Reduction of phase-induced intensity noise in a fiber-based coherent Doppler lidar using polarization control

Abstract

Optimization of signal-to-noise ratio is an important aspect in the design of optical heterodyne detection systems such as a coherent Doppler lidar (CDL). In a CDL, optimal performance is achieved when the noise in the detector signal is dominated by local oscillator shot-noise. Most modern CDL systems are built using rugged and cost-efficient fiber optic components. Unfortunately, leakage signals such as residual reflections inherent within fiber components (e.g. circulator) can introduce phaseinduced intensity noise (PIIN) to the Doppler spectrum in a CDL. Such excess noise may be a few orders of magnitude above the shot-noise level within the relevant CDL frequency bandwidth -corrupting the measurement of typically weak backscattered signals. In this study, observation of PIIN in a fiber-based CDL with a master-oscillator poweramplifier tapered semiconductor laser source is reported. Furthermore, we experimentally demonstrate what we believe is a newly proposed method using a simple polarization scheme to reduce PIIN by more than an order of magnitude.

A review of turbulence measurements using ground-based wind lidars

“…Improvement in lidar technology -new, cheaper solidstate lasers for coherent detection lidars with integrated optical amplification are being developed and tested (Hansen and Pedersen, 2008;Rodrigo and Pedersen, 2008). These may greatly expand the use of lidars for wind measurements, but they are not specifically tailored for turbulence measurements.…”

A review of turbulence measurements using ground-based wind lidars

“…3. Improvement in lidar technology -new, cheaper solidstate lasers for coherent detection lidars with integrated optical amplification are being developed and tested (Hansen and Pedersen, 2008;Rodrigo and Pedersen, 2008). These may greatly expand the use of lidars for wind measurements, but they are not specifically tailored for turbulence measurements.…”

Comparative study of the performance of semiconductor laser based coherent Doppler lidars

“…Such linewidth corresponds to a suitable few hundred meters of coherence length -the typical remote sensing range required in most wind-energy applications of CDL. However, the measured MOPA-SL linewidth is several orders of magnitude larger than that of a FL, which means that PIIN (phase-related noise) may introduce deleterious excess noise if not mitigated [6][7]10].…”

“…Due to these challenges, Lidar developers redirected their attention to embodiments based on a more expensive laser technology, namely, the fiber-laser and fiber-amplifier (FLFA) tandem. Recently, we initiated a reinvestigation of SL-based CDL systems to tackle the abovementioned problems [8][9][10]. Our efforts focused on two novel SL sources as potential emitters for developing an "all-semiconductor-laser" wind Lidar for field operation.…”