Suppression of nonlinear frequency sweep in an optical frequency-domain reflectometer by use of Hilbert transformation

2005 ◽  
Vol 44 (35) ◽  
pp. 7630 ◽  
Author(s):  
Tae-Jung Ahn ◽  
Ji Yong Lee ◽  
Dug Young Kim
Keyword(s):  
Frequency Domain ◽  
Hilbert Transformation ◽  
Optical Frequency ◽  
Nonlinear Frequency ◽  
Frequency Sweep

High-speed optical-frequency domain imaging by one frame imaging within one single frequency sweep

2007 ◽  
Author(s):  
Hiroyuki Furukawa ◽  
Takuji Amano ◽  
DongHak Choi ◽  
Hideaki Hiro-Oka ◽  
Kohji Ohbayashi
Keyword(s):  
Frequency Domain ◽  
High Speed ◽  
Single Frequency ◽  
Optical Frequency ◽  
Frequency Sweep ◽  
Optical Frequency Domain Imaging

scholarly journals Ultimate Spatial Resolution Realisation in Optical Frequency Domain Reflectometry with Equal Frequency Resampling

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4632
Author(s):  
Zhen Guo ◽  
Gaoce Han ◽  
Jize Yan ◽  
David Greenwood ◽  
James Marco ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Spatial Resolution ◽  
Optical Frequency ◽  
Measured Temperature ◽  
Nonlinear Frequency ◽  
Equal Frequency ◽  
Distributed Temperature Sensing ◽  
Rayleigh Backscattering ◽  
Optical Frequency Domain Reflectometry ◽  
Frequency Domain Reflectometry

A method based on equal frequency resampling is proposed to suppress laser nonlinear frequency sweeping for the ultimate spatial resolution in optical frequency domain reflectometry. Estimation inaccuracy of the sweeping frequency distribution caused by the finite sampling rate in the auxiliary interferometer can be efficiently compensated by the equal frequency resampling method. With the sweeping range of 130 nm, a 12.1 µm spatial resolution is experimentally obtained. In addition, the sampling limitation of the auxiliary interferometer-based correction is discussed. With a 200 m optical path delay in the auxiliary interferometer, a 21.3 µm spatial resolution is realised at the 191 m fibre end. By employing the proposed resampling and a drawing tower FBG array to enhance the Rayleigh backscattering, a distributed temperature sensing over a 105 m fibre with a sensing resolution of 1 cm is achieved. The measured temperature uncertainty is limited to ±0.15 °C.

scholarly journals A serial optical frequency-domain imaging study of early and late vascular responses to bioresorbable-polymer sirolimus-eluting stents for the treatment of acute myocardial infarction and stable coronary artery disease patients: results of the MECHANISM-ULTIMASTER study

2021 ◽  
Author(s):  
Tomonori Itoh ◽  
◽  
Hiromasa Otake ◽  
Takumi Kimura ◽  
Yoshiro Tsukiyama ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Coronary Artery Disease ◽  
Coronary Artery ◽  
Frequency Domain ◽  
Stable Coronary Artery Disease ◽  
Imaging Study ◽  
Optical Frequency ◽  
Bioresorbable Polymer ◽  
Artery Disease

AbstractThe purpose of this study was to assess early and late vascular healing in response to bioresorbable-polymer sirolimus-eluting stents (BP-SESs) for the treatment of patients with ST-elevation myocardial infarction (STEMI) and stable coronary artery disease (CAD). A total of 106 patients with STEMI and 101 patients with stable-CAD were enrolled. Optical frequency-domain images were acquired at baseline, at 1- or 3-month follow-up, and at 12-month follow-up. In the STEMI and CAD cohorts, the percentage of uncovered struts (%US) was significantly and remarkably decreased during early two points and at 12-month (the STEMI cohort: 1-month: 18.75 ± 0.78%, 3-month: 10.19 ± 0.77%, 12-month: 1.80 ± 0.72%; p < 0.001, the CAD cohort: 1-month: 9.44 ± 0.78%, 3-month: 7.78 ± 0.78%, 12-month: 1.07 ± 0.73%; p < 0.001 respectively). The average peri-strut low-intensity area (PLIA) score in the STEMI cohort was significantly decreased during follow-up period (1.90 ± 1.14, 1.18 ± 1.25, and 1.01 ± 0.72; p ≤ 0.001), whereas the one in the CAD cohort was not significantly changed (0.89 ± 1.24, 0.67 ± 1.07, and 0.64 ± 0.72; p = 0.59). In comparison with both groups, differences of %US and PLIA score at early two points were almost disappeared or close at 12 months. The strut-coverage and healing processes in the early phase after BP-SES implantation were significantly improved in both cohorts, especially markedly in STEMI patients. At 1 year, qualitatively and quantitatively consistent neointimal coverage was achieved in both pathogenetic groups.

scholarly journals An Optical Frequency Domain Angle Measurement Method Based on Second Harmonic Generation

Sensors ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 670
Author(s):  
Wijayanti Dwi Astuti ◽  
Hiraku Matsukuma ◽  
Masaru Nakao ◽  
Kuangyi Li ◽  
Yuki Shimizu ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Second Harmonic Generation ◽  
Frequency Domain ◽  
Harmonic Generation ◽  
Measurement Method ◽  
Second Harmonic ◽  
Angle Measurement ◽  
Laser Source ◽  
Optical Frequency ◽  
Measurable Range

This paper proposes a new optical angle measurement method in the optical frequency domain based on second harmonic generation with a mode-locked femtosecond laser source by making use of the unique characteristic of the high peak power and wide spectral range of the femtosecond laser pulses. To get a wide measurable range of angle measurement, a theoretical calculation for several nonlinear optical crystals is performed. As a result, LiNbO3 crystal is employed in the proposed method. In the experiment, the validity of the use of a parabolic mirror is also demonstrated, where the chromatic aberration of the focusing beam caused the localization of second harmonic generation in our previous research. Moreover, an experimental demonstration is also carried out for the proposed angle measurement method. The measurable range of 10,000 arc-seconds is achieved.

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