Distributed acoustic sensing using dynamic range suppression

A distributed optical fiber sensing/distributed acoustic sensing system comprising:

• a length of optical sensing fiber;
• a distributed optical fiber sensing/distributed acoustic sensing interrogator in optical communication with the length of optical sensing fiber, said interrogator including:
• a laser light source for generating optical probe pulses and introducing them into the length of optical sensing fiber;
• a coherent receiver that receives Rayleigh backscatter resulting from the probe pulses traversing the optical sensing fiber;
• a dynamic range suppressor that suppresses the dynamic range of the Rayleigh backscatter prior to coherent detection;
• and
• an optical amplitude modulator positioned before the coherent receiver such that the Rayleigh backscatter signal is applied to the optical amplitude modulator before the coherent receiver;
• wherein a drive voltage for the optical amplitude modulator is generated in a feedback loop including an envelope detector that recovers a slowly varying optical envelope of the Rayleigh backscatter signal, followed by a signal conditioner that generates the drive voltage for the optical amplitude modulator exhibiting a bias voltage and amplitude swing;
• wherein the signal conditioner exhibits a concave nonlinear function implemented in analog or digital electronics and is configured to produce additional dynamic range suppression.