RENO (Reactor Experiment for Neutrino Oscillation) has made a definitive measurement of the smallest mixing angle θ 13 in 2012, based on the disappearance of electron antineutrinos. More precise measurements have been obtained and presented on the mixing angle and the reactor neutrino spectrum, using ~800 days of data. We have observed an excess of IBD prompt spectrum near 5 MeV with respect to the most commonly used models. The excess is found to be consistent with coming from reactors. We have also successfully measured the reactor neutrino flux with a delayed signal of neutron capture on hydrogen. A future reactor neutrino experiment of RENO-50 is proposed to determine the neutrino mass hierarchy and to make highly precise measurements of θ 12 , ∆m 21 2 , and ∆m 31 2 . Physics goals and sensitivities of RENO-50 are presented with a strategy of obtaining an extremely good energy resolution toward the neutrino mass hierarchy.

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A fiber‐optic interferometric voltage sensor with a high‐sensitivity is investigated. The fiber‐optic voltage sensor is composed of an in‐line Michelson interferometer bonded to a piezoelectric transducer (PZT). The in‐line Michelson interferometer is a hollow optical fiber spliced to a single‐mode fiber at one end and cleaved at the other end. A phase shift in the sensor output signal is induced when applying an AC voltage to the PZT; and a higher‐amplitude voltage produces an output interference signal with a higher frequency. The relation between the amplitude of the applied voltage and the phase shift of the sensor output signal is found to be approximately linear and the slope of the relation graph is about 0.116 πradian/V. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1689–1691, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24434