The Advantest Q8163 is a optical polarization scrambler which has a function to change the state of output light polarization with using a polarization element of optical fiber type. The state of output light polarization can be changed continuously by driving 3 polarization elements of optical fiber type. Therefore, all the states of polarized light (all the points on the Poincare sphere) can be output. As a polarization element of optical fiber type is used inside, the fluctuation of insertion loss are ±0.005 dB or less when the state of polarized light changes. Therefore t provides the efficiency in evaluating various optics of small PDL (Polarization Dependent Loss). By driving the polarization element of optical fiber type, the state of output light polarization can be changed at high speed. It is possible to measure polarization dependability of various light components at high speed.