Brightness profile data having a number of dimensions is extracted based on image data in a radial direction of an optical fiber, the brightness profile data representing features for each rotation angle of the optical fiber. Machine learning uses training data to create a prediction model that based on the brightness profile data determines a rotation angle of each pair of optical fibers is. The pair of optical fibers are rotated to the determined rotation angle and then fusion spliced. The training data indicates a correspondence relationship between the rotation angle of the optical fiber and brightness profile in the radial direction for each rotation angle of the optical fiber. The prediction model can determine a rotation angle of an arbitrary optical fiber based on brightness profile data of the arbitrary optical fiber.
Fusion splicing system, fusion splicer and method of determining rotation angle of optical fiber