  The security of chaotic optical communication using time-frequency (TF)
representation is analyzed in this paper. The mean scalogram ratio (MSR) of TF
representation and peak sidelobe level of MSR are defined to detect message.
Algorithm for message detection and extraction is presented in detail. Two
typical message encryption schemes, chaos masking and chaos modulation, are
analyzed. The results reveal that it is not secure to transmit message when the
message frequency locates at low power on power spectrum portrait. The proposed
method is very useful for estimating the security level of message masking in
chaotic optical communication.
