A vectorial magnetometer utilising a microstructured optical fibre Bragg grating infiltrated by a ferrofluid

Herein, we present a compact and fully functional, optofluidic in-fibre magnetometer, based on a MOF Bragg grating, which has been infiltrated using a ferrofluid. The demonstrated MOF device is designed for operating at the 1.5μm band and is interrogated in reflection using a 50/50 fibre coupler; the output being connected to a pigtailed photodiode and either a broadband source or a fibre pigtailed diode. The MOF used is a grape-fruit geometry Ge-doped core fibre, while the Bragg grating was fabricated using 193nm excimer laser radiation and a phase mask interferometer. This in-fibre device utilises a short length of oil based ferrofluid (Ferrotec EMG905) placed at a specific point within the length of the MOF Bragg grating; forming a lossy Fabry-Perot cavity.