Bit error rate and power penalty of optical dpsk communication systems with echo

Abstract

IntroductionIt is known that the bit error rate is deteriorated if there exist echoes on the transmission line. This paper presents a theoretical analysis on influences of an echo on the bit error rate in the optical DPSK communication system. In general, there exists a floor in the bit error rate due to the phase fluctuation of the laser light, which is not reduced by increasing the received optical power. It is shown that the floor value increases with the increase of the amplitude ratio of the echo to the principal wave, as well as the increase of the delay time. It also is shown that the effect of the echo is more remarkable when the bit rate is higher and the spectral linewidth of the laser light is narrower.Finally, the bit error rate is calculated as a function of the received optical power and the power penalty is evaluated. The relation between the bit error rate for which the effect of the echo cannot be ignored and the spectral linewidth is discussed. The features of this paper are that the echo with a small delay time, which has some correlation to the principal wave, can be analyzed.