Design Of Optical Coupling System In Active Cable

Active optical cable(AOC)integrates multi-mode fiber optic cable,optical transceiver module and control chip,with high transmission capacity,low energy consumption advantages,is the data center,high-performance computer clusters and other areas of the ideal optical interconnect cable.In this paper,we study the coupling problem between chip cavity type vertical cavity surface emitting laser(VCSEL)and multimode fiber(MMF).Firstly,based on the mode coupling theory,the energy coupling between VCSEL and MMF mode is constructed by overlapping integral method Efficiency mathematical model.(1)When the VCSEL is directly aligned with the MMF,the energy coupling efficiency of the low fourth order transverse mode and the MMF mode field of the communication level VCSEL radiation is calculated.(2)The longitudinal and lateral directions between the VCSEL center and the MMF axis are calculated and analyzed When the VCSEL and MMF are shifted by 7.5μm in both directions,the calculation results show that when the VCSEL and the MMF are shifted by 7.5um,the results show that when the VCSEL and the MMF are shifted by 7.5μm,The coupling efficiency of the two is 50%.When the axial displacement between VCSEL and MMF increases from 0mm to 1mm,the coupling efficiency decreases to 8%.In order to improve the coupling efficiency of chip pallet type VCSEL and MMF,an aspheric lens coupling system with a radius of curvature of 2.549 mm and a center thickness of 2mm was designed by optical software ZEMAX.The actual coupling between the light source and the optical fiber was simulated in the optical analysis software TRACEPRO The simulation results show that when the VCSEL output end face and the MMF incident end face are located at the focal point of the two lenses respectively,the coupling efficiency is 86%,and the VCSEL chip center is shifted by 10 um relative to the axis of the MMF incident end face.Of the coupling efficiency decreased to 56%.According to the simulation system,the actual transmission optical system is built and the relevant data is measured.(1)The coupling between the VCSEL and the MMF is not coupled with the lens system.The center of the two is shifted from 0um to 20μm,(2)The coupling efficiency between VCSEL and MMF is reduced from 84% to 25% when the center of the two is shifted from 0μm to 20μm.The experimental results show that when the coupling pair on time,the design of the lens coupling system to improve the coupling efficiency of both 79%.