Optical wireless communication represents an emerging and dynamic research and development area that has generated a vast number of interesting solutions to very complicated communication challenges. For example, high data rate, high capacity and minimum interference links for short-range communication, inter-building communication or computer to computer network. In its many applications, optical wireless communication links have succeeded in becoming a part of everyday lives at homes and offices. Optical wireless products are already well familiar, ranging from visible-light communication (VLC), television remote control to infrared data association (IrDA) ports. Optical wireless is also widely available on personal computers, peripherals, embedded systems and devices of all types [1]. Obviously, the data rate, quality of service delivered, and transceiver technologies employed have improved greatly from those early optical wireless technologies, but light emitting diode which acts as optical wireless transmitter has raise fall period which restricts the data rate progress of optical wireless systems and bandwidth exploitation. In this paper, a proposed modulation scheme named interval shift key modulation (ISKM) is introduced to enhance the utilisation of huge bandwidth of optical wireless communication (OWC). MAT Lab is used to build a code to measure the data rate, spectral efficiency and bit error rate which directly related to the performance of OWC. Simulation results are obtained and found in a good agreement with those presented in state of arts.