PERFORMANCE EVALUATION AND IMPROVEMENTS OF ARQ SCHEMES FOR OPTICAL COMMUNICATION

The optical communication system can provide highly reliable and large -capacity transmission. It is becoming important as the major technolo gy of highspeed digital communication. In the optical communication sy stem, even though it is highly reliable, inevitably the bit error rate is deteriorated with the increase of the transmission rate or the rep eater distance. It is anticipated that some methods of error control w ill be required in the future. This paper discusses the application of the automated repeat request (ARQ) scheme, which is one of the error control methods, to the optical communication. It is noted first that the error that occurs in the optical communication channel is the tran sition from symbol ''1'' to ''0,'' but it can never be the transition from ''0'' to ''1''. An ARQ scheme is proposed using the m-out-of-n co de which can detect any error in such a channel. A performance evaluat ion is presented based on the throughput and the information efficienc y per photon. It is shown as a result that the SR+GBN scheme is the be st among various ARQ schemes from the practical viewpoint. It combines selective-repeat (SR) and go-back-hr (GBN). Then a new error-detectin g scheme is proposed based on the characteristics of the optical chann el, which can reduce the number of repeats of the codeword. It is show n that, by combining the proposed scheme with SR+GBN, a higher through put can be achieved.