Research On The Generation Of OFC Based On Cascaded Modulators And Spectrum Broadening

Optical frequency comb refers to a series of equally spacing,equal power optical frequency components.Optical combs have important applications in wavelength-division multiplexing(WDM),high-precision ranging,microwave photonics signal processing,microwave photonics arbitrary waveform generation and other related fields.Based on its important application value,optical frequency combing is becoming a hotspot in related fields.First,the general situation of microwave photonics,the development of optical frequency comb and the great role in ultra wide band communication are introduced.Based on the study of optical frequency comb research,a scheme of generating optical frequency comb based on cascade modulators and spectral broadening is proposed.At the same time,simulation and experimental verification are carried out.The main contents of this paper are as follows: the scheme of optical frequency combing based on intensity modulator cascade phase modulator is constructed.The principle of the scheme is analyzed and the specific parameters are obtained by using the relevant formulas.Based on the experimental simulation of Optisystem and Matlab combined with custom IM and PM,the experimental link is established.The experimental results are in agreement with the simulation,and the feasibility of the scheme is verified.The scheme of spectrum widening is constructed by using the generated optical frequency comb as the seeding.Firstly,the basic theoretical of pulse compression and four-wave mixing is introduced,and the design method of precision parameter mixer is analyzed.By calculating the up chirp induced by PM and the down chirp induced by SMF,the optimal length of pulse compression is obtained,and the enhanced pulse peak power will provide sufficient conditions for the four wave mixing in the next stage.The nonlinear optical fiber loop mirror can improve the optical frequency comb flatness.The strain distribution of the nonlinear optical fiber can suppress the stimulated brillouin scattering effect,which lead to the loss of the optical fiber.The nonlinear optical fiber with the dispersion flatness curve is obtained,and the efficiency of the four-wave mixing is improved.The experiment achieves a spectrum broadening of 30 nm,but the overall flatness is poor and the carrier to noise ratio is low.Besides,the local spectrum width of 10 nm is flat,with 100 combs and 5dB flatness.