with a master clock (MC) is achieved, wherein the synchronization packet carries a timestamp TMt1i determined after the time synchronization of the OLT is achieved, adjusting a local clock according to the timestamp to achieve time synchronization of an optical network unit/optical network terminal (ONU/ONT) with the OLT, and after the time synchronization of the OLT is achieved, instructing an slave clock (SC) to perform time synchronization. A time synchronization device and a time synchronization system for implementing the method in a PON are further provided.

Abstract: Erroneous data due to faults are prevented from propagating through a distributed network node having diversely routed communications links by using a fault masking technique that eliminates the 60 ms of error propagation time associated with SONET networks. The fault masking technique can also prevent random bit errors from propagating through the distributed network node. A frame alignment technique used in the network node is scalable for very wide words (e.g., 128 bits) for use with high speed optical communications protocols, such as OC-192.

Abstract: It is necessary to completely remove the overlapping of signals between plural PONs in order to make the PONs coexist. Accordingly, it is required to share or intensively manage bandwidth use conditions over an optical fiber that serves as a common band between plural systems. Therefore, transmission clocks should be synchronized with high accuracy between the plural systems. A reference clock is provided from an external device or a representative OLT to the entire systems to perform clock synchronization between the plural systems, so that the overall systems are synchronized by synchronizing each OLT with the reference clock. A hierarchical management method is selected that manages ONUs under the control of each OLT by managing band use information arranged for each OLT with respect to an external device or a representative OLT for sharing of bandwidth use conditions between plural systems.

Abstract: A first header-attaching unit attaches to data of a low speed bit rate A, a header of the bit rate A. A second header-attaching unit attaches the header of the bit rate A to data of a high speed bit rate B. A combining unit combines outputs of the first and the second header-attaching units. A low speed scrambling unit performs a scrambling process on combined data by using a clock corresponding to the bit rate A. A high speed scrambling unit performs a scrambling process on the data of the bit rate B by using a clock corresponding to the bit rate B. During a timing corresponding to the bit rate A in the frame, a selector selects an output of the low speed scrambling unit. During a timing corresponding to the bit rate B in the frame, the selector selects an output of the high speed scrambling unit.

Abstract: In one embodiment, a method includes receiving a first input stream, generating a first clock, sampling the first input stream based on the first clock, detecting a first phase difference between the first input stream and the first clock to generate a clock-correction signal and a first select signal, and generating a first recovered stream based on the first select signal. The method may additionally include receiving a second input stream, generating a second clock, sampling the second input stream based on the second clock, detecting a second phase difference between the second input stream and the second clock to generate a clock-correction signal and a second select signal, and generating a second recovered stream based on the second select signal. The method may further include adjusting the clocks based on the first and second clock-correction signals and combining the first and second recovered data streams to generate an output.

Abstract: A system and method implementing dual stage carrier phase estimation (CPE) in a coherent receiver for an optical fiber communication system. In the first stage, a feed-forward CPE is implemented to make an initial carrier phase estimation of a training sequence. The initial carrier phase estimation is coupled to the second stage which implements a decision-feedback CPE. After a training period, accurate bit decision for system traffic can be achieved using the decision-feedback CPE.

Abstract: The invention relates to a device for regenerating the phase of an optically modulated signal with phase changes and based on two and three replicas, wherein the replicas refer to the number of identical signals that are obtained form the input signal. This regenerator is capable of regenerating the phase and period of any format of modulation of optical communications systems which are differential modulation with phase changes, such as: DISK, DQPSK, RZ-DQPSK, RZ-DQPSK, D8PSK, D8PSK, RZ-D16PSK, D16PSK. The regenerator design presented involves the regenerator being placed alter the multiplexer of a communications system and before the signal modulators and/or decoders. Thus the regenerator receives the signal leaving the multiplexer and this signal is input in an amplitude modulator.

Abstract: A signal transmitting device includes a transmitter, a receiver, and four optical fibers. The transmitter includes a first electro-optical converter electro-optically converting original electrical red video signal into optical red video signal in original video signal, a second electro-optical converter electro-optically converting original electrical green video signal into optical green video signal a third electro-optical converter electro-optically converting original electrical blue video signal into optical blue video signal, a parallel/serial converter converting original electrical parallel signal having a lower transfer rate than a transfer rate of the original video signal into original electrical serial signal, and a fourth electro-optical converter electro-optically converting the original electrical serial signal transmitted from the parallel/serial converter into optical serial signal.

Abstract: The present invention is directed to realize a stable and highly-efficient quantum communication without being influenced by the jitter of the heralding signal. In regard to the quantum encryption transmitting apparatus 200, the pulse-driven heralded single-photon source 201 generates a photon pair, outputs one photon of the photon pair, and outputs the other photon of the photon pair as a heralding signal. The timing adjuster 202 synchronizes the heralding signal with a clock signal for pulse driving the pulse-driven heralded single-photon source 201, and outputs as a trigger signal. The quantum communication modulating unit 203 implements the signal modulation to a quantum signal, in timing with the trigger signal, and transmits the quantum signal to the quantum encryption receiving apparatus 300 via the quantum communication path 101. The heralding signal transmitting unit 205 transmits the heralding signal to the quantum encryption receiving apparatus 300 via the heralding signal communication path 102.

Abstract: Disclosed are a digital equalization apparatus for a coherent optical receiver and a digital equalization method for a coherent optical receiver, capable of compensating for chromatic dispersion and polarization impairment through a digital signal processing, and capable of performing a clock recovery and a data recovery through a digital symbol synchronization. The digital equalization apparatus and the method compensate for various impairments occurring on an optical path in a digital manner and achieve synchronization through a simple structure.

Abstract: The present disclosure provides Network Element (NE) clock synchronization using Optical Transport Network (OTN) delay measurement systems and methods such as described in ITU-T G.709 (12/2009) “Interfaces for the Optical Transport Network (OTN)” and G.798 (10/2010) “Characteristics of optical transport network hierarchy equipment functional blocks”. OTN provides a Delay Measurement (DM) function to measure fiber path latency between two network elements to within microsecond accuracy. The convergence of packet switching and OTN transport into the same network element allows the sharing of this information between the two applications. The OTN delay measurement value can be used to synchronize two network element clocks to within microsecond accuracy without the need for a costly GPS synchronization solution or reduced accuracy NTP solutions.

Abstract: In a WDM-PON system wherein a plurality of ONUs transfer signals by sharing wavelengths, one wavelength dedicated to a ranging procedure is set, and the ranging is performed with only the dedicated wavelength, so as to measure reciprocating delay times. At the other wavelengths, transmission signals from a plurality of ONUs are transferred in time division multiplexing based on the obtained reciprocating delay times. An OLT includes a burst receiver circuit for only the wavelength dedicated to the ranging, and subsequently to the ranging, the OLT adjusts transmission amplitudes and transmission phases for the ONUs, so as to equalize received amplitudes and received phases in the OLT. For this purpose, the OLT includes means for measuring the amplitudes and phases of received signals, as the burst receiver circuit, and it includes a table for managing the received amplitudes and received phases of the respective ONUs.

Abstract: An optical transport system has an optical transmitter and an optical receiver coupled to one another via an optical link having a plurality of transmission paths. The optical transmitter uses at least one of the transmission paths to transmit an optical-reference signal that enables the optical receiver to obtain (i) an optical local-oscillator signal that is phase- and frequency-locked to an optical-carrier frequency used by the transmitter for the generation of data-bearing optical signals and (ii) a clock signal that is phase- and frequency-locked to the clock signal used by the transmitter. The optical receiver then uses these signals to demodulate and decode the data-bearing optical signals in a manner that significantly reduces the complexity of digital signal processing compared to that in a comparably performing prior-art system.

Abstract: A system, a Laser-on-CMOS chip, and a method are described herein in accordance with the present invention. In one embodiment, the present invention enables a conventional WDM-capable system to dictate what wavelengths a Laser-on-CMOS chip's optical ports will use by seeding each of their LoC upstream reflective light generation devices (e.g., RSOAs) with a particular wavelength.

Abstract: A transmitter including a plurality of input lanes, a substitutor module, and an interleaver module. The plurality of input lanes is configured to receive input symbols including data symbols and idle symbols, wherein the input symbols are arranged into columns of concurrently received input symbols, and wherein each of the columns includes one input symbol from each of the plurality of input lanes. The substitutor module is configured to, at intervals, replace one of the columns with a column of alignment symbols. The substitutor module is further configured to replace an immediately subsequent one of the columns with a column of disposable symbols; and replace one or more immediately subsequent ones of the columns with columns of boundary symbols uninterrupted by disposable symbols. The interleaver module is configured to interleave symbols from the substitutor module between a first transmit lane and a second transmit lane.

Abstract: A method and apparatus for producing a series of amplified optical pulses from a series of input optical pulses. The method includes creating a set of local optical pulses from a series of input optical pulses, the set of local optical pulses being applied to the input of an optical amplifier and having different amplitudes arranged in a graded order. The set of local optical pulses are amplified by an optical amplifier to have a significantly amplified first local optical pulse that is removed from the set of local optical pulses and output as a part of the series of amplified optical pulses. After removing the significantly amplified first local optical pulse, the set of local optical pulses is recreated by adding a new optical pulse from the series of input optical pulses to the end of the set of local optical pulses; and the recreated set of local optical pulses is routed back to be applied to the input of the optical amplifier to continue producing the series of amplified optical pulses.

Abstract: A method and apparatus for synchronizing time in a Gigabit Passive Optical Network (GPON) in which an Optical Line Terminal (OLT) sends a downstream frame including a Physical Control Block downstream (PCBd) field and a payload field to an Optical Network Unit (ONU); the OLT determines a time value associated with a certain bit in the PCBd field of the downstream frame; and the OLT sends an Operation, Administration and Maintenance (OAM) message defined by a GPON protocol carrying the time value to the ONU, wherein the ONU uses the time value to adjust a local time of the ONU.

Abstract: A system and method for data synchronization in Passive Optical Networks are disclosed. According to an embodiment, the present invention provides a method for providing upstream data synchronization in an optical communication network. The method includes sending data from an Optical Network Unit. The data includes a first data frame, which includes a header sequence, a synchronization segment, and a data segment. The synchronization segment includes 66 bits, which includes a first number of bits having nonzero values and a second number of bits having a value of zero. The first number is different from the second number. The method further includes receiving at least the first data frame by an Optical Line Terminal. The method also includes processing the first data frame. The method additionally includes selecting a first segment of the first data frame, the first segment including 66 bits.

Abstract: An output control unit outputs data of bit rate A to a first header-attaching unit and data of bit rate B to a second header-attaching unit. An instructing unit instructs the first or the second header-attaching unit to attach a header of bit rate being the least bit rate to the data of bit rate A or B. The first header-attaching unit creates a header of bit rate A, including an ID of a destination ONU of the data of bit rate A and information concerning the data length, and attaches the header of bit rate A to the data of bit rate A. The second header-attaching unit creates a header of bit rate A, including an ID of the destination ONU of the data of bit rate B and information concerning the data length, and attaches the header of bit rate A to the data of bit rate B.

Abstract: System and methods are provided, in an Optical Transport Network (OTN), for communicating asynchronous Tributary Slots (TSs) via a synchronous Optical Payload Transport Unit of level k (OTUk) interface. The transmission method accepts a plurality of TSs at a corresponding plurality of asynchronous data rates. The TSs are mapped, using a tangible memory medium, into pseudo-Optical channel Data Tributary Unit (ODTU) frames synchronized to a common clock. Then, the synchronized pseudo-ODTU frames can be interleaved into an OTUk frame, without the need of a phase-locked loop (PLL) or buffering.

Abstract: An apparatus including a data framer and an optical transmitter. The data framer is used to frame a data stream into a plurality of frames, each of the frames includes a plurality of fields sized to align the frames with a word boundary greater than or equal to four bytes long. The optical transmitter is coupled to the data framer and is used to transmit the frames. Included is an apparatus with at least one component for implementing a method for encapsulating a data stream with at least one Gigabit Passive Optical Network (GPON) Encapsulation Method (GEM) payload aligned with a word boundary of at least four bytes long, encapsulating the GEM payload with a GPON Transmission Convergence (GTC) frame aligned with the word boundary, and transmitting the GTC frame.

Abstract: A phase synchronized optical master-slave loop comprises at the slave-end a processor (105) configured to include a first timing signal into a bit stream to be transmitted to the master-end, detect a second timing signal from a bit stream received from the master-end, and calculate a phase difference between a regenerated phase signal and a reference phase signal on the basis of a transmission moment of the first timing signal, a first time-stamp indicating a reception moment of the first timing signal at the master-end, a reception moment of the second timing signal, and a second time-stamp indicating a transmission moment of the second timing signal from the master-end. The processor is configured to read the time stamps from the received bit stream that corresponds to a received light signal according to a reception line-code. Thus, conversion of data format is not necessary for the phase synchronization.

Abstract: A communication system and a timing control method are proposed that optimize timing in a sender and thereby enable information to be stably transmitted at the right timing. Under instructions from a timing controller in a receiver, the timing of driving a phase modulator in a sender is shifted by one step after another, and the then amount of clock shift and result of interference are monitored at the receiver and stored in a memory. The optimum timing is determined based on the stored data. Thus, a clock for driving the phase modulator in the sender can be set at the right timing. This is equivalent to compensating for group velocity dispersion due to wavelength dispersion that occurs when an optical signal channel and a clock signal channel are transmitted by wavelength division multiplexing transmission.