Optical-fibre remote sensing system of low-level propane gas using a 1·68 μm InGaAs light emitting diode

A fully optical remote detection system for propane gas was realized in real time by a near-infrared absorption method employing a 2-km long low-loss silica optical-fibre link in conjunction with an InGaAs light emitting diode at 1.68 μm. The detection sensitivity for propane gas in air, which was achieved to lower than 2 torr, i.e. nearly 12% of the lower explosion limit for propane, demonstrates the practical feasibility and reliability of this kind of fibre-optic remote gas sensor system with electrical and thermal safety.