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A method to optimize the gain of a fiber optical parametric amplifier (FOPA) is presented by using a genetic algorithm (GA), which can determine the parameters of FOPA and avoid the trouble of trial and error to achieve it. The effect of pump depletion on the gain characteristic of the FOPA is emphasized, and the effects of the fiber length, the wavelength, and the power of two pumps on bandwidth, flatness, and magnitude of the gain spectrum are also studied. According to the presentation, fiber length and the wavelength of the two pumps are selected to be the variable parameters in the GA. When the parameters of the fiber are determined, with the numerical simulation, the optimum combination scheme between those chosen variables could be obtained by the algorithms with the result of the gain optimization of FOPA.

Brillouin optical time domain analyzer (BOTDA) assisted by optimized support vector machine (SVM) algorithm for accurate temperature extraction is presented and experimentally demonstrated. Three typical intelligent optimization algorithms, particle swarm optimization algorithm, genetic algorithm and firefly algorithm are explored to optimize the SVM parameters. The performances of optimized SVM algorithms for temperature extraction are investigated in both simulation and experiment under different conditions for Brillouin gain spectrum collection, resulting in the significant enhancement of sensing accuracy. In particular, the extraction accuracy (i.e., smaller root mean square error value) of temperature information is improved about 4°C compared with the conventional SVM when the signal-to-noise ratio (SNR) as low as 2.5 dB and 40-ns pump pulse width are adopted in the experiment. In addition to the enhanced accuracy with good robustness, the optimized algorithms have faster processing speed than the curve fitting method, over 20-times improvement. That makes the optimized algorithms become a very promising candidate for high performance BOTDA sensors in the future.

Electromagnetic pulses (EMPs) with high intensity and frequency bandwidth can be generated during the intensive laser irradiating solid targets in inertial confinement fusion (ICF). To shield the EMPs radiation and hence protect various diagnostics in and outside the target chamber, we designed a multi-layer structure material to shield the EMPs and demonstrate experimentally and numerically shielding performance of the material structure. The thickness of the multi-layer structure material has a great influence on the EMPs shielding. It is shown that, with the increase of the material thickness, the better shielding performance is obtained, and the material structure with polytetrafluoroethylene of 0.5 mm, copper of 0.4 mm and lead of 2.4 mm reduces 448 times compared the maximum value of EMPs voltage to that without shielded. The design of multilayer structure material for EMPs shielding provides a promising way to reduce EMPs radiation, which is extremely useful for the diagnostics protection and signal processing in ICF.

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