Abstract: To address the challenges in monitoring-data transmission for mountain transmission lines in areas without public-network coverage, this paper proposes a wide-narrowband data backhaul scheme integrating optical fiber and Long Term Evolution Mesh (referred to as LTE ad-hoc network). With the collaborative design of Optical Ground Wire (OPGW) and LTE Mesh wireless communication modules, combined with the interface conversion function of intelligent enhanced splice closures, a full-coverage communication network for power transmission corridors is established. Pilot application on the 35 kV Taizhang Line in Jiangshan, Zhejiang Province demonstrates that the device enables reliable transmission of data including ice-coating monitoring, conductor sag detection, and channel visualization. It supports a maximum transmission rate of 100 Mbps, and the rate remains no less than 6 Mbps after 7 hops. The scheme effectively resolves the bottleneck of data transmission for transmission lines in deep-mountain areas and provides technical support for the safe operation and maintenance of transmission lines under extreme conditions.