A novel technique for mitigating the polarization sensitivity between the uplink multiple access signals was proposed in the AM-CO-OFDMA PON uplink transmission. To pro- vide uplink multiple access on the orthogonal frequency division multiplexing (OFDM) based op- tical access network, the polarization difference between the uplink optical signals are unavoidable issue which degrades a transmission performance severly. By using symple digital signal process- ing with Pythagorean identity, we experimentally demonstrated stable transmission performance of various polarization states of uplink multiple access signals.