ABSTRACT
A swept source (SS)-based circular-state (CS) polarization-sensitive optical coherence tomography (PS-OCT) constructed entirely with polarization-maintaining fiber optics components is proposed with the experimental verification. By means of the proposed calibration scheme, bulk quarter-wave plates can be replaced by fiber optics polarization controllers to, therefore, realize an all-fiber optics CS SSPS-OCT. We also present a numerical dispersion compensation method, which can not only enhance the axial resolution, but also improve the signal-to-noise ratio of the images. We demonstrate that this compact and portable CS SSPS-OCT system with an accuracy comparable to bulk optics systems requires less stringent lens alignment and can possibly serve as a technology to realize PS-OCT instrument for clinical applications (e.g., endoscopy). The largest deviations in the phase retardation (PR) and fast-axis (FA) angle due to sample probe in the linear scanning and a rotation angle smaller than 65 deg were of the same order as those in stationary probe setups. The influence of fiber bending on the measured PR and FA is also investigated. The largest deviations of the PR were 3.5 deg and the measured FA change by ~12 to 21 deg. Finally, in vivo imaging of the human fingertip and nail was successfully demonstrated with a linear scanning probe.
Subject(s)
Fiber Optic Technology , Tomography, Optical Coherence/methods , Calibration , Endoscopy/methods , Equipment Design , Fingers/pathology , Fourier Analysis , Humans , Image Processing, Computer-Assisted/methods , Nails/pathology , Optics and Photonics , Reproducibility of Results , Signal Processing, Computer-Assisted , Signal-To-Noise RatioABSTRACT
The path imbalance (PI) of the two-arm fiber-optic interferometric sensor is a substantial parameter; a precise value of millimeters is required. Currently the precision reflectometry and the millimeter optical time-domain reflectometry are used to measure the tiny optical path difference, but the performances of these measurements are limited from the length and the resolution of the PI. We propose a new method accomplished by interferometer to accurately measure millimeters to within a few decimeters of the PI.
ABSTRACT
In general applications, the output signals of the fiber-optic interferometric sensor (FOIS) need some demodulation techniques to linearly demodulate the sensing phase signal. The common signal demodulation circuit of the FOIS is passive homodyne demodulation using phase-generated carrier [(PGC) demodulation]. Preliminary analysis of the research demonstrates that a variation in the output demodulated signal is related to the length of the fiber, and the output demodulated signal will approach zero at some certain lengths of the fiber. To improve the performance of the FOIS, it is necessary to develop the modified PGC demodulation to compensate for the propagation delay of the fiber.
ABSTRACT
We have proposed and demonstrated a multi-wavelength-switchable and uniform erbium-doped fiber laser using unbalanced in-line Sagnac Interferometer. By employing this simple scheme and through the proper control of the polarization controller, we were able to achieve uniform multi-wavelength operation of up to 84 laser lines with the signal-to- noise ratio over 20dB and 0.8-nm wavelength switching at room temperature. Again, we generated more than 300 lines, 0.1-m wavelength switching and good power stability (
ABSTRACT
A counting signal processing technique of the fiber-optic interferometric sensor is proposed. The technique is capable of counting the numbers of the maximum and minimum of the output interferometric signal in a specific time duration, and it can be used as the basis to distinguish the sensing phase signal. It can also be used as a signal detector on applications such as intrusion detection. All sensors are subject to aging of the optical components and bending loss, and therefore the output signal of each sensor may vary with time. We propose a counting level normalization technique to compensate for these variations and to obtain the correct counting numbers.
ABSTRACT
We have proposed and demonstrated a high-power C+L-band erbium amplified spontaneous emission source using an optical circulator with double-pass and bi-directional configuration, which can provide a high output power of 177.8 mW with a ripple of 5 dB and a wide line width of 81.0 nm (1525.1-1606.1 nm) without adding any external spectra-flattening components. This designed configuration is also considered relaxing resonant lasing for averaged power stability with +/- 0.013 dB, allowing high pumping efficiency of 32.8%.
