Told by fiber technician Michael Walther | 1 March 2025
We were assigned to install a fiber optic backbone cable between two small towns in central Sweden. A week earlier, we had already received the map data and scouted the area. When working with long distances, proper positioning is crucial – especially considering elevation changes and bends in the duct route.
The client asked if we should split the cable onto two drums since the total distance was 8 km. But I declined – I know what my equipment and I are capable of. And skipping the splice means real cost savings for the client.
We were installing into a 40/32 mm duct, using a 192-fiber cable with a diameter of around 8 mm. Two cabinets along the route were looped together, just in case we needed to adjust the setup mid-installation. For water supply and pressure regulation, we used a flushing truck with 8 cubic meters of water.
We started with low pressure at 4 bar and let the water flow for about 5 minutes before feeding the cable. This helps prevent the cable from outrunning the water, a common issue at lower pressures. Initial speed was around 120–130 meters per minute. After about 1,600 meters, the cable had gone past the water flow. We paused for a minute, then continued – now at 12 bar and 65 meters per minute. As the pressure equalized, we dropped it to 8 bar, which increased the speed to 108 meters per minute.
Around 3,000 meters, we encountered what we call “spaghetti fiber” – the cable compresses and fluctuates in speed. You can hear it in the machine. But the Jetting V2 gives excellent feedback – it’s compact and responsive, yet powerful enough to handle these drums. By lowering the speed and increasing water pressure, we stabilized the flow again.
At 6,000 meters, we held a steady 65 m/min and 15 bar pressure – until the water ran out. We disconnected the hose and sent the driver to refill. Restarting can be tricky when that much cable is already in the duct, but after 15 minutes, we regained the right pressure and continued the job.
Result: 7,700 meters installed in one go – no splice needed. We finished off by looping in the cabinets, slitting the ducts, and labeling the cable. Calling the client to say he could skip the expensive straight splice? Extra satisfying. 🙂
Use air for installations up to 3000–4000 meters. Above that, water is the way to go. Of course, it depends on cable and duct type – but that’s my general rule.
