Abstract: An optical signal transmission can use probabilistically shaped technique to improve performance and increase the transmission capacity. For instance, a 30-Gbit/s/? probabilistically shaped (PS) 1024-QAM DFT-S OFDM was experimentally demonstrated over 40-km SSMF in an intensity modulation-direct detection system. The Achievable Information Rate (AIR) 9.5344-bits/QAM symbol of PS-1024-QAM modulation is first achieved in the experiment and shows feasibility for OFDM.

Abstract: A digital communication technique, implementable in a digital communication system, includes performing a training phase in which the transmitter sends one or more transmissions of pulse amplitude modulation (PAM) signals wherein the PAM signals are modulated using one or more data-to-PAM-symbol mapping schemes, performing a feedback phase in which the transmitter receives a feedback message from a receiver, the feedback message indicative of a change to be made to data-to-PAM-symbol modulation schemes, and implementing a data transmission phase in which data is transmitted using a current PAM symbol mapping scheme based on the feedback message, wherein at least some symbols of the current PAM symbol modulation scheme are unequally spaced with respect to each other.

Abstract: Methods and systems for optical signal transmission, particularly with carrier-less amplitude and phase (CAP) modulation and direct detection, are disclosed. In one exemplary aspect, a method of optical signal transmission is disclosed. The method includes receiving information bits at an input interface; mapping the information bits to a plurality of modulation symbols; separating in-phase (I) and quadrature (Q) components of the plurality of modulation symbols such that the I and Q components form a Hilbert pair in a resulting signal; pre-dispersing the resulting signal with an inverse of a phase delay of an expected chromatic dispersion to obtain a pre-dispersed signal; converting the pre-dispersed signal from digital domain to analog domain using a digital to analog conversion circuit; performing modulation of an output of the digital to analog conversion circuit to generate an output signal; and transmitting, over an optical transmission medium, the output signal from the modulation.

Abstract: A lifting table includes a lifting mechanism, a base, an upper tabletop and a tabletop mounting frame assembly; the lifting mechanism includes a plurality sections of lifting columns and a controller, and the lifting columns are matched and connected with one another; the base is installed at a bottom of the lifting mechanism, the controller is hidden in the base and connected with buttons on the tabletop mounting frame assembly; the upper tabletop and the tabletop mounting frame assembly are both installed on lifting columns, and the tabletop mounting frame assembly is located below the upper tabletop; through selection of buttons on the tabletop mounting frame assembly, a signal is sent to the controller so that the controller drives the lifting columns to stretch out or draw back and hence to drive the upper tabletop and the tabletop mounting frame assembly to raise up or lower down.

Abstract: A digital communication technique, implementable in a digital communication system, includes performing a training phase in which the transmitter sends one or more transmissions of pulse amplitude modulation (PAM) signals wherein the PAM signals are modulated using one or more data-to-PAM-symbol mapping schemes, performing a feedback phase in which the transmitter receives a feedback message from a receiver, the feedback message indicative of a change to be made to data-to-PAM-symbol modulation schemes, and implementing a data transmission phase in which data is transmitted using a current PAM symbol mapping scheme based on the feedback message, wherein at least some symbols of the current PAM symbol modulation scheme are unequally spaced with respect to each other.

Abstract: Embodiments of the present invention pertain to optical wireless architecture. More particularly, certain embodiments of the invention pertain to a novel method and apparatus to generate millimeter-wave signals with simple and/or low cost architecture. Simple millimeter-wave generation and dispersion-tolerant transmission is based on photonic mixing of two free-running lightwaves and self-mixing down-conversion. More particularly, heterodyne mixing of two free run lightwaves is achieved, wherein one lightwave is modulated by an external modulator driven by electrical data as one of the side-bands of a millimeter-wave signal. Optical to electrical conversion is performed and the millimeter-wave signal is broadcasted by a high-frequency antenna to a receiving side having a local oscillator with self-mixing architecture to down-convert the radio frequency to its baseband form.

Abstract: A scheme for generating, transmitting and receiving dual-polarization asymmetric single sideband photonic vector signal at millimeter wave spectral region is described. At a transmitter, information bits to be transmitted are modulated using a vector modulation technique to generate a baseband signal. The baseband signal is converted into its single sideband (SSB) version using a complex frequency source having a first frequency. Two IQ signals are generated using an integrated dual polarization IQ modulator. The I/Q modulator is driven by a laser source at frequency fc. The resulting signal is transmitter over an optical transmission medium and/or a multi-input, multi-output over the air antenna configuration, upconverted by a single-ended photodiode to a desired radio-frequency (RF) carrier frequency.

Abstract: An optical transmitter multiplexes multiple optical channels for transmission over an optical communication medium. The spectrum of modulated signal in each optical channel is lowpass filtered in the electrical (digital) domain at half the channel baud rate such that super Nyquist signal multiplexing can be achieved in the optical domain without having to perform optical filtering. An optical coupler may be used to multiplex the multiple optical channels.

Abstract: A scheme for generating asymmetric single sideband photonic vector signal at millimeter wave spectral region is described. At a transmitter, information bits to be transmitted are modulated using a vector modulation technique to generate a baseband signal. The baseband signal is converted into its single sideband (SSB) version using a complex frequency source having a first frequency. The real part of the upconverted signal is added to the real part of a second frequency source and is input as I component to an I/Q modulator. The imaginary part of the upconverted signal is added to the imaginary part of the second frequency source and is used as the Q component. The I/Q modulator is driven by a laser source at frequency fc. The resulting signal is transmitter over an optical transmission medium and upconverted by a single-ended photodiode to a desired radio-frequency (RF) carrier frequency.

Abstract: Throughput between a transmitter and a receiver is increased by performing a three-stage joint channel optimization in which training sequences are used for calculating a pre-equalization estimate in the first stage, a look up table for pre-distortion in the second stage and a further updating the pre-equalization estimate and the look up table based on a third stage in which the training sequence used for the updating is pre-equalized and pre-distorted using previously calculated values prior to transmitting from the transmitter to the receiver.

Abstract: A method of optical communication, implemented at a receiver in an optical communication network, includes receiving an optical signal carrying modulated information bits, processing the optical signal through a receiver subsystem to generate a stream of digitized modulation symbols from the optical signal, and producing, using the digitized modulation symbols as input symbols to an iterative process, estimates of information bits. Each iteration includes: generating estimated output symbols from input symbols by filtering by an estimate of inverse of the optical channel, updating, using the estimated output symbols, the estimate of the inverse of the optical channel to minimize a measure of error, and compensating the estimated output symbols by using pre-distortion values from a look-up table (LUT) to generate compensated output symbols that are used as input to a next iteration.

Abstract: An exemplary technique of optical signal transmission in which modulated optical signals are generated using photonic heterodyne beating and operating a digital to analog converter at baseband includes receiving information bits, modulating the information bits to generate a precoded vector signal at baseband, generating, using photonic heterodyne beating, from the precoded vector signal at baseband, a precoded vector signal at an upconverted frequency, and transmitting the precoded vector signal at the upconverted frequency on the optical communication network.

Abstract: Methods and apparatus to realize high spectral efficiency in optical signals transmitted over long distances.

Abstract: In an optical communication system, an optical transmitter changes operational physical layer parameters to meet future target throughput for the optical communication system. The optical transmitter communicates the upcoming change to the optical receiver in a message that used current physical layer parameters. The optical transmitter provides sufficient time to the optical receiver to adjust reception functions of the receiver, including polarization based demodulation scheme. In some implementations, the optical transmitter performs the transition to a new physical layer transmission format without waiting for an acknowledgement from the optical receiver.

Abstract: A method of digital communication is described. The method includes generating a first orthogonal frequency division multiplexed (OFDM) signal from a first portion of information bits received at the communication apparatus, generating a second OFDM signal from a second portion of information bits received at the communication apparatus, generating a first input for a modulator using the first OFDM signal and the second OFDM signal, generating a second input for the modulator using the second OFDM signal and the second OFDM signal, and operating the modulator to produce a modulated signal from the first input and the second input.

Abstract: An optical signal transmission can use probabilistically shaped technique to improve performance and increase the transmission capacity. For instance, a 30-Gbit/s/?, probabilistically shaped (PS) 1024-QAM DFT-S OFDM was experimentally demonstrated over 40-km SSMF in an intensity modulation-direct detection system. The Achievable Information Rate (AIR) 9.5344-bits/QAM symbol of PS-1024-QAM modulation is first achieved in the experiment and shows feasibility for OFDM.

Abstract: An optical signal transmitter produces optical signals comprising QAM modulated vector signals generated using a single external electro-optical modulator operated in conjunction with a wavelength selective switch. The transmission processing achieves adaptive photonic frequency multiplication and comprises QAM modulated signals with high order constellations such as 8-QAM, 16-QAM, 32-QAM and 64-QAM.

Abstract: A novel and simple photonic vector signal generation scheme at radio frequency (RF) bands enabled by a single-drive Mach-Zehnder modulator (MZM)-based optical carrier suppression (OCS) without precoding techniques and optical filter, which can reduce the complexity of transmitter digital signal processing (DSP), is described. The generation and reception of 16/20/22-Gbaud quadrature-phase-shift-keying (QPSK) vector signals at 16/20/22 GHz are experimentally demonstrated, respectively. The measured bit-error ratio for 16G-baud QPSK vector signals after transmitting over 10-km standard single mode fiber (SSMF) can be under 7% hard-decision forward-error-correction (HD-FEC) threshold of 3.8×10?3. Moreover, compared to the conventional precoding scheme, the receiver sensitivity can be enhanced by 4 dB at both back-to-back (BTB) and after 10-km SSMF transmission cases, which demonstrates the feasibility of this technique, and show its potential promising application in radio over fiber (RoF) system.

Abstract: A method and apparatus for generating sub-carriers is disclosed. Coherent optical sub-carriers with sub-carrier spacing are generated for carrying an orthogonal frequency division multiplexed (OFDM) signal. Multiple peaks are generated by cascading multiple phase modulators driven by different radio frequency sources.

Abstract: Provided are methods and systems for receiving and processing optical signals. A dual single side band (SSB) modulation scheme is utilized to take advantage of a given wavelengths' bandwidth. Modulation schemes are employed that modulate each SSB with their In-phase (I) and Quadrature (Q) components. The methods and systems discussed utilize an adaptive equalizer and an LMS algorithm to remove imaging components of the left and right SSBs provided by the modulators. The adaptive equalizer and the LMS algorithm also compensate for linear and nonlinear distortions. Various algorithms can be employed, including but not limited to, algorithms for updating crosstalk coefficients in the equalizer, where the cross talk coefficients are induced from the imaging from the modulation of the dual SSB signal, and for updating coefficients relating to linear and nonlinear distortion.