Optoelectronic oscillator-based interrogation system for Michelson interferometric sensors

High-performance interrogation systems for optical fiber sensors are extensively required for environmental condition monitoring applications.In this article,we propose and demonstrate a Michelson interferometer(MI)interrogation system based on an optoelectronic oscillator(OEO).The frequency of the OEO is related to the free spectral range(FSR)of the MI.Thus,when the FSR of the MI varies with a change in external physical factors,the frequency of the OEO shifts and can be used for interrogation.We demonstrate that the temperature sensitivity and interrogation resolution are 35.35 MHz/℃and 0.012℃,respectively.Such an OEO-based scheme enables wavelength-to-frequency mapping and promises a wide linear interrogation range,high resolution and high-speed interrogation.

Wideband Tunable Frequency-Doubling Optoelectronic Oscillator Using a Polarization Modulator and an Optical Bandpass Filter

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 -100dBc/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.

Optical pulse repetition rate division using an optoelectronic oscillator

An approach for frequency division of an optical pulse train(OPT) based on an optoelectronic oscillator(OEO) is proposed and experimentally demonstrated. When the OPT is injected into the OEO, a microwave signal with a frequency equaling fractional multiples of the repetition rate of the OPT is generated. This signal is then fed back to the OEO, maintaining its oscillation, while simultaneously serving as the control signal of a Mach–Zehnder modulator(MZM) in the OEO. The MZM acts as an optical switch, permitting specific pulses to pass through while blocking others. As a result, the repetition rate of the OPT is manipulated. A proof-of-concept experiment is carried out. Frequency division factors of 2 and 3 are successfully achieved. The phase noises of the OPT before and after the frequency division are investigated. Compared to previously reported systems, no external microwave source and sophisticated synchronization structure are needed.

基于偏振自稳定双环的受激Brillouin散射光电振荡器

基于偏振自稳定双环结构提出一种受激Brillouin散射(SBS)光电振荡器(OEO),利用SBS的窄带宽增益谱实现相位调制到强度调制的转换(PM-IM),并选择OEO的振荡模式,构造偏振自稳定双环结构,在每个回路中的输入光被45°Faraday旋转镜反射后,将通过45°Faraday旋转器和不同长度单模光纤返回其路径,保证输出信号和输入信号的偏振态始终相差180°,从而消除外界机械振动和温度干扰.由于环路结构为反射式往返传输,因此所需光纤长度缩短1/2.实验结果表明,该OEO通过改变泵浦光波长实现频率调谐,可产生1~16 GHz的微波信号,10 GHz处边模抑制比(SMSR)达67.14 dB,相位噪声为-116.3 dBc/Hz@10 kHz.

基于受激布里渊散射的二倍频光电振荡器

为了打破器件带宽限制,提高光电振荡器(optoelectronic oscillator, OEO)的频率范围,设计了一种基于受激布里渊散射的二倍频光电振荡器。系统并联了相位调制器(phase modulator, PM)和双平行马赫曾德尔调制器(dual parallel Mach Zender modulator, DP-MZM),利用受激布里渊散射效应(stimulated Brillouin scattering,SBS)实现相位调制器的相位转幅度调制;打破±1阶边带平衡,利用光电探测器(photodetector, PD)拍频得到基频10 GHz信号;驱动DP-MZM,使其工作在最小传输点,实现载波抑制双边带调制(double side band with suppressed carrier, DSB-SC)产生二倍频20 GHz信号。实验结果显示,所设计的振荡器在OEO环路中基频信号为10 GHz的情况下,产生了20 GHz的二倍频信号,通过分析其边模抑制比性能、频率功率稳定性及相位噪声对系统性能进行验证。

基于光电混合反馈控制的光电振荡器稳频研究

光电振荡器具有输出信号相位噪声低、频率可调的优点,已成为军民应用领域的研究热点。然而,目前光电振荡器存在输出信号频率不稳定的核心问题,这限制了其在工程中的应用和推广。基于此,文章研究了光电振荡器频率漂移机理,提出了一种基于光电混合反馈控制的光电振荡器频率稳定方法,该方法在保证光电振荡器低相噪的情况下可同时实现光电振荡器特定振荡频率的稳定输出。实验测试得到光电振荡器的稳定度达到了5.6×10^(-12)/天,这可以满足工程中对频率稳定的应用需求。

基于光电振荡器的变电站设备高精度温度监测系统

为有效监测变电站设备的实时温度,提出一种基于光电振荡器的高精度温度实时监测系统。首先,将温度信息映射到光电振荡器的振荡频率;然后利用现场可编程逻辑门阵列对温度参量进行实时解算,并通过4G模块将数据无线传输至终端,完成变电站设备温度的在线监测。通过实验验证了本系统对变电站设备温度实时监测的可行性和有效性。

Recent advances in optoelectronic oscillators

An optoelectronic oscillator(OEO)is a microwave photonic system that produces microwave signals with ultralow phase noise using a high-quality-factor optical energy storage element.This type of oscillator is desired in various practical applications,such as communication links,signal processing,radar,metrology,radio astronomy,and reference clock distribution.Recently,new mode control and selection methods based on Fourier domain mode-locking and parity-time symmetry have been proposed and experimentally demonstrated in OEOs,which overcomes the long-existing mode building time and mode selection problems in a traditional OEO.Due to these mode control and selection methods,continuously chirped microwave waveforms can be generated directly from the OEO cavity and single-mode operation can be achieved without the need of ultranarrowband filters,which are not possible in a traditional OEO.Integrated OEOs with a compact size and low power consumption have also been demonstrated,which are key steps toward a new generation of compact and versatile OEOs for demanding applications.We review recent progress in the field of OEOs,with particular attention to new mode control and selection methods,as well as chip-scale integration of OEOs.

Polarization-maintained coupled optoelectronic oscillator incorporating an unpumped erbium-doped fiber

A polarization-maintained coupled optoelectronic oscillator（COEO） with its performance significantly improved by a short-length unpumped erbium-doped fiber（EDF） is reported and experimentally investigated.A 10 GHz optical pulse train with a supermode suppression ratio of 61.8 d B and a 10 GHz radio frequency signal with a sidemode suppression ratio of 94 d B and a phase noise of-121.9 d Bc∕Hz at 10 k Hz offset are simultaneously generated. Thanks to saturable absorption of the 1 m unpumped EDF, which introduces relatively large cavity loss to the undesired modes and noise, the supermode suppression ratio and the phase noise are improved by 9.4 and 7.9 d B, respectively.

Experimental optimization of phase noise performance of optoelectronic oscillator based on directly modulated laser

The experimental optimization of a 10 GHz optoelectronic oscillator (OEO) based on a 1.55 μm directly modulated distributed feedback (DFB) laser is demonstrated in this paper. The phase noise of the directly modulated laser (DML) based OEO is significantly reduced by proper selection of the laser's bias current and by using a dispersion shifted fiber as a delay line. The phase noise performance of the DML OEO achieved after optimization is close to that of a conventional OEO constructed using a commercial DFB laser and a LiNbO 3 Mach-Zehnder modulator. The DML based OEO is most promising for future realization of a miniature OEO architecture with the components integrated on a semiconductor substrate.

High-Precision Magnetic Field Sensor Based on Fiber Bragg Grating and Dual-Loop Optoelectronic Oscillator

A novel fiber-optic magnetic field sensor with high interrogation speed and resolution by using an etched fiber Bragg grating(FBG)in conjunction with a dual-loop optoelectronic oscillator(OEO)is proposed and experimentally demonstrated.A commercial FBG is firstly dipped into mixed hydrofluoric acid solution to remove the cladding layer and then is embedded with the magnetic fluid(MF)as a sensing element.The central wavelength reflected from the FBG is related to the overall time delay of the dual-loop OEO,which determines the oscillating frequency of the OEO.Therefore,the magnetic field can be estimated by measuring the oscillating frequency shift of OEO.The experimental results show that the oscillating frequency linearly increases with the increment of the magnetic field,achieving the sensitivity of 16.3 Hz/Oe with a R-square of 0.991 in the range of 5 mT-10 mT.In addition,the maximum error is within±0.05 mT in the range of 7 mT-8 mT,which offers potentials in many fields where the high-precision magnetic field measurement is required.

Tunable frequency-multiplying optoelectronic oscillator based on a dual-parallel Mach-Zehnder modulator incorporating a phase-shifted fiber Bragg grating

A tunable frequency-multiplying optoelectronic oscillator(OEO) based on a dual-parallel Mach-Zehnder modulator(DPMZM) is proposed and experimentally demonstrated. In the proposed system, the tunable fundamental microware signal is generated by a tunable optoelectronic oscillator incorporating a phase-shifted fiber Bragg grating(PS-FBG). By adjusting the DC bias of the DPMZM, the frequency-doubled microwave signal with a tunable frequency range from 11 GHz to 20 GHz and the frequency-quadrupled microwave signal with a tunable frequency range from 22.5 GHz to 26 GHz are generated. The phase noises of the fundamental, frequency-doubled and frequency-quadrupled signals at 10 k Hz offset frequency are-105.9 d Bc/Hz,-103.3 d Bc/Hz and-86.2 d Bc/Hz, respectively.

A High Side Modes Suppression Dual-Loop Optoelectronic Oscillator With Fabry-Perot Etalon

A novel dual-loop technique was proposed for single-mode selection in an optoelectronic oscillator （OEO）. It consisted of a pump laser and a feedback circuit including an intensity modulator, a Fabry-Perot （FP） etalon, two optical fiber delay lines, two photodetectors, and an amplifier. By inserting the Fabry-Perot etalon, the proposed dual-loop OEO realized a single mode oscillation ranging from 0 Hz to 20 GHz. The strong oscillation mode was present at 15 GHz, and the side modes suppression ratio （SMSR） exceeded 140dB. More over the length of the two fiber loops were just 5 meters and 36 meters.

Time-delay signature characteristics of the chaotic output from an optoelectronic oscillator by introducing an optical feedback

In this work,via autocorrelation function(ACF)and permutation entropy(PE)methods,we numerically investigate the time-delay signature(TDS)characteristics of the chaotic signal output from an optoelectronic oscillator(OEO)after introducing an extra optical feedback loop.The results demonstrate that,for such a chaotic system,both the optoelectronic feedback with a delay time of T1 and the optical feedback with a delay time of T2 contribute to the TDS of generated chaos.The TDS of the chaotic signal should be evaluated within a large time window including T1 and T2 by the strongest peak in the ACF curve of the chaotic signal,and the strongest peak may locate at near T1 or T2.Through mapping the evolution of the TDS in the parameter space of the optical feedback strength and time,certain optimized parameter regions for achieving a chaotic signal with a relatively weak TDS can be determined.

Radio-frequency arbitrary waveform generation based on dispersion compensated tunable optoelectronic oscillator with ultra-wide tunability

Photonic generation of radio-frequency（RF） arbitrary microwave waveform with ultra-wide frequency tunable range based on a dispersion compensated optoelectronic oscillator（OEO） is proposed and experimentally demonstrated. Dispersion compensation scheme and specially designed fiber Bragg grating（FBG）-based Fabry-Perot（F-P） filters are employed in the OEO loop to realize a frequency tunable range of 3.5-45.4 GHz. An optimization process provided by the combination of an erbium-doped fiber amplifier（EDFA）and FBG is employed to improve the signal-to-noise ratio（SNR） of final RF signals. The generation of linearfrequency and phase-coded microwave waveforms, with a tunable carrier frequency ranging from 4 to 45 GHz and tuned chirping bandwidths or code rates, is experimentally demonstrated.

一种基于光电隔离和频率检测的光伏板故障检测方法

针对由于局部遮荫引起的热斑故障导致光伏板无法正常工作的问题,提出了一种基于光电隔离和频率检测的光伏板故障检测方法。首先设计了由光电隔离与RC振荡器构成的光伏板故障检测电路,利用光电隔离将光伏板的电流信号转化为阻值信号,控制RC振荡频率;然后设计了电路拓扑,依次检测模块频率参数,计算出相应的光伏板相对偏差,判断光伏板是否存在热斑故障;最后搭建实物电路与Proteus仿真实验,结果表明故障光伏板的输出频率及其相对偏差较低,可有效检测出光伏板热斑故障。

基于相位调制等效展宽激光线宽的极低相噪光电振荡器

光电振荡器是一种采用光电结合方式的新型微波频率源,其利用光学长时储能,可以实现极低相位噪声的信号输出。文章研究了光纤中散射噪声对光电振荡器相位噪声的影响,重点介绍了基于相位调制等效展宽激光线宽,抑制布里渊散射噪声架构,通过理论公式推导以及实验验证,表明了上述架构可极大改善光电振荡器的相位噪声。实验中采用调制频率为50 MHz、调制幅度为3.1的相位调制信号对激光线宽进行等效展宽,得到在10 GHz频率下为-157.3 dBc/Hz@10 kHz的极低相位噪声信号输出。

可重构多维度探测微波光子雷达

随着“太空经济”时代的到来,大国间的太空竞争也愈发激烈,对星载雷达探测系统的测量精度和多维度目标参数测量提出了更高要求。现有的星载雷达系统主要采用传统微波技术实现,面临电子器件速率低、工作带宽小、可重构性差等问题,这些问题越来越成为限制星载雷达系统进一步发展的瓶颈。将微波光子技术引入雷达系统可利用光子技术高频率、大带宽、可重构的特点有效克服电子技术的局限性,突破雷达技术瓶颈。阐述了可重构多维度目标探测微波光子雷达的特点和基本结构,介绍了多维度目标参数测量和雷达波形可重构的原理与方法,并对星载微波光子雷达的发展趋势和特殊应用环境需要考虑的问题进行了论述。随着微波光子雷达技术研究的不断深入和光电集成技术的迅速发展,微波光子雷达有望在未来星载雷达系统中得到大规模应用。

光电反馈抑制DBR单纵模光纤激光器的弛豫振荡噪声

报道了使用光电反馈法对1.5μm分布式布拉格反射(DBR)单纵模光纤激光器强度噪声的抑制结果。通过分析光纤激光器的泵浦扰动到激光输出功率波动的传递函数,发现其相频响应在弛豫振荡频率处有180°相位突变。因此,依据已有的商用比例积分(PI)控制电路设计并构建了一阶移相网络,在弛豫振荡频率处提供45°超前相位以补偿该频率处的相位突变。采用该反馈控制系统,可将激光器的弛豫振荡峰由−95 dB/Hz降至−125 dB/Hz,抑制幅度高达30 dB。抑制后的光纤激光器有望在精密测量等应用中发挥重要作用。

耦合式光电振荡器的动态腔长稳定控制

提出了一种基于耦合式光电振荡器的动态腔长长时稳定控制方案,当光谐振腔腔长变化时,通过同相正交(in-phase/quadrature,I/Q)混频器测量光谐振腔内选定两点的谐振相位变化量,反馈控制光电再生腔的光延迟线进行再生腔长跟随补偿,实现可变腔长的耦合式光电振荡器的锁模控制输出,从而将变化的谐振腔腔长转化为变化的谐振频率进行精密测量。经过系统实验,当谐振腔长变化时,振荡器可实时锁定输出可变的微波信号,并保持边模抑制比优于47.26 dB,1 h内功率抖动小于0.28 dB,锁定相位误差抖动在±1.5°以内。