transmission line; transmission path
Technical term used in telecommunications and signal engineering for the physical or logical medium that carries signals.
Optical fiber is widely used as a high-speed data transmission line.
Measure the characteristics of the transmission path.
回線 is a general term for a circuit or line, commonly used in telephony and networking, whereas 伝送路 is more specific to the transmission aspect.
Compound of 伝送 (transmission) + 路 (path, route). A straightforward technical coinage.