Research On D-Shape Twin-Core All-Fiber Optical Modulator Based On Graphene

Optical modulators are key components in modern optical communication links and towards wide bandwidth,high extinction ratio,low insertion loss,as the information society demands higher transmission rates.In recent years,graphene has become the research hotspot due to its unique band structure,excellent electrical and optical properties.Graphene-based optical modulators have high modulation efficiency,large bandwidth,and easy to integrate features.In addition,all-fiber optical modulators have good compatibility with fiber links,and modulation material interact more strongly with evanescent wave on D-shape twin-core fiber,which is beneficial to improve the modulation efficiency and the extinction ratio.In this paper,the combination of graphene and D-shape twin-core fiber structure is proposed,which realized the double modulation effect of graphene absorption modulation and two core coupling modulation.In this paper,the modulator structure parameters are optimized and the modulation characteristics are analyzed.The main research contents are listed as follows.(1)The research background and status of graphene-based optical modulator are described.The energy band structure,optical and electrical properties of graphene,twin-core fiber transmission are theoretically analyzed.According to Kubo formula,the relationships between graphene conductivity,permittivity,effective refractive index and chemical potential is theoretically derived.The preparation of graphene and D-shape twin-core fiber are introduced in detail.(2)The modulation principle of graphene-based D-shape twin-core all-fiber optical modulator is studied and its theoretical model is established.Based on the model,the effects of modulator transmission mode,the radius of two cores,the distance between two cores,graphene layer number,and transition layer material on modulation performance are analyzed.The research shows that the modulator has better modulation effect in TE mode.The radius of two cores are taken as 2.5μm and 2.8p.m respectively,the distance between two cores is 12μm to reach more conducive coupling modulation.The more graphene layer number the better the absorption modulation effect,the smaller output power.When the transition layer material is h-BN,the modulation efficiency is higher than that of Al2O3.The modulator performance is analyzed,modulation bandwidth is 8.56GHz,extinction ratio is 67.64dB,insertion loss is 1.4dB.(3)Based on the above analysis,the structure is optimized.The structure of two cores are arranged horizontally is simulated,the modulation bandwidth is 37.04GHz,the extinction ratio is 30.37dB and the insertion loss is 1.37dB.When the graphene coating width is reduced to 6p.m,the modulation bandwidth achieved 54.92GHz,the extinction ratio is 22.78dB and the insertion loss is 1.02dB.The effect of the grinding depth of the D-shape twin-core fiber on the performance of the modulator is simulated,the research shows that the larger the grinding depth,the larger the modulator loss and the faster the signal attenuation.Therefore,the adjustment of the structural parameters can improve the modulation performance.The structure solves the problem of compatibility with fiber links and has the advantages of fast modulation speed,high extinction ratio and all-fiber modulation.