Litai 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.

Millimeter-wave subcarrier generation utilizing four-wave mixing and dual-frequency Brillouin pump suppression

A novel photonic technique of 60-GHz millimeter-wave subcarrier generation base on four-wave mixing effect in a semiconductor optical amplifier (SOA) and a dual-frequency Brillouin fiber laser configuration is proposed. In this system, two new harmonic components with six times spacing of the microwave source frequency are created when an optical signal, generated by carrier-suppressed intensity modulation, is launched into the SOA. The two residual modulation sidebands are then suppressed by stimulated Brillouin scattering process, and the leaved idlers provide an millimeter-wave subcarrier signal.

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.

Time- and wavelength-interleaved picosecond pulse source using spectral slicing and dispersion management

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.

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.

Polarization Control and Stabilization Using Coordinate System Transformation

A fast and accurate polarization control and stabilization system, which is based on coordinate system transformation, is experimentally demonstrated. The typical control speed is 50-ms and the output SOP precision is 0.5°.

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.

A novel optical pulse source based on optoelectronic oscillator

A time- and wavelength-interleaved (T- W-interleaved) optical pulse source based on optoelectronic oscillator is presented. By utilizing spectral slicing, a multi-loop configuration is formed in OEO system, which can effectively suppress side-modes. In addition, this configuration is able to generate multi-wavelength optical pluses which can be arranged T- W-interleaved optical pulse stream at different nodes. In this system, 10-ps-wide optical pulses at 5GHz repetition rate are generated with 1ps timing jitter (in the 100Hz-1MHz range) and -100dBc/Hz spurious modes suppression, Along with the optical outputs, 5GHz electrical signal with low phase noise (-113dBc/Hz at 10kHz offset from the carrier) is also obtained.