They have been connected via a spur line from a subsea cable which stretches 68 miles from the Shetland to Orkney Islands.
It is the greatest distance that Openreach has transmitted a continuous full fibre signal anywhere in the UK.
Openreach had to deploy innovative engineering to boost the signal strength because of the distance between the islands.
Among the businesses connected are a post office and shop, while all premises on the island can now order the service too.
The project has been funded through the Scottish Government’s £404.1 million Reaching 100% (R100) North contract and £17.4 million from the UK Government.
Wellbeing economy secretary Neil Gray, said, “I am delighted that we have achieved digital connectivity for Fair Isle almost two years earlier than planned. Through our R100 commitment to tackle some of the hardest to access terrain in the country, we are improving the educational and life opportunities available to young people across Scotland. This innovative step forward for engineering ensures children on Fair Isle are not left behind.
“Internet speeds rivalling the best in the country are helping create a more attractive place for families and young people to live.
“We committed to invest further in our digital connectivity, despite powers being reserved to Westminster, because we know that by supporting remote working and rural businesses – from Fair Isle jumpers to tourism – we can help to build an island economy which is fair, green and prosperous.”
Stackhoull Stores and Post Office was connected to full fibre before Christmas.
Postmistress Fiona Mitchell, said, “We are a small population and want to grow and encourage people to be a part of our community. Getting a full fibre connection so that people can more easily work and live here is a major part of that. We need all hands on deck to make the island run.”
Openreach chief engineer for Scotland, Fraser Rowberry, said: “Regular fibre signals just couldn’t go the distance, so we had to get creative with some world first engineering to transmit life-changing ultrafast broadband over 100 kilometres to islanders. We had to do everything differently on Fair Isle, from planning around bird nesting seasons to setting up flat-packed cabins for our crew.
“A big shout-out to the people of Fair Isle for being so welcoming to our team. They’ve been amazing. Now, they’re connected to the world in a whole new way. This will make Fair Isle an even better place to be – for residents, visitors and future generations – and we’d encourage people on the island to upgrade to full fibre.”