Abstract: Systems and methods for visible light communication are disclosed. In part, illumination devices and related systems and methods are disclosed that can be used for general illumination, lighting control systems, or other applications. The illumination devices synchronize preferentially to the AC mains to produce time division multiplexed channels in which control information can be communicated optically by the same light source that is producing illumination. Such illumination devices preferentially comprise LEDs for producing illumination, transmitting data, detecting ambient light, and receiving data, however, other light sources and detectors can be used. The physical layer can be used with a variety of protocols, such as ZigBee, from the Media ACcess (MAC) layer and higher.

Abstract: Circuits, methods, and apparatus that allow signals that are compliant with multiple standards to share a common connector on an electronic device. An exemplary embodiment of the present invention provides a connector that provides signals compatible with a legacy standard in one mode and a newer standard in another mode.

Abstract: Provided is a clock operating method and apparatus for supporting a plurality of Ethernet physical layer interfaces. To provide a network synchronization function in a board of simultaneously accommodating the plurality of Ethernet physical layer interfaces, the clock operating method may include: determining a physical layer interface according to a current network synchronization mode; and generating a clock signal of the determined physical layer interface as a reference signal of another physical layer interface.

Abstract: Transmitter waveform dispersion penalty (“TWDP”) is decreased in a transmitter. A binary data signal is received for transmission over a channel that exhibits TWDP. The data signal is shifted less than a full clock cycle to generate at least one post cursor signal. The post cursor signal is subtracted from the data signal to generate a transmitter output data signal for transmission over the channel. In addition to decreasing TWDP, data dependent jitter is also reduced for data transmission across a channel that exhibits a multi-pole transmission characteristic. A main data signal and at least one cursor signal, which is shifted at least a portion of a clock period from the main data signal, is generated. The cursor signal is filtered to filter out effects based on the second pole of the multi-pole transmission characteristic. The main data signal is subtracted from the filtered cursor signal to generate the transmitter output data signal.

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: 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 serializer is equipped with a plurality of input terminals into which a plurality of binary signals are input in parallel, and converts the plurality of input binary signals into serial binary signals and transmits the serial binary signals to an optical transmission module. One input terminal out of the plurality of input terminals is assigned as an input terminal for preventing bit continuation by inserting “1” signals or “0” signals into the serial binary signals so that a predetermined number of bits of the same value may not be inserted continuously. Due to this structure, bit continuation can be prevented even for a signal generating source with no coding function by a simple configuration without increasing cost and size.

Abstract: In a coherent optical receiver of an optical communications network, a method of recovering a clock signal from a high speed optical signal received through an optical link. A set of compensation vectors are adaptively computed for compensating Inter-symbol Interference (ISI) due to at least polarization impairments of the optical signal. A channel delay is estimated based on the computed compensation vectors. The estimated channel delay is subtracted from the computed compensation vectors to generate corresponding modified compensation vectors. Finally, the modified compensation vectors are used to derive a recovered clock signal.

Abstract: In the field of optical network communication technologies, a method, a device, and a system for transmitting a constant rate data stream are provided. The method for transmitting the constant rate data stream by the first network device includes: receiving a constant rate data stream; calculating an input rate of the constant rate data stream or a rate difference between the input rate and a standard rate of the constant rate data stream in each cycle of a reference clock; encapsulating the constant rate data stream into a Gigabit-Passive Optical Network (GPON) Encapsulation Method (GEM) frame by using a bit as a minimum encapsulation unit; and encapsulating the GEM frame into a GPON Transmission Convergence Layer (GTC) frame, and sending the GTC frame to the second network device through a GPON network. Therefore, the technical solutions may be widely applied to the GPON network.

Abstract: According to one embodiment, an optically coupled insulating device includes an optical transmitter and an optical receiver. The optical transmitter includes an analog-to-digital converter, an encoder, a transmitting controller, and an electrooptical transducer. The encoder is configured to generate a transmitting signal by superimposing an output of the analog-to-digital converter onto a signal based on a clock signal. The transmitting signal is encoded to have an average duty ratio of more than zero and less than one. The transmitting controller is configured to output one of the transmitting signal and the output of the analog-to-digital converter depending on an input level of the analog signal. The electrooptical transducer is configured to convert an output of the transmitting controller into an optical signal. The optical receiver includes an optoelectrical transducer, a decoder, and a receiving controller.

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: The present invention relates to filter, coherent receiver device and coherent receiving method. The filter is used for converting a partial response signal into a full response signal, wherein the filter uses the following transfer function HPre-Filter(z) with respect to a partial response signal having a transfer function H PR ? ( z ) = A ? ( 1 + z - 1 ) m ? ( 1 - z - 1 ) n : ? ? H Pre - Filter ? ( z ) = 1 A ? ( 1 + ? ? ? z - 1 ) m ? ( 1 - ? ? ? z - 1 ) n , in which A is other item, m and n are integers larger than or equal to 0 but not being 0 at the same time, 0<?<1.

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: 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 and apparatus for optical signaling. In one embodiment, a laser driver converts a digital voltage sequence to a current signal having a bias mode adjustable by a bias control and a modulation mode adjustable by a modulation control. A laser generates an optical signal responsive to the current signal of the laser driver. In one embodiment, a photo-detector receives an optical signal and generates a single ended current signal. A transimpedance amplifier circuit converts the single ended current signal to a differential voltage signal. A clock recovery circuit generates an aligned clock signal and a sampler circuit uses the aligned clock signal to retrieve a digital voltage sequence.

Abstract: In a communication system in which a station-side line terminal apparatus 1 and a user-side line terminal apparatus 10 perform communication via a plurality of redundant physical lines, the user-side line terminal apparatus 10 monitors an out-of-synchronization error and line abnormality of the physical lines and, when line abnormality is detected (P4), shifts from a registered state to a holdover state for deferring discarding of setting information such as link information. The user-side line terminal apparatus 10 suppresses detection of the out-of-synchronization error during a deferred period to prevent a communication link from being disconnected by the out-of-synchronization error and prevent initial setting from being required. The station-side line terminal apparatus 1 switches a line during the deferred period (P7) and, after transmitting a synchronization signal (P8) to synchronize with the user-side line terminal apparatus, resumes normal communication.

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 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: 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 communication system comprising an emitter of weak light pulses, a detector which is capable of detecting single photons, and a source of a clock signal, wherein said emitter and detector are synchronised using said clock signal, the system further comprising a frequency divider for said clock signal to produce a reduced frequency clock signal and a clock regenerator for regenerating the original clock signal from the reduced frequency clock signal, the system further comprising a communication channel configured to communicate the clock signal between the emitter and detector, the clock signal being reduced before sending through said channel and reconstructed after it has exited said channel.

Abstract: An electro-optic conversion module (30) is disclosed, including: an electric interface unit (31) configured to receive multiple electric signals to be converted and transmit each electric signal to be converted to a corresponding electro-optic conversion unit (32); electro-optic conversion units (32) configured to convert the electric signals from the electric interface unit (31) into optical signals; a multiplexer unit (33) configured to multiplex the optical signals from the electro-optic conversion units (32) into a wavelength division multiplexed signal; and an optical interface unit (37). An optic-electro conversion module and the conversion methods are also disclosed in the present disclosure. With the electro-optic conversion module (30), the optic-electro conversion module and the conversion methods of the present disclosure, the electro-optic conversions for multiple electric signals or the optic-electro conversions for multiple optical signals may be achieved in the same module.

Abstract: A subscriber terminal connected to a central-office unit in an optical communication network includes a variable optical attenuator for attenuating an optical signal received from the central-office unit; an optical-electric converter for converting the optical signal received via the attenuator to a corresponding electric signal; a clock extractor for extracting a clock from the electric signal and producing a clock extraction information signal representing whether or not the clock is extracted stably; and a terminal controller. The controller includes a clock extraction decider for determining whether or not the extractor stably extracts the clock on the basis of the information signal, a receiving level adjuster for setting an attenuation value to a value between a minimum and a maximum value, and an attenuation controller for setting the attenuation amount for the attenuator to the set attenuation value.

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: An active/standby switchover device and an active/standby switchover method of an asynchronous backplane in a transport network are provided. A local oscillator clock is adopted to obtain a clock of a working path, so as to replace the clock of the working path tracked in a phase-locked loop mode. An active/standby switchover operation is realized by using the local oscillator clock, so that the implementation cost is greatly reduced, and the hysteresis problem of the phase-locked loop tracking clock during the active/standby clock switchover is eliminated, thereby effectively achieving the lossless switchover of services.

Abstract: This disclosure is directed to techniques for facilitating clock recovery in optical networks. An optical network terminal (ONT) that terminates a fiber link of an optical network includes a clock mode selection module that automatically selects a clock recovery mode based on a type of optical network to which the ONT connects and a type of service provided to one or more subscriber devices coupled to the ONT. By automatically selecting the clock recovery module, an administrator or other user need not provision this aspect of the optical network, thereby reducing administrative tasks and facilitating the provisioning of the optical network. In addition, the techniques enable selection of the most optimal clock recovery mode based on the current state of the optical network.

Abstract: Burst mode clock and data recovery (BCDR) circuit and method capable of fast data recovery of passive optical network (PON) traffic. An over-sampled data stream is generated from an input burst data signal and a phase interpolator generates sampling clock signals using a reference clock and phase information. A phase estimation unit (PEU) determines a phase error in the over-sampled data streams; and a phase retrieval unit sets the phase interpolator with the respective phase information of the input burst data signal prior to reception of the input burst data signal.

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: In a method for controlling timing of an upstream from an optical network termination device to an optical line termination device, a downstream transmission is analyzed to determine a core clock rate for the termination device. The core clock signal is then used to determine a transmitter clock signal to be used for upstream transmission, where the transmitter clock signal is offset from the core clock signal. The offset transmitter clock signal may be determined in the receiver or in the transmitter of the termination device and by a delay lock loop or by a clock data recovery/generator circuitry. For example, the transmitter clock signal may be taken from a plurality of phase adjusted clock offset signals created by the clock data recovery/generator circuitry during identification of the core clock signal.

Abstract: A first node receives a first phase modulated optical signal at a first wavelength from a master node. The first node also transmits a first amplitude modulated optical signal to the master node at the first wavelength using a portion of the first phase modulated optical signal as a light source.

Abstract: An O/E conversion element converts an input NRZ optical signal into an electric signal. A clock recovery circuit recovers a clock signal from the electric signal obtained by the O/E conversion element. A phase modulator applies phase modulation to the NRZ optical signal, using the recovered clock signal. An intensity modulator applies intensity modulation to the NRZ optical signal, using the recovered clock signal. A dispersion medium compensates for a frequency chirp of an optical signal output from the intensity modulator.

Abstract: An optical line termination includes a deserializer that parallelizes burst data received from a termination device, a fixed-pattern generating unit that generates fixed pattern data that is a predetermined fixed data, and a data selecting unit that selects either the fixed pattern data or the burst data based on a data-head instruction signal indicating a head of the burst data and a data-end instruction signal indicating an end of the burst data, and inputs the selected data to a deserializer as data to be parallelized.

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.

Abstract: A method, a device, and a system for realizing data transmission extension in a passive optical network (PON) are provided. Between a burst-mode clock and data recovery (BCDR) module and an electrical-optical (E/O) amplification module, the device includes a delimiter matching module and a preamble buffering and compensating module. The delimiter matching module is adapted to receive a data frame sent by the BCDR module and determine a location of a delimiter in the data frame. An optical-electrical (O/E) amplification module performs O/E conversion, amplification, and shaping on the data frame. The BCDR module then performs clock and data recovery processing on the data frame.

Abstract: A clock recovery method and apparatus is provided. The high-order demultiplexing-demapping unit (102) demultiplexes and demaps the high-order OTN frame (101) into N low-order ODTUjk frames (103), and transmits the N low-order ODTUjk frames (103) to the low-order demapping unit (104); the low-order demapping unit (104) respectively demaps the N ODTUjk frames (103) into N ODUj frames (105), and writes the ODUj frames from memory unit 1 (106) to memory unit n (108) into memory unit n+1 (109) to memory unit 2n (111) by using the clock signal whose gaps are uniformly distributed; and the ODUj frame clock generating unit (113) adjusts the read out clock in memory unit n+1 (109) to memory unit 2n (111), i.e. ODUj frame clock (114), according to the data volume stored in memory unit n+1 (109) to memory unit 2n (111).

Abstract: The communication system having a transmitter and a receiver, wherein the transmitter and the receiver are coupled by a clock channel and a data channel, wherein the clock channel is shorter than the data channel and wherein the receiver comprises a delay circuit for extracting a jitter signal from a clock channel signal, delaying the extracted jitter signal, and generating a receiver clock signal for the receiver by the delayed jitter signal.

Abstract: The present invention provides a light receiving apparatus using the DQPSK demodulation method. The light receiving apparatus comprises: one Mach-Zehnder interferometer for branching a received light signal into light signals at two arms to allow the branched two light signals to interfere with each other; one balanced photoelectric converter for converting the two interfered light signals, by using the Mach-Zehnder interferometer, into an electric signal corresponding to a difference between light intensities of the two light signals; and a phase adjuster for dynamically shifting the phase of a light signal passed through one of the two arms at the Mach-Zehnder interferometer.

Abstract: A topology for optical transceiver components comprises an electrical signal interface stage, a data timing and signal reformatting stage, and an optical fiber interface stage. Unlike transceiver components known in the art, functions having signals with the most jitter are partitioned into the electrical signal interface stage. Data timing functions, for example retiming or clock and data recovery, are included in the data timing and reformatting stage. Output jitter from the data timing and signal reformatting stage is approximately equal to jitter in a clock signal, enabling use of semiconductor components having jitter greater than SONET limits and thereby increasing a value of production yield. Embodiments of the invention are well suited for 40 G transmitters and receivers in nonconnectorized surface mount packages. 40 G transceivers built in accord with the invention are expected to have lower cost, smaller size, and higher production yield than 40 G transceivers known in the art.

Abstract: In a coherent optical receiver of an optical communications network, a method of recovering a clock signal from a high speed optical signal received through an optical link. A set of compensation vectors are adaptively computed for compensating Inter-symbol Interference (ISI) due to at least polarization impairments of the optical signal. A channel delay is estimated based on the computed compensation vectors. The estimated channel delay is subtracted from the computed compensation vectors to generate corresponding modified compensation vectors. Finally, the modified compensation vectors are used to derive a recovered clock signal.

Abstract: A transponder includes a CDR section that extracts clocks from an input signal, an oscillating section that can output various frequencies to the CDR section, a frequency instruction processing section that instructs the oscillating section to output an arbitrary frequency, a detection processing section, and a frame processing section control section. The detection processing section determines whether the frequency output from the oscillating section and an input signal synchronize in frequency or not in response to an instruction by the frequency instruction processing section, and detects a synchronization frequency. The frame processing section control section operates a frame processing section based on the synchronization frequency detected by the detection processing section.

Abstract: A transceiver includes a receiver unit including a clock and data recovery unit. The transceiver includes a transmitter unit and a digital core coupled to the receiver unit and the transmitter unit. A switch circuit is positioned after the clock and data recovery unit, and is configured to route data from the receiver unit to the transmitter unit in a test mode of the transceiver.

Abstract: A process for transmitting data on an optical fiber including multiplexing in wavelength signals coming from a plurality of monochrome transmitters, each of which has its own wavelength, and modulating information to be transmitted by a carrier realized per channel, wherein timing (clocking) of each transmitter is controlled by a common clock.

Abstract: An economical optical network is constituted by effectively using network resources by using the minimum number of, or minimum capacity of 3R repeaters. 3R section information corresponding to topology information on the optical network to which an optical node device itself belongs is stored, and the 3R section information stored is referred so as to autonomously determine whether or not the optical node device itself is an optical node device for implementing the 3R relay when setting an optical path passing through the optical node device itself. Alternatively, when the optical node device itself is a source node, another optical node device for implementing the 3R relay among the other optical node devices through which the optical path from the optical node device itself to the destination node passes is identified, and this identified optical node device is requested to implement the 3R relay when setting an optical path in which the optical node device itself is a source node.

Abstract: In an optical receiving apparatus for receiving an optical DQPSK signal, a phase difference between both arms of an optical interferometer is controlled to an optimum value. The optical DQPSK signal is incident on two optical interferometers in each which a delay-time difference between two arms is set to be equal to a 1-symbol time of the optical DQPSK signal and which are orthogonal to each other. The optical receiving apparatus converts the optical DQPSK signal into an intensity signal and receives it. A differential amplifier obtains a difference signal between outputs of a pre-amplifier and a discriminator connected thereto. The difference signal includes, as an amplitude, a phase shift in a phase section. A control circuit adjusts the phase of the phase section in the optical interferometers to reduce this difference signal, and changes the phase difference between the two arms to a desired phase difference.

Abstract: The present invention relates to an adaptive and all-optical method for data packet rate multiplication compatible with multiple data rates and/or multiple communication protocols. By performing a real-time pulse width compression on an original electronic or optical packet from an end user or a network interface device, the method generates an optical packet having an identical rate with the original packet while the duration of each pulse being significantly reduced. Then, by eliminating any redundant idle time due to the pulse width compression, the method also shortens data period and thus makes the rate of packet multiplied. The present invention addresses the technical problem of limited data rate in EO/OE conversion as known in the prior art and solves fundamentally the interconnection and communication between networks or systems of different data rates and/or protocols.

Abstract: Femtosecond pump/probe experiments using short X-Ray and optical pulses require precise synchronization between 100 meter-10 km separated lasers in a various experiments. For stabilization in the hundred femtosecond range a CW laser is amplitude modulated at 1-10 GHz, the signal retroreflected from the far end, and the relative phase used to correct the transit time with various implementations. For the sub-10 fsec range the laser frequency itself is upshifted 55 MHz with an acousto-optical modulator, retroreflected, upshifted again and phase compared at the sending end to a 110 MHz reference. Initial experiments indicate less than 1 fsec timing jitter. To lock lasers in the sub-10 fs range two single-frequency lasers separated by several teraHertz will be lock to a master modelocked fiber laser, transmit the two frequencies over fiber, and lock two comb lines of a slave laser to these frequencies, thus synchronizing the two modelocked laser envelopes.

Abstract: An optical clock signal recovery apparatus includes a mode-locked semiconductor laser that generates an optical pulse train polarized in a first direction. Optical components of the apparatus transmit a component of an input optical signal polarized in a second direction, perpendicular to the first direction, into the mode-locked semiconductor laser while blocking the component of the input optical signal polarized in the first direction, and transmit light exiting the mode-locked semiconductor laser polarized in the first direction, while blocking light exiting the mode-locked semiconductor laser polarized in the second direction. The transmitted exiting light is output as a recovered optical clock signal.