Signal Transmission Performance at 1550nm Using Directly Modulated VCSEL over G.652 and G.655 fiber links

Abstract

We experimentally characterized and optimized the performance of a vertical cavity surface emitting laser (VCSEL) in a communication link. VCSEL at 1550 nm transmission windows was chosen for data rate of 10 G bps for metro networks due to its wavelength tune ability, cost and energy efficiency. The optical link was evaluated through Bit Error Rate (BER) measurements for17 km over G.652 traditional fiber and compared to 24.69km of Single Mode Fiber-Reduced Slope (SMF-RS) at 5.5m A bias current. The corresponding eye diagrams at telecommunication BER threshold of 10-9 were captured on the scope. The BER for the two measurements were then compared. Transmission over 24.69 km on G.655 SMF-RS was achieved with a penalty of 1.39 dB with respect to B2B. The G.652 fiber at 1550 nm yields non optimal performance due to its high dispersion coefficient of 17 ps/(nm.km) and this therefore provided a better platform to compare performance of the two fibers. The maximum transmission distance of 74.91 km was achieved over G.655 fiber with a penalty of 0.717 dB with respect to Back to Back (B2B). At transmission distance of 24.69 km a power penalty of 0.131 dB was incurred while at 49.42 km a power penalty of 0.391 dB was incurred. This therefore proved that shorter distances yielded better results which ware observed with high receiver sensitivity. Therefore, with the increase in distance high power is needed to compensate for dispersion effects. This study is vital in enhancing awareness on the effects of CD on the already laid fibers and hence looking for methods to mitigate the effects for the next-generation optical fiber networks. Keywords: VCSEL, BER, CD