Connection between base stations and optical cables

Optical cables are distributed to base stations using a combination of hybrid optical-electrical cables, point-to-point or point-to-multipoint topologies, and optical modules connecting BBUs and RRUs.Cable Types and StructureOptical cables used for base station distribution can be single-mode or multi-mode fibers housed in loose tubes or tight-buffered subunits. Loose tube cables contain fibers in high-modulus plastic tubes filled with a gel-like compound for protection, with a central metallic or non-metallic strength member for mechanical support, and are armored with steel tapes or aramid yarns for durability . Tight-buffered fibers are often surrounded by a helical steel hose and LSZH (low-smoke zero-halogen) outer sheath for additional protection . Hybrid cables combine optical fibers and copper conductors to simultaneously transmit data and DC power to remote units .Network TopologiesOptical distribution can follow point-to-point or point-to-multipoint configurations:Point-to-point: A single central office terminal (COT) connects directly to one or multiple remote terminals (RTs) or RRUs using hybrid optical-electrical cables, joint boxes, and patch cords .Point-to-multipoint: Used when multiple base stations are scattered over a wide area. A joint box splits the hybrid cable to feed several RRUs or micro base stations, allowing efficient deployment and centralized maintenance .BBU-RRU ConnectionsIn distributed base stations, the Baseband Unit (BBU) processes signals, while the Remote Radio Unit (RRU) transmits them. Optical fibers connect BBUs and RRUs using optical modules. Depending on network requirements, modules can support 1.25G, 2.5G, 6G, or 10G transmission rates . To optimize fiber usage over long distances, Coarse Wavelength Division Multiplexing (CWDM) allows multiple signals to share a single fiber, enabling serial networking of BBUs and RRUs and reducing the number of fibers required .Hybrid Optical-Electrical SolutionsHybrid cables allow simultaneous transmission of optical signals and DC power, reducing the need for separate power lines and simplifying maintenance. The DC remote power supply system converts high-voltage DC or AC to 48V DC to power RRUs, optical repeaters, and small base stations, ensuring all-weather, maintenance-free operation .SummaryOptical cable distribution to base stations involves:Using single-mode or multi-mode fibers in loose tube or tight-buffered hybrid cables.Employing point-to-point or point-to-multipoint topologies depending on base station layout.Connecting BBUs and RRUs with optical modules and optionally using CWDM to maximize fiber efficiency.Integrating hybrid optical-electrical cables to deliver both data and power efficiently, reducing construction and maintenance costs . This approach ensures high-bandwidth, long-distance, and reliable communication between distributed base stations.