Fuel detection system using OTDR with multimode fiber

Abstract

This work presents an optical fiber based sensor for fuel detection adapted to an optical time domain Reflectometer (OTDR) as an analyzer. The sensing system consists of a portion of removal clad multimode fiber (MMF) as sensing part connected in between a receive and launch fibre. The sensing part was prepared by removing 1 cm of the MMF cladding layer using chemical etching technique. Both launch and receive fibres are using single mode fibre (SMF) where OTDR is connected to the Launch Fibre while Receive Fibre has one end with air interface.The sensor response is based on optical return loss recorded from OTDR trace when sensing part in contact with fuel where in this work diesel and benzene were tested. OTDR measurement revealed that the return loss recorded from OTDR increases when etching time of the MMF is increased. The highest return loss of 2.462 dB and 3.099 dB were recorded in diesel and benzene respectively with etching time of 20 minutes. The etching time up to 25 minutes however found to cause the fibre core become too thin and at the end the fiber core can completely dissolved. Further enhancement of detection sensitivity has achieved by using two point MMF sensing system.