UMTS radio-over-fiber pico-cell interconnection employing low-cost VCSELs and multi-mode fibre

This paper investigates experimentally the suitability of low-cost vertical cavity surface emitting lasers (VCSEL) for radio-over-fibre transmission of UMTS signals. Three directly-modulated VCSEL configurations are investigated: Multi-mode VCSELs operating at 850 nm and 1300 nm respectively in multi-mode fibres (MMF), and single-mode VCSELs operating at 1310 nm with standard single-mode fibre (SSMF). In the later case, the performance of directly-modulated distributed-feedback (DFB) lasers is also reported for comparison. The experimental results demonstrate that UMTS radio-over-fibre is feasible at distances exceeding 1 km and 2 km on MMF with multi-mode VCSELs operating at 850 nm and 1300 nm, respectively. Transmission distances exceeding 25 km can be obtained with the single-mode VCSELs in SSMF. In this later case, the transmission performance is comparable to a directly-modulated distributed feedback laser source, but at much lower cost.