How Long to Replace a Faulty ONT on FTTP Broadband ISP Lines

The ever-increasing coverage of Fibre-to-the-Premises (FTTP) based broadband ISP networks across the United Kingdom has also started to highlight that, while the infrastructure is fundamentally more reliable, providers will face a rising problem from faulty optical modems or ONT / ONUs (Optical Network Terminal / Units).

In the old days you often only needed to worry about one end-user device going faulty – the broadband router, which in many cases could be replaced by a third-party alternative that the customer kept in reserve, or vice versa for an ISP supplied device – unless the ISP specifically locked down their router(s), which could prevent that. Suffice to say, many of us have spare routers lying around to minimise the risk of downtime.

However, modern FTTP networks have both a router and an ONT. The latter of which is typically installed on the inside wall of your home (wall hung) and works to convert the incoming optical signal into a more conventional electrical one for your router and its Ethernet (Local Area Network) ports to understand.

The issue with this is that it adds another point of potential failure for your connection and, unlike with a router, you can’t just stick a random spare ONT on the wall because they each have a unique identifier for your connection. As it stands, ISPs often need to send out an engineer to replace them (adding to their costs and your potential downtime).

Admittedly, such always-on devices are designed to be both highly reliable and long-lasting (faults are super rare), but inevitably some will still fail and so it’s worth exploring how ISPs respond when this happens.

ONT Faults and Fix Times

Most of the ISPs that we spoke with said that, on the rare occasion where problems arise, it’s usually the Power Supply Unit (PSU – Power Adapter) for the ONT that fails, rather than the optical processor itself. One of the next most common faults, relatively speaking, can occur when a non-standard power outage (mains failure etc.) or surge damages the ONT’s Ethernet port.

The ONT itself typically comes shipped to ISPs with a 12-month guarantee, unless the provider successfully negotiates for more, but sod’s lore dictates that by the time these devices are installed, and possibly fail, then the network provider will probably already be outside that window. But some operators work around that with an “over-supply” agreement (e.g. for every 100 ONTs purchased, the manufacturer will send 101).

Replacing the ONT is a trivial matter as they can come pre-configured with the right serial for your line (i.e. take the old one off the wall and put the new one on), but it does depend upon engineering availability, and that may vary. For some operators, especially smaller networks, it could be as quick as the next working day if reported early enough, but for others it may take a week – or possibly longer in the event of major disruption from storms etc.

In theory, it’s entirely possible that future ONT replacements could become a self-install job, instead of an engineer visit. But as one network operator pointed out: “We’d rather an engineer did it to avoid customers doing silly things, like looking into the lasers” 🙂 (yes, it happens). On the other hand, people still fill up petrol mowers with highly combustible fuel and use dangerous DIY tools, so such a risk is not insurmountable.