A leased line is a dedicated, fixed-bandwidth data connection. It allows data-hungry businesses to have a reliable, high-quality internet connection with guarantees of upload and download speed, uptime and resilience. “Leased” refers to the connection which is rented by the Internet Service Provider (ISP) directly to a business, resulting in a service above and beyond what standard broadband provides. A leased line uses exactly the same technology as fibre optic broadband. A fibre optic leased line works by sending pulses of light down a fibre optic cable. When you need to send data down a fibre optic cable, the equipment at either end is on the lookout for light – namely whether the light is on or off – representing the binary 0s and 1s of digital data. Equipment at one end will turn lights on and off to represent 1s and 0s, and the equipment at the other recognises this, records it and stores it back as 1s and 0s.
This data travels at the speed of light. As it is physically impossible for this to be any faster, the only limiting factor on speed is more often how quickly the equipment at either end can send or recognise light.
Where a leased line differs is this connection is leased to a business, so this connection to the ISP is unique to that particular firm, rather than shared with many thousands of others.