In this paper, we propose and experimentally investigate an optical sensor based on a novel combination of a long-period fiber grating (LPFG) with a permanent magnet to measure electrical current in unmanned aerial vehicles (UAVs). The proposed device uses a neodymium magnet attached to the grating structure, which suffers from an electromagnetic force produced when the current flows in the wire of the UAV engine. Therefore, it causes deformation on the sensor and thus, different shifts occur in the resonant bands of the transmission spectrum of the LPFG. Finally, the results show that it is possible to monitor electrical current throughout the entire operating range of the UAV engine from 0 A to 10 A in an effective and practical way with good linearity, reliability and response time, which are desirable characteristics in electrical current sensing.

Surveillance missions in vast, difficult access environments are responsible for logistic difficulties in comparison to using an in loco monitoring team. For this and many other reasons, solutions with robotic platforms such as unmanned aerial vehicles (UAVs), present economic advantages.

Optical fiber sensors based on long period grating (LPG) are effective devices in sensing simultaneously temperature and mechanical strain. It was shown that different shifts in the resonant bands for the transmitted spectrum of an LPG sensor can be correlated with variation in temperature or mechanical strain. This paper presents the effects of non-linearity and cross-sensibility in the LPG resonance condition arising from combined effects of temperature and mechanical strain, proposing an adjustment coefficient in order to compensate these effects in a simple and effective way, reducing uncertainties in simultaneous measurements of temperature and mechanical strain.

This work develops a continuous wave numerical model based on the spatial propagation of the pumps and signals into the optical fibre in a Raman amplification scheme that can be helpful to predict the behavior of different architectures in a remote optical fiber sensor system based on a long period grating. The numerical model is validated by experimental results and is applied in the analysis of the noise generated by Raman amplification in the remote optical sensors systems. After that, the numerical model is applied to analyze the most viable architecture to be implemented in an experimental measure in the temperature remote optical sensor with 50 km distance between the central unit and the sensor head. An electrical interrogation scheme is used due their low cost and good time response. The simulation results show 2,8 dB improvement in OSNR estimation for an optical amplification scheme using two optical fibers instead of only one for the same distance length.