Ignacio Enrique Zaldivar Huerta

This work presents a novel high-speed random bit generation approach based on chaotic optical signals combined with a pseudo-random pulse amplitude modulation (PAM) sequence. Chaotic dynamics generated by a laser diode under optical feedback provide the physical entropy source. At the same time, the PAM signal is added as an amplitude-level transformation to enhance the statistical distribution of the digitized signal. Unlike conventional post-processing techniques such as least significant bit (LSB) extraction, which reduce the effective bit rate, the proposed method described in this article preserves the full 8-bit resolution of the analog-to-digital converter improving the distribution of amplitude levels. Experimental results show a significant improvement in compliance with the NIST SP 800-22 statistical test suite. The system operates at a sampling rate of 20 GSa/s, achieving a theoretical bit generation rate of 160 Gb/s. These results demonstrate that the proposed approach provides an alternative to conventional digital post-processing techniques while maintaining high throughput.

Hybrid Random Bit Generators (HRBGs) can generate high-quality random bits by combining physical entropy sources with a computer algorithm. In this work, an experimental HRBG is proposed using chaotic signals from a laser diode under optical feedback as a physical entropy source, whereas a pseudo-random PAM (Pulse Amplitude Modulation) signal is generated numerically by a computer algorithm. The obtained chaotic signals are digitized by an 8-bit ADC (Analogue-Digital Converter) and mixed by adding the pseudo-random PAM signal in amplitude. The randomness of the proposed approach is verified using the NIST (National Institute of Standards and Technology) Statistical Test Suite. The test results demonstrate successful true random bit generation across 1000 tested bit sequences. Unlike the conventional 4-LSB (Least Significant Bit) extraction method, the PAM method retains the entire 8-bit digitized signal. It can be implemented in an all-optical system, offering a promising solution for real-time and high-speed random bit generation.

This paper presents a set of simulations to evaluate the digital data transmission performance of a two-user Fiber-Radio system that shares the same optical and wireless link. For this purpose, at the optical stage, the Optisystem software 21.1.0 is used to simulate the transmission of two digital signals at a bit rate of 2.4 Gbps through a 100 m single-mode standard fiber (SM-SF). To implement the use of a single optical link for two users, the Wavelength Division Multiplexing (WDM) technique is used. Subsequently, the wireless stage is evaluated in MATLAB R2023a by using the NOMA scheme, and the wireless transmission and data recovery are shown and explained in detail. In the wireless stage, four factors that affect the transmitted signal are considered: noise, two types of fading, and Co-channel interference. Performance of the wireless system is evaluated using statistical tests. The simulation set has potential applications in the performance evaluation of Fiber-Radio systems for outdoor environments due to their satisfactory operation at distances of up to 500 m from the transmitting station. Furthermore, the proposed system could be applied to cellular telephony, the Internet of Things (IoT), and sensor signal transmissions for industrial or agricultural uses.

Microstrip filters are widely used in electronics and communications. Designing these filters requires knowledge in communications, microwave engineering, and radiofrequency systems. Specialized software facilitates the design process, often allowing optimization of results; however, such tools typically require expensive licenses, making them inaccessible to many students. While the literature includes some proposals for microstrip filter design, they generally have the limitation of not addressing parameter optimization. This paper presents a GUI (Graphical User Interface) for microstrip low-pass filter design, offering precise and reliable results at the desired cutoff frequency and attenuation, as demonstrated by experimental tests. The key strategy involves systematically following the steps of the classic design process, while simultaneously varying a specific parameter to analyze its impact on filter development. By exploring the variations in different parameters, various insightful analyses can be conducted. One of the notable achievements is the ability to design an optimal filter with a desired total length, while concurrently maximizing the performance of specific parameters. Additionally, this software is compatible with both MATLAB and Octave platforms, ensuring its usability across multiple environments.

Ultra-dense networks (UDN) have become a key technology in future communications systems by deploying a large number of low-power small cell base stations (SBS). However, ultra-dense deployment of small cells in the coverage area of conventional macrocells presents new challenges, such as inter-tier interference (interference between small cells (SC) and macro cells (MC)) and both-tier interference (interference between small cells), which may affect the overall network performance. In this work, in order to mitigate interference, frequency reuse is used. The simulation was performed with MATLAB software based on Monte Carlo methodology for discrete events, with the objective of evaluating the impact of ultra-dense networks within fixed infrastructure wireless networks. The main performance indicators are the Signal to Interference Ratio (SIR) and throughput.

This work presents an optoelectronic instrument designed for wireless visible light communication (WVLC) systems, operating within a wavelength range of 380–750 nm and compatible with standard radio frequency (RF) communication. The instrument encompasses two distinct architectures. The first enables the transmission and reception of RF-processed audio signals through a three-stage process involving RF signal transmission via Bluetooth, signal multiplexing using acousto-optic modulation, a sinusoidal grating, a PIN photodetector array, and final audio playback. The second architecture focuses on the wireless transmission and reception of temperature data, utilizing a similar three-stage approach that includes temperature data measurements with an LM35 sensor, signal processing with Arduino UNO microcontrollers, and information transmission via Bluetooth. Experimental results for both architectures validate the effectiveness of this optoelectronic instrument, demonstrating its capability to integrate RF and WVLC technologies.

It is experimentally demonstrated as an alternative to one of the classical optical heterodyning techniques for generating microwave (MW) signals. The originality of this work resides in the use of a Multimode Laser Diode (MLD) associated with a Fiber Bragg Grating (FBG) and a tunable Distributed Feedback laser (DFB), instead of two DFBs. As an optical filter, the FBG selects a single mode among various provided by the MLD signal. The selected single-mode signal is used as a reference in the optical beating together with the signal of the tunable DFB. The tunability is achieved by varying the DFB wavelength to modify the wavelength spacing () between the two optical signals. The experimental results are corroborated with those obtained theoretically and by simulations. The system performance evaluation is achieved through the Signal-to-Noise Ratio (SNR) and the Phase Noise (PN) measurements

This paper shows the design and implementation of a multimode optical source in the VPIphotonics software. Considering all the powerful features this software provides, the absence of a device such as a multimode source in its library constitutes a limitation for particular simulations. The use of single‐mode optical sources available in the library allows for obtaining a multimode spectrum. The mathematical relationship that describes a multimode optical source is numerically evaluated in MATLAB. Afterward, this graphical result is compared with the obtained in the VPIphotonics software. The importance of using this type of optical source resides in its applications for modern optical communications systems, microwave photonic filters (MPFs), opto‐electronic oscillators (OEOs), and sensors. This implementation aims to drive virtual systems where required, and by setting its parameters similar to the real ones, it allows good studying and understanding of system responses. Even more, it predicts or ensures the results of experimental systems by having the possibility to vary different parameters. A practical application of the obtained multimode optical spectrum is shown with its use in the implementation of an MPF. This last simulation is experimentally corroborated. This work presents a technique for designing a multimode optical source in this particular software and provides also academics and students, with a methodology for the use of this software for this kind of photonic design.

This work shows a set of numerical simulations to evaluate the digital data performance transmission for a fiber-radio system. For this goal, VPI Photonics software is used to simulate the transmission of a digital signal at a bit rate of 2.4 GHz through an optical link of 25 km of single-mode standard fiber (SM-SF). Whereas MATLAB software is utilized to emulate a wireless channel considering four main phenomena inherent to this channel, such as multipath and slow fading, co-channel interference, and additive white Gaussian noise (AWGN). The modeling carried out in MATLAB considers a user in movement within its coverage area cell. The constellation diagram, bit error rate (BER), and signal-to-interference-plus-noise ratio (SINR) statistical tests are used to evaluate the performance of this approach. This proposal finds potential applications in the field of cellular telephony, the Internet of Things (IoT), or any other communication system to evaluate the quality of the delivered signal to a user in motion within a particular coverage cell.

Microwave photonic filters (MPFs) with the capabilities of bandwidth reconfigurability and frequency tunability in the GHz range are of great interest in high-speed communications systems. In this paper, we propose a new reconfigurable multiband microwave photonic filter (MPF) using a tunable Fabry–Perot Filter (FPF). It is demonstrated by numerical simulations that the modification of the intermodal separation (δλ) of a multimode laser diode (MLD) by tunable FPF allows for the reconfigurable multi-passband of the MPF. Our simulation results show that our new filter system is promising to communications systems.