At the heart of every optical transceiver lie three essential components, often called the “Three Pillars” of optical communication: Laser — generates light. Modulator — encodes data onto the light. Since most lightwave systems employ the binary intensity modulation, we focus on digital optical receivers. As signals travel in a fiber, they are attenuated and distorted, and it is the function of the receiver circuit at the other side of the fiber to generate a clean electrical signal from th l signal to an electrical signal. However, the signal gen-erated by a. than that of an optical Transmitter. Why? Receiver has to detect weak signal. amplitude shift keying (ASK) or on off keying (OOK).