High Sensitive Refractometric Sensor Using Symmetric Cladding Modes of an FBG Operating at Mode Transition

• Published in: Journal of lightwave technology Vol. 34; no. 14; pp. 3348 - 3353
• Main Authors: Bandyopadhyay, Sankhyabrata, Dey, Tanoy Kumar, Basumallick, Nandini, Biswas, Palas, Dasgupta, Kamal, Bandyopadhyay, Somnath
• Format: Journal Article
• Language: English
• Published: New York IEEE 15-07-2016; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Couplings; Fiber Bragg grating (FBG); Fiber gratings; fiber optic sensors; mode transition; Refractive index; refractive index (RI) sensing; Sensitivity; Sensors
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2016.2563521

We report a high sensitive refractive index (RI) sensor using fiber Bragg grating (FBG) where azimuthally symmetric resonant cladding modes were used for RI sensing. We enhanced the sensitivity by tailoring the effective index of a cladding mode to an optimum value so that the mode has maximum sensitivity around a specific surrounding RI. We tailored the effective index of a clad mode by controlled deposition of a thin polymer layer having RI higher than the cladding. Experiments show that the sensitivity of cladding mode (LP0,12) of a standard FBG with overlay coating to the surrounding medium having RI around 1.333 is ~ 2600 pm/RIU. The proposed sensing mechanism will be useful for biological sensing application.