Structural health monitoring has been used to confirm the durability evaluation and safety of a structure in which long-term use is required. Because the transmission loss of the optical fiber sensor is extremely small, it can measure the present status of structures from far away. Generally the FBG (Fiber Bragg Grating) optical sensing systems are often used to get reliable indices from structures. The shipping industry recently, there has been a growing interest in fuel efficiency improvements and energy regulation in international shipping. Therefore, during sailing, to measure the exact power of the main shaft of the ship has become important. We proposed the monitoring system using space optical transmitting of the FBG optical fiber to get information from a rotational shaft. And we evaluated the performance of the space optical transmission of the FBG optical fiber sensing system for rotational shaft in the previous study. Consequently, we reported that it can be effectively measured and space optical transmission metric is effective for performance prediction．In this paper, the strain and the temperature on the rotating torsion shaft, is measured by the FBG optical fiber sensor and the space optical transmission. We confirm reliability of the information that is retrieved from the rotating shaft subjected to torsion in the experiment. The conditions for reliable data from the rotating shaft under loading is obtained on the basis of the experimental results of the proposed systems.

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Structural health monitoring is intended as a mechanism to ensure the operation and to evaluate the durability of the structure whose use is expected during a long time. It reduces life-cycle costs with ensuring the safety and the reliability of the structural systems. In addition, the optical fiber sensing systems are used for structural health monitoring because the high accuracy measurement and the transmission line, can be combined by the optical fibers. On the other hand, accurate measurement of horsepower for a rotary shaft in ships is needed for higher fuel efficiency and the energy regulation in international shipping. The FBG (Fiber Bragg Grating) optical fibers sensing are applied to measure several strains at different location which are induced by the torsion for the rotary shaft rotating in 100-400 rpm. The measured data of the strains have to be transmitted to the outside of the rotary shaft to use the FBG optical fiber sensing. The optical space transmission system makes it possible to transmit the data of the strains on the surface of the rotary shaft to outside the measurement system. In this study, we propose to use FBG optical fiber sensor to the shaft horsepower meter of main rotary shaft in ship. The optical transmission efficiency of the FBG measurement system is studied by a static and rotational experiment. Based on the experimental results, we verify the effectiveness of the optical space transmission performance of the system, and of the metrics for its improving performance.