In order to locate the source of a sound in the sea, we can use a series of hydrophones. We can go up to a dozen, more we have, the better accuracy. But when descending to depths very significant (1 km), all wiring becomes heavy. Indeed, each hydrophone requires a pair of wire twisted in addition to other wires when they are equipped with a pre-amplification circuit. Ultimately, the power cable becomes very large and very cumbersome when it comes to the wind, especially if it is deployed over several hundred meters. Thus, our mission is to develop a technique to reduce the diameter of the cable carrying the information captured by hydrophones, priority or other sensors plunged into the sea, to a computer to the surface. The proposed solution is to send each hydrophone signals through an optical fiber. The challenge is therefore to develop a technique to convert signals from several hydrophones and multiplex them through an optical fiber. Then, the signals transmitted are converted into electrical signals to store in .wav format on the hard disk of a computer. The use of an optical fiber is justified by the fact that they can transmit a considerable amount of information thus reducing the number and size of transmission cables. In this paper we will explain the general system architecture including optical fiber transmission system and especially we will show the implementation of the multiplexer and de-multiplexer system on FPGA using MATLAB/Simulink with system generator in Xilinx system.