A Sandwich Structure for the Magnetic Field Detection With Supermodes Interference

A sandwich structure between two fiber cores and the magnetic fluid has been designed and tested for the magnetic field detection. The magnetic fluid is clamped between two parallel cores in the photonic crystal fiber. The broadband light is propagated longitudinally with periodical coupling between two parallel cores. Even and odd supermodes with different propagation constants are formed, which result in the supermodes interference. The group effective refractive indices of supermodes depend on that of the magnetic fluid under different magnetic field, and the magnetic field is measured by interrogating the wavelength shift of the transmission spectrum. The experimental results show that the sensitivity of up to 143 pm/Oe is achieved.