# Evaluation of the Digital Data Performance Transmission on a Fiber-Radio System
## 2 Optical and Wireless Transmission Schemes  
Figure 2 depicts the block diagram of the fiber-radio scheme proposed in this work. The blue dotted box corresponds to the electro-optic arrangement simulated by the use of the VPI Photonics software. The simulation conditions are a sequence of bits at a BR of 2.4 GHz (sequence used commercially according to the optical communication standards), a distributed feedback (DFB) laser as an optical source emitting at 1550 nm (wavelength used in standard optical communication systems) at an optical power of 2 dBm, a Mach-Zehnder intensity modulator (MZ-IM), 25 km (length commonly used in an urban optical transmission link) of SM-SF whose chromatic dispersion parameter (D) at 1550 nm is 16.75 ps/nm\(\cdot\)km. A photodetector (PD) recovers the modulated optical signal delivering an electrical signal (transmitted bits). From the library of this software, the Laser_vtms, ModulatorMZ_vtms, FiberNLS_vtm, and Photodiode_vtms modules are selected to simulate the DFB (linewidth of 10 MHz), the MZ-IM, the SM-SF (attenuation of 0.2 dB/km, chromatic dispersion parameter of 16.75 ps/nm\(\cdot\)km), and the PD acting as an APD (avalanche photodiode with a responsivity of 0.9 A/W), respectively. The modules PRBS_vtms_1 and Coder_NRZ_vtms1 are used to generate the electrical sequence to be sent. Whereas the SignalAnalyzer modules are used as optical and electrical analyzers to monitor the corresponding signals step by step. Figure 3 shows the diagram corresponding to the electro-optic arrangement simulated in the VPI photonics software. The interface of this software allows the visualization of the results in a graphical manner and export to a file with a \(\cdot\)txt extension. Figure 1: Basic fiber-radio scheme. The green dotted box in Figure 2 corresponds to the block implemented in MATLAB. This block is fed with the data previously obtained from the electro-optical system. Initially, a normalization and debugging process for these data is carried out and subsequently modulated in QPSK format with a 5 GHz carrier signal to satisfy the Nyquist theorem. This format is chosen due to its robustness and because it is currently used in 4.5G and 5G technologies. The resulting modulated signal emulates the signal radiated from the antenna to the environment. Knowing that any propagated electromagnetic signal is subjected to several inherent phenomena typical of this environment, this work considers four main phenomena such as multipath and slow fading, co-channel interference [5], and AWGN [4]. The black dotted box emulates the environment through which the radiated signal travels and where the effects previously mentioned are included. The maximum distance considered between the antenna and the receiver is 500 m. Finally, the resulting electrical signal is demodulated to recover the original data digital signal and displayed graphically. In wireless networks, the coverage area for a mobile user consists of a hexagonal distribution because it provides an equidistant array of antennas, is symmetrical, and supplies full coverage. In this work, a particular case is analyzed involving a wireless  
Figure 3: The layout diagram corresponding to the electro-optic arrangement in the VPI photonics software. Figure 2: Block diagram of the optical and wireless transmission stages. receiver U1 situated within one of the three sectors in the central base station (BS0) cell as is depicted in Figure 4.  
An discrete-event Monte Carlo simulation is carried out to evaluate the performance of the U1 user inside the coverage area. The central cell is surrounded by the nearest co-channel interfering bases (BS1 to BS6) [5]. Mathematically, the modulated signal is treated as follows [13; 14]  
\[Prx=\frac{yh\ell}{d^{\mu}}=\frac{y\ h(10^{\frac{\zeta}{10}})}{d^{\mu}} \tag{1}\]  
where  
_Prx_ is the received power for U1. \(y\) is the total signal emitted by BS0. \(d\) is the distance between BS0 and U1 (the user position is uniformly distributed inside the coverage area).