Abstract

Standard optical fiber communication systems employ intensity-modulation/direct-detection schemes. This is noise-carrier communication and in a sense is more primitive than the radio engineering in Marconi’s age. However, it has the practical advantage of system simplicity and low cost. On the other hand, some applications of optical fiber communication exist in which a long repeater separation is the primary concern; an example is submarine optical cable communication between islands, in this case, the improvement of the bit-error rate (BER) by a coherent modulation/demodulation scheme such as PCM-PSK or PCM-FSK may be advantageous even at the sacrifice of simplicity and low cost.

© 1981 Optical Society of America