In response to the challenges of insufficient sensitivity and low strain transfer efficiency of sensors for long-term strain monitoring in civil engineering

a buried fiber Bragg grating(FBG)strain sensor with a variable cross-section sensitivity-enhancing structure is proposed.By optimizing the elastic structure design and key parameters

and combining with integrated additive manufacturing process

the strain transfer efficiency and measurement consistency of the sensor are effectively improved.Experimental results indicate that the average linearity of the forward stroke is 0.58%

and the sensitivity is 4.78pm/με; the average linearity of the reverse stroke is 0.622%

and the sensitivity is 4.82pm/με.Furthermore

the repeatability of the three forward and reverse strokes is 0.58%

0.68%

and 0.71%

respectively;the overall repeatability is 1.18% for the forward stroke and 1.48% for the reverse stroke.The sensor demonstrates good linear characteristics and measurement stability.This paper provides a reliable solution with engineering application value for solving the technical diffculties of sensing in long-term strain monitoring of civil structures.