Temperature insensitive strain sensor based on long period fiber grating pair in photonic crystal fibers

Abstract

We report temperature insensitive strain sensor based on long period fiber grating pair by partially tapering a photonic crystal fiber under CO 2 laser irradiation and experimantally investigated its novel mechanical chracteristics and thermal properies for optical sensing.

Review of long period fiber gratings written by CO2 laser

“…89 Moreover, a LPFG pair has been successfully created in a pure-silica PCF with a CO 2 laser to develop a stain sensor. 90 A novel coupled local-mode theory could be used to model and analyze this type of PCF-based LPFGs with periodic collapses of air holes. 91 Such a theory is based on calculating the variations in local-mode profiles and propagation constants over the perturbed regions and on solving the coupled local-mode equations to obtain a quantitative description of the intermodal energy exchange.…”

“…Another strain sensor based on a CO 2 -laser-induced LPFG pair in a PCF exhibits a high stain sensitivity of about −3 pm/ and a low temperature sensitivity of about 4.6 pm/°C. 90 Theoretical analysis reveals that a simple, low cost LPG sensor with approximately zero temperature sensitivity but large strain sensitivity could be realized by selecting an appropriate grating period. 137 Moreover, temperature-independent strain sensors were demonstrated by measuring the separation change between the two spit peaks of LPFGs written in the twisted optical fibers with a CO 2 laser and exhibited a high strain sensitivity of about 106.7 pm/ .…”

Long period fiber gratings written in photonic crystal fibers by use of CO2 laser

“…Such a strain sensor could effectively reduce the cross-sensitivity between the strain and temperature, and the temperature-induced strain error obtained was only 0.5 µε/℃ without temperature compensation. Another strain sensor based on a CO 2 -laser-induced LPFG pair in a PCF exhibited a high stain sensitivity of about -3 pm/µε and a low temperature sensitivity of about 4.6 pm/℃ [45]. Theoretical analysis reveals that a simple, low-cost LPG sensor with approximately zero temperature sensitivity but large strain sensitivity could be realized by selecting an appropriate grating period [46].…”

Ultrashort Long-Period Fiber Grating Sensors Inscribed on a Single Mode Fiber Using CO2 Laser Radiation

“…LPFGs have been developed and improved for decades, which resulted in numerous fabrication techniques and in a set of different sensor types, from simple LPFGs to interferometric systems, plasmonic resonance based sensing, and special fibers like photonic crystals [2][3][4][5]. There are many fabrication techniques inducing a permanent change on the refractive index: laser-based inscription systems such as UV [6], femtosecond pulses [7], and CO 2 laser nearinfrared radiation [8], or physically deforming the fiber using other methods such as electric arc discharges [9][10][11], ion implantation [12], or microbends [13].…”