Xiurong Ma

Temperature Dependence of Fiber-Format Multiwavelength Generation Process in Bulk MgO-PPLN Crystal Via High-Power Photonic Crystal Fiber Laser

In this paper, we report on a compact frequency conversion scheme based on high-power photonic crystal fiber (PCF) laser at optical communication band using a multigrating MgO-PPLN crystal. Temperature dependence of wave-vector mismatch, group velocity, central wavelength, and conversion efficiency was theoretically analyzed. Temperature tuning characteristics were experimentally obtained by propagating 240-fs pulses with a 126-MHz repetition rate in a 10-mm-long MgO-PPLN crystal. We also observed and characterized second-harmonic generation (SHG), third-harmonic generation (THG), and fourth-harmonic generation processes in the same crystal. Maximum SHG and THG conversion efficiency values of 27.5% and 4.3% were achieved at 100 °C and 77 °C, respectively.

Pilot-Based Phase Noise, IQ Mismatch, and Channel Distortion Estimation for PDM CO-OFDM System

In this letter, a pilot-based method is proposed to suppress three non-ideal factors, including channel distortion, transmitter in-phase and quadrature (IQ) mismatch, and laser phase noise for polarization division multiplexed coherent optical orthogonal frequency division multiplexing systems. Compared with the conventional phase noise and IQ mismatch estimation methods which only consider one of the two non-ideal factors, we deduce a novel mathematical model considering both and compensate them with special designed pilots: the channel distortion and IQ mismatch are compensate by the block-type pilot while the comb-type pilot is used to estimate phase noise. The simulation results proved that our method can not only better compensate the non-idealities factors, but also can provide high speed transmission with 120 Gb/s over 400-km transmission compared with the conventional methods.

Spectral broadening in femtosecond pulse written filamentary waveguides in periodically poled lithium niobate

The authors report the filamentary waveguide formation and the significant spectral broadening based on periodically poled lithium niobate substrate. The modified morphology contributes to the combined effects of optical diffraction and self-focusing with the dependence on pulse intensity. Up to 4 times broadening of the FF wave and about 47 nm spanning of the SH wave with the pump power of 19.5 mW are achievable under 1550 nm excitation. Spectral evolution by cubic nonlinearity inside the waveguide has been obtained numerically, and provides a reasonable agreement with the experimental results.

Equal channel spacing Sagnac filter using high-birefringent photonic crystal fibers

An equal channel spacing Sagnac filter is proposed using a high-birefringent photonic crystal fiber (PCF) with birefringence square to the operation wavelength. A PCF with four smaller central air holes surrounded by larger air holes is applied in a Sagnac filter with optimized parameters to achieve equal channel spacing of 0.8 nm. Given that the birefringence of this PCF is square to the operation wavelength, the channel spacing of the proposed filter changes by only 0.03 nm within a wavelength range from 1400 to 1650 nm; this is about one order of magnitude less than that constructed with conventional high-birefringent fibers.

Novel training symbol structure for transmitter IQ mismatch compensation for PDM CO-OFDM at 100Gb/s

We propose a novel training symbol structure for polarization division multiplexed (PDM) coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. We deduce the mathematical model for the scheme. Based on the given model, a novel compensation method is introduced to compensate the IQ imbalance. The theoretical analysis is validated by numerical simulation, in which we apply the Quadrature Phase Shift Keying (QPSK) modulation at a data rate of 75.211Gb/s over 50 km and data rate of 100Gb/s over 320 km transmission. Compared with the commonly used approach, the proposed scheme demonstrates better system BER performance against IQ imbalance.

Compensation for transceiver IQ mismatch with phase noise in CO-OFDM system

In this paper, a simultaneous compensation method to against transmitter (Tx) and receiver (Rx) in-phase/quadrature (IQ) mismatch is proposed in the presence of phase noise originating from the transmitter and local oscillator (LO) lasers for coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. A mathematical model is given which includes the transceiver IQ mismatch and laser phase noise above mentioned. Based on the given model, a recursive algorithm is offered, in which the compensated results are updated symbol by symbol. Simulation results show that when the Tx and Rx amplitude mismatch are2dB, phase mismatch are 10° and 5°, a 1.2dB optical signal-to noise ratio is improved for 60kHz of the laser linewidth of the proposed method by compared with the hybrid method.

Monocycle and doublet pulses generation via photon echo in rare-earth-doped optical crystal

Abstract. All-optical pulse generation opens up a field for ultrawideband (UWB) applications. However, controllable pulse width and pulse type are still challenging. Here, we present a theoretical model and stimulated results of monocycle and doublet waveforms generation using programmable optical photon echo progress. We synthesized instantaneously monocycle and doublet waveforms by adjustment of pulse width, pulse amplitude, pulse position, and time interval of subpulses. We verified the possible application of the proposed method to design U.S. Federal Communications Commission-compliant UWB waveforms, and therefore, it may provide an avenue for waveform generation.