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In this paper, we describe a low cost optical sensor of water level based on fiber bending effect associated to the use of an elastomeric membrane. The sensor proposed has a particular design to be simple, reliable, and low cost. It is suitable to be used in tubes of embankment dams, tanks, and reservoirs. The sensor uses a standard single mode fiber and can measure the water levels up to 10 m or more, choosing the appropriate membrane. This paper describes the development of the sensor, a theoretical modeling, and the results of laboratory and field tests. Seven sensors were installed in an embankment dam where they have been used in a real time monitoring system based in optical time domain reflectometry.Index Terms-Optical sensor, bend loss, dam's monitoring, liquid level sensor. 1530-437X

We experimentally investigate the impact of chromatic dispersion (CD), post-filtering effects (PFEs), and backreflection-induced penalties on intensityremodulation topologies based on self-seeded directly modulated reflective semiconductor optical amplifiers (RSOAs) acting as downstream carriers. Optical eye diagrams and power penalties as a function of link reach and reflection tolerances, as well as optical spectra and bit error rate (BER) performance up to 100 km, are measured and directly compared to a conventional prespectrum slicing light (PSSL) injection topology, in order to highlight the advantages and drawbacks of the self-seeding scheme. Downstream and bidirectional reaches up to 80 and 60 km, respectively, with a maximum 2 dB power penalty (for a BER of 10 −12 ) at 1.25 Gb/s operation are demonstrated in our self-seeding configuration, which enables enhanced resilience to CD and PFE effects while surpassing the conventional PSSL scheme in about 40 km.

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