Design and development of long-period grating sensors for temperature monitoring

Abstract

Long Period Gratings (LPGs) have been developed using carbon dioxide laser in a standard optical fibre. LPGs with a periodicity of 600 μm and grating length of 24 mm have been inscribed on standard single mode fibre. Such gratings have been used in designing temperature sensors and temperature is monitored up to 80 • C. The sensitivity of such type of sensor is 0·06 nm/ • C where as for standard Fibre Bragg Grating (FBG) it is 0·011 nm/ • C. The LPG performance is also evaluated after γ -ray irradiation for total dose of 5 KGy and has not shown any effect on transmission spectrum.

High Radiation Sensitivity of Chiral Long Period Gratings

“…1 Why did previous irradiation tests of LPGs [7], [21]- [23] show no distinct DWS? 2 Why are the DWSs of CLPGs about 100-1000 times higher than the BWSs observed with FBGs?…”

“…For a dose of 9.3 kGy they report a DWS of +0.15 nm, but with an error of 0.3 nm, i.e., the resolution of their measurements seemed to be relatively poor. In [23] a LPG written by a CO laser in a Corning SMF-28 fiber was irradiated up to a gamma dose of 5 kGy. The authors did not find "any effect on the transmission spectrum", whereas our CLPG made of a Corning SMF-28 fiber showed a DWS of nearly 3 nm at that dose.…”

“…The denominator N is an integer that can be (i.e., ) and gives the order of refraction. This factor is not considered in most LPG publications, e.g., [17], [23]. So far we are not able to calculate the dip wavelength from and the refractive index difference because i, N, as well as are not known at present, but extensive evaluations of all relevant grating parameters are in progress, e.g., [25].…”

“…In [21] and [22], no radiation-induced spectral changes up to a dose of 0.5 MGy were found in LPGs written by the arc discharge technique in pure silica core fibers. Chaubey et al [23] investigated LPGs written by a CO laser in a Corning SMF-28 fiber. No effect on the transmission spectrum was observed after a gamma dose of 5 kGy.…”

Optical Properties of Multi-Microgratings, Their Replication and Applications

“…Some novel designs such as thermally actuated interferometric sensors have been reported based on device fabricated with PDMS [71], long period grating fiber sensors with high temperature sensitivity [72,73] and designs with photonic crystals [74,75] and plasmonic nanostructures [76]. These novel designs are complicated to fabricate and may not be suitable for a simple, quick temperature measurement.…”