OMU and ORU: radio frequency over fibre optic distributed antenna system
When one repeater has to cover several blocks or many floors, I use a fibre system: an OMU next to the repeater, and an ORU in each area that needs signal. These are the units I work with.
How the system fits together
- RepeaterThe repeater, such as the SLR 5300, stays in the equipment room and handles the talk.
- OMUSits beside the repeater, turns its radio signal into light and sends it over optical fibre.
- FibreOptical fibre out to each zone, up to 20-30 km from the OMU.
- ORU and antennasTurns the light back into radio signal and feeds the antennas in its zone. Talk from portable radios goes back the same way.
OMU and ORU side by side
| OMU | ORU | |
|---|---|---|
| Where it sits | Next to the repeater | In each zone that needs signal |
| What it does | Radio to light | Light to radio, then amplifies |
| Fibre ports | 4 LC | 1 LC |
| Operating temperature | -5 to +45 °C | -25 to +55 °C |
| Size | 2U, cabinet installation | 2U, cabinet installation |
| SIRIM | Type approved | Type approved |
When it fits
- Sites with more than one building that must share the same channels.
- Tall buildings, deep basements and sealed rooms that one antenna point cannot reach.
- Long runs between buildings, where coaxial cable would lose too much signal.
One building with a basement is often fine with a repeater and a good antenna layout. I check on site first.
Certification and licence
Both units hold SIRIM QAS type approval in the repeater category, for 400 to 450 MHz, valid to September 2031. Tell me if your tender needs copies of the certificates. A repeater system with a fibre optic distributed antenna system still needs an MCMC licence, and I can handle the application.
The units
Radio Frequency Over Fibre Optic Distributed Antenna SystemOMUData centres, campuses and tall buildings where one repeater has to cover several blocks or many floors.Specs and quoteRadio Frequency Over Fibre Optic Distributed Antenna SystemORUBlocks, floors and basements too far from the repeater for its signal to reach well.Specs and quoteCommon questions
How far can an ORU be from the OMU?
Up to 20-30 km of fibre. On a real site the distance is set by your buildings and where fibre can run.
Do the OMU and ORU replace the repeater?
No. The repeater still handles the talk. The OMU and ORU carry its signal to the places it cannot reach on its own.
Which frequency do they work on?
UHF, VHF, HF or customised, set to your licensed frequency. The SIRIM approval covers 400 to 450 MHz. Tell me your frequency and I will check it before I quote.
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