Mode scrambler

Provided is a low-loss mode scrambler that allows for the steady-state mode distribution to be acquired within a short distance even when incident light is smaller than the numerical aperture of fibers to be measured and facilitates switching to the all-mode distribution state in a multi-mode fiber having a numerical aperture of 0.2 or more with a core diameter larger than tens of [mu]m. A singlefiber 2 is wound around and bundled on a plurality of bobbins 3a, 3b with a larger radius than the minimum bending radius of the fiber. A twisted portion 5 is formed by rotating the bobbins 3a, 3b andtwisting the fiber 2. Thereby, the output acquired from the light entering the fiber is in the steady-state mode. 本发明提供种低损失的搅模器，其在芯径超过数十μm且数值孔径在0.2以上的多模光纤中，即使在入射光比被测光纤的数值孔径更小的情况下，也能够以较短距离获得稳态模分布，且容易切换至全模分布。通过将根光纤(2)缠绕在半径比光纤的最小弯曲半径更大的多根绕线管(3a、3b)上而归拢，并使该绕线管(3a、3b)旋转，从而能够扭转光纤(2)而形成扭转部(5)，而从进入光纤(2)的入射光提取稳态模的输出。