Based On The Rs Encoder Of The Optical Communication System Design And Implementation

Wireless optical communication refers to the technology of transmmiting data by the means of laser bean. Because this communication method has many advantages such as large information capacity, strong resistance to interference and high communication security, it has good application foreground. At the same time, the technology is in face of the great challenge, because the optical signal will be affected by absorption, dispersion and attenuation in the optical wireless channel. It is necessary to bring in the forward error correction (FEC) to decrease bit error rate (BER) and increase the reliability of communication. Using FEC also could decrease the requisition for the optical output power so as to save costs.Reed-Solomon (RS) code is linear block cyclic codes in the FEC area with the high performance. Because it not only could correct random errors but also could correct burst errors, it is widely used by people in optical communication field. We have studied existing RS encoding and decoding algorithm and have chosen the reformulated inversionless BM algorithm (RiBM) to solve the key equation of the decoder, which is the compromising algorithm between the operation time delay and hardware complexity. Then we have utilized the VLSI design method to map the algorithms to the hardware architecture, and have realized the RS encoder and RS decoder. The decoder works in the fully-pipelined continuous decoding manner. Compared to the Altera's IP Core, the RiBM decoder is better in either size or rate.Having studied the character or RS code, we have chosen the RS(255,239) with code length of 255 bytes and payload of 239 bytes as FEC. Then we have designed and implemented the wireless optical communication system circuit board using Altera's FPGA.The system is composed of transmitter (including data source, encoder and scrambler) and receiver (including frame synchronism modul, descrambler, decoder and BER statistic module). The system supports two transmition rate of 155Mbps and 2.5Gbps.Finally, we make the performance test for the RS code under two communication rate on the experiment platform. We have tested the performance of RS(255,239) code through calculating BER with FEC and BER without FEC. The test result shows that under 155Mbps communication rate and received optical power of -38dBm, using FEC the BER of received data could be encreased from 1.08×10?4 to 2.29×10?10, coding gain is close to 6dB. Under 2.5Gbps communication rate and received optical power of -31.74dBm, using FEC the BER of received data could be encreased from 3.16×10?7 to 4.49×10?10, coding gain is close to 3dB. RS(255,239) code can improve the performance of system with 2~5dB, which is consistent quite well with the theoretical performance.