Reach extension in 10-Gb/s directly modulated transmission systems using asymmetric and narrowband optical filtering.

Optical filtering has been used to extend the reach of directly modulated laser in 10Gb/s WDM systems via two separate mechanisms: narrowing the broadened spectrum, and converting frequency modulation into useful amplitude modulation. We investigate in detail, the impact of asymmetric and narrowband optical filtering at the transmitter or receiver. Experimental demonstrations for both shorter distance and long-haul like transmission using optical filtering are performed. The transmission reach is nearly doubled from <25-km to >45-km without dispersion compensation. 1400-km error-free transmission (Q > 15.6-dB) is further achieved over dispersion-managed link for a directly modulated DFB laser within an 8x10-Gb/s WDM system.