Comparative life test of 0.8-μm laser diodes for SILEX under NRZ and QPPM modulation

Abstract

The paper describes the procedures and preliminary results of accelerated life tests performed in the frame of an evaluation programme under ESA -contract. For the calculation of activation energy and median life time, and in order to investigate the drift behaviour ofoptical parameters, a conventional three temperature ageing test at 30°C, 50°C and 70°C is being performed on 80 laser diodes in total, split into two subgroups operating under quaternary pulse position modulation (QPPM) and non return to zero (NRZ) modulation at l6Mbitis with a PN-code length 2-1. The hermetically sealed diodes of the three selected laser types are operated for 3500hrs under automatic average power control with lO4mWpeak/3OmWaverage for QPPM and SlmWpeak/42mWaverage power for NRZ. The failure criterion is 30%-increase ofthe bias current, continuously monitored by computer. Intermediate measurements of the lasers PJI-curves, V/I-characteristics, far field patterns and spectra for purpose of s-calculation are performed. leasurements before and upon completion of the ageing tests consist of Pa/I-curves, V/I-characteristics, photo diode tracking ratios, spectra, mode hopping behaviours, far field patterns, wave front errors and astigmatisms and linear polarization ratios.