## 1 Introduction  
In the field of communication, for several decades recently, the wavelength division multiplexing (WDM) technique has been widely applied in optical transmission systems for both high-speed backbone and access systems, up to 400 Gbps per wavelength, aiming to utilize the huge bandwidth of optical fiber [1, 2, 3, 4] in order to respond to the huge requirement of broadband services, e.g., broadband mobile access service, data mining, cloud computing, augmented reality, and virtual reality experiments. To enhance the capacity of communication channels, we can combine the WDM technique with several different methods, such as spatial division multiplexing [5], multi-carrier [6], super-channel [7], advanced multilevel modulation format [8], etc. This is due to the linear independence of such mentioned formats from the wavelength. Lots of optical fiber WDM communication systems use advanced modulation schemes such as quadrature amplitude modulation (QAM) [9; 10] or phase shift keying (PSK) [11] techniques in combination with a dual polarization scheme to increase the significant spectral efficiency by mean of maximization of wavelength bandwidth. For example, if an optical fiber transmission migrates from the mono polarization-QPSK format to the dual polarization-QPSK format, the capacity of the channel will double, while the bit error rate of the optical link will be negligibly affected [11]. In high-security communication systems, such as military communication, banking communication, and government communication systems [12], advanced and complicated encryption systems have been used to encode communication bit streams, such as FPGA-based hardware [13], RSA [14; 15], DES [16], alternatively interleaved AES [16; 17; 18], etc. However, these methods have some drawbacks, such as: (i) requiring complex electronic circuits for encoding and decoding, which are costly; (ii) increasing information processing delays; and (iii) being vulnerable to brute-force algorithms due to the development of computer-supported algorithms [19; 20]. Therefore, an economical approach increasingly used in physical layer security is the use of chaotic techniques [21; 22; 23] due to the superior characteristics of chaotic features, such as random pseudo-noise and spread spectrum [24]. On the other hand, chaos is also a deterministic phenomenon, so data can be decrypted if the synchronization process can be controlled. Information data are mixed with chaotic sequences through mechanisms such as scrambling, modulation, and encryption in order to enhance security so that eavesdroppers cannot successfully detect the encrypted information [17; 25; 26]. Nowadays, the chaos phenomenon is applied in various applications, such as wireless and radio communication [27], free-space optical communication [25], short-range chaotic optical communication [28; 29], visible light communication (VLC) [30; 31], underwater communication [32; 33; 34], automatic control [35], sensors [36], etc. Some related works have proposed utilizing the chaos effect arising from the dynamic properties of semiconductor laser systems for high-intensity applications in intensity-modulated direct detection (IM-DD) systems. However, generating chaotic laser beams with significant amplitude variations for WDM IM-DD systems remains challenging [37; 38]. In addition, chaotic techniques have not been widely applied in fiber optic communication systems due to the lack of research on the chaos phenomenon in wideband optical fiber communication systems, such as WDM systems. One of the most significant technological advancements in recent years is artificial intelligence (AI). In particular, deep learning (DL) models [39] have brought new dimensions to many fields, such as human-machine interaction [40], robotics [41], natural language processing [42; 43], etc. Recently, deep learning models have been applied in the field of information by effectively representing them through deep autoencoders for optical information signals to reduce nonlinearity and nonlinear balance.