Guangtao Zhou

Dispersion-Compensation Schemes for 160-Gb/s 1200-km Transmission by Optical Phase Conjugation

Appropriate dispersion management possesses the superiority to relax the limitation of nonlinearities in high-speed transmission systems employing optical phase conjugation (OPC). In this paper, several dispersion-compensation schemes have been analytically and numerically investigated in a 160-Gb/s OPC system. A comprehensive performance comparison of these schemes over 1200-km transmissions has been carried out to present a reference for future OPC system designs. The scheme with a gradient dispersion map is recommended, particularly for G.655 fiber with a relatively low local dispersion.

40Gbit∕s all-optical logic NOR gate based on a semiconductor optical amplifier and a filter

A novel all-optical logic NOR gate is presented that is composed of a semiconductor optical amplifier (SOA) and an optical bandpass filter. The NOR gate is successfully experimentally demonstrated at 40 Gbit/s. The experiment result shows good extinction ratio of larger than 12.0 dB with clear and open eye. The NOR gate has a simple configuration and allows photonic integration.

Automatic PMD compensation experiment with particle swarm optimization and adaptive dithering algorithms for 10-gb/s NRZ and RZ formats

We demonstrate a 10-Gb/s polarization-mode dispersion (PMD) compensation experiment by using a 4-degree of freedom compensator for both NRZ and RZ formats. The particle swarm optimization method is used as the searching algorithm and an adaptive dithering algorithm is employed in tracking process. The results show that the searching process is finished within several hundreds of milliseconds and the response time for the compensator to recover from a sudden disturbance is less than 20 ms.

Analysis of four-wave mixing effects in 40Gbit/s CSRZ/RZ-DPSK systems

The work presented in this paper gives performance comparisons of Carrier Suppressed Return-to-Zero Differential Phase-Shift Keying (CSRZ-DPSK) with Return-to-Zero Differential Phase-Shift Keying (RZ-DPSK) against both the effects of Intra-Channel Four-Wave Mixing (IFWM) and inter-channel Four Wave Mixing (FWM) in 16×40 Gb/s WDM systems with symmetrical fiber link schemes. IFWM gives smaller phase perturbation to CSRZ-DPSK signal than to RZ33-DPSK, although BER performance of CSRZ-DPSK is worse than that of RZ33-DPSK. The numerical comparison indicates that RZ33-DPSK is a better candidate for 40 Gb/s WDM systems than CSRZ-DPSK.

Analysis of DOP feedback signal in PMD compensation system based on the different modulation formats

The relationships between Degree of Polarization (DOP) and Polarization Mode Dispersion (PMD) for different modulation format signals are discussed not only in theory but also in experiment, which include the NRZ, RZ, CSRZ, DPSK, RZ-DPSK and CSRZ-DPSK signals. The RZ signals with different duty cycle are also analyzed and compared. The results are found that the optical signals DGD/DOP relation depends on their optical spectrum structure as well as the modulation formats, and the phase-shift-keying signal with free chirp will provide better performance in the PMD compensation based on the DOP feedback control because of the DOP sensitivity and wide monitoring window, besides, the CSRZ has the stalest character for the variety of modulation chirp.

Performance analysis of DPSK modulated signals in optical transmission link with PMD and PDL

Polarization effects such as polarization mode dispersion (PMD) and polarization dependent loss (PDL) have become the critical limiting factors for long haul high bit rate optical fiber transmission. This paper use waveplate models to simulate the statistical performance of optical link with PMD and PDL in 40Gbit/s optical system. Three DPSK modulation formats are compared each other for their tolerance against PMD and PDL. The 33% RZ-DPSK is superior to the other two DPSK formats, the 50% RZ-DPSK and the CSRZ-DPSK whose duty cycle is 67% when only PMD is considered. And in case of PDL, the outages for three DPSK formats do not show obvious changes with the increasing of PDL. Furthermore, the performance of two RZ-DPSK formats, whose duty cycles are 33% and 50% respectively, is superior to that of CSRZ-DPSK. This shows that modulation format with narrower pulse width owns more high tolerance against PMD and PDL, therefore the CSRZ-DPSK format shows poorer performance when it is compared with the other two DPSK formats.

Adaptive PMD compensation up to second-order in 40Gb/s OTDM optical communication system using two-stage compensator

In this paper we report a successful experiment of adaptive polarization mode dispersion (PMD) compensation up to second-order in a 40Gb/s optical time-division multiplexed (OTDM) communication system by using two-stage compensator. In the experiment the PMD monitoring technique based on degree of polarization (DOP) was adopted. And the Particle Swarm Optimization (PSO) algorithm was introduced in adaptive PMD compensation, with the desirable features of fast convergence to the global optimum point for compensation without being trapped in local sub-optima and with good robustness to noise. The comparison was made to estimate the performance effectiveness between PSO algorithms with global neighborhood structure (GPSO) and with local neighborhood structure (LPSO). The LPSO algorithm is shown to be more effective to search global optimum for PMD compensation than GPSO algorithm. The ability of tracking changed PMD using PSO algorithm was also investigated. The two-stage PMD compensator is shown to be effective for both first- and second-order PMD, and the compensator is shown to be bit rate independent. The compensation time is within several hundreds of milliseconds. The response time for recovery from a sharp disturbance is about 11ms.

An experiment of adaptive polarization mode dispersion compensation of optical communication systems

An experiment of adaptive polarization mode dispersion compensation of optical communication systems is reported in this paper. The compensated PMD value is up to 30 ps. Automatic tracking time is about 1 to 2 seconds. The quasi-real-time adaptive PMD compensation is realized.

A novel all-optical up-conversion technique using FWM effect in HNL-DSF for binary OOK-ROF system with CSRZ carrier

Using four wavelength mixing (FWM) effect in high-nonlinear dispersion-shifted fibre (HNL-DSF), a novel up-conversion technique for binary on-off-key (OOK) radio-on-fibre (ROF) system is proposed in this paper. By injecting a non return-to-zero (NRZ) format data signal and a carrier-suppressed return-to-zero (CSRZ) format carrier signal into HLN-DSF, a signal with a new frequency component generated by FWM effect will have the phase characteristic of CSRZ carrier. The simulation results indicate that the signal has the better transmission performance because of the strong ability of resisting dispersion.

PMD and CD tunable compensation using the nonlinear chirp SBG with uniform grating period

Polarization mode dispersion (PMD) and chromatic dispersion (CD) are two important limiting factors, which affect the performance of high speed fiber transmission system. The tunable PMD and CD compensation experiment on 10Gbit/s NRZ fiber transmission link is reported by using two nonlinear chirp sampling fiber gratings, which are fabricated on high-birefringence and standard single mode fibers by using uniform phase mask. The total system power penalty is less than 1dB (@BER 10-12) after PMD and CD tunable compensation.