Coherent radio-over-fiber (CRoF) approach for heterogeneous wireless-optical networks

A new coherent optical heterodyne radio-over-fiber (CRoF) scheme is proposed for seamless integration of next generation millimeter-wave wireless systems into a (ultra-dense) next generation passive optical network (NG-PON2). For seamless integration with the (ultra-dense) WDM infrastructure of high-capacity and longer-reach NG-PON2 networks, we propose novel radio access units (RAU) using coherent optical heterodyne detection for the generation of the millimeter-wave radio signals. The proposed CRoF concept supports the provision of multiple services over a single optical distribution network including next generation optical and wireless access services and high-capacity fixed wireless links for mobile backhaul. A proof-of-concept experiment is demonstrated in the context of backhauling. An E-band RAU utilizing CRoF is used for converting 2.5 Gb/s optical baseband data after 20 km fiber transmission to a 76 GHz wireless signal. After subsequent wireless transmission over 40 m (limited by the lab environment), the wireless E-band signal is directly reconverted to 2.5 Gb/s baseband data using a low-cost 76 GHz wireless receiver with RF envelope detection. The receiver´s sensitivity is only -47 dBm for a bit error rate (BER) of 2.10^-3. Within international regulations, the transmit RF power can be further increased by about 68 dB, i.e. wireless distances way beyond 2 km can be expected even in the case of rain.