Utilizing standard deviation to find optimal wavelength of sampling pulse in PPLN based all optical sampling

In all optical sampling technique based on sum frequency generation (SFG) effect in periodically poled lithium niobate (PPLN), a method by measuring the standard deviation (STD) of output light is introduced in order to eliminate the influence of second harmonic generation (SHG) effect of sampling pulse and to realize the automatic selection of optimal wavelength of sampling pulse. With the coupled mode equations of SFG and SHG combined together, the mean value and STD value of output light under different wavelength of sampling pulse are calculated theoretically, which shows the peak of STD value corresponds to the quasi phase matching (QPM) wavelength of SFG. Under such circumstance, the eye diagram is recovered. However, the peak of mean value corresponds to the QPM wavelength of SHG, and the eye diagram cannot be recovered. All optical sampling experimental system is built, the eye diagram of signal is recovered successfully and the mean value and STD value are recorded, which is coincident with simulated results.