The present disclosure relates to fiber optic networks carrying sensitive information such as classified government communications, sensitive financial information, proprietary corporate information, and associated systems and methods for secure transmission where fiber tampering is easily detected. The present invention provides improved security systems and methods for fiber optic communication links. Specifically, a hollow-core photonic bandgap fiber is deployed as a transmission medium. A secure fiber optic communication link is established over the hollow-core photonic bandgap fiber with a monitoring mechanism. The monitoring mechanism is configured to detect large losses and large spectral variability each indicative of loss introduced by malicious intrusion attempts. Further, the monitoring mechanism allows easy differentiation of intrusion relative to normal system variations thereby reducing false positives and missed intrusions.