A strong roll-off performance in Optical Coherence Tomography (OCT) is essential for imaging the inner ear, as it enables better depth resolution and penetration into the delicate structures within the temporal bone. This ensures higher-quality images and improved visualization of inner ear pathologies, thereby rendering OCT a valuable non-invasive tool for accurate diagnosis and assessment of inner ear conditions. In this work, we propose a spectral-domain OCT design that incorporates a frequency comb light source to enhance the penetration depth through improved roll-off performance. A broadband (~87nm at 3dB) comb source was developed centered near 1300nm, producing ~1000 lines spaced by a constant dk (~0.83cm-1), which were coupled into a Mach-Zehnder interferometer and then detected by a spectrometer. Our initial results demonstrate an >80% improvement in 3-dB roll-off compared to the same system without the comb, i.e., with a broadband light source as used in the classical SD-OCT design.
We propose a fully distributed optical fiber sensor capable of performing spectrally-resolved detection of visible light radiation. The sensor is based on monitoring the temperature change between two optical fibers with different coating colors. In our implementation, the temperature is simultaneously monitored in a black-coated fiber (which is highly sensitive to all input wavelengths) and a color-coated fiber, which basically acts as an optical stop-band filter for a certain input color. By comparing the temperature behavior attained for each fiber, it is possible to obtain information of the wavelength/color of a given optical radiation present in the environment. Suitable calibration could lead to distributed colorimetry measurements.
Monitoring the presence of external electric fields over large distances and detecting losses along power transmission networks, is of extreme importance nowadays due to concerns with environment, efficiency, cost and safety. In this work, we evaluate a method to achieve distributed measurements of the quadratic electro-optic Kerr effect in silica fibers in a distributed way. For this purpose, we integrate a twin-hole fiber filled with BiSn alloy electrodes and monitor its electric-field induced refractive index (RI) change Δn by using a chirped-pulse phase-sensitive OTDR (CP-ΦOTDR). By exploiting its high sensitivity (RI changes of the order of 10-9 ), we demonstrate that the proposed system is able to detect the intrinsic quadratic electrooptic nonlinearity (the electric Kerr effect) in the fiber, an effect that is usually considered to be too weak to be exploited for practical applications. Additionally, we show that the CP-ΦOTDR is sufficiently sensitive to measure the electric Kerr effect with untreated standard telecommunication fibers under realistic fields.
The proposed technique consists in an optical fiber resonator interrogated for sensor characterization, implementing an alternative technique for dynamic range improvement. Such technique relies on the analysis of an added-signal caused by signal saturation, which occurs due to the broadening of the laser pulse. A wide study for different pulse widths is presented in this work, namely for 100 ns, 5 μs and 20 μs, being the last one related to the emergence of an added-signal for the proposed configuration. The behavior of the waveform in the presence of an intensity sensor is also characterized.
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