Studies On All-optical Regeneration And Wavelength Conversion Based On Dispersion Flattened Highly Nonlinear Fiber

With the development of communication technology,all-optical network based on wavelength division multiplexing has become a research hotspot.In the all-optical network of wavelength division multiplexing,there are two problems need to be solved urgently:(1)Due to some factors such as fiber loss,dispersion,nonlinearity and optical amplifier noise,the quality of optical signal will be degraded significantly.(2)Since the number of available wavelengths is significantly less than the number of nodes and users,it will cause wavelength competition,system congestion and bandwidth waste.So regeneration and wavelength conversion are necessary for optical signal.At present,there are two ways,namely optical-electrical-optical mode and all-optical mode.The former is mature,but it faces the problem of “electronic bottleneck”;the latter processes the optical signal directly in the optical domain,optical-electrical-optical conversion is not necessary,it can greatly save costs.In this paper,all-optical 2R regeneration and wavelength conversion based on nonlinear fiber optics is carried out by theoretical analysis,numerical simulation and experimental study.The main researchs are as follows:(1).All-optical 2R regeneration based on self-phase modulation(SPM)and offset filtering is carried out,the effects of optical signal input power,dispersion of optical fiber,the bandwidth and center wavelength of filter on system regeneration performance are studied.A cascaded wavelength-invariant all-optical regeneration scheme based on semiconductor optical amplifier(SOA)and dispersion flattened highly nonlinear fiber(DF-HNLF)is proposed.This scheme can keep the wavelength of the regenerated optical signal unchanged,and further improve the quality of regenerated signal.A scheme for realizing all-optical 2R regeneration by using slow light enhanced nonlinear effects is proposed.It is expected to realize compact and integrated all-optical regeneration system.(2).The polarization insensitive wavelength conversion schemes based on four-wave mixing(FWM)are studied,namely co-polarized dual pump scheme,orthogonal dual pump scheme and polarization diversity scheme,respectively.Theoretical analysis and simulation verification of each scheme are carried out in detail.Wavelength conversion of optical signals with different modulation formats are implemented by using FWM and transparency to the modulation format is verified.The wavelength conversion experiment is carried out by using FWM in DF-HNLF,the polarization sensitivity of FWM is verified.And the polarization diversity scheme is used to effectively reduce the polarization sensitivity of the FWM wavelength conversion.(3).The soliton self-frequency shift in a single-mode optical fiber is studied by numerical simulation,it is found that the soliton self-frequency shift increases with the increase of soliton peak power and nonlinear coefficient of transmission fiber,and decreases with the increase of soliton pulse width and group velocity dispersion.The soliton self-frequency shift in a single-mode optical fiber is studied by experiment.By adjusting the peak power of the soliton,continuously tunable self-frequency shift with center wavelength from 4.29 nm to 35.60 nm is achieved.The effect of group velocity dispersion on the self-frequency shift of soliton is verified,the experimental results are basically consistent with the numerical simulation.