摘要
Performance of multicarrier code division multiple access (MC-CDMA) long reach passive optical network (LR-PON) implemented with colorless laser diode transmitter is evaluated and compared with the same system under typical orthogonal frequency division multiplexing (OFDM) format. The relative amount of the multicode interference (MCI) in the MC-CDMA PON can be efficiently suppressed by applying the minimum mean square error based MCI cancellation processing and be analyzed in term of the error vector magnitude deviation. Due to the double sideband nature of the directly modulated colorless laser diode, both OFDM and MC-CDMA formats suffer from severe power fading after fiber transmission. Partial subcarriers in the OFDM-PON fail to reach the specified forward error correction (FEC) threshold, causing a huge performance deviation among subcarriers and a 3% data loss after 75-km transmission. In contrast, a distance transparency transmitter design for subscribers ranging from back-to-back to 50 km is achieved in the MC-CDMA PON scheme, and the received performance among subcarriers are equalized under the FEC criterion even after 75-km transmission. Therefore, the MC-CDMA exhibits superior performance when comparing with the OFDM format in the directly modulated colorless laser diode based LR-PONs.