Highly sensitive fiber-optic torsion sensor based on an ultra-long-period fiber grating

• Published in: Optics communications 2006-10, Vol.266 (1), p.187-190
• Main Authors: Rao, Y.J., Zhu, T., Mo, Q.J.
• Format: Article
• Language: English
• Subjects: Applied sciences; Birefringence; Circuit properties; CO2 laser; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Gas lasers including excimer and metal-vapor lasers; General equipment and techniques; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Integrated optics. Optical fibers and wave guides; Lasers; Optical and optoelectronic circuits; Optical fiber sensing; Optics; Physics; Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing; Torsion sensor; Ultra-long period fiber grating; Wave optics
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/j.optcom.2006.04.045

A high sensitivity fiber-optic torsion sensor, which can measure twist rate and determine twist direction simultaneously based on a novel ultra-long-period fiber grating (ULPFG) with a period of up to several millimeters, is proposed and demonstrated. Such an ULPFG is fabricated by using the high-frequency CO2 Laser pulses exposure technique. The unique torsion characteristics of the ULPFG are simply analyzed by using the mode coupling theory and the birefringence effect. The experimental results show that the high order resonant wavelengths of the ULPFG have higher torsion sensitivities, which is several times higher than that of the normal LPFG. In addition, an intensity-type demodulation approach used to realize real-time torsion measurement is proposed and demonstrated based on the edge filtering effect of the ULPFG.