Research On The 2μm All-optical Wavelength Conversion Technology Based On Tapered Fiber

In the field of optical fiber communication,optical signal processing based on nonlinear effects is an important function to support wavelength routing links.As an important device in the wavelength routing link,the wavelength converter is an effective means to alleviate wavelength blocking in wavelength division multiplexing(WDM)-based network systems.Compared with traditional "optical-electrical-optical(OEO)" wavelength converters,all-optical wavelength conversion(AOWC)has a faster conversion speed,a simpler conversion process,and can also handle multiple channels for more flexible operation.In general,there are many ways to implement AOWC.Among them,four-wave mixing(FWM)has the potential to become the mainstream of future AOWC devices due to its transparent modulation format and ability to transmit high bitrate signals.At present,the research on AOWC is mainly focused on the traditional communication band of about1.55μm,while the research of AOWC technology in the 2μm band which is at the edge of the mid-infrared band is relatively rare.However,the conversion efficiency of AOWC in the 2μm band is much lower than the conversion efficiency at 1.55μm because greater nonlinearity is required at this wavelength to balance the dispersion caused by the material and waveguide.Nevertheless,compared with the traditional communication band,the 2μm band has better atmospheric transmission characteristics,human eye safety characteristics and a lower degree of atmospheric scattering,which has great development potential in the field of optical communication.Low conversion efficiency is a major limitation factor for this approach,as most devices exhibit weak optical nonlinearity.In order to solve the above problems and develop a high-efficiency mid-infrared wavelength conversion device,the nonlinearity coefficient of the wavelength converter is further improved by combining a tapered optical fiber with a two-dimensional(2D)material,so as to improve the efficiency of AOWC and expand its operating wavelength range.The specific research content is mainly as follows:1)Research on AOWC conversion characteristics based on FWM principle.According to the amplitude coupling equation,the theoretical transport model of FWM is established,and the analytical solution and numerical solution processes are carried out for the theoretical model.Then,according to the obtained results,the factors affecting the conversion efficiency and the specific process of conversion are mainly analyzed.2)Preparation of tapered fiber based on 2D materials.Firstly,the transmission characteristics of the light field in the tapered fiber waist region were numerically simulated,and then 2D materials-graphene oxide(GO)and MXene were prepared.The properties of the prepared materials such as X-ray diffraction,Raman spectroscopy,light absorption spectroscopy and scanning electron lensing were characterized.After that,the tapered optical fiber was successfully prepared by the hydrogen-oxygen flame tapering machine,and it was used as a waveguide for carrying 2D material.After measurement,it was found that the insertion loss of the medium was only about 1d B.Finally,by optical deposition method,the 2D material was transferred to the waist region of the tapered optical fiber to form a composite waveguide,and its loss is increased to 4d B.3)AOWC experimental study operating at the 2μm band.In the initial experiment,a wavelength converter operating at 1.9μm was successfully set up,which achieved a conversion efficiency of-45.52 d B and a tunable wavelength spacing of 6nm.For the stability characteristics,the experiment measured that the conversion efficiency fluctuated by ±0.41 d B in 2 hours,indicating that the device can operate stably for a long time.In subsequent experiments,the conversion efficiency of AOWC was successfully improved by combining highly nonlinear optical fibers and two-dimensional materials with taper pull.Experiments show that the conversion efficiency can reach-27.22 d B at an amplification power of 28 d Bm,and the adjustable range of wavelength interval is also about 17 nm.