A polarimetric current sensor using an orthogonally polarized dual-frequency fibre laser

We demonstrate a novel -doped fibre laser operating in orthogonally polarized dual-frequency modes and its application to electric current sensing with frequency read-out. A Faraday rotating mirror and spatial hole burning effects in a gain medium and in a saturable absorber are utilized to control the lasing mode and polarization. The polarization mode beat frequency changes linearly in response to the non-reciprocal circular birefringence induced by an external magnetic field. When the laser was applied to sensing an alternating electric current with a simple phase-locked loop signal processing scheme, the slope coefficient of 8.0 kHz per turn and the noise equivalent current of 460 per turn were obtained. The new current sensor is immune to perturbations in the lead fibres.

[1]  G. Day,et al.  Annealing of linear birefringence in single-mode fiber coils: application to optical fiber current sensors , 1991 .

[2]  B Y Kim,et al.  Longitudinal mode control in few-mode erbium-doped fiber lasers. , 1996, Optics letters.

[3]  Richard O. Claus,et al.  A reciprocal-compensated fiber-optic electric current sensor , 1994 .

[4]  J. T. Kringlebotn,et al.  Polarimetric Er(3+)-doped fiber distributed-feedback laser sensor for differential pressure and force measurements. , 1996, Optics letters.

[5]  G. Meltz,et al.  Polarimetric heterodyning Bragg-grating fiber-laser sensor. , 1993, Optics letters.

[6]  S H Yun,et al.  Response of fiber lasers to an axial magnetic field. , 1995, Optics letters.

[7]  David A. Jackson,et al.  RAPID COMMUNICATION: Vibration immunity and Ampere's circuital law for a near perfect triangular Faraday current sensor , 1996 .

[8]  Juichi Noda,et al.  Dispersion of Verdet constant in stress-birefringent silica fibre , 1984 .

[9]  M. Martinelli.  A universal compensator for polarization changes induced by birefringence on a retracing beam , 1989 .

[10]  Gordon W. Day,et al.  Fundamentals and Problems of Fiber Current Sensors , 1996 .

[11]  S H Yun,et al.  Polarization- and frequency-stable fiber laser for magnetic-field sensing. , 1996, Optics letters.

[12]  J. Zyskind,et al.  Linewidth-narrowing mechanism in lasers by nonlinear wave mixing. , 1994, Optics letters.

[13]  N. C. Pistoni,et al.  Vibration-insensitive fiber-optic current sensor. , 1993, Optics letters.

[14]  H. K. Kim,et al.  Polarimetric fiber laser sensors. , 1993, Optics letters.