Critical Petermann K-factor for intensity noise squeezing

Joint probabilistic data association (JPDA) is a powerful tool for solving data association problems. However, the exact computation of association probabilities {/spl beta//sub jk/} in JPDA is NP-hard, where /spl beta//sub jk/ is the probability that j-th observation is from k-th track. Hence, we cannot expect to compute association probabilities in JPDA exactly in polynomial time unless P = NP. In this paper, we present a simple Markov chain Monte Carlo data association (MCMCDA) algorithm that finds an approximate solution to JPDA in polynomial time. For /spl epsiv/ > 0 and 0 < /spl eta/ < .5, we prove that the algorithm finds good estimates of /spl beta//sub jk/ with probability at least 1 - /spl eta/ in time complexity O(/spl epsiv//sup -2/ log /spl eta//sup -1/N(N log N + log /spl epsiv//sup -1/))), where N is the number of observations.

We have developed a new simulation methodology for predicting shot noise intensity in Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET). In our approach, shot noise in MOSFETs is calculated by employing a two dimensional device simulator in conjunction with the shot noise model of a p-n junction. The accuracy of the noise model has been demonstrated by comparing simulation results with measured noise data of p-n diodes. The intensity of shot noise in various n-MOSFET devices under various bias conditions was estimated beyond GHz operational frequency by using our simulation scheme. At DC or low-frequency region, sub-threshold current dominates the intensity of shot noise. Therefore, shot noise is independent on frequency in this region, and its intensity is exponentially depends on V G , proportional to L -1 , and almost independent on V D . At high-frequency region above GHz frequency, on the other hand, shot noise intensity depends on frequency and is much larger than that of low-frequency region. In particular, the intensity of the RF shot noise is almost independent on L, V D and V G . This suggests that high-frequency shot noise intensity of MOSFETs is decided only by the conditions of source-bulk junction.

The concept of diffusive representation is used in this paper for modeling purposes in the field of electrical engineering, namely when some non-rational dynamics are involved. Diffusive formulations are convenient for analysis and cheap numerical approximations. We study the problem of time-domain identification of the so-called diffusive symbol /spl eta/(/spl xi/) associated to the permittivity /spl epsiv/(p) of dielectric material. The so obtained state-space models allow simple and precise time-domain simulation of such dynamical components.

Differential displacement due to a gravitational force gradient, acting on two superconducting test masses which are elastically suspended from the instrument frame, is sensed by a superconducting quantum interference device (SQUID), coupled to the masses by a current flowing in the sensing circuits. The SQUID transducer absorbs energy from the masses, and, hence, it reacts with a random force (fluctuation-dissipation principle). This force increases if the coupling current grows. Additionally, the transducer outputs an amplification noise that is independent of the coupling. This output noise is equivalent to a force, applied to the masses, which decreases with stronger coupling, Hence, the strength of the total equivalent gravity gradient noise has a minimum with respect to the coupling. The minimum is found to be about 1.5/spl epsiv//sub A//spl omega//sub 0//sup 2//(ml/sup 2/), where /spl epsiv//sub A/ means the equivalent energy sensitivity, in the white noise limit, of the SQUID junctions; /spl omega//sub 0/ is the natural frequency of the mass suspension; m is the test mass, and l is the base length,.

On the basis of calculating the steady-state meannormalized intensity fluctuation of a signal-mode laser system driven byboth colored pump noise with signal modulation and the quantum noise withcross-correlation between its real and imaginary parts, we analyze theinfluence of modulation signal, noise, and its correlation form on thestatistical fluctuation of the laser system. We have found that when theamplitude of modulation signal weakens and its frequency quickens, thestatistical fluctuation will reduce rapidly. The statistical fluctuation ofthe laser system can be restrained by reducing the intensity of pump noiseand quantum noise. Moreover, with prolonging of colored cross-correlationtime, the statistical fluctuation of laser system experiences a repeatedchanging process, that is, from decreasing to augmenting, then todecreasing, and finally to augmenting again. With the decreasing of thevalue of cross-correlation coefficient, the statistical fluctuation willdecrease too. When the cross-correlation form between the real part andimaginary part of quantum noise is zero correlation, the statisticalfluctuation of laser system has a minimum. Compared with the influenceof intensity of pump noise, the influence of intensity of quantum noise onthe statistical fluctuation is smaller.

In this paper, a distributed Bragg reflector single-frequency fiber laser (SFFL) operating at 1550nm with ultra-narrow linewidth and near shot-noise-limited intensity noise is demonstrated experimentally. The low-noise fiber laser employs a short linear-cavity based on Er3+/Yb3+ co-doped phosphate fiber, achieving stable single-longitudinal-mode operation through a multi-technique noise-suppression scheme. By incorporating self-injection locking, pump noise optimization, optoelectronic feedback, and the gain saturation effect of a semiconductor optical amplifier to improve the noise performance, the SFFL exhibits a linewidth of less than 89Hz. The relative intensity noise of the fiber laser is reduced to near the shot-noise limit (-156dB/Hz at 1mW), with measured values of approximately -152.5dB/Hz in the 2-10kHz frequency range and -155dB/Hz in the 1-10MHz frequency range. Furthermore, the optical signal-to-noise ratio exceeds 70dB, and the polarization extinction ratio is greater than 26dB. These combined techniques enable the SFFL to simultaneously achieve an ultra-narrow linewidth (sub-100Hz level) and low intensity noise, rendering it suitable for demanding applications such as coherent optical communications, precision metrology, and laser cooling.

The noise properties of supercontinuum (SC) sources are of importance in many applications. This intensity noise of the SC arises from nonlinear amplification of the input-pulse shot noise and the spontaneous Raman scattering down the fiber [1]. Low noise femtosecond SC generation (SCG) has previously been demonstrated [2]. However, in commercial SC sources, the SC is generated by pumping with picosecond to nanosecond pulses and the SCG is thus initiated by modulation instability (MI). Therefore, the SC is characterized by low coherence and high shot-to-shot fluctuations, in particular at the spectral edges [3-5]. However, the influence of the noise properties when pumping in the normal dispersion regime has so far not been investigated for long pulse pumping. In this work we have measured and compared the relative intensity noise (RIN) properties of long-pulse MI initiated SCG in three different regimes: (i) all-normal SCG, (ii) normal-pumped SCG where higher-order Raman lines occur in the anomalous dispersion regime, and (iii) anomalous-pumped SCG. We show that the noise properties for the three regimes are similar: when increasing the input pump power, the intensity noise will continuously decrease for a given wavelength, and for a given input power the intensity noise will be lowest at the pump wavelength and increase when moving towards the spectral edge [6].

We have studied the gain and noise characteristics of a Brillouin amplifier, both when it is used to amplify weak signals and when it is used for phase conjugation. The amplifier consists of a 20-cm long cell filled with TiCl4 which is pumped by a 25-ns pulse from a near diffraction-limited injection seeded Nd:YAG laser. The Brillouin gain is given by G B = exp(gIpL), where I p is the input pump intensity; and gains in excess of 109 have been measured for signals of 500 fJ. The observed signal-to-noise ratio is 85:1; within a factor of 16 of the theoretical limit. In the absence of a signal, the output noise is observed to vary as Nout = N o G B /g, where N o is a spontaneous scattering term equivalent to an input noise signal. When an aberrator is placed in front of the beam, the intensity of noise which is conjugate to the pump beam is enhanced by a factor J &gt; 2, i.e., Nout pc = N o G J /Jg. The enhancement factor depends on the speckle in the pump beam, and observed values of J &gt; 3 are larger than predicted by theory.

In this paper the performance of Incoherent SAC OCDMA system has been evaluated in a noisy environment using ZVCC (Zero Vector Combinatorial Code set). CDMA system allows multiple users to access the channel simultaneously but is limited by some problems like MAI (multiple access interference), PIIN (Phase induced intensity noise), thermal noise, and shot noise still exists in this system. It is observed from the results that as effective power is increased, the intensity noise becomes the main factor of performance degradation of the system.

It is shown that by attenuating the reference power in an optical low-coherence reflectometry (OLCR) measurement, the reflection sensitivity can be improved, even though, in many other types of optical measurements, sensitivity is improved as optical power is increased. The difference is due to the presence of inherent intensity noise associated with low-coherence sources, which can dominate over shot noise at optical powers that are as low as 1 mu W. A reflection sensitivity of -146 dB is demonstrated using this technique.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

ABSTRACTRadio emissions were observed by Voyager 1 and Voyager 2 planetary radio astronomy experiments during saturnian ring plane crossings. Several mechanisms are proposed and tested. Quasi-thermal noise is negligible. Shot noise due to electrons and ions collected and/or emitted by antennas and spacecraft can explain not too intense noise. However, for the strong noise in the ring plane, observed by Voyager 2 at ~ 2.9 Rs, we must take into account shot noise due to grain impacts. A quantitative evaluation of this process gives an estimation of the dust size ~ 1.1 µm close to the G ring.

Photonic neural networks have emerged as a promising solution to overcome limitations of traditional hardware for neuromorphic computations, offering advantages in bandwidth, latency, and power efficiency. However, their performance is constrained by the limited precision of analog photonic computing, which is affected by inherent noise sources such as thermal and shot noise, and distortions. These effects degrade the photonic neural network performance, reducing the bit resolution achievable in photonic hardware typically to 2–4 bits. Traditional quantization strategies fail to account for these noise contributions, resulting in a substantial accuracy loss during inference. This paper introduces an adaptive quantization method called Adaptive-Quantization Photonic-Aware Neural Network (AQ-PANN) to address the challenges posed by different noise sources in analog photonic hardware. The proposed method uses a learnable step size quantization scheme to achieve high accuracy and stability under varying noise levels, introducing a scheme that unifies quantization step adaptation with noise injection exactly where photonic distortions arise. This design incurs only a minor training-time overhead, as it involves learning a small number of per-layer quantization step sizes and does not affect inference. Experimental evaluations on three commonly used test datasets (MNIST, SVHN, and CIFAR-10) with different bit resolutions show the robustness of AQ-PANN. On MNIST, an accuracy drop of only 2% was observed from low to high noise levels in a 4-bit configuration, while traditional DoReFa quantization suffered a 29% drop. For the SVHN dataset, AQ-PANN obtained a mean accuracy of 92% under high noise with 4-bit quantization, outperforming DoReFa by over 45%. On CIFAR-10, AQ-PANN maintained close to 60% accuracy under high noise in the 4-bit configuration, whereas DoReFa and PACT both collapsed below 40%. These results highlight the effectiveness of AQ-PANN in sustaining model performance across different noise intensities, enabling practical photonic neural network deployment.

The dominant noise source, which effects the electron dynamics in semiconductor nano‐structures, is shot noise, which is associated with the tunneling of individual carriers across a potential barrier. We consider noise‐induced dynamics of electrons in a superlattice, which consists of alternating layers of two semiconductor materials with different band gaps. The parameters are fixed in the regime below the Hopf bifurcation of spatio‐temporal oscillations, where in the absence of noise the system rests in a fixed point. It is shown that in this case noise applied to the superlattice can induce quite coherent oscillations of the current through the device. While the regularity of these oscillations depends on the noise intensity, their dominant frequency remains almost constant with variation of the noise level in the system. Further, we demonstrate that a time‐delayed feedback scheme that was previously used to control purely temporal oscillations induced by noise, can not only enhance or deteriorate the regularity of stochastic spatio‐temporal patterns but also allows for the manipulation of the system’s timescales with varying time delay.

In this study, five deaf individuals with cochlear implants were presented with noise that was manipulated systematically, to test the hypothesis that deaf persons using cochlear prostheses will demonstrate intensity regulation of their vocal output that is more appropriate when their implants are turned on than when turned off. The intensity of their vocal output was measured to determine if they demonstrated a Lombard response, that is, a systematic increase in vocal intensity with increasing intensity of background noise. Results from the study were mixed. With implants on, three subjects made systematic increases in vocal intensity with increasing background noise, while two subjects did not make such increases. In addition, the relation between intensity of vocal output and background noise was closer to the normal function for the three subjects who demonstrated a Lombard response. The "normal function" was defined by measuring the vocal intensity responses of five normal hearing control subjects who performed the same tasks as the experimental subjects.

We develop a general approach to including the internal optical loss in the description of semiconductor lasers with a quantum-confined active region. We assume that the internal absorption loss coefficient is linear in the free-carrier density in the optical confinement layer and is characterized by two parameters, the constant component and the net cross section for all absorption loss processes. We show that, in any structure where the free-carrier density does not pin in the presence of light generation, the free-carrier-density dependence of internal loss gives rise to the existence of a second lasing threshold above the conventional threshold. Above the second threshold, the light-current characteristic is two-valued up to a maximum current at which the lasing is quenched. We show that the presence of internal loss narrows considerably the region of tolerable structure parameters in which the lasing is attainable; for example, the minimum cavity length is significantly increased. Our approach is quite general but the numerical examples presented are specific for quantum dot (QD) lasers. Our calculations suggest that the internal loss is likely to be a major limiting factor to lasing in short-cavity QD structures.