Computer-aided analysis of signals from a low-coherence Fabry-Pérot interferometer used for measurements of biological samples

The aim of the study was to develop a method for computer-aided analysis of signals obtained from
noninvasive measurements of biological samples using a low-coherence Fabry-Pérot interferometer.
Optical measurement setup has the advantage of not requiring any physical contact between the probe
and the sample under study, while low-coherence interferometry is not affected by the uncertainty of
measurements longer than one wavelength, inherent to laser-based solutions.

The measurement setup consists of: an optical processor (Optical Spectrum Analyzer Ando AQ6319
with wavelength resolution of 1 pm, wavelength accuracy of ±50 pm, and close-in dynamic range of 60 dB),
a superluminescent diode (Superlum Broadlighter S1300-G-I-20, with the following optical parameters:
central wavelength λ₀ = 1290 nm and bandwidth Δλ = 50 nm, and Gaussian spectral intensity distribution),
and a low-finesse fiber-optic Fabry-Pérot interferometer.

It was experimentally determined that the measurement set-up provides good quality data while maintaining
simple configuration, and an immunity for changes of the optical polarization.

The main obstacle to overcome while designing the computer-based part of the setup was ensuring immunity to
noise that is inevitably affecting the measurement, while remaining sensitive to the meaningful information
contained within the signal. Various solutions were considered theoretically, and further evaluated on real
and simulated signals, to determine the optimal filtering and peak detection method.