Changyong Tian

Dual-Wavelength Packets Buffering in Dual-Loop Optical Buffer

We demonstrated 10-Gb/s dual-wavelength packets buffering in a dual-loop optical buffer with a semiconductor optical amplifier. Confirmed by experiments, the crosstalk between lambda1 and lambda2 signals, which is the main reason of restraining the buffering time, is decreased by using power equalization. The buffered data packets are retrieved after they are buffered for one, two, and three cycles with the maximum buffering time up to 3.75 mus. The power penalty, the extinction ratio, and the signal-to-noise ratio are 2.1, 7.5, and 4 dB, respectively, after three cycles. We obtain the eye diagrams for both wavelengths with good results, and the buffer is transparent for either wavelength.

Novel Tunable Fiber Optic Edge Filter Based on Modulating Chirp Rate of π-Phase-Shifted Fiber Bragg Grating

We propose and experimentally demonstrate a novel tunable fiber optic edge filter based on modulating the chirp rate of a pi-phase-shifted fiber Bragg grating (FBG) operated in reflection mode. The phase shift induced notch in the reflection spectrum is utilized as the edge filter. The dependence of the pi-phase-shifted FBGs spectral response on the chirp rate has been numerically studied in detail and experimentally confirmed for the first time. The linear wavelength range of this edge filter can be tuned by changing the chirp rate of FBG. A fiber optic edge filter is further obtained experimentally and tested as a wavelength interrogator, which is in a good agreement with numerical results. The proposed edge filter has advantages of simple-structure, cost-effectiveness, high sensitivity, and flexible tunable, thus opening up some applications, especially as wavelength interrogator in small wavelength range.

Polarization rotation analysis of semiconductor optical amplifiers and switching application

By means of polar decomposition of the Mueller matrix, we analyze polarization rotation (PR) effects in SOAs and demonstrate the PR angle is linear to the birefringence dependent gain (BDG). Then we further investigate the photoinduced PR (PPR) and cross-gain modulation (XGM) effects in a pump-probe scheme, and realize the orthogonal PR by control of a high-intensity pump laser. Finally we perform the polarization switching (PS) based on PPR with data rate at 2.5 G-bit/s. The switching speed of our PS is ~300 ps, which is highly promising to be further upgraded.

All-Optical Clock Frequency Multiplication Based on SOA-assisted Mach-Zehnder Interfering

We present a novel scheme of all-optical clock frequency doubling and quadrupling based on Mach-Zehnder interfering with a polarization-sensitive semiconductor optical amplifier (SOA). Then we experimentally demonstrate the frequency doubling of 5 G-bit/s optical clock signal, and quadruple 2.5 G-bit/s signal to stable short pulse train with pulse FWHH ~55 ps. Our relatively concise scheme is convenient to be upgraded to 40 G-bit/s and applicable to high-speed optical communications.

Dual-wavelength signals delays via Brillouin Slow Light in an Optical Fiber

We demonstrate the single and dual wavelength signals delays via Brillouin slow light in the single mode fiber at the same time. Moreover, each wavelength delay of the signal can be also controlled by the other wavelength pump power. For single wavelength, the width of 100 ns pulse can be delayed from 0 ns to 40 ns by tuning the power of the pump while for dual wavelengths pump the delay time decrease to 30 ns.

Stimulated Brillouin scattering of various specialty fibers and its application in slow light

We have tested and characterized the stimulated brillion scatter (SBS) optical spectrum in single-mode optical fibre (SMF), photosensitive fibres (PSF) and photonic crystal fibers (PCF). The different refractive indexes of fibbers cause different Brillion frequency shifts. We have also demonstrated the slow light in SMF visa SBS. The width of 100ns pulse can be delayed from 0ns to 40ns by tuning the power of the pump.

Dual wavelength signals buffered in DLOB and its improvement by power equalization

ww have presented and demonstrated the dual-wavelength signal storage in Dual-Loop Optical Buffer. The output equality of dual wavelength signals will decrease for unbalanced gain and phase shift. The problem can be resolved by power equalization using the saturation character of SOA. The data packets with2 × 2.5Gb/s can be buffered in DLOB for 16 cycles corresponding to 20 .The Extinction Ratio of the output packet is 8dB while the S/N is 8.1dB.

Digital polarization encoding based on orthogonal polarization rotation in a semiconductor optical amplifier

We investigate the polarization-dependent mode gains and polarization rotation (PR) of the semiconductor optical amplifier in pump-probe scheme, and find that the relationship between polarization rotation (PR) and mode gains keeps well under different pump power. Thus we can simply obtain the PR angle by measurement of the mode gains. Choosing suitable injected current we realize the orthogonal polarization rotation by pump laser with power of ~3.5 mW. Then we propose a novel digital polarization encoding scheme and perform it well in a 10-km fiber transmission system with data rate at 2.5 G-bit/s, which is promising to promote the optical power-equalized encoding communications.

Phenomenological Model with Application for Polarization-Sensitive Semiconductor Optical Amplifiers

We introduce a phenomenological model to describe polarization-sensitive SOAs which is composed of a partly linear polarizer, a retarder, and a polarization independent amplifier. It shows that any input optical vector of signal will first be partly linearly polarized, then rotate around S1-axis of the Poincaré sphere for θ, and finally be amplified equably. Then we investigate and experimentally demonstrate the relationship between polarization rotation (PR) and mode gains. We further obtain two necessary conditions for the valuable orthogonal polarization rotation (OPR), and then perform a power-equalized OPR by optical-electric synchronous control of the SOA. The polarization duration time is ~10 ns which is applicable to high-speed polarization state generation.

8×10 Gb/s data packets buffered in Dual Loop Optical Buffer (DLOB)

Abstract-We demonstrated 8 × 10 Gbit/s packets buffered in Dual Loop Optical Buffer (DLOB).Confirmed by experiments, the crosstalk and unbalanced power among different wavelengths which is the main restraining of the buffering time can be avoided by power equalization using Semiconductor Optical Amplifier (SOA). The buffered data packets can be retrieved after they are buffered for 5 cycles. The power penalty, the Extinction Ratio and the Signal to Noise Ratio are 4.2dB, 3.98dB, 5.47dB. The eye diagrams for 8 wavelengths signals are obtained.