We report mode missing and modal instability of uncooled Fabry-Perot (FP) l
asers for the temperature range from -45 to 85 degreesC and their effect on
transmission performance. Using the time domain laser model (TDLM), mode m
issing has been modeled in FP lasers with structural defects in the active
layer. Using this model, we have estimated eye opening penalty (EOP) due to
missing modes up to 2.5 Gbps data rate. These simulation results suggest t
hat FP lasers should have less than two missing modes for stable operation
and high performance for optical data links.