Xiaonan Hu

Chaos-Based Partial Transmit Sequence Technique for Physical Layer Security in OFDM-PON

We propose and demonstrate a physical layer security scheme via chaotic partial transmit sequence (PTS) technique in orthogonal frequency-division multiplexing passive optical network (OFDM-PON). A 4-D hyper chaos is employed to generate the chaotic partition information, the chaotic phase weighing factors in PTS as well as the chaotic training sequence for OFDM symbol synchronization, which provides a huge key space to enhance the physical layer confidentiality. Transmission of 8.9-Gb/s 16 quadrature amplitude modulation encrypted OFDM signals is demonstrated over 20-km standard single-mode fiber, which shows reliable robustness against exhaustive attacks. Moreover, the proposed scheme improves the OFDM transmission performance due to the effective reduction of the peak-to-average power ratio of the OFDM signals by chaotic random PTS.

Gain-clamped erbium-doped fiber-ring lasing amplifier with low noise figure by using an interleaver

A novel all-optical gain-clamped erbium-doped fiber-ring lasing amplifier (GC-EDFRLA) has been demonstrated, in which the odd port of a 100/200-G interleaver was used to form a fiber-ring cavity to produce lasing oscillation for locking the gain and its even port was employed to export the amplified signals. In such a way, the problem existing in the conventional GC-EDFRLA is solved. The signal can be exported separately without the lasing power while the noise figure (NF) is very low. Finally, the GC-EDFRLA with a low NF of 4.2 dB was achieved.

Chaotic Encryption Algorithm Against Chosen-Plaintext Attacks in Optical OFDM Transmission

We propose and demonstrate a physical-layer encryption algorithm against chosen-plaintext attacks (CPAs) in optical orthogonal frequency-division multiplexing (OOFDM) transmission, where the cyphertexts are dynamically generated for the first time by incorporating the random feature of the input data. The multiple-fold encryption algorithm consists of chaotic subcarrier allocation scrambling in time/frequency domains, chaotic phase rotation of subcarriers, as well as chaotic training sequence, which creates a total huge key space of 10194 by using a 4-D hyperdigital chaos. The transmission of 8.9-Gb/s 16-QAM encrypted OOFDM data is demonstrated over 20-km standard single-mode fiber. The proposed encryption scheme provides excellent confidentiality of OOFDM transmission against the brute-force attacks and CPAs.

Chaotic signal scrambling for physical layer security in OFDM-PON

We propose and demonstrate physical layer security schemes via implementation of chaotic signal scrambling such as partial transmit sequence (PTS) and selected mapping (SLM) techniques in orthogonal frequency-division multiplexing passive optical network (OFDM-PON). The digital chaotic sequences are employed in PTS/SLM schemes to encrypt the OFDM data, which provides a huge key space to enhance the physical layer confidentiality. Transmission of 8.9Gb/s 16QAM encrypted OFDM signals is demonstrated over 20km standard single-mode fiber, which shows the security enhancement against malicious eavesdropping or exhaustive attacks. Moreover, the proposed secure schemes improve the OFDM transmission performance since the peak-to-average power ratio (PAPR) of the OFDM signals is significantly reduced by the signal scrambling.

Physical layer signal encryption using digital chaos in OFDM-PON

Fiber optical network offers higher data rate and larger capacity transmission, however the security issues are becoming a big concern. Digital chaos is capable of providing a huge key space for data encryption in physical layer, to enhance network security during high-speed data transmission. We will review the recent progress on security enhancement via the implementation of digital chaos for high-speed signal encryption, especially in orthogonal frequency-division multiplexing passive optical network (OFDM-PON). As examples, we will focus on the recently-proposed two novel security schemes using chaotic signal scrambling: partial transmit sequence (PTS) and selected mapping (SLM). It has been shown that, the digital chaotic schemes not only guarantee the network data security against malicious eavesdropping or exhaustive attacks, but also simultaneously improve the transmission performance. This is due to the significantly reduction in the peak-to-average power ratio (PAPR) of the OFDM signals via PTS or SLM. Experimentally, encrypted data transmissions of 8.9Gb/s 16QAM OFDM signals are demonstrated over 20km standard singlemode fiber (SSMF) using chaotic PTS and SLM approaches.

Understanding bandwidth enhancement of all-optical turbo-switch

We propose a detailed frequency-domain model of the all-optical turbo-switch incorporating two cascaded semiconductor optical amplifiers (SOAs) with a broad band-pass optical filter in between the SOAs. The frequency-domain SOA model has taken the spatial inhomogeneity of the saturated SOA gain associated with the pump optical field into consideration for the first time. The simulations based on the model have been presented to understand the reason of the bandwidth enhancement and to predict the 3-dB bandwidth of frequency response of the turbo-switch. With the optimization of the optical powers, waveguide loss and a delayed-interferometer, the 3-dB bandwidth of turbo-switch can reach up to 270 GHz.

Physical layer encryption algorithm for chaotic optical OFDM transmission against chosen-plaintext attacks

We propose and analyze a novel physical layer security scheme with the capability of resisting the chosen plaintext attacks in OFDM data transmission. The proposed security scheme consists of a multiple-fold data encryption based on hyper digital chaos, which provides a huge key space. The first chaotic encryption is applied in the chaotic OFDM subcarrier allocation scrambling, both in time and frequency domains. The second encryption is the introduction of chaotic phase rotation of the OFDM signals, where the amount of phase rotation is determining by both of a chaotic sequence and the original input plain data. As a result, it provides a dynamic key system and the generated ciphertexts will be influenced by the original data, which is a core feature against the chosen-plaintext attacks. The proposed security scheme is successfully verified via numerical simulations.

Frequency chirp compensation of directly modulated DBR laser

We propose a model to analyze the frequency chirp of directly modulated distributed Bragg reflector (DBR) laser by evaluating the carrier dynamics in DBR. Due to the opposite sign of chirp in the gain and phase sections, the chirp compensation is achieved by injecting simultaneously injecting the data signals into both of the phase and gain sections in DBR laser. The simulation shows that, the overall chirp can be fully compensated, while the residual chirp at the rising and falling edges is only ~2 GHz. Moreover, the corresponding spectrum linewidth is significantly compressed after effective chirp compensation.

Secure optical OFDM signal transmission using electro-optic chaos

We propose a novel security scheme to encrypt OFDM signal transmission by introducing the electro-optic chaos in optical physical layer. The transmission performance of OFDM signals is numerically evaluated with respect to the signal-noise ratio (SNR) of the chaotic channel, to guarantee both of the robust security and high quality transmission. The optimized key parameters such as the chaotic masking ratio and the channel SNR are also given to facilitate the practical implementation.

All-optical encryption/decryption for nonreturn-to-zero differential phase-shift keying signals using four-wave mixing in semiconductor optical amplifier

Abstract. By experiment we demonstrate an all-optical encryption/decryption scheme for nonreturn-to-zero differential phase-shift keying (NRZ-DPSK) signals at 10u2009u2009Gbit/s using all-optical exclusive-OR (XOR) logic. The key bit stream is performed by a pseudorandom bit stream. The all-optical XOR logic is achieved by nondegenerate four-wave mixing (FWM) in a semiconductor optical amplifier (SOA), which allows high data rate operation and asymmetric optical powers of the two input bit streams. The gain dynamics and pattern effect associated with the SOA carrier lifetime are alleviated due to the constant envelope of the NRZ-DPSK signals.