Multimode Noise Research Articles

Fiber-Optic Sensor Spectrum Noise Reduction Based on a Generative Adversarial Network.

In the field of fiber-optic sensing, effectively reducing the noise of sensing spectra and achieving a high signal-to-noise ratio (SNR) has consistently been a focal point of research. This study proposes a deep-learning-based denoising method for fiber-optic sensors, which involves pre-processing the sensor spectrum into a 2D image and training with a cycle-consistent generative adversarial network (Cycle-GAN) model. The pre-trained algorithm demonstrates the ability to effectively denoise various spectrum types and noise profiles. This study evaluates the denoising performance of simulated spectra obtained from four different types of fiber-optic sensors: fiber Fabry-Perot interferometer (FPI), regular fiber Bragg grating (FBG), chirped FBG, and FBG pair. Compared to traditional denoising algorithms such as wavelet transform (WT) and empirical mode decomposition (EMD), the proposed method achieves an SNR improvement of up to 13.71 dB, an RMSE that is up to three times smaller, and a minimum correlation coefficient (R2) of no less than 99.70% with the original high-SNR signals. Additionally, the proposed algorithm was tested for multimode noise reduction, demonstrating an excellent linearity in temperature response with a R2 of 99.95% for its linear fitting and 99.74% for the temperature response obtained from single-mode fiber sensors. The proposed denoising approach effectively reduces the impact of various noises from the sensing system, enhancing the practicality of fiber-optic sensing, especially for specialized fiber applications in research and industrial domains.

Self-Injection-Locked Optoelectronic Oscillator Based on Frequency Conversion Filtering

The multi-mode noise is an important issue for the optoelectronic oscillator (OEO) in generating a spectrally pure microwave. Especially in oscillators with low phase noise, increasing the cavity length to improve the phase noise performance will make the mode interval smaller, which is more likely to cause multi-mode noise. Here, we proposed a low phase noise and high side-mode suppression ratio self-injection-locked OEO based on frequency conversion filtering. We theoretically and experimentally studied the influence of the phase noise of the external microwave source on the proposed OEO and, as a comparison, the conventional injection-locked OEO. The results show that, compared with the traditional injection-locked OEO, the proposed OEO is less sensitive to the phase noise of the external microwave source. Under the same experimental conditions, the proposed OEO achieved the same side-mode suppression ratio and the phase noise is reduced by 30 dB at 10 kHz offset from the 10-GHz carrier compared with the conventional injection-locked OEO.

An Erbium Fiber Laser With Single-Frequency Oscillation and Wavelength-Upconverted Output

In this paper, we present experimentally an erbium-doped fiber (EDF) laser system to accomplish the single-longitudinal-mode (SLM) and wavelength-upconverted output by using nonlinear effect. To accomplish the SLM output, a short length of unpumped EDF saturable absorber (SA) is applied inside the EDF laser cavity for filtering densely multi-mode noise. In accordance with the designed EDF laser system, the lasing wavelength can be upconverted to a longer wavelength position. In addition, the output characteristics of output power, optical signal to noise ratio (OSNR), tunability, stability and linewidth in the EDF laser are also discussed.

Structured light entities, chaos and nonlocal maps

Spatial chaos as a phenomenon of ultimate complexity requires the efficient numerical algorithms. For this purpose iterative low-dimensional maps have demonstrated high efficiency. Natural generalization of Feigenbaum and Ikeda maps may include convolution integrals with kernel in a form of Green function of a relevant linear physical system. It is shown that such iterative $nonlocal$ $nonlinear$ $maps$ are equivalent to ubiquitous class of nonlinear partial differential equations of Ginzburg-Landau type. With a Green functions relevant to generic optical resonators these $nonlocal$ $maps$ emulate the basic spatiotemporal phenomena as spatial solitons, vortex eigenmodes breathing via relaxation oscillations mediated by noise, vortex-vortex and vortex-antivortex lattices with periodic location of vortex cores. The smooth multimode noise addition facilitates the selection of stable entities and elimination of numerical artifacts.

Dynamics of bell-nonlocality for two atoms interacting with a vacuum multi-mode noise field

We investigate the internal-state Bell nonlocal entanglement dynamics, as measured by CHSH inequality of two atoms interacting with a vacuum multi-mode noise field by taking into account the spatial degrees of freedom of the two atoms. The dynamics of Bell nonlocality of the atoms with the atomic internal states being initially in a Werner-type state is studied, by deriving the analytical solutions of the Schrödinger equation, and tracing over the degrees of freedom of the field and the external motion of the two atoms. In addition, through comparison with entanglement as measured by concurrence, we find that the survival time of entanglement is much longer than that of the Bell-inequality violation. And the comparison of the quantum correlation time between two Werner-type states is discussed.

Multi‐mode noise parameters for multi‐port networks

This study derives an equation set by which the equivalent multi-mode noise parameters of a general multi-port receiver can be solved in terms of the noise parameters of the constituent single-ended (SE) low-noise amplifiers (LNAs). The expressions are used to derive equivalent differential- and common-mode noise parameters for a pair of balanced LNAs as well as the equivalent multi-mode noise parameters of four SE LNAs excited through a quadraxial transmission line.

Noise Sources for Duct Acoustics Simulations: Broadband Noise and Tones

Although simulating acoustic tones propagating in ducts or waveguides is relatively well established, broadband noise is composed of a wide range of frequencies, and at each frequency, the acoustic energy is generally distributed over all the cut-on modes of the duct. Simulating the propagation and absorption of broadband noise is further complicated by the random nature of the sound field. This paper presents a computational method to generate truly broadband, multimode noise in a time-domain simulation. This method is equally applicable to the generation of deterministic tones. For broadband noise, we devise a stochastic source that is tailored to radiate a sound field characterized by the cross-correlation between mode amplitudes. This stochastic source allows to compute in a single time-domain simulation the complete spectrum of the broadband multimode sound field. Unlike other methods proposed for predicting broadband noise, there is no need to perform several simulations for different realizations. Results are presented for broadband noise alone as well as for a combination of tones and broadband noise.

Broadband Wave Propagation from an Aeroengine Duct

Accurate and efficient computation of multimode/broadband noise propagating into and radiating out of a duct has both fundamental and practical interests, particularly for broadband turbofan noise problems. In this work, a new complex formulation of the linearized Euler equations is proposed in the time domain for accurate and efficient multimode noise computations via a single-mode summation approach. The approach achieves incoherent results by summation of individual predictions from excitation modes at all discrete frequencies. The solutions are obtained using high-order computational aeroacoustics algorithms. An advantage of the proposed formulation is that the number of computations is equal to the cuton mode number at the highest frequency regardless of the frequency sampling rate. Furthermore, the computation cost only increases marginally despite a doubling of the governing equations in real space. Tests show that the method could potentially achieve significant computational cost savings. This approach is compared with a time-domain random phase approach with which incoherent results are obtained by averaging the results from repeated simulations with random phases added to the wave inputs in each computation. Examples including a generic bypass engine duct are included to illustrate the reliability and efficiency of the method.

Quantum Recoil Effects of Spontaneous Emission on Disentanglement

By taking into account spatial degrees of freedom of atoms, we study the internal-state disentanglement dynamics of two atoms interacting with a vacuum multi-mode noise field. We show that the complete internal-state disentanglement of the two atoms, caused due to the atomic spontaneous emission can he achieved in a finite time.

A computational mode-matching approach for sound propagation in three-dimensional ducts with flow

A finite element (FE) mode-matching approach is presented for duct acoustics with flow and circumferentially varying liners. The primary application of the method is the prediction of sound attenuation in turbofan inlets and bypass ducts including the effects of liner splices. A fully numerical procedure has been developed to determine the acoustic modes in ducts of arbitrary cross-section and mean flow profile. A numerical mode-matching method is proposed using a modified matching technique in order to deal more accurately with liner discontinuity with flow. An analytic radiation model can also be integrated with the mode-matching procedure in order to obtain far-field directivity for tones and broadband multimode noise. The accuracy of the mode-matching method is demonstrated by comparison with exact solutions and high-resolution FE solutions. The influence of non-axisymmetric liners on noise radiation is also illustrated.

Fabrication of an Electro-Optical Temperature Sensor Based on Silicon Oxynitride Films Deposited by PECVD

We present the fabrication and characterization of an electro-optical temperature sensor based on silicon oxynitride dielectric films deposited by Plasma Enhanced Chemical Vapor Deposition at low temperatures (~300oC). The temperature sensor is basically a Mach-Zehnder interferometer such that a temperature difference between its arms produces a phase difference between the electromagnetic waves traveling through each arm thus originating a variation in the output optical power. In order to analyze the feasibility of this sensor, a temperature difference is imposed by applying a heating element in one of the arms. The results show that it is possible to control the optical device output through the adequate control of the heating element. Furthermore, the influence of heat propagation, multimode noise and methods to obtain monomode optical waveguides and self-sustained Mach- Zehnder structures are discussed in this work.

압전션트 댐핑을 이용한 지능패널의 다중 모드 소음 저감

This paper presents the multi-mode noise reduction of smart panels of which passive piezoelectric shunt damping is introduced. For the piezoelectric shunt damping, a passive shunt circuit composed of inductors and a load resistor is connected to the piezoelectric patch mounted on the panel structure. An electrical impedance model is introduced for the system based on the measured electrical impedance, and the criteria for maximum energy dissipation at the shunt circuit is used to find the optimal shunt parameters. For multi-mode shunt damping, the shunt circuit is modified by the introduction of a block circuit. Also the optimal location of the piezoelectric patch is studied by finite element analysis in order to cause the maximum admittance from the patch for each mode of the structure. An acoustic test is performed for the panels and a remarkable noise reduction is obtained in multiple modes of the panel structure.

Multi-mode noise analysis of cantilevers for scanning probe microscopy

A multi-mode analysis of micro-cantilever dynamics is presented. We derive the power spectral density of the cantilever displacement due to a thermal noise source and predict the cantilevers’s fundamental resonant frequency and higher harmonics. The first mode in the multi-mode model is equivalent to the traditional single-mode model. Experimental results obtained with a silicon nitride cantilever at 300 K are in excellent qualitative agreement with the multi-mode model. The multi-mode model may be used to obtain accurate values of the cantilever properties such as the elastic modulus, effective mass, thickness and moment of inertia.

Multimode-fiber technology for digital transmission

Multimode-fiber systems are presently being installed to meet some of the burgeoning demands for digital transmission in the telecommunications industry. These first-generation systems operate near 0.85-µm wavelength with laser transmitters and avalanche-photodiode receivers. Second-generation multimode systems may use simpler and more reliable LED's and p-i-n photodiodes operating near 1.3 µm, where fibers exhibit much lower loss and dispersion. This paper summarizes the state of the art of multimode-fiber digital transmission with special emphasis on emerging technologies for operation in the 1.1-1.7- µm wavelength region. Graded-index multimode fibers, lasers, LED's, photodetectors, receiver sensitivities, and noise penalties are considered. Finally, some of the requirements and challenges in applying these technologies are discussed.