Beat noise reduction utilizing the transient acoustic-wave response of an optical fiber in Brillouin grating-based optical low coherence reflectometry

2018 ◽  
Vol 57 (18) ◽  
pp. 5235 ◽  
Author(s):  
Kazumasa Takada ◽  
Shin-ichi Satoh
Keyword(s):  
Acoustic Wave ◽  
Optical Fiber ◽  
Noise Reduction ◽  
Low Coherence ◽  
Beat Noise ◽  
Wave Response ◽  
Optical Low Coherence Reflectometry

scholarly journals Signal-to-Noise Ratio of Brillouin Grating Measurement with Micrometer-Resolution Optical Low Coherence Reflectometry

Sensors ◽  
2020 ◽  
Vol 20 (3) ◽  
pp. 936
Author(s):  
Kazumasa Takada ◽  
Shin-ichi Satoh ◽  
Akiya Kawakami
Keyword(s):  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
Pump Light ◽  
Logarithmic Scale ◽  
Signal To Noise ◽  
Light Power ◽  
Low Coherence ◽  
Beat Noise ◽  
Noise Ratio ◽  
Optical Low Coherence Reflectometry

Signal-dependent speckle-like noise was the dominant noise in a Brillouin grating measurement with micrometer-resolution optical low coherence reflectometry (OLCR). The noise was produced by the interaction of a Stokes signal with beat noise caused by a leaked pump light via square-law detection. The resultant signal-to-noise ratio (SNR) was calculated and found to be proportional to the square root of the dynamic range (DR) defined by the ratio of the Stokes signal magnitude to the variance of the beat noise. The calculation showed that even when we achieved a DR of 20 dB on a logarithmic scale, the SNR value was only 7 on a linear scale and the detected signal tended to fluctuate over ±14% with respect to the mean level. We achieved an SNR of 24 by attenuating the pump light power entering the balanced mixer by 55 dB, and this success enabled us to measure the Brillouin spectrum distributions of mated fiber connectors and a 3-dB fused fiber coupler with a micrometer resolution as examples of OLCR diagnosis.

Optical low-coherence reflectometry (OLCR) characterization of efficient Bragg gratings in optical fiber

1993 ◽  
Author(s):  
Hans G. Limberger ◽  
Pierre-Yves Fonjallaz ◽  
Patrick Lambelet ◽  
Rene-Paul Salathe ◽  
Christophe Zimmer ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Bragg Gratings ◽  
Low Coherence ◽  
Optical Low Coherence Reflectometry

scholarly journals The feasibility of a noise elimination method using continuous wave response of therapeutic ultrasound signals for ultrasonic monitoring of high-intensity focused ultrasound treatment

2021 ◽  
Author(s):  
Ryo Takagi ◽  
Toshikatsu Washio ◽  
Yoshihiko Koseki
Keyword(s):  
Noise Reduction ◽  
High Intensity ◽  
Focused Ultrasound ◽  
Continuous Wave ◽  
High Intensity Focused Ultrasound ◽  
Hifu Treatment ◽  
Noise Elimination ◽  
Tissue Samples ◽  
Wave Response ◽  
Failure Conditions

Abstract Purpose In this study, the robustness and feasibility of a noise elimination method using continuous wave response of therapeutic ultrasound signals were investigated when tissue samples were moved to simulate the respiration-induced movements of the different organs during actual high-intensity focused ultrasound (HIFU) treatment. In addition to that, the failure conditions of the proposed algorithm were also investigated. Methods The proposed method was applied to cases where tissue samples were moved along both the lateral and axial directions of the HIFU transducer to simulate respiration-induced motions during HIFU treatment, and the noise reduction level was investigated. In this experiment, the speed of movement was increased from 10 to 40 mm/s to simulate the actual movement of the tissue during HIFU exposure, with the intensity and driving frequency of HIFU set to 1.0–5.0 kW/cm2 and 1.67 MHz, respectively. To investigate the failure conditions of the proposed algorithm, the proposed method was applied with the HIFU focus located at the boundary between the phantom and water to easily cause cavitation bubbles. The intensity of HIFU was set to 10 kW/cm2. Results Almost all HIFU noise was constantly able to be eliminated using the proposed method when the phantom was moved along the lateral and axial directions during HIFU exposure. The noise reduction level (PRL in this study) at an intensity of 1.0, 3.0, and 5.0 kW/cm2 was in the range of 28–32, 38–40, and 42–45 dB, respectively. On the other hand, HIFU noise was not basically eliminated during HIFU exposure after applying the proposed method in the case of cavitation generation at the HIFU focus. Conclusions The proposed method can be applicable even if homogeneous tissues or organs move axially or laterally to the direction of HIFU exposure because of breathing. A condition under which the proposed algorithm failed was when instantaneous tissue changes such as cavitation bubble generation occurred in the tissue, at which time the reflected continuous wave response became less steady.

Surface acoustic wave response to ambient humidity in graphite oxide structures

2011 ◽  
Vol 99 (5) ◽  
pp. 051915 ◽  
Author(s):  
R. Rimeika ◽  
J. Barkauskas ◽  
D. Čiplys
Keyword(s):  
Acoustic Wave ◽  
Surface Acoustic Wave ◽  
Graphite Oxide ◽  
Ambient Humidity ◽  
Wave Response
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