The National Communications System (NCS) is responsible for defining reasonable enhancements that could be applied to commercial common carrier (or carriers'-carrier) fiber optic systems that will be leased or owned by Government agencies and that may be used for National Security and Emergency Preparedness (NS/EP) purposes. This paper describes enhancements recommended by the authors for making fiber optic long-haul systems more survivable against both man-made and natural disasters. For a limited nuclear environment, outside of the blast region where buildings and personnel would be expected to survive, involving surface and in-atmosphere nuclear bursts, the vulnerability of optical fiber waveguides to fallout radiation is a primary concern. An assessment of fiber darkening from gamma radiation, based on a review of unclassified literature, is presented. For exoatmospheric nuclear bursts, the fiber optic system is exposed to high altitude electromagnetic pulse (HEMP) radiation. Other man-made disasters include sabotage, fires, accidents, and unintentional dig-ups. Natural disasters considered were floods, earthquakes, lightning, temperature extremes, rodents, etc.