Fig. 1. Setup of the proof-of-concept experiment. ASE, amplified spontaneous emission; PPG, pulse pattern generator; SMF, single-mode fiber; EDFA, erbium-doped fiber amplifier; PD, photon detector; OF, optical filter; BER, bit error rate; DCF, dispersion compensation fiber; TX, transmitter; RX, receiver.

Fig. 2. Waveform and frequency of the signal.

Fig. 3. Experimental results of different positions. (a) The measured null frequency and (b) the error of the calculated position.

Fig. 4. BER curves of the covert channel with and without vibration.

Fig. 5. BER curves of the public channel under vibration.