VCSEL Modeling and Parameter Extraction for Optical Link Simulation and Optimization

A single and multimode vertical cavity surface emitting laser (VCSEL) model and the associated parameter extraction using bandwidth and intensity noise measurements was proposed. To meet the growing bandwidth demand, optical VCSEL links are commonly turning to equalization, and multilevel modulation formats. The need for an accurate physics-based rate equation model is critical for the design and analysis of VCSEL links as we move past 25Gb/s. Single and multimode VCSEL models were able to accurately capture the bandwidth and noise characteristics of VCSELs over a large range of operating conditions. Through spatial mode overlaps, which cause inter and intra mode gain saturation, the multimode VCSEL model uncovered a possible source of positive and negative mode noise correlations recently discovered in VCSELs which affect RIN. Through S-parameter VCSEL characterization and intensity noise measurements, our models could extract and simulate extrinsic and intrinsic VCSEL PAM-4 performance for 100Gb/s+ short reach optical links.Ph.D

Systèmes OFDM optiques à détection directe à complexité réduite pour les communications à haut débit

A possible approach to maximize the data rate per wavelength, is to employ the high spectral efficiency discrete multitone (DMT) modulation. The work presented in this thesis mainly focuses on optimizing the power consumption and cost of DMT, that are the major obstacles to its market development. Within this context, we have first developed novel techniques permitting to discard the use of Hermitian symmetry in DMT modulations, thus significantly reducing the power consumption and the system cost. We have next proposed an asymmetric linear companding algorithm permitting to reduce the optical power of conventional DCO-OFDM modulation with a moderate complexity. A new VCSEL behavioural model based on the use of the VCSEL quasi-static characteristic was also developed to accurately evaluate the VCSEL impact on DMT modulations. Finally, we have built an experimental system to experimentally validate our proposed techniques. Several simulations and measurement results are then provided.Une approche pour augmenter le débit par longueur d'onde, est d'utiliser la modulation DMT (Discrete Multitone) à haute efficacité spectrale. Le travail présenté dans cette thèse se focalise principalement sur l'optimisation de la consommation en puissance et le coût de la DMT, qui présentent des obstacles majeurs à son industrialisation. Dans ce cadre, nous avons tout d'abord développé des nouvelles techniques permettant d'exclure la symétrie Hermitienne des modulations DMT, réduisant ainsi considérablement la consommation en puissance et le coût du système. Nous avons ensuite proposé un algorithme de compression linéaire asymétrique permettant de réduire la puissance optique de la modulation DMT avec une complexité modérée. Un nouveau modèle comportemental du VCSEL basé sur la caractéristique quasi-statique a été également développé. Nous avons enfin validé expérimentalement les techniques que nous avons proposées. Plusieurs résultats de simulations et de mesures sont ainsi présentés