We present a novel technique to generate an orthogonally polarized optical single sideband (OSSB) generated by a tunable bandpass filter (TBF).When the OSSB passes through the other polarization modulation (PolM) which is polarization dependent, the phase shift of the optical carrier and first-order sideband is different under different bias. As a result, a wideband tunable phase shifter is realized by adjusting the bias applied to the polarization modulator.