Abstract

Highly linear-birefringent (HiBi) optical fibres have been widely used to transmit linearly polarised light in various applications because of their polarisation-holding properties [1]. Faraday coupling in linear-birefringent fibres have been reported previously [2,3]. Recently, an optical-fibre current sensor which makes use of the Faraday Effect to couple light resonantly from one mode to an originally-empty mode of a HiBi fibre, when the fibre is subjected to a periodic magnetic field, has been reported [4,5]. In this paper we report that the resonance of Faraday coupling is dependent on the relative axial position of the fibre and the magnetic field. This is caused by the interference of the Faraday coupled signal and the residual empty mode component, due to imperfect launching of purely linearly-polarised light into one eigenmode of a HiBi fibre.

© 1992 Optical Society of America