In recent years, with the development of eavesdropping technology, how to improve the security of data transmission has become a hot research issue. In order to enhance the security of the secure communication system, a chaotic laser secure communication system with variable laser power is proposed in this paper. Based on the original optoelectronic feedback chaotic laser communication system, the change of laser power is regarded as a new key. The simulation results show that the error rate of the eavesdropper is above 10-2 over most of the laser power, and the average error bit rate of the eavesdropper is 7 orders of magnitude higher than the average error rate of the authorized receiver. In addition, the appropriate masking efficiency will reduce the bit error rate of the eavesdropper, while it has little effect on the eavesdropper. The system scheme can be used in communication with high confidentiality requirements in the future.
An innovative demodulation system for multilongitudinal mode fiber laser sensor has been proposed. By using a bandpass filter and a low-speed analog-to-digital converter (ADC), the high-frequency sensing signal can be downconverted and sampled simultaneously when the unaliasing condition is satisfied. Since the MLM fiber laser sensor could generate a wideband electrical signal after optical-to-electrical conversion, it is convenient to filter the signal to meet the unaliasing condition by a tunable bandpass filter while keeping the sample rate unchanged. Moreover, each tone of the beating frequency signal has the full information for demodulation of measurand. The demodulation system only needs a bandpass filter and a low-speed ADC which reduces the cost of the system and make the system more stable. A proof-of-concept experiment is conducted to verify the proposed scheme. Eventually by demodulating a beat frequency in 1.625GHz, a sensitivity of -5.87kHz/°C is achieved in a fiber laser sensing system with a sample rate of 500MHz.