Research And Design Of Wide Input Dynamic Range CMOS Optical Receiver

Optical receiver is a significant part of optical fiber communication system. It’sperformance directly affects the quality of the whole optical fiber communicationsystem. Nowadays, the volume of information becomes larger and the transfer speedneeds more higher, which put higher request forward the performance of opticalreceiver. Larger bandwidth is needed to transfer higher rate data. At the same time, indifferent links, fiber length and the efficiency of photodetector are different, whichleads to the big change of current generated by photodetector. In this case, a wideinput dynamic range is needed to deal with variational photocurrent. Based on theabove performance request to the optical receiver, two methods are used to increasethe dynamic range of optical receiver on the condition of enough bandwidth in thispaper.The basic structure of optical receiver includes transimpedance amplifier, mainamplifier and output buffer. In this paper, two kinds of transimpedance amplifiers areintroduced and designed. One kind is a simple single-ended common sourcetransimpedance amplifier and the other is a differential common sourcetransimpedance amplifier. Both the amplifiers take active inductance as load in orderto gain larger bandwidth.In the design of main amplifier, a piecewise linear circuit and logarithmicamplifier are used to increase the input dynamic range of optical receiver. Piecewiselinear circuit is a kind of piecewise approximation method. It is linear in each smallrange, then a large linear range can be achieved by connecting them together. In thispaper, the piecewise linear circuit is implemented by multi-tanh circuit and an opticalreceiver with piecewise linear circuit is designed. Logarithmic amplifier is a kind ofamplifier whose input signal and output signal are logarithmic relation. It cancompress signal instantaneously and transform the wide dynamic range signal tosmall range signal that the optical receiver can handle. In this paper, a parallelsummation of limiting amplifiers is adopted to achieve logarithmic amplifier andactive inductor technology is used to improve the bandwidth.In this paper, the circuit is implemented in UMC0.18um CMOS process.Cadence spectre and virtuoso is used for simulation and layout design. The result shows that the optical receiver with piecewise linear circuit achieves2Gb/s datatransmission rate and46dB input dynamic range, while the optical receiver withlogarithmic amplifier obtains2.5Gb/s data transmission rate and60dB input dynamicrange.