High-Efficiency Inscription of Fiber Bragg Grating Array with High-Energy Nanosecond-Pulsed Laser Talbot Interferometer.

Zhe Zhang,Weijia Bao,Baijie Xu,Maoxiang Hou,Yiping Wang,Jun He

doi:10.3390/s20154307

Zhe Zhang, Weijia Bao + Show 4 more

Open Access

https://doi.org/10.3390/s20154307

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Abstract

A high-energy nanosecond-pulsed ultraviolet (UV) laser Talbot interferometer for high-efficiency, mass production of fiber Bragg grating (FBG) array was experimentally demonstrated. High-quality FBG arrays were successfully inscribed in both H2-free and H2-loaded standard single-mode fibers (SMFs) with high inscription efficiency and excellent reproducibility. Compared with the femtosecond pulse that had a coherent length of several tens of micrometers, a longer coherent length (~10 mm) of the employed laser rendered a wider FBG wavelength versatility over 700 nm band (1200–1900 nm) without the need for optical path difference (OPD) compensation. Dense FBG array with center wavelength separation of ~0.4 nm was achieved and more than 1750 FBGs with separated center wavelength could be inscribed in a single H2-free or H2-loaded SMF in theory, which is promising for mass production of FBG arrays in industry. Moreover, precise focusing of laser beam was superfluous for the proposed system due to the high energy density of pulse. The proposed FBG inscription system was promising for industrialization production of dense FBG arrays.

Highlights

Over decades, tremendous progress has been made in fiber Bragg gratings (FBGs) due to its extensive applications in optical fiber lasers [1,2,3], optical fiber communications [4,5,6] and single-point [7,8,9] or quasi-distributed [10,11] optical fiber sensing fields
We report on a reliable laser Talbot interferometer FBG inscription system, which overcome the deficiency of continuous-wave UV-laser and femtosecond laser Talbot interferometer
The FBG inscription efficiency in H2 -free Ge-doped single-mode fibers (SMFs) was improved significantly with the proposed inscription system, which was promising for mass production of weak-reflection FBG array for quasi-distributed fiber-optic sensing applications

Summary

Introduction

Tremendous progress has been made in fiber Bragg gratings (FBGs) due to its extensive applications in optical fiber lasers [1,2,3], optical fiber communications [4,5,6] and single-point [7,8,9] or quasi-distributed [10,11] optical fiber sensing fields. In 2017, Gui et al [15] developed a dense weak-reflection FBG array with identical FBG central wavelength for high spatial resolution distributed sensing applications. They demonstrated a high spatial resolution over 6680 FBGs along a 10-m-long fiber. Tremendous methods have been developed for the inscription of FBG array with separated wavelength, such as femtosecond laser point-by-point [17], line-by-line [18] and laser Talbot interferometer methods [19]. 1750 FBGs with separated center wavelength can be inscribed in a single fiber Such properties of the proposed FBG inscription system make it a good candidate for mass production of FBG arrays for industry applications

Sensor Fabrication and Working Principle

Inscription of Various FBG Arrays

FBG Array Inscribed in H2 -Free SMFs

FBG in H

Reflection spectra evolution an FBG

Reflection spectrum ofFBG an FBG inscribed by proposed the proposed

Conclusions