## 2 Materials and Methods
### RoF  
The RoF system is practically well-matched with the technology of WDM, which gives a huge number of the essential BS for covering a wireless service area in arrangements of the Pico- or Femtocell [14]. The demand to have broadband capacity, which applies a pressure on the wireless communication systems for increasing the coverage area and the capacity of the transmission [15]. RoF is an appropriate system because it consumes less power and costs less. This is because the RoF system lets the electrical signal modulate the optical source. Then, the optical signal is propagated through the optical fibre to a remote station. If the RF signal is modulated directly to the optical link, the power consumption will be dropped while the antenna side has carriers with high radio frequency. The cost reduction in RoF technology can be demonstrated in two stations: the first is CS, which provides resources that may be shared by a set of BS; the second is BS, which can only execute simple tasks. Furthermore, the size of BS is smaller, and it costs less. The range of GHz frequency requires extra bandwidth, which gives additional capacity for carrying data. For a wireless data transmission, further losses are encountered in RoF systems, hence no long distance transmission can be performed. Instead, low-frequency signals can be used for long distances which encounters fewer losses. Therefore, there is a need for a waveguide for carrying these signals. In RoF, the CS is connected with many BS with optical fibres. BS functions only to convert an optical signal into a wireless signal and vice versa, whereas CS executes all processes of modulation, demodulation, routing, and coding. The RoF system distributes the RF signal using a high linear optic link between CS and BS. The demand for increasing the capacity and the bandwidth of wireless system, the WDM technique has been employed in RoF systems (WDM-RoF). A wireless network based on RoF  
Figure 1: Wavelength division multiplexing (WDM) configuration. technologies is a practical solution. It acts as a back-end technology for the transportation of microwaves and millimetre waves [16]. Integration of WDM into RoF leads to a significant increase in the coverage area and the overall capacity of the current optical network and offers the benefits of high data rate and increased mobility. A WDM-RoF system is proposed for signal demodulation. This has prevented the need to design and install two separate networks. The universal Internet traffic is increasing at a massive pace and is estimated to keep increasing over the next few years. To support this growth, a future-proof network needs to be designed. This network needs to offer large bandwidth and high data rate in a cost-effective way. If this network can combine wireless and wired facilities together, then, along with high data rate, increased mobility can be achieved [17]. RoF is a technique that combines both wired (optical) and wireless (microwave) networks. An RoF network involves the transmission of RFs over an optical fibre link to support numerous wireless applications. A solution has been proposed by many researchers. [PERSON] et al. [3] proposed a WDM-RoF system transmitting a 1 Gbps downlink and uplink information stream over a length of 25 km with an effectively-factor. [PERSON] et al. [5] proposed architecture for wired as well as wireless systems that was capable of delivering a 2.5 Gbps uplink signal. [PERSON] et al. [11] demonstrated the synchronous transmission of a 1.25 Gbps wired and wireless information stream over a WDM-RoF access system. [PERSON] et al. [17] proposed a blend of SCM and WDM models to ensure vast transmission capacity and a high information rate in cellular communication, particularly between CS and BS. [PERSON] (2014) [18] investigated spectrum sliced dense wavelength division multiplexed passive optical network (SS-DWDM-PON) as a solution for power active and cost efficient in optical access network.