Optical Microwave and Millimeter Generation by Using Birefringent Fiber FP Cavity with Pulse Laser Injection

A novel optical microwave and millimeter generation by using single mode fiber FP cavity (SMFFPC) with pulse laser injection is proposed and experimentally demonstrated. The frequency of output signal is determined by the birefringence degree of the SMFFPC, a general relationship between output signal frequency of SMFFPC and birefringence degree of single mode fiber is derived. The proof of concept device consists of a light source, a polarizer controller, a modulator, a RF generator, a single mode fiber Fabry-Perot cavity, a strain inspector, an erbium doped fiber amplifier, a filter, a polarizer, and a digital communication analyzer. The results demonstrate the new concept of optical microwave and millimeter generation and the technical feasibility.     

重复频率可调谐的超低抖动光窄脉冲源的研究

提出了一种新型的基于光电振荡器的重复频率可调谐的超低抖动光窄脉冲源. 光电振荡器系统可以产生超低相位噪声的微波信号; 被该信号调制的直调光经过两次相位调制之后, 使光脉冲的啁啾增强; 再通过一段色散补偿光纤, 光脉冲被进一步压窄. 实验中使用YIG可调滤波器, 可以得到8–12 GHz内步进为200 MHz的可调谐微波信号, 因此光脉冲的重复频率具有可调谐性. 当微波信号即脉冲重复频率为9.6 GHz时, 测得脉冲宽度为3.7 ps, 相位噪声为-130.1 dBc/Hz@10 kHz. 由此得出光脉冲的瞬时抖动为60.1 fs (100 Hz–1 MHz), 因此该方案产生的光窄脉冲源具有超低的抖动.     

Microwave photonic filter’s application on the microwave signal generation based on an active mode-locked fiber laser

A novel scheme which utilizes the microwave photonic filter technique for the optical generation of a microwave signal based on an active mode-locked fiber laser is proposed. A microwave signal generator using a microwave photonic filter based on a 2: 1 optical coupler with a fiber loop which can effectively suppress a low-order frequency component of the microwave signal is demonstrated and a ～10-GHz microwave signal is achieved based on an active mode-locked fiber laser with the original pulse repetition rate of ～5 GHz.     

外部光注入混沌激光器产生超宽带微波信号的研究

利用外部光注入混沌激光器产生了完全符合美国联邦通信委员会关于室内无线通信频谱限定的超宽带(UWB)微波信号.基于外部光注入光反馈半导体激光器的速率方程组,理论研究了外部及内部参量对半导体激光器输出混沌UWB脉冲信号的影响.研究表明,UWB信号的-10 dB带宽随着光注入强度、注入失谐量以及线宽增强因子的增大而增大,随着激光器偏置电流的增大而减小.同时,UWB信号的中心频率在5–8 GHz范围内变化.在实验中,通过设定其他参量和调节光注入强度,得到中心频率及带宽可调谐的混沌UWB微波信号,传输速率达到500 Mbit/s.实验结果与理论分析相符合. 关键词： 半导体激光器 混沌激光 光生微波技术 超宽带信号     

2.87-Gb/s random bit generation based on bandwidth-enhanced chaotic laser

We experimentally demonstrate a fast random bit generator (RBG) based on bandwidth-enhanced chaotic laser from an optical feedback laser diode with optical injection.The bandwidth-enhanced chaotic signal is sampled and converted to a binary sequence in real time without the need of programming for off-line processing.Multi-rate bit sequences,with the fastest rate of up to 2.87 Gb/s,are obtained with verified randomness.     

基于外光注入互耦合垂直腔面发射激光器的混沌随机特性研究

通过在互耦合垂直腔面发射激光器(VCSELs)系统中增加外光注入, 建立了一种基于偏振可调光反馈VCSEL驱动互耦合VCSELs混沌系统模型, 分析了增加外光驱动对互耦合激光器随机特性的影响. 以不可预测度作为随机特性的评价指标, 采用信息论中的排列熵作为相应量化工具, 对系统输出混沌信号的不可预测性进行定量分析.数值研究了光强度、时延、偏振旋转角度以及驱动激光器与耦合激光器间的频率失谐对输出信号随机特性的影响.结果表明: 外光注入能够增大互耦合VCSELs输出混沌信号的排列熵, 即外光注入能够有效提高耦合系统的随机特性; 驱动激光器可调偏振片偏转角度调节到45° 附近, 注入强度适中, 满足耦合强度大于驱动激光器自反馈强度条件, 系统输出信号的排列熵较大; 在耦合时延与驱动激光器反馈时延不相等的同时, 增加驱动激光器与耦合激光器频率失谐, 外光注入互耦合VCSELs的随机特性能够得到进一步提高.     

A Method to Compute the Schrieffer–Wolff Generator for Analysis of Quantum Memory

Quantum illumination uses entangled light that consists of signal and idler modes to achieve higher detection rate of a low-reflective object in noisy environments. The best performance of quantum illumination can be achieved by measuring the returned signal mode together with the idler mode. Thus, it is necessary to prepare a quantum memory that can keep the idler mode ideal. To send a signal towards a long-distance target, entangled light in the microwave regime is used. There was a recent demonstration of a microwave quantum memory using microwave cavities coupled with a transmon qubit. We propose an ordering of bosonic operators to efficiently compute the Schrieffer–Wolff transformation generator to analyze the quantum memory. Our proposed method is applicable to a wide class of systems described by bosonic operators whose interaction part represents a definite number of transfer in quanta.     

Microwave Frequency Quadrupling Based on Distributed Feedback Laser and a Single Intensity Modulator

In this article, we have proposed and experimentally demonstrated a directly modulated distributed feedback laser (DFB-LD) to generate microwave and millimeter-wave signals. The proposed scheme uses DFB-LD and intensity modulator (IM) biased at null point. A radio frequency (RF) signal from a signal generator is split into two branches and one branch directly modulates the DFB-LD, while the other branch drives the IM. Two second-order sidebands separated by four times the frequency of the input RF signal are generated. Experimental results indicated that we can generate a four-fold microwave signal with a good optical signal to noise ratio.     

Synchronization of time delayed semiconductor lasers and its applications in digital cryptography

This work aims to demonstrate the effect of synchronization phenomena in chaotic laser systems described by modified Lang-Kobayashi's (L-K) delay differential equations. The synchronized system considered for numerical simulations and for cryptography consists of identical semiconductor lasers operating in single longitudinal mode. The two lasers are bidirectionally coupled by linear optical feedback. As this is essential in simultaneous transmission of messages, we have applied the corresponding coupled chaotic dynamics to secure communications. An investigation of the system together with a novel scheme for digital cryptography and visual recurrence analysis (VRA) of the chaotic time series are presented. Extended statistical tests with the proposed two phase scheme demonstrate the efficiency of these infinite dimensional systems in being tolerant to different types of statistical attacks. The result emphasizes the merits of the uncertainty and high dimensionality of optical chaos system in duplex high speed secure communications.     

基于平行偏振光注入的1550nm波段垂直腔表面发射激光器获取窄线宽光子微波的理论和实验研究

提出一种基于1550 nm垂直腔表面发射激光器(1550 nm-VCSEL)获取高质量微波信号的全光方案.在该方案中,采用波长位于VCSEL中被抑制模式的中心波长附近、振动方向与VCSEL中主导模式相同的偏振光注入(即平行注入)1550 nm-VCSEL获取高频微波,并借助双光反馈对该高频微波的线宽进行窄化.一方面,基于VCSEL的自旋反转模型,从理论上分析了采用该方案产生微波信号的可行性;另一方面,通过构建相应的实验系统,对该方案产生的微波的特性进行初步实验研究.实验结果表明:在合适的注入条件下,1550 nm-VCSEL能够产生30 GHz左右的微波信号,但该信号的线宽较宽(百兆水平);引入双光反馈后,微波线宽可被压窄两个数量级以上,得到了线宽低于1 MHz、信噪比大于40 d B的微波信号.     

光注入提高半导体激光器混沌载波发射机的带宽

外光反馈下的半导体激光器可视为混沌载波发射机.数值研究发现，外部强光注入可以显著提高混沌载波发射机的带宽，带宽提高的程度在一定范围内与注入光的强度成正比.当外部光注入系数k_inj=0.39时，混沌载波的带宽由无光注入时的2.7GHz增大到14.5GHz，提高了5倍多.研究还发现，在相同的注入强度条件下，当注入光的频率比半导体激光器的中心频率高2—4GHz时，可实现最大限度的带宽增强.此外，适当提高半导体激光器的偏置电流也可以在一定程度上提高其产生的混沌载波的带宽. 关键词： 半导体激光器 混沌 带宽     

基于双通道马赫曾德尔调制器调制边带滤波的微波光子移相器

提出了一种基于双通道马赫曾德尔调制器(DPMZM)调制边带滤波的微波光子移相器。在双通道马赫曾德尔调制器的结构中,在一路马赫曾德尔干涉仪上实现抑制光载波的双边带调制输出,而在另一路马赫曾德尔的相位调节臂上通过调节偏置电压实现光载波信号的光学移相,两路光信号经过干涉合路后由光纤布拉格光栅(FBG)滤除其中一个一阶边带,最后输入到光电探测器(PD)进行光电转换得到移相的微波信号。实验结果表明,基于DPMZM调制边带滤波的微波光子移相器具有传输特性稳定、输出幅度波动小的优点。该结构还具有相移调节响应速度快、应用频带宽以及移相范围大于360°等特点。     

An ultrabroadband microwave chaos generator with electron feedback: On the band of generation,statistical properties of signals,and field of application

An experimental investigation of the chaotic signals of a microwave generator with electron feedback (based on a virtual cathode) was carried out. It was found that microwave chaos generators with electron feedback are of ultraband generation. The statistical properties of the generated chaotic signals were shown. The perspective fields of application for the considered ultrabroadband chaos generators were given.     

混沌信号在光纤传输过程中的非线性演化

对光纤混沌传输理论及混沌信号与光纤传输媒介相互作用的物理机制进行了理论研究. 通过耦合激光混沌系统和光纤传输信道，提出光纤混沌信号传输的非线性演化物理模型. 着重分析光纤自相位调制对激光混沌信号传输与演化的作用. 结果表明：自相位调制不影响混沌信号脉冲的形状，但能产生非线性相移使混沌信号频谱展宽；自相位调制不影响混沌信号脉冲的功率分布和场强分布，但能影响混沌信号脉冲的功率频谱分布，影响混沌信号光场以及慢变场的变化. 提出混沌信号在光纤传输中的非线性演化频率啁啾和形式，数值模拟了混沌信号在光纤传输过程中的相位、频谱、场以及场的慢变部分的相空间等演化形式和特点. 关键词： 混沌 光纤 传输 演化     

Study on the method of controlling chaos in an Er-doped fiber dual-ring laser via external optical injection and shifting optical feedback light

Controlling chaos in an erbium-doped fiber dual-ring laser is studied by injecting an external light and shifting the phase of an optical feedback light. First, the parameters of the externally injected optical signal are adjusted to bring the chaotic laser into a single-period state and a multiperiod state, respectively. In addition, the single-mode locking in a single ring of the laser as well as the dual-mode locking in dual ring of the laser are found. Secondly, the method of optical feedback is used to stabilize chaos by controlling the parameters of the optical devices in an external optical path. We show that the optical negative feedback can stabilize the chaotic laser into a single-period state, while the optical positive feedback can stabilize the chaotic laser into another single-period state and a period-doubling state. Lastly, various dynamical states are produced in the laser by shifting the phase of the optical feedback light.     

切比雪夫光混沌发生器的优化

研究了利用马赫-曾德尔干涉仪来构造扩频序列的设计方法,并对以往提出的切比雪夫光混沌序列发生器的构造原理和方案进行了分析,针对其受到器件尺寸限制的不足,提出了利用余弦函数的性质对其改进的新方案,从而消除了原方案在设计上的局限性.同时通过外加电压对马赫-曾德尔干涉仪两臂折射率的调节增加了波长适应性功能,使得光混沌序列发生器可以在不同的入射波长下得到不同的切比雪夫光混沌序列. 关键词： 切比雪夫映射 混沌序列 Lyapunov指数 光混沌序列发生器     

Tunable optical frequency comb with a crystalline whispering gallery mode resonator

We report on the experimental demonstration of a tunable monolithic optical frequency comb generator. The device is based on four-wave mixing in a crystalline calcium fluoride whispering gallery mode resonator. The frequency spacing of the comb is given by an integer number of the free spectral range of the resonator. We select the desired number by tuning the frequency of the pumping laser with respect to the corresponding resonator mode. We also observe a rich variety of optical combs and high-frequency hyperparametric oscillation, depending on the experimental conditions. A potential application of the comb for generating tunable narrow band frequency microwave signals is demonstrated.     

Generation of a stationary train of chaotic soliton-like microwave pulses in self-oscillating ring systems with a ferromagnetic thin film

The generation of a stationary train of chaotic soliton-like microwave pulses has been observed in an isolated self-oscillating ring system with a ferromagnetic thin-film and a resonator. The pulses have been formed owing to three-wave parametric processes and modulation instability of a surface magnetostatic wave. The soliton-like character of the microwave pulses is indicated by the time dependence of the instantaneous phase of the signal envelope.     

Relativistic twistron based on backward-wave oscillator with modulating reflector and an efficiency of 56%

Technical Physics - Using numerical simulation, the operating mode of a relativistic Cherenkov microwave generator of the twistronic type has been demonstrated. The generator includes an...     

混沌光通信与OC-48光纤通信的波分复用

数值证实并分析了混沌激光通信与现行光通信的波分复用传输,对于100 GHz的信道间隔,混沌激光通信系统实现了传输速率为1 Gbit/s数字信号的保密传输,现行光通信系统实现了传输速率为2.5 Gbit/s数字信号的传输.研究表明,当现行光通信中脉冲光信号的峰值功率不超过17 dBm时,混沌激光通信可在传输距离80 km内实现并行传输.此外,当现行光通信中脉冲光信号的峰值功率为7 dBm时,系统接收到的信号质量受混沌激光通信的干扰很小,当光纤传输距离从80 km增加到160 km时,对应的眼图开启度从82% 关键词： 混沌光通信 混沌同步 波分复用 信道串扰