Strictly speaking, a DS1 is the data carried on a T1 circuit, and likewise for a DS3 and a T3, but in practice the terms are used interchangeably.
At least one manufacturer has a commercial system[citation needed] that operates at 90 Mbit/s, twice the DS3 rate.
New systems, which take advantage of the high data rates offered by optical communications links, are also deployed or are under development.
DS3 may be converted to an optical fiber run when needing longer distances between termination points.
When a DS3 is delivered over fiber it is still an analog type trunk connection at the termination points.