Polarisation state optimisation in observing Brillouin scattering signal in polymer optical fibres

In general, the state of polarisation (SOP) should be adjusted to optimise the signal-to-noise ratio of Brillouin measurement based on self-heterodyne detection. Although Brillouin Stokes power in silica fibres is known to be enhanced by optimising the SOP, the role of SOP optimisation in polymer optical fibres (POFs) is quite different from that in silica fibres. In this reported work, it is clarified that the role of SOP optimisation in POFs lies not in enhancing the Brillouin Stokes power but in suppressing the tail of the Rayleigh-scattered light spectrum.