S. Ebisawa and S. Komatsu: Message encoding and decoding using asynchronous chaotic laser diode transmitter-receiver array, Appl. Opt., Vol.46, No.20 (2007) 4386-4396.

We have numerically investigated a chaotic laser diode transmitter-receiver array scheme (CLDTRAS), which is a secure digital communication scheme using a difference between two types of transmitter-receiver array consisting of two self-pulsating laser diodes (LDs), i.e., a receiver LD and a transmitter LD. By analyzing the bit error rate, particularly its dependence on the parameter mismatches of the hardwareand channel noise and on the correlation coefficient between a transmitter LD and receiver LD, weexamined the problems of sensitivity to parameter mismatches and channel noise and a dependence onchaos synchronization between a transmitter LD and a receiver LD. The former makes communicationdifficult, and the latter makes it possible for an eavesdropper to estimate the receiver LD using chaossynchronization and to forge the hardware. Then we studied the effects of the bit error rate for variousvalues of the threshold, which determines a binary message, and for various numbers of transmitters-receivers making up a LD transmitter-receiver array. It has been shown that a highly noise-tolerant andhardware-dependent communication scheme can be achieved with the LD transmitter-receiver array,whose transmitter and receiver LDs are asynchronous with respect to each other, by choosing the properthreshold and increasing the number of LD transmitters-receivers. Since it is possible to communicatewithout chaos synchronization, it becomes difficult to forge hardware and to eavesdrop with the forgedhardware even if the key is stolen.