Long-Distance Transmission of AM-VSB CATV Systems Using Fabry-Perot Laser Diode and Fiber Bragg Grating

This study presented a directly modulated 1550 nm NTSC AM-VSB CATV longdistance transmission system using Fabry-Perot laser diode, optical isolator, fiber Bragg grating, quarter-split-band, and wavelength-division multiplexing techniques. Good carrier-to-noise ratio ( ≥48 dB), composite second-order ( ≥64 dB), and composite triple-beat ( ≥60 dB) performances were obtained after a 100 km standard single-mode fiber transmission. Our proposed system does not use an externally modulated 1550 nm transmitter and a sophisticated stimulated Brillouin scattering suppression technique. It reveals a prominent technique with simpler and more economical advantages than that of externally modulated 1550 nm transmission system.     

Dispersion Compensation in Externally Modulated Transmission System Using Chirped Fiber Grating

We present an externally modulated NTSC AM-VSB erbium-doped fiber amplifier (EDFA)-repeated system in the 1550 nm region which uses a chirped fiber grating (CFG) as a dispersion compensation device. In contrast to the conventional externally modulated fiber optical CATV systems, either with or without dispersion compensation fiber (DCF), good performances of carrier-to-noise ratio (CNR) S 50 dB, composite second order (CSO) S 74 dB, and composite triple beat (CTB) S 65 dB were achieved for the full channel band after a 100-km single-mode fiber (SMF) transmission.     

Dispersion Compensation in Externally Modulated Transmission System Using Chirped Fiber Grating

We present an externally modulated NTSC AM-VSB erbium-doped fiber amplifier (EDFA)-repeated system in the 1550 nm region which uses a chirped fiber grating (CFG) as a dispersion compensation device. In contrast to the conventional externally modulated fiber optical CATV systems, either with or without dispersion compensation fiber (DCF), good performances of carrier-to-noise ratio (CNR) ≥50 dB, composite second order (CSO) ≥74 dB, and composite triple beat (CTB) ≥65 dB were achieved for the full channel band after a 100-km single-mode fiber (SMF) transmission.     

Improvements in Carrier-to-Noise-Ratio (CNR) of Lightwave Amplitude Modulated Vestigial-Sideband (AM-VSB) Transmission Systems by the Use of Optical Isolators

In lightwave community antena television (CATV) systems as well as other optical fiber communication networks, a transmitted optical signal is known to be degraded by an intensity noise produced within the fiber due to the interference between the signal and doubly reflected light. We report on the improvements to the signal degradation due to the double Rayleigh backscattering by inserting optical isolators in the trunk lines of the systems. A carrier-to-noise ratio (CNR) has been calculated as a function of the number and the insertion loss of the isolators. The calculated results indicate that there is an optimum number of isolators, and if the insertion loss is less than 0.3 dB, the CNR degradation can be restored by more than 60%. To test the calculated results, we conducted experiments for the specific case of employing one isolator, and obtained good agreements between the two.     

Study on EDFA Gain Tilt and Nonlinear Distortion in an AM-VSB CATV Optical Fiber Transmission System

The gain tilt of the erbium-doped fiber amplifier (EDFA) and the nonlinear distortion in an AM-VSB CATV optical fiber transmission system with a cascade of EDFAs are analyzed. It demonstrates that the nonlinear distortion induced by the light source and the EDFA would be counteracted each other to a certain degree as long as the EDFA has a negative gain tilt. As a result,an optimal EDFA negative gain tilt is suggested as a solution to self-compensation of the nonlinear distortion.     

Study on EDFA Gain Tilt and Nonlinear Distortion in an AM-VSB CATV Optical Fiber Transmission System

1IntroduCtionAMVSB(~litUdemodulationwithvestigialsideband)CATVoPticalfibertrandriSSdrisystemiswidelyaPpliedduetocomplete1ycomatibilitywtthekistingCATVtechntheyandoccuPationaverynarrowband.Theopticalpowerbudgetofthesystemistoollttle(about5~8dBm)toreallzealDngdistancetransndssion,andoPticalmodulationdegreeisalsorestrainedinanarrowrangeinordertOguaranteethenonlinearrequlrementssinceitissensitivetOthenonlineardistortion.EDFAisintroducedintothesystemtoimProvetheopticalpoWrbudget.Indongs…     

激光抖动法抑制光纤调幅有线电视外调制传输中的受激布里渊散射

光纤中的受激布里渊散射效应限制了调幅有线电视（ＡＭ ＣＡＴＶ）外调制传输中的最大注入光功率，这对有线电视传输不利的，因而必须采取措施抑制。通过对激光器抖动法进行理论分析，导出了激光抖动法提高受激布里渊散射阈值的公式，实验结果和公式计算是一致的。     

Impact of Laser Linewidth on Performance of Externally Modulated Optical Transmission Systems

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有线电视系统中行波式半导体激光放大器功率特性研究

根据行波式半导体激光放大器的特点，可用输入功率的台劳级数表示放大器的输出功率，只求出级数各阶导数就可以方便地计算在多路有线电视系统中放大器引起的失真。文中出放大器的速率方程组的解，并在此基础上导出理想放大器的前三阶导数的解析表达式。     

空间调制干涉光谱成像仪的星上定标系统稳定性研究

空间调制干涉光谱成像仪对地物光谱辐射信息以目标像元干涉图的形式进行采集,系统定标后,复原的光谱图能定量地反映地物目标实际对太阳光的漫反射特性。分析了空间调制干涉光谱成像仪的定标原理,经计算推导和实验,介绍了空间调制干涉光谱仪的星上定标系统,并进行了实验室光谱测试和航天元件的多种环境测试,解决了空间调制干涉光谱仪星上定标技术的关键组件定标光源、光谱滤光片、积分球组件的技术难点,对定标卤钨灯进行了辐射稳定性测试,光谱滤光片进行了光学性能测试和粒子辐照试验,星上积分球组件进行了环境力学试验和热真空实验,均得到了较好的结果。通过全孔径、部分视场的相对光谱定标,能够得到星上定标光谱和干涉图,在经过不同条件下复原光谱比较后,证明此星上定标系统是稳定可靠的。     

Spectral characteristics of polymer micro-fiber MZI near 1550 nm

The authors have produced the polymer micro-fiber with a highly optical conductive efficiency of 83% and 89% for the pump light of 532 nm and 1550 nm, respectively. The authors constructed a Mach–Zehnder Interferometer (MZI) by a micro-manipulation method and measured the different interference spectra by micro-adjusting the path difference of the dual interference arms of MZI under a microscope. Due to the path difference, the coherent length of the corresponding spectrum continuously and slightly decreases from 20 μm, 13.5 μm, 10.6 μm to 8 μm. The relationships between this particular MZI structure and the surrounding temperature, as well as the refractive index changes can be determined via the evanescent field and the thermally induced expansion or contraction effect, which will be reflected in the interference spectrum.     

Optimization of wide band mesa-type enhanced terahertz photoconductive antenna at 1550 nm

A mesa-type enhanced InGaAs/InAlAs multilayer heterostructure(MLHS) terahertz photoconductive antenna(PCA)at 1550 nm is demonstrated on an InP substrate. The InGaAs/InAlAs superlattice multilayer heterostructures are grown and studied with different temperatures and thickness ratios of InGaAs/InAlAs. The PCAs with different gap sizes and pad sizes are fabricated and characterized. The PCAs are evaluated as THz emitters in a THz time domain spectrometer and we measure the optimized THz bandwidth in excess of 2 THz.     

聚合物弥散液晶材料在1550nm的电光特性研究

实验研究了不同配方及工艺条件下,聚合物弥散液晶（PDLC）材料在1550nm处的电控光透射特性。由此筛选合适的配方和工艺,研制了聚合物弥散液晶电控可调光衰减器样品。实验说明,在1550nm工作点,50％左右合适的液晶含量的聚合物弥散液晶样品能够获得更好的电控光学性能。采用配方质量比ω（DHPA）：ω（E7）：ω（RB）：ω（NVP）：ω（NPG）=100：100：3：2：1．5的配方,制作在1550nm工作的聚合物弥散液晶光衰减器样品。经检测,输入光源为1550mm,223μW时,器件插入损耗为2．3dB,衰减调节范围为13dB,线性工作区域为20～70V。     

偏振保持光反馈下1550 nm垂直腔面发射激光器的非线性动力学特性研究

基于自旋反转模型,研究了1550 nm垂直腔面发射激光器(VCSELs)在偏振保持光反馈下的非线性动力学特性.结果表明:自由运行的1550 nm-VCSELs在电流增加的过程中,发生偏振转换所对应的电流值与内部参数的取值有关,随着有源介质线性色散效应系数γ_a的增大,偏振开关的转换点所对应的电流值将增加;偏振保持光反馈的引入将导致1550 nm-VCSELs中自由运行时的主导模(Y偏振模式)在不同电流下呈现不同动力学状态,引起另外一个模式(X模式)激射,两个模式的平均输出功率随电流的增加总体呈现增加的趋势,但伴随着起伏;反馈时间取不同值时,1550 nm-VCSELs的输出随着反馈强度的增大经历倍周期、准周期或阵发混沌等多种通向混沌的演化途径.     

Waveform shaping of 1550 nm transmission through hollow quartz fiber

In this paper, we connected two single-mode fiber ends with a micron hollow quartz fiber. The hollow fiber was used to modulate the waveform of a 1550 nm light signal, resulting in a lower noise and a narrower linewidth. Specifically, the noise range and the linewidth decreased from 14% to 3% and 0.28–0.23 nm, respectively. The light field distribution and far-field intensity distribution of the hollow fiber are studied using finite difference time domain simulation. Furthermore, we discussed the research suggestions of this configuration in detail. Collectively, these results suggest that it can be used in the fields of optical signal processing, fiber laser and optical sensor.     

Line broadening and shift coefficients of acetylene at 1550 nm

Pressure broadening and shift coefficients have been measured for the ν₁ + ν₃ band of acetylene, C₂H₂, broadened by N₂, H₂, D₂, air, and the noble gases at 295 K. Coefficients are reported for lines between 6470 and 6612 cm⁻¹ (1512-1546 nm). The pressure broadening coefficients are in general agreement with those reported for other vibrational bands, indicating that they are insensitive to vibrational excitation. The pressure shift coefficients, by contrast, are found to differ substantially among vibrational bands.     

在高于253 K温度下的1550 nm波长单光子探测实验

介绍了在高于253 K的温度下,实现红外单光子探测的实验.选用拉通电压较高的雪崩光电二极管（APD）,设计制作了非线性限流技术保护高温工作的APD,利用半导体热电制冷器,在256.8K的温度下,实现了1550 nm波段的单光子探测实验.单光子探测的暗记数率为3.13×10－5 ns,在220 kHz/s的单光子脉冲速率下,探测效率为2.08%.     

基于三种调制模式下的turbo码光无线通信系统分析

从分析大气对光无线通信系统的影响出发,研究了大气信道特性,建立了大气信道信噪比和能见度的关系.为降低系统误码率,提出了基于OOK、BPSK、BPPM三种调制模式的turbo码的编码方案,推导出三种不同方案对应的turbo码迭代MAP算法.应用建立的信噪比关系,分析和计算了基于三种不同方案的系统的误码率.结果表明,基于BPSK的turbo码系统比OOK和BPPM系统的信噪比降低约3dB,且在高的信噪比情况下,BPSK系统能显著降低系统的误码率.因此,基于BPSK的turbo码方案较适合光无线通信系统.     

理论构造周期极化KTiOPO_4晶体制备852和1550nm双色纠缠光

利用KTiOPO4(KTP)材料非线性系数d33对应的二阶非线性0-类准相位匹配,理论上设计构造了一种周期极化KTiOPO4晶体(PPKTP),当晶体温度为20℃时,晶体准相位匹配格子的周期为10.70μm。波长为550nm的激光泵浦由该晶体组成的光学参量振荡器能产生含852nm信号光和1550nm的闲置光的双色纠缠,其中信号光对应Cs原子吸收线,闲置光1550nm对应光纤通讯波长。该纠缠光对量子信息网络和原子信息存储有非常重要的意义。