Yiqiao Feng

Joint tracking and equalization scheme for multi-polarization effects in coherent optical communication systems

We propose a joint multi-polarization-effect tracking and equalization method based on two extended Kalman filters, which can cope with state of polarization (SOP) tracing, polarization demultiplexing, equalization for polarization dependent loss (PDL) and polarization mode dispersion (PMD) in PDM-M-QAM coherent optical communication system. The mathematical model of the proposed method is given and analyzed in detail. Through simulation, the proposed method is proved to be very effective in a 28 Gbaud/s PDM-16QAM system. With the proposed method, SOP tracing speed is up to 110 Mrad/s for azimuth angle and 1200 krad/s for phase angle, respectively, and PDL and PMD can be equalized simultaneously in the values of 10 dB and more than half of the symbol period.

An effective carrier phase estimation scheme in faster than Nyquist WDM transmission system

We propose a carrier phase estimation method using unequaled digital pilot tone in a faster than Nyquist WDM transmission system, in which the digital pilot tone is employed to estimate laser phase noise induced by the lasers located at the transmitter and the receiver ends. The method can effectively overcome the scale of the inter-symbol interference introduced by FTN signaling, with the good features of high phase noise tolerance and simple hardware complexity.

Implementation of a Reconfigurable Optical Logic Gate Using a Single I/Q Modulator With Direct Detection

We propose and investigate a new scheme to realize all-optical logic gates using a single I/Q modulator with direct detection. Both intensity and phase of the optical signal are utilized to represent the four different states of two binary inputs, whereas direct detection is used to map the four states to the corresponding binary output. This structure is very simple and has the potential to reach high speed. All of the basic logic gates can be implemented by adjusting the bias voltages of the two arms, peak-peak voltages of the driving signals, and the phase shift. Experiments are successfully carried out to realize all six basic logic gates at the data rate up to 10 Gb/s with eye diagrams clearly observed. Extinction ratios (ERs) of the output signals are increased for all these logic gates, compared with the original input signals. ER decreases when increasing the data rate from 1 to 10 Gb/s. Up to 24 logic gates can be implemented by using a single I/Q modulator.

Experimental demonstration of high-speed logic gates of OR, AND, XOR and NOR in optical domain based on a single I/Q modulator and direct detection

We propose a novel scheme of realizing all-optical logic gates based on a single I/Q modulator and direct detection by adjusting bias voltages of the two arms, peak-peak voltages of the driving signals and the phase shift. Experiments are successfully carried out to demonstrate four logic gates of OR, AND, XOR and NOR at the bit rate of 1Gbit/s with extinction ratio higher than 11 dB.

Joint tracking and mitigation of linear dynamic impairments using a 3-stage extended Kalman filter in fiber channel

We propose a novel joint tracking and mitigation scheme for linear dynamic impairments using a 3-stage extended Kalman filter. Simulation results show that it can quickly track and compensate the impairments including multi-polarization effects, frequency offset and phase noise.

Joint equalization scheme for multi-polarization effects in faster than Nyquist WDM transmission systems

We propose a joint multi-polarization-effect equalization scheme using two Kalman filters in a faster than Nyquist-WDM transmission system, which can cope with state of polarization (SOP) tracing, polarization demultiplexing, equalization for polarization dependent loss (PDL) and polarization mode dispersion (P MD).

A noise-folding suppression method in photonic compressed sampling

We utilize a preprocessing method of Whitening Filter in photonic compressed sampling, which can resist the noise-folding problem. The numerical analysis shows that this method can get 20% higher successful recovery ratio of spectral support set compared with traditional method when signal to noise ratio(SNR) is lower than −3dB.

A modified Viterbi and Viterbi phase estimation scheme in faster than Nyquist optical communication system

Faster than Nyquist optical communication system recently attracts more and more attentions because of its higher spectral efficiency than ordinary Nyquist systems. In this work, we propose a modified-Viterbi and Viterbi phase estimation (VVPE) carrier phase recovery (CPR) scheme which shows an effective capability of reducing the cycle slips induced by inter-symbol interference (ISI) in a fast-than-Nyquist (FTN) optical coherent communications system. In a 28-Gbaud FTN polarization-division multiplexed (PDM)-QPSK optical communication system, the comparison of the proposed modified-VVPE scheme and the conventional VVPE scheme is carried out. It is proved that the proposed modified-VVPE scheme can effectively overcome error carrier phase estimation, which leads to a better BER performance.