Hi Jamal,
You are correct that the sample file called “BPON Bidirectional” uses WDM to transmit data to users, but it is also a PON type network. A passive optical network is a telecommunications network that uses unpowered optical splitters to enable a single optical fiber to serve multiple users (this is heavily paraphrased from the link http://en.wikipedia.org/wiki/Passive_optical_network).
You’ll notice at the link provided they mention that time division multiplexing is most often used in these types of networks, but that doesn’t remove the possibility of other types of access systems (like WDM). You could also have a combination of WDM and TDM, mode division multiplexing, or code division multiplexing etc.
A passive optical network does not have to be time division multiplexed.
Hope this clears it up!