共查询到19条相似文献,搜索用时 62 毫秒
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1引言光纤有着巨大的频带资源和优异的传输性能 ,它是实现高速率、大容量传输的最理想的物理媒质。随着波分复用 (WDM)技术的成熟 ,一根光纤中已经能够传输几百Gbit/s到Tbit/s的数字信息。传输系统的快速增长对交换系统发展带来压力和动力。通信网中交换系统的规模越来越大 ,运行速率也越来越高 ,未来的大型交换系统将需要处理几百、上千Tbit/s的信息。但是 ,目前的电子交换和信息处理网络的发展已经接近电子速率的极限 ,其中所固有的RC参数、钟歪、漂移、串话、响应速度等缺点限制了交换速率的提高 ,这就是所谓的… 相似文献
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This paper describes an electrooptic probing technique using a CW semiconductor-laser beam associated with a fast photodetector. Besides its simplicity, this technique presents some advantages over the sampling one thanks to the presence of a Fabry-Perot effect, namely an enhancement of the electrooptic interaction and a simple solution to the calibration problem. The good validity of the calibration method allows the application of this technique to S-parameter measurements. The S-parameter determination, in modulus and in phase, of an industrial MMIC by the electrooptic method is reported and compared with direct network analyzer measurements 相似文献
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High-speed modulation of an electrooptic directional coupler 总被引:1,自引:0,他引:1
A LiNbO3 :Ti directional coupler driven by an RF signal has been tested at 1.06 μm over a large modulation bandwidth. An analytical model has been developed leading to simple usable expressions to describe the theoretical dependence of the frequency spectrum of sinusoidally modulated light. The frequency response has been measured with a scanning Fabry-Perot and also with a high-speed photodiode. Both methods provided results which are in good agreement. The 9 mm long switch exhibited a 2.5 GHz bandwidth; a 16 dB extinction ratio has been achieved with a driving power of approximately 50μW/MHz. The confirmation of practical modulation response expressions shows the advantage of the optical spectrum observation, which is a very simple measurement method without any bandwidth limitation. In addition, this method has the advantage of remaining quite accurate even for large modulation signals. 相似文献
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The use of slow-wave optical propagation to promote highly efficient electrooptic modulation of light is investigated theoretically. The proposed modulators utilize a traveling wave (TW) design in which a grating integrated with a single-mode waveguide induces coupling between forward- and reverse-propagating waves. This contradirectional coupling leads to a reduction in the average optical propagation speed in the forward direction. The “slow” waveguide structures provide two features which facilitate improved modulator performance over conventional “fast” TW designs: (1) optical/microwave velocity matching in substrates with high electrooptic coefficients and dielectric constants and (2) enhancement of electrooptic phase shift due to the “dwell time” of the light in the modulation region. For the ideal case of perfect velocity matching, these two factors lead to a potential improvement of nearly an order of magnitude in electrical power dissipation over velocity-matched designs in the conventional lithium niobate (LN) substrate material. Additional orders-of-magnitude improvement in the required electrical power could result from the use of tungsten bronze substrates such as strontium barium niobate (SBN), which have such higher electrooptic coefficients than LN. The prediction of a large reduction in electrical power dissipation is confirmed by calculations for specific slow-wave designs utilizing multireflector etalons in SBN, although response speed limitations result from the fact that perfect velocity matching is not achieved 相似文献
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Muller P.O. Alleston S.B. Vickers A.J. Erasme D. 《Quantum Electronics, IEEE Journal of》1999,35(1):7-11
Electrooptic sampling has proved itself as the best technique for the measurement of high-speed electronic signals. This is due to its high bandwidth and noninvasiveness. Standard sampling geometries rely on a rotation of polarization within an electrooptic material and subsequent polarization sensitive detection. In this paper, we present results using a simple technique which relies on Fabry-Perot resonances inside the electrooptic material to produce an amplitude modulation. This simplifies the experiment considerably 相似文献
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Phase modulators utilizing the electrooptic effect in Li-NbO3 are most efficient if the waveguide, and hence the guided mode, is positioned as closely as possible to the modulation electrode which is located at the surface of the crystal. However, placing the guided wave near the crystal surface tends to deform its shape so that the coupling loss between the waveguide mode and an optical fiber is increased. In this paper, we study the tradeoffs between coupling loss and modulation efficiency that result from moving the waveguide further below the crystal surface. 相似文献
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A figure of merit is constructed for broad-band electrooptic modulators which compares bandwidth with launched generator voltage standardized to a common wavelength. Comparison of various published results in terms of this figure shows that a lumped-element III-V semiconductor device performance may be no more than a factor of two below that of typical (i.e., LiNbO3 ) traveling wave devices and are probably easier to implement-especially in an integrated format. Accurate modeling, which incorporates all transit time and velocity match effects, is described and found to agree well with experimental results. Experimental GaAs/GaAlAs modulators have been made, using a Mach-Zehnder interferometer configuration. At a wavelength of 1.15 μm and with unterminated drive a bandwidth of 6.5 GHz was obtained with Vpi of 17.3 V. A shorter (34.6-v) device was ∼ 1.25-dB down at 8.4 GHz. The corresponding figures of merit are close to the maximum expected for the configurations used. 相似文献
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Yifei Li Bystrom M. Yoo D. Goldwasser S.M. Herczfeld P.R. 《Microwave Theory and Techniques》2005,53(10):3121-3129
Future communication systems will require high data rates and flexible modulation. Direct optical phase modulation of two microchip lasers by information-bearing signals allows for high-rate delivery via fiber to a basestation. At the basestation, the coherent optical signals are combined with a reference in a photodetector to produce a microwave/millimeter-wave carrier with arbitrary M-ary quadrature amplitude modulation, which can then be transmitted over a wireless channel. Rapid tuning of the microwave/millimeter-wave carrier, the modulation scheme, and the data rate is achievable through this method with no fixed oscillators at the basestation, thus providing for flexible architectures. Results show a high-quality carrier and, for 4- and 16-QAM, with data rates to 200 Mb/s. Extensions to higher data rates are discussed. 相似文献
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The use of an electrooptical-waveguide modulator to achieve over 80-percent modulation of 7980-Å light from a room temperature laser diode operating at 10 mW CW is reported. The insertion loss of the modulator including couplers is 8.5 dB, and the output beam has high coherence. 相似文献