Xiaohong Ma

A Novel Design of Distributed Surface Plasmon Sensors Based on Nanoparticles Composite Layers

The application of composite layers with gold nanoparticles embedded in them as the resonance wavelength modulation layers is proposed and theoretically investigated. The results show that the nanoparticles composite layers can increase the sensitivity as well as modulate the resonance wavelength. Besides, when the volume fraction of gold in the composite film is 0.15, the best sensitivity enhancement effect can be obtained.

Theoretical analysis of all-optical 2R regeneration in a SOA-based Mach–Zehnder interferometer

Abstract All-optical 2R regeneration in a semiconductor optical amplifier-based Mach–Zehnder interferometer is theoretically analyzed. It is shown that the chirp of the regenerated signal is positive, while the input signal has no chirp. The peak extinction ratio (ER) of the regenerated signal is associated with the input wavelength and there exists an input wavelength corresponding to the largest ER of the output signal. The output peak ER is also found influenced by the input power, with lower input power getting higher peak ER.

Detection of sulfur dioxide in air by laser induced breakdown spectroscopy

A study of gaseous sulfur dioxide detection in air by Laser Induced Breakdown Spectroscopy(LIBS) is reported. Plasmas were formed in the sulfur dioxide gas, and three lines of sulfur at 560.61nm, 567.77nm and 565.99nm were observed. We found that the most appropriate experimental conditions for LIBS detection on sulfur dioxide gas are: Laser Pulse Energy =100mJ, Gate Time Delay = 2us. A further study was made in detecting sulfur dioxide gas of different concentrations by LIBS. Finally we calculated the detection limit of sulfur dioxide gas is 330ppm.

An absolute frequency reference in exact multiples of 100 GHz by calibrated F-P etalon

1.5μm wavelength region is the window of optical communication. Absolute frequency references that satisfy ITU-T standards in 1.5 μm region for frequency calibration are widely needed in DWDM system. In this paper, an approach of obtaining precise frequency points which ITU-T has produced has been experimented, using an acoustic frequency shift, by calibrating Fabry-Perot etalon using double acetylene absorption lines. In the experiment, mode 1955 of F-P etalon is offset frequency-locked to acetylene absorption line P14, 195500.4023GHz, with frequency stability 108 for a 30-minute measurement. After calibrating, a series of spaced 100GHz artificial absolute frequency references in 1.5μm region are obtained.

A Study of Polarized Light Propagation in Turbid Medium by Monte Carlo Simulations and Experiments

A study of polarized light transmitted through turbid media is described. Spatial distribution of the intensity and the degree of polarization of the transmitted light are measured experimentally and simulated numerically using Monte Carlo method. A CCD (Charge Coupled Device) camera was used in the experiment to capture the profile of the laser source and transmitted light. The experimental and simulation results show that the spatial factors of the scattered light can be used to demarcate tissue optical parameters such as scattering coefficient and absorption coefficient.

Improvement of dispersion tolerance using phase-Modulated NRZ signals in 40-gb/s transmission systems

Compared with the conventional nonreturn-to-zero (NRZ), return-to-zero (RZ), carrier-suppressed return-to-zero, and chirped RZ signals by numerical simulation, a higher dispersion tolerance in the presence of fiber nonlinearities and amplifier noise has been obtained in this letter by using the phase-modulated NRZ signals. This scheme aims to improve resistance to residual dispersion by an adapted phase modulation at the transmitter.

Calibrated Fabry-Perot etalon as 1.5-μm wavelength region absolute frequency reference based on double acetylene absorption lines

Absolute frequency reference in 1.5-μm wavelength region is very useful for DWDM system. We have studied on producing artificial 1.5-μm wavelength region absolute frequency reference by calibrating the F-P etalon. Double acetylene absorption line calibrating technique was adopted. An experiment of calibrating the Fabry-Perot etalon using double acetylene absorption lines has been demonstrated. In the experiment, Mode 1996 of the F-P etalon was locked to acetylene absorption line 1533.4621 nm. The frequency stability of the calibrated F-P etalon was about 7×10-8. After calibrating, a series of artificial absolute frequency references in 1.5-μm wavelength region was obtained. To reduce the complexity of calibrating, a novel frequency difference measurement method was introduced.

A novel method for carrier-suppressed return-to-zero pulse train generation

A novel method to generate carrier-suppressed return-to-zero (CSRZ) pulses by using a sampled fiber Bragg grating (FBG) is proposed, and the transmission characteristics of the CSRZ pulses are simulated and discussed. This CSRZ pulse has a duty cycle of 50%, narrower than conventional CSRZ pulse, which is due to the filtering and shaping of FBG, and leads to increase of nonlinearity and dispersion tolerance in high-speed transmission systems. Through proper design of FBG and adoption of short pulse source, this technique provides a promising way to modify the pulse shape and consequently improve system performance.

Spectrum pruning of 42.7-Gb/s CS-RZ for spectrally efficient long-haul DWDM system

This paper focuses on the simulative optimization of modulation format, which is CS-RZ format with appropriate spectrum filtering, in a 42.7Gb/s spectrally efficient long-haul DWDM system. It is studied that the required bandwidth of the CS-RZ signal with spectrum pruning for channel spacing of 50GHz. The power loss and crosstalk are calculation under the Gaussian filter with various order and bandwidth. The influence on the CS-RZ waveform by the filter of various order and bandwidth was also investigated. Furthermore, the Q-value of the 42.7Gb/s CS-RZ signal was simulated before and after 640km fiber link transmission with 3 order Gaussian filter of various bandwidth, which simulative test system was designed as a 42.7Gb/s DWDM system with simultaneous C+L band discrete Raman amplifier by dispersion compensation fiber (DCF) as Raman medium. As a conclusion, the optimum filter bandwidth of 42GHz is obtained for the 42.7Gb/s 50GHz spaced DWDM system. Q-value of the signal is up to 8 and remains 6.7 after transmission of 640km fiber link, with the filter of the optimum bandwidth.

Impact of concatenated AWG filters in metro transparent network with DML

This paper studies the impact of concatenated AWG routers of metro transparent network with directly modulated lasers (DML). The wide bandwidth and central frequency shift of the directly modulated laser entail a large signal penalty, thereby limiting the allowable number of AWG routers in a metro network. The degradation caused by the concatenation of passband-flattened AWG is much lower than that of the conventional round-top AWG of the same number. Therefore the passband-flattened AWG has the largest allowable number in the metro network based on DML.