Abstract
We propose a novel tilted long period fiber grating (TLPFG) design, inscribed using a line-by-line inscription technique and an infrared femtosecond (Fs) laser. The responses of this TLPFG to external refractive index, temperature, torsion, and strain were systematically investigated to determine its sensing characteristics. The external refractive index (RI) was measured to be −602.86 nm/RIU at an RI of ~1.432. The TLPFG was used to accurately measure temperatures up to 450 °C with a sensitivity of 103.8 pm/°C. The torsion and strain sensitivity of the device were 48.94 nm/(rad/mm) and −0.63 pm/µε, respectively. These results demonstrate that the proposed TLPFG could be used as sensors in a series of application fields including high temperatures and external environments.
Highlights
Optical fiber sensors have been widely used in a variety of fields due to several inherent advantages
We report on a tilted long period fiber grating (TLPFG) fabricated using an infrared
As the TLPFG was cooled down to room temperature, its transmission wavelength with pattern of LP05 shows a relatively high temperature response sensitivity, as high as spectrum was gradually restored but the resonance dip remained in a deteriorated state, due to the
Summary
Optical fiber sensors have been widely used in a variety of fields due to several inherent advantages. Pretreated high-pressure hydrogen loading processes are required to enhance the grating writing efficiency To solve this problem, Kondo et al firstly fabricated an LPFG in a single mode fiber (SMF) using an 800 nm Fs laser and the point-by-point method without hydrogen loading [14]. In 2008, Allsop et al successfully inscribed a series of symmetric and asymmetric LPFGs in photonic crystal fibers (PCFs) by a low-repetition femtosecond laser system with the point-by-point method [16]. The resulting grating transmission spectral shape was complex and included several smaller peaks This can be attributed to regularity of simultaneous refractive index modulation in the fiber core and cladding. Fs laser and a line-by-line inscription method This technique has several advantages, including fabrication flexibility, high machining efficiency, and repeatability. The measured twisting and strain sensitivities were 48.94 nm/(rad/mm) and −0.63 pm/με, respectively
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