In this paper,an optical pulse amplitude modulation with 4 levels(PAM-4)using a fiber combiner is proposed to enhance the data rate of a field-programmable gate-array-based long-distance real-time underwater wireless ...In this paper,an optical pulse amplitude modulation with 4 levels(PAM-4)using a fiber combiner is proposed to enhance the data rate of a field-programmable gate-array-based long-distance real-time underwater wireless optical communication system.Two on-off keying signals with different amplitudes are used to modulate two pigtailed laser diodes,respectively,and the generated optical signals are superimposed into optical PAM-4 signals by a fiber combiner.The optical PAM-4scheme can effectively alleviate the nonlinearity,although it reduces the peak-to-peak value of the emitting optical power by 25%.A real-time data rate of 187.5 Mbit/s is achieved by using the optical PAM-4 with a transmission distance of 50 m.The data rate is increased by about 25%compared with the conventional electrical PAM-4 in the same condition.展开更多
Security is one of the key issues in communications,but it has not attracted much attention in the field of underwater wireless optical communication(UWOC).This Letter proposes a UWOC encryption scheme with orthogonal...Security is one of the key issues in communications,but it has not attracted much attention in the field of underwater wireless optical communication(UWOC).This Letter proposes a UWOC encryption scheme with orthogonal frequency division multiplexing(OFDM)modulation,based on the three-layer chaotic encryption and chaotic discrete Fourier transform(DFT)precoding.The three-layer chaotic encryption processes are bit stream diffusion,in-phase/quadrature encryption,and time-frequency scrambling.With multi-fold data encryption,the scheme can create a keyspace of 9.7×10^(179),effectively resisting brute force attacks and chosen-plaintext attacks.A 3 Gbit/s encrypted OFDM signal is successfully transmitted over a 7 m water channel.展开更多
基金supported by the National Natural Science Foundation of China(NSFC)(No.61971378)Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA22030208)Zhoushan-Zhejiang University Joint Research Project(No.2019C81081)。
文摘In this paper,an optical pulse amplitude modulation with 4 levels(PAM-4)using a fiber combiner is proposed to enhance the data rate of a field-programmable gate-array-based long-distance real-time underwater wireless optical communication system.Two on-off keying signals with different amplitudes are used to modulate two pigtailed laser diodes,respectively,and the generated optical signals are superimposed into optical PAM-4 signals by a fiber combiner.The optical PAM-4scheme can effectively alleviate the nonlinearity,although it reduces the peak-to-peak value of the emitting optical power by 25%.A real-time data rate of 187.5 Mbit/s is achieved by using the optical PAM-4 with a transmission distance of 50 m.The data rate is increased by about 25%compared with the conventional electrical PAM-4 in the same condition.
基金supported by the National Natural Science Foundation of China(NSFC)(No.61971378)Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA22030208)Zhoushan-Zhejiang University Joint Research Project(No.2019C81081)。
文摘Security is one of the key issues in communications,but it has not attracted much attention in the field of underwater wireless optical communication(UWOC).This Letter proposes a UWOC encryption scheme with orthogonal frequency division multiplexing(OFDM)modulation,based on the three-layer chaotic encryption and chaotic discrete Fourier transform(DFT)precoding.The three-layer chaotic encryption processes are bit stream diffusion,in-phase/quadrature encryption,and time-frequency scrambling.With multi-fold data encryption,the scheme can create a keyspace of 9.7×10^(179),effectively resisting brute force attacks and chosen-plaintext attacks.A 3 Gbit/s encrypted OFDM signal is successfully transmitted over a 7 m water channel.
