Phase Noise Research Articles

A Low-jitter Charge-pumped PLL for LiDAR Detectors

A low-jitter charge-pumped phase-locked loop (CPPLL) with four-stage differential delay units is implemented in 180 nm standard CMOS technology. Not only a current-steering technique is adopted to eliminate charge injection and clock feed-through effects, but also a frequency divider with a retiming structure is used to ensure the high accuracy of the system feedback loop. The voltage-controlled oscillator adopts a gated-ring structure to achieve a stable and controllable clock. The prototype of the CPPLL occupies 0.184 , and results reveal that when the reference clock is 50 MHz, the output frequency is locked at 800 MHz accurately. The phase noise is as low as -140 dBc/Hz @1 MHz, with a peak-to-peak jitter of 4.36 ps. Meanwhile, an ultra-low root-mean-square (RMS) jitter of 0.161 ps is obtained. At the output spectrum of 800 MHz, the reference spur is merely -72 dBc. These results highlight the CPPLL's outstanding performance in phase noise, jitter, and stability, making it well-suited for high-precision integrated LiDAR.

Low-noise high-power dual-frequency MOPA laser with an NPRO seed

Dual-frequency lasers are significant in fields like photonic microwave sources, optical carrier lidar, and heterodyne laser interferometry. Increasing the power of dual-frequency lasers is crucial for expanding their applications. However, achieving high-power dual-frequency lasers with low noise remains a challenge. In this work, we demonstrate a low-noise, high-power dual-frequency laser in a master-oscillator-power-amplifier (MOPA) configuration. In this setup, a dual-frequency monolithic nonplanar-ring-oscillator (NPRO) serves as the seed, and an ytterbium-doped fiber amplifier (YDFA) is used to boost the optical power. The MOPA laser achieves a dual-frequency laser power up to 5 W at 1064 nm and maintains the phase noise of the beat signal at 5.78 GHz as low as -116.6 dBc/Hz at 10 kHz and -152.3 dBc/Hz at 10 MHz. To quantify the additional phase noise to the beat signal from the fiber amplifier, we established a theoretical model, which reveals that this noise is negligible in our system. We anticipate that our model can be extended to analyze the phase noises of other dual-frequency laser systems, and our MOPA laser will enhance the capabilities of dual-frequency laser applications in industrial, airborne, and spaceborne environments.

Optoelectronic Oscillators: Progress from Classical Designs to Integrated Systems

Optoelectronic oscillators (OEOs) have emerged as indispensable tools for generating low-phase-noise microwave and millimeter-wave signals, which are critical for a variety of high-performance applications. These include radar systems, satellite links, electronic warfare, and advanced instrumentation. The ability of OEOs to produce signals with exceptionally low phase noise makes them ideal for scenarios demanding high signal purity and stability. In radar systems, low-phase-noise signals enhance target detection accuracy and resolution, while, in communication networks, such signals enable higher data throughput and improved signal integrity over extended distances. Furthermore, OEOs play a pivotal role in precision instrumentation, where even minor noise can compromise the performance of sensitive equipment. This review examines the progress in OEO technology, transitioning from classical designs relying on long optical fiber delay lines to modern integrated systems that leverage photonic integration for compact, efficient, and tunable solutions. Key advancements, including classical setups, hybrid designs, and integrated configurations, are discussed, with a focus on their performance improvements in phase noise, side-mode suppression ratio (SMSR), and frequency tunability. A 20-GHz oscillation with an SMSR as high as 70 dB has been achieved using a classical dual-loop configuration. A 9.867-GHz frequency with a phase noise of −142.5 dBc/Hz @ 10 kHz offset has also been generated in a parity–time-symmetric OEO. Additionally, integrated OEOs based on silicon photonic microring resonators have achieved an ultra-wideband tunable frequency from 3 GHz to 42.5 GHz, with phase noise as low as −93 dBc/Hz at a 10 kHz offset. The challenges in achieving fully integrated OEOs, particularly concerning the stability and phase noise at higher frequencies, are also explored. This paper provides a comprehensive overview of the state of the art in OEO technology, highlighting future directions and potential applications.

Leveraging autoencoder for laser phase noise compensation in coherent optical OFDM systems

Leveraging autoencoder for laser phase noise compensation in coherent optical OFDM systems

Synergizing the low-phase noise characteristics of a dielectric resonator oscillator and a bichromatic Brillouin laser oscillator.

We introduce a method that synergistically combines the distinct phase noise profiles of a dielectric resonator oscillator (DRO) and bichromatic Brillouin laser oscillator (BBLO), for high spectral purity microwave generation. Typically, free-running DROs exhibit high-phase noise at low-frequency offsets but ultra-low-phase noise at high offsets. In contrast, BBLOs based on photonic devices demonstrate very low-phase noise at low offsets, yet they experience increased phase noise at higher offsets due to photodetector shot noise. By locking the DRO to a frequency-matching BBLO, our experiment combines the merits of both oscillators and generates X-band microwave with exceptional phase noise across the entire frequency offset range, reaching -93 dBc/Hz at 100 Hz offset and -171 dBc/Hz at 10 MHz offset.

Research on LD-pumped single-frequency laser based on twisted-mode-cavity and RVBG

Abstract Single-frequency lasers have the advantages of good spectral purity, high peak spectral density, long coherence distance and low phase noise. They are widely used in fields such as laser spectroscopy, laser lidar, sodium guide stars, coherent optical communication and high-resolution measurement. We designed an all-solid-state single-frequency laser based on twisted-mode-cavity (TMC) structure and used a reflective volume Bragg grating (RVBG) to replace the ordinary output mirror. Through the composite mode selection effect of the twisted-mode-cavity and RVBG, the occurrence of multi-longitudinal mode oscillation is eliminated successfully, and precise optical frequency selection is achieved. When the pump power reached 88.0 W, the output power was 1.6 W, allowing for stable single-frequency laser operation at 1064.44 nm, with an output laser linewidth of 9.77 × 10−3 pm, the corresponding slope efficiency was 10.00%, and the light-to-light conversion efficiency was 1.82%. The power instability was less than 4.44% and the beam quality factor were M x 2 = 1.35 , M y 2 = 1.38 . Experimental results show that compared with using a RVBG or twisted-mode-cavity individually, the combination of the two methods can significantly compress the laser linewidth and achieve single-frequency laser output.

Robust suppression of high-frequency laser phase noise by adaptive Pound-Drever-Hall feedforward

Robust suppression of high-frequency laser phase noise by adaptive Pound-Drever-Hall feedforward

GAN augmented phase noise modeling of PLL for use in automated testing

ABSTRACT Phase noise measurement of Phase Locked Loop (PLL) in automated test equipment (ATE) is expensive and time-consuming. Indirect phase noise measurement relies on a few correlated low-cost measurements called signatures obtained from specific nodes of the PLL. A regression model using these signatures is learned during the design phase for phase noise estimation. Extraction of these signatures and phase noise performance in PLL requires significant simulation time, raising non-recurring design costs and computer aided design (CAD) tool usage costs. In this work, a new methodology for indirect phase noise measurement is developed where Generative Adversarial Network (GAN), a deep learning framework, has been used for generating a substantial amount of model-driven synthetic signatures that are strongly correlated to simulation-driven real signatures. These model-driven signatures are then used to construct a regression model for phase noise prediction. The GAN model efficacy is verified by comparing the prediction accuracy of the simulation-driven signature-based model with the GAN-augmented signature-based regression model.

Design and Analysis of High Speed Phase Frequency Detector with Zero Dead Zone in PLL

This paper presents a proposed phase frequency detector(PFD) designed by using the 180-nm CMOS process. Adding an extra buffer to the typical D flipflop-based PFD solves the dead zone(DZ) problem, however the frequency of operation is reduced. The proposed design of PFD eliminates the dead zone(DZ) and reduces the blind zone(BZ) significantly by developing the independent relationship between the blind zone(BZ) and the dead zone(DZ). Moreover, the proposed architecture helps to increase the operating frequency compared to the conventional architecture. The reset time of the proposed PFD requires one NAND gate, one AND gate, and an OR gate, whereas conventional PFDs require one D flipflop, one AND gate, and a delay element, which limits the frequency of operation in conventional architecture. The proposed architecture achieves 135 ps of reset time and 95 ps of delay time at the maximum operating frequency of 4.3 GHz. The phase noise of the proposed architecture is −143.2 dBc/Hz with 1 MHz offset at 4 GHz. The PLL is designed using the proposed PFD architecture with an reference frequency of 4 GHz and the phase noise is −110 dBc/Hz at a 1.5 MHz offset frequency.

Improved Adaptive Kalman Filter (IAKF) technique For Phase Noise Compensation using Rotation based channel scheme for Millimeter-wave MIMO-NOMA systems

Improved Adaptive Kalman Filter (IAKF) technique For Phase Noise Compensation using Rotation based channel scheme for Millimeter-wave MIMO-NOMA systems

Narrow Linewidth All-Optical Microwave Oscillator Based on Torsional Radial Acoustic Modes of Single-Mode Fiber.

A Hz level narrow linewidth all-optical microwave oscillator based on the torsional radial acoustic modes (TR2,m) of a single-mode fiber (SMF) is proposed and validated. The all-optical microwave oscillator consists of a 20 km SMF main ring cavity and a 5 km SMF sub ring cavity. The main ring cavity provides forward stimulated Brillouin scattering gain and utilizes a nonlinear polarization rotation effect to achieve TR2,7 mode locking. By combining the sub ring cavity with the main ring cavity and utilizing the Vernier effect, the TR2,7 mode microwave photonic single longitudinal mode (SLM) output can be ensured. Meanwhile, the 6.281 Hz narrow linewidth of the TR2,7 mode is achieved by reducing the intrinsic linewidth of the passive resonant cavity. The acoustic mode suppression ratio and side mode suppression ratio of the TR2,7 mode were 43 dB and 54 dB, respectively. The power and frequency fluctuations of within 40 min were approximately ±0.49 dB and ±0.187 kHz, indicating good stability. At a frequency offset of 10 kHz, the TR2,7 mode had a low phase noise value of -110 dBc/Hz. This solution can be used in various fields, such as high-precision radar detection, long-distance optical communication, and high-performance fiber optic sensing.

High-fidelity and adaptive forward-phase-based vibration sensing using a Wiener filter in DSCM systems under commercial ECLs.

In this Letter, we propose and experimentally validate a high-fidelity and adaptive forward-phase-based vibration sensing using a Wiener filter (WF). In commercial coherent digital subcarrier multiplexing (DSCM) systems under external cavity lasers (ECLs), frequency-domain pilot tones (FPTs) in subcarrier intervals are employed for dynamic frequency offset estimation (FOE), carrier phase estimation (CPE), and polarization demultiplexing. The phase estimated by the CPE module is processed with the WF to achieve high-fidelity extraction of the vibration-induced phase. Compared to traditional bandpass filter (BPF)-based phase extraction, the WF method effectively suppresses sensing background noise caused by laser phase noise, improving sensing signal-to-noise ratio (SSNR). Furthermore, without knowing vibration frequency and waveform information, the WF method can adaptively detect various vibration waveforms, including amplitude-modulated continuous wave (AMCW) and frequency-modulated continuous wave (FMCW). In experiments, for 10 kHz sinusoidal vibration detection, the WF method demonstrated an 8 dB SSNR improvement compared to the BPF method. The experiments further verified that both AMCW and FMCW vibrations can be detected adaptively with the WF method using the same filter parameters as for sinusoidal vibrations.

Resonant Young's Slit Interferometer for Sensitive Detection of Low-Molecular-Weight Biomarkers.

The detection of low-molecular-weight biomarkers is essential for diagnosing and managing various diseases, including neurodegenerative conditions such as Alzheimer's disease. A biomarker's low molecular weight is a challenge for label-free optical modalities, as the phase change they detect is directly proportional to the mass bound on the sensor's surface. To address this challenge, we used a resonant Young's slit interferometer geometry and implemented several innovations, such as phase noise matching and optimisation of the fringe spacing, to maximise the signal-to-noise ratio. As a result, we achieved a limit of detection of 2.9 × 10-6 refractive index units (RIU). We validated our sensor's low molecular weight capability by demonstrating the detection of Aβ-42, a 4.5 kDa peptide indicative of Alzheimer's disease, and reached the clinically relevant pg/mL regime. This system builds on the guided mode resonance modality we previously showed to be compatible with handheld operation using low-cost components. We expect this development will have far-reaching applications beyond Aβ-42 and become a workhorse tool for the label-free detection of low-molecular-weight biomarkers across a range of disease types.

Optoelectronic Oscillator Based Microwave Frequency Downconverter With Low Phase Noise and High Conversion Efficiency

Optoelectronic Oscillator Based Microwave Frequency Downconverter With Low Phase Noise and High Conversion Efficiency

Theoretical and experimental analysis of phase noise in semiconductor lasers biased below threshold

Abstract We report a theoretical and experimental study of phase noise in semiconductor lasers when the bias current is below the threshold value. The theoretical study is performed by using two types of rate equations, with additive and multiplicative noise terms. We find the conditions for which the evolution in those rate equations can be described by 1-dimensional and two dimensional Brownian motions, respectively. The main statistical differences between the additive and multiplicative noise models are then illustrated by using the simplified Brownian motion models. Additive and multiplicative noise models predictions are compared with measurements of the phase noise with a coherent receiver using a 90o optical hybrid. We develop a novel method to extract the phase noise directly from our measurements, that in contrast to the usual direct method is not based on the analysis of the phase noise difference. The method permits a direct visualization of the phase noise trajectories and a calculation of the averages and the distribution that is valid in the short-time limit. Our results are in very good agreement with the results obtained with the method based on the phase noise difference. Our experimental results show that the variance of the phase noise grows linearly in time and has Gaussian statistics, supporting the modelization of the phase noise statistics with the additive noise model.

Feasibility of phase stabilization for satellite-mediated twin-field quantum key distribution.

Quantum key distribution (QKD) is critical for future proofed secure communication. Satellites will be necessary to mediate QKD on a global scale. The limitations of the existing quantum memory and repeater technology mean that twin-field QKD (TF-QKD) provides the most feasible near-term solution to perform QKD with an untrusted satellite. However, the TF-QKD requires links between ground stations and satellites to be phase stable. We show that phase stabilization of the links to LEO and MEO satellites is feasible in spite of phase noise due to atmospheric turbulence, laser instability, and path length asymmetry while only incurring a quantum bit error rate (QBER) penalty of less than 1.5%. These results are also applicable to future untrusted satellite networks employing precisely synchronized quantum memories or quantum repeaters.

A Noise-Tolerant Carrier Phase Recovery Method for Inter-Satellite Coherent Optical Communications

Coherent free-space optical communication offers significant advantages in terms of communication capacity, making it particularly suitable for high-speed inter-satellite transmission within satellite communication networks. Nonetheless, the presence of Doppler frequency offset (FO) and phase noise (PN) associated with lasers adversely affects the bit error rate (BER) performance of these communication systems. Conventional methods for FO and phase estimation are usually hindered by high computational demands and phase cycle slips, especially in environments characterized by elevated channel noise. To address these challenges, a noise-tolerant method is proposed to facilitate accurate carrier phase recovery (CPR) with reduced complexity. This method merges a second-order feedback loop and a feedforward stage to achieve accurate estimation. The simulation results indicate that the proposed method surpasses traditional methods in terms of noise tolerance and resource efficiency. Particularly, the BER of the proposed method can be decreased to 6.7×10−3 at a signal-to-noise ratio (SNR) of 4.5 dB, in contrast to a BER of 0.25 for the traditional method. Additionally, the resource consumption of the proposed method can be decreased by 64% under equivalent conditions. Furthermore, the experimental results reveal that the phase estimation error and BER for the proposed method are 2.1×10−4 and 7.5×10−4, respectively, when the received power is −41 dBm. These values are significantly lower than those achieved with traditional methods, which obtain errors of 1.85×10−3 and a BER of 0.48, respectively.

Optoelectronic oscillator system with low phase noise based on a microwave multiplexor: evaluation of construction possibilities

The paper is dedicated to the current issue of microwave photonics: the development of optoelectronic oscillators for ultra-high frequency signals. The interest in creating such oscillators is largely driven by the possibility of obtaining signals with low levels of phase noise. The use of multiplexers as fi lters in optoelectronic oscillators opens up new possibilities in building optoelectronic systems for generating ultra-high frequency signals at different frequencies. This implementation of the optoelectronic generator allows for discrete regulation of the frequency of the generated signal, or generating the signal simultaneously at multiple specifi ed frequencies. In the investigated system, phase noises were measured: less than 100 dBc/Hz at 1 kHz offset from the carrier frequency and less than 130 dBc/Hz at 10 kHz offset from the carrier frequency. The obtained results confirm the potential use of multiplexers as bandpass filters, which is important for the development and optimization of optoelectronic oscillators

Phase Noise and Dynamic Range in Radar Arrays

Phase Noise and Dynamic Range in Radar Arrays

Development of a novel high-frequency reciprocal structure fiber optical pulsed current sensor.

A novel all-fiber optic current sensor (FOCS) is designed specifically for the measurement of large transient currents based on the Faraday effect. A reciprocal symmetric structure is incorporated into the optical sensing loop, and the current dependent phase demodulation is achieved by using a passive optical fiber coupler and the homodyne detection scheme. This design offers several advantages, including structural simplicity, high voltage insulation, low noise, high linearity, and excellent frequency response, and is highly suitable for use in any system of high-voltage, high-power, and high-frequency in nature. A current source based on fast capacitor discharge is used for the bench-test of the FOCS system, and several laser sources with different wavelengths and linewidths have been used to test the FOCS performance. Experimental results show that the phase noise of the laser is independent of both wavelength and linewidth. The sensitivity of the FOCS system has been calibrated against a commercial Rogowski current sensor. This FOCS offers precise and flexible high-current pulse measurements with a measured phase noise of 1.4 × 10-3rad, using a 1550nm laser with a 1kHz linewidth. The fully reciprocal sensing loop ensures that the phase noise remains unchanged as the loop length increases. These features make the FOCS a robust and adaptable tool for high-precision current sensing in challenging environments. Finally, the FOCS system has consistently demonstrated its superior and stable performance in terms of high-frequency response and low noise with minimal dependence on the laser parameters.