 So far, we have looked at NGN from so many perspectives. A very important aspect is the economy of scales. With regards to the deployment of technologies, fiber optic communication systems exceed any other technology in terms of the economy of scales by far. Therefore, NGNs consider fiber optic communication system to be a very important technology. We'll see how this technology is being adopted as in the fiber to the home architecture. Specifically, we look at the access network perspective of the fiber to the home. In this module, first of all, we shall convince ourselves that fiber optic communication system is the future. Fiber optic communication, if I just quickly recap, is based on the transmission of optical pulses on optical fiber, which is a strand of a material which could be either glass or it could be plastic. This medium replaces the copper based conductors, which have previously been used. Consequently, the telecommunication companies are giving fiber optic communication systems more importance because of the bandwidth availability, which is there in these fiber optic networks. For the last good about 20 years, optical networks have seen immense deployment as regards to network traffic aggregation. For instance, the synchronous digital hierarchy or the synchronous optical networks have been used for serving as the transport networks. However, optical fiber is found to be very, very useful, not only at the back hall or in the transport, but also at the core and the access network. Recently, broadband technology is increasingly being deployed in terms of the last mile optical fiber cable instead of copper. The advantages are, of course, as compared to the electrical conductors. Optical communication is less susceptible to electromagnetic interference since fiber optic cable is now being considered for deployment right at the doorstep. So different architectures are being considered for deploying fiber optic under different conditions. The various architectures for implementation are, they are known collectively as FTTX, that is, fiber to the cabinet or fiber to the curb, fiber to the building, fiber to the home, fiber to the pavement, fiber to the distribution box. In all, these are known as FTTX, but we can conveniently refer to these as fiber to the home. The reason for calling it fiber to the home is that the fiber can be laid from the central office to the location which is closest to the customer premises and from there different hybrid or fiber-based solutions can be provided. The emphasis, however, is, as we initially said, the economy of scales to reduce the overall cost of deployment. It requires significant investments both in terms of time, the physical labor and the cost, of course, because generally there's a thumb rule. The thumb rule is when you consider a technology for deployment, the last mile technology part is the most cumbersome because it involves interaction with the number of users which are interested in getting the service. As a general thumb rule, it says two-thirds of the overall cost, including even the electronics and the server cost, two-thirds of the overall cost goes to the last mile. So you can well imagine that a very cost-effective solution for deploying fiber right at the home is very, very critical. As a makeshift, some solutions have already been there. For instance, a combination of optical technology along with the electrical technology has been used known as the XDSL. XDSL is what combines fiber-optic communication systems with the digital subscriber line technology and likewise, when we integrate or when we dovetail the coaxial cable with fiber-optic cable, it is known as the hybrid fiber coax. In all these, of course, the emphasis is to have a mechanism that reduces the fiber installation cost, including the fiber cost itself. The conversion between the electrical to optical and the optical to electrical domains because it is important to understand that the processing of packets, such as buffering, storage, and the packetization and the scheduling of different packets, is carried out in the electrical domain. So it means the cost considerations must include these as well.