Distributed antenna systems based on radio over fibre technology (fibre DAS) are becoming increasingly popular for providing cellular radio coverage within large buildings such as shopping centres, airports and corporate office blocks. The main limitation with fibre DAS, however, is its lack of flexibility for providing tailored radio coverage in multi-service or multi-operator environments. A new architecture, switched DAS, is proposed for these situations, which leads to both capital and operational cost savings as well as much greater operational flexibility
We report the analysis and application of uncooled, directly-modulated high-speed DFB lasers with emphasis on their analogue transmission performance. Fibre-optic links employing such lasers are shown to meet the most stringent requirements of analogue systems at both high carrier frequencies and high temperatures. Spurious-free dynamic ranges (SFDR) exceeding 100dB×Hz2/3 and 90dB×Hz2/3 and input third-order intercept points (IIP3) above 20dBm and 18dBm are reported for carrier frequencies up to 20GHz at 25°C and up to 10GHz at 85°C, respectively. The error-vector magnitude (EVM) for a 256-QAM modulated signal transmitted over 15km of SMF remains below 1.9% for carrier frequencies of both 2GHz and 5GHz for all measured temperatures. The link performance is assessed by using 3GPP W-CDMA, IEEE 802.11a and IEEE 802.11b signals. In all cases the EVM remains within the standard specification, for fibre-optic link lengths of up to 10km and laser operating temperatures of up to 70°C. Finally, an IEEE 802.11b WLAN demonstrator is presented, allowing antenna remoting over up to 1000m of 62.5/125μm MMF.