Coherence multiplexing of sensors based on long-period fibre grating Mach-Zehnder interferometers

A novel interrogation scheme for multiplexing the sensors based on long-period grating (LPG) Mach-Zehnder interferometers (MZIs) is proposed. Each LPG-MZI is formed by a pair of cascaded identical LPGs and induces an additional optical path difference (OPD) proportional to the centre-to-centre interval between the two LPGs. A sub-reflectogram including sensing information can be achieved when the OPD induced in one LPG-MZI is compensated by scanning one arm of a Michelson interferometer to a certain range. For multiple sensors, the grating intervals of different LPG-MZIs are set to different values to ensure that their sub-reflectograms can be well separated in time domain. The spectral response of the LPG-MZI is reconstructed from the corresponding sub-reflectogram with a fast Fourier transformation. Applications of the bending and temperature monitoring are demonstrated by measuring the signals in time domain and wavelength domain, respectively.

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

[2]  A. Vengsarkar,et al.  Optical fiber long-period grating sensors. , 1996, Optics letters.

[3]  W. Sorin,et al.  Multiplexed sensing using optical low-coherence reflectometry , 1995, IEEE Photonics Technology Letters.

[4]  S. James,et al.  Simultaneous temperature and bend sensing with long-period fiber gratings. , 2000, Optics letters.

[5]  A. Kersey,et al.  A four-element fiber grating sensor array with phase-sensitive detection , 1994, IEEE Photonics Technology Letters.

[6]  Libo Yuan,et al.  Two-loop-based low-coherence multiplexing fiber-optic sensor network with a Michelson optical path demodulator , 2005 .

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

[8]  Philippe Gallion,et al.  A generalized approach to optical low-coherence reflectometry including spectral filtering effects , 1998 .

[9]  T. Erdogan.  Fiber grating spectra , 1997 .

[10]  A. Zhang,et al.  Fiber-taper seeded long-period grating pair as a highly sensitive refractive-index sensor , 2005, IEEE Photonics Technology Letters.

[11]  M. Yamada,et al.  Analysis of almost-periodic distributed feedback slab waveguides via a fundamental matrix approach. , 1987, Applied optics.

[12]  A. Kersey,et al.  Multiplexed fiber Bragg grating strain-sensor system with a fiber Fabry - Perot wavelength filter. , 1993, Optics letters.

[13]  A.P. Zhang,et al.  Sandwiched long-period gratings for simultaneous measurement of refractive index and temperature , 2005, IEEE Photonics Technology Letters.