Long-gage fibre optic sensors are designed to measure an average strain between two points of the structure. The advantage of the sensors is in a magnitude of gage-length, usually ranged between 250 mm and 10 m, which makes them insensitive to local structural defects like crack or air pockets. The data collected by the sensors is not related to local material properties but rather to structural behaviour of monitored element. The philosophy of monitoring using long gage sensors is very similar to philosophy of finite element method: the structure is divided in elements, called cells, and each cell is equipped with a combination of sensors, called topology. The topology is particularly adapted to efforts expected in the cell, e.g. in case of pure traction or compression the topology consists of single sensor installed parallel to the axis of cell, while in case of bending the topology consists of two sensors parallel to each other and to the axis of the cell. Using appropriate algorithms, the behaviour of different cells is correlated and monitoring at global structural level is performed. Since single topology can cover important volume of the structure, the total number of cells is limited and the total number of sensors necessary for representative monitoring of whole structure is reasonably small. In addition, fibre optic nature of the sensors makes them insensitive to environmental influences such as temperature, humidity, corrosion, and electromagnetic fields. The aim of this paper is to present the application of long-gage fibre optic sensors to piles subject to axial compression, pullout and flexure, and to highlight their performances through the results. Large spectra of parameters such as the Young modulus of the piles, the occurrence and characterisation of cracks, the normal force distribution, the ultimate load capacity in case of axial compression and pullout tests as well as the curvature distribution, horizontal displacement, deformed shape and damage localization in case of the flexure tests. Moreover, the distribution of the pile-soil friction, the quality of soil and the pile tip force were estimated.