Liminal-F is an advanced, cost-effective, fiber-optic technology-based intrusion detection system that provides superior perimeter security. This robust and highly reliable system can detect various types of intrusion attempts, including climbing, cutting, and breaking on fences, and it generates immediate alarms using Active Detection technology. Liminal-F operates on the principle of light signal interference within optical fibers. As an intrusion detection sensor system, it leverages the properties of light traveling through these fibers to sense disturbances caused by potential intrusions. This innovative approach ensures highly sensitive and accurate detection, enhancing the overall security of the perimeter. It is engineered to be functionally robust even under harsh environmental conditions. It maintains its effectiveness when exposed to direct sunlight, high temperatures, rain, moisture, and dust. This durability ensures that the system provides consistent security monitoring regardless of the external environment, making it suitable for a wide range of applications. The versatility of Liminal-F allows it to be installed in various configurations to suit different security needs. The fiber-optic cable can be laid over walls, fences, or even buried underground, providing a flexible solution for diverse perimeter security challenges. This adaptability makes it an excellent choice for both urban and rural settings, as well as for protecting critical infrastructure. The principal application of the Liminal-F system is in the surveillance of areas requiring critical security monitoring. This includes military bases, government facilities, airports, power plants, and other high-security zones. By providing reliable and accurate intrusion detection, Liminal-F ensures that these critical areas are safeguarded against unauthorized access and potential threats.