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.

In this work we proposed a sealing method of fiber Bragg grating (FBG) in pressure sensors using electroless nickel-plating. The sensor is designed to be used in harsh environments of thermoelectric power plant engines. In order to be applied in the engine injector nozzle the FBG has just a single attached point in the pressure sensor and the combustion chamber pressure will freely compress the FBG. The fixation material used to seal the FBG in the pressure sensor is the key for the sensor performance considering the engine environment used in thermoelectric power plant. Typical level of pressure in the engine monitoring point is around 200 bar and the temperature exceed 300 °C. We detailed the method of fabrication and the characteristics of this method. Next the FBG pressure sensors using electroless nickel-plating sealing were studied and submitted to laboratorial and field trial evaluation. In addition, we evaluated the signal characteristics of the FBG pressure sensor and we compared it with a standard pressure sensor used in this application.

In this work, we propose a novel self-seeded WDM-PON topology. Unlike previous works, in our case, the self-seeding occurs in RSOAs located at the OLT, allowing upstream transmission based on carrier remodulation at the ONT. Thus, a single wavelength per user can be employed for both traffic directions while eliminating the need for an external broadband light source at the CO. A maximum bidirectional 2.5 dB power penalty for a BER of 10^-10 was obtained for an injection power level of -22 dBm into the ONT RSOAs. We also investigate the tolerance of downstream BER to downstream extinction ratio (ER_D) and self-seeding power (P_ss), as well as analyze the impact of upstream extinction level (ER_UP), injection power (P_inj) and ER_D levels on upstream BER performance, on symmetric 1.25 Gbps OOK transmission over 20 km without DTLA and FFCI mechanisms. We have successfully demonstrated downstream error free transmission (BER of 10^-12) for an as low as 3.5 dB.

In this work, we present the results of a fiber optic powered sensor for monitoring partial discharges on high voltage transformer bushings. The main advantages of the proposed system are high bandwidth, passivity, flexibility, non-intrusive, human and equipment risk free, easy installation and inherently galvanic isolation. The complete system is composed by the sensor that is one active hermetically sealed circular antenna installed near to the bushing flange, a fiber network and a control unit. The sensor is powered only by the optical power provided by one optic fiber connected to a remote optical source. At the same time, the partial discharge signals are transmitted by another optical fiber to the control unit installed in the substation room. We describe the design and the performance evaluation of the fiber optic powered antenna in laboratory.

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