Fiber optic transmitter is applied to transmit a variety of analog and digital signals. In a typical fiber optic communication system, a transmitter and an amplifier are coupled together to produce and amplify a signal to be transmitted over a long distance. Hence, fiber optic transmitter is one of the key components in the fiber optic networks. Fiber optic transmitter contains an LED or laser source, and signal conditioning electronics, to inject a signal into fiber. The modulated light may be turned on or off, or may be linearly varied in intensity between two predetermined levels. Light Emitting Diodes (LEDs) have relatively large emitting areas and as a result are not as good light sources as laser diodes. When it concerned to the economical factor, fiber optic transmitter is quite suited for short to moderate transmission distances. Laser diodes are able to couple many times more power to optical fiber than LEDs. They are mainly used for areas that need the transmission of signals over long distances.