We present a novel co-axial dual core LMA fiber based high sen-
sitivity refractive index sensor. We have investigated the perfor-
mance of the sensor with respect to the design parameters.
Proposed sensor is highly sensitive in the range 1.44375–1.44382
where the transmittance of the fiber varies from 90% to 25%. We
expect that the structure would have ample potential in chemical
sensor applications.