Suppressing the impact of water vapor inside optical components for optical fiber $$\hbox {H}_{2}\hbox {O}$$ H 2 O sensing system

Abstract

Water vapor inside optical components can impact the measurement result of optical fiber $$\hbox {H}_{2}\hbox {O}$$ sensing system, and the impact is described. This research focuses on two main optical components: a distributed feedback laser diode (DFB-LD) and two photodetectors (PD). The principle and implementation of an approach to suppress the inside water vapor impact are introduced. As a result, impact of water vapor inside DFB-LD on measurement can be furthest suppressed by adopting a dual-beam differential approach. Impact of water vapor inside PDs can be eliminated by adopting one easy and feasible calibration approach, which is based on temporal difference technique through an optical switch.