Long-period grating assisted Michelson interferometer has been proved to be a perspective device for chemical and biochemical sensing based on refractive index measurement. However, the phase difference between the fiber core propagation and the fiber cladding propagation in the in-fiber Michelson interferometer is correlated to the common path length. As a result, the fringe spacing in the reflection spectrum drops with the interferometer cavity length, leading to reduced fringe wave length shift in refractometry measurement. In this paper, we proposed a long-period grating assisted Michelson interferometer with the core mode and the cladding mode propagation separated. By eliminating the residue core mode after the long period grating coupling, an interferometer arm consists of cladding mode propagation is realized. With the cavity length of the other arm controllable, the fringe spacing in the reflection spectrum of the Michelson interferometer can be precisely controlled. The proposed Michelson interferometer allows use of long cavity length of the cladding mode arm to accumulate phase change and large fringe spacing for wavelength interrogation in refractometry sensing.

Date Published: 12 August 2008
PDF: 9 pages
Proc. SPIE 7099, Photonics North 2008, 70992A (12 August 2008); doi: 10.1117/12.807755

Published in SPIE Proceedings Vol. 7099:
Photonics North 2008
Réal Vallée; Michel Piché; Peter Mascher; Pavel Cheben; Daniel Côté; Sophie LaRochelle; Henry P. Schriemer; Jacques Albert; Tsuneyuki Ozaki, Editor(s)