Performance of a snoring noise control system based on an active partition

This paper proposes an active partition that can be placed between a snorer and a non-snorer on a bed to reduce the snoring noise around the non-snorer ears by integrating a rigid finite size passive partition with a two channel active noise control system. The noise reduction performance of the passive partition on a bed with a headboard is studied first, where the effects of the height and the width of the partition are discussed. Due to the limited partition size, the attenuation for the low-frequency diffracted noise is not sufficient, so two loudspeakers are proposed to be installed on the partition as the secondary sources to increase the overall noise attenuation. Both numerical simulations and experiments are carried out to demonstrate the feasibility of the proposed integrated snoring noise control system, and the results show that the proposed active partition can achieve over 10 dB noise attenuation at non-snorer ears in the 1/3 octave bands from 80 to 1000 Hz.     

Statistical-mechanics theory of active mode locking with noise

Actively mode-locked lasers with noise are studied employing statistical mechanics. A mapping of the system to the spherical model (related to the Ising model) of ferromagnets in one dimension that has an exact solution is established. It gives basic features, such as analytical expressions for the correlation function between modes, and the widths and shapes of the pulses [different from the Kuizenga-Siegman expression; IEEE J. Quantum Electron. QE-6, 803 (1970)] and reveals the susceptibility to noise of mode ordering compared with passive mode locking.     

Quantum partition noise of photon-created electron-hole pairs

We show experimentally that even when no bias voltage is applied to a quantum conductor, the electronic quantum partition noise can be investigated with GHz radio frequency excitation. Using a quantum point contact configuration as the ballistic conductor we are able to make an accurate determination of the partition noise Fano factor resulting from the photon-assisted shot noise. Applying both voltage bias and rf irradiation we are able to make a definitive quantitative test of the scattering theory of photon-assisted shot noise.     

Linewidth and relative intensity noise measurements of longitudinal modes in ultrahigh-speed mode-locked laser diodes

The longitudinal linewidth and corresponding relative intensity noise (RIN) of 10- and 40-GHz mode-locked laser diodes are measured for the first time to our knowledge. It is shown that the cavity Q value is a dominant parameter of the linewidth. It is also shown that the linewidth of the individual modes is almost constant. This means that the phase noise of each mode is almost the same in the mode-locked condition. The RIN value is larger for modes that are distant from the center longitudinal mode. This mode dependence is a consequence of the mode partition noise.     

Sampling time effects on signal-to-noise and contrast-to-noise ratios in spin-echo MRI

This work discusses the effect of sampling time on noise, signal-to-noise and contrast-to-noise ratios in magnetic resonance imaging. A simple imaging experiment is performed to demonstrate the effect of sampling time on noise, confirming theoretical expectations that doubling the sampling time while decreasing the read gradient strength by a factor of two reduces statistical noise to 1/square root 2 of its original level. This result suggests that sampling time should be maximized within the constraints of the pulse sequence: namely, that sampling time should be increased and read gradient strength decreased as TE is increased. Revised expressions for signal-to-noise and contrast-to-noise ratios are presented based on the assumption that sampling time increases linearly with echo delay time above a certain minimum TE value. The revised expressions are then used to derive new predictions of the interpulse delay times that maximize signal-to-noise and contrast-to-noise ratios in spin-echo imaging. It is demonstrated that sampling times are critical in determining whether T1-weighted or T2-weighted sequences produce superior tissue contrast in spin-echo imaging.     

Influence of dephasing on shot noise in an electronic Mach-Zehnder interferometer

We analyze shot noise under the influence of dephasing in an electronic Mach-Zehnder interferometer, of the type that was realized recently [Nature (London) 422, 415 (2003)]]. Using a model of dephasing by a fluctuating classical field, we show how the usual partition noise expression T(1-T) is modified. We study the dependence on the power spectrum of the field, which is impossible in simpler approaches such as the dephasing terminal, against which we compare. We remark on shot noise as a tool to distinguish thermal smearing from genuine dephasing.     

Analytical expressions for the intensity and frequency noise of an individual mode in a multimode semiconductor laser with external optical feedback

Analytical expressions are derived for the intensity and frequency noise of each individual mode in a multimode semiconductor laser with external optical feedback. It is shown that in a two-mode laser the side-mode effect on the intensity noise is enhanced by the optical feedback which gives the maximum linewidth narrowing.     

近红外“3R”法双谱自适应去噪

针对近红外透射和吸收双光谱提出一种自适应的去噪方法。同步采集样品的近红外透射谱和吸收谱,在相同分解原则下总体经验模态法分解两组光谱,得到单组分特征模态分量。计算特征模态分量与原透射谱、吸收谱之间相关性,以及两组特征模态分量之间相关性,相关性最小模态分量初判为噪声分量。分析该分量在光谱中点处自相关性,若中点处很大,其他点几乎为零或很小,可以判断该分量为噪声。这种基于模态分量相关性的噪声判别方法称为“3R”法则。剔除噪声分量,重构光谱信号,循环上述分解过程,直到不满足“3R”法则,降噪过程结束。构造理想光谱,叠加噪声,“3R”法降噪效果优于EMD和EEMD低通滤波器,略逊于小波分解。真实光谱实验中,经过上述方法降噪处理过的玉米叶片光谱采用3层BP神经网络建立与叶绿素之间预测模型,“3R”法处理模型具有最大校正相关系数和预测相关系数,最小校正标准差和预测标准差。在四种降噪方法中,“3R”法对光谱谱峰位置和峰高的影响最小。实验表明,“3R”双谱去噪方法无需预设迭代次数,不用考虑分解层数,没有基函数,是自适应的,该方法适合近红外光谱去噪。     

Raman-noise-induced noise-figure limit for chi(3) parametric amplifiers

The nonzero response time of the Kerr [chi(3)] nonlinearity determines the quantum-limited noise figure of chi(3) parametric amplifiers. This nonzero response time of the nonlinearity requires coupling of the parametric amplification process to a molecular-vibration phonon bath, causing the addition of excess noise through Raman gain or loss at temperatures above 0 K. The effect of this excess noise on the noise figure can be surprisingly significant. We derive analytical expressions for this quantum-limited noise figure for phase-insensitive operation of a chi(3) amplifier and show good agreement with published noise-figure measurements.     

Suppression of mode partition noise in a multiwavelength semiconductor laser through hybrid mode locking

We demonstrate the suppression of intensity fluctuations, which are known as mode partition noise, in a multiwavelength semiconductor laser by using a hybrid mode-locking scheme. The laser design incorporates a saturable absorber and a gain-modulated semiconductor optical amplifier, along with spectral filtering, in an external cavity to achieve multiwavelength hybrid mode locking. The mode-locked laser produces an error-free (pulse Q>13) 300-MHz optical pulse train in each of three wavelength channels.     

Approach to block entropy modeling and optimization

This paper introduces an approach to the block entropy modeling of stationary signals. The block entropies, constructed according to the Tsallis generalized formalism, are optimized with respect to the block length and the partition of the signal value domain, to appropriately measure the complexity of the signal. The optimal partition is known to be addressed by the Euclidean mean, expressing the signal optimized level based on the least squares fitting method. However, this is valid only for random signal values following a symmetric distribution. Alternatively, and within the framework of fitting methods based on non-Euclidean metrics, we implement the qth order means to consistently describe the optimal signal level, and to clearly present the difference between the optimal signal level and the optimal partition. The signal optimization is utilized for detecting the distribution modes, developing a technique, being resistant to the noise corruption, that can be useful for detecting the optimal partition. Moreover, the mechanisms that affect the optimal partition are identified and thoroughly investigated. We first consider random signals following an arbitrary distribution, where the block entropy modeling reveals that the optimal partition is located at the median. Thereafter, we consider persistent signals, specifying a degree of determinism, where the optimal partition is found to be driven far from the median and close to the persistent mode. The existence of persistent modes of small hitting time is the key point of this dissertation, highlighting their implications on the block entropy modeling. Finally, efforts towards block entropy modeling of non-stationary signals are discussed.     

Fractionalization noise in edge channels of integer quantum Hall states

A theoretical calculation is presented of current noise which is due charge fractionalization, in two interacting edge channels in the integer quantum Hall state at filling factor ν=2. Because of the capacitive coupling between the channels, a tunneling event, in which an electron is transferred from a biased source lead to one of the two channels, generates propagating plasma mode excitations which carry fractional charges on the other edge channel. When these excitations impinge on a quantum point contact, they induce low-frequency current fluctuations with no net average current. A perturbative treatment in the weak tunneling regime yields analytical integral expressions for the noise as a function of the bias on the source. Asymptotic expressions of the noise in the limits of high and low bias are found.     

Information Theory Applied to Parameter Inference of Pake Doublet Spectra

Magnetic resonance absorption lineshapes can have subtle dependencies on the model parameters that specify the lineshape. To quantify how the model parameters influence the lineshape, it is useful to study simple model systems for which analytical expressions are available. We propose that information theory is a useful tool to quantify how well model parameters may be inferred from a noisy signal. Information theory also allows us to assess the importance of missing parameters from an incomplete model. We do this by monitoring the magnitude of a partition function determined from a suitably defined probability mass function as the model parameters are varied. The optimum parameter set makes the partition function a maximum, which establishes a computable criterion for determining the best model parameter set. Given the availability of a partition function, one may define thermodynamic functions such as the entropy. The optimum parameter set in this interpretation corresponds to the state of maximum entropy. In this work, we observe that at sufficiently low signal to noise ratio, the entropy landscape has no clear maximum, while a related quantity, the Fisher information, always has a clear minimum at the optimum parameter set. The qualitative information we are able to gather from the entropy landscapes is also difficult to assess when the parameters are far from their optimum values, at least for the model system studied here.     

Fluctuations in doubly scattered laser light

Fluctuations in laser light, doubly scattered by brownian particles, were analysed by measuring the spectral noise power of the photodetector current. Scattering took place at two spatially separated systems of spherical particles. Analytic expressions for the field and intensity correlations are derived. The analytic expressions for the spectrum of the intensity fluctuations of the doubly scattered laser light demonstrate that the frequency dependence of the spectrum depends strongly of the geometry of the experimental arrangement. This is not the case for singly scattered light where in good approximation the spatial and temporal correlations can be separated analytically.Our measurements show that the noise spectrum of the doubly scattered radiation may have the same frequency dependence as the spectrum of the singly scattered light. However, there are conditions where the frequency dependence of the noise of the doubly scattered light diverges markedly from that of the singly scattered light.     

Analysis of bit error rate and power penalty for a birefringent wavelength division multiplexer

The power penalty and bit error rate degradation encountered when using wavelength division multiplexing devices is analyzed. Analysis is applied to the birefringent wavelength division multiplexer (BWDM) with a sinusoidal transfer function.¹ The degradation in bit error rate is attributed to laser mode partition noise and crosstalk noise.     

The Mean First-Passage Time for Nonlinear Non-Markovian Continuous Noise

A method for calculating the mean first-passage time for non-Markovian free processes driven by continuous noise is generalized to free process X(t)=g[F(t)] and unfree process X( t)=f[X(t)]g[F(t)] with nonlinear noise. When the switch distribution + rectangular, the exact analytic expressions of the mean first-passage time for free process X(t) = [F(t)]^m driven by nonlinear noise and X( t=) -k[X(t)]ⁿ[F(t)lm+ [F(t)]^m driven by both multiplicative and nonlinear additive noises are also given.     

Analysis of bit error rate and power penalty for a birefringent wavelength division multiplexer

The power penalty and bit error rate degradation encountered when using wavelength division multiplexing devices is analyzed. Analysis is applied to the birefringent wavelength division multiplexer (BWDM) with a sinusoidal transfer function.¹ The degradation in bit error rate is attributed to laser mode partition noise and crosstalk noise.     

Effect of nonlinear gain on the phase noise of Y-branch lasers

Effect of nonlinear gain on the phase noise of modulated grating Y-branch (MGY) lasers is investigated by experiments and simulations. The phase noise is first characterized by measuring the frequency modulation noise spectrum of the MGY laser, and some interesting phenomena are observed. In order to understand the underlying physic mechanism of those phenomena, simulations are performed with taking Langevin noise sources and nonlinear gain terms into account. Simulated results show that, in the presence of the nonlinear gain, fluctuations of side-modes can bring excess phase noise to the lasing mode, especially when the side-modes are on the long-wavelength side of the main mode. Furthermore, it has been found that the phase noise hopping phenomenon can be induced by a bi-stable state of the laser, which is also closely related to the nonlinear gain. The investigation is helpful for explaining the complicated phase noise characteristics of the MGY laser.     

噪声模态单元预判的经验模态分解脉冲星信号消噪

为了改善脉冲星辐射脉冲信号的消噪效果, 提出了一种基于噪声模态单元预判的经验模态分解(EMD) 消噪声方法. 该方法首先利用EMD将含噪辐射脉冲信号分解为一组内蕴模态函数(IMF), 根据IMF系数的统计特性采用局部均方误差准则进行噪声模态单元预判, 并将噪声模态单元置零; 然后对噪声模态单元预判处理后的IMF以模态单元为基本单位进行最优比例萎缩消噪, 从而达到抑制噪声、保留信号的目的. 实验结果表明: 与Sure Shrink小波阈值法、Bayes Shrink小波阈值法和EMD模态单元比例萎缩法相比, 基于噪声模态单元预判的EMD消噪方法可以更有效地去除脉冲辐射信号中的噪声, 同时更好地保留信号突变处的细节信息特征, 在信噪比、 均方误差、峰值相对误差、峰位误差和相位误差等方面都有一定程度的改善. 关键词： 脉冲星信号消噪 经验模态分解 噪声模态单元预判 局部均方误差