# OpticalTrust: A Sensor-to-Blockchain Framework Using Free-Space Optical Communication
## 1 Introduction  
The dynamic field of telecommunications continues to undergo transformative changes, particularly in data transmission technologies. Traditional residential and commercial networks relied heavily on copper-based infrastructure for phone and internet services [1]. This push for innovation aims to overcome the constraints of traditional copper infrastructure and meet the growing demand for amplified data quantity transmission rates and enhanced network performance. Among these, wireless transmission technologies--including both radio frequency (RF) and FSOs--have proven to be strong options [2, 3]. FSOs uses open space to transmit light beams, which creates a channel for data interchange [4]. Modern FSOs systems aim to achieve high transmission rates, while conventional optical fiber systems can already operate at bit rates of up to 40 Gbps with proper design, primarily limited by electronics rather than the optical technology itself [5]. FSOs demonstrates superior agility in establishing connections for both unicast and multicast configurations, outpacing legacy technologies such as Radio over Fiber (ROF) and traditional optical fiber systems [6]. FSOs systems achieve full-duplex communication throughindoor-deployed optical transceivers with integrated laser transmitters and receivers, offering the dual advantages of eliminating RF radiation risks and avoiding extensive underground cabling while maintaining optimal resource utilization through its high-capacity spectrum [3; 7; 8]. Simultaneously, with these advancements, sensor networks have become a crucial element in the changing paradigm of data transmission technologies. These networks comprise globally dispersed independent sensors that observe physical or environmental variables and collaboratively transmit their data over the network to a central hub [9]. Sensor networks can be seamlessly integrated with FSOs and other data transfer technologies to create robust, intelligent systems for data collection and transmission. For instance, in smart city applications, sensor networks can gather real-time data on traffic patterns, air quality, and energy usage, which can then be rapidly transmitted via FSOs links to central processing units for analysis and decision-making [10]. This synergy between sensor networks and advanced data transfer technologies like FSOs is paving the way for more efficient, responsive, and interconnected systems across various domains, from environmental monitoring to industrial automation [11]. In addition to these advancements in data transfer and sensor technologies, blockchain has emerged as a transformative force in securing and managing data across networks. Blockchain technology, with its decentralized and immutable ledger system, offers a novel approach to enhancing the security, transparency, and efficiency of data management in FSOs and sensor network systems. Images obtained by optical spectrum analyzers are crucial for guaranteeing the dependability, efficiency, and sustained prosperity of FSOs systems [12; 13]. Engineers and researchers can use these images and the information they provide to improve FSOs communication, making it faster and more secure for different uses. Storing this image securely is crucial due to potential problems that could compromise data integrity, data accessibility, and data provenance. To address these challenges, blockchain technology is the appropriate option. The solutions are as follows:  
1. Immutable: Blockchain's cryptographic nature ensures that any data within the network is tamper-proof. Every single image on the network is hashed and preserved. 2. Secure Access and Authentication: Blockchain facilitates the implementation of safe access control mechanisms via private and public key cryptography. Stored photos can be accessed or denied access based on predetermined rules enforced through smart contracts. This guarantees that only authorized entities may securely access and distribute the images. 3.