[en] This work was performed by Taisei Kiso Sekkei Co., Ltd. under contract with Japan Atomic Energy Agency. The objective of this work is development of multiple stage optical fiber displacement sensors for the deformation monitoring of shafts and horizontal tunnels at the Phase 2 of 'Geoscientific Research,' In last Japanese fiscal year, the feasibility study was done for developing the multiple stage optical fiber displacement sensors of ten stages or more for the boreholes of which diameter are 66 mm. Based on the result of this feasibility study, two types of prototype for field measurement were developed and evaluated by laboratory tests. These prototypes were modified and field test equipments which were consisted of 4 pieces of shallow part sensors and 2 pieces of deep part sensors were developed. The field test was done for installation to the borehole drilling in bedrock and a continuous observation of one month was performed, obtained results were summarized and the problems were picked up and arranged. (author)