Photonic Polarity-Switchable Ultra-Wideband Pulse Generation Using a Tunable Sagnac Interferometer Comb Filter

A photonic approach to polarity-switchable ultra-wideband (UWB) pulse generation is proposed. The proposed setup principally consists of an electrooptic phase modulator (EOPM) and a tunable optical comb filter constructed with another EOPM inside a Sagnac interferometer. The comb filter working at its linear region performs the phase-to-intensity conversion to generate UWB pulses with monocycle shape. By adjusting the bias voltage of the EOPM inside the Sagnac interferometer, a shift of the comb filter can be achieved, which is the key point for a pulse polarity switch. A pair of monocycle pulses with reversed polarities was experimentally obtained by applying the dc bias of 0 and 1.9 V, respectively. The convenience to electrically control the pulse polarity is favorable for biphase modulation in UWB impulse radio applications.     

Analog and Digital Optical Pulse Synthesizers Using Arrayed-Waveguide Gratings for High-Speed Optical Signal Processing

In this paper, analog and digital optical pulse synthesizers using high-resolution arrayed-waveguide gratings (AWG) have been developed. The analog type of optical synthesizer consists of an AWG with an integrated 45deg, curved-surfaced mirror, a 4-f lens system, and an optically addressable spatial light modulator. The effective frequency resolution is 14.5 GHz. A dispersion compensation experiment is successfully carried out and a transform-limited short pulse has been obtained. This digital type of optical synthesizer comprises 30 frequency separated channels with a spacing of 12.5 GHz, where each channel includes an amplitude modulator and a phase modulator. The rectangular-shaped pulse is generated with this pulse synthesizer, together with a 12.5-GHz-spacing, optical frequency comb. The synthesizer can generate an optical pulse with any waveform. Moreover, using periodic characteristics of the pulse synthesizer, a 250-GHz repetition rate pulse train was generated, in combination with an ultrawideband, waveguide type of Fabry-Perot electrooptic modulator.     

基于SOA的L波段多波长锁模光纤环形激光器

报道了一种基于半导体光放大器(SOA)的L波段多波长光纤环形激光器,采用自制的100GHz信道间隔的光纤Mach-Zehnder(M-Z)干涉仪作为梳状滤波器,电吸收调制器(EAM)实现主动锁模,在1593.6nm附近获得了11个波长的同步锁模脉冲序列,脉冲重复频率为10GHz,半高全宽约为24ps,不同波长间功率不平坦度小于1dB。激光器具有工作稳定、输出光谱较宽和不同波长间功率波动小的特性。     

Generation and distribution of a wide-band continuously tunable millimeter-wave signal with an optical external modulation technique

A new technique to generate and distribute a wide-band continuously tunable millimeter-wave signal using an optical external modulator and a wavelength-fixed optical notch filter is proposed. The optical intensity modulator is biased to suppress the odd-order optical sidebands. The wavelength-fixed optical notch filter is then used to filter out the optical carrier. Two second-order optical sidebands are obtained at the output of the notch filter. A millimeter-wave signal that has four times the frequency of the microwave drive signal is generated by beating the two second-order optical sidebands at a photodetector. Since no tunable optical filter is used, the system is easy to implement. A system using an LiNbO/sub 3/ intensity modulator and a fiber Bragg grating filter is built. A stable and high spectral purity millimeter-wave signal tunable from 32 to 50 GHz is obtained by tuning the microwave drive signal from 8 to 12.5 GHz. The integrity of the generated millimeter-wave signal is maintained after transmission over a 25-km standard single-mode fiber. Theoretical analysis on the harmonic suppression with different modulation depths and filter attenuations is also discussed.     

基于偏振复用技术的光频梳研究

为提高光频梳带宽和谱线平坦度,设计了一种基于偏振复用和电吸收调制(EAM)技术的光频梳产生方 案。通过调整EAM 参数产生除中心载波外的高平坦度光频梳,再结合偏振复用技术优化中心载波峰值功率,使得光频 梳带宽整体提升一倍。文中讨论了相关参数对光频梳平坦度的影响,利用Optisystem 软件搭建了基于该方案的微波频 率可调载波重用全双工光载无线系统(RoF)。研究结果表明,在下行链路中当误码率为10-9 时,传输10 km 与背靠背 传输相比功率代价仅为0.42 dB。     

A 16-bit 250-kHz delta-sigma modulator and decimation filter

This paper describes a delta-sigma analog-to-digital converter (ADC) capable of converting input frequencies up to 250 kHz. It consists of a fifth-order switched-capacitor delta-sigma modulator and a decimation filter. Various design optimizations in the modulator are presented. The decimation filter consists of a comb filter followed by a novel, highly efficient and scalable finite impulse response filter. The ADC was implemented in 0.6-μm CMOS technology. It achieves a dynamic range of 94 db     

基于F-P滤波器的光纤光栅解调系统的优化设计

为了提高基于法布里-珀罗(Fabry-Perot,F-P)滤波器的光纤光栅波长解调系统的性能,提出了一种采用新型光纤梳状滤波器作为参考波长装置的解调方案.新型光纤梳状滤波器由两个啁啾光栅和一个光耦合器组成,与传统的参考光栅相比可以为解调系统提供更多的参考点.优化后的解调系统重复性好,运行更稳定、精确.     

1.8-THz bandwidth, zero-frequency error, tunable optical combgenerator for DWDM applications

We report on the experimental realization of a simple optical comb generator, based on phase modulation within an amplified fiber loop, which offers exact referencing to an arbitrary supplied reference frequency and tunable comb-line spacing. At a reference wavelength of 1529 nm up to 103 comb lines within a 40-dB power envelope were generated with spacings adjustable from 1 to 25 GHz, limited only by the bandwidth of the phase modulator     

一款高速、低功耗的Sigma-Delta模数转换器

提出了一种高速、低功耗、高分辨率的新型Sigma-Delta模数转换器(ADC)结构。该结构选择过采样率(OSR)为32的4阶调制器设计以缓解输出速率和通带宽度的压力,采用级联和双量化的方法进行优化,并利用SIMSIDES工具(基于Simulink的Sigma-Delta仿真器)进行仿真。数字抽取滤波器部分由级联积分梳状(CIC)滤波器、有限长单位冲激响应(FIR)滤波器和半带(HB)滤波器组成,并且三级滤波器都采用了多相分解结构,以降低动态功耗。使用0.18μm的标准CMOS工艺实现数字抽取滤波器版图。仿真结果表明,在250 kHz带宽下,有效位宽(ENOB)为19 bit。     

Synthesis of photonic microwave filters based on external opticalmodulators and wide-band chirped fiber gratings

The synthesis of photonic microwave filters employing optical sources with modulation side-bands, as multimode optical sources, and chirped fiber gratings is addressed. A single wavelength laser externally modulated using electrooptical Mach-Zehnder modulators and electroabsorption modulators have been proved as optical sources with modulation sidebands. Microwave filter features such as wide range tunability, compactness, readily reconfigurable frequency responses and flexibility have been achieved and demonstrated for the proposed structure. Experimental results using both a dual-electrode Mach-Zehnder electrooptical modulator and an electroabsorption modulator as optical sources with modulation sidebands are provided to demonstrate the feasibility of this technique     

Widely wavelength-tunable ultra-flat frequency comb generation using conventional dual-drive Mach-Zehnder modulator

Wavelength-tunable ultra-flat optical frequency comb generation is demonstrated using only a conventional Mach-Zehnder modulator that is asymmetrically dual-driven by large-amplitude sinusoidal signals with different amplitudes. A 10 GHz-spaced frequency comb with a 10 dB bandwidth of 230 GHz was experimentally generated. In addition, 50 nm widely wavelength tunable operation was achieved.     

A 5-V single-chip delta-sigma audio A/D converter with 111 dBdynamic range

A 5-V 24-b audio delta-sigma A/D converter has been developed. The single chip integrates stereo delta-sigma modulators, a voltage reference, and a decimation filter. A fourth-order cascaded delta-sigma modulator using a local feedback technique was employed to avoid overload without sacrifice in noise performance. A two-stage decimation filter architecture which reduces digital noise was developed. A new multistage comb filter was used for the first-stage, and a bit-serial finite impulse response (FIR) filter was used for the second stage. The 25.8 mm² chip was fabricated in 0.7-μm CMOS with low threshold MOS devices. Measured results show 111 dB dynamic range and 103 dB peak signal-to-(noise plus distortion)S/(N+D)     

基于相位调制器的宽带窄线宽的线性调频激光源的产生

提出了一种基于相位调制器(PM)和可调谐光滤波器产生线性调频激光信号的方法。该方法利用带有基频的微波线性调频信号作为相位调制器的驱动信号,窄线宽的激光种子源经相位调制器调制后产生一系列的宽带线性调频激光信号。通过可调谐光滤波器抑制其他边带保留所需阶次的线性调频激光信号。实验结果表明:当光滤波器保留正二阶调频激光信号时,获得了调频带宽为2 GHz、调频速率为6 THz/s的线性调频激光信号。在观测时间为1 ms时,测得的线性调频激光信号的瞬时线宽为3.2 kHz。该方法结构简单,易于实现,并且对调频连续波激光雷达、相干光谱分析等测量应用有重要意义。     

Performance predictions and topology improvements for optical serrodyne comb generators

Detailed simulations identify which optical components affect the performance of a radio frequency (RF) and optical comb generator based on an optical loop with a phase modulator. The simulations suggest that the topology of the loop can be modified to give a flatter RF spectrum and a greater resilience to fluctuations in the optical phase length of the loop. Furthermore, a method of filtering the laser's output to reduce the noise floor of the RF comb is proposed and verified. The simulations show that the linewidth of the source is critical to good performance, as are the quality of the sawtooth and the short-term phase stability of the loop. However, the amplified spontaneous emission noise (ASE) from the optical amplifier within the loop is relatively unimportant.     

Optical frequency comb generation based on dual-parallel Mach–Zehnder modulator and intensity modulator with RF frequency multiplication circuit

A new method of generating optical frequency comb by cascading a single dual-parallel Mach–Zehnder modulator and two intensity modulators is proposed. The intensity modulators are modulated by a frequency multiplication circuit of radio frequency. Theoretical model of the system is derived, and optical frequency comb with ultra-flatness and high side-mode suppression ratio can be obtained. The study results show that 72-line optical frequency comb with spectrum power variation of 0.26 dB, SMSR of 21 dB and frequency space of 4 GHz is gotten easily by adjusting the amplitude of radio frequency signal and the direct current bias of the modulators. The simulation result is in good agreement with the theoretical analysis model.     

Simple and Accurate Optical Frequency Domain Ranging Using Off-the-Shelf DFB Lasers Subject to Frequency-Shifted Optical Feedback

It is demonstrated that accurate distance measurement may be effected using a commercially available distributed feedback (DFB) semiconductor laser subject to frequency-shifted optical feedback. A simple experimental arrangement is employed wherein a chirped frequency comb is generated in an external cavity DFB laser using an intracavity acoustic-optic modulator. The frequency comb generates a beat frequency which is proportional to the path difference of a target and reference arm. An estimate of the accuracy and resolution of the measurement is given.     

双光频梳辅助的微波频率测量方法北大核心CSCD

为实现大频率范围内多微波频率的高精度即时测量,提出了一种基于双光频梳和法布里-珀罗滤波器(Fabry-Perot filter,FPF)的微波频率测量方案。将待测微波信号通过单边带调制加载在一路光频梳上进行频率复制,再将调制后的光信号通过一个法布里-珀罗滤波器进行信道分割。FPF的输出信号和另一路光频梳耦合后通过光解复用器实现信道化接收。通过设置合适的系统参数,可使得每个信道输出的拍频信号在同一窄带中频频段内。基于频率-光功率映射的原理,通过判断信号的存在性即可确定未知信号所处的频率段,实现信号频率的粗估计。通过对目标信道输出的微波信号进行采样、模数变换和信号处理可实现未知信号频率的高精度测量。通过实验仿真验证了所提方案的有效性,频率测量误差在±2.5 MHz内。     

用一维多元光子晶体实现光学梳状滤波的数值研究

把传输矩阵方法推广应用于研究一维多元光子晶体实现光学梳状滤波.数值结果指出,要实现光学梳状滤波,首先要找到合适的组元个数,并通过调节组元位置和厚度找到所需要的禁带中心位置与宽度;其次根据梳状滤波的梳齿数目、位置和透过率等具体要求,通过调节缺陷组数、缺陷组相对位置、缺陷组各组元厚度而达到梳状滤波设计的目的.     

基于级联相位调制器和光衰减器的光频梳产生研究

提出了一种基于级联相位调制器和光衰减器的光 频梳产生方案,建立了方案的理论模型并进行了 系统验证,研究了射频(radio frequency,RF) 信号幅度和光衰减器衰减系数对光频梳平坦度的影响。结果表明数值 计算与实验 结果一致性较好,通过调整RF驱动信号幅度和光衰减器衰减系数可产生梳线数量为15条、平坦度为 0.8 dB,边模抑制比(side-mode suppression ratio,SMSR) 为5.05 dB的光频梳。方 案中引入滤波器后,在梳线数量保持不变的前 提下,其平坦度和SMSR可分别提高62.5%和61.4%。     

Optical time-division multiplexing signal processing using electro-optic modulators

We present some optical signal processing methods for optical time-division multiplexing, based on electro-optic modulators. Dual-parallel Mach–Zehnder modulator and time-lens-based signal processing for optical frequency comb generation, optical Nyquist pulse generation and time-domain demultiplexing are realized. Multifunctional optoelectronic oscillators which are capable of performing simultaneous electrical clock recovery, optical clock recovery and demultiplexing are demonstrated with modulators embedded as the key components.