scholarly journals Investigation and Mitigation of Noise Contributions in a Compact Heterodyne Interferometer

Sensors ◽  
2021 ◽  
Vol 21 (17) ◽  
pp. 5788
Author(s):  
Yanqi Zhang ◽  
Adam S. Hines ◽  
Guillermo Valdes ◽  
Felipe Guzman
Keyword(s):  
Noise Source ◽  
Laser Frequency ◽  
Noise Estimation ◽  
Frequency Noise ◽  
Correction Algorithm ◽  
Dynamic Measurements ◽  
Heterodyne Interferometer ◽  
Order Of Magnitude ◽  
Noise Correction ◽  
Laser Interferometers

We present a noise estimation and subtraction algorithm capable of increasing the sensitivity of heterodyne laser interferometers by one order of magnitude. The heterodyne interferometer is specially designed for dynamic measurements of a test mass in the application of sub-Hz inertial sensing. A noise floor of 3.31×10−11m/Hz at 100 mHz is achieved after applying our noise subtraction algorithm to a benchtop prototype interferometer that showed a noise level of 2.76×10−10m/Hz at 100 mHz when tested in vacuum at levels of 3×10−5 Torr. Based on the previous results, we investigated noise estimation and subtraction techniques of non-linear optical pathlength noise, laser frequency noise, and temperature fluctuations in heterodyne laser interferometers. For each noise source, we identified its contribution and removed it from the measurement by linear fitting or a spectral analysis algorithm. The noise correction algorithm we present in this article can be generally applied to heterodyne laser interferometers.

Laser frequency noise measurement using an envelope-ratio method based on a delayed self-heterodyne interferometer

2019 ◽  
Vol 435 ◽  
pp. 244-250 ◽  
Author(s):  
Yimin Li ◽  
Zhuo Fu ◽  
Lei Zhu ◽  
Jie Fang ◽  
Haoran Zhu ◽  
...  
Keyword(s):  
Laser Frequency ◽  
Noise Measurement ◽  
Ratio Method ◽  
Frequency Noise ◽  
Heterodyne Interferometer

Noise source location and scaling of subsonic upper-surface blowing

2020 ◽  
Vol 19 (3-5) ◽  
pp. 191-206
Author(s):  
Trae L Jennette ◽  
Krish K Ahuja
Keyword(s):  
Strouhal Number ◽  
Noise Source ◽  
Low Frequency ◽  
Directivity Pattern ◽  
Source Location ◽  
Dipole Source ◽  
Frequency Noise ◽  
Noise Sources ◽  
Trailing Edge ◽  
Trailing Edge Noise

This paper deals with the topic of upper surface blowing noise. Using a model-scale rectangular nozzle of an aspect ratio of 10 and a sharp trailing edge, detailed noise contours were acquired with and without a subsonic jet blowing over a flat surface to determine the noise source location as a function of frequency. Additionally, velocity scaling of the upper surface blowing noise was carried out. It was found that the upper surface blowing increases the noise significantly. This is a result of both the trailing edge noise and turbulence downstream of the trailing edge, referred to as wake noise in the paper. It was found that low-frequency noise with a peak Strouhal number of 0.02 originates from the trailing edge whereas the high-frequency noise with the peak in the vicinity of Strouhal number of 0.2 originates near the nozzle exit. Low frequency (low Strouhal number) follows a velocity scaling corresponding to a dipole source where as the high Strouhal numbers as quadrupole sources. The culmination of these two effects is a cardioid-shaped directivity pattern. On the shielded side, the most dominant noise sources were at the trailing edge and in the near wake. The trailing edge mounting geometry also created anomalous acoustic diffraction indicating that not only is the geometry of the edge itself important, but also all geometry near the trailing edge.

scholarly journals Estimation of the Laser Frequency Noise Spectrum by Continuous Dynamical Decoupling

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Manchao Zhang ◽  
Yi Xie ◽  
Jie Zhang ◽  
Weichen Wang ◽  
Chunwang Wu ◽  
...  
Keyword(s):  
Noise Spectrum ◽  
Laser Frequency ◽  
Frequency Noise ◽  
Dynamical Decoupling

A Study on Exhaust Muffler Using Counter-Phase Counteract

2014 ◽  
Vol 986-987 ◽  
pp. 810-813
Author(s):  
Ying Li Shao
Keyword(s):  
Mathematical Model ◽  
Experimental Validation ◽  
Noise Source ◽  
Low Frequency ◽  
Frequency Noise ◽  
Expansion Chamber ◽  
Band Noise ◽  
Exhaust Noise ◽  
Perforated Pipe ◽  
The Mathematical Model

The exhaust noise, which falls into low-frequency noise, is the dominant noise source of a diesel engines and tractors. The traditional exhaust silencers, which are normally constructed by combination of expansion chamber, and perforated pipe or perforated board, are with high exhaust resistance, but poor noise reduction especially for the low-frequency band noise. For this reason, a new theory of exhaust muffler of diesel engine based on counter-phase counteracts has been proposed. The mathematical model and the corresponding experimental validation for the new exhaust muffler based on this theory were performed.

scholarly journals Impact of laser frequency noise on high-extinction optical modulation

2020 ◽  
Vol 28 (26) ◽  
pp. 39606
Author(s):  
Gavin N. West ◽  
William Loh ◽  
Dave Kharas ◽  
Rajeev J. Ram
Keyword(s):  
Laser Frequency ◽  
Optical Modulation ◽  
Frequency Noise

Laser frequency noise immunity in multiplexed displacement sensing

2011 ◽  
Vol 36 (5) ◽  
pp. 672 ◽  
Author(s):  
Danielle M. R. Wuchenich ◽  
Timothy T.-Y. Lam ◽  
Jong H. Chow ◽  
David E. McClelland ◽  
Daniel A. Shaddock
Keyword(s):  
Noise Immunity ◽  
Laser Frequency ◽  
Frequency Noise

scholarly journals Dynamical decoupling of laser phase noise in compound atomic clocks

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Sören Dörscher ◽  
Ali Al-Masoudi ◽  
Marcin Bober ◽  
Roman Schwarz ◽  
Richard Hobson ◽  
...  
Keyword(s):  
Phase Noise ◽  
Phase Measurement ◽  
Local Oscillator ◽  
Frequency Instability ◽  
Laser Frequency ◽  
High Signal ◽  
Frequency Noise ◽  
Atomic Clocks ◽  
Dynamical Decoupling ◽  
Measurement Protocol

Abstract The frequency stability of many optical atomic clocks is limited by the coherence of their local oscillator. Here, we present a measurement protocol that overcomes the laser coherence limit. It relies on engineered dynamical decoupling of laser phase noise and near-synchronous interrogation of two clocks. One clock coarsely tracks the laser phase using dynamical decoupling; the other refines this estimate using a high-resolution phase measurement. While the former needs to have a high signal-to-noise ratio, the latter clock may operate with any number of particles. The protocol effectively enables minute-long Ramsey interrogation for coherence times of few seconds as provided by the current best ultrastable laser systems. We demonstrate implementation of the protocol in a realistic proof-of-principle experiment, where we interrogate for 0.5 s at a laser coherence time of 77 ms. Here, a single lattice clock is used to emulate synchronous interrogation of two separate clocks in the presence of artificial laser frequency noise. We discuss the frequency instability of a single-ion clock that would result from using the protocol for stabilisation, under these conditions and for minute-long interrogation, and find expected instabilities of σy(τ) = 8 × 10−16(τ/s)−1/2 and σy(τ) = 5 × 10−17(τ/s)−1/2, respectively.

The Effect of Airfoil Shape on Trailing Edge Noise

2019 ◽  
Vol 27 (02) ◽  
pp. 1850020 ◽  
Author(s):  
Seongkyu Lee
Keyword(s):  
Boundary Layer ◽  
Noise Source ◽  
Source Region ◽  
Low Frequency ◽  
Suction Side ◽  
Frequency Noise ◽  
Pressure Side ◽  
Trailing Edge ◽  
Trailing Edge Noise ◽  
Naca0012 Airfoil

This paper investigates the effect of airfoil shape on trailing edge noise. The boundary layer profiles are obtained by XFOIL and the trailing edge noise is predicted by a TNO semi-empirical model. In order to investigate the noise source characteristics, the wall pressure spectrum is decomposed into three components. This decomposition helps in finding the dominant source region and the peak noise frequency for each airfoil. The method is validated for a NACA0012 airfoil, and then five additional wind turbine airfoils are examined: NACA0018, DU96-w-180, S809, S822 and S831. It is found that the dominant source region is around 40% of the boundary layer thickness for both the suction and pressure sides for a NACA0012 airfoil. As airfoil thickness and camber increase, the maximum source region moves slightly upward on the suction side. However, the effect of the airfoil shape on the maximum source region on the pressure side is negligible, except for the S831 airfoil, which exhibits an extension of the noise source region near the wall at high frequencies. As airfoil thickness and camber increase, low frequency noise is increased. However, a higher camber reduces low frequency noise on the pressure side. The maximum camber position is also found to be important and its rear position increases noise levels on the suction side.

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