基于双音外差的电光相位调制器半波电压自校准测量方法∗
Two-tone optical hetero dyning metho d for the self-calibrated measurement of half-wave voltage of electro optic phase mo dulator
摘要
Abstract
High speed electrooptic phase modulators play very important roles in the high-speed optical fiber communication system, microwave photonic system, and coherent optical communication system, due to their advantages of bias voltage free and linear modulation. As an intrinsic parameter, the half-wave voltage of an electrooptic phase modulator has been characterized by using an electrical spectrum method and an optical spectrum method in the last two decades. The op-tical spectrum method is generally limited by the line-width of the laser source and the resolution of the available optical spectrum analyzer, while the electrical spectrum method requires the conversion from phase modulation to intensity modulation before photodetection, since a phase modulator generates a phase modulated optical signal with constant envelope. The major difficulty in the electrical spectrum method lies in the extra calibration for the responsivity fluctu-ation in the photodetection. In this paper, a novel self-calibrated measurement of half-wave voltage of electrooptic phase modulators is carried out based on the optical heterodyning between the two-tone phase modulated sidebands and the frequency-shifted carrier. The method achieves a self-calibration measurement, and avoids the effect of the responsivity fluctuation in the photodetection by setting a specific frequency relationship between the two-tone microwave signals. Moreover, it extends the measuring frequency range to the double bandwidth of photodetection and spectrum analysis. Compared with the optical spectrum method, the proposed method achieves very high frequency resolution measure-ment, and simultaneously avoids the line-width influence of laser source by use of two-tone heterodyning. Compared with the traditional electrical spectrum method, our method works under no small-signal assumption nor photodetection calibration, and eliminates the limits of electrical driving amplitude and operating wavelength. Moreover, it decreases by at least half bandwidth requirement for the photodetector and spectrum analyzer. Our experimental demonstra-tion shows that the measured half-wave voltages of the electrooptic phase modulator obtained by our method agree well with the data measured by the optical spectrum method, and the two-tone heterodyning method greatly improves the measurement range and frequency resolution. The proposed measurement method provides a very simple analysis method for the microwave characterization of high-speed electrooptic phase modulators, which is also a reference for other optoelectronic devices.关键词
电光相位调制/双音调制/光外差/半波电压Key words
electrooptic phase modulation/two-tone modulation/optical heterodyning/half-wave voltage引用本文复制引用
王恒,张尚剑,邹新海,刘俊伟,张雅丽,李和平,刘永..基于双音外差的电光相位调制器半波电压自校准测量方法∗[J].物理学报,2015,(12):1-8,8.基金项目
国家重点基础研究发展计划(批准号:2011CB301705,2012CB315702)、国家自然科学基金(批准号:61377037,61421002,61378028)、四川省青年基金(批准号:2013JQ0026)、教育部新世纪人才支持计划(批准号：NCET-11-0069)和信息光子学与光通信国家重点实验室(北京邮电大学)开放基金资助的课题.* Project supported by the National Basic Research Program of China (Grant Nos.2011CB301705,2012CB315702), the National Natural Science Foundation of China (Grant Nos.61377037,61421002,61378028), the Science Foundation for Youths of Sichuan Province, China (Grant No.2013JQ0026), the Program for New Century Excellent Talents in University of Ministry of Education of China (Grant No. NCET-11-0069), and the Open Fund of State Key Laboratory of Information Photonics and Optical Communications (Beijing University of Posts and Telecommunications), China （批准号:2011CB301705,2012CB315702）
