Presently used magnetic target location methods are greatly affected by geomagnetism and involve complex solution processes. To address these problems, herein, a linear method based on the two-point gradient full tensor is proposed. Moreover, principle of single-point positioning analyzed in detail. Based this principle, model constructed. A Measuring at two locations using for calculation model, more precise achieved. The simulation results show that proposed significantly reduces relative...

The demodulation algorithm based on 3 × coupler in a fiber-optic hydrophone array has gained extensive attention recent years. traditional method uses circulator to construct the normal path-match interferometry; however, problem of increasing asymmetry three-way signal be demodulated is easily overlooked. To provide solution, we report pretreatment for demodulation. We use cubic spline interpolation perform nonlinear fitting reflected pulse train and calculate peak-to-peak values single...

This paper investigates a 1.7 mm diameter ultra-weak fiber Bragg grating (UWFBG) hydrophone towed array cable for acoustic direction finding. The mechanism of the underwater waves received by this integrated-coating sensitizing optical is deduced, and it shown that amplitude its response varies with sound wave. An anechoic pool experiment carried out to test performance such array. selection six sensing fibers, each which coiled into 9 cm ring suspended in water receive signals. average...

In the field of aviation anti-submarine warfare, magnetic detection systems often result in a large number false alarms due to inability effectively distinguish between local geomagnetic anomaly background and target anomaly. To address this problem, paper proposes matching method for underwater targets. This is based on measured data sea area, reference map area generated by interpolation Kriging method; then, signal extracted from real-time acquired are matched similarity metric algorithm;...

In order to verify the validity of regional reference grating method in solve strain/temperature cross sensitive problem actual ship structural health monitoring system, and meet requirements engineering, for sensitivity coefficients method, national standard measurement equipment is used calibrate temperature coefficient selected FBG sensor strain this modal. And thermal expansion steel ships calibrated with water bath method. The calibration results show that 28.16pm/°C within -10~30°C,...

In this paper, a method of detecting the central wavelength ultra-weak chirped fiber Bragg grating is proposed, based on correlation coefficient to solve problem calculating wavelength, in case wideband reflection spectrum jitter. A mathematical model jitter with piecewise step function superimposed by Gaussian noise built. By moving relative positions, curve their coefficients obtained, and horizontal coordinate corresponding maximum found, determine it. Then, variation trajectories between...

In order to ensure that a perimeter security system can work effectively, convenient and effective event detection algorithm has an important engineering significance. Given the above background, in this paper, we propose high reliability intrusion recognition method vibration sensing system, based on ultra-weak fiber Bragg grating array, by using dimensional random matrix. We obtain sensitivity optical interference signal constructing patch-matched then compose demodulated into...

We report on current theoretical and experimental results of echo pulses based ultra-weak Fiber Bragg Gratings (uwFBGs), using intensity compensation to solve the signal distortion caused by light pulse delay. Cubic Spline Interpolation is applied, leading better robustness for interference intensity. Then linear value obtained comparing peak in order correct attenuation three-way optical path. improvements over conventional demodulation algorithm 3×3 coupler with circulator. The have shown...

Aiming at the problem that attitude changes will cause sway errors of fluxgate, firstly, change error model is constructed theoretically, and influence on three-axis fluxgate analyzed; secondly, in order to improve measurement accuracy reduce caused by attitude, calibration method for proposed. Furthermore, established. Finally, effectiveness verified simulation actual experiment. The uniaxial absolute can be up 4.64% a minimum. effect good, calibrated data basically meet needs.

Easy wavelength division multiplexing array is the outstanding advantage of fiber-optic laser hydrophone, and injection reflected light from external cavity will have a significant impact on performance hydrophone array, which one problems that must be solved for engineering application array. In this article, by constructing combined model, influence distributed feedback (DFB) fiber theoretically analyzed, characteristics are studied. The theoretical calculation shows length threshold 1.96m...

In order to design and fabricate high-performance fiber gratings distributed feedback lasers, the monitoring of AC DC components core refractive index modulation during grating engraving was studied. Based on Bragg equation coupled mode theory, average variation fringe visibility were calculated by center wavelength transmission spectrum depth. The experiment boron-germanium co-doped fiber, germanium-doped erbium-doped photosensitive carried out their data obtained. Experiment also showed...

For the axial stretching fiber laser hydrophone, a is often exposed to flexural interference. A theoretical model for vibration of was therefore constructed in this paper explore low frequency anti-interference mechanism response an axially tensioned hydrophone (FLH). specific packaging structure used finite element comparison and simulation. Packaged FLHs were tested response. The simulation test results reveal that flexible attachment at both ends leads lower amplitude compared with rigid...