Integrated optical Mach-Zehnder modulator based on polycrystalline BaTiO3

Good-quality polycrystalline BaTiO3 thin films are deposited on MgO substrates by pulsed laserdeposition. The deposition parameters are optimized to achieve optical-quality films with an attenuation coefficient of 4 dB/cm at the 633-nm wavelength. Thin-film electro-optic Mach-Zehnder modulators are fabricated with standard lithography and ion-beam etching. The waveguides patterned by lithography are the ridge type, and they ensure single-mode propagation in the wavelength range of 633-1550 nm. An electro-optic coefficient of 22 pm/V is estimated for the polycrystalline BaTiO3 films.     

基于双平行马赫曾德调制器的动态可调光载波边带比光单边带调制：理论分析与实验研究

理论分析并实验研究了一种基于双平行马赫曾德调制器(DP-MZM)具有动态光载波边带比(OCSR)调谐能力的光单边带(OSSB) 调制实现方案, 方案利用DP-MZM内部集成的三个独立的调制单元, 分别实现OSSB调制、光载波移相和光信号干涉, 最终, 仅需改变调制器的一个偏置点, 就实现了OCSR的动态调谐, 实验得到了小信号调制(调制系数m=0.2)下, OCSR的可调范围-20.8–23.5 dB. 并分析了OCSR与射频功率之间的对应关系, 通过本方案调谐至最佳的OCSR可提高模拟光链路接收灵敏度. 关键词： 光纤通信 微波光子 光载波边带比 光单边带调制     

Tunable optical second-order sideband effects in a parity-time symmetric optomechanical system

We theoretically investigate the optical second-order sideband generation(OSSG) in an optical parity-time(PT) symmetric system, which consists of a passive cavity trapping the atomic ensemble and an active cavity. Compared with the double-passive system, it is found that near the exceptional point(EP), the efficiency of the OSSG increases sharply not only for the blue probepump detuning resonant case but also for the red one. Using experimentally achievable parameters, we study the effect of the atomic ensemble on the efficiency of the OSSG in the PT-symmetric system. The numerical results show that the efficiency of the OSSG is 30% higher than that of the first-order sideband, which is realized easily by simultaneously modulating the atom-cavity coupling strength and detuning. Moreover, the efficiency of the OSSG can also be tuned effectively by the pump power, and the efficiency is robust when the pump power is strong enough. This study may have some guidance for modulating the nonlinear optical properties and controlling light propagation, which may stimulate further applications in optical communications.     

Highly linear W-band receiver front-end based on higher-order optical sideband processing

A highly linear W-band receiver front-end based on higher-order optical sideband(OSB) processing is proposed and experimentally demonstrated. Two-tone analysis shows that by manipulating higher-order OSBs, the thirdorder intermodulation distortion(IMD3) introduced by optoelectronic components(mainly modulators) in the receiver front-end can be further suppressed, and a 9 dB improvement of the ratio of the fundamental and IMD3 can be attained. In the experiment, the spurious-free dynamic range of the W-band receiver front-end is up to 122.1 d B·Hz~(2∕3), with improvement by 9 dB compared with that of only processing the five OSBs.     

A novel reconfigurable radio-over-fiber system based on flexible optical devices

In this paper, a reconfigurable Radio over Fiber system based on optical switches, optical multimode interference power splitter and tunable optical filters is designed, which can achieve quadrature phase shift keying wireless modulation in optical domain and switch carrier frequency between 30 and 60 GHz. The scheme can make good use of bandwidth resource and realize signal transmission in fiber within 10 km.     

A two-stage optical frequency comb generator based on Mach-Zehnder modulator and Re-circulating frequency shifter

We propose a novel scheme to generate optical frequency comb by using a two-stage generator based on Mach-Zehnder modulator and re-circulating frequency shifter. Based on the Mach-Zehnder modulator a light source including 2 flat and stable frequency spectrum lines is generated at the first stage, and the light source is then used as the seed light in the re-circulating frequency shifter loop at the second stage. The scheme can greatly reduce the accumulated noise of the system. Through theoretical analysis and simulation it is shown that the proposed theoretical model of the two-stage system is proved in good agreement with simulation results.     

Improved dispersion tolerance of an optical duobinary transmitter based on a Mach-Zehnder modulator and an optical delay interferometer

We present a method for improving the dispersion tolerance of an optical duobinary transmitter based on a dual-arm Mach-Zehnder (MZ) modulator and an optical delay interferometer without electrical low-pass filters. Since such a duobinary modulator using a standard 1-bit delay cannot provide high dispersion tolerance, we investigated the impact of the modulator driving voltages and the bit delay in the interferometer to improve the transmitter’s dispersion tolerance.     

基于光子晶体马赫-曾德尔干涉仪的太赫兹开关及强度调制器

通过对二维正方晶格光子晶体线缺陷模色散曲线慢光特性的研究, 利用外电场对液晶分子取向的调控作用, 在填充液晶的正方晶格波导的马赫-曾德尔干涉仪结构中实现了开关和强度调制等功能. 利用平面波展开法计算了光子晶体波导的线缺陷模, 分析了液晶折射率的变化对缺陷模的影响. 计算表明, 液晶折射率仅改变了0.1, 线缺陷模有效折射率改变达0.168, 该特性可以更为有效地实现对相位的控制, 进而实现高消光比开关和强度调制功能, 这种高效的相位调节器件在集成光系统中将有很好的应用前景.     

Performance investigation of 110-Gbps optical MSK system using a Quad Mach-Zehnder IQ modulator

In this paper, numerical simulation is conducted to investigate the generation, transmission and detection of a 110 Gbps optical Minimum Shift Keying (MSK) signal. The transmitter has been designed using a Quad Mach-Zehnder IQ Modulator. At the transmitter, a 110 Gbps optical MSK signal with constant envelope and a continuous phase is generated by combining signals of I-arm and \(90^\circ\) phase shifted of Q-arm. Error-free transmission of 110 Gbps optical MSK signal is achieved after traversing a distance of 240 km, also a comparison is made with respect to Differential Phase Shift Keying (DPSK) to show its effectiveness. At the receiver side, the original signal is recovered through a balanced detection method, with a power penalty of around 3.34 dB. Also, BER curves of different bit rates for MSK are studied ranging from 40 to 120 Gbps and found that maximum 110 Gbps can be achieved error-free. The optical spectrum of both MSK and DPSK signals are observed and found that MSK is having narrower main lobes with smaller side lobes compared with that of DPSK, which in turn results in an increase in spectral efficiency and reduction in intersymbol interference.     

马赫-曾德光纤干涉光谱测量系统的设计

光纤干涉光谱仪由于其体积小、分辨率高、抗电磁干扰和耐高温的特点,广泛应用于各种领域的物质检测中。设计了一种使用电动光纤延迟线实现光程差调制的基于Mach-Zehnder光纤干涉仪的光谱测量系统。介绍了系统的构成,推导了基于该系统的光谱计算公式以及分辨率计算公式。搭建了实验平台,对一宽谱光源进行测试,并采集其干涉信号,解调出了相应的光谱图。对结果进行分析,当最大光程差变为0.479 5 cm时,光谱分辨率为2.085 4 cm-1。电动光纤延迟线的性能在很大程度上决定了最终解调出的光谱的分辨率、精度,尤其是速度和延时时间的精度和线性度。     

The transmission performance of the single sideband optical millimeter-wave with BPSK signal in the duplex radio-over-fiber link

This paper has investigated the transmission performance of the single sideband (SSB) optical millimeter (mm)-wave with signal carried by the sideband in BPSK format in duplex radio-over-fiber (RoF) system theoretically and numerically. The SSB optical mm-wave signal is generated by a LiNbO₃ Mach–Zehnder modulator and there exists an optimal modulation index to generate the SSB optical mm-wave with a maximal RF photocurrent. The SSB optical mm-wave is much suitable for the duplex ROF link with the uplink lightwave recovered from the downlink because the optical carrier carries no signal. In such a duplex RoF link, although there are the spurs on the optical carrier, they have little influence on the downlink and the uplink signal even if the modulation index is large.     

Asymptotic formalism for ultraflat optical frequency comb generation using a Mach-Zehnder modulator

We theoretically prove that a conventional Mach-Zehnder modulator can generate an optical frequency comb with excellent spectral flatness. The modulator is asymmetrically dual driven by large amplitude sinusoidal signals with different amplitudes. The driving condition to obtain spectral flatness is analytically derived and optimized, yielding a simple formula. This formula also predicts the conversion efficiency and bandwidth of the generated frequency comb.     

An all-optical polymeric light modulator based on a Mach-Zehnder interferometer

A new promising technology of manufacturing waveguide structures using polymeric materials has been invented. It has been applied to construct an integrated, all-optical, polymer-based light modulator based on a Mach-Zehnder interferometer.     

Photonic microwave phase shifter/modulator based on a nonlinear optical loop mirror incorporating a Mach-Zehnder interferometer

We realize a novel photonic microwave phase shifter/modulator based on a nonlinear optical loop mirror incorporating a Mach-Zehnder interferometer. A near-linear phase shifter exceeding 180 degrees and a phase modulation with 2.5 Gbit/s baseband signal are obtained for a 10 GHz microwave signal by this proposed device.     

基于外调制器的全双工无线信号光传输系统

提出了一种基于双平行马赫 增德尔调制器的全双工矢量信号传输系统。传统的光学倍频技术只适用于NRZ (not return to zero) 等强度调制格式,而不适用于无线通信中常用的MPSK、MQAM等矢量信号调制技术,用传统的倍频技术生成光毫米波后,用滤波器将其2个边带分开,在其中一个边带上调制矢量信号,这样幅度和相位信息被正确保留,且使用了8倍频模块,降低了传输过程中对光电器件的带宽要求。理论分析和仿真结果表明:通过此方法产生的携带在60 GHz载波上的625 Msymbol/s的4QPSK信号,经过20 km单模光纤传输后,误差向量幅度损耗可以忽略不计。     

Lateralization based on interaural differences in the second-order amplitude modulator

Second-order amplitude modulation is a relatively slow variation of the modulation depth of a first-order amplitude modulation with higher frequency. In contrast to first-order modulation, which appears as a physical component in the stimulus spectrum after half-wave rectification, second-order modulation is not necessarily demodulated by the auditory periphery. For binaural processing of second-order amplitude modulated stimuli it is unknown whether interaural time differences (ITDs) in the second-order modulation result in a lateralized percept. Thus, second-order modulation can serve as a tool to investigate whether demodulation of interaurally delayed components is a prerequisite for lateralization. In most of the psychoacoustic experiments presented here, a 25 Hz sinusoidally amplitude-modulated (SAM) 160 Hz tone was either transposed to 4 kHz by half-wave rectifying this SAM waveform before multiplication with a 4 kHz tone (TSAM), or by adding an offset before multiplication (SAMAM). The experiments revealed an inability to lateralize the SAMAM based on ITDs in the 25 Hz component, whereas subjects could lateralize the TSAM. Given that only the TSAM results in a demodulated 25 Hz component after peripheral auditory processing, this result supports the hypothesis that demodulation is a prerequisite for lateralization, which has consequences for temporal modulation processing in models of binaural interaction.     

Compact temperature-insensitive modulator based on a silicon microring assistant Mach-Zehnder interferometer

<正>On the silicon-on-insulator platform,an ultra compact temperature-insensitive modulator based on a cascaded microring assistant Mach-Zehnder interferometer is proposed and demonstrated with numerical simulation.According to the calculated results,the tolerated variation of ambient temperature can be as high as 134℃while the footprint of such a silicon modulator is only 340μm~2.     

A full-duplex radio-over-fiber system based on dual quadrupling-frequency

We proposed and simulatedly demonstrated a novel full-duplex radio-over-fiber system using an external modulator and an optical interleaver to generate dual quadrupling-frequency optical millimeter waves for carrying two base station downstream data and wavelength reuse for uplink connection. The simulation results reveal that the power penalties for the downstream and upstream signals of both base stations are less than 0.8 dB. In this new scheme, the configuration of the both base stations is simplified further because there is no additional laser at two base stations. The frequency of local oscillator signal is reduced due to frequency quadrupling. The cost of the new system is largely reduced.     

交叉克尔非线性对二阶非线性诱导透明的影响

考虑耦合介质存在交叉克尔非线性的情形下,研究了交叉克尔效应对耦合双谐振腔中二阶非线性诱导透明的影响.首先给出了描述体系理论模型的哈密顿量,再通过对海森堡-朗之万方程进行线性化,得到了探测场的透射率,进而得出系统的吸收和色散关系.研究结果表明,在交叉克尔非线性强度较小时,可忽略其对诱导透明的影响;随着交叉克尔非线性强度的增大,诱导透明窗口宽度随之快速变窄.此外,吸收曲线中还出现了双吸收峰.进一步增强交叉克尔非线性,导致原本出现的诱导透明消失,并在新吸收峰处产生了新的诱导透明,新的诱导透明的吸收零点位置随着交叉克尔非线性增加而向左偏移.这些结果可能在不透明介质的窄窗口光传输和提高光学腔的性能方面提供一些参考.     

Long-reach 60-GHz radio-over-fiber system based on turbo-coded OFDM

Turbo-coded 1.25-Gb/s orthogonal frequency-division multiplexing （OFDM） signals in 60-GHz radio-over-fiber system are demonstrated.It can overcome impairments in fibers and extend transmission distance.Experimental results show that the transmission distance of turbo-coded OFDM signals at 1.25 Gb/s with coding （pure bit rate of 830 Mb/s） can be extended by over 30%.