Radio over fibre distributed antenna networks

Radio over fibre (RoF) has long been proposed as a suitable alternative technology for distributed antenna systems (DAS). In this thesis the concept of optical DAS is extended and improved to the idea of an optical distributed antenna network (DAN) to meet future requirements. Active RoF link solutions are also demonstrated to improve link performance and simplify design. It is shown that modern communication signals can be multicast simultaneously from a number of low power antennas in a DAN to expand the area of coverage without causing “black-spots”. The required output power at each antenna is reduced by 15 dB by using 3 distributed antennas instead of 1. As a result of this finding, it becomes desirable to use many more antenna units in the DAN, and the cost of installation must be considered. Current systems generally use separate antennas for the uplink and downlink to provide isolation. A new active solution to provide isolation requiring only a single antenna when time division duplexed signals are used, based on switching of the downlink laser bias current, is proposed and demonstrated. It is shown to have no negative impact on the throughput of IEEE 802.11g signals while increasing the uplink dynamic range by 10 dB. To meet future inbuilding wireless service requirements, DAN will have to support sensing functions as well as communications. It is shown that RFID signals can be carried on RoF without effecting the RFID performance. A low cost electronic predistortion scheme is demonstrated to allow simultaneous delivery of IEEE 802.11g with an EVM of 3.1% at +15 dBm and RFID signals at +28 dBm over a single RoF link while meeting spurious emissions limits. More advanced network functions such as the ability to dynamically route RF signals will become a key requirement in more complex DANs. Previously semiconductor optical amplifiers (SOAs) have been demonstrated as switching elements in small RoF switches using a single SOA in each path, limiting the number of ports which could be supported. A new switch architecture is investigated using cascaded SOAs. A testbed is demonstrated using 3 cascaded SOAs to simulate part of a 32x32 switch. It is shown that the switch can carry IEEE 802.11g signals with an output EVM of 4% indicating that two such switches could be cascaded achieving a 1024x1024 switch while maintaining an EVM below 5.6 %.EThOS - Electronic Theses Online ServiceGBUnited Kingdo