How Shifting Dynamics in Intercontinental Cabling are Driving New High-Reliability Solutions From G&H

When a manufacturing facility producing high-reliability components for long-distance submarine cables suddenly has to triple its output of couplers for prestige clients, meeting this demand is literally a tall order. But this is exactly what happened at our Torquay facility.

Torquay has been making high-reliability (HI REL) fused couplers for the past 21 years, which we design and specify for never-fail deployment on the ocean floor. Recently the world’s appetite for these critical enabling technologies has multiplied, with bandwidth requirement literally exploding, driven by the growth in fiber-to-home installation, the increasing use of social media applications, and also, of course, by the huge rise in video calls and remote working caused by the Covid pandemic. Some cables now in use are capable of a total two-way carrying capacity of 60 terabits per second.

Image: G&H Fusion

Against this backdrop, it is clear that HI REL components will become even more critical in ensuring a global data flow that is ‘always on’, and foremost amongst these are fused fiber couplers, which enable the signal to be amplified and re-emitted by repeaters on the ocean floor every 100 km or so.

If you use the internet – or any other medium that relies on submarine cables – there is a greater than 50% chance that your data passes through G&H couplers, since in each repeater there are up to eight coupled amplifiers, and several hundred repeaters are installed on a typical transatlantic undersea link.

To ensure the best possible high-reliability fiber coupler production, the manufacture of these pieces involves significant human input and observation. We believe that working “hands on” gives us the advantage in terms of quality, whether it is manual fiber stripping and handling; inserting the fibers into the manufacturing rigs; or observing processes and measurements.

Repeater pods provide a dry, constant-temperature environment for our couplers. The device is housed in a 3 mm diameter stainless 55 mm-long steel tube. These small and incredibly simple but reliable components are responsible for carrying all of our internet traffic from continent to continent. Yet the incessant appetite for bandwidth will soon see cables that are made up of many more pairs of fibers than previously – in the immediate future 12 – 16, as opposed to the current 6 – 8, and in the next 3 – 5 years we can expect 32 – 48 fiber pairs in one cable.

Clearly, this increase in cabling fibers raises challenges around the physical size of the repeater housings, as it is not technically desirable or cost-effective to increase their footprint – yet more fibers will mean more couplings must, necessarily, be accommodated within those same dimensions.

G&H’s response has been to develop a 4 x 4 fiber optic coupler that enables pump sharing through a single component, rather than the traditional approach of networking four 2 x 2 components together. This saves space, thereby reducing the footprint and simplifying customer designs.

Figure: 4 x 4 fiber optic coupler pump sharing

But it also delivers other benefits to our customers, too. The 4 x 4 design means fewer connections, so minimal optical loss, and makes for easier, quicker, and more cost-efficient manufacture and deployment.


We use proof-testing at two stages in our manufacturing process. We clean the fiber and get it into a fit state for our fusion rigs, in order to prevent damaging the fiber’s surface. Then we strain test it to verify its strength before loading onto the fusion rig. It is also proof-tested at the end of the fusion process. We optically-test the devices before the temperature screening process, and we then check to see there is no change in optical performance through screening. By this means, we are ensuring that the devices are strong and there are no mechanical flaws in the fused fiber.

At present, our 4 x 4 HI REL fiber optic couplers have passed critical design review, and are about to go into production readiness review and then qualification period. They are already in test with some customers, and samples will be available to our wider customer base shortly.


As a consequence of the recent surge in demand, we have grown our production teams, built a new clean room, and we now offer a comprehensive line of fused fiber couplers for visible and NIR wavelengths using single-mode and polarization maintaining fiber. We also offer multimode pump combiners.

However, submarine cables aren’t the only application where HI REL components are critical. Space applications, for example, require a similar level of component dependability, for similarly limited size and weight in ratio to power (SWaP), and this application sector is also growing exponentially.

In fact, G&H components have been used in a number of national space agency missions, including Hayabusa 2, ExoMars TGO, and ExoMars Rover, so our ability to produce solutions that stand up to the rigors of harsh environments (temperature extremes, vibration, shock, radiation) where failure is not an option is well proven.

In short, with its 4 x 4 fused fiber optic couplers and its extensive expertise and experience in the wider fiber optic applications field, G&H has stayed ahead of the curve for its customers, delivering once again on its mission to change the world – and cyberspace – with photonics.

For more information on our HI REL products, take a look at our fused fiber components page.