A 10-GHz Optoelectronic Oscillator at 850 nm Using a Single-Mode VCSEL and a Photonic Crystal Fiber

We demonstrate an optoelectronic oscillator using a gain-switched single-mode vertical cavity surface-emitting laser and a single-mode photonic crystal fiber. A 10-GHz optical pulse train at 850 nm with a timing jitter of 1.2 ps was successfully generated.     

基于F-P腔的干涉/强度调制型光纤温度传感器

介绍了一种基于非本征F P腔的干涉/强度调制型光纤温度传感器。宽谱光源发光二极管(LED)发出的光经过2×2耦合器C1 传给F P传感头,传感头返回光信号再次经过耦合器C1 及C2 后分成两路,一路直接传给光电探测器D1,另一路经过窄带滤光片再传给D2,光信号经光电转换及放大后由计算机采集处理。给出了采用不同谱宽的两路光信号进行自补偿运算和温度测量的理论模型,并简单分析了影响这一温度传感器长期稳定性的原因。实验中利用Levenberg Marquardt非线性拟合得到与理论模型符合很好的温度定标曲线。该传感器在 20~200℃量程内,温度变化最小分辨率达到0 .1℃,长期测量精度达到±0. 2℃。     

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。     

Optoelectronic oscillator employing reciprocating optical modulator for millimetre-wave generation

An optoelectronic oscillator that employs a reciprocating optical modulator is demonstrated. By giving positive optoelectronic feedback to the modulator, the reciprocating modulation in the modulator effectively multiplies the fundamental oscillation frequency by several times. A 52.8 GHz millimetre-wave signal is generated by self-oscillation.     

Fiber-grating-based self-matched additive-pulse mode-locked fiberlasers

Fiber-grating-based self-matched additive-pulse mode-locked (APM) fiber lasers were investigated both theoretically and experimentally. With three fiber gratings to form the linearly coupled cavities, such a fiber laser system could generate stable mode-locked output without critical cavity length control. It was shown that the wavelength dependence of the effective penetration length of a fiber grating led to the self-matching of the cavity lengths of the coupled cavities. A millimeter-order cavity-length mismatch could be tolerated. In a similar laser structure using chirped fiber gratings with a designated arrangement of the grating polarities, the APM fiber laser could have the advantages of higher tolerance of cavity-length mismatch and stretched-pulse amplification. After pulse compression with a piece of single-mode fiber, output pulses with full-width at half-maximum pulsewidths of 930 fs were obtained     

A 10-GHz Optoelectronic Oscillator at 1.1 m Using a Single-Mode VCSEL and a Photonic Crystal Fiber

We report a self-starting optoelectronic oscillator operating at 1.1 $mu{hbox {m}}$ that uses a gain-switched vertical-cavity surface-emitting laser (VCSEL) and a single-mode photonic crystal fiber. The modulation bandwidth and sidemode suppression ratio of the VCSEL were 7.2 GHz and more than 50 dB, respectively. A 10-GHz 11.5-ps optical pulse train with a timing jitter of 0.9 ps was successfully generated.      

Injection-Locked Hybrid Optoelectronic Oscillators for Single-Mode Oscillation

We demonstrate single-mode extraction from multiple modes in a 30-GHz optoelectronic oscillator (OEO) by injecting OEO modes into an electrical oscillator. The electrical oscillator is injection-locked by one OEO mode resulting in single-mode oscillation. The single-mode oscillation frequency can be tuned by changing the electrical oscillation frequency.      

耦合式光电振荡器的理论与实验研究

为了研究耦合式光电振荡器,阐述了耦合式光电振荡器的模式选择理论,给出了维持最佳锁模状态的相位匹配条件,分析了影响射频信号相位噪声的因素,进行了基于保偏机制的耦合式光电振荡器的实验研究。采用分别调节光环形腔和光电微波振荡环路中的保偏可变光纤延迟线可改变腔长的方法,获得了腔长与振荡频率的关系。同时,采用鉴频法测量了不同条件下5GHz射频信号的相位噪声,研究了影响射频信号相位噪声的因素。结果表明,耦合式光电振荡器的振荡模式取决于光环形腔的腔长,射频信号相位噪声受到光信号偏振态、相位匹配、环路长度等因素的影响。实验中获得了偏移频率10kHz处相位噪声达到-136dBc/Hz的5GHz射频信号,是目前国内已知的相位噪声最低的耦合式光电振荡器。     

Coupled Optoelectronic Oscillation via Fundamental Mode-Locking in a Composite-Cavity Electro-Optic Microchip Laser

Composite-cavity electro-optic microchip lasers have been proposed as a source for high-speed, low-noise microwave and optical signals. Such signals can be produced from a single short-cavity laser using the coupled optoelectronic oscillation architecture, but strict control of the cavity longitudinal modes must be maintained to achieve fundamental mode-locking. The mechanism for this control is studied analytically and it is determined that the Lorentzian gain approximation does not predict nonadjacent modal effects in short-cavity lasers. A modification is presented which can explain these effects. Experimentally, the modal structure of an adjustable short-cavity laser is investigated and the results are consistent with the revised model. Finally, the results of the theory are used to design an optimized cavity geometry that is used to successfully demonstrate FM mode-locking and coupled optoelectronic oscillation at 20 GHz using a Nd:YVO₄/MgO:LiNbO₃ prototype.     

Experiments on modulation properties and optical feedback characteristics of laser diodes stabilized by an external cavity or injection locking

In the wavelength range near 1.3-μm, single-mode operation of laser diodes is achieved by means of an external cavity and injection locking. The influence of digital modulation and optical feedback from a directly taper-coupled fiber is investigated. Lasers stabilized by injection locking showed excellent side-mode suppression at CW-operation but strong side modes when the laser was modulated. The frequency of the main mode is neither affected by modulation nor by optical feedback from the fiber. On the contrary the laser stabilized by an external cavity exhibited good side-mode suppression even when it was modulated. However, the frequency stability of the main mode was influenced severely by optical feedback and modulation. A transmission experiment over 21 km at a bit rate of 2.24 Gbit/s showed that this simple stabilization method is sufficient for applications in optical wide-band IM-PCM transmission systems.     

基于法布里-珀罗标准具的双环路光电振荡器

设计了一种基于法布里-珀罗(FP)标准具的双环路光电振荡器(OEO),该振荡器能将连续的光功率转换为稳定的频谱纯净的微波信号。FP标准具具有滤波的特性,因此可以替代普通OEO中的电滤波器从而降低电噪声,此外,FP标准具是一种高Q值的光学器件,可以缩短普通OEO所使用的光纤长度。双环路结构的引入能够更好地保证振荡器的单模输出,进一步降低相位噪声。仿真结果证明这种新型结构的OEO可以实现20GHz范围内振荡频率为15GHz的单模起振,边模抑制比超过150dB,使用的两条光纤环路长度分别为5m和36m。     

多波长掺镱光纤线形腔激光器的实验研究

利用两个光纤环镜作为线形腔的端镜,在其中一个环镜中加入腔长可调的F-P腔构成梳状滤波器,从而产生波长间隔可调的多波长激光振荡.实验结果表明,当波长间隔大于1.3nm时,器件可以产生室温下稳定的多波长激光.     

激光传感通信技术的智慧医疗监测系统

将激光传感通信技术应用在智慧医疗监测领域,设计高监测精度、高传输速率的智慧医疗监测系统。利用激光传感技术设计体温测量模块,模块采用F-P腔匹配滤波解调方法,泵浦源发射光产生宽带光在谐振腔生成激光,抵达光栅后原路反射到达F-P腔中心波长解调,光电探测器接收光栅反射光与F-P腔透射光的卷积,获取体温监测信号;激光跳频通信模块FPGA以串口为中介发送、接收医疗数据,模块的ASK基带编码激光调制依据调制激光循环频率随调制信号基带频率的变换的原理,计算可变基频调制信号,实现医疗数据通信传输。得到以下实验结论:体温测量模块能够提升中心波长,节约模块测量人体体温用时;激光通信模块可连续传输医疗数据,运行稳定。     

A Stabilized MIC Oscillator Using a Germanium Avalanche Diode (Short Papers)

A stabilized X-band oscillator using a germanium avalanche diode in a microwave integrated circuit (MIC) is proposed. The stabilization is achieved by coupling a transmission cavity to the resonant cavity in which an avalanche diode is embedded. A mode-jumping problem inherent in a coupled-cavity oscillator was solved coupling a third varactor-embedded low-Q cavity to the transmission cavity. As a result, single-mode oscillation in an MIC oscillater was successfully obtained. Varactor tuning can also be realized with as small a change in output power as 7 percent for a tuning range of 30 MHz. The experimental results and the theoretical analysis of the new stabilized oscillator are given.     

基于激光外调制的频率可调谐光电振荡器

为了实现光电振荡器(OEO)输出频率的可调谐,提出了一种基于外调制激光的频率可调谐光电振荡器。此方案在单环OEO的基础上增加一个由微波滤波器、电衰减器、电放大器和电移相器构成的电增益选频腔,通过调节电移相器的偏置电压可以等效改变电选频腔的腔长,从而改变其输出微波信号的频率;同时调节光延时线来改变光电振荡器的起振模式,通过电增益选频腔信号与光电振荡器自由振荡信号的电注入锁定,即可实现频率可调谐的光电振荡器,其输出信号的频率由锁定OEO模式的电增益选频腔决定。实验结果表明,本方案产生了频率调谐范围为10.05 GHz~10.09 GHz、调谐步长为400 kHz的输出信号,频率在40 MHz的范围内连续可调谐。在输出频率为10.0519 GHz时,其边模抑制比为60 dB,相位噪声为-115 dBc/Hz @10 kHz。该方案结构简单,既保留了单环OEO低相位噪声的优势,又能有效抑制边模,为实现频率可调谐OEO提供了一种新的方法。     

1550 nm高效窄线宽光纤激光器

研制了一种采用双光纤光栅法布里-珀罗(FBG F-P)腔选模的线形腔结构窄线宽光纤激光器.激光器以高掺杂Er3 光纤为增益介质,结合非相干技术,利用全光纤型法拉第旋转器(FR)抑制空间烧孔效应,通过2个短FBG F-P腔选模,产生了稳定的1 550 nm单频激光输出.采用两端976 nm LD抽运方式,阈值抽运光功率为11 mW,在抽运光功率为145 mW时输出信号光功率为73 mW.光-光转换效率为50%,斜率效率达55%.采用延迟自外差方法精确测量光纤激光器线宽,实验中使用了10 km单模光纤延迟线,由于测量精度的限制,得到线宽小于10 kHz.研究表明,这种光纤激光器具有输出功率高、线宽窄和信噪比高的特点,可用于高精度的光纤传感器系统.     

Semiconductor laser stabilization by external optical feedback

A report is presented on a general theory describing the effect of external optical feedback on the steady-state noise characteristics of single-mode semiconductor lasers. The theory is valid for arbitrarily strong feedback and arbitrary optical feedback configuration and spectrum. A generalized Langevin rate equation is derived. The equation is, in general, infinite order in d/dt constituting an infinite-order correction to the low-frequency weak-feedback analysis. The general formalism includes relaxation oscillations and permits analysis of the effect of feedback on the laser linewidth, frequency noise, relative intensity noise, and the relaxation oscillation sidebands in the field spectrum. The theory is applied to two important feedback configurations: the laser coupled to a single mirror and the laser coupled to a high-Q cavity     

Wavelength Selector External Cavity Laser Diode by Fiber Switch

A Fabry–Perot laser diode coupled to a single-mode fiber Bragg grating has the ability to emit a single longitudinal mode. In this paper a wavelength selector source based on a mechanical fiber switch used to change the Bragg grating in front of the laser diode is investigated. The external laser wavelength is changed. Critical coupling exists between the two fiber ends of the switch, which leads to the creation of a parasitic cavity inside the laser cavity. The aim of this work is to optimize the coupling ends of a single-mode fiber switch with respect to coupling efficiency and afterward measure the laser output power variation and spectrum to check their optical feedback characteristics on the relative intensity noise. Typical emission performance is a power of −2.5 dBm with a SMSR of 43 dB and a RIN of −146 dB/Hz.     

宇称时间对称光电振荡器技术研究进展

随着微波技术的不断进步,提升本振信号源的频率稳定度及相位噪声指标的需求尤为迫切.光电振荡器技术因具备极低的相位噪声以及良好的频率拓展性吸引了研究人员的广泛关注.但光电振荡器内部的长距离光纤大量增加了输出信号的边带,如何解决单模输出与相位噪声之间的矛盾成了光电振荡器领域研究的热点.宇称-时间对称方法在保证输出信号相位噪声的前提下可极大地优化输出信号的边带抑制,受到国内外研究团队的广泛关注.文章在对宇称-时间对称光电振荡器的工作原理和特性进行阐述和分析的基础上,对国内外研究团队设计的宇称-时间对称光电振荡器结构和方案进行了总结,分析比较了各种方案的基本原理及性能指标,讨论了宇称-时间对称光电振荡器技术的未来发展方向.     

Gain-clamped fiber amplifier with a loop mirror configuration

A new configuration of a gain-clamped fiber amplifier is proposed and demonstrated. A laser cavity was formed by a fiber grating and a loop-mirror containing an erbium-doped fiber amplifier in its loop. Owing to the loop-mirror property, the signal light does not enter the laser cavity, and the signal light around the oscillation wavelength can be amplified in the same way as signals far from the oscillation wavelength. Our configuration also has an advantage that only the signal light appears at the output port