Measurements of dynamic photon fluctuations in a directly modulated 1.5-μm InGaAsP distributed feedback laser

We report new results on dynamic photon statistics of 1.5-μm distributed feedback buried heterostructure lasers when driven from below threshold at 1.5-GHz modulation. In contrast to Fabry-Perot lasers, a transient turn-on delay fluctuation in the total power of about 50 ps is observed with no evidence of modal partition. These fluctuations can be explained by the randomized nature of the spontaneous emission. Typically occurring at low frequencies, these turn-on effects can result in system timing errors. This impairment can be eliminated by modulating entirely above threshold or minimized by modulating at frequencies below a few hundred megahertz.