  Addressing the temperature and strain induced cross-talks simultaneously, we
propose an inherently strain and temperature insensitive fiber-optic
bio-sensor. The insensitivity has been achieved by properly adjusting the
dopants and their concentrations in the optical fiber core region, and by
optimizing the grating period and the strength of concatenated dual-resonance
long-period-gratings. The simulations have been carried out using the same
fiber parameters as used in our earlier experimental studies, which matched
excellently with the experimental results. The proposed sensor has a
theoretical refractive-index sensitivity of 4607 nm/RIU, which can be used to
detect changes as small as 2.2 x10^-7 in ambient refractive indices using a
detection system with spectral resolution of 1 pm. Our work finds application
in developing precision biosensors with inherent insensitivity towards
temperature and axial strain fluctuations. The sensor is currently under
fabrication at our lab.
