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 optical signal transmission can use probabilistically shaped technique to improve performance and increase the transmission capacity. For instance, a 30-Gbit/s/λ, 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:
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.
Abstract:
At a transmitter-side in an optical communication network, pulse amplitude modulation optical signals to be transmitted are pre-compensated using a chromatic dispersion pre-compensation stage and a device non-linearity pre-compensation stage. The non-linearity pre-compensation may be achieved by using look-up tables that are built based on messages exchanged between the transmitter and a target receiver using known symbol patterns.
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:
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.
Abstract:
A dual-polarization, 2-subcarriers code orthogonal, orthogonal frequency division multiplexed signal carrying information bits is transmitted in an optical communication network without transmitting a corresponding pilot tone or training sequence. A receiver receives the transmitted signal and recovers information bits using a blind equalization technique and by equalizing the 2-subcarriers OFDM signal as a 49-QAM signal in time domain with a CMMA (constant multi modulus algorithm) equalization method.
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 16 G-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:
Duo-binary encoding is used for encoding I and Q data prior to performing orthogonal frequency division multiplexing based transmission using discrete Fourier transform spreading (DFT-S). Advantageously, duo-binary encoding improves robustness of the encoded signal to inter symbol interference, making the degradation caused by the subsequent DFT-S stage less susceptible to reduction in bit error rate performance.