光纤多路模拟电视传输

本文指出光纤通信除在公用和专用数字通信网发挥广泛作用外,近年又在模拟电视传输和有线电视网开展新兴业务,利用多路宽带传输代替原先的单路基带传输。在副载波频分多路的频段内,每路有调频和调幅两种方式。沿干线传输电视,每路宜用调频,而在有线电视分配网,每路宜用残留边带调幅。单模光纤的工作波长倾向于使用1.3μm,而不是1.55μm。为此,1.3μmDFB激光管是关键器件,应具有高线性特性,以便同时传输较多路数的电视,又要求提供大功率,以便扩大服务用户数。光纤多路电视非常需要光放大器,半导体行波放大管对每路调频是适宜的,对每路调幅则限制频级的最高与最低频率比不大于2。氧化物光纤掺镨可望制成1.3μm光纤放大器。     

Improving the Performance of Sampled-Grating DBR Laser-Based Analog Optical Transmitters

In this paper, the available analog link performance of integrated transmitters containing a sampled-grating distributed Bragg reflector laser, a semiconductor optical amplifier, and a modulator is evaluated. It is found that to provide a link gain and a low-noise figure, an RF preamplifier is required, and for this reason, spurious-free dynamic range (SFDR) including a preamplifier has been evaluated. An SFDR of 110-dBHz^2/3, a noise figure of 5.4 dB, and link gain of 6.9 dB at 5 GHz is obtained. It is further investigated how link SFDR can be improved by linearization techniques. Two novel approaches are proposed and demonstrated: first, predistortion by extraction of nonlinear components from an integrated second modulator exposed to the same wavelength, optical power and temperature for matched nonlinear terms; second, a novel linearized modulator configuration balancing electroabsorption and Mach-Zehnder modulation that can reach a null for both second- and third-order intermodulation products at a single bias point.     

Linearization of Phase-Modulated Analog Optical Links Employing Interferometric Demodulation

We present a linearized phase-modulated analog photonic link that utilizes parallel interferometric demodulation to suppress the third-order intermodulation distortion present in the link. By utilizing two parallel interferometers with different differential delays, we are able to balance the third-order distortion in the output photocurrent and achieve a fifth-order limited link response. We demonstrate shot noise-limited spurious-free dynamic ranges of ~ 130 dB (1-Hz bandwidth) at ~ 1 GHz for a total DC photocurrent I_dc~ 8 mA and ~ 131 dB (1-Hz bandwidth) at ~ 5 GHz for a total DC photocurrent I_dc ~ 7 mA . These results represent a nearly two order-of-magnitude improvement in dynamic range over conventional intensity- or phase-modulated analog photonic links for a fixed received photocurrent.     

Optimizing Optical Transmitters and Receivers for Transmitting Multichannel Video Signals Using Laser Diodes

Analog transmission using laser diodes is quite attractive for transmitting multiplexed video signals, owing to the wide modulation bandwidth of laser diodes. Optimizations for transmitting color-TV signals (7 channel frequency division multiplexed) in the VHF band using buried heterostructure laser diodes are investigated. The major transmission objectives are a carrier to noise ratio of larger than 48 dB and intermodulation products of less than -55 dB. Design curves for minimizing distortion at the transmitter are demonstrated. A modulation index of 70 percent is shown to be capable of attaining the objective. Both the avalanche photodiode (APD) and the pinphotodiode (PD) are considered for use in the receiving amplifier. Minimum receiving power of -11 dBm obtained with the PD receiver is in good agreement with theoretical values. Deterioration of signal to noise ratio due to fiber guided transmissions is also reviewed in comparison with aerial transmissions.     

1550nm光传输系统中的外调制光发射机

本在对1550nm光传输系统性能在分析的基础上，详细阐述了1550nm外调制光发射机设计的原理、方法和注意事项。     

Neural-Network-Based Robust Linearization and Compensation Technique for Sensors Under Nonlinear Environmental Influences

A novel artificial neural network (NN)-based technique is proposed for enabling smart sensors to operate in harsh environments. The NN-based sensor model automatically linearizes and compensates for the adverse effects arising due to nonlinear response characteristics and nonlinear dependency of the sensor characteristics on the environmental variables. To show the potential of the proposed NN-based technique, we have provided results of a smart capacitive pressure sensor (CPS) operating under a wide range of temperature variation. A multilayer perceptron is utilized to transfer the nonlinear CPS characteristics at any operating temperature to a linearized response characteristics. Through extensive simulated experiments, we have shown that the NN-based CPS model can provide pressure readout with a maximum full-scale error of only 1.5% over a temperature range of 50 to 200 with excellent linearized response for all the three forms of nonlinear dependencies considered. Performance of the proposed technique is compared with a recently proposed computationally efficient NN-based extreme learning machine. The proposed multilayer perceptron based model is tested by using experimentally measured real sensor data, and found to have satisfactory performance.     

Improved Large Signal Analysis of the Dual-Wavelength Linearization Technique of Optically Phase-Modulated Analog Microwave Signals

This paper presents simple closed-form expressions, in terms of the ordinary Bessel functions, for the amplitudes of the third- and fifth-order intermodulation products of the dual-wavelength linearized phase modulated link for any scenario of the microwave driving voltage. The results obtained for a microwave driving voltage comprising equal-amplitude two- and three-tones show that the third-order intermodulation can be minimized for values of phase modulation depth less than 0.2 over a relatively wide range of the ratio between the powers in the TM and TE waves of the link. Using these results it is possible to adjust the phase modulation depth and/or the ratio between the powers of the TM and TE waves to achieve a dual-wavelength linearized phase modulated link with a predetermined intermodulation performance.     

Analog/RF Performance of Multichannel SOI MOSFET

In this paper, for the first time, we present a detailed RF experimental and simulation study of a 3-D multichannel SOI MOSFET (MCFET). Being different from the conventional planar technology, the MCFET features a total of three self-aligned TiN/HfO₂ gate stacks fabricated on top of each other, allowing current to flow through the three undoped ultrathinned silicon bodies (UTBs). In other words, the operation of the MCFET is theoretically based on two UTB double-gate SOIs and a single-gate UTB fully depleted SOI (FDSOI) at the bottom. Using on-wafer S-parameters, the RF/analog figures-of-merit of an MCFET with a gate length of 50 nm are extracted and discussed. Thanks to the enormous transconductance (gm) and very low output conductance, the RF/analog performances of MCFET-voltage gain (A _VI) and early voltage (V _EA) are superior compared with that of the single-gate UTB-FDSOI. However, these advantages diminish in terms of transition frequency (fT), due to the large total input gate capacitances (C _GG). This inspires the introduction of spacer engineering in MCFET, aiming at improving both C _GG and fT. The sensitivity of the spacer length to the RF/analog performances is experimentally analyzed, and the performance optimization is validated using ac simulation. This paper concludes that optimized MCFETs are a serious contender to the mainstream MOSFETs including FinFETs for realizing future low-power analog applications.     

一种模拟预失真线性化微波功率放大器

研究了一种新的模拟预失真线性化电路,它由2对工作于不同偏置电压下的反向并联肖特基二极管对以及电容、电阻,3 dB电桥耦合器(Hybrid)、可变增益放大器组成,通过调节二极管对的偏置电压可分别控制产生IM3和IM5信号的幅度和相位。利用专用的微波电路仿真工具ADS进行仿真验证,仿真结果表明在2 GHz频段功率放大器的增益压缩和相位偏移在1 dB压缩点附近分别补偿了1.5 dB和9.3°,双音测试表明,在输出功率为41.8 dBm时,IMD3和IMD5分别改善了26和10 dB。     

多通道模拟监视器件AMC7820的原理及应用

AMC7820是德州仪器公司(TI)推出的专为多通道应用而设计的模拟监视与控制电路。它内含一个8通道12位模数转换器、3个12位数模转换器、9个运算放大器、1个热控电流源、1个内部 2.5V基准和1个SPI串行接口。应用该器件可对光放大器中的泵激光电流和热电致冷器(TEC)以及DWDM(利用光波长进行数据传输)应用中的光功率进行控制和监控，并可大大降低成本。文中介绍了AMC7820的基本原理、管脚功能和应用电路。     

Expected Crosstalk Performance of Analog Multichannel Subscriber Carrier Systems

This paper determines the intelligible crosstalk performance of analog multichannel subscriber carrier systems. Using a 0.1 percent probability of intelligible crosstalk objective, the calculations determine that the equal level far-end crosstalk loss must exceed 55.6 dB. Based on crosstalk measurements of in-service cables in South Central Bell, it is shown that only a small fraction of the pairs fail the crosstalk objective. Hence, it is concluded that multichannel analog subscriber carrier systems can be applied without any cable crosstalk constraints.     

高速传输系统的偏振模色散补偿技术

随着光网络的快速发展,系统的传输码率逐渐提升,传输技术也不断地发展和完善。光纤传输系统中的各种因素造成的影响程度也出现了很大的变化。针对偏振模色散(PMD)对高速光纤传输系统造成的损害,对目前光域和电域的PMD补偿技术进行详细的阐述。通过比较各种方案,指出高速光纤传输系统中PMD的光域补偿技术更适用,发展空间大,而且性能好。其中光纤光栅补偿技术应用广泛,对单信道和多信道传输系统都适用。因此,光纤光栅技术最具发展潜力。     

射频功率放大器线性化技术研究

在当今社会,随着无线通信技术的发展和应用,人们开始追求高功率效率和高频谱利用率。基于此,高效射频功率放大器、线性调制技术等,都开始得到越来越广泛的应用。但是,经过非线性射频功率放大的包络变化调制信号,时常会产生互调失真的情况,会引发较为严重的临近信道干扰以及码间干扰等问题。对此,在对射频功率放大器进行应用的过程中,应当注重采用线性化技术,以确保良好的通信质量。     

Novel Optical Control Techniques for Solid-State Radar Transmitters

New optical techniques for performing the RF control functions needed for such applications as short-pulse and phased-array radar transmitters are described and demonstrated. The techniques utilize optical signals to directly control the internal operation of a solid-state oscillator by the photoexitation of carriers within the active region of the oscillator. Short RF pulse generation is achieved by making use of the subnano-second optical power rise time of a laser diode to rapidly quench the RF output of a microwave oscillator. Phase control of a microwave oscillator is achieved by a phase-locked-loop (PLL) scheme wherein the loop is completed by an optical signal that directly controls the ontput frequency.     

用二元光学技术制作的多通道频谱分析元件

介绍了两种二元光学组合元件：一种是两个线型波带板的组合,其效果相当于两个柱面透镜的组合;另一种是一个线型波带板和一个圆型波带板的组合,效果相当于一个凸透镜和一个柱面透镜的组合。这两种元件在x方向的焦距均为y方向焦距的两倍,如果把物放在此二种元件前fx焦平面处,则在元件后fx焦平面上,x方向可以产生傅里叶频谱,y方向可以产生等大倒像,从而具有多通道频谱分析的功能。给出了制作这两种元件的原理、方法、参数和相应的实验结果。     

光学多道光谱仪的应用

报道了一种新型光学多道光谱仪的结构,光谱分辨率的提高及其在医学,激光器研究,水体及太阳光谱测量等方面的广泛应用。     

多通道光功率自动监测系统的设计

介绍了多通道光功率自动监测系统的组成。该系统最多可以实现16路光功率实时监测,有效地解决了多芯光缆以及多路分支器件在机械和环境试验时的光功率自动监测问题。同时系统中增加的光开关和温度传感器,使系统实现了双波长实时切换以及温度实时显示的功能。系统的稳定度在短时间(15min)优于0.01dB,长时间(8h)优于0.02dB。     

Compensation of Low-Frequency Disturbances by Means of Linearization of the Electronic Systems Characteristic

A mechanism to demodulate a two-tone high-frequency oscillation in nonlinear electronic devices due to an external electromagnetic field is investigated. The results of a demodulation are low-frequency disturbances to the internal circuits of electronic devices. A method for the synthesis of nonlinear compensators on the basis of the operational equations of electronic devices is offered for protection against low-frequency noise. The nonlinear operator of the compensator is designed so that a cascade connection of the electronic device and the compensator is described by the linear Volterra functional. As an example, the compensation of nonlinear transformations of a detector at high-frequency oscillation is synthesized with the use of results of measurements. The accuracy of the executed compensation is estimated.      

DWDM系统光发射机温度控制电路的优化设计

本文提出了一种在激光发射机温度控制电路中提高控制精度，降低功耗，增加集成度的有效方法，给出了波长的热电温度控制原理及测试结果。