In this paper, we propose a Rayleigh backscattering (RB) noise mitigation scheme based on the use of real-time heterodyne receiver for loop-back wavelength division multiplexing passive optical network (WDM-PON). Heterodyne detection has been utilized to increase the upstream receiver sensitivity, while an electro-absorption modulator (EAM) is used to simultaneously turn heterodyning bipolar signal into single polar signal and mitigate accumulated carrier RB noise. With the help of the nonlinear negative-slope transfer function of EAM, low frequency interference noise is suppressed successfully. RB noise mitigation performance is studied over 45-km single mode fiber (SMF) transmission, and the optical-signal-to-Rayleigh-noise-ratio (OSRNR) is reduced to 15.6 dB, when bias voltage of EAM is at -4 V. Through utilizing this real-time heterodyne receiver in single fiber loop-back structure, upstream error free transmission is realized with receiver sensitivity of -25 dBm.
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http://dx.doi.org/10.1364/OE.22.022673 | DOI Listing |
Rev Sci Instrum
November 2024
Department of Electrical and Computer Engineering, Tufts University, 161 College Avenue, Medford, Massachusetts 02155, USA.
Real-time and non-invasive measurements of tissue concentrations of oxyhemoglobin (HbO2) and deoxyhemoglobin (HbR) are invaluable for research and clinical use. Frequency-domain near-infrared spectroscopy (FD-NIRS) enables non-invasive measurement of these chromophore concentrations in human tissue. We present a small form factor, dual-wavelength, miniaturized FD-NIRS instrument for absolute optical measurements, built around a custom application-specific integrated circuit and a dual-slope/self-calibrating (DS/SC) probe.
View Article and Find Full Text PDFSci Rep
September 2024
Institut für Experimentalphysik, Universität Hamburg, 22761, Hamburg, Germany.
Compact laser interferometers with large dynamic range are one of the core emerging tools to improve low frequency performance in gravitational wave detectors by providing local displacement sensing with sub 1 precision. Strong sinusoidal frequency modulations are used in such laser interferometers to create heterodyne-like photodetector signals from which the phase and other parameters, such as the absolute distance, can be extracted. The nested sinusoidal function in such signals is a challenge for the real-time parameter estimation in low-noise applications.
View Article and Find Full Text PDFSensors (Basel)
June 2024
Department of Electrical and Electronic Engineering, Mokwon University, 88 Doanbuk-ro, Seo-gu, Daejeon 35349, Republic of Korea.
This paper introduces the novel design and implementation of a low-power wireless monitoring system designed for nuclear power plants, aiming to enhance safety and operational efficiency. By utilizing advanced signal-processing techniques and energy-efficient technologies, the system supports real-time, continuous monitoring without the need for frequent battery replacements. This addresses the high costs and risks associated with traditional wired monitoring methods.
View Article and Find Full Text PDFAs a stochastic perturbation, the inter-core crosstalk (IC-XT) severely distorts the signal in multi-core fibers (MCF), especially for long-haul transmission. How to quickly measure and monitor the IC-XT online for an MCF-based space division multiplexing (SDM) system is of special importance. In this paper, we introduce the technology of auxiliary management and control channel (AMCC) to online monitor the IC-XT of MCF, in which the unique advantage of low-frequency auxiliary management and control signal is fully utilized with the limited influence on high-speed data transmission.
View Article and Find Full Text PDFSpectrochim Acta A Mol Biomol Spectrosc
May 2024
Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun, Jilin 130033, China; University of Chinese Academy of Sciences, Beijing 100049, China; National Engineering Research Center for Diffraction Gratings Manufacturing and Application, Changchun, Jilin 130033, China.
Microplastic pollution has become a global environmental problem that cannot be ignored. Raman spectroscopy has been widely used for microplastics detection because it can be performed in real-time and is non-destructive. Conventional detection techniques have had weak signals and low signal-to-noise ratios (SNR).
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