While fiber optics are tough, cold temps can cause trouble. Water in cables can freeze, potentially harming connections. Waterproofing prevents icy issues. Waterproof fiber connectors are designed to protect the optical interface from water and particulate ingress, not to improve optical performance. Their defining feature is the mechanical sealing system surrounding the connector interface, which isolates the ferrule, adapter sleeve, and mating zone. You need to keep water out and buffer temperature swings. When the temperature drops, the water freezes, and ice forms around the fiber – with the large resulting forces causing the fiber to deform and bend.