In optical transmission technique using optical polarization, the change of state of polarization (SOP) and the rotation of SOP (RSOP) during optical transmission has a significant impact on the transmission performance. We propose polarized intensity rotational frequency shift keying (PIR-FSK) as a novel modulation technique in change of SOP and RSOP-tolerant optical transmissions. The proposed PIR-FSK signal does not affect the entire intensity of the optical carrier by modulating the

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... al signals on each X and Y-polarized optical carrier. Therefore, the proposed PIR-FSK modulation and optical carrier intensity modulation can operate at the same time. Moreover, since the proposed technique does not modulate the signal using the SOP unlike the PolSK, PIR-FSK is not affected by SOP changes that occur during transmission, and the signal does not be degraded even with RSOP. We demonstrated that the signals modulated using the proposed PIR-FSK modulation have higher signal capacity and efficiency compared to the signal modulated using PolSK modulation.