Analysis on spatial and temporal resolution in photonic time stretch frequency domain reflectometry based fully distributed fiber Bragg grating sensors

We propose and experimentally demonstrate fully distributed strain sensing along the length of a linearly chirped fibre Bragg grating with simultaneously high spatial and temporal resolution based on photonic time stretch frequency domain reflectometry (PTS-FDR). The distributed strain information is reconstructed from the instantaneous RF frequency of a temporal interference waveform via short-time Fourier transform analysis. The utility of the proposed method is characterized by analysing the spatial and temporal resolution obtained. An ultrafast strain measurement at a speed of 50 MHz with a high spatial resolution of 31.5 µm over a gauge length of 25 mm and a strain resolution of 9.1 µ? have been achieved

All-optical high-speed temporal random pattern generation based on photonic time stretch

We propose a novel all-optical temporal random pattern generation scheme based on photonic time stretch involving cascaded Mach-Zehnder interferometers (MZIs) with different chirped spectral response. The overall spectral response represents a broadband random spectral pattern. Temporal random patterns can then be generated thanks to photonic time stretch which mirrors spectrum encoding to temporal waveform. Tuning of the generated temporal patterns is achieved using a rapidly tunable optical delay module in one of the MZIs

Bayesian Estimation of CIR Model

Abstract: This article concerns the Bayesian estimation of interest rate models based on Euler-Maruyama approximation. Assume the short term interest rate follows the CIR model, an iterative method of Bayesian estimation is proposed. Markov Chain Monte Carlo simulation based on Gibbs sampler is used for the posterior estimation of the parameters. The maximum A-posteriori estimation using the genetic algorithm is employed for finding the Bayesian estimates of the parameters. The method and the algorithm are calibrated with the historical data of US Treasury bills

Ultrafast Interrogation of Fully Distributed Chirped Fibre Bragg Grating Strain Sensor

A novel ultrafast and high spatial-resolution interrogation method for fully distributed chirped fibre Bragg grating sensors based on photonic time-stretch frequency-domain reflectometry is presented. Real-time interrogation at measurement speed of 50 MHz with a spatial resolution of 35 µm was experimentally demonstrated

High spatial and temporal resolution interrogation of fully distributed chirped fiber Bragg grating sensors

A novel interrogation technique for fully distributed linearly chirped fiber Bragg grating (LCFBG) strain sensors with simultaneous high temporal and spatial resolution based on optical time-stretch frequency-domain reflectometry (OTS-FDR) is proposed and experimentally demonstrated. LCFBGs is a promising candidate for fully distributed sensors thanks to its longer grating length and broader reflection bandwidth compared to normal uniform FBGs. In the proposed system, two identical LCFBGs are employed in a Michelson interferometer setup with one grating serving as the reference grating whereas the other serving as the sensing element. Broadband spectral interferogram is formed and the strain information is encoded into the wavelength-dependent free spectral range (FSR). Ultrafast interrogation is achieved based on dispersion-induced time stretch such that the target spectral interferogram is mapped to a temporal interference waveform that can be captured in real-Time using a single-pixel photodector. The distributed strain along the sensing grating can be reconstructed from the instantaneous RF frequency of the captured waveform. High-spatial resolution is also obtained due to high-speed data acquisition. In a proof-of-concept experiment, ultrafast real-Time interrogation of fully-distributed grating sensors with various strain distributions is experimentally demonstrated. An ultrarapid measurement speed of 50 MHz with a high spatial resolution of 31.5 μm over a gauge length of 25 mm and a strain resolution of 9.1 μϵ have been achieved