Integrated Wireless-pon access Network Architectures Milos Milosavljevic

Chapter 7 Experimental Investigation of WiMAX Transmission over Multi-Wavelength PONs 
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7.2.2 WiMAX over PON Link Implementation 
Four WiMAX channels, forming an FDM window, at the standard 3.5 GHz with 30 MHz 
subcarrier spacing were generated at the OLT. The number of generated WiMAX channels was 
defined by the limitation of the Aeoflex device. Ideally the number of generated WiMAX 
channels should match the passive optical network split and as a result for a targeted 1:16 split 
to comply with current deployments of legacy PONs, a minimum of 16 channels should be 
generated. This assumes that one or more ONU/BSs would require more than one WiMAX 
channels. The 30 MHz subcarrier spacing was chosen to match the Aeroflex receiver filter 
specifications.
To address individual ONU/BSs each WiMAX channel should be shifted in frequency from 3.5 
GHz to any higher value that avoids adjacent channel interference. This was being achieved by 
using a predetermined local oscillator (LO) and BPFs in the OLT. In succession the WiMAX 
channels are combined and modulated onto an optical carrier. At ONU/BS, a LO is required, 
operating at the exact same frequency for a specific ONU/BS to downshift the appropriate 
WiMAX channels. Multiple BPFs are also needed to select each channel prior to transmission 
over the air. 
The formed FDM signals in the OLT are then externally modulating by means of a Mach-
Zehnder modulator (MZM) a commercially available distributed feedback (DFB) laser source.
The resulting signal (shown as inset in Figure 7-1) was then transmitted on 
λ
d1
=1558.1 nm, 
through a circulator and a 16x1 AWG to an ONU/BS, using various lengths of standard single-
mode fibre (SSMF) ranging from 23.2 km to 40.7 km. Having added the various optical 
component losses, including 7.75 dB for the MZM, 1 dB for the polarisation controller and 3.76 
dB for the AWG in the system’s OLT, 0.9 dBm optical power was launched into the fibre. 
Quite importantly if there was a requirement to accommodate legacy PONs over this 

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