Due to the contacts and bus of the high voltage switch lies in high potential

it is difficult to detect their temperature directly. Combined with good characteristic of optical fiber

optical fiber temperature sensor is designed based on displace-intensity modulated

which has advantage with simple structure and system. The sensor’s mathematics model is provided. The result of experiment shows that this scheme is feasible

and suitable to be used under the conditions such as narrow space

strong electromagnetic field

combustible and explosible sites and so on.