SignificanceSpectroscopic analysis of optical coherence tomography (OCT) data can yield added information about the sample’s chemical composition, along with high-resolution images. Typical commercial OCT systems operate at wavelengths that may not be optimal for identifying lipid-containing samples based on absorption features.AimThe main aim of this study was to develop a 1200 nm spectroscopic OCT (SOCT) for the classification of lipid-based and water-based samples by extracting the lipid absorption peak at 1210 nm from the OCT data.ApproachWe developed a 1200 nm OCT system and implemented a signal processing algorithm that simultaneously retrieves spectroscopic and structural information from the sample. In this study, we validated the performance of our OCT system by imaging weakly scattering phantoms with and without lipid absorption features. An orthogonal projections to latent structures-discriminant analysis (OPLS-DA) model was developed and applied to classify weakly scattering samples based on their absorption features.ResultsThe OCT system achieved an axial resolution of 7.2 μm and a sensitivity of 95 dB. The calibrated OPLS-DA model on weakly scattering samples with lipid and water-based absorption features correctly classified 19/20 validation samples.ConclusionsThe 1200 nm SOCT system can discriminate the lipid-containing weakly scattering samples from water-based weakly scattering samples with good predictive ability.
This paper discusses the detailed experimental investigations on the performance of interferometer based fiber optic
hydrophones with different Phase Generated Carrier (PGC) demodulation algorithms for their interrogation. The study
covers the effect on different parametric variations in the PGC implementations by comparison through Signal to Noise
And Distortion (SINAD) and Total Harmonic Distortion (THD) analysis. This paper discusses experiments on most
popular algorithms based on PGC like Arctangent, Differential Cross Multiplication (DCM) and Ameliorated PGC. A
Distributed Feed-Back Fiber Lasers (DFB-FL) based fiber optic hydrophone, with Mach-Zehnder Interferometer having
active phase modulator in reference arm and mechanism to cater polarization related intensity fading were used for the
experiments. Experiments were carried out to study the effects of various parameters like the type and configuration of
low pass filter, frequency of the modulation signal, frequency of acoustic signal etc. It is observed that all the three
factors viz. the type of low pass filter, frequency of modulating and acoustic signal plays important role in retrieving the
acoustic signal, based on the type of algorithms used and are discussed here.
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