# Upscaling Customer Access Network Using Spectrum Conversion-Slicing-Duplication Technique
## 1 Introduction  
GIGABIT-class passive optical networks (PONs) are currently being deployed in many countries because they have significantly higher capacity than traditional copper-based access networks. These networks allow for the delivery of broadband services, such as voice-over internet protocol (VoIP) and video on demand (VoD). There are two main gigabit-class PONs, the ethernet PON (E-PON (IEEE802.3 ah)) and the gigabit PON (G-PON (ITU-T G.984)), which are standardized by the Institute of Electrical and Electronics Engineers (IEEE) and the International Telecommunications Union's Telecommunication Standardization Sector (ITU-T), respectively. In both standards, service is provided using time division multiplexing (TDM) technology, in which a point-to-multipoint (P2 MP) connection is established between one optical line terminal (OLT) and several optical network units (ONUs). In an E-PON network, service is provided by one OLT over a 10-20 km feeder fiber to 16 ONUs, and 1 Gbp is symmetrically specified for the downstream and upstream traffic. In a G-PON network, service is provided over a 20 km feeder fiber between 1 OLT and 64 ONUs using asymmetric data rates of 2.5 Gbps for the downstream and 1.25 Gbps for the upstream. Because gigabit-class PONs provides an improved bandwidth segmentto each user compared with the copper-based access networks, they were envisioned as the ultimate solution to the problem of increased bandwidth demand. However, their capacity has been exhausted because of the newly developed high-bandwidth-consuming services, such as high-definition television (HDTV) and 3D television (3D-TV), as shown in Figure 1. For example, 10 Mbps is required to support a single HDTV channel, in addition to the bandwidth required for data and voice [1]. Thus, advancing from the gigabit-class PONs to next-generation optical access networks (NG-OANs) was inevitable. In addition to the high-speed requirement, the NG-OANs should overcome the other limitations of existing PONs, such as the low capacity, limited reach, and restricted mobility. Different architectures have been proposed in the literature to create an NG-OAN scheme that is able to satisfy particular sets of these limitations [2; 3; 4; 5]. Significant effort was invested to unify the design of the ONU for the proposed colorless ONU, based on applying different techniques, such as injection locking, wavelength seeding (remote modulation), spectrum slicing, and wavelength tuning, so that each ONU is assigned a different wavelength [6]. The scalability feature refers to expansion of an optical access network to accommodate many users without compromising the bandwidth allocated [7]. A long-reach optical network is also a part of the scalability, in which the optical signal is converged to support long-range end users [8]. Most operators do not consider FTTH to be viable. They would rather extend their existing infrastructure. When rolling out a new network, the digging cost will play a decisive role, especially in rural areas. Important value is placed on the Capex cost per home passed (HP) [9]. Reducing the digging cost can significantly improve FTTH rollout. Combining digging works with planned road works, and using existing ducts with micro-pipes, are good ways to limit the digging cost. P2P technology is more expensive than P2 MP if we able to reduce of the price of the digging cost, OLTs and ONUs. The world has seen the incredible growth of the internet as a global means of communication. The FTTH network that we use today can reach only up to 256 users with the use of WDM Demux and an optical splitter with the ratio of 8 \(\times\) 32 [10]. The first stage of research can expand that figure up to 6144 users with the addition of a new component in the network, AWG, with the latest ratio of 6 \(\times\) 32 \(\times\) 32. Then, the research continues to increase the scalability of the network with several additional components, which then expands the access of the users up to 196,608 users.