Question

1) Why is it necessary to fabricate the two semi-half FBG sensors close together

2) Give ANY TWO reasons to justify the use of FBG Sensors for condition monitoring of the container wall.

Answer 1

1.two semi fbg fabricated close because reflected wave by 2nd sensor also changes its wavelength during propagating through 1st sensor because of changing is medium and changed reftractive index.if this reflected wave after propogation through 1st sensor then changes its wavelength enough to satisfy braggs conditions than it can also transmitted through the second sensor.

2.Fbg are like gratings because there refrective index changes...so at each point signals are reflected back.fbg permits transmission only to those waves which satisfy the brag conditions.