Secure optical communication system based on polarization regulation of the data fragmentation multipath transmission technology.

We propose and demonstrate a data fragment multipath transmission scheme to achieve a secure optical communication based on polarization regulation. A dual-polarization Mach-Zehnder modulator (DPMZM) is driven by digital signals which are scattered by field-programmable gate array (FPGA) and transmitted in multiple paths. By utilizing two orthogonal polarization states, we have achieved a signal transmission under different optical parameters, and the transmission rate of the two paths can reach over 10 Gbps through a 20 km fiber with 2.5 Gbps hopping rate. In addition, we establish a theoretical model to analyze the security of the system and simulate brute force cracking; the probability of cracking the minimum information unit is 1.53 × 10-53. This proves that it is difficult to obtain a user data even using the fastest computers. Our scheme has provided, to our knowledge, a new approach for physical layer security.

100 Gb/s NRZ OOK signal regeneration using four-wave mixing in a silicon waveguide with reverse-biased p-i-n junction.

A silicon waveguide with reverse-biased p-i-n junction is used to experimentally demonstrate all-optical regeneration of non-return-to-zero (NRZ) on-off keying (OOK) signal based on four-wave mixing. The silicon waveguide allows a high conversion efficiency of -12 dB. The 0.22 dB (1.1 dB) quality (Q) factor and 0.74 dB (6.3 dB) extinction ratio (ER) improvements on average are achieved for 100 Gb/s (50 Gb/s) NRZ OOK signal regeneration at different receiving powers via the optimal match between the input signal optical power and input-output transfer curve. To the best of our knowledge, this silicon-based all-optical regenerator exhibits superior regeneration performance, including large ER and Q factor improvements, and the highest regeneration speed of NRZ OOK signal, and it has wide applications in 5 G/6 G networks.

Ultrahigh spectral resolution single passband microwave photonic filter.

Microwave photonic filters (MPFs) with only one ultra-narrow passband are able to provide high frequency selectivity and wide spectral range, and they are of great importance in radio-frequency (RF) signal processing. However, currently all MPFs are limited by trade-offs between key parameters such as spectral resolution and range, tunability, and stability. Here, we report the first demonstration of a single passband MPF with unprecedented performance including ultrahigh spectral resolution of 650 kHz, 0-40 GHz spectral range, and high stability of center frequency drifting within ±50 kHz. This record performance is accomplished by breaking the amplitude equality of a phase-modulated signal via a Brillouin dynamic grating (BDG) which has an ultra-narrow reflection spectrum of sub-MHz. The results point to new ways of creating high performance microwave photonic systems, such as satellite and mobile communications, radars, and remote-sensing systems.

Ultrahigh-Q and tunable single-passband microwave photonic filter based on stimulated Brillouin scattering and a fiber ring resonator.

A scheme to perform ultrahigh-Q and single passband microwave photonic filter (MPF) with tunability is proposed and experimentally demonstrated. The single passband of the MPF is implemented by the stimulated Brillouin scattering (SBS) in an optical fiber. The ultrahigh-Q of the MPF is realized due to the ultra-narrow resonant linewidth of the fiber ring resonator, which compresses the bandwidth of the SBS dramatically. A MPF with a single passband and an ultra-narrow 3 dB bandwidth of 825±125 kHz over the wide center frequency tuning range of 2-16 GHz are achieved. The MPF also shows high out-of-band suppression exceeding 25 dB and small amplitude fluctuation of ±1.8 dB within the tuning range. The maximum Q-factor of the MPF is 17778. To the best of our knowledge, this is the highest Q single-passband MPF reported to date, with wide tunability, high out-of-band suppression, and a simple structure.