A loss-based, magnetic field sensor implemented in a ferrofluid infiltrated microstructured polymer optical fiber
By using the experimental set-up of Fig.1(b), different magnetic field fluxes were applied perpendicular to the fiber axis, and unpolarised spectral measurements were obtained, revealing that the short wavelength band cut-off of the ferrofluid infiltrated MPOF shifts to longer wavelengths versus magnetic increasing field flux. The maximum spectral shift of ~60nm was obtained for a magnetic field flux of 2KGauss, or alternatively, considering the transmission at a fixed wavelength of 633 nm, an
~11dB reduction in transmission was observed. The corresponding transmission changes measured at
833nm under the same magnetic fields are less than 1.8dB. With this excitation scheme the minimum detectable field flux was 85Gauss, resulting in a normalized transmission modulation of 0.02dB at
633nm. Such types of transmission data are useful when fiber connectorized devices are developed.
FIG. Supl.
(a) Unpolarised transmission spectra of the 1cm ferrofluid infiltrated MPOF for different magnetic field strengths, measured using the set-up (b) presented in Fig. 1. The spectral discontinuity

located at 650nm is due to artifact of the OSA. (b) Square points: Transmission changes probed at
633nm and normalized versus transmission changes at 800nm for different magnetic field strengths applied in the ferrofluid infiltrated fiber. Circles: Short wavelength band slope shift traced at -60dB, transmission level.