Abstract: An arrangement is described for compensating intra-channel nonlinearities in an optical communications system which combines optical dispersion compensation with electronic pre-distortion (EPD). EPD with moderate lookup table size can effectively suppress intra-channel nonlinearities over optical transmission links incorporating optical dispersion compensation. The arrangement can be implemented for a variety of optical communications systems, including 10 Gb/s, 40 Gb/s and higher bit rate systems as well as single-channel and wavelength-division multiplexing (WDM) systems.

Abstract: This present disclosure provides an optical transmission method and system. The system includes a pre-coder for pre-coding an input signal into a first pre-coded signal, an encoder/separator coupled to the first pre-coded signal and arranged to encode the first and second pre-coded signals into a first encoded signal with 0 degree phase shift and a second encoded signal with 180 degree phase shift, and an optical modulator for providing optical modulation to the first and second encoded signals with a light source such that the intensity of an output optical duo-binary (ODB) signal with frequency chirp has identical logic sequence as the input signal.

Abstract: Systems and methods are disclosed to perform nonlinear compensation (NLC) in an optical communication system by applying digital backpropagation (DBP) using a frequency-shaped split-step Fourier method (FS-SSFM), and processing a data block using an overlap-and-save method with a block size M and an overlap factor of N samples between adjacent blocks.

Abstract: An optical transmission device includes a signal generator configured to generate a first signal corresponding to an amount of residual chromatic dispersion that occurs in a light signal transmitted from the optical transmission device to a downstream device, and a superimposer configured to superimpose the first signal on the light signal transmitted from the optical transmission device and transmit the light signal superimposed by the first signal to the downstream device.

Abstract: The present invention relates to optical transmission systems. In particular, the present invention relates to a method and system for estimating the spectral efficiency which may be achievable in an optical transmission network and for adapting the parameters of the transmission network to the achievable spectral efficiency. A method and system for controlling an optical transmission system comprising a first and a second optical transmission channel is described. The first optical transmission channel is affected by the second optical transmission channel. The method comprises the steps of measuring the inverse signal-to-noise ratio of the first channel for a plurality of input power levels used by the first and second channel; determining a contribution of the second channel to the inverse signal-to-noise ratio; and determining the input power to the second channel, such that an overall throughput of the first and second channel is maximized.

Abstract: Thermal chirp compensation in a chirp managed laser. In one example embodiment, a laser package including a laser and an optical spectrum reshaper configured to convert frequency modulated optical signals from the laser into an amplitude modulated optical signals is provided. A thermal chirp compensation device is in communication with the laser package and a laser driver. The thermal chirp compensation device includes means for generating bias condition and temperature specific thermal chirp compensation signals that each corresponds to a predetermined level of thermal chirp that is induced in the laser by operating the laser at a particular bias condition and temperature.

Abstract: The pulse light source according to the present invention comprises: a seed pulse generator 1 for outputting an input pulse 10 as a seed pulse; a pulse amplifier 2; and a dispersion compensator 3 for dispersion compensating a light pulse output from the pulse amplifier 2. Moreover, the pulse amplifier 2 comprises a normal dispersion medium (DCF 4) and an amplification medium (EDF 5) that are multistage-connected alternately, for changing the input pulse 10 to a light pulse having a linear chirp and outputting the light pulse. Furthermore, an absolute value of the dispersion of the DCF 4 becomes to be larger than the absolute value of the dispersion of the EDF 5.

Abstract: An optical transmission system capable of efficiently reducing waveform distortion of an optical signal. A transmitting-side distortion compensation coefficient storage of a transmitting station stores transmitting-side distortion compensation coefficients for compensating for waveform distortion of an optical signal to be transmitted to a receiving station. A transmit signal processor performs distortion compensation on the optical signal on the basis of a suitable transmitting-side distortion compensation coefficient stored in the transmitting-side distortion compensation coefficient storage. A transmitter transmits the distortion-compensated signal to a transmission path. A receiver of the receiving station receives the optical signal from the transmission path. A receiving-side distortion compensation coefficient storage stores receiving-side distortion compensation coefficients for compensating for waveform distortion of the optical signal received by the receiver.

Abstract: A plurality of inductors are connected in series between a load resistor and a first transistor, and a plurality of second transistors provided in parallel are connected to the plurality of inductors.

Abstract: Disclosed herein are embodiments of a device, method of use and system for an analog multi-wavelength transamplifier. The transamplifier embodiments described herein allow the use of multiple wavelengths to segment logical service groups, such as for use in a CATV distribution system and a FTTH system having a broadband overlay. Improved optical signal power performance can be achieved by using direct modulating transmitters and maintaining polarization of the optical signals that are modulated by a phase modulator, such as an external waveguide.

Abstract: A method for processing data in an optical network element. A multi-carrier signal is linear pre-coded and the linear pre-coded signal is modulated. A corresponding optical network element is also described.

Abstract: An wave division multiplexed (WDM) optical transmitter is disclosed including a directly modulated laser array and a planar lightwave chip (PLC) having a plurality of OSRs that receive outputs of the laser array and increase the extinction ratio of the received light. An optical multiplexer receives the outputs of the OSRs and couples them to a single output port. The multiplexer has transmission peaks through its ports each having a 0.5 dB bandwidth including the frequency of a laser in the array. The optical multiplexer may be embodied as cascaded Mach-Zehnder interferometers or ring resonators.

Abstract: An apparatus for generating a dispersion compensation signal includes a splitting module for splitting a data signal to be transmitted into N channels of data signals; N pre-processing modules for adjusting in frequency domain the phases and amplitudes of the N channels of data signals and outputting N channels of pre-warped electrical signals; an optical carrier generating module for generating N channels of coherent optical carriers; N electro-optic modulators for modulating the N channels of coherent optical carriers based on the N channels of pre-warped electrical signals and generating N channels of pre-warped optical signals; an optical coupling module for coupling the N channels of pre-warped optical signals into a dispersion compensation optical signal. By pre-processing the data signals, the present disclosure may allow the use of existing devices to generate a dispersion compensation signal so that the bandwidth requirement set by prior art on the electrical device is reduced.

Abstract: A pre-equalization optical transmitter includes: an RZ conversion circuit for generating an RZ-type input data sequence based on an NRZ-type input data sequence and a clock that is twice the speed of the NRZ-type input data sequence; a digital filter for generating pre-equalized data by a convolution operation between the RZ-type input data sequence and a desired transfer function corresponding to the wavelength dispersion of an optical fiber transmission path; D/A converters for performing D/A conversion on the pre-equalized data to output analog pre-equalized data; and a vector modulator for modulating light from a laser light source based on the analog pre-equalized data to output an RZ-type optical signal.

Abstract: A transmitter reduces or minimizes pulse narrowing. In one approach, an optical transmitter is designed to transmit data over an optical fiber at a specified data rate using on-off keying. The transmitter includes a pre-converter electrical channel and a limiting E/O converter. The pre-converter electrical channel produces a pre-converter signal that drives the limiting E/O converter. The pre-converter electrical channel is designed to reduce pulse narrowing in the pre-converter signal. In one implementation, the pre-converter electrical channel includes a pre-emphasis filter that is designed to minimize pulse width shrinkage.

Abstract: Provided is a channel assignment method in a wavelength-division-multiplexed transmission system. The channel assignment method includes obtaining information about signal modulation schemes from a plurality of optical transmitters, and assigning channels to the respective optical transmitters in consideration of the obtained information about the signal modulation schemes. Accordingly, in transmission of channels of different modulation formats, cross phase modulation is minimized, thereby reducing inter-channel interference.

Abstract: An optical transmission apparatus for suppressing deterioration of transmission quality due to XPM in a wavelength division multiplexing optical communication system in which an intensity modulation optical signal and a phase modulation optical signal exist in a mixed form. The apparatus has an intensity inversion signal light output section which outputs light having an intensity pattern obtained by inverting intensity changes of the intensity modulation optical signal near a wavelength of the intensity modulation optical signal in arrangement on wavelength axis of optical wavelengths that can be multiplexed as a wavelength division multiplexed signal as intensity inversion signal light, and a wavelength division multiplexed optical signal output unit which wavelength-division-multiplexes the intensity modulation optical signal, the phase modulation optical signal and light from the intensity inversion signal light output section and outputs a wavelength division multiplexed optical signal.

Abstract: A distortion compensation circuit including a configurable delay may be used with one or more non-linear elements, such as a laser, to compensate for distortion generated by the non-linear element(s), for example, in broadband RF applications. Embodiments of the distortion compensation circuit may include a primary signal path with a configurable delay segment and a secondary signal path including at least one distortion generator. The configurable delay segment may be selectively configured to provide different delay settings to accommodate different RF loading conditions such that the delayed RF signal on the primary signal path is aligned with the distortion products generated on the secondary signal path when combined to form an RF signal with distortion compensation.

Abstract: An optical transceiver calibration system and manufacturing method to fabricate a dual closed loop control transceiver are provided. The calibration system and method includes measuring an operating temperature and determining operational parameters based upon the operating temperature. The operational parameters may include, for example, a target power for transmitting a digital one, a target power for transmitting a digital zero, a modulation current, and a bias current. A bias may be added to the temperature to account for the difference between the temperature at the temperature sensor and the optical equipment. The operational parameters are preferably calculated independently of each other and are used as initial values during operating modes and allow the control loop to converge more quickly. The optics data is may be scanned electronically via bar code or some other electronic format prior to test. The software residing on the module then calibrates and configures the transceiver.

Abstract: A transmitting apparatus using visible light communication generates transmission data into a two-dimensional data code according to a predetermined code method between the transmitting apparatus and a receiving apparatus and transmits the two-dimensional data code through a plurality of light emitting diodes (LED) that are arranged in a two-dimensional form. Therefore, the receiving apparatus senses light from a plurality of LEDs as an image using an image sensor, demodulates the image into a two-dimensional data code, decodes the two-dimensional data code using a code book, and restores data.

Abstract: A companding transform technique is incorporated into orthogonal frequency division multiplexed signals to reduce the peak-to-average ratio of the signals. Prior to the companding transform, an inverse discrete Fourier transform is performed on the signal. Following the companding transform, the signal is compressed, at which point the compressed signal may be advantageously optically transmitted.

Abstract: A digital filter processes an input signal to be conveyed through an optical communications system. The processing generates a predistorted signal using a compensation function that mitigates impairments of the optical communications system. The input signal has a sample period of T, while the predistorted signal has a sample period of T/2. The digital filter has a first branch including a respective first T-spaced filter for processing the input signal using the compensation function to generate a corresponding first output signal comprising nT/2 samples with n odd. A second branch includes a respective second T-spaced filter for processing the input signal with a delay of T relative to the first branch using the compensation function to generate a corresponding second output signal comprising nT/2 samples with n even. A combiner operates to combine the first and second output signals to generate the predistorted signal having a sample period of T/2.

Abstract: Thermal chirp compensation in a chirp managed laser. In one example embodiment, a method for thermal chirp compensation in a chirp managed laser (CML) includes several acts. First, a first bias condition and temperature is selected. Next, a first thermal chirp compensation signal is generated. Then, the laser is driven by biasing a first input drive signal with the first thermal chirp compensation signal. Next, a second bias condition and temperature is selected. Then, a second thermal chirp compensation signal is generated. Finally, the laser is driven by biasing a second input drive signal with the second thermal chirp compensation signal.

Abstract: A distortion compensation circuit compensates for distortion generated by one or more non-linear elements such as a laser device and may include a primary signal path for carrying an input signal and one or more secondary signal paths for generating distortion. The distortion compensation circuit may also include one or more controllable phase inverters on at least one of the paths. For example, the secondary signal path may include a distortion generator to produce distortion products from the input signal and a signal controlled phase inverter that inverts the phase of the distortion products. The distortion generator and phase inverter may be combined as an invertible distortion generator. The phase inversion may be controlled in response to a phase inversion control signal generated based on one or more parameters such as temperature.

Abstract: A modulated optical system with anti-clipping reduces or corrects clipping that might occur in the laser as a result of negative spikes or peaks in a multichannel RF signal. The system generally detects an envelope of the RF signal to generate an anti-clipping signal that follows at least a portion of the envelope and prevents one or more negative peaks from causing clipping by adjusting a bias current in response to the anti-clipping signal. The system may also reduce cross modulation by clamping the anti-clipping signal at an anti-clipping limit during lower power periods of the RF signal.

Abstract: An optical transmitter is disclosed wherein a signal processor receives a data stream and outputs a drive signal for a laser, where the drive signal encodes each bit of the data stream according to the values of adjacent bits effective to compensate for spreading of bits within the fiber. The output of the laser is input to an optical spectrum reshaper that outputs a signal having an enhanced extinction ratio.

Abstract: A method of protection switching between first and second transceivers where dispersion compensation is effected electrically in the transmitters. The method includes detecting, at the second transceiver, a signal failure of a signal transmitted from the first transceiver and, upon detecting the signal failure, signalling the first transceiver to change its compensation function. The signalling can be done by encoding overhead bits in a signal transmitted from the second to the first transceiver. Another method of protection switching includes both transceivers toggling alternate reception paths upon detecting a signal failure and changing their dispersion compensation function to that of their respective alternate path.

Abstract: Photonic integrated circuits (PICs) may include transmit and receive PICs that include individually tunable optical elements. In one implementation, a device may include a number of optical elements that form a number of optical channels. Tuners may be used to modify a property associated with the at least one of the optical elements where the modified properties of the optical elements adjust a frequency grid of the optical channels.

Abstract: A chirped pulse amplification (CPA) system and method is described wherein the dispersion of the system is tuned by actively tuning one or more system components, for example, using a temperature or strain gradient, or using actinic radiation. In other embodiments, an additional element, such as a modulator, is added to the CPA system to actively to tune the pulse. A pulse monitor is added to the system to measure an output pulse and provide feedback to one or more active tuning elements.

Abstract: A high peak intensity laser amplification system and the method therein implemented are provided. In a first aspect of the invention, the laser system includes at least one optical member (27) operably introducing a phase function into a high peak intensity laser pulse (25). A further aspect includes introducing destructive interference in an unchirped laser pulse prior to amplification and reconstructive interference in the output laser pulse after amplification. Dynamic pulse shaping is employed in another aspect of the present invention.

Abstract: Predistortion logic for an optical communications laser or optical modulator, includes predistortion logic embodied in a field programmable gate array (FPGA). A first analog to digital converter (ADC) provides a representation of an RF signal at an input of the FPGA. A digital to analog converter provides a representation of an output of the FPGA to a laser or modulator.

Abstract: A digital filter is provided for processing an electrical input signal to be conveyed through an optical communications system. The processing generates a predistorted electrical signal using a compensation function that substantially mitigates for intra-channel non-linearity imparted to the communications signal by the optical communications system. The digital filter has a memory having a limited size storing a reduced data set used for approximating an original, unreduced data set used to implement the compensation function. The reduced data set is used for the digital filter to apply the compensation function to mitigate the intra-channel non-linearity over longer transmission distances of the optical communications system than would be possible without the use of the reduced data set.

Abstract: An optical transmitter is disclosed wherein a modulating signal, such as an NRZ signal, encoding data is combined with a time derivative of the modulating signal and coupled to a directly modulated laser in order to generate artificial transient chirp in the output of the laser effective to substantially compensate for dispersion experienced by the output of the laser traveling through a dispersive medium such as an optical fiber. In some embodiments, the time derivative is added to the modulating signal only at the falling edges of the modulating signal.

Abstract: There is provided an optical signal transmission apparatus having a stable dispersion compensation function without unnecessarily controlling a compensation value even when a main signal quality is deteriorated due to a factor other than dispersion or in the case of a transmission failure. When it is determined that a signal quality is deteriorated due to dispersion of a fiber by determining a control mode of a variable dispersion compensator by means of optical noise information and received power information in addition to bit error information of a received signal, a compensation value of the variable dispersion compensator is varied and a compensation value other than the dispersion of the optical fiber is held to an existing set value.

Abstract: A distortion compensation circuit compensates for distortion generated by one or more non-linear elements such as a laser device. The distortion compensation circuit may be used in an optical transmitter, such as a laser transmitter used for forward path CATV applications. The distortion compensation circuit may include a primary signal path and a secondary signal path that receive an input signal. The secondary signal path produces distortion of a magnitude corresponding to the magnitude of, but at an opposite phase to, the distortion generated by the non-linear amplifier. The secondary signal path includes a plurality of distortion sub-paths with each of the distortion sub-paths configured to produce intermodulation distortion products of the same distortion order but for different frequency dependent orders in a time dependent series representative of the distortion produced by the non-linear amplifier.

Abstract: A method of transmitting information over a non-linear optical channel includes the step (152) of generating an information-bearing signal, preferably an OFDM signal, which includes a plurality of closely-spaced sub-carriers in the frequency domain. A time-varying phase modulation is determined (154), which is a first function, and preferably a linear function, of the transmitted optical power corresponding with the information-bearing signal. The information-bearing signal and the time-varying phase modulation are applied (156) to an optical source in order to generate a corresponding transmitted optical signal having substantially the stated transmitted optical power characteristic. The first function of transmitted optical power is selected so as to mitigate the effect of the non-linearity of the optical channel upon the transmitted optical signal.

Abstract: A method of communicating digital information over a dispersive optical channel includes encoding the digital information into a plurality of data blocks, each of which includes a number of bits of the information. A time-varying electrical signal is generated which corresponds with each of said data blocks. The time-varying electrical signal is applied to an optical transmitter (122) to generate an optical signal which includes an asymmetrically amplitude limited transmitted signal modulated onto an optical carrier. The optical signal is then transmitted over the dispersive optical channel (106). At a receiving apparatus (104) the optical signal is detected to produce an electrical signal which corresponds with the asymmetrically amplitude limited transmitted signal.

Abstract: A method performed by a networked device for energy efficient operation of an optical transceiver of the networked device is described herein. It is determined whether a port control of the networked device is enabled to operate in an energy efficient state. Where the port control is enabled to operate in the energy efficient state and an absence of a valid receive energy from a link partner is determined, a laser transmitter of the optical transceiver is pulsed by asserting and de-asserting a control signal.

Abstract: In a quaternary phase modulator including two phase modulators disposed in parallel and a phase adjuster that adjusts a phase difference when the outputs of the two phase modulators are combined, there are provided a second light source that introduces light propagated in a backward direction, a first controller that controls the bias of the two phase modulators so that the intensity of the backward light is a minimum on the input side of the quaternary phase modulator, and a second controller that controls the bias of the phase adjuster so that a result monitored by a photodiode having a bandwidth not exceeding the bit rate on the output side of the quaternary phase modulator is a minimum, the first controller being implemented after the second controller is implemented.

Abstract: A data transmission system comprising a transmitter and a receiver. The transmitter comprises a phase encoder for partitioning consecutive bit data to be input in data in units of X bits; and converting a 2x value indicated by the data of X bits in unique association with an (N/2?1)Y value of a Y symbol, and for confining use of signal points, from among the signal points of N-ary phase, only to a signal point P1 (at a phase angle 0) and N/2?2 signal points P(2n+2) (where 1?n<N/2?2). The receiver comprises a phase decoder for notifying an error detection when a signal point other than a signal point that are permitted to be used is received, and performing an error correction by changing the signal point to a signal point which has a smaller hamming distance.

Abstract: Provided are an optical amplifier, a control method therefor, and an optical transmission system that can use a simple technique to correct SRS tilt generated in a transmission path after a back-stage amplifier out of two amplifiers, which respectively amplify an input optical signal in a front stage and a back stage of a variable attenuator, in accordance with the number of wavelengths of the optical signal transmitted on the transmission path. A control parameter for controlling the two amplifiers and the attenuator is determined so as to correct a spectral slope caused by stimulated Raman scattering of the optical signal based on network information received from another device, and the two amplifiers and the attenuator are controlled based on the control parameter.

Abstract: A distortion compensation circuit compensates for distortion generated by one or more non-linear elements such as a laser device and may include a primary signal path for carrying an input signal and one or more secondary signal paths for generating distortion. The distortion compensation circuit may also include one or more controllable phase inverters on at least one of the paths. For example, the secondary signal path may include a distortion generator to produce distortion products from the input signal and a signal controlled phase inverter that inverts the phase of the distortion products. The distortion generator and phase inverter may be combined as an invertible distortion generator. The phase inversion may be controlled in response to a phase inversion control signal generated based on one or more parameters such as temperature. The secondary signal path may also include separate distortion sub-paths to produce frequency independent distortion products and frequency dependent distortion products.

Abstract: The present invention relates to an optical modulation method and optical modulation system of a wavelength locked Fabry Perot-Laser Diode (FP-LD) by injecting a broadband light source (BLS) using mutual injection of FP-LDs. More specifically, the present invention relates to a novel modulation technology which embodies a wavelength locked FP-LD capable of being used as an economic light source in an optical network based on a wavelength-division multiplexing passive optical network (WDM-PON).

Abstract: A circuit controlling the gain of an amplifier in an optical transmitter used for optical communication, including a detection circuit for measuring the power of the RF input to a laser; a gain controller or controlling a gain of an amplifier, and a switch connected to the gain controller, wherein the gain controller is adapted, in response to an activation of a switch, to: (i) automatically vary gain of the amplifier, and (ii) set the gain of the amplifier at a level corresponding to a reduction in the noise and/or distortion associated with the transmitter.

Abstract: A fiber-optic transmission system includes a transmitter having a designed chirp value. The transmitter has first and second inputs for receiving first and second input signals, respectively, used to produce a modulated output signal. An optical fiber is responsive to the transmitter for receiving the output signal. A circuit asymmetrically drives the first and second input signals so as to change the designed chirp value of the transmitter to another value. Methods of controlling the chirp of a commercially available transmitters are also disclosed. Because of the rules governing abstracts, this abstract should not be used to construe the claims.

Abstract: A system includes a laser generator, and a signal distortion generator circuit inline with the laser generator modulation signal and configured to generate distortion vectors in any of four distortion vector quadrants.

Abstract: Linearized optical transmitter units are described for a hybrid optical fiber coaxial cable network. The linearized optical transmitter unit can comprise a directly-modulated or externally-modulated laser optically coupled to an optical conduit directed to an optical fiber communications link and electrically coupled to an electrical RF source line that provides an RF source to drive the laser or an external modulator for a light beam from the laser. A linearization information electrical component comprising memory and/or a processor, and a data output configured to transmit linearization enabling data for input into a direct digital synthesis engine that enables the direct digital synthesis engine to generate an RF signal wherein nonlinear responses of the transmitter and/or the optical fiber communications link are pre-compensated, in which the data is specific for the optical transmitter and/or the optical fiber communications link.

Abstract: The present invention provides byte-interleaving systems and methods for Optical Transport Unit N (OTUN) (i.e. Optical Transport Unit 4 (OTU4)) and 100 Gb/s (100 G) optical transport enabling multi-level optical transmission. The byte-interleaving systems and methods of the present invention support the multiplexing of sub-rate clients, such as 10 Gb/s (10 G) clients, 40 Gb/s (40 G) clients, etc., into two 50 Gb/s (50 G) logical flows, for example, that can be forward error correction (FEC) encoded and carried on a single wavelength to provide useful, efficient, and cost-effective 100 G optical transport today. Signaling format support allows these two 50 G logical flows to be forward compatible with an evolving OTU4 and 100 G signaling format without waiting for optical and electronic technology advancement. Signaling format support also allows an evolving standard 100 G logical flow (i.e. OTU4, 100 Gb/s Ethernet (100 GbE), etc.

Abstract: An optical transceiver and a method to setup the optical transceiver are disclosed, where the transceiver has a function to compensate the distortion and the dispersion due to the limited bandwidth of the electrical signal line, that of the active devices, and that of the optical fiber. The optical transceiver comprises a transmitter with an equalizer unit and a receiver also with an equalizer unit. The equalizer unit in the transmitter compensates the distortion due to the limited bandwidth of the transmission lines for the electrical signal and that of the semiconductor active device, while, the equalizer unit in the receiver compensates the dispersion due to the limited bandwidth of the optical fiber.

Abstract: The present invention relates to pre-distortion in transmitter circuits and provides a circuit for introducing pre-distortion into the output of a transmitter, wherein said pre-distortion comprises a pre-cursor, a cursor and a post-cursor, the circuit comprising: a first driver arranged to switch an output drive between said pre-cursor and said cursor; a second driver arranged to switch an output drive between said post-cursor and said cursor; a third driver arranged to switch an output drive between a positive cursor drive and a negative cursor drive. The arrangement provided give flexibility when setting the pre-cursor, cursor and post-cursor levels.