A numerical model of an all-fiber Nd3+ laser passively Q-switched with Cr4+ is presented. The repetition rate, average output power, and pulse width have been calculated with the same parameters as those of an experimental setup of another group. We found a qualitative agreement between the two results. The validated model has been used on another proposed setup to investigate and optimize laser parameters. The low and high self-impulse amplitude regimes were found for different Cr4+ ion densities. The optimal efficiency of the high regime was established when the saturable absorber density increases.
An autoregressive method to analyze the fringe pattern observed in holographic interferometry is reported. Considering the impact of a 30 dB signal-to-noise ratio, we have shown that the reconstruction of the simulated symmetric profiles with 3, 4, and 5 fringes produces a maximum error of 0.300, 0.520, and 1.015 rad, respectively. The reconstruction of an asymmetric profile gives a larger error. The method was also applied to a recent fringe pattern. Our results are in qualitative agreement with those obtained using other methods.
We have adapted the point model for the study of an all-fiber laser doped with Nd3+ and Q-switched by a saturable fiber absorber doped with Cr4+. Calculations of the output power of the 1084 nm laser are considered as a function of the pump power supplied by a 790 nm laser diode. The analysis of the simulation results reveals the existence of pulsed, sinusoidal, and dc operating regimes.
Curvature of a multimode optical fiber reduces the numerical aperture and induces radiation losses. We study this phenomenon and we present the "model disadaptation" method to calculate the local numerical aperture and the power attenuation. We exploit the bending effect on the local numerical aperture to propose a new intrinsic optical fiber temperature sensor. The modeling results are experimentally validated for two kinds of optical fibers: a silica-silicone optical fiber and a silica-polymer optical fiber. The simulation and the experimental results are in good accordance and show that the silica-silicone optical fiber sensor can operate between −60 and 152°C with a good response. The silica-polymer optical fiber temperature sensor can sense the temperatures between −249 and 83°C with a good response.
The frequency of the holographic fringe signal is proportional to the measured object deformation or displacement. Fast Fourier transform (FFT) is the most commoly used signal processing technique for analyzing output fringes. One problem with this approach is that a long data acquisition is required to achieve adequate deformation resolution, typically 5 to 10 fringes are needed. We propose using an autoregressive (AR) model to obtain with the same advantages deformation of an opaque object using holographic interferometry. This deformation will be estimated directly from the model parameters. The theoretical and experimental results obtained indicate that the proposed method has a good accuracy by using a small number of fringes.