Miniaturised distributed optical fibre sensors (DOFS) based on photonic integrated circuits (PICs) for space applications

Distributed optical fibre sensors (DOFS) are highly suitable for monitoring temperature, vibration and strain using physical principles such as Raman, Rayleigh and Brillouin backscatter. They convert a standard telecom infrastructure to a sensor network providing thousands of virtual sensors per km using the intrinsic light/glass interaction during propagation. DOFS have clear benefits in certain space applications, such as the ability to embed the sensors in the structure of reusable vehicles (even for ground testing, where they could remain after testing), the very small size of the sensors and simplified wiring). DOFS could also complement earth observations from space with ground or ocean-based monitoring, e.g., of ocean currents, salinity and temperature to improve climate models. DOFS have wide terrestrial applications, such as the monitoring of energy cables including those linking offshore wind farms to the mainland. The issue with present DOFS is that the interrogators (opto-electronic unit that probes the fibre and interprets the optical signal) consist of multiple optical components linked by fibre connections that need careful, bulky, packaging and are vibration-sensitive. This has, so far, rendered them unsuitable for space applications as well as certain ground-based applications.