Abstract：The monitoring of the stress distribution along prestressed anchorage cables is one of the unsettled issues for prestressed reinforcement in geotechnical engineering. As a novel optical fiber sensing technique，BOTDR (Brillouin optical time domain reflectometer) can be used to measure the distributed strain along an optical fiber bonded to the support structure. Therefore，it is of great theoretical significance and practical value to study how to apply this technique to the monitoring of the stress distribution for the prestressed anchorage cables. A tensile test is carried out for one steel and three AFRP (aramid fiber reinforced plastic) prestressed anchorage cables while the strain distributions of the cables are monitored simultaneously with a sample resolution of 5 cm. The experimental results show that the distributed fiber optic sensing holds a rather high accuracy，with a relative error of the measurement results of no more than 3.8% between the fiber optic sensor and the strain gauge. The instantaneous prestressing loss of steel prestressed anchorage cable is 8.8%，while the instantaneous prestressing loss of AFRP prestressed anchorage cables were under 6.08%. After 30 days，the total prestressing loss of steel prestressed anchorage cable was 11.1%，while the total prestressing loss of AFRP prestressed anchorage cables were under 10.3%. Thus，the conclusion can be drawn herein that BOTDR distributed fiber optic sensing shows considerable applicability in monitoring the stress (strain) state of prestressed anchorage cable in geotechnical engineering.
