Li-Fi: The Invisible Visible-Light Network

In a fascinating process called electroluminescence, a material produces visible light when exposed to an electric current. This is the science behind light-emitting diodes, better known as LEDs. Early models circa 1965 were used as indicator lights in various appliances. LEDs that are powerful enough to be used for illumination became commercially available in the '90s. These days, LEDs power lights in lampposts, vehicles and electronics, but it's their data-transmitting potential that's causing a stir.

The infrared light spectrum of LEDs is already utilized in signal-transmitting devices such as remote controls. Now, researchers led by Professor Harald Hass propose that LED-based wireless communication technology -- Light Fidelity, or Li-Fi -- can complement or even replace cellular and Wi-Fi transmission of data.

While Wi-Fi relies on the radio-frequency spectrum, Li-Fi can use the entire visible light spectrum, which is 10,000 times larger. This will mean an exponentially higher bandwidth and speed: in lab tests, Li-Fi is 100 times faster than Wi-Fi, and that may only be one hundredth of its potential. Li-Fi doesn't cause electromagnetic pollution, which is good news for our health, as well as for sensitive medical and navigation instruments. Ordinary lamps could become ubiquitous data access points that require no additional energy or expense.

Currently, Li-Fi is limited to indoors and a short range. However, its developers see a very bright future ahead.

Li-Fi：光速上網

在一個名為「電場發光」的迷人過程中，物體暴露於電流下，產生了可見光。這就是發光二極體──也就是我們熟知的 LED──背後的科學原理。1965 年左右的早期 LED 燈模組被用作各種裝置的指示燈。功能強到足以做為照明器具使用的 LED 在 90 年代成為可供市售的商品。如今，LED 的功率點亮了燈柱、車輛與電子儀器，但造成轟動的是它的數據傳輸潛力。
LED 的紅外線光譜早已用在遙控器之類的訊號傳輸裝置上。今日，由哈洛德．哈斯教授領軍的研究者們提出，以 LED 為基礎的無線通訊技術──稱為 Light Fidelity 或 Li-Fi──可補足或甚至取代手機和 Wi-Fi 的資料傳輸功能。
Wi-Fi 仰賴無線電頻譜，而 Li-Fi 則是用大出一萬倍的可見光光譜來傳輸。這將代表頻寬和傳輸速度都是以指數成倍數成長：在實驗室裡的測試中，Li-Fi 比 Wi-Fi 的速度快了一百倍，而這可能只是它百分之一的潛力。Li-Fi 不會製造電磁波汙染，對我們的健康是個好消息，也不會干擾敏感的醫療與導航儀器。一般的燈具就能變成普遍的資料傳輸點，不需額外的能源或花費。
目前，Li-Fi 僅限於室內或短距離使用。然而，其研究者看到的是一片光明的未來前景。