In this paper, a bidirectional high-speed chaotic optical communication scheme with physical layer encryption is proposed and studied theoretically. The external cavity optical feedback method is analyzed, an erbium-doped fiber amplifier (EDFA) is used to represent the all-optical delay feedback loop of the traditional external cavity, which can overcome the shortcomings of the traditional method such as lower precision and large equipment volume. And the bidirectional communication scheme is discussed, which just sets the encryption device at the transmitter, uses the correlation between the two encryption signals to decrypt, and cancels the decryption device at the receiver, which not only simplifies the experimental equipment, but also solves the problem that the receiver can’t decrypt synchronously due to the channel damage in remote communication, and is easy to be applied in production and life. Finally, the simulation results show that the bit error rate is less than 10− 5, the bidirectional transmission of 10Gb/s information over 85km single-mode fiber is successfully realized.