Abstract: Extracting a displacement component includes: receiving a received signal resulting from an optical signal being scattered by the plurality of particles in the fluid, the received signal comprising a displacement component; mixing the received signal with a local oscillator signal to generate a mixed signal; detecting the mixed signal via a set of one or more detectors and generating a set of one or more electrical signals based on the detection; demodulating the set of one or more electrical signals to obtain the displacement component; and outputting the displacement component.