Intrinsic optical fibre sensing based on integrated mode division multiplexing

This study addresses a significant deficiency; the absence of integrated solutions to real-time fiber integrity monitoring and intrusion detection. An optimized solution to this problem which is both practical and scalable is highly coveted. Our approach to providing such a solution is to use the femtosecond laser direct-write (FLDW) process for the fabrication of novel optical waveguide circuits and the creation of an integrated hybrid-wavelength optical fiber sensing platform based on spatial mode-division multiplexing which is capable of operating across standard single-mode fiber as used in the telecommunications industry.The development of integrated, parametric implementations of optical spatial-division multiplexing and fiber sensing mechanisms is a key step towards maturation of the photonics industry. This thesis reports on the design, simulation and fabrication of integrated optical code division multiplexers capable of performing higher order mode sensing in industry standard G.652 single-mode optical fiber. The efficacy of this sensing platform was verified via the demonstration of a novel, intrinsic optical fiber torsion sensor based on intra-modal cross-talk, capable of augmenting existing fiber integrity monitoring techniques. Further-more, the successful application of this technique to single-mode fiber unlocks the potentialfor exploiting optical fiber telecoms infrastructure for large scale distributed sensing.