A tether is a length of cable which connects the Companion Computer to the Topside Computer. Radio frequency (RF) waves do not travel far through water and acoustic modems have limited bandwidth, so a tether is a critical component to connect the vehicle to a surface computer.
The Companion Computer communicates by 10/100 Base Ethernet. Therefore, a standard Cat 5 cable may be used to connect to the vehicle and topside computer. The maximum transmission length of Cat5 cable is around 100m.
Although optional and not necessary for basic functionality, tether interfaces increase the range and reliability of Ethernet communications.
Interfaces for Copper Twisted Wire Pairs
Interface boards which use the Homeplug AV standard provide a robust high-speed, long-distance Ethernet connection over a single pair of wires. These boards enable HD video and high-bandwidth data over 300m+ tether lengths.
The following interface boards are supported:
- Blue Robotics Fathom-X Tether Interface Board Set
- Blue Link Dual Ethernet Plus Serial Multiplexer (DEPS MUX)
Interfaces for Fiber Optic Cable
With communications being Ethernet based, fiber optic cables may also be used with Ethernet-to-Fiber converters installed inside the ROV and topside.
The following fiber optic interface boards have been known to work: