Remote sensing network to detect and identify organic vapours

In this work, a novel CWDM (Coarse Wavelength Division Multiplexing) network that multiplexes intensity modulated optical fibre sensors is presented. These transducers are based on a sensing material that suffers reversible changes in its optical properties in presence of organic vapours. This compound is fixed onto cleaved ended single mode optical fibres pigtails using Electrostatic Self-Assembly method. As their response depends on intensity changes, a referencing signal is simultaneously generated to eliminate the effect of optical source power fluctuations. Thus, a parallel array of phaseshifted fibre Bragg gratings (PS-FBGs) is included to obtain the referencing signal. Looking forward to remote sensing applications, an Erbium doped fibre amplifier (EDFA) is included in the header of the network to reach up to 4 km of distance. Four new sensors have been multiplexed and exposed to saturated atmospheres of methanol and ethanol individually, showing different response and recovery times in each case. Finally, we checked that our sensors were able to distinguish between pure and kerosene polluted water probes in terms of response and recovery times as well.