Characterizing power-dependent chirp dynamics of DML based on a time lens

Directly modulated lasers (DMLs) are extensively employed for short-reach photonic interconnection systems, but the interplay between their chirp and chromatic dispersion (CD) of standard single mode fiber (SSMF) leads to signal distortion, frequency-selective power fading, and reduced effective bandwidth. Thus, it is vital to characterize the chirp dynamic of DML. Here, we experimentally demonstrate a time-lens-based method to discriminably characterize chirp coefficients of a DML, including the adiabatic chirp coefficient κ and the linewidth enhancement factor α. Moreover, the time-lens-based setup has the dynamic observation capability of DML chirp dynamics in relation to both power and time. Experimental validation indicates that a measurement range of up to 19.9 for parameter α and 51 GHz/mW for parameter κ can be achieved, when the DML driven by a 1.33 GHz electrical signals has variable optical powers from 1.2 mW to 3.6 mW.