Study of the Influence of Various Stress-Based Mechanisms on Polarization of an SM mPOF for the Development of Useful Devices

In contrast to conventional polymer optical fibres (POFs), single-mode microstructured POFs (SM mPOF) exhibit polarization properties that make them potentially interesting for their use in the design and development of polarimetric fibre optic systems. In spite of the theoretical sixfold symmetry of the microstructure that yields zero linear birefringence, a measurement technique reveals us that the SM mPOF behaves as a linear birefringent system with clearly defined optical axes and characteristics. Regarding externally induced birefringence mechanisms acting upon the SM mPOF, either bend- and pressure-induced retardations or twist-induced light rotation follow the behaviour predicted theoretically. More specifically, bend-induced retardation varies linearly with the inverse square of the bending radius of the fibre, and in the case of asymmetrical lateral stress, pressure-induced retardation varies with the applied force. As to twist-induced rotation, the electric field rotates linearly with the angle through which the fibre is twisted. All cases are highly reproducible phenomena that, if used advantageously, may yield useful mPOF-based polarimetric optical devices not exploited yet.