Setting up a Redundant Link
For critical satellite communications – such as military comms, TV broadcast, Internet services – and satellite TT&C (Telemetry, Tracking and Command) it is vital to have redundant systems in place to ensure five nines reliability (99.999% uptime). Many of the world’s leading satellite operators and service providers rely on 1:1 redundant systems to reduce downtime.
Major causes of primary link failure
- The cable being damaged or disconnected
- Removal of the transmitter or receiver
- Equipment failure
- Any system alarm
Mitigating risk of downtime
The risk of failure of an RFoF link is low. Typically RF over fiber links have a MTBF (Mean Time Between Failure) of at least 15 years. The most common cause of failure is the cable being damaged. This can be mitigated by running the primary and second links through two separate fiber cables.
Rapid module replacement
It is possible to further minimize downtime through the use of ViaLite’s blind mate feature which allows for the rapid replacement of rack chassis modules – reducing downtime time from several minutes to seconds. The ViaLite SNMP module has an auto-configuration function which automatically loads the settings of the old module to the replacement module, resulting in zero setup time.
How a redundant system works
A 1:1 redundant system uses an RF splitter to allow the signal to be transported across two separate fibers. The splitter can be placed anywhere within the system – freeing-up rack space and allowing for the use of an existing splitter to lower costs.
In the event of a major alarm, in the receive module of the chosen primary link, the RF switch automatically reverts to the secondary fiber link. As the signal is being transmitted on two fibers simultaneously, it is switched instantly, providing instaneous redundancy.
Setting up a redundant system
Either single or dual ViaLite RF over fiber modules can be used in a redundant system. In a single RF module system, the switch is placed in-between the primary and secondary RF over fiber links, providing four fully redundant RF channels in a 3U chassis.
To increase the number of RF channels per 3U chassis, it is possible to use the ViaLite dual RF over fiber modules in a redundancy configuration which allows up to six fully redundant RF channels per unit.
A dual system has dual modules situated either side of the switches, with the exception of the modules in the end slots: 1 and 13, which are single modules. This allows cross-coupling of the dual modules with channel B (the primary feed) on the first dual module backed-up by channel A (secondary feed) on the second dual module. Single modules are used at either end as there is only one channel to back-up.