Measurement of signal-to-noise ratio for a mixture of coherent and incoherent sources using digital sampling oscilloscope

摘要

Signal-to-noise ratios for a coherent laser source and a mixture of a laser source with a narrow band amplified spontaneous emission source are directly measured using a digital sampling oscilloscope. The measurement for a coherent source is found unreliable due to the low level of shot-noise compared to the thermal noise. On the other hand, the measurement for a mixed source is found in good agreement with theoretical predictions within 1dB error.