Single-sideband Phase Noise Research Articles

Wideband Tunable Frequency-Doubling Optoelectronic Oscillator Using a Polarization Modulator and an Optical Bandpass Filter**Supported by the National Natural Science Foundation of China under Grant No 61675196, the National Basic Research Program of China under Grant No 2014CB340102, the National High-Tech Research and Development Program of China under Grant No 2015AA016903, and the Open Research of Beijing University of Posts and

A wideband tunable frequency-doubling optoelectronic oscillator (FD-OEO) is proposed and experimentally demonstrated based on a polarization modulator and an optical bandpass filter (OBPF). The central frequency of the correspondingly fundamental OEO could be adjusted by tuning the bandwidth and central frequency of the OBPF, which could also be regarded as a photonic-assisted tunable microwave filter. The frequency tuning range of the FD-OEO covers from 9.5 to 32.8 GHz, and the single sideband phase noise of the fundamental signal is lower than −100 dBc/Hz at an offset of 10 kHz. Moreover, the frequency stability of the generated signal is investigated by measuring its Allan deviation. The Allan deviation of the generated fundamental signal at 10 GHz is 2.39×10−9.

Tunable Low-Jitter Low-Drift Spurious-Free Transposed-Frequency Optoelectronic Oscillator

We propose and theoretically and experimentally demonstrate a novel tunable spurious-free single-loop optoelectronic oscillator (OEO) with low drift and low-phase noise. In the proposed transposed-frequency OEO (TF-OEO), a nonreciprocal bias unit and an optical phase modulator in a fiber Sagnac interferometer function jointly as an intrinsically drift-free intensity modulator, which improves the long-term drift. Besides, a transposed-frequency low-noise filtered amplifier is used which replaces the conventional radio frequency (RF) bandpass filter (BPF) and RF amplifier with an intermediate frequency (IF) BPF, an ultralow phase noise IF amplifier, and a tunable local oscillator, to attain frequency tuning and single-frequency selection with ultralow phase noise at the same time. The quality of the generated microwave signals is theoretically investigated and verified by experiments. Preliminary phase noise, frequency stability, spurious noise levels, and frequency tunability of the photonically generated microwave signal are also investigated. A microwave signal with a frequency tunable range of 15 MHz around 10.833 GHz is generated with no spurs. The generated microwave oscillation has a single-sideband phase noise of −120 dBc/Hz at 10 kHz offset from 10.833 GHz carrier, with 36 fs RMS timing jitter integrated from 1 kHz to 10 MHz. Long-term frequency stability measurements show ±0.05 ppm maximum fractional frequency deviation over 60 h, which is mainly limited by drift of the fiber delay line. The measured results show the long-term frequency stability (in terms of overlapping Allan deviation) within $8.7\times 10^{-9}$ at 1000 s averaging time.

Low-Drift Optoelectronic Oscillator Based on a Phase Modulator in a Sagnac Loop

A low-drift optoelectronic oscillator (OEO) is developed and experimentally shown. In the proposed OEO, a fiber Sagnac interferometer, including an optical phase modulator (PM) and a nonreciprocal bias unit, functions as an intrinsically drift-free intensity modulator. The phase noise of the proposed OEO is modeled in phase space, which is verified by experiments. Phase noise and frequency stability of the photonically generated microwave signals are measured. The single-sideband phase noise of the generated microwave signal is −106.6 dBc/Hz at 10-kHz offset from the 10.833-GHz carrier, with 120-fs rms timing jitter integrated from 1 kHz to 10 MHz. Frequency drift measurements show ±0.85-ppm maximum fractional frequency deviation over 35 h, mainly caused by drift of the fiber delay line.

Wideband tunable optoelectronic oscillator based on the deamplification of stimulated Brillouin scattering.

A wideband tunable optoelectronic oscillator (OEO) based on the deamplification of stimulated Brillouin scattering (SBS) is proposed and experimentally demonstrated. A tunable single passband microwave photonic filter (MPF) utilizing phase modulation and SBS deamplification is used to realize the tunability of the OEO. Theoretical analysis of the MPF and phase noise performance of the OEO are presented. The frequency response of the MPF is determined by the + 1st sideband attenuation due to SBS deamplification and phase shift difference between the two sidebands due to chromatic dispersion and SBS. The close-in (< 1 MHz) phase noise of the proposed OEO is shown to be dominated by the laser frequency noise via phase shift of SBS. The conversion of the laser frequency noise to the close-in phase noise of the proposed OEO is effectively reduced compared with the OEO based on amplification by SBS. Tunable 7 to 40 GHz signals are experimentally obtained. The single-sideband (SSB) phase noise at 10 kHz offset is -128 dBc/Hz for 10.30 GHz signal. Compared with the OEO based on SBS amplification, the proposed OEO can achieve a phase noise performance improvement beyond 20 dB at 10 kHz offset. The maximum frequency and power drifts at 10.69 GHz are within 1 ppm and 1.4 dB during 1000 seconds, respectively. To achieve better close-in phase noise performance, lower frequency noise laser and higher pump power are preferred. The experimental results agree well with the theoretical models.

Self-stabilization of an optical frequency comb using a short-path-length interferometer.

We stabilized the repetition rate of an optical frequency comb using a self-referenced phase-locked loop. The phase-locked loop generated its error signal with a fiber-optic delay-line interferometer that had a path-length difference of 8 m. We used the stabilized repetition rate to generate a 10 GHz signal with a single-sideband phase noise that was limited by environmental noise to -120 dBc/Hz at an offset frequency of 1 kHz. Modeling results indicate that thermoconductive noise sets a fundamental phase noise limit for an 8 m interferometer of -152 dBc/Hz at a 1 kHz offset frequency. The short length of the interferometer indicates that it could be realized as a photonic integrated circuit, which may lead to a chip-scale stabilized optical frequency comb with an ultralow-phase-noise repetition rate.

Simple optical frequency comb generation using a passively mode-locked quantum dot laser

A simple and quasi-tunable optical frequency comb (OFC) generator is proposed and experimentally demonstrated using a C-band passively Fabry-Pérot quantum dot mode-locked laser and a dual-driven LiNbO3 Mach–Zehnder modulator. A 16-nm bandwidth OFC with 81, 58 and 30 comb lines at frequency interval of 23.3GHz, 35GHz and 70GHz respectively is obtained experimentally. Measured average optical signal to noise ratio of 10-dB bandwidth OFCs is 36.3dB, 38.5dB and 40.8dB at frequency interval of 23.3GHz, 35GHz and 70GHz, respectively. Besides, single-sideband phase noise of the 23.3GHz and 35GHz frequency comb is −110 dBc/Hz and −102 dBc/Hz at an offset of 1kHz, respectively. RF linewidth of the 23.3GHz and 35GHz OFC is about from 275Hz to 289Hz. This is considered a very simple OFC generator with a broadband and seamless spectrum.

Simple and seamless broadband optical frequency comb generation using an InAs/InP quantum dot laser.

A simple and seamless broadband optical frequency comb (OFC) generator is proposed and experimentally demonstrated using a Fabry-Perot quantum dot mode-locked laser combined with a dual-driven LiNbO₃ Mach-Zehnder modulator driven by a low-power radio frequency (RF) signal. It is experimentally demonstrated that the 10-dB seamless bandwidth of the OFC is 8.2 nm (1.02 THz), which has 62 and 40 comb lines for frequency intervals of 16.56 GHz and 24.84 GHz, respectively. The single-sideband phase noise is as low as -112 and -108 dBc/Hz at an offset of 10 kHz, respectively, for the photodetector-converted 16.56 and 24.84 GHz frequency carriers. Correspondingly, the RF linewidths of the 16.56 GHz and 24.84 GHz carriers are about 251 Hz-263 Hz, respectively. Using a QD laser, an ultra-low phase noise and quasi-tunable broadband OFC generator is obtained easily.

Tunable Ultra-Broadband Microwave Frequency Combs Generation Based on a Current Modulated Semiconductor Laser Under Optical Injection

We have demonstrated and characterized the generation of ultra-broadband microwave frequency combs (MFCs) based on a current modulated distributed feedback semiconductor laser (DFB-SL) subject to optical injection, and the comb spacing of MFCs can be tuned easily through adjusting the modulation frequency $\text{f}_{m}$ . For the DFB-SL under only current modulation with modulation frequency $\text{f}_{m }= 1.2$ GHz and modulation power $\text{P}_{m }= 22$ dBm, the generated MFC has a bandwidth of about 15.6 GHz within ±5.0 dB amplitude variation. Further, introducing continuous-wave optical injection into the current modulated DFB-SL with injection power $\text{P}_{i }= 1170~\mu \text{W}$ and no frequency detuning between the injection light frequency and the oscillation frequency of the free-running DFB-SL, the bandwidth of MFC can be increased to 57.6 GHz. Through measuring the single sideband (SSB) phase noises of some representative comb lines, the performances of the MFCs generated before and after introducing optical injection are compared, and the SSB phase noises at 10 kHz offset frequency can be increased by 10 dB for the harmonics with frequencies of more than $40\text {f}_{m}$ after adopting optical injection. Moreover, the influences of operation parameters on the bandwidths of MFCs are analyzed, and the optimized parameter range for generating ultra-broadband MFCs has been determined.

High- $Q$ Optoelectronic Oscillator Based on Active Recirculating Delay Line and Dual-Loop Topology

A high Q-factor optoelectronic oscillator (OEO) based on an active recirculating delay line and a dual-loop topology is proposed and demonstrated experimentally. The implemented OEO provides a very stable oscillation at 5.4 GHz with a sub-Hz 3-dB bandwidth and a $Q$ -factor in excess of $10^{10}$ . A single side-band phase noise of −74 dBc/Hz is measured at 10 kHz offset, while side modes are significantly suppressed for offset values in the range of 100 kHz–1 MHz.

Technical noise in K‐band low‐noise cryogenic amplifier

The performance of a 15–29 GHz low-noise high-electron-mobility transistor amplifier at room and cryogenic temperatures is reported. The close-to-carrier technical noise is measured for frequency offsets from 100 mHz to 100 kHz and the effect of adjusting the DC power biasing is investigated. An order of magnitude improvement in intrinsic phase noise is achieved by optimising the bias settings away from manufacturer specifications, giving a single-sideband phase noise power spectral density at 1 Hz offset of −100 dBc/Hz and −105 dBc/Hz for a 26.6 GHz carrier at room temperature and 6.5 K, respectively.

Femtosecond Laser-Based Microwave Signal Generation and Distribution

We review our most recent progress in microwave photonic applications of ultralow timing jitter femtosecond mode-locked fiber lasers. Sub-femtosecond timing jitter (integrated from 10 kHz to >10 MHz offset frequency) optical pulse trains can be generated from various types of mode-locked fiber lasers using dispersion engineering and intracavity filtering. To fully utilize such ultralow-jitter lasers for microwave photonic applications, we demonstrate a sub-femtosecond-resolution (−159 dBc/Hz phase noise floor) phase detection method between optical pulse trains and microwave signals using a Sagnac-fiber-loop-based device named the fiber-loop optical-microwave phase detector (FLOM-PD). Using ultralow-jitter mode-locked Er-fiber lasers and FLOM-PDs, we generate 10-GHz microwave signals with −142 dBc/Hz absolute single-sideband phase noise at 10-kHz offset frequency. When an all-fiber Michelson interferometer-based repetition-rate stabilization method is further employed, the phase noise is suppressed to −90 dBc/Hz at 10-Hz offset frequency, which results in 3-fs absolute rms timing jitter integrated from 10 Hz to 10 MHz offset frequency. Long-distance microwave phase transfer via optical fiber links is also demonstrated using the FLOM-PD as a means for stabilizing pulse time-of-flight in fiber transfer. Relative frequency instability of 6.5 × 10−19 is demonstrated for 2.856-GHz microwave signals transferred over a 2.3-km-long fiber link. We anticipate that the capability of generation, characterization, stabilization, and transfer of ultralow-noise microwave signals using ultralow-jitter femtosecond mode-locked lasers will find more applications in microwave photonics in the near future.

Tunable single-mode injection-locked optoelectronic oscillator with low phase-noise

Tunable single-mode injection-locked optoelectronic oscillator (OEO) with low phase-noise is presented in this article. A master oscillator contributed by amplifier and tunable band-pass filter (TBPF) is embedded in the general single loop OEO. The oscillation frequency is determined by the center frequency of the TBPF. A portion of master oscillation signal is injected into the slave OEO loop, then it is locked by OEO signal after it passes through a long optical delay line with high Q value. With the RF isolator, the master oscillation signal with poor phase-noise is avoided directly mixing in the OEO signal. With the configuration a tunable range from 1.93 to 17.69GHz with 68dB suppression of the nearest-neighbor spur is realized. The single-sideband phase noise is below −112dBc/Hz at an offset of 10kHz within the whole tunable range. The frequency drift of the OEO system is <±2kHz within 1h. With low cost and simple system, tunable single-mode RF signal with low phase-noise and high frequency-stability is generated.

A 4–32-GHz Chipset for a Highly Integrated Heterodyne Two-Port Vector Network Analyzer

This work presents a chipset for a highly integrated heterodyne vector network analyzer (VNA) with two ports and a multi-octave bandwidth from 4 to 32 GHz. The chipset is comprised of a stimulus integrated circuit (IC) with two selectable single-ended output channels and a four-channel receiver IC. Both chips contain a frequency synthesizer with an average output power of 2.5 dBm and a single-sideband phase noise between ${-}{\hbox{96.3}}$ and ${-}{\hbox{115.3 dBc/Hz}}$ at 1-MHz offset. The synthesizer consists of an array of three voltage-controlled oscillators with tuning ranges between 24.8% and 28.2% and a bandwidth extension stage. Wideband design techniques based on cascaded emitter followers are applied to a variable gain amplifier with a peak gain of 15.1 dB and to a wideband source switch with a minimum isolation of 23.6 dB. Single-ended receiver components such as a wideband low-noise amplifier with an average gain of 10 dB and a micromixer are used to compose the four-channel receiver with an average conversion gain of 14.4 dB. A hybrid microwave integrated circuit was fabricated in order to prove the functionality of a VNA utilizing the proposed chipset and wideband directional couplers. The measured scattering parameters of an arbitrary device-under-test showed an average deviation of 0.18 dB in magnitude and 1.8 $^{\circ }$ in phase from the measurements obtained with a commercial VNA.

Compact optoelectronic oscillator based on a Fabry–Perot resonant electro-optic modulator

A novel compact optoelectronic oscillator (OEO) employing a Fabry–Perot (FP) resonant electro-optic (EO) modulator is proposed and experimentally demonstrated. The resonant modulator is used as the optical storage element as well as the mode selection element, which can greatly reduce the system complexity and make the system more portable. Moreover, the optical resonance and electrical transmission response for the FP resonant EO modulator are theoretically and experimentally studied. The proposed OEO oscillates at 10 and 20 GHz in the proof-of-concept experiment, and the corresponding single-sideband phase noise can reach below −118 and −108 dBc/Hz at 1 MHz offset frequency, respectively.

SSB Phase Noise Evaluation of Analog/IF Signals on Standard Digital ATE

This paper presents a low-cost solution for the evaluation of frequency-domain phase noise characteristics for analog/IF signals. The technique is based on 1-bit signal acquisition with a standard digital channel of an Automated Test Equipment (ATE) and a dedicated post-processing algorithm that permits to reconstruct the time-domain phase fluctuations of the analog/RF signal from the captured binary vector. Single SideBand (SSB) phase noise is then obtained based on FFT applied on the reconstructed phase fluctuations. Simulation results demonstrate a very good agreement between SSB phase noise obtained using the proposed digital method and the conventional analog method on a large range of measurement frequency offset. The digital method also permits spur detection and exhibits similar performance than the conventional method in terms of measurement variability. The technique is also validated through hardware measurements on a practical case study, i.e. SSB phase noise evaluation on the 1.3125 MHz sinusoidal signal delivered by the transceiver of a JN5168 wireless microcontroller.

Self-oscillating optical frequency comb generator based on an optoelectronic oscillator employing cascaded modulators.

An ultraflat self-oscillating optical frequency comb generator based on an optoelectronic oscillator employing cascaded modulators was proposed and experimentally demonstrated. By incorporating the optoelectronic oscillation loop with cascaded modulators into the optical frequency comb generator, 11 ultraflat comb lines would be generated, and the frequency spacing is equal to the oscillation frequency of the OEO. 10 and 12GHz optical frequency combs are demonstrated with the spectral power variation below 0.82dB and 0.93dB respectively. The corresponding spectral pure microwave source are also generated and evaluated. The corresponding single-sideband phase noise are as low as -122dBc/Hz and -115 dBc/Hz at 10 kHz offset frequency.

Frequency stability and phase noise performance of X‐band to Ka‐band active multiplier

The performance of an active frequency doubler used to generate a pump signal for a solid-state microwave amplification by stimulated emission of radiation (MASER) based on paramagnetic impurity ions in sapphire is reported. The frequency doubler has been characterised in terms of phase noise, power dependence and frequency stability (Allan variance) for an output frequency range between 20 and 40 GHz. With the measurement system referenced to a 10 MHz hydrogen MASER, the doubler exhibits a single sideband phase noise of ∼−108 dBc/Hz at 1 Hz offset frequency, from which an upper limit fractional frequency instability of about 2 × 10−16 at 1 s integration time is estimated.

New kind of injection-locked oscillator and its corresponding long-term stability control.

A new type of opto-electronic hybrid oscillator is proposed for the first time, to the best of our knowledge, and verified by experiments in this paper. Typical electronic oscillator-dielectric resonator oscillator as the first injection source is used to injection lock the first long-fiber loop-based opto-electronic oscillator (OEO); then its output is used to injection lock the second long-fiber opto-electronic oscillator. Using this method, low-phase noise output signal can be obtained. Experiments show that single side-band (SSB) phase noise of a 9.5 GHz oscillation signal at 10 kHz offset frequency decreases from -123 to -135 dBc/Hz after the first injection, then, through the second injection, the SSB phase noise drops down to -146 dBc/Hz. In order to solve the long-term stability problem of the above oscillator, a new stability-control circuit also is designed and verified by experiments. Experiments show that the Allan deviation decreases from 9.0×10(-11) to 2.2×10(-12) during 1 s after the long-term stability-control circuit being used.

Frequency-tunable optoelectronic oscillator using a dual-mode amplified feedback laser as an electrically controlled active microwave photonic filter.

A widely tunable optoelectronic oscillator (OEO) based on a self-injection-locked monolithic dual-mode amplified feedback laser (DM-AFL) is proposed and experimentally demonstrated. In the proposed OEO structure, the DM-AFL functions as an active tunable microwave photonic filter (MPF). By tuning the injection current applied on the amplifier section of the AFL, tunable microwave outputs ranging from 32 to 41 GHz and single sideband phase noises below -97 dBc/Hz at 10 kHz offset from the carriers were realized.

A low-phase-noise 18 GHz Kerr frequency microcomb phase-locked over 65 THz.

Laser frequency combs are coherent light sources that simultaneously provide pristine frequency spacings for precision metrology and the fundamental basis for ultrafast and attosecond sciences. Recently, nonlinear parametric conversion in high-Q microresonators has been suggested as an alternative platform for optical frequency combs, though almost all in 100 GHz frequencies or more. Here we report a low-phase-noise on-chip Kerr frequency comb with mode spacing compatible with high-speed silicon optoelectronics. The waveguide cross-section of the silicon nitride spiral resonator is designed to possess small and flattened group velocity dispersion, so that the Kerr frequency comb contains a record-high number of 3,600 phase-locked comb lines. We study the single-sideband phase noise as well as the long-term frequency stability and report the lowest phase noise floor achieved to date with −130 dBc/Hz at 1 MHz offset for the 18 GHz Kerr comb oscillator, along with feedback stabilization to achieve frequency Allan deviations of 7 × 10−11 in 1 s. The reported system is a promising compact platform for achieving self-referenced Kerr frequency combs and also for high-capacity coherent communication architectures.