10-Gb/s Upgrade of Bidirectional CWDM Systems using Electronic Equalization and FEC

We discuss options for upgrading coarse wavelength division multiplexed (CWDM) optical access links over standard single- mode fiber (SSMF) by increasing per-channel data rates from 2.5 Gb/s to 10 Gb/s. We identify electronic equalization and forward error correction (FEC) as the enabling technologies to overcome the dispersion limit of SSMF. In addition, we show how FEC enhances the tolerance to in-band crosstalk, and paves the way towards fully bidirectional CWDM transmission. Due to the lack of CWDM sources rated for 10-Gb/s operation, we demonstrate full-spectrum (1310 nm to 1610 nm) 10-Gb/s CWDM transmission over standard-dispersion fiber using uncooled, directly modulated lasers specified for 2.5 Gb/s. All 16 CWDM channels could be transmitted over more than 40 km, yielding a capacity-times-distance product of 6.4 Tb/s/km. The longest transmission distance (80 km) was achieved at 1610 nm, equivalent to 1,600 ps/nm of chromatic dispersion.