  An ultra-sensitive sensor based on long-period fiber graings (LPFGs) has been
fabricated for the detection of methanol and water content in ethanol. Our
sensor is very compact in size, highly accurate and easy to fabricate making it
very useful than the conventional surface plasmon resonance (SPR) sensor, which
is bulky and expensive. We show that our sensor is capable to achieve an ultra
sensitivity of 696.34 pm/ Volume-percent methanol and 655.3 pm/ Volume-percent
water in presence of methanol and water in ethanol respectively. Our sensor is
capable of detecting minimum 1.5 x 10^-3 Volume-percent methanol and water in
ethanol, which is far better than all the methods reported till now.
