Effect of laser diode phase noise on coherent sensing systems

The laser frequency noise is of crucial importance in coherent sensing applications. Indeed, the frequency noise of a laser has a direct influence on the lineshape and the linewidth, farther influence on the measuring accuracy. This topic is particularly interesting for laser diodes (LD), which optical properties make them key-devices for optical communications and Coherent Sensing systems. Phase noise in LD and the related problems that arise when such lasers are employed in coherent optical sensing systems are investigated. Applications to metrology and to new sensing schemes are described, experimental results are reported and the overall performances of the sensors are assessed.