Thermal Effects in Integrated Dfb Laser-EA Modulator Device

This book examines thermal crosstalk in monolithically integrated Distributed Feedback (DFB) lasers and Electroabsorption (EA) modulators used in high-capacity optical fiber communication systems. While integrated DFB laser–EA modulator sources enable high-speed operation up to 40 Gb/s, their performance is limited by chirp induced by thermal interaction between the laser and modulator sections. Through a combination of experimental investigation and finite element method (FEM) simulations, this work analyzes the mechanisms of heat generation, propagation, and their impact on wavelength stability. Experimental results obtained from devices fabricated at NTT Laboratories, operating at 1.55 µm, reveal that increased EA modulator bias leads to higher power dissipation, localized heating, and a corresponding wavelength shift in the laser. The study confirms that thermal coupling between the integrated sections is the primary cause of chirp degradation.