## 1 Introduction  
The Visible Light Communication (VLC) systems that use light-emitting diode (LED) technology to transmit the information signal have attracted research and commercial interest during the last few years due to the advantages that they offer [1; 2; 3; 4; 5; 6; 7; 8]. The use of the visible electromagnetic (EM) spectrum, between 400 nm and 700 nm, and the high responsivity of LED lamps offer a high data rate performance suitable for modern networks with high capacity requirements [9]. Additionally, the visible EM spectrum is environmentally and biologically safe and no license is required to use it, while, due to the evolution of semiconductor technology, low-cost and low energy consumption LED lamps are used. All these advantages have identified VLC systems as a highly accessible solution for next-generation communication networks [10; 11], as well as for smart home and smart city applications [12; 13]. However, such systems can be affected by various factors that degrade their performance and most of them are difficult to predict or eliminate. The main factor that significantly affects and decreases the performance of VLC systems is the background noise, which mainly originates from sunlight radiation, and this is the main reason why such communication systems are mostly used for indoor applications [14]. One of the most effective techniques that reduces the sunlight background noise is the appliance of suitable optical filters at the receiver in order to decrease the noise power in the wavelength range that is not used for data transmission [15]. In this work, a low-cost vanadium dioxide (VO\({}_{2}\)) thin film is developed and experimentally investigated in order to be evaluated as an optical band-pass filter in front of the receiver of a VLC system to reject the wavelength range of the EM spectrum, which is not used for data transmission, reducing the background noise. The proposed optical filter consists of a thin densified film of VO\({}_{2}\) deposited on a glass substrate. Its filtering capability utilizes the wavelength dependence of the optical transmittance of metallic phase VO\({}_{2}\). In comparison to other (thin film) optical filters, such as interference (dichroic) filters [16], or other proposed filtering devices [17], it can be argued that VO\({}_{2}\) can be as efficient but, in addition, being a single layer, it is easily fabricated by applying established experimental techniques, making it a more economical choice. Furthermore, the luminous transmittance of pure undoped VO\({}_{2}\) might be favorably employed to a greater degree in the proposed filter as compared to, for example, the application of VO\({}_{2}\) films as shielding layers in smart windows [18]. For this latter application, the presently achieved luminous transmittance of undoped VO\({}_{2}\) thin films scarcely meets the requirements and a great research effort is devoted to the corresponding improvement on an international level. It should, however, be mentioned here that the transmittance performance of the proposed optical filter can further be improved, as will be discussed in Section 2 of the present work. To investigate the performance of the proposed filter, four Red Green Blue (RGB) LED lamps are used in order to deploy a VLC communication system in an indoor environment in the presence of sunlight radiation. The room dimensions employed in the numerical calculations are not exactly the \"typical ones\", but a larger space has been chosen, in order to extract clearer conclusions about the effectiveness of the experimental optical filter under consideration, for the VLC links. The modulation scheme of space shift keying (SSK) which is used has proved to be a very effective technique for increasing the VLC system performance [19; 20]. According to this technique, each LED lamp is active in a specific timeslot, transmitting a different symbol.