High synchronization absolute distance measurement using a heterodyne and superheterodyne combined interferometer

We propose an absolute distance measurement method that employs heterodyne and superheterodyne combined interferometers to achieve synchronous detection and demodulation of multiwavelengths.Coarse and fine synthetic wavelengths are generated by a dual-longitudinal-mode He-Ne laser and four acoustic optical frequency shifters.Further,to improve phase synchronization measurement for multiwavelengths,we analyze the demodulation characteristics of coarse and fine measurement signals and adopt a demodulation method suitable for both signals.Experimental results demonstrate that the proposed method can achieve high-precision synchronous demodulation of multiwavelengths,and standard deviation is 1.7×10^(-5)m in a range of 2 m.

Dynamic spatiotemporal correlation coefficient based on adaptive weight

Risk management is an important aspect of financial research because correlations among financial data are essential in evaluating portfolio risk.Among various correlations,spatiotemporal correlations involve economic entity attributes and are interrelated in space and time.Such correlations have therefore drawn increasing attention in financial risk management.However,classical correlation measurements are typically based on either time series correlations or spatial dependence;they cannot be directly applied to financial data with spatiotemporal correlations.The spatiotemporal correlation coefficient model with adaptive weight proposed in this paper can(1)address the absolute quantity,dynamic quantity,and dynamic development of financial data and(2)be used for risk grading,financial risk evaluation,and portfolio management.To verify the validity and superiority of this model,cluster analysis results and portfolio performance are compared with a classical model with time series correlation or spatial correlation,respectively.Empirical findings show that the proposed coefficient is highly effective and convenient compared to others.Overall,our method provides a highly efficient financial risk management method with valuable implications for investors and financial institutions.

Optical Frequency Comb Frequency-division Multiplexing Dispersive Interference Multichannel Distance Measurement

An optical frequency comb(OFC)frequency-division multiplexing dispersive interference multichannel distance measurement method is proposed.Based on the OFC dispersive interference,the wide OFC spectrum is divided into multiple channels using a wavelength-division multiplexer.Under the existing light source and spectrometer,a single interference system can realize six channels of the high-precision parallel absolute distance measurement.The influence of the spectrum width and shape on the performance of the distance measurement channel is analyzed.The ranging accuracy of six channels is higher than±4μm under the optimization of a nonuniform discrete Fourier transform and Hanning window.