纯音脉冲强度JND测试值与SPIN理论严重背离

对不同持续时间 1 k Hz纯音的强度 JND的测量表明 ,Weber比随信号持续时间的增加而减小 ,减小的速度随信号持续时间的增加而减缓 ,到信号持续时间增加到 5s时 Weber比不再随信号持续时间的增加而减小 ,此时 Weber比随强度的变化与 Weber定律极为接近 ,而与内部泊松内部噪声 ( PIN)理论、以及饱和内部泊松内部噪声 ( SPIN)

A 3-D Polarization Quadrature Amplitude Modulation Method and Constellation Mapping

As a new three-dimensional(3-D)modulation,Polarization Quadrature Amplitude Modulation(PQAM) can be regarded as the combination of Pulse amplitude modulation(PAM) and Quadrature Amplitude Modulation(QAM) Modulation.It can better improve the digital communication efficiency and reduce the Symbol error rate(SER) of the system than one-dimensional or two-dimensional modulation scheme.How to design a feasible constellation is the most concerned problem of PQAM currently.This paper first studies the relationship between the SER theoretical value of PQAM and the distribution of M and N,proposes a new M,N allocation scheme.Secondly,a new and straightforward design method of constructing higher-level 3-D signal constellations,which can be matched with the PQAM,and the constellation can divided into three different structures according to the ary for PQAM.Finally,the simulation results show that:in PQAM system,the modulation scheme and the constellation mapping scheme are proposed in this paper which can effectively reduce the system SER and improve the anti-noise performance of the system.

A new LDPC decoding scheme for PDM-8QAM BICM coherent optical communication system

A new log-likelihood ratio(LLR) message estimation method is proposed for polarization-division multiplexing eight quadrature amplitude modulation(PDM-8QAM) bit-interleaved coded modulation(BICM) optical communication system.The formulation of the posterior probability is theoretically analyzed,and the way to reduce the pre-decoding bit error rate(BER) of the low density parity check(LDPC) decoder for PDM-8QAM constellations is presented.Simulation results show that it outperforms the traditional scheme,i.e.,the new post-decoding BER is decreased down to 50%of that of the traditional post-decoding algorithm.

Evolution of downsized crescent-shaped dune in wind tunnel experiment

The migration of a downsized crescent-shaped dune was investigated in a wind tunnel experiment.Quantified upwind influx and vertical oscillation of the sand bed were introduced to modulate the saturation level of the sand flux above the dune surface to affect dune evolution.The evolution was recorded by top-view photography and then abstracted as the evolution of self-defined characteristic quantities using a digital image processing algorithm.The results showed that,in contrast to the case for spanwise quantities,the evolution of streamwise quantities corresponds to a linear increase in the modulation magnitude more positively and in a monotonic and convergent manner.In contrast with quantities on the windward face,the changes in quantities with respect to the horns were nonmonotonic with time and almost uncorrelated with the variation in modulation strength,which reveals the distinctiveness of leeside evolution.

A novel chromatic dispersion monitoring method for 1 024 QAM fiber-optic system based on asynchronous amplitude sampling

A new chromatic dispersion(CD) monitoring method is proposed, and the CD monitoring is achieved on the whole range of 0—600 ps/nm. A dual-polarization(DP)-1 024 quadrature amplitude modulation(QAM) 400 Gbit/s CD monitoring system is built using OptiS ystem14.0 software. With different optical signal to noise ratio(OSNR) values, different filter bandwidths or different duty cycles, the simulations are carried out. The simulation results show that this new CD monitoring method can be less affected by noise and has a high tolerance for different filter bandwidths. At the same time, this method can do effective CD monitoring on the signal with duty cycle greater than 80%. A high sensitivity in 0—200 ps/nm can be achieved using this CD monitoring method. The technique supports a wide range of data traffic and enhances operation flexibility of optical networks.