WDM NETWORK WITH CONTROL WAVELENGTH

摘要

A wavelength division multiplex communications system has a head station and a plurality of terminal stations interconnected by an optical fiber cable. The head station transmits CW modulated wavelengths ( lambda -1- lambda k), and a signalling wavelength ( lambda 0) which is used to indicate, in each time slot, which wavelengths in the following time slot are available for transmission. Each terminal station is arranged to receive the signalling wavelength ( lambda 0), to determine therefrom whether the next time slot contains any data packets for that terminal station and, if so, to receive the packets. Each terminal station is arranged, if it has a data packet to transmit, to determine from the signalling wavelength ( lambda 0) whether the next time slot already contains data packets for the destination station and, if so, to avoid data collision by not transmitting its own data packet. The terminal station then determines a free wavelength ( lambda t) from the signalling wavelength ( lambda 0), modulates the free wavelength with the data packet it is to transmit, and modifies the signalling wavelength.