Fangzheng Zhang

Simultaneous multi-channel CMW-band and MMW-band UWB monocycle pulse generation using FWM effect in a highly nonlinear photonic crystal fiber

We propose and experimentally demonstrate a scheme to simultaneously realize multi-channel centimeter wave (CMW) band and millimeter wave (MMW) band ultra-wideband (UWB) monocycle pulse generation using four wave mixing (FWM) effect in a highly nonlinear photonic crystal fiber (HNL-PCF). Two lightwaves carrying polarity-reversed optical Gaussian pulses with appropriate time delay and another lightwave carrying a 20 GHz clock signal are launched into the HNL-PCF together. By filtering out the FWM idlers, two CMW-band UWB monocycle signals and two MMW-band UWB monocycle signals at 20 GHz are obtained simultaneously. Experimental measurements of the generated UWB monocycle pulses at individual wavelength, which comply with the FCC regulations, verify the feasibility and flexibility of proposed scheme for use in practical UWB communication systems.

Pilot-symbols-aided cycle slip mitigation for DP-16QAM optical communication systems

A pilot-symbols-aided phase unwrapping (PAPU), which utilizes the time-division multiplexed pilot symbols that are transmitted with data, is proposed to do cycle slip detection and correction with the carrier phase estimation (CPE). Numerical simulations for 10 Gbaud dual-polarization 16-ary quadrature amplitude modulation (DP-16QAM) systems show that the block averaging quadrature phase-shift keying (QPSK) partitioning with PAPU greatly eliminates the performance degradation caused by cycle slips, maintains a low CS probability with less influence of filter length, and achieves a bit-error-rate (BER) performance below soft-decision forward error correction (FEC) limit 2 × 10⁻² at 15 dB optical signal-to-noise ratio with only 1.56% overhead and 6 MHz combined laser linewidth.

Compensation of Mode Coupling of Mode-Division Multiplexing Transmission System with MIMO CMA

We simulate a mode-division multiplexing transmission system with 4×4 MIMO structure, mainly considering the impact of constant linear mode coupling in the channel. W, and utilize multimode CMA to restore emission signal.

Arbitrary repetition-rate multiplication of high speed optical pulses using a programmable optical processor

We demonstrate a method to realize arbitrary repetition-rate multiplication of 40 GHz optical pulses based on optical spectrum manipulation. The generated 80–320 GHz pulses can well maintain the original pulse shape with uniform amplitude and improved SNR.

Nonlinear phase noise in coherent polarization-multiplexed quadrature phase-shift keying systems over dispersion managed link

Nonlinear phase noise (NLPN) induced by the interaction between the amplified spontaneous emission noise (ASE) and the information signal in polarization-multiplexed quadrature phase-shift keying (PM-QPSK) systems at 42.8(112)  Gbit/s over dispersion-managed (DM) link is investigated by numerical simulations. Both symbol-aligned non-return-to-zero (NRZ) PM-QPSK and symbol-interleaved return-to-zero (RZ) PM-QPSK formats are considered and compared. We find that for aligned NRZ-PM-QPSK systems, the impact of NLPN on system performance seems rather weak due to the strong interchannel cross-polarization modulation (XPolM). However, when the interleaved RZ-PM-QPSK format is used, in which the XPolM is suppressed significantly, the system performance is seriously degraded by NLPN, especially at low bit rates. Results of 1000-km transmission employing standard single-mode fiber (SSMF) over DM link show that for 42.8  Gbit/s coherent RZ-PM-QPSK systems, the nonlinear threshold (NLT) will decrease from 6 to 2 dBm due to nonlinear phase noise when symbol-interleaved format is used.

Fiber nonlinear tolerance comparison between 112 Gb∕s coherent transmission systems using quadrature-phase- shift-keying, offset quadrature-phase-shift-keying, and minimum-shift-keying formats

Abstract. We numerically investigate the nonlinear transmission performance of 112  Gb/s coherent transmission systems using polarization multiplexed quadrature-phase-shift-keying (QPSK), offset QPSK (OQPSK) and minimum-shift-keying (MSK) formats, and compare the fiber nonlinear tolerances of the three modulation formats. Simulation results show that in both single channel and wavelength-division-multiplexed (WDM) systems, OQPSK is slightly more resistant to fiber nonlinearities than QPSK, and MSK has the best fiber nonlinear tolerance. The advantage of MSK format over QPSK and OQPSK is particularly notable in WDM systems. When digital back propagation (DBP) is used in the digital coherent receiver for intra-channel fiber nonlinearity compensation, system performance is improved with better Q-factor, enlarged input optical power range and extended transmission distance. It is found that the use of DBP brings the largest performance improvement in QPSK system and the least performance improvement in MSK system although MSK system has better fiber nonlinear tolerance.

Simultaneous UWB monocycle pulse generation and frequency up-conversion with multicasting capability using FWM effect in a highly nonlinear photonic crystal fiber (HNL-PCF)

A scheme to simultaneously realize UWB monocycle pulse generation and frequency up-conversion using FWM effect in a 60-meter HNL-PCF is experimentally demonstrated. Two baseband and two frequency up-converted signals are obtained for UWB-over-fiber systems.