- 标题
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- 实验方案
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Robust holography of the temporal wave function via second-order interference
摘要： Containing the capacity to record both amplitude and phase information of the light ?eld, holography is of great importance in science and technology. Here, we present robust holography via second-order interference, considering both single-photon states and coherent states. Temporal amplitude and phase distribution carried by a weak coherent state are reconstructed experimentally. By comparison between holography using ?rst-order interference and second-order interference, the robustness against phase noise of our method is veri?ed. Besides, information about the state can be directly retrieved, with no complex algorithm required.
关键词： single-photon states,holography,coherent states,second-order interference,phase noise
更新于2025-09-11 14:15:04
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Adaptive Subspace Method for Phase Noise Estimation in CO-OFDM Systems
摘要： In this paper, a blind phase noise estimation method for a coherent optical orthogonal frequency-division multiplexing (CO-OFDM) system is considered. Based on the subspace approach, a simple and robust method is proposed to adaptively estimate and track phase noise in CO-OFDM systems. The idea behind this novel technique is to estimate the singular vectors that correspond to the smallest singular values of the noise subspace. A weighting parameter, which is derived based on the forward–backward linear prediction technique, is subsequently constructed using the obtained singular vectors of the noise subspace to adaptively estimate the phase noise in the system. Also, a variable step size is introduced to ensure an improved performance as well as stable convergence. Simulation results are shown to demonstrate the effectiveness as well as the efficiency of the proposed algorithm, which is implemented in a polarization multiplexed CO-OFDM system stressed by polarization mode dispersion, chromatic dispersion, and other polarization-dependent losses along the fiber link.
关键词： subspace method,adaptive algorithms,CO-OFDM,phase noise estimation,OFDM
更新于2025-09-11 14:15:04
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Detection and Evaluation of Fiber Noise Induced in Ultra-Stable Environments
摘要： We investigated phase noise induced in a piece of optical fiber installed in an ultra-stable environment. The ultra-stable environments were implemented by hermetically sealing, vacuuming, temperature stabilization, vibration isolation, and acoustic shielding. Moreover, in order to detect and evaluate such small fiber noise with high sensitivity, we employed the well-known self-heterodyne technique. The most stable environment drastically reduced the phase noise induced in a 10-m fiber; the noise corresponds to Allan deviation of 7 × 10?20 at 1-s averaging time, and to 2 × 10?21 at 10000-s averaging time (measurement bandwidth: 500 Hz).
关键词： Phase noise,Laser stability,Optical fibers,Noise measurement,Optical metrology,Interferometers
更新于2025-09-10 09:29:36
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Reduction of the Phase Noise Level of Heterodynes of Modern Spectrum Analyzers Using Fundamental Frequency Images of Direct Digital Synthesizers
摘要： A hybrid frequency synthesizer is developed in which fundamental frequency images of a direct digital synthesizer are used to improve noise characteristics. It is shown that this synthesizer can generate a wide range of output frequencies with a small step size adjustment. Mathematical modeling of the noise characteristics of the synthesizer and comparison with the noise characteristics of heterodynes of modern spectrum analyzers are carried out.
关键词： spectrum analyzer,phase-locked loop,direct digital synthesizer,phase noise,heterodyne,hybrid frequency synthesizer
更新于2025-09-10 09:29:36
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Ultra Low Phase Noise 10MHz Crystal Oscillators
摘要： This paper describes the design and implementation of low phase noise 10MHz Crystal Oscillators (using SC cut crystal resonators) which are being used as part of the chain of a local oscillator for use in compact atomic clocks. The design considerations and phase noise measurements are presented. The design includes a low noise transformer coupled differential amplifier, spurious resonance rejection filter and electronically tuned phase shifter. Phase noise measurements demonstrate a performance of -122dBc to -123dBc/Hz at 1Hz and -148dBc/Hz at 10Hz offsets. The phase noise at 1Hz offset is very similar to the phase noise produced by the low noise version of a doubled 5MHz BVA resonator based oscillators (Model number 8607) previously produced by Oscilloquartz. The noise floor of the oscillators presented in this paper is around -161dBc/Hz. These designs can be used as the reference oscillator to control the timing of many modern electronics systems.
关键词： spurious resonance rejection filter,differential amplifier,SC cut crystal resonators,low phase noise,compact atomic clocks,10MHz Crystal Oscillators,electronically tuned phase shifter
更新于2025-09-10 09:29:36
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A Tunable Low-Power Oscillator Based on High-Q Lithium Niobate MEMS Resonators and 65-nm CMOS
摘要： This paper presents a comprehensive guide to co-design piezoelectric RF-micro-electromechanical system (MEMS) resonators and CMOS for enabling voltage-controlled MEMS oscillators (VCMOs) that harness the best benefits out of both platforms. The analysis, focusing on understanding different tradeoffs among the tuning range, power consumption, gain, and phase noise, is generic to any kind of piezoelectric resonators and specific for Colpitts VCMOs. As a result of this paper, the first VCMO based on the heterogeneous integration of a high-Q lithium niobate (LiNbO3) micromechanical resonator and CMOS has been demonstrated. A LiNbO3 resonator array with a series resonance at 171.1 MHz, a Q of 410, and an electromechanically coupling factor of 12.7% is adopted, while the TSMC 65-nm RF LP CMOS technology is used to implement the feedback and tuning circuitry with an active area of 220 × 70 μm2. The frequency tuning of the VCMO is achieved by programming a binary weighted digital capacitor bank and a varactor that are both connected in series to the resonator. The best measured phase noise performance of the VCMO is ?72 and ?153 dBc/Hz at 1 kHz and 10-MHz offsets from 178.23- and 175.83-MHz carriers, respectively. The VCMO consumes a dc current of 60 μA from a 1.2-V supply while realizing a tuning range of 2.4 MHz (～1.4% fractional tuning range). Such VCMOs can be applied to enable ultralow power, low phase noise, and wideband RF signal synthesis for emerging applications in Internet of Things.
关键词： RF-micro-electromechanical system (MEMS),lithium niobate (LiNbO3),phase noise,oscillator,Internet of Things (IoT)
更新于2025-09-10 09:29:36
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A Method to Improve the Imaging Quality in Dual-Wavelength Digital Holographic Microscopy
摘要： A digital hologram-optimizing method was proposed to improve the imaging quality of dual-wavelength digital holographic microscopy (DDHM) by reducing the phase noise level. In our previous work, phase noise reduction was achieved by dual-wavelength digital image-plane holographic microscopy (DDIPHM). In the optimization method in this paper, the phase noise was further reduced by enhancing the real-image term and suppressing effects of the zero-order term in the frequency spectrum of a digital hologram. Practically, the carrier frequency of the real-image term has the correspondence with interference fringes the first order intrinsic mode function (IMF1) in bidimensional empirical mode decomposition (BEMD) has similar characteristics to the grayscale values of ideal interference fringes. Therefore, with the combination of DDIPHM and BEMD, by utilizing the characteristics of IMF1, the digital hologram was optimized with purified interference fringes, enhancing the real-image term simultaneously. Finally, the validity of the proposed method was verified by experimental results on a microstep.
关键词： digital holographic microscopy,BEMD,dual-wavelength,DDIPHM,phase noise
更新于2025-09-10 09:29:36
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Tunable optoelectronic oscillator working in the Ku band
摘要： An improved tunable optoelectronic oscillator (OEO) based on a dual-parallel Mach–Zehnder (MZ) modulator embedded with a sub-MZ modulator is designed and experimentally demonstrated for Ku band applications. Single-mode oscillator operation is achieved with a single feedback loop and without any electrical filters, which improves the tunability of the proposed OEO. The microwave power expression at the output of photodetector is developed using the well-known Taylor series expansion method to calculate the electrical spectrum and accumulated dispersion (ps nm?1) of the dispersive element (linearly chirped fiber Bragg grating). Phase noise is also examined, which allows us to conclude that our proposed oscillator is suitable for optical wireless communication, radar and phase array antenna applications. Furthermore, its application as a strain and temperature sensor is investigated and it is found to have maximum strain sensitivity (Kε) of 58.75 MHz με?1 and temperature sensitivity (KT) of 1.752 GHz °C?1.
关键词： optoelectronic oscillator,fiber Bragg gratings,microwave generation,phase noise,photonic sensor
更新于2025-09-10 09:29:36
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Study on the influence of phase noise on coherent beam combined Bessel-Gaussian beam
摘要： Coherent beam combining (CBC) technology is one of the effective methods to obtain the high power laser beam, but the quality of the combined beam is significantly affected by the random phase noise among the sub-beams. In this work, a method for generating a combined Bessel-Gaussian (CBG) beam based on CBC technology is proposed. The correlation coefficient is adopted to evaluate the influence of phase noise on CBG beam including the Gaussian phase noise (GPN) and measured fiber laser phase noise (FLPN). The research results of GPN show that the spiral phase of the n-order CBG beam is unaffected by noise when the amplitude of phase noise is less than λ/5. The phase noise of fiber laser is measured, and its amplitude is around λ/10. Therefore, the spiral phase of the CBG beam is unaffected by the measured FLPN. Moreover, the resisted ability of the CBG beam against phase noise is improved efficiently through increasing the number of sub-beams.
关键词： Phase noise,Vortex beam,Coherent beam combining technology,Correlation coefficient
更新于2025-09-10 09:29:36
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Space qualified microwave source for cold atom clock operating in orbit
摘要： The space cold atom clock (CAC) suffers more degradation of frequency stability from the local oscillator noise compared with fountain clocks operating on the ground because of the larger dead time of the clock cycle. Therefore, low phase noise is required for the microwave source of the space CAC in addition to robustness, compactness, and adaptability to the space environment. This paper presents the design and measurements of a low-phase-noise space quali?ed microwave source for the cold atom clock experiment in space CAC operating in the Tiangong-2 Chinese space laboratory. At frequencies near the carrier, a phase noise level of 10?6.7 × f ?1.5 rad2/Hz ( f is the Fourier frequency) is achieved. This guarantees a frequency stability of 1.4 × 10?13 τ?1/2 (τ is the average time in seconds) for the typical space CAC operation cycle.
关键词： cold atom clock,space quali?ed,frequency stability,microwave source,phase noise
更新于2025-09-10 09:29:36