A MULTIPOINT QUASI-DISTRIBUTED OPTICAL-FIBER PH SENSOR

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.