A new tunable optical encoder/decoder structure based on holographic optical processor is proposed.The planar holographic optical processor that is a low cost fabrication and that is spatial domain encoding and decoding.The modulating signal for each ONU can take on any form (digital or analog),any rate,and any shape.So this is very suitable for multimedia environment.An impulsive signal entering the input port and interacting with the index grating at special position produces an output signal.Control of the spacing and amplitude of index variations provides required temporal response.For the proposed tunable optical encoder/decoder structure,simulation experiments have been accomplished and a part of typical results are given in this paper.In contrast to the previous structures reported in the literature,the new structure has greatly reduced the hardware complexity,the cost and the power loss.It is easy to integrate.