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We have demonstrated an all-fiber erbium laser incorporating a few-mode fiber long-period grating passively Q-switched by carbon nanotube for cylindrical vector beam generation. The laser can output both radially and azimuthally polarized beams.
A helical long-period grating (HLPG) was written in a polarization maintaining fiber (PMF) with CO2 laser. The twist characteristics of individual and cascaded PMF-HLPG were investigated experimentally. It was found that PMF-HLPG behaved differently with a different light input. When a polarized light was launched into the cascaded PMF-HLPGs with opposite helical direction, a high twist sensitivity...
We demonstrate the fabrication of long-period fiber gratings written in six-mode fiber by CO2-laser pulses as a mode converter to realize the mode conversion from LP01 mode to LP11 mode, LP21 mode and LP02 mode successfully with efficiencies of more than 90%, respectively.
We propose a novel mode converter (MC) based on multimode interference (MMI). This MC taking advantages of long-period fiber grating and multimode interference, it not only has high conversion efficiency, but also greatly reduces the interference between modes.
We propose the fabrication of double-helix chiral long-period fiber grating by twisting polarization-maintain fiber when the fiber is heated by CO2 laser irradiation. Different with conventional long-period fiber grating, the chiral grating is found to be insensitive to the fiber bending due to its helical waveguide structure.
A few-mode (FM) Er-doped fiber is fabricated using MCVD in combination with liquid solution method. Its absorption and gain spectra are tested. The experiment results show that On-Off gain of FM Er-doped fiber is about 30 dB/m, and can be used to study the amplification of different modes beam and Orbital Angular Momentum. It can be used in the long distance transmission system.
We demonstrate a fiber specklegram sensor based on the twist-induced effect in tilted two-mode fiber Bragg gratings (TM-FBGs). The measured LP21 mode specklegram rotates 4.73 (radm−1) with twist in the tilted TM-FBGs.
We demonstrated fabrication of a long-period fiber grating (LPFG) in B-Ge co-doped single-mode fiber near the turning point, which coupled light from fundamental mode to high diffraction order cladding mode, and high refractive index sensitivities up to 853 nm/RIU in 1.337–1.427 and 3970.3 nm/RIU in 1.427–1.451 were achieved.
We demonstrate a novel all-fiber mode converter based on an axial long-period fiber grating which was inscribed in two-mode fiber using a femtosecond laser. The OAM±1,1 modes can be effectively generated using this mode converter.
A compact optical fiber reflective index sensor is proposed and experimentally demonstrated. It is based on the tilted fiber Bragg grating (TFBG) inscribed in the thin-core fiber that is downstream spliced to the conventional single mode fiber (SMF). Thanks to the core dismatch between the SMF and the thin-core fiber, more cladding modes can be recoupled back into the SMF .The sensor can be used to...
We demonstrated the fabrication of the chiral long-period grating (CLPG) with the helical structures by twisting conventional single-mode fibre while the fibre was exposed unilaterally by CO2 laser. The bending and surrounding refractive index characteristics of the fabricated CLPG were investigated experimentally. Experimental results show that the CLPG has high bending sensitivity of 19.336 nm/m...
A new type of interlaced tilted phase-shifted long period grating (IPLPG) has been fabricated using focused CO2 laser. For the axial strain and temperature, the two resonance dips produced by phase-shift have different features. They have obvious differences for axial strain which are −5.0522×10−4 nm/µε and -7.9767×10−4 nm/µε from 340µε to 3060µε.
We demonstrated the fabrication of the helical long-period grating (HLPG) in conventional single-mode fiber (SMF) by CO2 laser. The surrounding refractive index and bending characteristics of the fabricated HLPG were investigated. Experiment shows that the fabricated grating has high refractive index sensitivity of −2321.67 nm/RIU. The resonance wavelength shifted to shorter wavelength linearly and...
Based on the finite difference beam propagation method (FD-BPM), we analysed the transmission spectra of tilted long period fiber gratings (TLPFGs) in detail. The new resonance dips corresponding to the LP1,m cladding modes appear at the right side of the resonance dips corresponding to the LP0,m cladding modes. While the tilted angle is equals to ∼ 86°, the coupling efficiency of new resonance dips...
We demonstrate the fabrication of thermal regenerated fiber Bragg gratings written in the hydrogen-loaded single-mode fiber by 193 nm excimer laser. The regenerated grating is found to have higher sustainable temperature up to 900°C. The characteristics of the gratings written in three kinds of photosensitive fibers are compared experimentally.
We demonstrate experimentally the fabrication of the long-period fiber gratings in the twisted polarization-maintaining fiber using CO2 laser. Thanks to the asymmetric and helical index modulation along the fiber, the unique index and bending characteristics of the twisted gratings can be achieved, which could be useful for practical sensing applications.
We demonstrated the fabrication of long period fiber gratings written in two-mode fiber as mode converter to realize the mode conversion between LP01 mode and LP11 mode with an efficiency of up to 99.9%.
A novel class of tilt long-period fiber gratings (TLPFGs) coated with nano-scale gold film is introduced, which is at period of 368pm and easy to fabricate. Gold film at nano-scale has been deposited on TLPGs by adopting evaporation technique in Vacuum Film-Sputtering Machine. The experiment results demonstrate that the refractive index sensitivity measured by resonant wavelength shift is raised in...
We demonstrate the fabrication of long-period fiber gratings (LPFGs) written by CO2 laser in different micro-structure specialty fibers. The characteristics of grating growth were studied by using the dynamic analysis of laser writing process. It can be believed that the residual stress relaxation, glass structure changes, and frozen of the non-uniformed external stress account for the formation of...
A fiber optic liquid level sensor based on the strain sensing by a fiber Bragg grating (FBG) is proposed and demonstrated. The FBG packaged on a thin cantilever beam so that the elongation and contraction of the FBG indicate a liquid level change. The strain response of FBG has been carried out and the shift in the Bragg wavelength shows a very good linearity during rise and fall of liquid level....
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