Data Pattern Dependence of VCSEL Far-Field Distributions

Abstract

Abstract-The far field divergence angle distribution of verticalcavity surface-emitting lasers is found to exhibit dependence on the data pattern driving the lasers. Two 50% duty cycle 1.25-Gb/s data patterns chosen to cause the same thermal conditions but with frequency content differing by a factor of 16 resulted in changes in the beam profile distributions with up to a 30% power variation in the central on-axis portion of the beam. Examination of the temporal waveforms as a function of far field angle revealed overshoot in the on-axis power and undershoot in the off-axis portion of the beam.Index Terms-Beam divergence, data pattern dependent, far field, laser diode, multimode fiber optic.

30-Gb/s 3$\,\times\,$3 Optical Mode Group-Division-Multiplexing System With Optimized Joint Detection

“…When a single mode source with a Gaussian profile is used to realize selective launching, the power for all launched modes changes linearly with the power fluctuation of the source. Compared to overfilled launching with using a VCSEL whose mode pattern is data pattern dependent [6] so that power changes for different modes are different, the laser influence to modal noise can be basically neglected assuming phase changes of modes at the output are slow, which can be satisfied when the transmission fiber is kept stable. The maximum power fluctuation for different radial offset launching over a time period of 20 s is 0.2 dB in the case a 185/250 m GI-MMF is coupled with a 50/125 m GI-MMF, smaller than the case when a SMF is used [4].…”