Showing papers on "Phase noise published in 2018"

Breaking the limitation of mode building time in an optoelectronic oscillator.

Abstract: An optoelectronic oscillator (OEO) is a microwave photonic system with a positive feedback loop used to create microwave oscillation with ultra-low phase noise thanks to the employment of a high-quality-factor energy storage element, such as a fiber delay line. For many applications, a frequency-tunable microwave signal or waveform, such as a linearly chirped microwave waveform (LCMW), is also needed. Due to the long characteristic time constant required for building up stable oscillation at an oscillation mode, it is impossible to generate an LCMW with a large chirp rate using a conventional frequency-tunable OEO. In this study, we propose and demonstrate a new scheme to generate a large chirp-rate LCMW based on Fourier domain mode locking technique to break the limitation of mode building time in an OEO. An LCMW with a high chirp rate of 0.34 GHz/μs and a large time-bandwidth product of 166,650 is demonstrated.

High key rate continuous-variable quantum key distribution with a real local oscillator

Abstract: Continuous-variable quantum key distribution (CVQKD) with a real local oscillator (LO) has been extensively studied recently due to its security and simplicity. In this paper, we propose a novel implementation of a high-key-rate CVQKD with a real LO. Particularly, with the help of the simultaneously generated reference pulse, the phase drift of the signal is tracked in real time and then compensated. By utilizing the time and polarization multiplexing techniques to isolate the reference pulse and controlling the intensity of it, not only the contamination from it is suppressed, but also a high accuracy of the phase compensation can be guaranteed. Besides, we employ homodyne detection on the signal to ensure the high quantum efficiency and heterodyne detection on the reference pulse to acquire the complete phase information of it. In order to suppress the excess noise, a theoretical noise model for our scheme is established. According to this model, the impact of the modulation variance and the intensity of the reference pulse are both analysed theoretically and then optimized according to the experimental data. By measuring the excess noise in the 25km optical fiber transmission system, a 3.14Mbps key rate in the asymptotic regime proves to be achievable. This work verifies the feasibility of the high-key-rate CVQKD with a real LO within the metropolitan area.

Parity-time-symmetric optoelectronic oscillator

Abstract: An optoelectronic oscillator (OEO) is a hybrid microwave and photonic system incorporating an amplified positive feedback loop to enable microwave oscillation to generate a high-frequency and low-phase noise microwave signal. The low phase noise is ensured by the high Q factor of the feedback loop enabled by the use of a long and low-loss optical fiber. However, an OEO with a long fiber loop would have a small free spectral range, leading to a large number of closely spaced oscillation modes. To ensure single-mode oscillation, an ultranarrowband optical filter must be used, but such an optical filter is hard to implement and the stability is poor. Here, we use a novel concept to achieve single-mode oscillation without using an ultranarrowband optical filter. The single-mode operation is achieved based on parity-time (PT) symmetry by using two identical feedback loops, with one having a gain and the other having a loss of the same magnitude. The operation is analyzed theoretically and verified by an experiment. Stable single-mode oscillation at an ultralow phase noise is achieved without the use of an ultranarrowband optical filter. The use of PT symmetry in an OEO overcomes the long-existing mode-selection challenge that would greatly simplify the implementation of OEOs for ultralow-phase noise microwave generation.

Ultimate waveform reproducibility of extreme-ultraviolet pulses by high-harmonic generation in quartz

Abstract: Optical waveforms of light reproducible with subcycle precision underlie applications of lasers in ultrafast spectroscopies, quantum control of matter and light-based signal processing. Nonlinear upconversion of optical pulses via high-harmonic generation in gas media extends these capabilities to the extreme ultraviolet (EUV). However, the waveform reproducibility of the generated EUV pulses in gases is inherently sensitive to intensity and phase fluctuations of the driving field. We used photoelectron interferometry to study the effects of intensity and carrier-envelope phase of an intense single-cycle optical pulse on the field waveform of EUV pulses generated in quartz nanofilms, and contrasted the results with those obtained in gas argon. The EUV waveforms generated in quartz were found to be virtually immune to the intensity and phase of the driving field, implying a non-recollisional character of the underlying emission mechanism. Waveform-sensitive photonic applications and precision measurements of fundamental processes in optics will benefit from these findings. High-harmonic generation in quartz offers immunity to the extreme-ultraviolet waveform against the intensity and phase noise of the driving laser pulse, extending precision waveform synthesis to the extreme ultraviolet.

A Low-Flicker-Noise 30-GHz Class-F 23 Oscillator in 28-nm CMOS Using Implicit Resonance and Explicit Common-Mode Return Path

Abstract: This paper presents a millimeter-wave (mmW) frequency generation stage aimed at minimizing phase noise (PN) via waveform shaping and harmonic extraction while suppressing flicker noise upconversion via proper harmonic terminations. A 2nd-harmonic resonance is assisted by a proposed embedded decoupling capacitor inside a transformer for explicit common-mode current return path. Class-F operation with 3rd-harmonic boosting and extraction techniques allow maintaining high quality factor of a 10-GHz tank at the 30-GHz frequency generation. We further propose a comprehensive quantitative analysis method of flicker noise upconversion mechanism exploiting latest insights into the flicker noise mechanisms in nanoscale short-channel transistors, and it is numerically verified against foundry models. The proposed 27.3- to 31.2-GHz oscillator is implemented in TSMC 28-nm CMOS. It achieves PN of −106 dBc/Hz at 1-MHz offset and figure-of-merit (FoM) of −184 dBc/Hz at 27.3 GHz. Its flicker phase-noise ( $1/f^{3}$ ) corner of 120 kHz is an order-of-magnitude better than currently achievable at mmW.

OSNR and nonlinear noise power estimation for optical fiber communication systems using LSTM based deep learning technique.

Abstract: The optical signal-to-noise ratio (OSNR) and fiber nonlinearity are critical factors in evaluating the performance of high-speed optical fiber communication systems. Recently, several deep learning based methods have been put forward to monitor OSNR of a fiber communication system. In this work, we propose a long short-term memory (LSTM) network based method to simultaneously estimate OSNR and nonlinear noise power caused by fiber nonlinearity. In the training step, LSTM network extracts the essential features in frequency domain of the input signal. Then, with the built model in the training step, the LSTM output the OSNR and nonlinear noise power of the signal under test. The simulation by VPI software is carried on a 5-channel long haul optical transmission system with the launched optical power of -3.0~ + 3.0dBm per channel. The results show that the test error of OSNR is less than 1.0dB with the reference OSNR from 15 to 30dB for QPSK, 16QAM and 64QAM signal. The test error of nonlinear noise power is less than 1.0dB for QPSK and 16QAM signal when the Laser linewidth is 6 KHz and 100 KHz respectively. The proposed method is a promising candidate for nonlinearity-insensitive OSNR and accurate nonlinear noise power estimation in multi-channel long haul optical fiber communication systems.

Integrated optoelectronic oscillator.

Abstract: With the rapid development of the modern communication systems, radar and wireless services, microwave signal with high-frequency, high-spectral-purity and frequency tunability as well as microwave generator with light weight, compact size, power-efficient and low cost are increasingly demanded. Integrated microwave photonics (IMWP) is regarded as a prospective way to meet these demands by hybridizing the microwave circuits and the photonics circuits on chip. In this article, we propose and experimentally demonstrate an integrated optoelectronic oscillator (IOEO). All of the devices needed in the optoelectronic oscillation loop circuit are monolithically integrated on chip within size of 5×6cm2. By tuning the injection current to 44 mA, the output frequency of the proposed IOEO is located at 7.30 GHz with phase noise value of −91 dBc/Hz@1MHz. When the injection current is increased to 65 mA, the output frequency can be changed to 8.87 GHz with phase noise value of −92 dBc/Hz@1MHz. Both of the oscillation frequency can be slightly tuned within 20 MHz around the center oscillation frequency by tuning the injection current. The method about improving the performance of IOEO is carefully discussed at the end of in this article.

Silicon Photonic Integrated Optoelectronic Oscillator for Frequency-Tunable Microwave Generation

Abstract: Photonic generation of a frequency-tunable microwave signal based on a silicon photonic integrated optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. The silicon photonic chip includes a high-speed phase modulator (PM), a thermally tunable micro-disk resonator (MDR), and a high-speed photodetector (PD). When an external light wave is injected into the chip, by a joint use of the PM, the MDR, and the PD, a bandpass microwave photonic filter (MPF) based on phase modulation and phase-modulation to intensity-modulation (PM-IM) conversion is realized. If the output microwave signal from the MPF is fed to the microwave input port of the PM with a sufficiently large gain provided by an electrical amplifier, the MPF becomes an OEO. By controlling the electrical power applied to a micro-heater, the resonance frequency of the MDR is tuned, which leads to the tuning of the MPF, and thus, the OEO oscillation frequency. In the experimental demonstration, two silicon photonic integrated OEOs using two MDRs with different micro-heaters are studied. The first OEO has a high-resistivity metallic micro-heater placed on top of the MDR, and the second OEO has a p-type doped silicon heater in the MDR. The two thermally tunable MDRs are characterized, and the performance of the MPFs based on the two MDRs is evaluated. The use of the two MPFs to implement two OEOs is performed, and their performance is evaluated in terms of frequency tunable range, phase noise, and power consumption.

A 27-GHz Quad-Core CMOS Oscillator With No Mode Ambiguity

Abstract: There is a lower bound on the size of a planar inductor below which significant $Q$ -degradation occurs. While this bound can limit the absolute performance of an $LC$ oscillator at any frequency, it is usually only encountered when designing at mm-wave and above. The classic way to mitigate the issue is through the use of NMOS-only and/or multi-core designs. Such techniques, however, are often not suitable for mm-wave commercialization; NMOS-only designs require thick-oxide devices, while multi-core designs need to be carefully controlled at startup to avoid unwanted oscillation modes. The circular geometry topology, first proposed in 2004, appears to overcome these issues, but, surprisingly, it has not yet been adapted to mm-wave frequencies. In this paper, we show how the topology is well suited to high-frequency applications. A quad-core 27-GHz $LC$ oscillator is presented that has a single high- $Q$ mode. The suppression of the three unwanted modes removes any mode ambiguity and enhances the $Q$ of the wanted mode. The design is fully complementary and, so, is compatible with the use of high $f_{T}$ thin-oxide devices. The near mm-wave prototype achieves a figure of merit of 187 dBc/Hz and a tuning range of 26%. The measured phase noise is −110 dBc/Hz@1 MHz, which is among the lowest reported for a fully complementary near mm-wave design.

Parallelized Kalman Filters for Mitigation of the Excess Phase Noise of Fast Tunable Lasers in Coherent Optical Communication Systems

Abstract: Numerical and experimental investigations are carried out on the performance of parallelized Kalman filters applied for mitigation of the excess phase noise of fast tunable lasers. Based on the characterization of the phase noise of a sampled grating distributed Bragg reflector (SG-DBR) laser, the proposed carrier phase recovery (CPR) scheme using Kalman filters is introduced. By performing simulations of data transmission with various advanced modulation formats in the presence of the excess phase noise, the Kalman filter based CPR scheme shows its ability to overcome the excess phase noise and this method is suitable for parallel processing. Then the results are further demonstrated by 12.5 Gbaud QPSK and 16-QAM transmission experiments employing the SG-DBR laser. We find that the Kalman filters have better performance than the 2nd-order phase-locked loop in parallel systems due to a better phase noise tolerance. The bit error rate performance is also examined in the whole tuning range (∼30 nm) of the tunable laser, which further proves the feasibility of the proposed scheme.

Machine learning based linear and nonlinear noise estimation

Abstract: Operators are pressured to maximize the achieved capacity over deployed links. This can be obtained by operating in the weakly nonlinear regime, requiring a precise understanding of the transmission conditions. Ideally, optical transponders should be capable of estimating the regime of operation from the received signal and feeding that information to the upper management layers to optimize the transmission characteristics; however, this estimation is challenging. This paper addresses this problem by estimating the linear and nonlinear signal-to-noise ratio (SNR) from the received signal. This estimation is performed by obtaining features of two distinct effects: nonlinear phase noise and second-order statistical moments. A small neural network is trained to estimate the SNRs from the extracted features. Over extensive simulations covering 19,800 sets of realistic fiber transmissions, we verified the accuracy of the proposed techniques. Employing both approaches simultaneously gave measured performances of 0.04 and 0.20 dB of standard error for the linear and nonlinear SNRs, respectively.

Fully Integrated Single-Chip 305–375-GHz Transceiver With On-Chip Antennas in SiGe BiCMOS

Abstract: A fully integrated single-chip transceiver (TRX) with on-chip antennas for transmitting and receiving signals within a continues frequency range from 305 to 375 GHz is presented. The radio-frequency (RF) and local oscillator signals are generated using a wideband push–push voltage-controlled oscillator, a three-stage power amplifier, and a frequency doubler. A heterodyne receiver using a fundamental mixer converts the received RF signal to an intermediate frequency (IF) signal, which drives an IF amplifier. Additionally, a divide-by-64 frequency divider is integrated to provide a low-frequency output for measurement purposes and to enable later the addition of a phase-locked loop for frequency stabilization and synthesis. A 130-nm silicon–germanium BiCMOS process with $f_t/f_{\max}$ = 250 GHz/370 GHz is used. The TRX chip is wire bonded to a printed circuit board and a TPX (Polymethylpentene) lens is placed on top of the chip for focusing the radiation. At a frequency of 343 GHz, the measurements show an effective isotropic radiated power of 18.4 dBm, a phase noise of $-$ 79 dBc/Hz@1 MHz, and an IF conversion gain of 28 dB. The obtained tuning bandwidth of 70 GHz is the highest reported so far for fully integrated TRXs.

A 0.083-mm 2 25.2-to-29.5 GHz Multi-LC-Tank Class-F 234 VCO With a 189.6-dBc/Hz FOM

Abstract: A compact multi-LC-tank Class-F234 voltage-controlled oscillator (VCO) for mm-wave applications is reported. It features an inductive multiplier inside the positive feedback loop to suppress the effective noise factor of the MOS devices. Also, by pseudo-squaring the drain-voltage waveform of the MOS devices via 2nd, 3rd, and 4th harmonic peaking, we obtain a lower impulse-sensitivity-function rms value. Prototyped in 65-nm CMOS, the VCO at 28 GHz shows a phase noise of −114.72-dBc/Hz at 1-MHz offset, while consuming 6.6 mW at 0.55 V. The tuning range is 15.7% (25.2–29.5 GHz) and the chip area is 0.083 mm2.

Low-Phase-Noise Wideband Mode-Switching Quad-Core-Coupled mm-wave VCO Using a Single-Center-Tapped Switched Inductor

Abstract: This paper describes a mode-switching quad-core-coupled millimeter-wave (mm-wave) voltage-controlled oscillator (VCO), using a single-center-tapped (SCT) switched inductor for extension of the frequency tuning range (FTR) and improvement of the phase noise (PN). The switches not only serve for in-phase coupling among the VCO cores but also can modify the equivalent tank inductance suitable for coarse frequency tuning. The frequency gaps between the multi-resonant frequencies are controlled by the common-mode (CM) inductance that is precisely set by the lithography fabrication. Together with the tiny varactors for fine frequency tuning, a wide and continuous FTR can be achieved. It is analytically shown that tiny switches (i.e., small parasitic capacitance) for mode selection are adequate to avoid bimodal oscillation, synchronize the VCO cores against resonance frequency mismatches, and prevent PN degradation. A symmetrical layout of SCT switched inductor also aids the VCO to be immune to magnetic pulling. Prototyped in 65-nm CMOS, the VCO exhibits a 16.5% FTR from 42.9 to 50.6 GHz. The PN at 46.03 GHz is −113.1 dBc/Hz at 3-MHz offset, corresponding to a figure-of-merit (FoM) of 183.6 dBc/Hz. The die size is 0.039 mm2.

Laser Phase-Noise Cancellation in Chirped-Pulse Distributed Acoustic Sensors

Abstract: Distributed acoustic sensors based on chirped-pulse phase sensitive-optical time-domain reflectometry (chirped-pulse ΦOTDR) have proven capable of performing fully distributed, single shot measurements of true strain or temperature perturbations, with no need for frequency scanning or phase detection methods. The corresponding refractive index variations in the fiber are revealed in the chirped-pulse ΦOTDR trace through a local temporal shift, which is evaluated using trace-to-trace correlations. The accuracy in the detection of this perturbation depends upon the correlation noise and the coherence of the laser source. In this paper, we theoretically and experimentally analyze the impact of the laser phase noise in chirped-pulse ΦOTDR. In particular, it is shown that the noise in the readings of strain/temperature variations scales directly with the frequency noise power spectral density of the laser. To validate the developed model, an experimental study has been performed using three lasers with different static linewidths (5 MHz, 50 kHz, and 25 kHz), i.e., with different phase noise. Besides, we present a simple technique to mitigate the effect of the laser phase noise in chirped-pulse ΦOTDR measurements. The proposed procedure enables to detect perturbations with high signal-to-noise ratio even when using relatively broad linewidth (i.e., comparatively high phase noise) lasers. Up to 17 dB increase in signal-to-noise ratio has been experimentally achieved by applying the proposed noise cancellation technique.

High-Power, Ultra-Low Noise Hybrid Lasers for Microwave Photonics and Optical Sensing

Abstract: This paper describes the design, fabrication, and excellent performance achieved with prototype hybrid lasers incorporating a high performance gain chip coupled into a fiber external cavity including a novel fiber Bragg grating (FBG) reflector. Packaged ultra-low noise (ULN) hybrid lasers operating at 1550 nm and at 1319 nm with high output power, >100 mW, and extremely low relative intensity noise (RIN) are described. Devices provide extremely stable singlemode output with high side-mode suppression ratio (SMSR), typically above 70 dB, with worst case measured RIN at microwave frequencies (1–20 GHz) being below –165 dBc/Hz. Operation of these high power, low RIN devices within an analog optical link demonstrates a Spurious Free Dynamic Range as high as 114.6 dB.Hz 2/3. In addition to high power and very low RIN, the ULN hybrid lasers provide extremely small low frequency phase noise, with Lorentzian linewidths down to 15 Hz, enabling key Microwave Photonics and Optical Sensing applications. A comparison of the phase noise and Lorentzian linewidth of ULN lasers with different FBG designs / external cavity lengths is described, demonstrating the novel hybrid approach for achieving extremely low phase noise lasers.

A quad-core 15GHz BiCMOS VCO with −124dBc/Hz phase noise at 1MHz offset, −189dBc/Hz FOM, and robust to multimode concurrent oscillations

Abstract: The relentless development of next-generation communication and radar systems sets increasingly stringent requirements on the spectral purity of local oscillators. Decreasing phase noise is crucial to support efficient modulation formats with large symbol constellations, as well as to enable innovative radar applications, e.g., anti-collision, gesture recognition, and medical imaging. To minimize phase noise, bipolar transistors offer some advantages over ultra-scaled CMOS: higher supply voltage (thus larger oscillation amplitudes), lower 1/f noise, higher-Q passives (due to higher resistivity substrate and, possibly, thicker metals), and higher f T , f max for a given technology node, which results in a cost advantage for a variety of medium-volume applications (e.g., infrastructure transceivers). For a given supply voltage, a tank showing a smaller resistance at resonance yields lower phase noise. As a result, the minimum phase noise achievable by a single voltage-controlled oscillator (VCO) is ultimately bounded by the smaller realizable inductor displaying the highest Q. To achieve significantly lower phase noise levels, bilaterally coupling N oscillators [1-3] is a viable option. However, to fully preserve the 10log(N) phase-noise advantage, while avoiding undesired multi-tone concurrent oscillations, the coupling network must be carefully designed. This work presents a quad-core bipolar VCO achieving phase noise as low as −124dBc/Hz at 1MHz offset from the 15GHz carrier, −189dBc/Hz figure-of-merit (FOM), and 16% tuning range. Insights are given into the design of the resistive network employed to couple the four oscillators, a key element in achieving the reported performance.

Pilot-multiplexed continuous-variable quantum key distribution with a real local oscillator

Abstract: We propose a pilot-multiplexed continuous-variable quantum key distribution (CVQKD) scheme based on a local local oscillator (LLO). Our scheme utilizes time-multiplexing and polarization-multiplexing techniques to dramatically isolate the quantum signal from the pilot, employs two heterodyne detectors to separately detect the signal and the pilot, and adopts a phase compensation method to almost eliminate the multifrequency phase jitter. In order to analyze the performance of our scheme, a general LLO noise model is constructed. Besides the phase noise and the modulation noise, the photon-leakage noise from the reference path and the quantization noise due to the analog-to-digital converter (ADC) are also considered, which are first analyzed in the LLO regime. Under such general noise model, our scheme has a higher key rate and longer secure distance compared with the preexisting LLO schemes. Moreover, we also conduct an experiment to verify our pilot-multiplexed scheme. Results show that it maintains a low level of the phase noise and is expected to obtain a 554-Kbps secure key rate within a 15-km distance under the finite-size effect.

Gain-Switched Optical Frequency Combs for Future Mobile Radio-Over-Fiber Millimeter-Wave Systems

Abstract: The millimeter-wave (mm-wave) frequency band has emerged as a means to overcome current radio frequency spectral limitations and represents an interesting solution to fulfill the bandwidth and networking requirements of fifth generation (5G) mobile communications and beyond. Photonic generation of these frequencies holds advantages over electronic methods in terms of cost and effective network distribution. Due to their coherent nature, optical frequency combs (OFC) are a promising solution for the efficient generation of mm-wave frequencies. The work outlined examines the use of OFCs in a mm-wave radio-over-fiber (RoF) heterodyne system with regard to the specific requirements of a 5G candidate waveform, universally filtered orthogonal frequency division multiplexing. Through experimentation and simulation, the key limitations of linewidth, effective path length difference, and relative intensity noise (RIN) are explored. Results are presented, in terms of error vector magnitude (EVM), for a wide range of system parameters highlighting important considerations to be taken in designing future mm-wave RoF systems employing OFCs. Performance of $\sim$ 5% EVM using single sideband modulation is achieved for optimized system conditions and an RIN level of $-$ 132 dB/Hz.

A Low-Integrated-Phase-Noise 27–30-GHz Injection-Locked Frequency Multiplier With an Ultra-Low-Power Frequency-Tracking Loop for mm-Wave-Band 5G Transceivers

Abstract: An ultra-low-phase-noise injection-locked frequency multiplier (ILFM) for millimeter wave (mm-wave) fifth-generation transceivers is presented. Using an ultra-low-power frequency-tracking loop (FTL), the proposed ILFM is able to correct the frequency drifts of the quadrature voltage-controlled oscillator of the ILFM in a real-time fashion. Since the FTL is monitoring the averages of phase deviations rather than detecting or sampling the instantaneous values, it requires only 600 $\mu \text{W}$ to continue to calibrate the ILFM that generates an mm-wave signal with an output frequency from 27 to 30 GHz. The proposed ILFM was fabricated in a 65-nm CMOS process. The 10-MHz phase noise of the 29.25-GHz output signal was −129.7 dBc/Hz, and its variations across temperatures and supply voltages were less than 2 dB. The integrated phase noise from 1 kHz to 100 MHz and the rms jitter were −39.1 dBc and 86 fs, respectively.

Fundamental noise dynamics in cascaded-order Brillouin lasers

Abstract: Author(s): Behunin, Ryan O; Otterstrom, Nils T; Rakich, Peter T; Gundavarapu, Sarat; Blumenthal, Daniel J | Abstract: The dynamics of cascaded-order Brillouin lasers make them ideal for applications such as rotation sensing, highly coherent optical communications, and low-noise microwave signal synthesis. Remark- ably, when implemented at the chip-scale, recent experimental studies have revealed that Brillouin lasers can operate in the fundamental linewidth regime where optomechanical and quantum noise sources dominate. To explore new opportunities for enhanced performance, we formulate a simple model to describe the physics of cascaded Brillouin lasers based on the coupled mode dynamics governed by electrostriction and the fluctuation-dissipation theorem. From this model, we obtain analytical formulas describing the steady state power evolution and accompanying noise properties, including expressions for phase noise, relative intensity noise and power spectra for beat notes of cascaded laser orders. Our analysis reveals that cascading modifies the dynamics of intermediate laser orders, yielding noise properties that differ from single-mode Brillouin lasers. These modifications lead to a Stokes order linewidth dependency on the coupled order dynamics and a broader linewidth than that predicted with previous single order theories. We also derive a simple analytical expression for the higher order beat notes that enables calculation of the Stokes linewidth based on only the relative measured powers between orders instead of absolute parameters, yielding a method to measure cascaded order linewidth as well as a prediction for sub-Hz operation. We validate our results using stochastic numerical simulations of the cascaded laser dynamics.

Blind Density-Peak-Based Modulation Format Identification for Elastic Optical Networks

Abstract: Optical modulation format identification is critical in the next generation of heterogeneous and reconfigurable optical networks. Here, we present a blind modulation format identification method by applying fast density-peak-based pattern recognition in the autonomous receiver of elastic optical networks. In this paper, we find that the different modulation format types show different energy level features which can be used as a metric to identify these modulation formats in two-dimensional Stokes plane. The proposed method does not require training symbols, and is insensitive to carrier phase noise, frequency offset as well as polarization mixing. The effectiveness is verified via numerical simulations and experiments with PDM-BPSK, PDM-QPSK, PDM-8PSK, PDM-16PSK, PDM-8QAM, and PDM-16QAM. The results show that high identification accuracy can be realized using our proposed method over wide optical signal-to-noise ratio ranges. Meanwhile, we also discuss the influence of the residual chromatic dispersion, polarization mode dispersion, and polarization dependent loss impairments to our proposed method. We believe that the simple and flexible identification method would certainly bring a great convenience to the future optical networks.

Ultra-narrow linewidth quantum dot coherent comb lasers with self-injection feedback locking

Abstract: We have used an external cavity self-injection feedback locking (SIFL) system to simultaneously reduce the optical linewidth of over 39 individual wavelength channels of an InAs/InP quantum dot (QD) coherent comb laser (CCL). Linewidth reduction from a few MHz to less than 200 kHz is observed. Measured phase noise spectra clearly indicate a significant decrease in phase noise in the frequency range above 2 kHz. The RF beating signal between two adjacent channels also shows a substantial reduction in 3-dB linewidth from 10 kHz to 300 Hz with the SIFL system, and a corresponding drop in baseline level (−27 dB to −50 dB).

Understanding Jitter and Phase Noise: A Circuits and Systems Perspective

Abstract: Gain an intuitive understanding of jitter and phase noise with this authoritative guide. Leading researchers provide expert insights on a wide range of topics, from general theory and the effects of jitter on circuits and systems, to key statistical properties and numerical techniques. Using the tools provided in this book, you will learn how and when jitter and phase noise occur, their relationship with one another, how they can degrade circuit performance, and how to mitigate their effects - all in the context of the most recent research in the field. Examine the impact of jitter in key application areas, including digital circuits and systems, data converters, wirelines, and wireless systems, and learn how to simulate it using the accompanying Matlab code. Supported by additional examples and exercises online, this is a one-stop guide for graduate students and practicing engineers interested in improving the performance of modern electronic circuits and systems.

Robust 700 MHz mode-locked Yb:fiber laser with a biased nonlinear amplifying loop mirror.

Abstract: We demonstrate a self-starting 700 MHz repetition rate Yb:fiber laser incorporated with a phase biased nonlinear amplifying loop mirror as an artificial saturable absorber. The laser delivers a maximum power of 150 mW and a pulse width of 215 fs at a pump power of 710 mW. The integration of relative intensity noise (RIN) between 10 Hz and 10 MHz results in a minimum integrated RIN of 0.015%. The phase noise of the fundamental repetition rate was also characterized at different net-cavity dispersion. Although the laser is made of nonpolarization maintaining fiber, the mode locking sustains over two weeks in open air, showing its environmental stability.

Wideband tunable optoelectronic oscillator based on a microwave photonic filter with an ultra-narrow passband

Abstract: A novel wideband tunable optoelectronic oscillator based on a microwave photonic filter (MPF) with an ultra-narrow passband is proposed and experimentally demonstrated. The single-passband MPF is realized by cascading an MPF based on stimulated Brillouin scattering and an infinite impulse response (IIR) MPF based on an active fiber recirculating delay loop. The measured full width at half-maximum bandwidth of the cascaded MPFs is 150 kHz. To the best of my knowledge, this is the first time realizing such a narrow passband in single-passband MPF. The oscillation frequency of the OEO can be tuned from 0 to 40 GHz owing to the wideband tunability of the MPF. Thanks to the ultrahigh mode selectivity of the IIR filter, the mode hopping is successfully suppressed. A stable microwave signal at 8.18 GHz is obtained with a phase noise of −113 dBc/Hz at 10 kHz, and the side mode noise is below −95 dBc/Hz. The signal-to-noise ratio exceeds 50 dB during the tuning process.

A 28-nm FD-SOI 115-fs Jitter PLL-Based LO System for 24–30-GHz Sliding-IF 5G Transceivers

Abstract: A system for local oscillator (LO) signal generation in 5G millimeter-wave (mmW) multi-antenna transceivers is presented. The system is modular with one phase locked loop (PLL) per antenna element transceiver, and a test circuit implemented in 28-nm fully depleted silicon on insulator (FD-SOI) CMOS features two such PLLs and a 491.52 MHz crystal oscillator (XO) generating a common frequency reference. A fractional-N architecture is employed to achieve high-frequency resolution, and the quantization noise is reduced using a novel frequency divider, which achieves full integer resolution while still using a pre-scaler. The system covers the 3rd Generation Partnership Project (3GPP) bands n257 and n258, achieved by a digital coarse tuning of the voltage-controlled oscillator (VCO). The chip area of each PLL is 0.11 mm2, and 0.029 mm2 for the XO. The total power consumption of the system is 35 mW, where each PLL consumes 15.4 mW and the XO consumes 0.84 mW. The total rms jitter from 20-kHz to 500-MHz offset for a 26-GHz carrier is just 115 fs, corresponding to an FOM $_{\vphantom {R_{j}}j}$ of −244 dB, which is the best reported figure for a fractional-N PLL above 15 GHz. The error-vector magnitude (EVM) due to phase noise is −34.6 dBc using an orthogonal frequency-division multiplexing (OFDM) signal with 120-kHz sub-carrier spacing, sufficient to support 256 QAM.

Self-Interference Cancellation With Nonlinearity and Phase-Noise Suppression in Full-Duplex Systems

Abstract: This paper addresses the self-interference (SI) cancellation for full-duplex operation in the presence of imperfect radio-frequency (RF) components In particular, we develop a new scheme to jointly estimate and cancel the in-phase/quadrature mixer imbalance, power amplifier nonlinearities, up-/down-conversion phase noise, and the SI channel First, we develop a detailed baseband model that captures the most significant transceiver RF imperfections, for both separate- and common-oscillator structures used in the up- and down-conversions Then, a basis expansion model is derived to approximate the time-varying phase noise and to transform the problem of estimating the time-varying phase noise into the estimation of a set of time-invariant coefficients Subsequently, the likelihood function is derived in the presence of the unknown intended signal to formulate the joint estimation of the intended channel, SI channel, nonlinear impairments, and phase noise, under the maximum likelihood (ML) criterion An iterative procedure is developed to find the ML estimate of the different parameters based on the known transmitted data, the known pilot symbols, and the statistics of the unknown intended signal received from the intended transmitter The full use of the received signal significantly reduces the required number of pilot symbols as compared to training-based techniques We consider the two pilot-insertion structures used in LTE for the frequency-multiplexed pilots and the time-multiplexed pilots Simulation results indicate that the proposed ML algorithms can offer a superior SI-cancellation performance with the resulting intended-signal-to-SI-and-noise ratio very close to the intended-signal-to-noise ratio

Wideband Dual-Injection Path Self-Interference Cancellation Architecture for Full-Duplex Transceivers

Abstract: A transceiver front end including a dual-injection path self-interference (SI) cancellation architecture is proposed for use in wideband full-duplex networks. The SI cancellation circuitry is implemented using: 1) one feedforward cancellation path containing a five-tap analog adaptive finite-impulse response (FIR) filter between the transmitter (TX) output and the receiver (RX) input; 2) a second baseband (BB) cancellation path containing a 14-tap low-frequency FIR filter with a point of injection at the RX BB output; 3) a phase noise cancellation method that suppresses the reciprocal mixing products associated with the downconversion in the BB cancellation path for the TX SI signal; and 4) an integrated noise cancelling power amplifier (PA). A prototype of 40-nm TSMC device was fabricated, which demonstrates more than 50-dB SI cancellation over 42-MHz bandwidth and a 10-dB attenuation of TX SI phase noise in the RX signal path. The two cancelling filters dissipate 11.5 mW, with a measured $P_{\mathrm {-1\,dB}}$ and IIP3 of 27/26.5 and 36/34.5 dBm, respectively. The RX noise figure is degraded by less than 1.55 dB, when both cancellers are enabled. The PA has a measured output of $P_{\mathrm {-1\,dB}}/P_{\mathrm {sat}}$ of 25.1/26.5 dBm, respectively. The total chip die area is 3.5 mm2 with an overall transceiver power consumption of 49 mW, excluding the integrated PA.

Generation of Linear Frequency-Modulated Waveforms by a Frequency-Sweeping Optoelectronic Oscillator

Abstract: In this paper, a simple scheme for linear frequency-modulated (LFM) waveform generation based on a frequency-sweeping optoelectronic oscillator is proposed and demonstrated. The OEO is built up with an optically injected semiconductor laser and the oscillation frequency can be tuned by adjusting the optical injection strength. By applying an injection strength controller in the OEO for rapid frequency sweeping, an LFM microwave waveform can be generated. When the sweep period of the output frequency matches with the round-trip time of the OEO cavity, signal quality of the generated LFM waveform can be significantly enhanced by the high Q optoelectronic oscillation. In the experiment, an LFM signal with a bandwidth as large as 7 GHz, a chirp rate reaching 0.18 GHz/ns, and a time-bandwidth product (TBWP) up to 2804.2 is generated. The corresponding electrical spectrum is a frequency comb with a contrast as high as 47 dB. Based on this system, an improved scheme for extending the frequency and bandwidth of the generated LFM signal is proposed by employing a polarization modulator to implement microwave photonic frequency multiplication. With this method, an LFM waveform with a TBWP as large as 13839.1 (bandwidth 15.6 GHz; temporal period 887.12 ns) is obtained.