This paper reports the development and characterisation of a multipoin
t quasi-distributed optical fiber sensor for pH measurement. The syste
m is based on a 170 m length of 200 mu m core diameter plastic claddin
g silica fiber where sections of cladding have been removed and replac
ed with dye immobilised sol-gel glass to form sensing points. Evanesce
nt wave excitation of a dye, immobilised within 2 mm long sections of
cladding, enables the pH value of any spillage material to be determin
ed by optical time domain reflectometry along the length of the seer.
The results suggest a spatial resolution of better than 2.5 meters for
this fiber system and indicate that this arrangement could form the b
asis of a practical sensor/actuator system for chemical spillage, prov
ided that suitable dye/analyte combinations are available.