Strain-insensitive and high-temperature long-period gratings inscribed in photonic crystal fiber

Abstract

We demonstrate the strain-insensitive and high-temperature long-period gratings in photonic crystal fiber. Thermal dependency of resonance wavelength is I0.!9pdC at range from 24OC to 992*C, whereas coefficient of strain sensitivity is -0.192pdp up to 2.74%~.

Strain and temperature characterization of LPGs written by CO2 laser in pure silica LMA photonic crystal fibers

“…The spectral measurements over temperature were performed three times for each grating in order to improve statistical confidence. A comparison to data available in the literature showed that LPG-E presented, for instance, a similar temperature sensitivity (-19.6 pm/℃) as that found in LPGs written in pure silica PCF by CO 2 laser (-21.51 pm/ ℃ ) [28], but different from the sensitivity (-10.9 pm/℃) found by Zhu et al [32] for LPGs in photonic crystal fiber by the use of focused pulses of a CO 2 laser and a periodic stress relaxation technique without geometrical deformation and elongation of the fiber.…”

Long Period Gratings in New Generation Optical Fibers

“…Zhao et al, 2008). These structures written with CO 2 laser were proposed as straininsensitive high-temperature PCF sensors (Zhu et al, 2005). For high-temperature applications, LPGs written in PCF with the electric arc technique have also shown an adequate performance, as was reported in (Humbert et al 2004).…”

“…In this section a brief review of the main applications of LPGs in PCFs is presented. Concerning the temperature dependence of LPGs in IG-PCF, most of the papers report that temperature sensitivity is of the order of few picometers (up to 10) per degrees centigrade (Dobb et al, 2004;Petrovic et al, 2007;Zhu et al 2005;Humbert et al, 2004) while the sensitivity of gratings in SMF is reported to be in the range 30-200 pm/°C or more (James & Tatam, 2003;Rego et al 2005b). The shifts of LPG bands due to thermal changes is principally attributed to two factors such as the thermooptic effect and the thermal expansion of the fiber that force wavelength shifts of opposite signs (Petrovic et al, 2007).…”

Long-period gratings based on Photonics crystal fibers and applications

“…However, the single material property of PCFs leads to non-photosensitivity to UV light, therefore FBGs and LPGs cannot normally be formed in PCFs by use of the conventional UV-written technique, unless a PCF with a Ge-doped photosensitive core is used [26]. Recently, several alternative methods for making LPGs in PCFs with non-photosensitive cores were introduced, including glass structure change [27], periodic structural and/ or residual stress relaxation induced by arc discharge or a CO 2 laser [28][29][30][31][32], refractive index modulation by periodically applied mechanical pressure [33] or by the use of an acoustic wave [34,35], and periodic drilling micro-holes with a femto-second laser [36].…”

“…Here, we demonstrate the fabrication method by using a CO 2 laser, which has been used widely [30,32,37,38,40]. 7.827×10 -6 7.8×10 -6 7.75×10 -6 ξ cl = 7.85×10 -6 Fig .…”