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In order to provide a cost-effective indoor positioning and tracking service for autonomous ground vehicles and other important assets in smart factories, we report the theory and experiments for a real-time indoor positioning system using commercially available LED lamps. Inspired by the fundamental theory of the global navigation satellite system, the proposed system uses the phase difference of arrival (PDOA) approach to obtain the time difference of arrival of each carrier transmitted from individual modified LED lamps so as to estimate the receiver position. A prototype of the atto-cellular positioning system covering an area of 2.2 × 1.8 m² with a height of 2 m was designed and experimentally demonstrated. For the design, we performed a simulation based on the Crámer-Rao bound to achieve optimal LED lamp arrangement, RF power, and other parameters. Furthermore, a virtual local oscillator for the PDOA scheme was applied to reduce the hardware complexity and to ensure the processing speed. In the experiment, the receiver was mounted on a movable material buffer station in a smart workshop, and the positioning performance was validated by tracking the trajectory of the material buffer station moving within the positioning coverage area. The experimental results show that an average positioning accuracy of ~7 cm was achieved. [ABSTRACT FROM AUTHOR]

We present a compact broadband supercontinuum (SC) generation in a single-mode fluorozirconate ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber pumped by femtosecond pulses from an erbium-doped fiber laser (EDFL). The femtosecond seed pulses are generated through passive mode locking using carbon-nanotubes- based saturable absorber in EDFL ring cavity. An SC spectrum spanning from 1100 to 3200 nm with a spectral flatness of <8 dB has been obtained successfully from a single-mode ZBLAN fiber. A piecewise linear relationship of SC spectrum bandwidth with input pulse power is observed. [ABSTRACT FROM AUTHOR]