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What is IRS network? | Basics of fiber optic distribution
IRS stands for Integrated Reception System. When discussing in-building optical networks (FTTH / MDU – Multi-Dwelling Unit), the industry refers to this as Fibre IRS (FIRS).
The concept is dead simple yet brilliant: the entire RF frequency spectrum coming from a single shared antenna headend (satellite dish + terrestrial DVB-T/T2 + FM/DAB radio) is converted into light, and then distributed to the apartments purely over optical fiber.
Instead of residents installing individual dishes on the facade, or having to drag thick, heavy coaxial cable bundles (trunks) down the risers to the apartments, the whole setup fits onto a few thin optical fibers.
How is a Fibre IRS Network Structured?
The system basically consists of three main parts:
1. Optical Transmitter Side (Headend)
The signals from roof-mounted antennas (such as one or more satellites like Astra or Hotbird, plus local terrestrial digital broadcasts) are fed into an optical transmitter (Optical Headend). This dedicated device (such as solutions from Triax or Televes) modulates the entire high-frequency RF spectrum onto one or more optical wavelengths (typically in the 1310 nm or 1550 nm range).
2. Optical Distribution Network (ODN, PON)
- The optical signal is distributed down the risers using passive optical splitters.
- There is no need for stairway amplifiers or active multiswitches on each floor, which would consume power and could fail.
- Signal loss (attenuation) is negligible compared to coax, allowing distances of up to several kilometers to be bridged without any quality degradation.
3. Receiver Side (GTU – Gateway Termination Unit)
The optical fiber terminates inside the apartment (usually in the low-voltage distribution box). This is where a GTU (or optical receiver) is placed, acting as a passive/active converter. This box converts the light back into standard RF electrical signals, providing the user with the exact same connectors at the output as if they had their own antennas:
- SAT outputs (up to 4 coax cables corresponding to the polarizations of a Quattro LNB, or a dSCR/Unicable output for modern receivers like Sky Q)
- Terr/Radio output (for terrestrial TV and radio broadcasts)
Why is this better than traditional coaxial IRS?
- Cable size and space requirements: In a traditional 4-satellite coax system, you would have to pull up to 17 thick coax cables down the riser. With fiber, a single, hair-thin optical fiber carries the exact same payload.
- No voltage differences or interference: Fiber optics provide complete galvanic isolation between the apartments and the roof antennas. No more ground loops, equipment damage from secondary lightning strikes, or electromagnetic interference (EMI).
- Compatible with internet (GPON): It is very common to multiplex the Fibre IRS signal (e.g., at 1550 nm) onto the same physical fiber used for the apartment's GPON internet (1310/1490 nm). This delivers gigabit internet and the full satellite/terrestrial TV lineup over a single fiber entering the apartment.
This technology is the low-voltage backbone of newly built premium apartment buildings, hotels, and residential parks.
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