Experimental And Simulation Investigation Into All-fiber Based Wideband Optical Waveform Sampling Systems

All optical sampling is the key technology for high speed optical signalprocessing. It directly samples the waveform profile of the high speed optical signalin the optical domain. Therefore, it requires lower bandwidth of theoptical-electronic conversion, which is expensive and complicated, and overcomesthe traditional “neck of the electronics”. The main advantage of optical sampling isthat it can utilize the mature commercial products with low bandwidth, such as theoptical-electronic conversion module and the analogue-digital conversion module, tocomplete the optical waveform sampling and the measurement of the high speedsignal. It will play an important role in high speed optical communication and highspeed measurement the future. The products of optical sampling can be obtained onthe market aboard in recent years. However, this technique is almost new in China.Most of the research is about the theory simulation and the nonlinear character of thesampling gate. However, experimental investigation is crucial for the practicaloptical sampling system in engineering.This paper is mainly about some of the author’s work in the program ofinvestigating the first optical sampling system in China. In addition, the arithmetic ofthe Q factor is investigated to prepare for the work in the future. Simulation of thefour wave mixing (FWM) effect in the highly nonlinear fiber (HNLF) is alsoinvestigated to improve the performance of the system. During the program, all ofthe work including both the simulation and experimental work is completed by ourteam. Lots of difficulties have been overcome. Many of the key components can notbe bought from the commercial products due to the restriction in China and have tobe investigated by ourselves. We found the solutions and made them stable for theengineering application. Kinds of programs for the whole system were comparedbefore application. Finally, we find the key to success. Valuable experience ispresented in this paper. However, there might be some mistakes due to the author’slimited knowledge. The research work and results are summarized as follows: 1、The high-speed pulse source with a LiNiO3modulator is investigatedtheoretically and experimentally. Simulation results and experimental results togenerate the high-speed pulse train with a repetition of10GHz and40Hz arepresented. Highly nonlinear fiber (HNLF) together with single mode fiber is utilizedto compress the initial pulse from7.8ps to985fs.2、The sampling pulse source with a new style cavity configuration is presented.Passive mode locking is achieved by the nonlinear amplification loop mirrortogether with the semiconductor saturable absorb mirror (SESAM). This pulsesource is compact, stable, and can realize self-start with a low jitter and low pumppower. Further investigation of the vector soliton character in the laser cavity is alsopresented.3、The investigation of the sampling gate is focused on the four-wave mixing(FWM) in the HNLF. Simulation of this effect is completed. Conversion efficiencyof FWM vursus the zero dispersion wavelength of the HNLF is investigated.4、The optical sampling system is experimentally investigated. Rebuilt of thewaveform with a10GHz repetition is achieved with the use of the HNLF. Pulsetrains with a repetition of40GHz and80GHz are rebuilt with the use of the PCF. Theconversion efficiency of the FWM in the HNLF is also investigated to guide theexperiment. The results of the simulation are presented.5、The arithmetic of the Q factor and the software synchronization is presentedbriefly.