Design And Applied Research Of Weakly Coupled Multi-core Fibers

With the rapid growth of the data traffic,the weakly coupled multi-core fiber(WC-MCF)based space division multiplexing(SDM)technique is expected to cope with the capacity crunch of traditional communication systems based on standard single-mode fiber(SSMF).Combined the design strategy with optical properties,the capacity enhancement and novel application of WC-MCFs are investigated by theoretical modeling,numerical optimization,and experimental verification.The main work is as follows:(1)Taking the compatibility with the SSMF and ease of system upgrading into account,the maximum number of independent parallel spatial channels of the WC-MCF with a cladding diameter of 125 ?m is investigated in this dissertation.By the introduction of geometric and stress birefringence,a design of polarization-maintaining(PM)five-core threemode fiber with a cladding diameter of 125 ?m is proposed.Trench-assisted heterogeneous core distribution is adopted in this design to suppress the inter-core crosstalk.Taking both inter-core crosstalk and intra-core mode coupling into account,under condition of inter-core crosstalk less than-30 d B/100 km,it is proved that the PM five-core three-mode fiber is capable to provide up to 19 independent parallel spatial channels without the need of MIMO signal processing.(2)For the purpose of the ease power acquirement and the centralized management for5 G micro base stations(BS),a 5G fronthaul link scheme based on the radio and power over a weakly coupled seven-core fiber(WC-7CF)is proposed and experimentally demonstrated.The 1.5 Gbit/s 5G new radio(NR)signal at 1550 nm and the 60 W energy light at 1064 nm are co-transmitted over 1 km WC-7CF,the total collected optical power of the energy light is 4.6times as much as that of the 1 km SSMF.Meanwhile,the error-vector magnitude(EVM)of1.5 Gbit/s 5G NR signal is 0.28% when the received electrical signal power is-25 d Bm.Moreover,its fluctuation is only 0.01% during six hours.The results indicate that,the WCMCF scheme based on the SDM technique is promising in realizing N times energy light transmission improvement by using N cores of the WC-MCF for energy light co-transmission,in comparison with traditional power over the SSMF scheme based on wavelength division multiplexing(WDM)technique.Meanwhile,the transmission quality of 5G NR signals can maintain excellently under the proposed scheme.