Capturing the Instantaneous Spectral Response of a MEMS Swept Laser Source Using a Quasi-Static Tunable Filter

The performance of the sensing and imaging applications based on swept laser sources (SLS) are strongly affected by the dynamic characteristics of the laser such as the instantaneous spectral linewidth, peak output power, spectral range, and the maximum operating speed. In this paper, the experimental extraction of the instantaneous parameters of an SLS is addressed, where the source is based on a fiber ring containing a deeply etched silicon micro-electro-mechanical system (MEMS) tunable filter and a semiconductor optical amplifier. A characterization method is introduced and analyzed, and the practical considerations for applying this method are discussed. The method is first applied on a simple MEMS tunable filter and the extracted spectral response is compared to the static response obtained using the optical spectrum analyzer. Then the method is applied on the SLS to extract its performance in the forward and backward wavelength sweep directions. The instantaneous spectral linewidth and peak output power and their variations with sweeping speeds up to 2000 nm/ms, pumping currents up to six times the threshold current, and fiber ring lengths in the range of 20-80 m are extracted and discussed.