digital signals and then to be displayed on the screen by certain software. The benefits got from interface personal computer with the environments are:high speed in processing, low cost of (PC), high degree of reliability in (PC),availability of external storage medium and availability of input and output devices .There are three methods for connecting computer with the out side word:Serial interface, direct interface, and parallel interface.A serial communication is the technique that allows one computer to beconnected to another device by sending data through a transition media and receivingdata on another and has a great importance because of its flexibility. Various devicessuch as plotter, modem, mouse and of course a printer can be connected to the serialinterface.The common type of the direct interface is the plug in card, which fits into afree expansion slot in the computer, and its main advantages are: low cost, high speed,and easily connected.Finally, the parallel interface is quickerand cheaper. It works by sendingdata through collection of eight wires at once, unlike the serial interface, parallelinterface can send an entire byte of data at once by using eight data wires.
For all these advantages of PCand optical fiber, recent work was concentratedon the construction of parallel interface circuit for the use of optical fiber system.MATERIALS AND METHODSThe Optical Fiber System:consists of a light sourcewhichis a cw laser diode:manufactured by Phillips Company, with optical power of 5 mw, wave length of 0.67μm, which is corresponding to the aperture of the used optical fiber with low loss,and it also corresponding to the response of the used optical detector. It is pumped bycurrent flow through the device. The Optical Fiber:Is a single mode polymethylmetacrylate (PMMA) Fiber, which hassuitable characteristics for diffusion of light, low cost and also has a little attenuationat the wavelength of 0.67 μm.The Optical Detector:Is a PNdetector, which is suitable for the wavelength of the laserused. A suitable electronic circuit is design and built to operate this detector.