Integrated Wireless-pon access Network Architectures Milos Milosavljevic

Chapter 7 Experimental Investigation of WiMAX Transmission over Multi-Wavelength PONs 
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7.3 Routing Performance Experimental Results
To establish accurate signal routing to and from an ONU/BS, received EVMs for the WiMAX 
channels and BERs for the GPON signals were experimentally investigated, aiming to confirm 
the routing simulation results produced in chapters 5 and 6.
To that extent, the four frequency shifted WiMAX channels generated prior to MZM 
modulation are initially observed and displayed in Figure 7-3. As expected and based on the 
RCE of the WiMAX channel shown in Table 7-1, the signal to noise ratio at the output of the 
Aeroflex PXI transmitter was 50 dB. The average power for the measurement channel at 4 GHz 
was +0 dBm. However, this power was varied in order to observe the effect of inter-modulation 
distortions due to the use of the MZM.
Figure 7-3: Obtained EVM for 3.5 GHz WiMAX channel at remote antenna downstream
After being modulated on the optical carrier and transmitted over the fibre, the spectrum of the 
combined electrical signal is shown in Figure 7-4 (left). The baseband signal extending up to 
1.25 GHz can be clearly seen populating the corresponding spectrum alongside the up-
converted WiMAX channels at 4 GHz. The power of the received signal before any electrical 
amplification is around -40 dBm. The measured BER of the GPON signal, after being 

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Chapter 7 Experimental Investigation of WiMAX Transmission over Multi-Wavelength PONs 
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transmitted over 23.2 km fibre, was 1E-11, demonstrating error-free transmission for the wired 
users.
Figure 7-4: Electrical spectrum after PIN
Alternatively, 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 (Figure 7-4 (right)) 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. This is 
displayed in Figure 7-5 for varying fibre lengths and network splits to define the maximum 
reach and splitting ratio attainable with a fully passive infrastructure. The plots drawn in Figure 
7-5 confirm in all cases that at low RF drive powers the signal is mainly distorted by noise 
while at high powers, EVM increases due to nonlinear effects.

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