Abstract: Aspects of the invention provide transmitters and receivers for managing multiple optical signals. High order modulation, such as phase and/or amplitude modulation, is used to achieve multiple bits per symbol by transporting multiple asynchronous data streams in an optical transport system. One or more supplemental multiplexing techniques such as time division multiplexing, polarization multiplexing and sub-carrier multiplexing may be used in conjunction with the high order modulation processing. This may be done in various combinations to realize a highly spectrally efficient multi-data stream transport mechanism. The system receives a number of asynchronous signals which are unframed and synchronized, and then reframed and tagged prior to the high order modulation. Differential encoding may also be performed. Upon reception of the multiplexed optical signal, the receiver circuitry may employ either direct detection without a local oscillator or coherent detection with a local oscillator.

Abstract: A method is provided for performing chromatic dispersion (CD) pre-compensation. The method generates an electronic signal at a transmitter, and uses a transmit CD compensation estimate to compute a CD pre-compensation filter. The transmit CD pre-compensation filter is used to process the electronic signal, generating a pre-compensated electronic signal. The pre-compensated electronic signal is converted into an optical signal and transmitted to an optical receiver via an optical channel. In one aspect, the transmitter generates a test electronic signal and the CD compensation estimate uses a first dispersion value to compute a first CD compensation filter. The transmitter accepts a residual dispersion estimate of the test optical signal from the first optical receiver CD compensation filter, generated from a (receiver-side) CD estimate, and then the transmit CD estimate can be modified in response to the combination of the first dispersion value and residual dispersion estimate.

Abstract: A system, e.g. for optical communication, includes an I-Q modulator and a transmission signal processor. The I-Q modulator is configured to modulate a first light source in response to first I and Q modulation signals. The transmission signal processor is configured to receive a data stream including data corresponding to a first data subchannel. The processor maps the data subchannel to an optical transmission subchannel and outputs the first I and Q modulation signals. The I and Q modulation signals modulate the light source to produce an optical transmission signal that includes wavelength components corresponding to the optical transmission subchannel.

Abstract: A system and method for improving receiver sensitivity of an DD-OFDM system without using frequency guard band. The method having: interleaving input data to the DD-OFDM system to generate interleaved data; encoding the input data with a first recursive systematic convolutional code to generate a first recursive systematic convolutional encoded data; encoding the interleaved data with a second recursive systematic convolutional code to generate a second recursive systematic convolutional encoded data; puncturing the first recursive systematic convolutional encoded data and the second recursive systematic convolutional encoded data to generate a parity sequence; and combining the input data with the parity sequence to generate coded DD-OFDM data; wherein the parity sequence is generated by using different puncturing rates for different OFDM subcarriers, so as to obtain higher spectral efficiency.

Abstract: A system for generating a frequency modulated linear laser waveform includes a single frequency laser generator to produce a laser output signal. An electro-optical modulator modulates the frequency of the laser output signal to define a linear triangular waveform. An optical circulator passes the linear triangular waveform to a band-pass optical filter to filter out harmonic frequencies created in the waveform during modulation of the laser output signal, to define a pure filtered modulated waveform having a very narrow bandwidth. The optical circulator receives the pure filtered modulated laser waveform and transmits the modulated laser waveform to a target.

Abstract: A distortion compensation circuit compensates for distortion generated by one or more non-linear elements such as a laser device and/or an optical fiber and may include a primary signal path for carrying an input signal and a secondary signal paths for generating distortion. The distortion compensation circuit may also include a controllable phase inverters and a tunable filter. 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 and a tunable filter that adjusts the phase of the frequency dependent distortion. The phase inversion and tunable filter may be controlled in response to control signals generated based on one or more parameters such as, for example, laser power, input RF channel loading, temperature, and fiber length.

Abstract: The present invention provides a wavelength division multiplexing system and a method and device for its residual dispersion compensation, wherein the device for residual dispersion compensation of wavelength division multiplexing system comprises: a performance parameter detecting device for receiving and detecting performance parameter of receiving terminal optical signal and sending detecting result of the performance parameter to a central control device; the central control device for deciding a dispersion regulating mode of a tunable dispersion compensator according to the detecting result of the performance parameter and sending the dispersion regulating mode to a tunable dispersion compensator control device through control signaling; and the tunable dispersion compensator control device for receiving the control signaling sent by the central control device and adjusting dispersion compensation amount of the tunable dispersion compensator according to the control signaling in order to make residual di

Abstract: An optical transmitter may include an optical source to provide a first optical signal having a varying frequency; an optical circuit to receive a portion of the first optical signal and provide a second optical signal corresponding to a change in frequency of the first optical signal; a photodetector to receive the first optical signal and provide an electrical signal that is indicative of the change in frequency of the first optical signal; an integrator to receive the electrical signal and provide an inverted electrical signal; and a controller to process the inverted electrical signal and provide a current, associated with the inverted electrical signal, to the optical source. The optical source may reduce the phase noise associated with the first optical signal based on the current.

Abstract: An optical transmitter includes: a digital signal processor to generate a drive signal from input data; a controller to control an amplitude or power of the drive signal according to information relating to the digital signal processing of the digital signal processor; and an optical modulator to modulate input light with the drive signal controlled by the controller to generate an optical signal.

Abstract: An optical network and 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, signaling the first transceiver to change its compensation function. The signaling 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: 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: A method for generating a 400 Gb/s single channel optical signal from multiple modulated subchannels includes carving respective modulated subchannels into return-to-zero RZ modulated subchannels having non-overlapping peaks with intensity modulators having a duty cycle less than 50%, and combining the subchannels into a single channel signal aggregating the bit rate of each of the subchannels. The subchannels are combined with a flat top optical component for increased subsequent receiver sensitivity.

Abstract: An optical transmission apparatus includes an optical transmitter that outputs a signal light corresponding to a wavelength of a WDM light, a multiplexer that multiplexes lights input to the plurality of input ports, and that outputs a light generated through the multiplexing from the one or more output port, an optical amplifier that amplifies the light output from the multiplexer; and an amplified spontaneous emission (ASE) transmitter that inputs branching off part of the light output from the optical amplifier by a splitter and multiplexes, with the signal light, ASE in a wavelength band corresponding to an unused wavelength adjacent to the signal light included in the branched-off light.

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: An efficient baseband predistortion linearization method for reducing the spectral regrowth and compensating memory effects in wideband communication systems using effective multiplexing modulation technique such as wideband code division multiple access and orthogonal frequency division multiplexing is disclosed. The present invention is based on the method of piecewise pre-equalized lookup table based predistortion, which is a cascade of a lookup table predistortion and piecewise pre-equalizers.

Abstract: There are various drawbacks by using existing OTN (Optical Transport Network) frames for communication between OTN cards. Such drawbacks might for example include high latency, low robustness, and/or high coding rate. According to embodiments of the present disclosure, systems and methods are provided for modifying an OTN frame (or creating a new frame with data from the OTN frame) prior to transmission by an OTL (Optical channel Transport Lane) in order to address some or all of the foregoing drawbacks. Note that this embodiment can make use of existing hardware (e.g. hardware used for generating the OTN frame, and the OTL used for transmission).

Abstract: A system for suppressing even-order distortion in a photonic link includes a laser for providing laser light to a first input of a Mach-Zehnder modulator (MZM), where the MZM has a second input for receiving an RF input signal, a third input for applying a DC bias voltage to the MZM, and an optical signal output. A dc-voltage-biased photodiode has an input, coupled to the MZM optical signal output, and a modulated RF signal output. The MZM DC bias voltage is set at a value to generate an even-order distortion amplitude substantially equal to an even-order distortion amplitude from the photodiode and 180 degrees out of phase so as to substantially cancel the photodiode even-order distortion. The invention provides the cancellation of photodiode even-order distortion via predisortion linearization with a MZM biased slightly away from quadrature, employing a single fiber run and a single photodiode. The invention provides an improvement in carrier-to-intermodulation ratio (CIR) upwards of 40 dB.

Abstract: For providing circuit arrangement and method for transmitting signals from a data source to a data sink, the signals being TMDS encoded, the driver circuit is supplied by a connection interface, connected upstream, assigned to data source, with supply voltage, electrical TMDS encoded signals are electro-optically converted by an LED connected downstream of the driver circuit and coupled into an optical fiber as light supplied with TMDS encoded signals, the direct current portion supplied from TMDS transmitter to connection interface, to data source, is converted by driver circuit to a modulated signal current for controlling LED.

Abstract: A wireless transmitter is disclosed that is capable of pre-compensating for oscillator phase noise. In the transmitter, an undesired phase noise being generated by a voltage-controlled oscillator can be detected by comparing the output of the voltage-controlled oscillator to a reference oscillator output. The phase can then be detected by calculating a desired number of zero crossings over a given time period, and comparing this value to an actual number of zero crossings detected in the signal generated by the voltage-controlled oscillator over the same period. From this, the phase component can be determined and digitally pre-compensated in a data signal.

Abstract: A modulation method, especially an optical modulation method, using the principle of discrete IQ modulation. The modulation method includes generating a carrier signal (Sc) and splitting the carrier signal at a splitting position in an I branch signal and a Q branch signal; modulating the amplitude of the I branch signal according to a first modulation signal and modulating the amplitude of the Q branch signal according to a second modulation signal, each of the first and second modulation signals being arranged to adopt a given number of values according to a given number of constellation points of a given modulation scheme; phase shifting the signal in the Q branch versus the signal in the I branch; and combining the signals in the I branch and Q branch at a combining position. The combined modulated signal (Stx,mod) is arranged to be transmitted over a transmission path.

Abstract: The present disclosure provides electrical domain suppression of linear crosstalk in optical communication systems using single-carrier implementations. This electrical domain suppression applies spectral shaping in the electronic radio frequency (RF) domain. Advantageously, spectral shaping in the electronic RF domain transfers system complexity from the bulk optical domain into the highly integrated CMOS (or equivalent) domain. The spectral shaping can include electronic circuitry including an electrical filtering block and a signal linearization block prior to optical modulation. The electrical filtering block suppresses coherent interference terms and can include an RF-domain low pass filter. The signal linearization block linearizes modulator response to compensate spectral regrowth due to nonlinear mixing in the modulator.

Abstract: A system for transmitting an optical signal over a fiber optic includes a terminal for generating the optical signal. Due to its modulation, the optical signal includes a carrier having a wavelength “?”, with an upper sideband and a lower sideband. A tuner is connected with the terminal to adjust the wavelength “?” of the carrier of the optical signal relative to a band pass filter. The purpose here is two-fold. For one, this adjustment eliminates a sideband of the optical signal, to avoid fading, and it suppresses the carrier of the optical signal, to enhance the OMI while maintaining the linearity of the signal.

Abstract: An optical transmission and reception system in which a plurality of tributary signals are converted into multilevel modulated light for transmission and reception. An apparatus for transmitting multilevel modulated light includes: FECs which perform error correction processing including addition of a tributary identifier; and a GEAR BOX which performs rate conversion on the processed signals.

Abstract: In one example embodiment, a transmitter module includes a header electrically coupled to a chassis ground. First and second input nodes are configured to receive a differential data signal. A buffer stage has a first node coupled to the first input node and a second node coupled to the second input node. An amplifier stage has a fifth node coupled to a third node of the buffer stage and a sixth node coupled to a signal ground that is not coupled to the chassis ground. An optical transmitter has an eighth node coupled to a seventh node of the amplifier stage and a ninth node configured to be coupled to a voltage source. A bias circuit is configured to couple a fourth node of the buffer stage to a bias current source.

Abstract: [PROBLEM] Providing an optical source that outputs optical frequency modulated light having a constant output optical intensity. [MEANS FOR SOLVING THE PROBLEM] Provided is a light source apparatus that outputs an optical signal having an optical frequency corresponding to a frequency control signal, the light source apparatus including a laser light source section that outputs laser light having an optical frequency corresponding to the frequency control signal; and an optical intensity adjusting section that compensates for intensity change of the laser light to output laser light in which the intensity change caused by a change in the optical frequency is restricted.

Abstract: A dispersion correction circuit is provided for use with an input driving signal. The dispersion correction circuit includes an input portion an output portion and a filter portion. The input portion is arranged to receive the input driving signal. The output portion can output an output signal based on the input driving signal. The filter portion is disposed between the input portion and the output portion. The filter portion includes a first varactor, a DC bias portion, and a second varactor. The DC bias portion provides a DC bias to the first varactor. The first varactor is arranged in a first polarity direction, and the second varactor is arranged in a second polarity direction that is the same as the first direction.

Abstract: A driver circuit configured to generate a drive signal for an optical source comprises an overshoot controller that provides an amount of overshoot for a given logic state of the drive signal as a function of a duration of at least one previous logic state of the drive signal. The drive signal may alternate between a first logic state associated with a first operating mode of the optical source and a second logic state associated with a second operating mode of the optical source. The overshoot controller may be configured to provide amounts of overshoot for respective instances of the first logic state that are proportional to the durations of their respective immediately preceding second logic states. The driver circuit may be implemented in a heat-assisted magnetic recording system in which the optical source alternates between on and off states associated with respective magnetic write and magnetic read modes.

Abstract: Provided is an optical module. The optical module includes: an optical bench having a first trench of a first depth and a second trench of a second depth that is less than the first depth; a lens in the first trench of the optical bench; at least one semiconductor chip in the second trench of the optical bench; and a flexible printed circuit board covering an upper surface of the optical bench except for the first and second trenches, wherein the optical bench is a metal optical bench or a silicon optical bench.

Abstract: An optical transmission apparatus includes an interleaver configured to filter an optical carrier, a multiplexer configured to combine lights output from the interleaver to generate a composite light, a monitor configured to monitor a light intensity of the composite light, and a control circuit configured to change a grid spacing in a filter characteristic of the interleaver in a direction in which an amount of change in a light intensity of the composite light increases, on the basis of a monitoring result measured while changing a center frequency in the filter characteristic of the interleaver and to change the center frequency in the filter characteristic in a direction in which a maximum value of the light intensity increases, on the basis of the monitoring result.

Abstract: A high-speed signal generator. A digital signal processing (DSP) block generates a set of N (where N is an integer and N?2) parallel digital sub-band signals, each digital sub-band signal having frequency components within a spectral range between 0 Hz and ±Fs/2, where Fs is a sample rate of the digital sub-band signals. A respective Digital-to-Analog Converter (DAC) processes each digital sub-band signal to generate a corresponding analog sub-band signal, each DAC having a sample rate of Fs/2. A combiner combines the analog sub-band signals to generate an output analog signal having frequency components within a spectral range between 0 Hz and ±NFs/2.

Abstract: A dispersion correction circuit is provided for use with an input driving signal. The dispersion correction circuit includes an input portion, an output portion and a filter portion. The input portion is arranged to receive the input driving signal. The output portion can output an output signal based on the input driving signal. The filter portion is disposed between the input portion and the output portion. The filter portion includes a varactor, a DC bias portion, and a transformer. The DC bias portion provides a DC bias to the varactor.

Abstract: Various embodiments are directed to a photonic impulse generator comprising a periodically chirped photonic source a single-frequency photonic source, a photodetector, an optical coupler, and a filter. The optical coupler may be positioned to couple an output of the single-frequency photonic source to an output of the periodically chirped photonic source, resulting in a combined photonic signal. The photodetector may be positioned to receive the combined photonic signal and generate a combined electrical signal. The filter may be in electrical communication with an output of the photodetector to receive the combined electrical signal.

Abstract: In order to reduce the circuit size for a chromatic dispersion pre-equalization operation, an optical multilevel signal pre-equalization circuit is provided with: (1) a plurality of look-up tables in which a string of middle codes utilizing a symmetry of a signal constellation of a multilevel code or a string of middle codes represented by polar coordinates is stored in association with a waveform response component; and (2) one or more operation circuits to which the waveform response component corresponding to a multilevel signal to be transmitted is inputted from the plurality of look-up tables, and which outputs a pre-equalized output waveform corresponding to the multilevel signal by operating the waveform response components outputted from different look-up tables.

Abstract: A method and apparatus for modeling distortion of a non-linear device are disclosed. A pre-distorter model has a plurality of branches. Each branch receives a different output basis function signal. At least one branch includes a down-sampler, a memory structure and an up-sampler. The down-sampler down-samples the received output basis function signal received by the branch by a factor of 1/Mk, where Mk is different for each of the at least one branches. The memory structure includes at least one delay element to delay the output of the down-sampler according to a predetermined delay. The memory structure has an output based on an output of the at least one delay element. The up-sampler up-samples the output of the memory structure by the up-sampling factor, Mk.

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: An optical transmitter for converting an input data series into an optical multi-level signal and for outputting the same, includes an LUT in which data for executing optical multi-level modulation is stored and from which first modulation data and second modulation data are output based on the input data series. A DAC converts the first modulation data by D/A conversion to generate a first multi-level signal. A DAC converts the second modulation data by D/A conversion to generate a second multi-level signal. A dual-electrode MZ modulator includes a first phase modulator for modulating light from a light source in accordance with the first multi-level signal and a second phase modulator for modulating light from the light source in accordance with the second multi-level signal, and combines an optical signal from the first phase modulator and an optical signal from the second phase modulator to output the optical multi-level signal.

Abstract: A driver for shaping a drive signal includes a pre-emphasis circuit, an offset adjustment circuit, and an amplifier. The pre-emphasis circuit symmetrically emphasizes a rising edge portion and a falling edge portion of the drive signal. The offset adjustment circuit applies a direct-current offset to the drive signal. The amplifier amplifies the drive signal with the direct-current offset adjusted by the adjustment circuit. The amplifier has an input-output characteristic with a nonlinear portion. The offset adjustment circuit adjusts the direct-current offset so that the drive signal is amplified in the nonlinear portion.

Abstract: The present invention provides an optical communication method, comprising: performing modulation on the obtained bit stream data to generate modulated signals; performing differential encoding on the modulated signals to generate differentially encoded signals; converting the differentially encoded signals into electrical signals; and mapping the electrical signals onto optical carriers to generate optical signals for transmission. With the present invention, it is possible to enhance the system's capability of resisting inter-carrier interference without decreasing spectrum efficiency, hence improving the tolerance of existing optical communication systems towards laser linewidth, fast-changing PMD, optical fiber nonlinearity, inter-channel interference and other damages, greatly enhancing system performances.

Abstract: An optical packet signal transmission device includes a transmitting unit which includes a plurality of data delay circuits; a plurality of optical branch units which branches some of the optical packet signals as monitor lights; an optical switch which selects one of the monitor lights; a test signal generation circuit which generates a test signal which is used to adjust a delay amount in the data delay circuits; a reference optical pulse generation circuit which generates a reference optical pulse based on the test signal; an optical phase comparator which detects an relative optical phase difference by comparing the phases of the selected monitor light and the reference optical pulse; and a control circuit which sequentially sends the test signals to the data delay circuits, switches the selected monitor light, detects a relative optical phase, determines the delay amount based on a detection result, and sets the delay amount.

Abstract: To efficiently apply jitter to an optical signal using a simple configuration, provided is an optical signal output apparatus that outputs an optical pulse pattern signal including jitter, the optical signal generating apparatus comprising a light source section that outputs an optical signal having an optical frequency corresponding to a frequency control signal; an optical modulation section that modulates the optical signal output by the light source section, according to a designated pulse pattern; and an optical jitter generating section that delays an optical signal passed by the optical modulation section according to the optical frequency, to apply jitter to the optical signal.

Abstract: Aspects of the invention provide transmitters and receivers for managing multiple optical signals. High order modulation, such as phase and/or amplitude modulation, is used to achieve multiple bits per symbol by transporting multiple asynchronous data streams in an optical transport system. One or more supplemental multiplexing techniques such as time division multiplexing, polarization multiplexing and sub-carrier multiplexing may be used in conjunction with the high order modulation processing. This may be done in various combinations to realize a highly spectrally efficient multi-data stream transport mechanism. The system receives a number of asynchronous signals which are unframed and synchronized, and then reframed and tagged prior to the high order modulation. Differential encoding may also be performed. Upon reception of the multiplexed optical signal, the receiver circuitry may employ either direct detection without a local oscillator or coherent detection with a local oscillator.

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: Transmitters for data communication can include a pattern generator configured to generate parallel data stream composed of k bits, k being a natural number greater than 2, a serializer configured to convert the parallel data stream into a serial data stream, a pre-emphasis circuit configured to pre-emphasize the serial data stream based on a pre-emphasis control value, to transmit the pre-emphasized serial data stream to a receiver via a first transmission line, and a pre-emphasis controller configured to receive measured values of transmission errors of the pre-emphasized serial data stream from the receiver via a second transmission line, and configured to set the pre-emphasis control value corresponding to a minimum measured value of the transmission errors, to an optimum pre-emphasis control value.

Abstract: A system and method for optimizing an optical RF photonic link system is presented. The system comprises a modulator subsystem in which nonlinear response is compensated by an envelope precompensation method and employs an optical filter to suppress optical carriers and extract modulated sidebands, an optical amplifier, and an array of photodetectors, each having a plurality of pairs of diodes. The modulator subsystem performs optical filtering on the signal, the signal is amplified by the optical amplifier and sent to the array of photodetectors. The optical amplifier can be an erbium doped fiber amplifier, or a phase sensitive amplifier. The optical power can be delivered to each diode of the array of photodetectors via a photonic integrated circuit.

Abstract: A vector sum phase shifter includes a 90° phase shifter (1) which generates an in-phase signal (VINI) and a quadrature signal (VINQ) from an input signal (VIN), a four-quadrant multiplier (2I) which changes the amplitude of the in-phase signal (VINI) based on a control signal (CI), a four-quadrant multiplier (2Q) which changes the amplitude of the quadrature signal (VINQ) based on a control signal (CQ), a combiner (3) which combines the in-phase signal (VINI) and the quadrature signal (VINQ), and a control circuit (4). The control circuit (4) includes a voltage generator which generates a reference voltage, and a differential amplifier which outputs the difference signal between a control voltage (VC) and the reference voltage as the control signal (CI, CQ). The differential amplifier performs an analog operation of converting the control voltage (VC) into the control signal (CI, CQ) similar to a sine wave or a cosine wave.

Abstract: Multimode optical fiber systems with adjustable chromatic modal dispersion compensation are disclosed, wherein the system includes a VCSEL light source and primary and secondary optically coupled multimode optical fibers. Because the VCSEL light source has a wavelength spectrum that radially varies, its use with the primary multimode optical fiber creates chromatic modal dispersion that reduces bandwidth. The compensating multimode optical fiber is designed to have a difference in alpha parameter relative to the primary multimode optical fiber of ?0.1?????0.9. This serves to create a modal delay opposite to the chromatic modal dispersion. The compensation is achieved by using a select length of the compensating multimode optical fiber optically coupled to an output end of the primary multimode optical fiber. The compensating multimode optical fiber can be configured to be bend insensitive.

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: A reconfigurable polarity detachable connector assembly includes a housing defining two accommodation channels and providing a springy protruding member at a top side, two mating simplex connectors respectively detachably mounted in the accommodation channels of the housing, a fiber optic cable fastened to the housing with two optical fiber cores thereof respectively inserted into respective calibration support rods of the mating simplex connectors, and a sliding cap slidably coupled to the housing. The sliding cap is unlocked and can be moved backwardly relative to the housing to expose the optical fiber cores of the fiber optic cable to the outside of the housing for allowing position exchange between the two mating simplex connectors after the user presses the springy protruding member.

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: A non-linear power amplifier generates an amplified output signal based on a pre-distorted signal generated by a digital pre-distorter (DPD) based on an input signal. A feedback path generates a feedback signal based on the amplified output signal. The feedback signal is aligned with the input signal, or vice versa, and the aligned signals are used to adaptively update the DPD processing. In particular, a linear FIR filter is estimated to minimize a cost function based on the input and feedback signals. Depending on how the filter is generated, the filter is applied to the input signal or to the feedback signal to generate the aligned input and feedback signals.