Single-sideband Phase Noise Research Articles

Tunable multi-frequency optoelectronic oscillator based on a microwave photonic filter and an electrical filter

We propose and experimentally demonstrate a multi-frequency optoelectronic oscillator (OEO) based on the phase-modulation to intensity-modulation conversion. A microwave photonic filter incorporating an optical fiber Bragg grating Fabry–Perot filter and an electrical yttrium iron garnet (YIG) filter in two branches are used to select the oscillation modes of the OEO. By adjusting the wavelength of laser source or the central frequency of YIG filter, two frequencies can be tuned independently within a wide range. The single sideband phase noises of the generated frequencies are measured experimentally. Moreover, the OEO shows potential ability to achieve more frequencies oscillation by multiplexing more optical and electrical filters.

Improvement of the phase noise model based on an optoelectronic oscillator using a directly modulated distributed feedback laser

A scheme of dual-loop optoelectronic oscillator (OEO) based on a directly modulated distributed feedback (DFB) laser is proposed and experimentally demonstrated. In the proposed scheme, thanks to the DFB laser with enough output optical power utilized as an optical source and a modulator at the same time, high-performance microwave signals are generated without external modulator and erbium-doped fiber amplifier (EDFA). A theoretical model based on the control theory is detailed to assess the single sideband (SSB) phase noise performance of the dual-loop OEO. The laser frequency noise under small-signal direct modulation is proposed and introduced to make the phase noise model more complete for the first time. According to the theoretical analysis, the close-in (<1 MHz) SSB phase noise floor of the dual-loop OEO is dominated by the flicker noise when the offset frequency is below 10 kHz, and determined by the laser’s relative intensity noise (RIN) when the offset frequency is beyond 10 kHz. Microwave signals with the frequency tuned from 8 to 12 GHz and 3-dB linewidth less than 100 Hz are realized. The side mode suppression ratio (SMSR) of the generated microwave signals are measured to be 55 dB based on the dual-loop configuration. Meanwhile, within the whole frequency tuning range, the SSB phase noises of about −125 dBc/Hz at 10 kHz offset frequency are obtained. The experimental results of the SSB phase noise agree very well with the simulation results based on the theoretical model.

All-optical microwave oscillator based on feedback modulation within distributed feedback laser diode

An all-optical microwave oscillator is proposed and experimentally demonstrated, in which a distributed feedback laser diode (DFB-LD) acts as light source and optical-optical modulator simultaneously. By employing stimulated Brillouin scattering (SBS) process for oscillation frequency selection and active optical comb filter for side-modes suppression, single-mode photonic microwave signal generation can be achieved through a pure optical oscillation. In the experiment, a stable 10.87-GHz photonic microwave signal is obtained. The signal quality is evaluated by measuring the side-mode suppression ratio and single side-band phase noise of the signal. The corresponding values are 42 dB and −85 dBc / Hz at 10 kHz, respectively. This scheme explores the innovative application potentiality of DFB-LD, which will benefit on-chip photonic microwave systems.

Method for the generation of microwave frequency combs based on a Vernier optoelectronic feedback loop.

Microwave frequency combs (MFCs) with flexible tunability and prominent phase noise performance are of importance to many applications, including consumer electronic product, fundamental research and military defence. It is difficult for traditional electronic signal sources to meet the imperative demand in terms of high frequency scale, due to a challenging problem of deteriorating phase noise performance with increasing frequency. Photonics-assisted methods have capacity of implementing the generation of microwave signals with high frequency and low phase noise. Here we report a novel photonics-assisted MFC generation method utilizing an optoelectronic feedback loop with a Vernier configuration. The proposed MFC generation system features self-sustained oscillation, inherent multiple-mode oscillation and low phase noise level. In the proof-of-principle experiment, the MFC generation system based on a dual-path Vernier optoelectronic feedback loop is demonstrated, and the comb spacing tuning from 3.072 to 4.710 GHz and the single sideband phase noise of -99.60 dBc/Hz at 10 kHz offset from the carrier are achieved.

Low phase noise and quasi-tunable millimeter-wave generator using a passively InAs/InP mode-locked quantum dot laser

A low phase noise millimeter-wave (MMW) signal generator is proposed and experimentally demonstrated with a C-band passively Fabry-Perot (F-P) quantum dot mode-locked laser. A novel method is proposed to generate low phase noise MMW signal, which is simply based on a commercial off-the-shelf dual-driven LiNbO3 Mach-Zehnder modulator and a passively F-P quantum dot mode-locked laser. MMW signal with the frequency of 30 GHz, 45 GHz and 90 GHz respectively is obtained experimentally. Single-sideband phase noise of the 30 GHz and 45 GHz MMW signal is −112 dBc/Hz and −106 dBc/Hz at an offset of 1 kHz, respectively. The linewidth of the 30 GHz and 45 GHz MMW signal is about from 225 Hz and 239 Hz. This is considered a very simple MMW generator with a quasi-tunable broadband and ultra-low phase noise.

Generation of Broadband Optical Frequency Comb Based on a Gain-Switching 1550 nm Vertical-Cavity Surface-Emitting Laser under Optical Injection

In this work, broadband optical frequency comb (OFC) generation by a gain-switching vertical-cavity surface-emitting laser (VCSEL) subject to optical injection is investigated experimentally. During implementing the experiment, a 1550 nm VCSEL under a large signal current modulation is driven into the gain-switching state with a broad noisy spectrum. By further introducing an optical injection, a high performance OFC can be produced. The experimental results demonstrate that the power and wavelength of the injection light seriously affect the performance of the produced OFC. Under proper optical injection parameters, two sub-combs originating from two orthogonal polarization components of the VCSEL can splice into a broadband total-OFC. By selecting optimized operation parameters, a high quality total-OFC can be acquired, with stable comb lines, high coherence, wide bandwidth of 70.0 GHz (56.0 GHz) within 10 dB (3 dB) amplitude variation and low single sideband phase noise at the fundamental frequency below −120.6 dBc/Hz @ 10 kHz.

A coupled all-optical microwave oscillator with large tuning range based on SBS

A coupled all-optical microwave oscillator with large tuning range is proposed. Without optical–electrical–optical conversion components or any electrical microwave devices, microwave signals can be generated through a pure optical oscillation. In this system, a fiber ring laser provides a set of frequency references for frequency selection. Meanwhile, it also serves as a high-Q active resonator to optimize phase noise performance. By transferring the cavity modes to an optical carrier and selectively amplifying some of the modes via stimulated Brillouin scattering, the oscillation frequency is preliminarily selected. A semiconductor optical amplifier in the fiber ring laser is employed to accomplish the optical envelope detection and feedback modulation. Once the oscillation system is closed, good quality and high stability single-mode microwave signals are generated. By varying the wavelength of Brillouin pump light, a tuning range from 2 GHz to 26 GHz is demonstrated. Furthermore, the single side-band phase noise of these microwave signals are around −90 dBc/Hz@10 kHz.

W-Band Optoelectronic Oscillator

We demonstrate the first W-band optoelectronic oscillator (OEO), that oscillates at 94.5 GHz with a measured single side band (SSB) phase noise of -101 dBc/Hz at an offset frequency of 10 kHz from the carrier. Side mode suppression of more than 65 dB has been achieved by using injection locking. This OEO has potential application as a signal source in emerging W-band applications (e.g. fiber-wireless links) and opens a path to low phase noise sources beyond 100 GHz.

Self-Forced Opto-Electronic Oscillators Using Sagnac-Loop PM-IM Convertor

Efficient phase to intensity conversion is key in Sagnac-loop based opto-electronic oscillators ( OEO). This paper features analytical modeling of phase to intensity conversion in practical Sagnac-loop interferometers, with practical coupling imbalance in 3-dB optical coupler, polarization imbalance of the non-reciprocal optical phase shifter (NRPS), and cross-talk ratio in polarization maintaining fiber (PMF). Single-sideband (SSB) phase noise of self-forced frequency stabilization technique of this OEO is also modelled using self-injection locked (SIL) and dual self-phase locked loop (DSPLL); the free-running and forced modeling results of Sagnac-loop based OEO matches with experimentally measured phase noise results. The measured phase noise of the SILDPLL based OEO at 10 GHz is −131 dBc/Hz at offset frequency of 10 kHz with approximately 11 dB phase noise reduction compared to the results of free-running OEO. Self-forced stabilization of OEO results in timing jitter of 19.5 fs, a factor of 6 times reduction in the free-running performance.

Photonic Microwave Generation Based on an OISL by Subharmonic Modulation From an OEO

Photonic generation of a low-phase-noise microwave signal based on period-one (P1) dynamics of an optically injected semiconductor laser (OISL) subject to subharmonic modulation from an optoelectronic oscillator (OEO) is firstly proposed and experimentally demonstrated. Under suitable injection parameters, an OISL can be driven into period-one (P1) dynamics, which can be regarded as a photonic microwave with a relatively large linewidth. By further introducing an OEO with a frequency of 1/2 P1 frequency to directly modulate the OISL, a low-phase-noise photonic microwave with P1 frequency can be obtained. For an OISL operating at P1 oscillation with a frequency of 16.96 GHz, after imposing a 1/2 subharmonic modulation of 8.48 GHz on the OISL by an OEO, the photonic microwave linewidth is reduced from 5.23 MHz to less than 1 kHz, and the single sideband (SSB) phase noise of the final photonic microwave is -102.5 dBc/Hz@10 kHz, which is close to the SSB phase noise of the OEO signal (-104.3 dBc/Hz@10 kHz).

A Monolithically Integrated Laser-Photodetector Chip for On-Chip Photonic and Microwave Signal Generation

An Indium-phosphide-based monolithically integrated photonic chip comprising of an amplified feedback laser (AFL) and a photodetector was designed and fabricated for on-chip photonic and microwave generation. Various waveforms including single tone, multi-tone, and chaotic signal generation were demonstrated by simply adjusting the injection currents applied to the controlling electrodes. The evolution dynamics of the photonic chip was characterized. Photonic microwave with frequency separation tunable from 26.3 GHz to 34 GHz, chaotic signal with standard bandwidth of 12 GHz were obtained. An optoelectronic oscillator (OEO) based on the integrated photonic chip was demonstrated without using any external electrical filter and photodetector. Tunable microwave outputs ranging from 25.5 to 26.4 GHz with single sideband (SSB) phase noise less than −90 dBc/Hz at a 10-kHz offset from the carrier frequency were realized.

Tunable single-mode microwave signal generation utilizing an all-optical coupled microwave oscillator.

A tunable all-optical coupled microwave oscillator is proposed and experimentally demonstrated. This system has no any electrical microwave devices as well as photoelectric conversion and electro-optic modulation. In this scheme, a fiber ring laser not only provides a set of frequency references but also acts as an active optical resonator. The oscillation frequency selection is carried out by cavity modes transfer and injection locking process. Due to the mode pulling effect, a self-adapting oscillation frequency locking is achieved. Through the microwave envelope detection and feedback modulation in a semiconductor optical amplifier (SOA), a microwave signal can be generated by a pure optical oscillation. In the experiment, good quality and high stability single-mode microwave signals are obtained, whose frequencies can be tuned from 6.93 GHz to 25.54 GHz by simply adjusting the wavelength of the master laser. Under different operation frequencies, the measured single-sideband phase noises are approximately -95 dBc/Hz at a 10-kHz offset from the carriers.

Comparison of Optical Frequency Comb and Sapphire Loaded Cavity Microwave Oscillators

The single-sideband phase noise power spectral density and Allan deviation of a portable microwave oscillator system based on an optical frequency comb stabilized to an ultra-low expansion Fabry-Perot reference cavity is characterized at carrier frequencies of 4.0, 8.0, and 16.0 GHz. Compared to industry standard sapphire loaded cavity oscillators, the photonic microwave oscillator shows superior phase noise at offset frequencies $3.0 \times 10^{-14}$ obtains at an averaging time of 400 ms.

Linearity improvement of RF mixer using double-linearization for 5 GHz applications

With 5G expected to roll out in 2020, the 5 GHz band will be sort after for sub-6 GHz 5G implementation. The feasibility of the wireless systems at 5 GHz will be primarily determined by the linearity of the RF down-converters in the receiver system. With growing battery-powered, portable, and wearable wireless devices, the task of achieving excellent linearity with low power consumption in RF down-converters is difficult. This work tries to overcome the difficulty by proposing a double-linearization (DL) based RF mixer. The proposed mixer circuit is designed using UMC 180 nm CMOS process libraries, and the post-layout simulations are carried out using Cadence SpectreRF in the presence of single-sideband phase noise. For a fundamental tone at 5 GHz and an interferer at 5.01 GHz, the proposed mixer using double-linearization achieves an input-referred third-order intercept point (IIP3) of 11.04 dBm, which is a 15 dB improvement over the IIP3 obtained before employing the proposed scheme. The proposed RF mixer circuit provides a conversion gain of 15.33 dB and an integrated double-sideband noise figure (DSB-NF) of 16.39 dB while consuming a low power of 1.5mW from a 1 V supply. The circuit also boasts an SFDR of 81.36 dB and IMR2 of 192.1 dB. The IIP3/mW ratio of the DL based mixer is 6.5 dB more than the recently proposed mixer topology. The layout of the proposed mixer consumes 0.57mm2.

Self-Oscillating Parametric Optical Frequency Comb Generation Using an Electroabsorption Modulated Laser-Based Optoelectronic Oscillator

A scheme for parametric optical frequency comb (OFC) generation using an electroabsorption modulated laser (EML) based optoelectronic oscillator is proposed and experimentally demonstrated. A phase modulator is cascaded with EML in the oscillating loop. In addition, the phase modulated laser is used as pump seeds for the parametric frequency mixer. In the mixer, a 100-m single-mode fiber is employed to compress the pump pulses, and the parametric process is stimulated in a 200-m-high nonlinear fiber (HNLF) with flat normal dispersion. In our experiments, a 10-GHz radio frequency signal with a side-mode suppression radio of 47 dB and a single-sideband phase noise of −109.89 dBc/Hz at 10 kHz offset is obtained. When the pump power injected into HNLF is 28 dBm, a 10-tone parametric OFC with a 5-dB power variation and spacing equal to the oscillation frequency is generated.

Optical Sideband Injection Locking Using Waveguide Based External Cavity Semiconductor Lasers for Narrow-Line, Tunable Microwave Generation

The generation by optical injection locking of spectrally unadulterated microwave signals using waveguide based external cavity semiconductor lasers (WECSL) is demonstrated. A tunable frequency of 2–11 GHz, limited by the modulator’s bandwidth and the photodetector (PD), was created as proof-of-experiment by the injection locking of the two WESCLs. A single sideband (SSB) phase noise of −75 dBc/Hz from the generated carrier at 10 kHz offset and a phase noise variance at an optimum injection ratio region was 0.03 rad2, corresponding to 1.7°, were observed. The main feature of this approach is the consolidation of the upsides of microwave generation at low phase noise with a broad tuning range and the capacity of hybrid photonic integration. In addition, the injection locking characteristics were used to determine the Q factor of the complicated optical cavities with unknown inner losses.

Tunable optoelectronic oscillator based on a polarization-dependent phase modulator cascaded with a linear chirped FBG

A tunable optoelectronic oscillator (OEO) based on polarization controlled frequency response shifting of a dispersion-induced microwave photonic filter (MPF) is proposed and experimentally demonstrated. The MPF consists of a phase modulator (PM), a linear chirped fiber Bragg grating (LCFBG), and polarization multiplexed dual loops. Thanks to the polarization properties of the LiNbO3 crystal, the center frequency of the MPF can be tuned by simply adjusting the polarization state of the optical signal, and a tunable optoelectronic oscillator is established. Compared to the previous structure, the expensive wavelength-tunable laser is not needed in the proposed structure. In addition, the instability of oscillation frequency caused by the bias drifts of the modulator is avoided. A pure oscillation signal with a tunable frequency range from 3.3 to 7.3 GHz is generated. The single-sideband phase noise of the oscillation signal is about −110 dBc/Hz at 10-kHz offset. During more than 30 min observation, the oscillation frequency drift is about 7 kHz.

Low phase noise optoelectronic oscillator based on an electroabsorption modulated laser

An optoelectronic oscillator (OEO) scheme based on an electroabsorption modulated laser (EML) is proposed and experimentally demonstrated. The oscillation conditions and a complete phase noise model for the EML-based OEO are detailed. A 20-GHz microwave signal with a side-mode suppression ratio of 42dB is generated and evaluated. The corresponding single sideband phase noise with a 1-km and 4-km fiber used in the loop is respectively measured to be -110.2 dBc/Hz and -114.8 dBc/Hz at 10kHz offset frequency. The experimental phase noise results agree well with the theoretical results in an offset frequency range from 100Hz to 10MHz.

Time and reference frequency transfer over 850 nm VCSEL for digital telecommunication network synchronization

Accurate time transfer and synchronization between different network nodes is a key functional requirement in digital communication. Developments in optical fiber-based frequency dissemination techniques have improved optical frequency stability over time to much lower levels. In this work, we experimentally present the reference frequency transfer employing 850 nm vertical cavity surface emitting laser (VCSEL) over 100.3 m OM3 multimode fiber for synchronization of clocks on networked devices such as servers and racks/pod at different data center network nodes. A low-cost power-efficient multimode VCSEL with central wavelength at 844.26 nm is directly modulated with a 2 GHz reference frequency (RF) clock signal, and transferred over 100.3 m of OM3 multimode fiber. The single side band (SSB) phase noise of -104.62 dBc/Hz and −100.70 dBc/Hz is experimentally measured at back-to-back (B2B) and 100.3 m OM3 multimode fiber transmission respectively at a 1 kHz frequency offset. The jitter stability of 0.14 ps and 0.15 ps is experimentally achieved at B2B and 100.3 m fiber transmission, respectively. This work provides an alternative viable approach for the development of time keeping devices in high-speed short-reach optical communication systems.

High-performance millimeter-wave synergetic optoelectronic oscillator with regenerative frequency-dividing oscillation technique.

A novel millimeter-wave synergetic optoelectronic oscillator based on regenerative frequency-dividing oscillation and phase-locking techniques is proposed and experimentally demonstrated. The regenerative frequency-dividing oscillator is embedded for millimeter-wave frequency division, and then synergistically oscillates with the optoelectronic oscillator (OEO) due to injection-locking effect. The phase-locking stabilization technique is skillfully utilized in millimeter-wave OEO via commercial analog phase shifter. As a result, a 40-GHz signal is generated featuring low phase noise, high stability and low spurs. The single-sideband phase noise is about -117 dBc/Hz at 10-kHz offset frequency and the spurious suppression ratio reaches more than 80 dBc. The measured overlapping Allan deviation of the proposed synergetic OEO reaches lower than 10-13 at 1024-s averaging time, which is five orders of magnitude lower than free-running millimeter-wave OEO.