Efficient multi-mode fiber to single-mode fiber coupling : High speed VCSEL characterization

This article aims at illustrating the MMF to SMF coupling using a multimode scrambler, as introduced in a previous article, to couple a Vertical Cavity Surface Emitting Diode Laser (VCSEL) laser into a ZOOM Spectra high resolution Laser Spectrum Analyzer. Indeed, VCSEL laser are really compact semiconductors laser diodes with large Numerical Aperture emission beam perpendicular to their top surface, as illustrated figure 1. VCSEL are generally fabricated by batch of millions units on a wafer using standard semiconductor technologies….

Multimode VCSEL unstability

VCSEL are now used as singlemode and multimode laser sources in many application fields. Many users are not laser expert and may discover VCSEL unstability late in a development …VCSEL Unstability can be related to two mains parameters : drive current and temperature. The following videos can help feeling how sensitive VCSEL unstability can be for a specific application. Here is a video of the spectrum of VCSEL when changing its current from 90 mA to 140 mA. From a…