High Speed Optical Signal Measurements Based On Optical Sampling Technology

ABSTRACT:High-speed signal measurement is en effective means to ensure the reliability of ultrahigh-speed optical network. Traditional electronic instruments are limited because of electronic bottleneck. Optical sampling measurement technology extend the bandwidth of conventional sampling technology, it is indeed an effective way to measure high-speed signals. The optical sampling technique is a key technique in optical oscilloscopes, all-optical analog-to-digital conversion and ultrahigh-speed signal processing. In this paper, we focus on the ultrahigh-speed signal measurement based on optical sampling, theoretical study was carried out.The main work of this thesis can be listed as follows:1. Principle and scheme of optical sampling technique are summarized. The principle of frequency-shift optical sampling is expounded. Moreover, synchronous sampling, asynchronous sampling and software-synchronized sampling are analyzed and compared. Several key technologies of optical sampling are discussed. The standards of sampling pulse source are explained. In addition, linear sampling, nonlinear sampling, clock recovery and photoelectric detector are introduced.2. Subsection model of SOA-XGM is built and the model of SOA-FWM is deduced. In order to meet the condition of injecting lower gain and strong-short pulse into SOA, the free-carrier absorption is considered in the model of SOA-FWM. Simulation models of SOA-XGM and SOA-FWM are demonstrated. Optical sampling gate is achieved via logic AND of nonlinear effect and the simulation results are discussed. The effect of XGM in SOA caused by the input optical power is analyzed. The effect caused by the pulse width to SOA-FWM pattern effect is studied, and the results show that:the larger duty ratio, the more serious of the pattern effect.3. The theories of XPM and FWM in nonlinear fiber are studied. Simulation models of FIBER-FWM and FIBER-XPM are demonstrated and the simulation results are discussed. The effects caused by dispersion to XPM are analyzed and the effects cause by dispersion coefficient and fiber lengths are discussed.4. Numerical simulation of lOGbit/s optical signal measurement is achieved via synchronous sampling and software-synchronized sampling. The circuit of photoelectric detector is designed and software-synchronized algorithm is realized. Eye diagram reconstruction and clock extraction are realized by the algorithm of BTDT. Finally, the effects caused by the time jitter and pulse width are discussed. A scheme is discussed to eliminate the pattern effect.