S. Ebisawa and S. Komatsu: Optimization of Chaotic Message Encoding and Decoding Using Laser Diode Transmitter/Receiver Array, Book of Abstracts, MOC'04 (10th Microopics Conference, Jena, Germany, 2004), p.55, F-41; Proc. MOC'04 (10th Microopics Conference, Jena, Germany, 2004), F_41.PDF.

We investigate the digital chaotic communication using the array of transmitter/receiver that consist of two self-pulsating LDs, i.e., a receiver LD and a transmitter LD. Part of the output of a transmitter LD is injected into the corresponding receiver LD that receives a chaotically encoded signal. A ND filter is placed after each transmitter LD to control the amount of light transmitted to and then injected into the corresponding receiver LD. According to the amount of the transmitter output which is injected into the receiver LD, two kinds of chaotic states with different Lyapunov exponent are induced in the receiver LD, and they are utilized to represent a binary digit. In addition, the distribution of the coupling factor between transmitter and receiver is used as a "key". Only the proper receiver who is precedently given the "key" is able to choose an appropriate threshold of the Lyapunov exponent calculated from the detected chaotic signal that is necessary to decipher each binary bit and to decode finally the whole message. In this study we numerically analyze the chaotic method for message encoding and decoding, and describe how to optimize the coupling factors of transmitter/receivers in the array in order to reduce the bit error rate.