PAM4 signal receiving demodulation circuit applied to high-speed optical interconnection

Abstract

The invention discloses a receiving and demodulating circuit for a fourth-order pulse modulation (PAM4) signal applied to high-speed optical interconnection, and the circuit comprises a trans-impedance amplifier which is used for converting an input PAM4 current signal into a PAM4 voltage signal, amplifying and balancing the high-frequency attenuation of the PAM4 voltage signal, and eliminating intersymbol interference; a level shifter which is used for respectively shifting three eyelets of the PAM4 voltage signal eye pattern to a zero level; a limiting amplifier used for separating an upper eye, a middle eye and a lower eye of the PAM4 voltage signal eye pattern, and converting four-order pulse modulation (PAM4) codes into three paths of thermometer codes; a re-timer used for re-timing the three paths of thermometer codes, eliminating the time delay of the three paths of signals and synchronously inputting the three paths of thermometer codes into the decoding circuit; and a decoder used for realizing XOR logic on the input three paths of thermometer codes, decoding one path of high-order NRZ signal, and directly outputting the other path of low-order NRZ signal by the sampled middle eye signal.

Description

technical field [0001] The invention relates to the technical field of high-speed optical interconnection, in particular to a receiving and demodulating circuit for PAM4 signals applied to high-speed optical interconnection. Background technique [0002] The popularity of electronic devices, high-quality video streaming, automotive electronics, and the Internet of Things has led to explosive growth in global data traffic. In the field of optical interconnection, with the increasing demand for underlying transmission capacity, limited by power consumption and system complexity, traditional multiplexing technology has gradually reached its limit in >25Gb / s ultra-high-speed transmission. Therefore, the next generation of optical transceivers must find another way to improve data throughput. [0003] In response to the above difficulties, introducing the modulation form of fourth-order pulse modulation (PAM4) is an effective method, because it can alleviate the bandwidth lim...

AI Technical Summary

Problems solved by technology

In 2015, Bell Laboratories in the United States developed a 112Gb / s PAM4 optical transceiver based on the 0.18μm SiGeBiCMOS process, and successfully realized transmission on a 2km standard single-mode fiber [1] , but its back-end demodulation module is processed by an analog-to-digital converter, which increases system complexity and power consumption; in 2018, Inphi designed a dual-channel 2×64Gb / s PAM4 transimpedance amplifier based on a 0.13μm SiGe BiCMOS process [2] , which significantly reduces the noise, but it only provides a solution for the front-end circuit of the receiver, and does not carry out the overall design of the receiver

At present, most of the research on PAM4 receiving and demodulating circuits at home and abroad is concentrated on the analog front-end circuit of the optical receiver. Not strong

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