Fiber modal Michelson interferometers with coherence addressing and heterodyne interrogation

A long-period-grating-based fiber optic Michelson modal interferometer with coherence addressing and heterodyne interrogation is studied as a sensing structure for measuring environmental refractive index, temperature, and liquid level. The effects of several system parameters on the measurements are investigated. Experimental results show that the sensitivity to the external refractive index increases with the order of cladding mode and with a reduction of the fiber diameter. The decrease of the fiber diameter from 125 µm down to 70 μm enhances the sensitivity to the external index by a factor of 2.7. It is also shown that the use of a silica-core fiber increases the sensitivity to the external index by a factor of 1.4 and reduces the thermal sensitivity by a factor of 2.5 compared to a standard fiber.

[1]  J. Jones,et al.  Pseudoheterodyne detection scheme for optical interferometers , 1982 .

[2]  J. H. Cole,et al.  Synthetic-heterodyne interferometric demodulation , 1982 .

[3]  A. Kersey,et al.  All-fibre 'michelson' thermometer , 1983 .

[4]  B. Y. Kim,et al.  Coherence multiplexing of fiber-optic interferometric sensors , 1985 .

[5]  A. Hamel,et al.  Coherence multiplexing using a parallel array of electrooptic modulators and multimode semiconductor lasers , 1987 .

[6]  David J. Webb,et al.  A high sensitivity refractometer based upon a long period grating Mach–Zehnder interferometer , 2002 .

[7]  Pieter L. Swart,et al.  Long-period grating Michelson refractometric sensor , 2004 .

[8]  G. Rego,et al.  Arc-Induced Long-Period Gratings , 2005 .

[9]  Pieter L. Swart,et al.  Temperature-compensated optical fiber Michelson refractometer , 2005 .

[10]  Jaw-Luen Tang,et al.  Fiber-optic biochemical sensing with a colloidal gold-modified long period fiber grating , 2006 .

[11]  Jose Luis Santos,et al.  Refractive index measurement with long-period gratings arc-induced in pure-silica-core fibres , 2006 .

[12]  O. Wolfbeis.  Fiber-optic chemical sensors and biosensors. , 2000, Analytical chemistry.

[13]  Anbo Wang,et al.  Fibre-optic interferometric immuno-sensor using long period grating , 2006 .

[14]  Chang-Qing Xu,et al.  High Sensitivity Long-Period Grating MichelsonRefractometer with Reduced Fiber Cladding , 2006 .

[15]  Zhengtian Gu,et al.  Optical fiber long-period grating with solgel coating for gas sensor. , 2006, Optics letters.