Dual-wavelength chaos generation and synchronization in erbium-doped fiber lasers

Dual-wavelength chaos is generated in one erbium-doped fiber laser. Tunable optical filters (TOF) are used to select the wavelengths. The generation of chaos is achieved by either modulating the pump laser diode near the relaxation oscillation frequency of the fiber laser or by introducing the modulation through an electrooptic modulator built into each wavelength branch. The receiver is fabricated with identical parameters as the transmitter except for an open loop structure. By tuning the TOF in the receiver, synchronization of chaos is observed in either of the two wavelengths. Thus, it can pave the way for wavelength-division-multiplexing chaos communications.

I. Introduction

Secure communications have been intensively studied in many areas such as electronic circuits, semiconductor lasers, and fiber lasers. Synchronized chaos was discovered by Pecora and Carroll in 1990 [1] in electronic circuits. Fig. 1. Experimental setup for dual-wavelength chaos generation in EDFRL. PD: Photodetector. Subsequently, chaos was also observed in various kinds of lasers such as Nd : YAG laser [2], laser [3], semiconductor laser [4], and erbium-doped fiber ring laser (EDFRL) [5]. There are numerous works on chaos communication based on EDFRLs [5]–[10]. Experiments of synchronization of chaos in EDFLs were reported, in an elliptical core EDFRL [6] and in standard single-mode EDFRL [7]. A sinusoidal signal at 1 GHz is demonstrated to be transmitted and recovered in a chaotic EDFRL system [8]. Encoded chaotic communication is realized for digital message at 250 Mb/s after transmission through 35-km single-mode fiber [9].