# Performance Monitoring of Hybrid All-Optical Fiber/FSO Communication Systems
## 2 Simulation Setup Description  
### Simulation Setup  
The simulation setup of the all-optical system that includes the data acquisition system is shown in Figure 1. The simulations are carried out using Transmission Maker 11.1 simulator, which is a powerful tool for modeling and analyzing optical systems and components. The simulator enables us to generate a dataset that includes different channel conditions, which is a difficult task and requires a long measurement campaign to collect such a dataset in real scenarios. Moreover, it allows repeating the measurements under the same channel conditions. The software employs a combination of different simulation techniques, including Finite-Difference Time-Domain, Beam Propagation Method, Finite Element Method, and Eigenmode Expansion Method, to provide a comprehensive solution for the design and simulation of photonic components and systems.  
On the transmitter side, a 10 Gbps on-off keying (OOK) signal is generated and transmitted over a single mode fiber (SMF) that introduced 0.2 dB/km attenuation and has 1.47 group refractive index. A laser diode (LD) emitting 16 dBm average power at 1550 nm wavelength is used at the transmitter to send the data optically over the fiber. The propagated optical signal over the fiber undergoes CD. The CD values vary between 100 ps/nm and 500 ps/nm with 100 ps/nm step size. The CD value is set by changing the value of the CD parameter in the fiber module in the software. To compensate for the signal attenuation in the system, signal amplification using an erbium-doped fiber amplifier (EDFA) is used, which introduces ASE noise. This noise is defined by the OSNR parameter. As the gain of the EDFA changes, the OSNR value changes too. The OSNR values range between 12 dB and 20 dB with a 2 dB step size. In the software, the value of the OSNR is set by changing the OSNR parameter value in the EDFA module. The signal is then transmitted over 1 km FSO channel, which introduces turbulence into the signal, modeled by the Gamma-Gamma model. The amount of turbulence impairment is defined by the index of refraction structure parameter, \(C_{2}^{2}\), with the following values: \(10^{-17}\) m\({}^{-2/3}\) and \(10^{-16}\) m\({}^{-2/3}\) for weak turbulence, \(10^{-15}\) m\({}^{-2/3}\) for moderate turbulence, and \(10^{-14}\) m\({}^{-2/3}\) and \(10^{-13}\) m\({}^{-2/3}\) for strong turbulence. To emulate the turbulence in the software, the \(C_{2}^{2}\) model, which is defined in [22], is used.  
On the receiver side, a data acquisition system is used to build the dataset. It includes a PD, a sampler, and offline processing. The PD is a PIN photodiode that converts the optical signal into an electrical signal. Then, the sampler samples the signal and generates a realization of 8192 samples. Note that, if the received signal power is attenuated due to factors such as geometric loss, fiber attenuation, and channel impairments, and the  
Figure 1: Block diagram of the hybrid all-optical fiber/FSO simulation setup including the acquisition system.  
resulting power level is lower than the receiver sensitivity, the receiver will not be able to detect the signal.  
After data acquisition, the collected dataset is processed offline for training and testing the ML model. The dataset includes 200 realizations for each value of the three parameters. This means the data size includes (200 realizations/value \(\times\)5 values/parameter \(\times\)3 parameters) 3000 realizations. This dataset is divided into 70% for training the model and 30% for testing.