The Design And Implementation Of Board-level Optoelectronic Interconnects Technology Based On Optical Waveguides

With the rapid development of modern communication technologies,the communication rate of high-speed communication electronic devices has grown exponentially.Due to the inherent physical characteristics of the electrical interconnection method,the parasitic effect of the copper wire at high frequency seriously affects the signal quality.The traditional electrical interconnection method has become a bottleneck restricting the rapid development of the communication system.Optical interconnection is considered as the next generation of communication technology that replaces electrical interconnection.It has the advantages of high bandwidth,large capacity and no electromagnetic interference.Therefore,research on optoelectronic interconnection technology that realizes mutual conversion of photoelectric signals is an inevitable trend of communication technology development.Through the research of board-level optoelectronic interconnection technology based on polymer optical waveguide,the photoelectric conversion communication of four groups of channels on the substrate is realized,and the communication capability of 10 Gbps is achieved.The average attenuation of the optical path is less than 0.3dB/cm.The main research contents and results are as follows: 1.Design a vertical coupling structure with high coupling efficiency to improve the transmission efficiency of optical interconnection layer.Aiming at the low coupling efficiency of the vertical coupling structure in the traditional optical interconnect layer,it is proposed to use a curved surface instead of a part of the plane to avoid the incident angle of reaching the reflecting surface not decreasing with the incident angle of the light source.Ultimately ensure that all incident angles reaching the reflecting surface are greater than the total reflection angle.Theoretically,the optical coupling efficiency is increased from 65% to 100%.2.Design optical transceiver module to realize photoelectric conversion function.In order to facilitate integration,the 6104 series optoelectronic chip is used as the main functional circuit.The digital signal to photocurrent conversion can be realized by the light emitting module HXT6104 with VCSEL array,and the photocurrent received by the HXR6104 is monitored by the C8051 microcontroller in the light receiving module.3.Design high speed signal differential line on PCB to realize data transmission capability of 10 Gbps in the electrical interconnection.Si9000 is used to design the laminate structure and the material,line width and line spacing were determined.The layout of differential lines on Altium Designer and TDR simulation by HFSS show that the differential impedance is 96.2~101.1?.Meet the 10 Gbps communication requirements.4.Design the preparation process of the polymer optical waveguide to achieve optical signal communication capability of optical interconnection.The Epo series material was selected as the core layer and the cladding of the optical waveguide according to the negative lithography process,and SU-8 was used as the photoresist.The preparation process of the optical waveguide is divided into three parts: a lower cladding layer,a core layer and an upper cladding layer by combining a photolithography process and a spin coating process.The flatness of the sidewall of the optical waveguide is optimized by parameters of substrate selection,spin coating speed control and exposure time.The average light decay measured by the insertion loss tester was 0.178 dB/cm.5.Design a 45° reflective surface structure forming process to complete the 90 degree turn of the optical path.Based on the grinding and polishing process,the process is improved by increasing the adhesion of the substrate surface and reducing the curing stress of the optical waveguide,thereby reducing the cracking phenomenon during the grinding process.