Analysis of the response of long period fiber gratings to external index of refraction

• Published in: Journal of lightwave technology Vol. 16; no. 9; pp. 1606 - 1612
• Main Authors: Patrick, H.J., Kersey, A.D., Bucholtz, F.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.09.1998; Institute of Electrical and Electronics Engineers
• Subjects: Applied sciences; Attenuation; Chemical sensors; Circuit properties; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Fiber gratings; Glass; Integrated optics. Optical fibers and wave guides; Laboratories; Optical and optoelectronic circuits; Optical attenuators; Optical coupling; Optical fiber filters; Optical fiber sensors; Optical fibers; Fiber; Refraction index; Chemical sensor; Experimental study; Grating in fiber; Wavelength; Optical fiber
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/50.712243

This paper demonstrates that the change in wavelength of a long period fiber grating attenuation band with changes in external index of refraction can be enhanced by proper selection of the grating period. We calculate and experimentally verify that the wavelength shift caused by changing the external index from n=1 to n=1.44 of the attenuation band which appears in the 1400-1600 nm region in a 200-/spl mu/m period grating is four times that in a 350-/spl mu/m period grating. Changes in the spectrum over a wavelength range from 1100 to 1600 nm and 1<n<1.72 index range are also presented, and implications for grating design when enhanced or reduced index sensitivity is desired are discussed. Finally, we demonstrate the use of a highly index-sensitive long period fiber grating as a chemical concentration sensor.