Designing magnetic field filter based on no-core fiber assisted by a ferrofluid

Magnetic nanoparticles and an in-line no-core fiber (NCF) Mach Zehnder interferometer are combined to create a unique magnetic field filter that is experimentally demonstrated and theoretically investigated by COMSOL6.1. Multiphysics, multimode interference (MMI), and self-image form the basis of the operation. The cascaded single-mode, no-core, single-mode (SNCS) fiber design of a tunable filter powered by magneto-optical fluids (MOF) was described using the technique of finite element modeling (FEM). Three materials were used as MOFs. The maximum wavelength tunability of the filter is around 113 nm. From 1538 to 1651 nm, the transmission light is increased and red shifted when the magnetic field increases from 0 to 75 mT, as a result of the RI of the surrounding MOF being increased. Experimentally found the maximum tunability of the magnetic field filter was about 19.2 nm (1537.7–1556.9 nm) at concentration 0.4%. When the magnetic field is changed from 0 to 30 mT, change 5 mT each step. The relationships between the transmission dips and magnetic field exhibit a very strong linear response, which is a necessary condition for the practical filter. This device has a wide tuning range, is very reliable, and is inexpensive when compared to other tuning methods. The device can be used in optical communication, fiber laser technology, spectroscopy, and fiber sensors. To the best of our knowledge, this is the first No-Core fiber-based magnetic field MMI tunable filter to be produced experimentally.