Unveiling delay time resolved phase noise statistics of narrow linewidth laser via coherent optical time domain reflectometry.
Laser with high spectral purity plays a crucial role in high precision optical metrology and coherent communication. Thanks to the rapid development of laser frequency stabilization, the laser phase noise can be remarkably compensated, allowing its ultra narrow linewidth subject to mostly quantum limit. Nevertheless, the accurate characterization of phase noise statistics and its linewidth of a highly coherent laser remains ambiguous and challenging. Here, we present an approach capable of revealing delay time resolved phase noise statistics of a coherent laser based on coherent optical time domain reflectometry (COTDR) in which distributed Rayleigh scattering along a delay fiber essentially allows a time of flight mapping of a heterodyne beating signal associated with delay time dependent phase information from a single laser source. Ultimately, this novel technique facilitates precise measurement of ultra narrow laser linewidth by exploiting its delay time resolved phase jitter statistics of random fiber laser with pump lasers of various linewidths, confirmed with the analytical modeling and numerical simulations.
Optics express