| As the society develops and science and technology improve continuously, the amount of information exchange has become larger day by day. Hence, establishing high-data-rate system is a demanding task. Accordingly, optical communication system has developed rapidly, which has been utilized widely for the merits of broad bandwidth and low attenuation. At present, 2.5Gbps optical communication system is under large-scale construction. Optical receiver is of great importance in the entire optical system. In addition, front-end amplifier is the front part of optical receiver, which makes front-end amplifier an even more critical research topic.In this dissertation, a STM-16(2.5Gbps) optical front-end amplifier which is applied to SDH is introduced. This front-end amplifier comprises of preamplifier and limiting amplifier. First, preamplifier and limiting amplifier are briefly outlined and their specifications of performance are introduced. Second, configuration of preamplifier circuit is analyzed in detail. On the basis of previous analysis, an input dynamic range expansion circuit including DC-canceling and AGC circuit is proposed. Third, some wideband techniques applied to limiting amplifier are analyzed, namely, shunt peaking, scalling-down and Cherry-Hooper amplifier. In the end, theoretical analysis of each block in the limiting amplifier is carried out.Upon the study of fundermental theory of preamplifier and limiting amplifier, the following blocks are resonabally designed: RGC TIA, DC-canceling circuit, input buffer stage, cascode Cherry-Hooper amplifier, output buffer stage, offset voltage compensation loop and single-to-double-end circuit. All the blocks as well as the whole system is simulated in 0.18um mixed-signal CMOS technology. Simulation results have showed: front-end amplifier's gain at medium frequency is 116dB, -3dB bandwidth is 2.13GHz, input dynamic range is 40dB, eye diagram is clear with eye largely open. The whole system can stably operate at 2.5Gbps rate. |
PDF Full Text Request