| Nowadays,the government is actively promoting plans to deploy gigabit fiber-to-the-home,build 5G base stations,and construct data centers to meet the growing demand for fast and efficient information exchange and data transmission in modern society.High-speed optical transmitters are a critical component of these facilities.However,non-ideal factors such as attenuation and distortion in the transmission channel can cause intersymbol interference and high-frequency attenuation in high-speed data(electrical signals)during transmission.This significantly increases the bit error rate of high-speed data transmission,which can severely impact the quality of the transmission.This article proposes a novel adaptive equalizer to compensate for the high-frequency attenuation caused by different front-end transmission channels in 25Gb/s high-speed optical transmitters.The aim is to improve the quality of high-speed data transmission by effectively mitigating the negative effects of high-frequency attenuation on signal transmission.To address the issues of low adaptability and poor comparison accuracy in conventional adaptive equalizers,the proposed adaptive equalizer employs a dual-loop structure and an adaptive control method based on power comparison.The compensating ability of the adaptive equalizer is automatically adjusted by comparing the power difference between the equalizer output signal and the reference signal output by the loop regulator.During the adaptive control process,1)the low-frequency power comparison loop adjusts the amplitude of the reference signal to calibrate it with the amplitude of the equalizer output signal,thus improving the precision of the high-frequency power comparison loop.2)The highfrequency power comparison loop not only adjusts the boosting factor of the equalizer to compensate for the high-frequency attenuation of the transmission channel,but also optimally controls the high-frequency gain peak of the loop regulation path by adjusting the capacitive load of the loop regulator,thereby avoiding excessive compensation of the reference signal.Furthermore,the key circuit modules employ the passive inductor shunt peaking structure to extend the bandwidth and improve the working speed of the circuit.The passive inductor also adopt the multi-layer stacking technique to save circuit area.This paper focuses on the circuit design,layout design,simulation,and measurement of a 25Gb/s dual-loop adaptive equalizer using Bi CMOS process.The layout area of the proposed dual-loop adaptive equalizer measures 258.13μm × 396.58μm.Simulation results indicate that the dualloop adaptive equalizer effectively compensates for-12.4d B coaxial cable attenuation at the Nyquist frequency of 12.5GHz under the typical condition at 27℃ and TT corner.The jitter of the output eye diagram is restored to 9.04 ps,the vertical eye opening is restored to 76%,and the dynamic power consumption is 21.19 m W.Similarly,under extreme conditions at 70℃ and SS corner,the output eye diagram demonstrates a jitter of 11.62 ps,a vertical eye opening recovery of 52%,and a dynamic power consumption of 20.57 m W,all meeting the design requirements outlined in this paper.Measurement results confirm that after transmitting the PRBS7 signal at a rate of 25Gb/s through a coaxial cable attenuated by-12.4d B@12.5GHz,the high-speed optical transmitter successfully restores the optical eye diagram’s jitter to 11.20 ps,and the eye margin is restored to 26.8%.These results demonstrate the adaptive equalizer’s capability to compensate for high-frequency signal attenuation caused by coaxial cables in high-speed optical transmitters. |
