An energy-time entanglement-based dispersive optics quantum key distribution (DO-QKD) is demonstrated experimentally over optical fibers of 20 km. In the experiment, the telecom band energy-time entangled photon pairs are generated through spontaneous four wave mixing in a silicon waveguide. The arrival time of photons are registered for key generating and security test. High dimensional encoding in the arrival time of photons is used to increase the information per coincidence of photon pairs. The bin sifting process is optimized by a three level structure, which significantly reduces the raw quantum bit error rate (QBER) due to timing jitters of detectors and electronics. A raw key generation rate of 151kbps with QBER of 4.95% is achieved, under a time-bin encoding format with 4 bits per coincidence. This experiment shows that entanglement-based DO-QKD can be implemented in an efficient and convenient way, which has great potential in quantum secure communication networks in the future.
An all-fiber high-sensitivity modal interferometer formed by a bent standard single-mode fiber (SMF) has been presented and demonstrated, which can be used to measure refractive indexes (RIs) of solutions and temperature. The interferometer has a simple and compact structure built with a bent bare SMF mimicking a balloon shape. Because of the curvature of bent fiber sensor, modal interference effect would occur when light propagates from the fiber core into the cladding. The measurement is achieved by monitoring the spectral shift of the modal interference. The performances of the interferometers with different bending diameters and sensitive lengths are experimentally investigated concluding the optimal bending radius as 4 mm and sensitive length 16 mm. In the RI range of 1.3493-1.3822, the corresponding sensitivity and detection limit are 225.95 nm/RIU (refractive index unit) and 3.2×10 −4 , respectively. The temperature sensitivity and detection limit of 0.418 nm/°C and 0.173°C are achieved, respectively.Index Terms-Balloon-like interferometer, bent single-mode fiber, refractive index (RI) sensing, temperature sensing.
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