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Helical Long-Period Gratings Inscribed in Polarization-Maintaining Fibers by CO2-Laser
摘要： We demonstrate fabrication of helical long-period gratings (HLPGs) in a polarization-maintaining fiber using CO2-laser. The maximum polarization dependent loss (PDL) of the grating was measured to be more than 30 dB at the resonance wavelength. The HLPG was found to have a high index sensitivity of -7248.6 nm/RIU when the surrounding refractive index changes in the range of 1.4470-1.4600, temperature sensitivity of 158.8 pm/°C, and strain sensitivity of 3.17 pm/με. The twist sensitivities based on intensity variation were measured to be 5.98 dB/ (rad/m) (co-directional twist) and -5.97 dB/ (rad/m) (contra-directional twist), respectively. The demonstrated grating devices have promising applications as high-sensitivity fiber sensors, PDL compensator etc.
关键词： optical fiber sensors,Fiber gratings,polarization-maintaining fibers,helical long-period gratings
更新于2025-11-28 14:24:03
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Theoretical analysis for exploring the optical performance of solid-core polymer based microstructured optical fibers
摘要： Polymer based microstructured optical fibers (MPOFs) like their silica counterparts guides the light through the use of array of wavelength-scale microstructures in the cross-section, and offers pivotal dominance over both polymer optical fibers (POFs) as well as air/silica microstructured optical fibers (MOFs). We aspire to investigate the optical characteristics of the solid-core MOFs based on polymer material by using an efficient theoretical model. Theoretical evidences to demonstrate that fiber support only single mode are explored and cut-off conditions are identified. We evaluate the effective index of higher-order mode (HOM) for the solid-core MPOF at terahertz (THz) regime, and the coupling properties of long-period gratings (LPGs) in MPOF are also examined. Further, the sensitivity coefficient is studied for realizing the efficient coupling in the evanescent field based applications. Theoretical results are compared with those as reported in the literature. Relative errors are also included.
关键词： Microstructured optical fibers,Single-mode,Long-period gratings,Polymer optical fibers,Second-order mode,Terahertz
更新于2025-09-19 17:13:59
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - CO <sub/>2</sub> -laser written helical long-period gratings with resonance at second-order diffraction
摘要： We demonstrate the fabrication of helical long-period gratings (HLPGs) with resonance at second-order diffraction for the first time. The torsion, temperature and bending sensing characteristics are investigated experimentally.
关键词： helical long-period gratings,fiber sensing,second-order diffraction
更新于2025-09-16 10:30:52
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Sensing characteristics of long period grating by writing directly in SMF-28 based on 800?nm femtosecond laser pulses
摘要： A long period grating is fabricated in standard SMF-28 ?bers without hydrogen loading by adopting point-by-point direct writing based on femtosecond laser pulses with 800 nm wavelength and 100 fs pulse width. Its sensing characteristics is investigated and the sensing sensitivities to temperature, external refractive index (RI) and strain are systematically examined as well. The experimental results show that the sensing sensitivity of the long period grating to temperature, RI and strain is about 124 pm/°C with a linearity of 0.989 within temperature ranging from 20 °C to 800 °C, ?582.5 nm/RIU (refractive index unit) with a linearity of 0.998 in the RI ranging from 1.342 to 1.380, and ?9.45 × 10-4 dB/με with a linearity of 0.98 in the strain ranging from 0 to 2925 με, respectively. The high sensitivity of prepared LPG will have potential application values in sensing measurement of multi-parameters and in the ?eld of high temperature and harsh environments detection.
关键词： Refractive index (RI),Long Period Gratings (LPGs),Femtosecond laser,Strain sensing,Temperature sensitivity
更新于2025-09-12 10:27:22
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Applications of Optical Fibers for Sensing || Optical Fibre Long-Period Grating Sensors Operating at and around the Phase Matching Turning Point
摘要： Optical fibres have been exploited as sensors for many years and they provide a versatile platform with a small form factor. Long-period gratings (LPGs) operating at and around the phase matching turning point (PMTP) possess some of the highest sensitivities to external perturbations in the family of LPG-based sensor devices. This type of optical fibre grating has been demonstrated as a sensor for use in a wide range of applications. In this review chapter, an overview of PMTP LPGs is presented and the key developments, findings and applications are highlighted. The fabrication considerations and sensor limitations are also discussed.
关键词： long-period gratings,turn around point,fibre optics,optical fibre,fibre sensors,phase matching turning point
更新于2025-09-11 14:15:04
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Comparative Investigation of Gamma Radiation Effects on Long Period Gratings and Optical Power in Different Optical Fibers
摘要： This work presents a comparative study regarding the effects of gamma radiation on standard and different radiation hardened optical fibers, by means of arc-induced long period gratings (LPGs) written in these fibers. In particular, the resonance wavelength shift (Δλres) of LPG attenuation bands and the attenuation in the fiber transmitted optical power (ΔP) have been comparatively explored during irradiation. Different responses were observed depending on the fiber model. The Ge-doped fiber exhibits significant changes of both resonance wavelength and optical transmission loss, whereas the pure silica core fiber is mostly insensitive to radiation (Δλres and ΔP keep almost close to zero). Surprisingly, the radiation resistant fiber, with doped core, exhibits significant resonance shift even if with trivial power losses. In addition, by combining these results with numerical modeling of LPGs, we were able to estimate the radiation effects on the optical fibers under investigation, in terms of average refractive index change. These results can be useful for the application of such devices in radiation environments, i.e., for the development of both radiation sensitive and radiation hardened sensors.
关键词： optical fiber sensors,Gamma-ray effects,Gamma-ray detectors,optical fiber applications,Dosimetry,long period gratings
更新于2025-09-11 14:15:04
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Ultrasensitive long-period gratings sensor works near dispersion turning point and mode transition region by optimally designing a photonic crystal fiber
摘要： A novel and ultrasensitive long-period gratings (LPGs) sensor based on photonic crystal fiber (PCF) has been proposed and theoretically investigated. The surrounding refractive index (SRI) sensitivity can be improved enormously by optimizing structure parameters of PCF to ensure LPGs work near dispersion turning point (DTP). Based on this, mode transition (MT) has been also designed and realized in LPGs based on PCF for the first time to further explore the theoretical limit of sensitivity. The simulation results illustrated that the optimized SRI sensitivity is 67,600 nm/RIU in low RI measurement region (1.334–1.344), which is much higher than that of other reported LPGs sensor based on PCF in previous literatures. The competitive advantages make the proposed sensor has a great application prospect in biosensing field, such as biomolecules detection and label-free immune sensing.
关键词： Long period gratings,Mode transition,Photonic crystal fiber,Dispersion turning point
更新于2025-09-09 09:28:46