Jacques Chi

All-Optical Clock Recovery and Pulse Reshaping Using Semiconductor Optical Amplifier and Dispersion Compensating Fiber in a Ring Cavity

An all-optical clock recovery device capable of continuously recovering the clock frequency of optical return-to- zero signals from a 10- to 12.5-GHz repetition rate is reported. The recovered clock consists of chirp-free Gaussian pulses at a diffraction limit with low timing jitter of ~200 fs. We employ intracavity dispersion-compensating fiber (DCF) in order to eliminate chirp and asymmetry of semiconductor optical amplifier (SOA)-amplified pulses. This SOA+DCF ring configuration allows us to easily recover the clock over a 40-nm tuning range corresponding to the SOA gain bandwidth.

Performance of the passive recirculating fiber loop buffer within an OTDM transmission link

In this paper, we examine the propagation of both standard soliton and the Gaussian-soliton shaped pulses within a recirculating fiber loop buffer. We believe that this is the first time Gaussian-soliton pulses are considered for the transmission of OTDM signals within a communication system. The simulation model is based on the nonlinear Schrodinger equation (NLSE) and accounts for fiber loss within the communications channel. At this stage pulse interactions are not considered and direct modulation of the launched pulses is assumed. Simulation results for bit error rate (BER) performance at different buffer loop numbers and eye diagrams for buffered and unbuffered cases are presented.

Comprehensive modelling of wave propagation in photonic devices

A simple and powerful modeling method is established to resolve travelling waves inside photonic devices. The basic idea is to transform usual space-time coordinates (z,t) into a mixed grid (u,v) in which waves propagate along their characteristic lines, resulting in an inherent numerical stability, as well as easy interpretation of all parametric variables and their derivatives. Beside examples of distributed-feedback (DFB) laser and semiconductor optical amplifier (SOA), we will discuss possible extension of the method toward higher-order precision, as well as its applications in ultra-fast pulse reshaping, laser dynamics, and nonlinear interactions. The aim is to offer a method for the handling of wave-propagating problems in photonic devices in general.

High precision simulation of a mode locked ring laser using SOA and fiber for generation of λ=1.55µm pulse train

A fiber ring laser with a semiconductor optical amplifier (SOA) as active component is investigated using a hybrid model. The SOA is studied using a newly-established 4th-order time-domain algorithm, which includes the nonlinear effects of carrier depletion and recovery, as well as gain dispersion. Comparison with existing analytical results shows that this algorithm can attain a relative precision of a few parts per thousand (~10-3) or better, which is essential for predicting waveform of optical pulse. The transmission in other parts of the ring laser is carried out in frequency domain. Our model predicts a pulse width of ~10ps with a 10GHz external modulation, and reveals higher stability, better waveform, as well as easier locking conditions with dispersion-compensating fiber (DCF). A diffraction-limited Gaussian pulse train can be obtained, with its carrier frequency effectively red-shifted due to band-pass filter. All these are in good agreement with our experimental observations.

Dispersion-managed ring laser using SOA and dispersion-compensating fibre for pulse reshaping and clock recovery

Using semiconductor optical amplifier (SOA) as gain medium and active mode-locker, and a dispersion-compensating fibre (DCF) to manage cavity dispersion as well as to control and remedy pulse shape, we report an all-optical clock recovery device capable of continuously recovering the clock frequency of optical return-to-zero (RZ) signals with 10 to 12.5 GHz repetition rate. The recovered clock is chirp-free Gaussians at diffraction limit with low timing jitter of ~200 fs. We employ intra-cavity DCF in order to eliminate chirp and asymmetry of SOA-amplified pulses. This SOA+DCF ring configuration allows us to recover easily the clock over 40 nm tuning range corresponding to the SOA gain bandwidth.