Integrated Wireless-pon access Network Architectures Milos Milosavljevic

Chapter 8 Project Achievements and Future Work 
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investigations involve no signal transmission over a wireless channel, the upstream WiMAX 
transmitter RCE was set to -25.8 dB to conform to the figure expected to be received at the base 
station in a practical scenario [3]. The resulting optical signal was then routed through the 
corresponding AWG output port to the destination receivers (Rx_Sect.X) in the OLT where 
individual EVMs are measured. 
In order to measure the effect of intermodulation distortion, following their application at the 
MZM RF input, and evaluate the associated degradation superimposed on the received WiMAX 
channels at the ONU/BS receivers, the Aeroflex output power was varied between -2 dBm and 
+14 dBm. To that effect the EVM characteristic of a selected WiMAX channel was drawn at 
the remote antenna input of the corresponding ONU/BS as a function of the MZM RF drive 
power.
Experimental results indicated 40 km downstream transmission with 8-split without any 
dispersion compensation. A justifiable increase in the fibre launch power would allow enhanced 
length-splitting ratios. This is expected to be achieved in a practical network by the optimisation 
of OLT network component losses according to specifications. Comparable results were 
confirmed for all WiMAX channels. The application of directly modulated VCSEL lasers in 
upstream has shown negligible degradation to the received signal in the OLT over 23.2 km of 
fibre with 16 split. Longer fibre lengths were not considered due to the VCSEL output power 
limitation. Taking into consideration that a +0 dBm VCSEL power was launched into the fibre, 
higher output power profile VCSEL arrays readily available are expected to significantly reduce 
the incurred EVM penalties. In that direction, IEEE 802.16-2005 standards compliance was 
demonstrated with EVM figures below -29 dB and -23 dB for 25.2 Mbit/s and 18.9 Mbit/s, 
downstream and upstream respectively alongside 1E-11 BERs for the GPON signalling. 

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