Abstract: Methods and systems are provided for cancellation of chromatic dispersion combined laser phase noise. A method may include measuring a differential of laser phase noise using two optical pilot signals, the pilot signals each having a different optical frequency, or using an optical carrier and a pilot signal. The method may also include determining an approximate laser phase noise present in an optical system based on the measured differential of laser phase noise. The method may further include compensating for laser phase noise based on the determined approximate laser phase noise.

Abstract: An example apparatus comprises an optical transmitter which includes a first processor and at least two optical modulators. The first processor is configured to generate a first electronic representation for each of at least two optical signals for carrying payload data modulated according to a one-dimensional (1-D) modulation format, and to induce on respective ones of the first electronic representations an amount of dispersion that depends on a power-weighted accumulated dispersion (ADPW) of a transmission link through which the at least two optical signals are to be transmitted thereby generating complex-valued electronic representations of pre-dispersion-compensated optical signals. Each of the at least two optical modulators modulate a respective analog version corresponding to a respective one of the complex-valued electronic representations onto a polarization of an optical carrier.

Abstract: An apparatus-transmitting signals in a network includes a light source generating an optical signal for encoding information transmitted over a light path of the network, a modulator controlling the optical signal to generate chirped optical pulses having a first frequency spectrum such that when the pulses are transmitted from the apparatus and received at an end of the first light path the pulses have a chromatic dispersion penalty that is less than a predetermined penalty. Modulation control circuitry receives instructions from a remote controller and, in response to the instructions, controls the modulator such that the chirped optical pulses have a second frequency spectrum such that when the pulses are transmitted from the apparatus and received at an end of a second light path of the telecommunications network the pulses have a chromatic dispersion penalty that is less than a predetermined penalty.

Abstract: A distortion compensator, an optical receiver and a transmission system including an operation selectively compensating for linear waveform distortion exerted on an optical signal via a plurality of distortion compensators and compensating for nonlinear waveform distortion exerted on the optical signal using nonlinear distortion compensators.

Abstract: A distortion compensating apparatus which compensates for distortion in a waveform of a received light signal through a digital signal processing includes a plurality of fixed amount compensators which compensate for the distortion in the waveform at respective given compensating amounts. The combination of operating states of the plurality of fixed amount compensators is changed by on/off switching of each of the plurality of fixed amount compensators, and the plurality of fixed amount compensators are cascaded.

Abstract: A time domain filter receives a double sideband (DSB) input in the frequency domain and compresses this input into a time domain signal filtered by a time gate for providing a time filtered signal that is then expanded back into the frequency domain as a single sideband (SSB) output with one sideband being filtered by the time gate for translating DSB signals into SSB signals well suited for communicating chirped modulated signals as SSB signals along an electrical line or optical fiber without dispersive nulling of the communicated signal.

Abstract: An optical dispersion compensator including a first optical device in which light inputted from a first port is outputted from a second port and light inputted from the second port is outputted from a third port, an optical filter type dispersion compensation device that receives light from the second port of the first optical device and compensates wavelength dispersion with respect to the received light, and a second optical device that includes a fourth port to which light is inputted from the optical filter type dispersion compensation device, and in which the light inputted from the fourth port is outputted from a fifth port and light inputted from a sixth port is outputted from the fourth port.

Abstract: A polarization mode dispersion compensator that includes two stages, one for reducing or eliminating first order polarization mode dispersion of an optical signal, and second stage for reducing or eliminating higher order polarization mode dispersion of the optical signal. In each stage, the polarization is adjusted so as to reduce polarization mode dispersion. Based on the power levels of various polarization states generated at the second polarization controller, the optical signal to noise ratio may be estimated. Furthermore, based on the amount of adjustment used to control the polarization controllers and the differential group delay, the polarization mode dispersion may be estimated.

Abstract: Systems and methods of compensating for transmission impairment are disclosed. One such method includes receiving a polarization-division multiplexed optical signal which has been distorted in the physical domain by an optical transmission channel, and propagating the distorted polarization-division multiplexed optical signal backward in the electronic domain in a corresponding virtual optical transmission channel.

Abstract: An optical transmission system is provided with an optical transmission apparatus, an optical reception apparatus, an optical transmission line redundantly configured with an active system optical transmission line and an standby system optical transmission line, an optical switch that switches an optical transmission line between the active system optical transmission line and the standby system optical transmission line, a variable dispersion compensator placed between the optical switch and the optical reception apparatus, a dispersion amount measuring unit that measures the dispersion amount of the standby system optical transmission line when the active system optical transmission line is being selected by the optical switch, a dispersion compensation amount setting unit that sets the amount of dispersion compensation to be applied to the standby system optical transmission line based on the measured dispersion amount of the standby system optical transmission line, and a control unit that controls, when

Abstract: Techniques, devices and applications are provided for monitoring a polarization mode dispersion (PMD) effect in an optical signal.

Abstract: A propagation apparatus includes a plurality of dispersion compensation execution units which accept a signal of a single wavelength from a wavelength-multiplexed signal which is received and execute dispersion compensation on the signal by inputting the accepted signal to a tunable dispersion compensator with an adjusted dispersion value, and a dispersion value calculation unit which acquires each dispersion value adjusted by the plurality of the dispersion compensation execution units, approximates the dispersion value of the wavelength assigned to a newly built line by using the acquired dispersion values whose signal error rates are in a tolerable range, and sets the approximated dispersion value as an initial value in the tunable dispersion compensator of the newly built line.

Abstract: A system and method for in-service optical dispersion determination are provided. Optical dispersion is determined by splitting a first optical signal into two components, introducing a time delay between the two components such that corresponding pulses of the two components partially overlap, combining the two components to generate a combined optical signal comprising a first component and a second component, determining power of the combined optical signal while applying a plurality of dispersion compensation values, in order to determine a dispersion compensation value that results in a minimum detected power of the combined optical signal. Polarization Mode Dispersion is determined by adjusting the time delay that is introduced until the power of the combined optical signal is substantially equal for all of the plurality of dispersion compensation values.

Abstract: A method for compensating for optical dispersion includes receiving an optical signal at a first node of an optical network that includes a first set of channels and a second set of channels that are each configured to be received using coherent digital receivers at a second node of the optical network. Each coherent digital receiver provides electronic dispersion compensation for the received channel at the second node. The method also includes forwarding the first set of channels from the first node without performing optical dispersion compensation on those channels. Furthermore, the method includes compensating for optical dispersion in the second set of channels at the first optical node and forwarding those channels from the first node. The optical dispersion compensation on the second set of channels at the first node provides dispersion compensation in addition to the compensation provided by the associated coherent digital receivers at the second node.

Abstract: According to an aspect of an embodiment, an optical modulation device includes a Mach-Zehnder modulator and a controller. The Mach-Zehnder modulator is supplied a drive signal and a bias voltage. The Mach-Zehnder modulator modulates inputted light on the bases of the drive signal and the bias voltage. The drive signal selectively is superimposes a predetermined frequency signal. The bias voltage selectively is superimposes the predetermined frequency signal. The controller selects a superimposing target which is the drive signal or the bias voltage so as to change modulation formats.

Abstract: A transmission device has a light emitting element for converting an electric signal to an optical signal and transmitting the same, and a drive section for outputting the optical signal from the light emitting element and driving the light emitting element by providing the electric signal to the light emitting element. The electric signal provided by the drive section to the light emitting element is a waveform deformed signal having a waveform in which a time required for a fall is longer than a time required for a rise in a binary signal having a signal of high level and a signal of low level.

Abstract: A wavelength dispersion measurement method includes generating a plurality of test lights in the first terminal, the wavelengths of which are different from a wavelength of a signal light, multiplexing each test light with the signal light and outputting the multiplexed light to the first transmission path, reconverting each electrical signal after converting each beam into electrical signals, multiplexing each test light with the signal light and outputting the multiplexed light to the second transmission path, reconverting each electrical signal after converting each test light into electrical signals, multiplexing each test light with the signal light and outputting the multiplexed light to the first transmission path, measuring times for each test light to be propagated up to a specified number of go-around, and measuring a change of a wavelength dispersion amount in the paths based on a difference between the measured propagation times of each wavelength.

Abstract: A signal equalizer for compensating impairments of an optical signal received through a link of a high speed optical communications network. At least one set of compensation vectors are computed for compensating at least two distinct types of impairments. A frequency domain processor is coupled to receive respective raw multi-bit in-phase (I) and quadrature (Q) sample streams of each received polarization of the optical signal. The frequency domain processor operates to digitally process the multi-bit sample streams, using the compensation vectors, to generate multi-bit estimates of symbols modulated onto each transmitted polarization of the optical signal. The frequency domain processor exhibits respective different responses to each one of the at least two distinct types of impairments.

Abstract: The mixing of coherent optical wavelength channels with non-coherent optical wavelength channels. Before mixing, a dispersive element introduces dispersion into the coherent optical wavelength channels and/or into the non-coherent optical wavelength channels such that the dispersion map of the coherent optical wavelength channels is different than the dispersion map of the non-coherent optical wavelength channels. By allowing the coherent channels to have a different dispersion map, the dispersion map may be moved further from the zero dispersion point, which can degrade coherent detection. Accordingly, coherent optical channels and non-coherent optical channels may be transmitted effectively over the same optical link.

Abstract: An optical assembly in an optical link coupling two optical terminals. The optical assembly receives and demultiplexes two groups of optical wavelength channels which are each treated separately as far as dispersion compensation and discrete amplification are concerned. The optical assembly then multiplexes the two groups back into the same fiber for further transmission. For instance, one group of optical wavelength channels may each be coherent channels, and subject to no dispersion in the optical assembly, while the other group may contain non-coherent channels, which are subject to dispersion compensation in the optical assembly.

Abstract: A chromatic dispersion compensation system for an optical transmission system incorporates circuitry which determines the length of an optical fiber extending between an output amplifier and an input amplifier. Based on fiber type, the total chromatic dispersion on the fiber is determined. Compensation can then be automatically implemented.

Abstract: A tunable chromatic dispersion compensation device used to compensate chromatic dispersion of wavelength of at least one predetermined wavelength band of light signal is provided. The tunable chromatic dispersion compensation device comprises a chromatic dispersion compensator, and a controller. The chromatic dispersion compensator comprises at least a first chromatic dispersion compensation unit and a second chromatic dispersion compensation unit connected with the first chromatic dispersion compensation unit in series. The first chromatic dispersion compensation unit has a free spectral range, the second chromatic dispersion compensation unit has a free spectral range same as to that of the first chromatic dispersion compensation unit. Each chromatic dispersion compensation unit comprises an interference cavity. The controller comprises an inputting unit being configured for inputting a predetermined chromatic dispersion compensation information.

Abstract: A device and method for depolarising the total field of a wavelength division multiplexed (WDM) signal is provided. A polarization maintaining multiplexor combines a plurality of optical signals to form a polarized multiplexed signal. The multiplexed signal is then passed through a differential group delay (DGD) element adapted to modify the polarization state of one or more optical source signals within the multiplexed signal and thereby to at least partially depolarise the multiplexed signal.

Abstract: An optical transmission system having an optical source, an optical dispersion compensation filter optically connected to the optical source, and a control system. The optical source generates a modulated optical signal having an optical spectrum and a value of dispersion robustness. The optical dispersion compensation filter has at least two cascaded optical resonators and a periodic transfer function rigidly translatable in the frequency spectrum to obtain translation in frequency of the transfer function without a substantial change in shape, and characterized by a free spectral range. The control system acts on the optical dispersion compensation filter in order to rigidly translate the transfer function along the frequency spectrum in first and second positions in the frequency spectrum. The translation of the transfer function between the first and the second positions is smaller than the free spectral range.

Abstract: A chromatic dispersion compensation design system includes: an input unit that inputs information of an optical network having a plurality of nodes optically coupled to each other via an optical transmission path; an allowable range determining unit that determines an allowable range of a residual chromatic dispersion with respect to every wavelength path of a plurality of signals from a starting node to a terminal node, based on the information of the optical network; and a calculation unit that calculates a wavelength path capacity in the allowable range of the residual chromatic dispersion, in view of a chromatic dispersion variability of each optical element in the optical network.

Abstract: In a method and system for providing dispersion compensation in an optical system, there is coupled into the optical system at least one pathway into which there is connected a tunable chirped fiber Bragg grating, each such grating providing a respective tunable amount of dispersion. At least one respective DGD element is connected into the respective pathway for each such grating. The set of all such respective DGD elements in a given pathway introduces a bias differential group delay DGD(bias) having an absolute value that, for at least one tuning value of the grating, is substantially equal to differential group delay introduced by the grating.

Abstract: The chromatic dispersion of an optical component is measured with high accuracy using a simple set-up, which includes a pump light source, a probe light source, and a measuring means. Pump light having a wavelength ?pump and probe light having a wavelength ?probe is propagated through an optical component, with the wavelength ?probe being apart from the wavelength ?pump by a given frequency. The generation efficiency of the idler light with respect to the wavelength ?pump is calculated by measuring the power of idler light having a wavelength ?idler output from the optical component, and by seeking the pump light wavelength for making the generation efficiency a local extreme value, the chromatic dispersion of the optical component is calculated from the result of calculation of phase mismatch among the pump light wavelength having such wavelength as sought, the corresponding probe light wavelength, and the corresponding the idler light wavelength.

Abstract: A method is provided for dispersion compensation of an optical signal communicated in an optical network. The method may include receiving an optical signal comprising a plurality of channels. The method may further include filtering at least one channel from the plurality of channels. The method may also include analyzing the at least one channel of the plurality of channels to measure optical dispersion in the at least one channel. The method may additionally include compensating for optical dispersion based on the measured dispersion.

Abstract: An OADM in a wavelength division multiplexing transmission system includes a wavelength selection switch that selects a predetermined wavelength from a multiple optical signal obtained by multiplexing a phase modulated signal and an intensity modulated signal and outputs the selected wavelength signal to a predetermined output port. The wavelength selection switch has a different delay for each wavelength of the multiple optical signal. For example, the wavelength selection switch includes a mirror array. Optical paths from the surfaces of mirrors arranged on the mirror array to the diffraction grating are different in the case of adjacent mirrors.

Abstract: According to the WDM optical transmission system, for optical signals of respective wavelength in a WDM light propagated through a transmission path, a spectrum component at a center wavelength of each optical signal and a spectrum component in the vicinity of the center wavelength thereof are selectively attenuated by a spectrum correction optical filter, so that the WDM light is transmitted in a state where intensity of sideband components in the spectrum of each optical signal is relatively increased. As a result, even if spectrum width of the optical signal of each wavelength is limited when the WDM light passes through the band-limiting device on the transmission path, degradation of transmission characteristics caused by the attenuation of sideband components is reduced.

Abstract: A dispersion compensation device includes: an optical branching unit to branch an optical signal to be received; a first dispersion compensator to perform dispersion compensation on one part of the optical signal branched by the optical branching unit with a variable compensation amount; a second dispersion compensator to perform dispersion compensation on another part of the optical signal branched by the optical branching unit; a monitoring unit to monitor the communication quality of an output optical signal of the second dispersion compensator; and a controlling unit to determine the direction of variation in chromatic dispersion of the optical signal based on the direction of variation in communication quality monitored by the monitoring unit and control the compensation amount of the first dispersion compensator based on the result of the determination.

Abstract: A tunable dispersion compensator (TDC) is tuned from a first dispersion setpoint to a second dispersion setpoint while maintaining continuity of the dispersion. The dispersion tuning follows a pre-determined trajectory in the time domain, so that continuity of the optical dispersion across the channel optical bandwidth is maintained while minimizing all other TDC-induced optical impairments during a tuning period.

Abstract: A method includes transmitting an optical signal over an optic link in a communication system, the optical link including an optical fiber and optical amplifier; coupling a coherent receiver in the communication system to the optic link for receiving the optical signal; and processing an output from the coherent receiver with digital signal processing DSP in the communication system, the DSP compensating for impairments of the optical signal due to the fiber optic link with an equivalent-link back-propagation.

Abstract: Various example embodiments are disclosed. According to one example embodiment, a phase error is estimated in a series of digital symbols of a phase-modulated signal, where the signal is subject to a non-linear phase shift error due to transmission of the signal through an optical fiber. A phase correction of an instant digital symbol that succeeds the series of digital symbols is estimated, where the estimated phase correction is based on the estimated phase errors in the series of digital symbols. The estimated phase correction of the instant digital symbol is limited to a maximum absolute value, and the estimated phase correction is applied to the instant digital symbol of the signal.

Abstract: An optical communication apparatus includes a receiver configured to receive an optical signal transmitted from an optical transmitting apparatus; a detector configured to detect a predetermined pattern signal included in the optical signal; a calculator configured to calculate, based on a waveform of the predetermined pattern signal, an amount of dispersion of the predetermined pattern signal; and a compensator configured to compensate for dispersion according to the amount of dispersion.

Abstract: A distortion compensation system and method may be used to compensate for data pattern dependent signal distortion in a signal received in a coherent optical signal receiver. In general, the distortion compensation system and method compares a received signal field with stored distorted signal waveforms associated with known data patterns and selects a compensation value associated with the distorted signal waveform that corresponds most closely with the received signal field. The distortion compensation system and method compensates the received signal using the selected compensation value and thus mitigates the effects of data pattern dependent signal distortion.

Abstract: In a dispersion compensating apparatus, a reference identifying unit identifies a reference (X dB down) that makes a penalty lower than a predetermined value in accordance with optical signal information and a reference identifying table, and a VIPA plate temperature adjusting unit adjusts a refractive index of a VIPA plate by modifying a temperature of the VIPA plate so that a transmission center wavelength derived from the reference matches the wavelength defined by an ITU-T Grid. If a dispersion compensation value setting unit performs an optimal residual dispersion value search, the VIPA plate temperature adjusting unit determines if a filtering penalty is lower than a predetermined value in accordance with a penalty management table. If the filtering penalty is lower than the predetermined value, temperature adjustment of the VIPA plate is not performed.

Abstract: A dispersion compensation device includes a variable dispersion compensator configured to subject an input optical signal to dispersion compensation, an optical receiver configured to convert an optical signal subjected to dispersion compensation into an electrical signal, recover a clock signal and a received data signal from the electrical signal, and output clock lock information indicating whether the clock signal is locked to the electrical signal, a signal processor configured to output bit error rate information on the received data signal, and a controller configured to variably control a dispersion compensation value of the variable dispersion compensator based on the bit error rate information and the clock lock information.

Abstract: A dispersion compensation method and a dispersion compensation device in an optical communication system are provided. The method mainly includes the following steps. A dispersion compensation value transmitted through a working path at a second wavelength is received through a non-working path at a first wavelength in an optical communication system. The non-working path at the first wavelength and the working path at the second wavelength use the same service channel. Dispersion in the non-working path at the first wavelength is compensated according to the dispersion compensation value. Therefore, no matter the working path is a main path or a backup path, the dispersion compensation value on the non-working path can be accurately regulated in time, such that the dispersion of the working path reaches an optimal status each time after the protection switching occurs to the service, thereby ensuring the fast switching of the service.

Abstract: An optical communication apparatus that includes multiple optically communicative components positioned optically in series. Some of the optically communicative components may be optical fiber segments of perhaps different types. The optical channel represented by the series of optically communicative components and approximates a transfer function of an optical channel of a longer optical fiber. Accordingly, rather than deal with a lengthy optical fiber, an apparatus having a shorter optical channel may be used instead. The construction of the optical communicative components may be calculating an input transfer function. The construction would include an ordering of discrete optically communicative components that, when placed optically in series, simulates an estimation of a particular transfer function. Testing may then occur by actually passing an optical signal through the series construction of optically communicative components, rather than through the longer optical fiber.

Abstract: The distributed Raman amplifier monitors an OSNR of each channel in a WDM light which has been propagated through a transmission path to be Raman amplified, and thereafter, is amplified by an optical amplifier in an optical repeating node; judges whether a monitor value of the OSNR is larger or smaller than a previously set target value thereof; and feedback controls a driving state of a pumping light source which supplies a Raman pumping light to the transmission path, based on the judgment result. The optical communication system comprises the above distributed Raman amplifier in each repeating span thereof, and performs a pumping light control of the distributed Raman amplifier corresponding to the repeating span selected based on the OSNR in each distributed Raman amplifier and the monitor result of span loss. As a result, it becomes possible to effectively improve the OSNR of each channel in the WDM light, and also, to reduce the power consumption.

Abstract: A method for determining a value of chromatic dispersion compensation in an optical network including a plurality of nodes connected by at least one transmission line, the plurality of nodes including a plurality of dispersion compensators, the optical network including a plurality of wavelength paths between the optional nodes, the method includes determining a compensation value of the dispersion compensators in the optical network by the computer, the compensation value selecting that an error between the object value of the residual chromatic dispersion in accordance with of the first end node of the first path and the permissible value of the residual chromatic dispersion of the first end node of the first path is least, and the value of the residual chromatic dispersion of the first end is in the permissible value of the residual chromatic dispersion of the second end node of the second path.

Abstract: In a network design apparatus, a full channel evaluator determines whether all wavelength channels for main signals can deliver the main signals of an existing optical network. When it is found that one or more wavelength channels cannot deliver main signals, a chromatic dispersion evaluator determines whether there are a specified number of wavelength channels that satisfy a specified chromatic dispersion condition. An optical signal-to-noise ratio (SNR) evaluator extracts a specified number of wavelength channels out of those satisfying the chromatic dispersion condition in descending order of optical SNRs thereof, and determines whether the extracted wavelength channels satisfy a specified optical SNR condition.

Abstract: A method for reducing cross-phase modulation in an optical signal includes receiving an optical signal comprising a plurality of channels, wherein the information being communicated in a first set of one or more of the channels is modulated using one or more single-polarization modulation techniques and wherein the information being communicated in a second set of one or more of the channels is modulated using one or more dual-polarization modulation techniques. The method also includes splitting the optical signal into at least a first copy of the optical signal and a second copy of the optical signal and terminating the second set of channels in the first copy. Furthermore, the method includes applying a differential group delay to the second copy, the differential group delay introducing a walk-off between symbols communicated in a first polarization component of the second set of channels and the symbols of a second polarization component of the second set of channels.

Abstract: A system to communicate optical data signals in parallel includes an optical splitter to split the data signals into two polarization multiplexed (PM) signals; and two reception channels coupled to the optical splitter, where each reception channel tracks and isolates a PM signal independently.

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: A signal detection method used in an optical receiver apparatus detects the variation of an optical input level from the presence or absence of a clock signal and appropriately controls a dispersion compensator, thereby enabling the presence or absence of an input signal to be correctly determined. The signal detection method includes: detecting the level of input light of an optical amplifier, storing the level of the detected input light, comparing the level of the stored previous input light with the level of current input light, detecting the level variation of the input light by the comparison to detect the state change of the presence or absence of an optical signal, performing a dispersion compensation on the input light, and extracting a clock from an optical input. When the level variation of the input light is detected, the presence or absence of the optical signal of the input light is determined from the presence or absence of the clock signal.

Abstract: A method for the polarization independent frequency domain equalization (FDE) on polarization multiplexing (POLMUX) coherent systems employing an adaptive crossing FDE which advantageously produces CD compensation, PMD compensation and PolDeMux within one functional block of a digital signal processor (DSP).

Abstract: The present invention relates to the quality monitoring of optical signals, which have different symbol rates and generated by different modulation schemes, used for example in a wavelength division multiplexing network. The apparatus according to the invention includes an optical splitter for outputting the input optical signal to a first optical route and a second optical route, an optical coupler for coupling a optical signal from the first optical route with a optical signal from the second optical route, a delay unit provided on the first optical route, and a phase shift unit provided on the first optical route or the second optical route.

Abstract: Methods and apparatus are provided for optical polarization mode dispersion compensator (PMDC) feedback control for APol-DPSK signals. A feedback signal generator includes a delay-line-interferometer (DLI), with a differential delay line delay (D) different from one bit period (Tb). In an exemplary embodiment, the DLI delay is in the range of 0.5 Tb<D<1.0 Tb, or 1.0 Tb<D<1.5 Tb, preferably 0.85 Tb or 1.15 Tb. The DLI is coupled to a single-ended detector, whose output is amplified and bandpass filtered around the frequency of half the bit rate. The filtered signal is then applied to an RF power detector to generate the PMDC feedback signal. Generation of the PMDC feedback signal in accordance with the present invention is insensitive to any alignment of the state of polarization (SOP) of the received APol-DPSK signal with the principal state of polarization (PSP) of the transmission link. As a result, there is no need for a polarization scrambler at the transmitter.