We demonstrate a simple and robust method to write a phase-shifted helical long-period fiber grating (HLPG), where an equivalent phase-shift is formed by changing the local period of the grating during the fabrication process. Furthermore, we propose and demonstrate a simple method to characterize the phase-shift formed in a HLPG, which is realized by directly analyzing the imaging pattern of the fabricated HLPG using a stereo microscope under a white light illumination. Unlike the previous methods which are indirectly realized either by measuring the transmission spectrum of the fabricated HLPG or by analyzing the differential interference contrast (DIC) microscopic images of the fabricated HLPG, the proposed method can be used to well estimate the grating period as well as the phase-shift inserted in the HLPG in situ, which could considerably facilitate the fabrication technique of the HLPG by using CO laser.
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| http://dx.doi.org/10.1364/OE.25.007402 | DOI Listing |
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Article Synopsis
- - The study presents a novel all-fiber mode converter that can generate various high-order core modes by inscribing a helical long-period grating in a few-mode fiber using a femtosecond laser.
- - By adjusting the pitch of the grating during the laser inscription process, the researchers successfully convert different LP modes, including multiple high-order modes.
- - The technique allows for the simultaneous generation of first to fourth-order orbital angular momentum modes, providing a new method for creating integrated and efficient mode converters useful for advanced optical applications.
Fabrication of High-Sensitivity Optical Fiber Sensor by an Improved Arc-Discharge Heating System.
Sensors (Basel)
March 2023
Photonics Research Center, School of Optoelectronic Engineering, Guilin University of Electronic Technology, Guilin 541004, China.
We proposed a high-sensitivity optical fiber sensor based on a dual-resonance helical long-period fiber grating (HLPG). The grating is fabricated in a single-mode fiber (SMF) by using an improved arc-discharge heating system. The transmission spectra and the dual-resonance characteristics of the SMF-HLPG near the dispersion turning point (DTP) were studied through simulation.
View Article and Find Full Text PDFIn this study, a broadband flat-top second-order orbital angular momentum mode (OAM) converter is proposed and demonstrated using a phase-modulated second-order helical long-period fiber grating (HLPG). The proposed HLPG is designed to be inscribed in a thinned four-mode fiber and operated at wavelengths near the dispersion turning point (DTP). In contrast to most of the HLPG-based OAM mode generators reported to date, where the high-order OAM mode and flat-top broadband have rarely been achieved simultaneously, a second-order OAM(OAM-2) mode converter with a flat-top bandwidth of 113 nm @ -20 dB (ranging from 1530-1643 nm) and a depth fluctuation of less than 3 dB @-26 dB has been successfully demonstrated in this study, such flat-top bandwidth covers the entire C + L bands and represents the best result of the HLPGs reported to date.
View Article and Find Full Text PDFWe demonstrated the fabrication of bandwidth tunable ultra-broadband mode converters based on CO-laser inscribed long-period fiber gratings (LPFGs) and helical long-period gratings (HLPGs) in a two-mode fiber (TMF). The simulation and experimental results show that there is a dual-resonance coupling from LP to LP core mode at the dispersion turning point. The mode converters based on the TMF-LPFG and TMF-HLPG provide a 10-dB bandwidth of ∼300 nm and ∼297 nm, respectively, which covers O + E+S + C band.
View Article and Find Full Text PDFThe helical long-period gratings (HLPGs) with resonance at high diffraction order are fabricated in single-mode fiber using a laser. A series of HLPGs with different pitches are fabricated, and the phase-matching curves of the HLPGs with first and second diffraction orders are presented based on the experimental results. The temperature, surrounding refractive index (SRI), and torsion-sensing characteristics of the HLPGs with different diffraction orders have been investigated experimentally.
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