**Patricia Kara De Maeijer 1,\* , Geert Luyckx 2, Cedric Vuye <sup>1</sup> , Eli Voet 2, Wim Van den bergh 1, Steve Vanlanduit 3, Johan Braspenninckx 4, Nele Stevens <sup>4</sup> and Jurgen De Wolf <sup>5</sup>**


Received: 15 May 2019; Accepted: 14 June 2019; Published: 20 June 2019

**Abstract:** Pavement design is essentially and usually a structural long-term evaluation process which is needed to ensure that traffic loads are efficiently distributed at all levels of the total road structure. Furthermore, to get a complete analysis of its durability behavior, long-term monitoring should be facilitated, not only from the top by falling weight deflectometer (FWD) or core drilling but preferably from inside the structure and at exactly the same positions during a long-time interval. Considering that it is very hard to devise an efficient method to determine realistic in-situ mechanical properties of pavements, the determination of strain at the bottom of asphalt pavement layers through non-destructive tests is of a great interest. As it is known, fiber Bragg grating (FBG) sensors are the most promising candidates to effectively replace conventional strain gauges for a long-term monitoring application in a harsh environment. The main goals of this paper are to compile an overview of the recent developments worldwide in the application of fiber optics sensors (FOS) in asphalt pavement monitoring systems; to find out if those systems provide repeatable and suitable results for a long-term monitoring; if there are certain solutions to validate an inverse modelling approach based on the results of FWD and FOS.

**Keywords:** asphalt; fiber optics sensors (FOS); fiber Bragg grating (FBG) sensors; falling weight deflectometer (FWD)
