2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/91243We propose a quantum cryptographic system based on a planar lightwave circuit (PLC) and report on optical interference experiments using PLC-based unbalanced Mach-Zehnder interferometers (MZIs). The interferometers exhibited high-visibility (>0.98) interference even when the polarisation in the optical fibre connecting the two MZIs was randomly modulated. The results demonstrate that a PLC-based setup is suitable for achieving a polarisation-insensitive phase-coding cryptographic system.Submitted to Electronics LettersQuantum Physicstext