Dexiu Huang

Ultrawideband monocycle generation using cross-phase modulation in a semiconductor optical amplifier

We propose a novel scheme to generate ultrawideband (UWB) monocycle pulses based on cross-phase modulation (XPM) of a semiconductor optical amplifier (SOA). The proposed system consists of a SOA and an optical bandpass filter (OBF). Due to the XPM, a continuous wave (CW) probe signal is phase modulated by another optical Gauss pulse in the SOA. The OBF will convert the phase modulation to intensity modulation. A pair of polarity-reversed UWB monocycle pulses is achieved by locating the probe carrier at the positive and negative linear slopes of the OBF. Both cases conform to the UWB definition of the Federal Communications Commission.

All-optical AND gate at 10 Gbit/s based on cascaded single-port-couple SOAs.

An all-optical logical AND gate at 10 Gbit/s based on cross-gain modulation (XGM) in two cascaded semiconductor optical amplifiers (SOAs) is demonstrated. Single-port-coupled SOAs are employed and specially designed to improve the output extinction ratio as well as the output performance of the logic operation. The output signal power and extinction ratio from the first-stage wavelength converter are critical to achieving all-optical logical AND operation.

Multiwavelength erbium-doped fiber lasers exploiting polarization hole burning

Simultaneous multiwavelength lasing is demonstrated exploiting intracavity polarization hole burning in an erbium-doped fiber laser. Experimental results indicate that polarization hole burning can be enhanced by the changes of the light polarization states and bias current of optical MQW waveguide which serves as reflector in the laser. Eleven wavelengths with 0.9 nm spacing are generated at room temperature.

Fiber grating Sagnac loop and its multiwavelength-laser application

We introduce a novel simple comb filter, which is based on a Sagnac interferometer with a fiber Bragg grating asymmetrically located in its fiber loop. The filter has advantages of simple design and easy fabrication, low insertion loss and low cost. Two filters with triple bandpasses and dual bandpasses, respectively, were fabricated and applied to an erbium-doped fiber ring laser. Stable triple-wavelength and dual-wavelength laser operations have been demonstrated.

Large blue shift of light emitting porous silicon by boiling water treatment

A boiling water treatment of light emitting porous silicon can give rise to a large blue shift of its photoluminescence spectrum and meanwhile strengthen the skeleton of porous Si by filling up many pores with aqueous oxide. A stable blue‐green light emission at the peak wavelength down to 500 nm is achieved. FTIR measurements show that the formation of Si dihydride on the sidewall surfaces of the Si rods is not responsible to the visible luminescence for the very thin Si wires.

Ultrafast All-Optical Signal Processing Based on Single Semiconductor Optical Amplifier and Optical Filtering

We propose and demonstrate several all-optical signal-processing technologies, including wavelength conversion (WC), leading/trailing edge detection, and logic gates based on a semiconductor optical amplifier (SOA) and a detuning optical bandpass filter (OBF). The system is based on pump-probe scheme. When the pump signal is return-to-zero (RZ) format, both inverted WC and noninverted WC at 40 Gb/s are obtained, and the polarity variation is highly dependent on the OBF detuning. When the pump signal is nonreturn-to-zero (NRZ) format, both the inverted WC and leading/trailing edge detection are obtained. In the inverted WC, the OBF detuning is small, and it helps to accelerate the amplitude recovery. However, in the noninverted WC and pulse edge detection, the OBF detuning is relatively large, and it acts as frequency-amplitude conversion. Finally, we present all- optical reconfigurable logic gates based on various nonlinearities in an SOA. The logic gates including AND, NOR/NOT, and OR are obtained by four-wave mixing, cross-gain modulation, and transient cross-phase modulation in the SOA, respectively. The NOR and OR gates are capable of operating at 40 Gb/s with the help of the OBF detuning. The XNOR gate is implemented by combining the AND output and NOR output.

High-speed all-optical differentiator based on a semiconductor optical amplifier and an optical filter.

We demonstrate a novel all-optical differentiator that carries out the first-order temporal derivation of optical intensity variation at high speed. It consists of a semiconductor optical amplifier (SOA) and an optical filter (OF) serving as an optical phase modulator and a frequency discriminator, respectively. A polarity-reversed derivative pair with a certain bias can be obtained by locating the probe wavelength at the positive or negative slope of the OF. Differentiations of super-Gaussian and Gaussian signals are obtained at various data rates. Defined as the mean absolute deviation of the measured result from the ideal result, total average errors of less than 0.12 are observed in all cases. Input power dynamics as well as control wavelength dependence are investigated and show that the cross-gain modulation in the SOA is detrimental to the differentiation performance.

Ultrafast all-optical three-input Boolean XOR operation for differential phase-shift keying signals using periodically poled lithium niobate

We propose and demonstrate that periodically poled lithium niobate (PPLN) can act as an ultrafast three-input XOR gate for differential phase-shift keying (DPSK) signals based on cascaded sum- and difference-frequency generation. PPLN-based all-optical three-input Boolean XOR operations for 20 Gbits/s return-to-zero DPSK (RZ-DPSK), 40 Gbits/s RZ-DPSK, and 20 Gbits/s non-return-to-zero DPSK signals are all successfully verified in the experiment.

Highly sensitive chemical sensor based on the measurement of the separation of dual resonant peaks in a 100-μm-period fiber grating

Abstract A novel chemical or surrounding refractive index sensing scheme based on the measurement of the separation of the dual resonant peaks in a long-period fiber grating with a period of 100 μm is demonstrated. Because the dual resonant peaks shift in opposite directions with the variation of surrounding refractive index, extremely high sensitivity can be achieved with the scheme. As an example, the minimum concentration change as small as 0.01% for aqueous solutions of cane sugar can be detected. The separation varied 229.2 nm and an average resolution of 4.8×10 −5 for the refractive index is achieved in the 1.33–1.44 index range.

Simultaneous demonstration on all-optical digital encoder and comparator at 40 Gb/s with semiconductor optical amplifiers

We proposed and experimental demonstrated all-optical two line-four line encoder and two bit-wise comparator of RZ data streams at 40Gb/s based on cross gain modulation (XGM) and four wave mixing (FWM) in three parallel SOAs. Five logic functions for digital encoder and comparator between two signals A and B: AB, AB, AB, AB and AOmicronB, were achieved simultaneously. The first three optical logics are realized based on XGM in SOAs, the fourth is realized with FWM, and the fifth is the mixing result of the first and the fourth. A detuning filter is employed to improve the output performance. The output extinction ratio (ER) for the XGM operation is above 10dB, and the ER for FWM operation is around 8 dB. Wide and clear eye patterns for the five logic outputs can be observed.