This project report describes the design and construction of the optical transmitter. The transmitter is intended for use in atmospheric optical transmission network with transmission range of 100 meters or more at data speed of 10 Mbps. This report begins with a review of the optical communication system with emphasis on the use of atmosphere as the transmission medium. A detail discussion of the techniques involve in the transmitter design is given, and the advantages and disadvantages of each techniques is highlighted. In the present work, a transmitter circuit which consists of logic interface, current switch and driver is designed. High speed current switching is achieved using a circuit operates on emitter coupled logic concept. The maximum data transfer is determined from the system rise time. Lens is used as optical antenna to transmits light at a greater distance. Transmitting range is determined by the light source and lens diameter used. Various types of LED have been tested in order to determine their suitability for use as the atmospheric optical transmitter. Maximum data rate of 14.8 Mbps is finally, the report discuss several recommendations to improve the transmitter circuit performance such as using a high optical power and smaller rise time and using a bigger lens diameter. Some of the potential applications of atmospheric optical system is also discussed.