## 1 Introduction  
Currently, we are witnessing the growth of personal communication demand and the popularity of the broadband services of terminal users, such as the wireless telephony, online gaming, high-quality internet, and digital-TV. All these services are generated in the electrical domain, and their distribution can be accomplished by copper cables, antennas, or optical fibers. It is well-known that optical fibers have outstanding features like a wider bandwidth, a greater information capacity, immunity to crosstalk, immunity to static interference, environmental immunity, lower transmission loss, security, durability, and reliability [1]. Additionally, optical communications systems allow the transport of large quantities of information (expressed in terms of bits per second), with fewer errors, reaching high transmission rates, allowing the encryption of voice, video, and data. [2]. In a parallel way, the implementation of microwave photonic filters (MPFs) in the optical domain has received great attention in recent years by taking advantage of the low-losses, a wide bandwidth, a fast tuning ability, and an immunity to electromagnetic interference offered by modern photonics [3]. All these characteristics have made it such that optical systems are rapidly moving towards the end-users in access networks as fiber-to-the-home (FTTH), fiber-to-the-building (FTTB), radio-over-fiber (RoF), etc. [4]. Nevertheless, the phenomena that limit high speed over a single mode-standard fiber (SM-SF) at 1550 nm are linear chromatic dispersion (CD) and nonlinear-optical-effects (NOE) such as self-phase modulation (SPM), four-wave mixing (FWM), and cross-phase modulation (XPM) [5]. To maximize the system capacity and to minimize degradation due to impairments of transmission, it is necessary to select an appropriate format to modulate the light-wave carrier. The dominant modulation format in intensity-modulated-direct-detection (IM-DD) fiber optic communications systems is non-return-to-zero (NRZ). NRZ exhibits good tolerance to CD due to its narrow optical spectrum. The NRZ format is not sensitive to laser phase noise as it is to phase key shift (PSK) modulation. Additionally, NRZ requires a relatively lower electrical bandwidth for transmitters and receivers than the RZ format, and its configuration is the simplest. However, this modulation format is not suitable for a high bit rate and long distances [6]. The digital signal performance in optical communication systems is affected by some factors such as power levels, modulation format, data rate, optical fiber length, and the number of channels, which are considered for all fiber access network technologies. For instance, in [7], an analysis of a gigabit passive optical network (GPON) was performed with keeping the data rate of 2.5 Gb/s and the link length of 20 km constant by using return-to-zero (RZ), non-return-to-zero (NRZ), differential-phase-shift-keying (DPSK), and differential-quadrature-phase shift-keying (DQPSK) modulation formats. In [8], the performance of the RZ and NR optical modulation formats in terms of the Q-factor, jitter, and bit-error-rate (BER) at a different distance (5 km, 15 km, 25 km, 40 km, 70 km, and 100 km) for wavelength-division-multiplexed (WDM) systems operating at a data rate of 10 Gb/s was analyzed. In [9], the NRZ, NRZ-DPSK, RZ-DPSK, carrier-suppressed-return-to-zero (CSRZ), CSRZ-DPSK modulation formats for a 64 channel 40 Gb/s WDM-PON with dispersion compensation using dispersion-compensation-fiber (DCF) over a 40 km fiber span were evaluated. In contrast to above-mentioned references, where all digital transmission scenarios were realized through simulations, the purpose of this work was to emulate an experimental scenario where the performance of digital signals transmitted over 25.31 km of SM-SF at different data rates (50 MHz, 100 MHz, and 150 MHz) was evaluated. In particular, digital signals were coded on filtered microwave band-pass windows located at 2.1 GHz and 4.2 GHz using a microwave photonic filter (MPF).