Aixu Zhang

Pulse source based on directly modulated laser and phase modulator

We propose the simple pulse source, in which the pulses generated by large-signal directly modulated laser diode are phase-modulated, and then compressed into short pulses by an optimized length of DCF. On the one hand, phase modulator is used to enhance the negative chirp of large-signal directly modulated pulses. On the other hand, the largesignal directly modulated pulses are used to suppress the pedestal produced by the phase modulator. Using this technique, highly stable 10-GHz 5.5-ps optical pulses are obtained, which suppress pedestal up to 20dB and have a low timing jitter of 184fs.

40-Gb/s All-Optical Serial-to-Parallel Conversion Based on a Single SOA

An all-optical serial-to-parallel converter (AOSPC) was experimentally demonstrated. It could potentially be used to process variable-length optical packets. This scheme mainly consists of wavelength interleaved pulse generation and the sequential multiwavelength conversion (SMWC). The SMWC is based on a single semiconductor optical amplifier. In this research, a 40-Gb/s serial optical signal was converted into four-channel 10-Gb/s parallel optical signals. This scheme has the advantages of a simple system configuration, integration potential, and polarization independency. In addition, the AOSPC is suitable for an input signal with a low optical signal-to-noise ratio and at the same time can regenerate degraded serial signals.

Investigation of a Rate-Selectable All-Optical Packet Clock Recovery System

This letter presents the experimental performance of a rate-selectable all-optical packet clock extractor using a Fabry-Perot (F-P) filter, a semiconductor optical amplifier (SOA), and polarization interferometers (PIs). The F-P filter with a low finesse and a free-spectral range (FSR) equal to the lowest packet data rate was used to directly extract the packet clock from the packet data stream, which ensures that the clock locks fast and vanishes quickly. Different PIs, in conjunction with the F-P filter, were used to form comb filters with different FSRs in order to suppress the undesired subharmonic frequencies. The clock then goes into SOA to reduce the low-frequency amplitude noise. We demonstrate packet clock extraction at 10, 20, and 40 Gb/s with the combination filter.

Tunable chromatic dispersion compensation using chirp control based on XPM in a SOA

We demonstrate a tunable chromatic dispersion (CD) compensation technique using a semiconductor optical amplifier (SOA) and a coil of dispersion compensation fiber (DCF). Based on cross-phase modulation (XPM) in the SOA, the transient chirp of the received signal can be adjusted by tuning the drive current of the SOA and the power of clock pulse. In this way, a 10-Gbit/s tunable CD compensation setup, ranging from -40ps/nm to 60ps/nm, is realized without changing the length of the DCF.

40-Gbit/s all-optical 3R regeneration based on F-P filter and SOA

40Gbit/s all-optical 3R regeneration was demonstrated. The wavelength of the data signal was converted with an SOA by cross-gain modulation (XGM). The clock recovery was based on Fabry-Perot (F-P) filter of high finesse (F=1000). The actual bit rate of the data signal was 40.04796Gbit/s, matching the free spectral range (FSR) of the F-P filter. Two SOAs were used in series as the decision gate to make full use of the nonlinearity. Taking advantage of the chirp, one narrowband OBF was used to reshape the waveforms in the clock recovery, so as to reduce the pattern effect. Another narrowband OBF was used after the decision gate to diminish the tails of the pulses. The clock signal had a root mean square (RMS) timing jitter of around 843fs. The output data signal of the regenerator had an optical signal-to-noise ratio (OSNR) of more than 40dB/0.1nm. The maximum timing jitter was 1.439ps.

Time-and Wavelength-Interleaved Picosecond Pulse Source with Tunable Channels and Repetition Rate

A time- and wavelength-interleaved optical pulse source, which is based on spectral slicing and dispersion management, is proposed and experimentally demonstrated. The pulse source has a simple configuration, and both the repetition rate and the wavelength channels can be tuned easily.

10GHz all-optical packet clock recovery with ultrafast locking and unlocking time via XPM effect of the SOA

Short locking and unlocking time is essepecially important in the packet clock recovery, as it determines the network resource utilization. This paper presents a novel 10-GHz all-optical packet clock extractor with ultrafast locking and unlocking time via self-phase modulation (SPM) effect of the semiconductor optical amplifier (SOA). Low finesse Fabry-Perot (F-P) filter and a saturated SOA, in cascade, are used to directly extract the packet clock from the data stream. An optical bandpass filter(OBPF) is used to filter out the red-shifted parts of the packet clock in order to reduce the locking and unlocking time. We analytically investigate the impact of the locking and unlocking time thanks to the self-gain modulation (SGM) effect and self-phase modulation(SPM) effect induced by the SOA, and demonstrate 10GHz clock extraction with the establishing time of 200ps and vanishing time of 600ps experimentally.

Short pulse generation using chirp control

We present a compact short pulses source, in which the pulses generated by large-signal directly modulated laser diode are phase-modulated, and it can compress the pulse from 30ps to 5.3ps with 184fs timing jitter.

All-optical regenerative multicasting at 4×10-Gb/s based on a SOA and a single optical source

We experimentally demonstrate a 4×10-Gb/s optical multicast scheme using a semiconductor optical amplifier (SOA) and a single optical source, which produce a 10-GHz multi-wavelength pulse-trains used as the probe light of the SOA. The multicast principle is based on the multi-wavelength conversion (MWC) by means of the interaction of both cross gain modulation (XGM) and transient cross phase modulation (T-XPM) of the SOA. Because of the nonlinear amplification of SOA, the 4 output copies are regenerated with respect to the input degraded signal. This scheme is very simple and allows photonic integration.

40-Gb/s all-optical serial to parallel converter

We demonstrate a novel 40-Gb/s all-optical serial to parallel converter (AOSPC), which can convert 40-Gb/s serial optical signals to 4-channel 10-Gb/s parallel optical signals. Moreover, based on the sequential multi-wavelength conversion the AOSPC shows the regeneration ability.