Fiber-optic vector acoustic receiver based on adaptive holographic interferometer

A mobile scalar–vector acoustic receiver is proposed, experimentally implemented and investigated. The key components of the receiver are (a) the six-channel fiber-optic coil-type sensor configured as to detect three projections of acoustic intensity vector, (b) the six-channel optical phase demodulator based on six-channel adaptive holographic interferometer configured with use of dynamic holograms multiplexed in a photorefractive crystal of cadmium telluride and (c) the signals recording ADC-based system combined with software package for data processing. Field tests of the developed receiver applied for obtaining scalar and vector parameters of acoustic waves generated by a stationary and moving acoustic source in open air and water area are carried out. Experimental results show perceptiveness of use of the fiber-optical adaptive interferometry system for bearing of weak acoustic sources in real conditions.

Investigation Of Dual-Pump Fiber Optical Parametric Amplifier Performance Driven by Energy Transfer Between Four-Wave Mixing Process

Fiber optical parametric amplifier (FOPA) is operated based on energy transfer from pump waves to signal wave and at the end of the fiber, an idler wave is generated. This process is called four-wave mixing (FWM). Even though effects of higher-order dispersion coefficients, fiber length, fiber nonlinearity, fiber attenuation, pump powers, pump wavelength separation and distance of central pump wavelength with ZDW on gain profiles have been examined by previous researchers, but on different fiber or numerically studied using the Optisys system, analytical model or different amplitude equations. Thus, in this study, the above-mentioned parameters on the gain performance of dual pump fiber optical parametric amplifier (FOPA) using highly nonlinear shifted fiber (HNL-DSF) as a medium will be numerically investigated using ode45 function in Matlab. The gain at a certain wavelength can be obtained by solving 4 coupled amplitude equations with fiber loss and pump depletion that govern the four-wave mixing (FWM) process of pumps, signal and idler waves. Simulations results indicate positive gives poor or no gain, meanwhile, an addition of to negative widens the bandwidth, but there is no significant effect with the addition of . Besides, an increase of fiber length, nonlinearity and pump powers improve gain performance, but an increase of fiber loss decays the gain amplitude. Increment of pump separation will enhance flatness of gain at wavelength far from central wavelength but results in an increase of gain reduction at the central wavelength. Lastly, must be positive, not too small and not bigger than 1.125nm to get a high, broader and lesser ripples gain.

Irregular layout of fiber-optical lines for tomographic monitoring of nautical structures

В статье рассматривается решение волоконно-оптической томографической задачи для мониторинга морских конструкций на основе новой, впервые публично представляемой, схемы укладки волоконно-оптических измерительных линий распределенной сети. В предлагаемой схеме укладки устраняется сдерживающий фактор линейности линий малоракурсной томографии и впервые анализируются возможности неравномерной схемы укладки. Сравнение предложенной схемы укладки с классическими схемами показало преимущество в точности определения места воздействия при уменьшении числа измерительных линий. Численное сравнение полученных результатов вычислительных экспериментов с ранее полученными результатами по другим схемам сканирования показали перспективность предлагаемого способа. Использование неравномерных схем укладок волоконно-оптических линий, наряду с применением систем искусственного интеллекта к информации на выходе этих линий, позволяет их изгибать теоретически на любых поверхностях морских конструкций, огибая углы балок, шпангоутов, неровных уплотнений и других подобных выпуклых поверхностей, для проектирования на их основе систем мониторинга состояния медленных физических полей на поверхностях со сложным произвольным профилем. The article discusses the solution of fiber-optical tomographic problem for monitoring nautical structures based on new layout of fiber-optic measuring lines. In the proposed scheme, the limiting factor of linearity of low-angle tomography lines is eliminated. The possibilities of Irregular layouts are analyzed. Comparison of the proposed layout with classical options showed gain in the accuracy of determining the location of the impact while reducing the number of measuring lines. A numerical comparison of the obtained results of computational experiments with previously obtained results for other scanning schemes showed the promise of the proposed method. Artificial intelligence systems are applied to the output data of these lines. This allows, in theory, to use uneven fiber-optic lines on any surfaces of nautical structures. At the same time, they will be able to bend around the corners of girders, ribs, uneven seals and other similar convex surfaces. All this will make it possible to design on their basis monitoring systems for slow physical fields on random profile surfaces.