The front end of a receiver consists of a photodiode followed by a preamplifier. The optical signal is coupled onto the photodiode by using a coupling scheme similar to that used for optical transmitters; butt coupling is often used in practice. In the intensity-modulation/direct-detection (IM-DD) system, the intensity modula-tion means that information is carried only by the intensity or power of the transmitted lightwave, not by its frequency or phase. In this design the power supply used by authors is 1. high-performance, low-cost optical links. Paul Cheng Po Chen was born in Yunlin, Taiwan, Republic of China, in May 1983.