 The more variants of the FTTH deployment architecture are important to be considered here. The next one after the peer-to-peer network is the active optical network. There is a reason that it is called active because it involves a star topology in which the central switching element is an active device. Let's get back to the text after we have seen the figure. This is the central office with one OLT installed. This OLT is connected to the active switch which is the central device through shared fiber. It is also known as the feeder fiber. The feeder fiber connects the OLT with the active switch. From the active switch to each home are the ONUs. So it means each ONU has a dedicated fiber optic led from the customer premises to the active switch. However, the overall length of fiber from the home or the user premises to the active switch is far less than the peer-to-peer fiber optic deployment that we earlier saw. So it means using this mechanism can significantly reduce the run or the length of cable. So the peer-to-peer links between the remote terminal and ONTs are fiber. However, the multiplexing that takes place between the OLT and the active switch is done in such a way that the active switch sequentially transmits the traffic of every ONU to the OLT. The next deployment is the passive optical network. It is different from the active optical network architecture because in active optical network architecture we saw an active optical switch. Now the active switch required the power supply. The power supply means some kind of mains or main power supply had to be provided to the active switch. But in case of passive switch, we shall see it is passive to give certain advantage. Number one, it is a passive star like we had an active star here in the preceding deployment. Here also it uses peer-to-peer shared links from the ONUs to the passive star at the passive switch and between the OLT to the passive switch there is a feeder fiber. Now there is an important concept called the splitter. The passive splitter is a device that passively splits the traffic coming from the OLT to the respective ONUs in one direction and aggregates the traffic that goes from the ONUs to the OLT. Now we look at the operation of the splitter in couple of slides. Now since the splitting is done without the involvement of any mains power supply unlike the active switch, so there is a likelihood that the more fiber strands which come out of the passive switch to the ONUs would cause the power to be shared I mean distributed and consequently the length of fiber from the passive switch to the ONUs would be significantly reduced. So that is an inherent downside of this mechanism. So this is passive optical network configuration looks like as we have already discussed the splitter is a splitter from the left hand side to the right hand side and it is an aggregator from the right hand side to the left hand side. If you look at the passive splitter it is nothing but the splicing or the interconnection of one input fiber to an array of output fibers. Each output fiber is then going to a specific ONU. So you see that there is a kind of array or some kind of tree that is formed. Now this tree is passive it means we don't see involvement of the electrical supply or the mains power supply here. Now this passive splitter is a device that is the easiest to be deployed. You can see that commercially off the shelf passive splitter arrangements are available from the market in a boxed containment. The last particular type of the deployment is the WDM or wavelength division multiplexed passive optical network. As the name suggests there are more than one wavelength. These wavelengths are carried from the feeder fiber to the respective individual fiber links to respective ONUs. The most natural and obvious reason for having more than one wavelength is to increase the bandwidth. So you see that here from the central office on a feeder fiber we have multiple wavelengths all sharing the same fiber. These wavelengths are non overlapping so there is no interference between them. Each wavelength is carrying a certain user or groups of user data and on the right hand side of the WDM splitter we see individual wavelengths going to individual ONUs in customer premises.