Chaos Coding-Based QAM IQ-Encryption for Improved Security in OFDMA-PON

In this letter, we propose a quadrature amplitude modulation (QAM) encryption method based on chaos coding for security improvement in orthogonal frequency-division multiple access-based passive optical network (OFDMA-PON) systems. In the encrypted QAM symbols, the real ( \(I\) ) and imaginary ( \(Q\) ) parts are separately coded with key sequences, which are generated by a modified Logistic mapping. Iteration parameters of the mapping formula are set as the security keys, which are determined in each optical network unit (ONU) and then sent to optical line terminal (OLT). The key sequences for different ONUs are generated with their corresponding security keys. According to the subcarrier allocation information, downstream signal is encrypted in the OLT and then decrypted in each ONU with distinct key sequences. Encryption of 10-Gb/s 16QAM OFDM and 12.5-Gb/s 32QAM OFDM signals has been successfully implemented over 30-km standard single mode fiber in the security improved OFDMA-PON.