| Popis: |
There is great interest for distributed or multiplexed fiber optic sensor networks for process control automation. Optical Time Domain Reflectometry (OTDR) is a potentially very useful method for monitoring several sensors distributed along a fiber, but its actual capabilities, using present concepts, are too restricted to allow competitive industrial performance. We present here a novel scheme of OTDR fiber sensor multiplexing which allows, ,the monitoring of up to 50 ON/OFF switches along a given fiber under practical and realistic conditions. Detection of reflected, rather than backscattered, light makes much better use of the in-line loss introduced by each sensor, yielding a larger dynamic range which explains this very significant improvement in the number of multiplexed sensors. Theoretical considerations about this novel scheme and its limits, taking into account present OTDR technology, are presented together with experimental results of a twenty ON/OFF sensor network feasibility prototype . |
