Xie Shizhong

Improved projection algorithm to invert forward scattered light for particle sizing

An improved version of the nonlinear iterative projection algorithm is proposed and applied to the inversion of the light-scattering data for particle sizing. Compared with the original projection algorithm, the improved one is much more stable, reliable, and accurate with respect to random noise. The particle-size distributions retrieved with the improved projection algorithm are independent of the different starting solutions. The criterion for stopping iteration is fairly clearly determined and is not a user-dependent parameter of the inversion algorithm. Numerical computer simulations and experimental results for the mixture of monodispersed size distributions are presented to allow both the inversion procedure validity and the instrument performance to be evaluated.

Tunable attenuator based on polymer microstructured optical fibers

Based on polymer microstructured optical fibers (PMOF) and selective liquid crystal injection technology, a novel temperature control tunable attenuator is designed theoretically in this paper. In our experiments, PMMA microstructured optical fibers with high performance are drawn successfully and the selective injection of liquid crystal 5CB into microholes is realized. The tunable attenuator is fabricated with an extinction ratio of over 60dB, which agrees well with the design.

Fiber gratings based optical add/drop multiplexer with low interferometric crosstalk

Optical add/drop multiplexer (OADM) is one of the key components for WDM systems to enable greater connectivity and flexibility of the network. Fiber grating based devices seem to be promising candidates for OADMs. Two types of OADMs based on fiber gratings and circulators are demonstrated. A novel structure with cascaded gratings is proposed to reduce the interferometric crosstalk which severely degrades the system performance in the common structure. The add/drop multiplexing experiments of 4-channel WDM signals indicate that in the cascaded gratings structure there is 8 dB reduction of the crosstalk for the added signal compared with the common structure and a complete suppression of the crosstalk for the dropped signal.

Fiber optical parametric oscillator based on photonic crystal fiber pumped with all-normal-dispersion mode-locked Yb:fiber laser

We demonstrate a cost effective, linearly tunable fiber optical parametric oscillator based on a home-made photonic crystal fiber pumped with a mode-locked ytterbium-doped fiber laser, providing linely tuning ranges from 1018 nm to 1038 nm for the idler wavelength and from 1097 nm to 1117 nm for the signal wavelength by tuning the pump wavelength and the cavity length. In order to obtain the desired fiber with a zero dispersion wavelength around 1060 nm, eight samples of photonic crystal fibers with gradually changed structural parameters are fabricated for the reason that it is difficult to accurately customize the structural dimensions during fabrication. We verify the usability of the fabricated fiber experimentally via optical parametric generation and conclude a successful procedure of design, fabirication, and verification. A seed source of home-made all-normal-dispersion mode-locked ytterbium-doped fiber laser with 38.57 ps pulsewidth around the 1064 nm wavelength is used to pump the fiber optical parametric oscillator. The wide picosecond pulse pump laser enables a larger walk-off tolerance between the pump light and the oscillating light as well as a longer photonic crystal fiber of 20 m superior to the femtosecond pulse lasers, resulting in a larger parametric amplification and a lower threshold pump power of 15.8 dBm of the fiber optical parametric oscillator.

A novel multi-bit optical code label processing scheme in optical packet switching networks

Parallel-to-cascading optical code label processing is proposed and experimentally demonstrated in a 16-node setup. The physical structure for multi-bit labels processing is significantly simplified, since only one encoder, one decoder and one photodiode are needed.

Improving transmission performance using a waveguide filter in all-optical wavelength converters

Wavelength converters based on cross-gain modulation in a semiconductor optical amplifier (SOA) are limited by pattern dependence and large chirp at high bit rates. We eliminated pattern dependence and realized 40 km SMF transmission of the converted signal from a SOA by using a waveguide narrow band filter at 10 Gbit/s.