title: Path-length-resolved measurements of multiple scattered photons in static and dynamic turbid media using phase-modulated low-coherence interferometry.
abstract: In optical Doppler measurements, the path length of the light is unknown. To facilitate quantitative measurements, we develop a phase-modulated Mach-Zehnder interferometer with separate fibers for illumination and detection. With this setup, path-length-resolved dynamic light scattering measurements of multiple scattered light in static and dynamic turbid media are performed. Optical path length distributions spanning a range from 0 to 11 mm are measured from the area under the phase modulation peak around the modulation frequency in the power spectrum. A Doppler-broadened phase modulation interference peak is observed that shows an increase in the average Doppler shift with optical path length, independent of absorption. Validation of the estimated path length distributions is done by measuring their deformation for increasing absorption and comparing these observations with predictions based on Lambert-Beer's law.
authors.affiliation: University of Twente, Biomedical Technology Institute, Biophysical Engineering Group, P. O. Box 217, NL-7500AE Enschede, The Netherlands. b.varghese@utwente.nl
authors.forename: Babu
authors.initials: B
authors.lastname: Varghese
authors.forename: Vinayakrishnan
authors.initials: V
authors.lastname: Rajan
authors.forename: Ton G
authors.initials: TG
authors.lastname: Van Leeuwen
authors.forename: Wiendelt
authors.initials: W
authors.lastname: Steenbergen
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation*; D007368:Interferometry / Q000295:instrumentation* / Q000379:methods; D017078:Laser-Doppler Flowmetry / Q000295:instrumentation* / Q000379:methods; D009391:Nephelometry and Turbidimetry / Q000295:instrumentation* / Q000379:methods; D017785:Photons; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D041623:Tomography, Optical Coherence / Q000295:instrumentation* / Q000379:methods