Differential loss magnetic field sensor using a ferrofluid encapsulated D-shaped optical fiber.

A ferrofluid immersed, D-shape optical fiber exhibits differential loss up to 12 dB with respect to an azimuthally rotating magnetic field placed around its longitudinal axis, manifested in its measured transmission power. Investigating the magneto induced refractive index and loss changes by using ferrofluid overlaid diffractive elements a differential loss mechanism is revealed, associated with the relative light polarization direction and the magnetic field application direction. The results were used for performing modal profile simulations of ferrofluid immersed D-shape optical fiber. It is demonstrated that such an optical system can act as a magnetic field sensor with field angle and intensity sensing capabilities.