Characterization of 1.55 μm VCSELs using high-resolution and high-dynamic range measurements of the CW optical spectrum

We present a methodology for the characterization of the main parameters of VCSELs for its use in direct modulation. Power response, chirp parameter alpha, linewidth, side-mode suppression ratio, relaxation oscillations peak frequency, damping rate and relative intensity noise (RIN) are obtained from measurements of the emitted optical spectrum in continuous wave (CW) operation by means of a high resolution (10 MHz) and high dynamic range (80 dB) optical spectrum analyzer. Many of the main static and dynamic parameters of VCSEL lasers can be obtained from the analysis of the optical spectrum when emitting in CW operation, but traditional spectrum analysis techniques do not achieve enough high resolution and dynamic range and high signal to noise ratio to perform it. Recent developments in high resolution optical spectrum analyzer (OSA) technology allow a deeper characterization of the main properties of VCSELs for its applications in optical communication systems by analyzing their CW emitted spectrum.