Phase-sensitive Optical Low-coherence Reflectometry Research Articles

Polarization sensitive optical low-coherence reflectometry for blood glucose monitoring in human subjects

A device based on polarization sensitive optical low-coherence reflectometry is developed to monitor blood glucose levels in human subjects. The device was initially tested with tissue phantom. The measurements with human subjects for various glucose concentration levels are found to be linearly dependent on the ellipticity obtainable from the home-made phase-sensitive optical low-coherence reflectometry device. The linearity obtained between glucose concentration and ellipticity are explained with theoretical calculations using Mie theory. A comparison of results with standard clinical methods establishes the utility of the present device for non-invasive glucose monitoring.

Time-Frequency Analysis for an Efficient Detection and Localization of Side-Coupled Cavities in Real Photonic Crystals

We propose and demonstrate here the high efficiency of concurrent time and frequency analysis to detect and unambiguously identify the coupled cavities in real photonic crystals containing imperfections and/or process-induced disorder. This procedure when applied to reflectograms recorded using phase-sensitive optical low-coherence reflectometry allows a straightforward and complete assessment of cavities (spectral and spatial localization in addition to photon lifetime) over a wide spectral range. Considering such a reflectogram (recorded in ~ 2 s), we show that this procedure greatly eases the evaluation of cavities under guiding conditions in real photonic crystals by discriminating their signature from the in-plane scattering induced by disorder.

Versatile Characterization of Specialty Fibers Using the Phase-Sensitive Optical Low-Coherence Reflectometry Technique

Emergence of new fibers families induces considerable requirements in terms of characterization and metrology (group delay, chromatic dispersion, birefringence, bending losses, etc.). The optical low-coherence reflectometry (OLCR) technique is demonstrated as a versatile method for the characterization of most types of optical fiber. A synthesis of multiple analysis concerning different families of specialty fibers including rare-earth-doped fibers, few-mode fibers, and microstructured fibers will be presented. OLCR allows measuring precisely the group velocity dispersion value for both polarization modes and birefringence. It is also possible to measure small refractive-index variations in a pumped Erbium-doped fiber. Unique dispersive properties of higher order modes fiber offer novel solutions for dispersion compensation or nonlinear effects management. OLCR can allow each LP mode characterization without the requirement for mode converters. A new method, called ldquotime-wavelength reflection mapping,rdquo based on the OLCR interferogram processing is applied to the determination of chromatic dispersion of each guided LP mode whatever their group index. Finally, different characterization results concerning photonics crystal fibers with guiding based on the conventional total internal reflection principle (high-index guiding) or photonic bandgap effect (low-index guiding) will be presented.

Optical low-coherence reflectometry for complete chromatic dispersion characterization of few-mode fibers

A phase-sensitive optical low-coherence reflectometry (OLCR) technique is demonstrated to simultaneously measure the absolute chromatic dispersion values of each guided LP mode of a few-mode fiber. We show that the OLCR technique requires only short samples of fiber (<1 m) and has no need for high-ratio mode converters to reach an accurate wavelength-dependent group delay evolution of every mode. As an example we present for the first time to our knowledge a direct and complete analysis of few-mode fibers with high, low, positive, and negative modal dispersion values, leading to chromatic dispersion parameters in good agreement with theoretical predictions.

Characterization of Fiber Bragg Gratings by Phase-Sensitive Optical Low-Coherence Reflectometry

Optical low-coherence reflectometry (OLCR) is a very useful metrology tool to characterize optical fiber components such as fiber Bragg gratings (FBGs). These components find a wide variety of applications in the telecommunication and sensor industry. Hence, their characteristics must be precisely analyzed. A high-resolution OLCR setup is presented as a useful investigation technique and detailed in this paper. The precise characterization of different FBGs is shown

DS-OCDMA encoder/decoder performance analysis using optical low-coherence reflectometry

Direct-sequence optical code-division multiple-access (DS-OCDMA) encoder/decoder based on sampled fiber Bragg gratings (S-FBGs) is characterized using phase-sensitive optical low-coherence reflectometry (OLCR). The OLCR technique allows localized measurements of FBG wavelength and physical length inside one S-FBG. This paper shows how the discrepancies between specifications and measurements of the different FBGs have some impact on spectral and temporal pulse responses of the OCDMA encoder/decoder. The FBG physical lengths lower than the specified ones are shown to affect the mean optical power reflected by the OCDMA encoder/decoder. The FBG wavelengths that are detuned from each other induce some modulations of S-FBG reflectivity resulting in encoder/decoder sensitivity to laser wavelength drift of the OCDMA system. Finally, highlighted by this OLCR study, some solutions to overcome limitations in performance with the S-FBG technology are suggested

Phase-sensitive optical low-coherence reflectometry technique applied to the characterization of photonic crystal fiber properties

Localized measurements of group-velocity dispersion and birefringence of photonic crystal fibers are achieved with a phase-sensitive optical low-coherence reflectometry technique. This technique is efficient for fiber samples no longer than 1 m. Theoretical simulations are in good agreement with experimental results. As a result, the stress-induced birefringence proves to be at most 1 order of magnitude below the geometrical-shape birefringence.

Detection of neural activity using phase-sensitive optical low-coherence reflectometry

We demonstrate non-contact sub-nanometer optical measurement of neural surface displacement associated with action potential propagation. Experimental results are recorded from nerve bundles dissected from crayfish walking leg using a phase-sensitive optical low coherence reflectometer. No exogenous chemicals or reflection coatings are applied. Transient neural surface displacement is less than 1 nm in amplitude, 1 ms in duration and is coincident with action potential arrival to the optical measurement site. Because the technique uses back-reflected light, noninvasive detection of various neuropathies may be possible.