A CATV ONU allows telecom operators to deliver internet and cable TV services over a single fiber. It combines normal PON access with a 1550 nm RF overlay, giving users broadband, Wi-Fi, voice, and television through one compact device.
This article explains how the CATV function works, its main benefits, and what to check when choosing an ONU for an FTTH network.
What Is a CATV ONU?
An ONU, or Optical Network Unit, is installed at the user end of a Passive Optical Network. It receives optical signals from the service provider and converts them into services that customers can use.
A standard ONU usually provides Ethernet and Wi-Fi. Some models also include voice ports. A CATV ONU adds an RF port for cable television.
The CATV port converts an optical TV signal into a standard RF signal. Users can connect the port to a TV or set-top box through existing 75 Ω coaxial cable. This makes it easy for operators to add television services without replacing the customer’s indoor coax network.
How Does the ONU CATV Function Work?
In a typical GPON or EPON network, different wavelengths carry different services:
- 1310 nm: upstream data from the ONU
- 1490 nm: downstream internet data
- 1550 nm: downstream CATV signal
At the headend, a CATV optical transmitter converts the television signal into a 1550 nm optical signal. A WDM device combines it with the PON data signal. Both services then travel through the same fiber and passive optical splitter.
Inside the ONU, another WDM component separates the wavelengths. The PON section processes internet data, while the CATV receiver converts the 1550 nm optical signal back into RF. The RF signal is then delivered through the CATV port.
Because television and data use separate wavelengths, the CATV service does not consume normal PON data bandwidth. It can also continue working independently of the internet connection.
Main Benefits of a CATV ONU
One Fiber for Multiple Services
A CATV ONU supports internet, Wi-Fi, voice, and cable TV over one fiber connection. This simplifies FTTH deployment and reduces the need for separate access networks.
Easy Use of Existing Coaxial Cables
Many homes, hotels, and residential buildings already have coax wiring. The ONU’s RF output can connect directly to this network, reducing installation time and cost.
Stable RF Output with AGC
Many CATV ONUs include Automatic Gain Control (AGC). AGC keeps the RF output level stable when the incoming optical power changes within the supported range. This helps maintain consistent picture quality across different subscriber locations.
Independent TV and Internet Services
The 1550 nm RF overlay is separate from the PON data channel. Heavy internet use therefore does not reduce television bandwidth or affect the number of broadcast channels.
Simple Network Expansion
Operators can add CATV service to an existing PON network by deploying a CATV transmitter, optical amplifier, and WDM equipment at the headend, together with compatible CATV ONUs at subscriber sites.
Where Is a CATV ONU Used?
CATV ONUs are suitable for:
- FTTH networks that provide broadband and broadcast TV
- Hotels and apartment buildings with existing coax distribution
- Rural broadband projects that still require traditional television
- Network upgrades from HFC or cable TV systems to fiber
- Triple-play services combining data, voice, and video
They are especially useful when an operator wants the efficiency of fiber while keeping familiar RF television equipment at the customer end.
Important Specifications to Check
When selecting an ONU with CATV support, review these parameters:
