Linear automatic gain control amplifier for forward current detection in PAM4 optical receiver

Abstract

The invention discloses a linear automatic gain control amplifier for forward current detection in a PAM4 optical receiver. The amplifier comprises a high-speed signal transmission main path and a low-speed gain control circuit, wherein the high-speed signal transmission main path comprises a trans-impedance amplifier, a variable gain control amplifier, a bandwidth expansion circuit and an outputbuffer stage, and the low-speed gain control circuit comprises a received signal strength detector, a current comparator, a decoder, a control voltage generation module and the like. In order to improve the performance of the whole circuit, the variable gain amplifier adopted by the invention has good linearity and a larger dynamic range. Meanwhile, a bandwidth expansion circuit is additionally arranged between the variable gain amplifier and the output buffer stage, so the bandwidth of the whole cascade circuit is expanded. The whole circuit adopts a feedforward structure, and the input current of the trans-impedance amplifier is detected forwards to generate a corresponding gain control signal, so the response time is greatly reduced.

Description

Technical field [0001] The invention relates to a receiver circuit in optical fiber communication and other systems, in particular to a linear automatic gain control amplifier for forward current detection in a PAM4 optical receiver. Background technique [0002] Optical fiber communication has the advantages of low transmission loss, less susceptibility to the influence of electric and magnetic fields, and high communication capacity of transmission. It has become one of the key transmission technologies in the current information highway. In optical fiber communication, for 100Gbit / s short-distance optical fiber transmission, the NRZ modulation method is currently commonly used. Nowadays, the era of big data and cloud computing has arrived. People's demand for traffic has greatly increased, and a new 4-level pulse amplitude modulation method (PAM4) has been proposed. The difference between PAM4 modulation and NRZ modulation is that 4 different signal levels are used for transm...

AI Technical Summary

Problems solved by technology

Since the current detected by the photodetector keeps changing, the output swing of the transimpedance amplifier varies greatly, which seriously affects the normal operation of the subsequent data clock recovery circuit.

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