Digital Phase Demodulation in Heterodyne Interferometry

The emergence of tunable diode lasers from the communications industry creates a need in diagnostic heterodyne sensors for flexible FM demodulation techniques. By using tunable lasers, it becomes efficient to generate Heterodyne Beat Frequencies (HBF) that can be tuned to over 10 GHz with frequency stabilities to within 100 kHz. These diode lasers are small in size, rugged, reliable, and relatively cheap. These characteristics make diode lasers the ideal light sources for sensors to be integrated into industrial processes, smart structures, and on-line quality control or NDE