Repeaterless transmission of eight channels at 10 Gb/s over 137 km (11 Tb/s-km) of dispersion-shifted fiber using unequal channel spacing

Experimental evidence of the effectiveness of a proper allocation of channel frequencies to suppress four-wave-mixing crosstalk is presented by comparing an eight-channel WDM system with unequal channel spacing with a conventional equally spaced WDM system with the same optical bandwidth. Repeaterless transmission of eight 10-Gb/s WDM channels over 137 km (11 Tb/s-km) of dispersion-shifted fiber was demonstrated and error-free operation was achieved over a wide range of input powers using unequally spaced channels. The same system with equally spaced channels could not achieve a probability of error lower than 10/sup -6/. The use of unequal channel spacing allows fiber input power to be increased by as much as 7 dB, which can be translated to a fivefold increase of the bit rate per channel (and therefore of the system capacity), or to an increase of the system length by about 30 km.<>