Wu Chong-Qing

Cascaded Optical Buffer Based on Nonlinear Polarization Rotation in Semiconductor Optical Amplifiers

A cascaded buffer based on nonlinear polarization rotation in semiconductor optical amplifiers is proposed, which is suitable for fast reconfiguration of buffering time at picoseconds. With the proposed buffer, sixty different buffer times are demonstrated at 2.5 Gb/s.

An Encryption-Decryption Method Using XOR Gate Based on the XPM between O-Band and C-Band Light Waves

An all-optical encryption-decryption method using an exclusive-or gate based on the cross-phase modulation between O-band and C-band light waves is proposed. The feasibility of the encryption-decryption technique is verified by handling binary signals at 2.5 Gbps, with less than 3 dB penalty of extinction ratio and 1 dB polarization dependent loss.

Evaluation of Slow Light Periodic Signals Considering the Distortion in EDF

Based on the fundamental harmonic phase delay, a new definition of fundamental harmonic fractional delay (FHFD) is proposed to evaluate slow light with the consideration of signal distortion, to eliminate the dependence on the choice of the reference point. By solving the rate equation of erbium-doped fiber (EDF), it is shown that the slow light always accompanies the signal distortion when the periodic signal propagates in EDF, and FHFD depends on the signal distortion, as well as the average input power, the modulation depth and the length of EDF. The results of simulations and experiments indicate that the definition of FHFD is reasonable and effective to evaluate the slow light of periodic signals.

Measurement of the Internal Loss Coefficient of Semiconductor Optical Amplifiers

The internal optical loss in semiconductor optical amplifiers (SOAs) is investigated experimentally and theoretically over a wide injection current range. A new measurement method is proposed without noise figure spectra. Theoretically, considering the internal loss in an SOA, a modified formula of the input-output characteristics is deduced. Based on the practically measured input-output characteristic curves, the internal loss coefficient of an SOA is measured at different injection currents. The results demonstrate that the internal loss coefficient of SOAs decreases with increasing injection current.

A New Distributed Measurement of Birefringence Vectors by P-OTDR Assisted by a High Speed Polarization Analyzer

A new polarimetric optical time domain reflectometry (P-OTDR) measurement device assisted by a high speed polarization analyzer is designed and a new algorithm, which can be used to accurately measure the birefringence vector, is proposed. In this method, only one measurement is required and the result is insensitive to the input state of polarization. An 1-km single mode fiber (SMF) is measured and the distribution of the local birefringence vector along the SMF is obtained with a resolution of 2 cm.

Investigation on Characteristics and the Improving Method of Double Loop Optical Buffer

We establish an equivalent cascaded semiconductor optical amplifier system model to analyze the characteristics of the double loop optical buffer (DLOB). The theoretical analysis finds that the performance of the DLOB can be improved by inserted amplifying process in an interval of some cycles. The experiment demonstrates that the buffered cycles can be improved from 20 to 50 and the bit error rate is less than 10−9 by inserting amplifying process in an interval of about 10 cycles.

Matrix-Based Polarization Analysis and Application of Semiconductor Optical Amplifiers

Employing the Mueller matrix method with polar decomposition, we analyse the polarization rotation (PR) effects in semiconductor optical amplifiers (SOAs) and demonstrate that the PR angle is linear to the birefringence dependent gain while the average PR coefficient is about 0.625 for the employed SOA. It is further evident that the current and optical intensity dependent PRs rotate reversely around the same axis. Thus we propose an optical-electric synchronous control scheme to obtain orthogonal polarization states with power-equalization, and implement it by a polarization-sensitive SOA. The polarization duration time is about 10 ns which is applicable to high-speed polarization state generation.

Measurement of linewidth enhancement factor of SOA using fiber Sagnac Ring

Semiconductor optical amplifiers (SOA) are optical amplifying devices and key parts in optical switches and optical buffers. They are largely used in communication system. Linewidth enhancement factor is an important parameter for SOA. A method is proposed to measure the linewidth enhancement factor with Sagnac interferometer. Cross phase modulation (XPM) and cross gain modulation (XGM) coexist in SOA. The quantitative relation of linewidth enhancement factor to XGM and the interference extinction ratio is given. The experimental results indicate that the value of linewidth enhancement factor changes from 5. 13 to 6. 24 when the electric current varies from 130 mA to 240 mA.

Influence of Multi-Cascaded Semiconductor Optical Amplifiers on the Signal in an Energy-Efficient System

Signal impairment is experimentally studied by using the extinction ratio (ER), error bit rate (BER) and optical spectrum in a three-cascaded semiconductor optical amplifier (SOA) setup. The signal with the ER of 13 dB and BER of < 10−9 is achieved after the signal passing through the cascaded SOAs. With the results obtained from the experiment, we confirm that the three-cascaded SOAs used to compensate for power in the optical transmission can be accepted. This experimental result also offers the possibility of achieving a higher throughput of multiplane architecture by exploiting three switching domains instead of two switching domains in the energy-efficient design of a scalable optical multi-plane interconnection architecture. The space switches in output ports of multi-plane interconnection architecture can be improved to N = 32 × 32 × 32 = 32768.

Polarization Dependence of Linewidth Enhancement Factor in Semiconductor Optical Amplifier and Its Implication for Nonlinear Polarization Rotation

Linewidth enhancement factors (LEFs) of the transverse electric mode and the transverse magnetic mode in bulk semiconductor optical amplifiers are measured using the nonlinear optical loop mirror method and the principal state of polarization vector method. The polarization dependence of LEFs plays an important role in the nonlinear polarization rotation. The relationship between the polarization-dependence of LEFs and nonlinear polarization rotation in the Stokes space is demonstrated.