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Science and Technolgy.
科技。
Visible-light communication.
可見光通信。
Tripping the light fantastic.
與光共舞。
A fast and cheap optical version of Wi-Fi is coming.
一個高速而廉價的光學Wi-Fi即將問世。
AMONG the many new gadgets unveiled at the recent Consumer Electronics Show in Las Vegas was a pair of smartphones able to exchange data using light.
最近，在拉斯維加斯國際消費電子展上首次展出的電子產品中，有一對能利用光交換數據的智能手機。
These phones, as yet only prototypes from Casio, a Japanese firm, transmit digital signals by varying the intensity of the light given off from their screens.
目前，這兩部不過是日本卡西歐公司的樣機，它們能通過改變自身屏幕的光強來傳傳輸數字信號。
The flickering is so slight that it is imperceptible to the human eye, but the camera on another phone can detect it at a distance of up to ten metres.
這樣的閃光很微弱，人眼無法感知，但另一部手機的攝像頭能夠在十米的范圍內檢測得到。
In an age of Wi-Fi and Bluetooth, flashing lights might seem like going back to sending messages with an Aldis lamp.
在這個Wi-Fi和藍牙橫行的時代里，使用閃光可能有點像回到用奧爾迪斯手提信號燈發送信息的年代。
In fact, they are the beginning of a fast and cheap wireless-communication system that some have labelled Li-Fi.
事實上，它們正是有人稱之為Li-Fi的高速、廉價的無線通訊系統的鼻祖。
The data being exchanged by Casio's phones were trifles: message balloons to be added to pictures on social-networking sites.
兩部卡西歐手機交換的數據量非常小：不過是添加在社交網站圖片中的虛擬對話框。
But the firm sees bigger applications, such as pointing a smartphone at an illuminated shop sign to read information being transmitted by the light: opening times, for example, or the latest bargains.
但卡西歐公司發現這項技術有更大的應用前景，比如將智能手機對準發光的商店招牌讀取通過燈光傳送的信息：如營業時間或最新優惠。
Yet that is still only a flicker of what is possible.
但是，這項技術可能有萬千功能，以上不過是冰山一角。
Last October a number of companies and industry groups formed the Li-Fi Consortium, to promote high-speed optical wireless systems.
去年十月，多家公司及實業集團共同成立了Li-Fi聯盟，以推廣高速無線光學通信系統。
The idea is that light can help with a looming capacity problem.
他們的想法是可見光通信將有助于解決即將來臨的數據傳輸瓶頸問題。
As radio-based wireless becomes ubiquitous, more and more devices transmitting more and more data are able to connect to the internet, either through the mobile-phone network or through Wi-Fi.
隨著無線電通訊的普及，越來越多的數據傳輸量越來越大的設備能夠通過移動網絡或Wi-Fi與互聯網連接。
But there is only a limited amount of radio spectrum available.
但可用于通信的無線電頻段是有限的。
Using light offers the possibility of breaking out of this conundrum by exploiting a completely different part of the electromagnetic spectrum, one that is already ubiquitous because it is used for another purpose: illumination.
運用一個完全不同的電磁波段——可見光，就有可能解決這個難題；這個波段其實早已相當常用，因為它有另一個作用：照明。
Lighten the darkness.
照亮黑暗。
To turn a light into a Li-Fi router involves modulating its output, to carry a message, and linking it with a network cable to a modem that is connected to a telephone or cable-broadband service, just like a Wi-Fi router.
要將一個可見光源變成能夠攜帶信息的Li-Fi路由器，需要調制其光強以及用網線將其與一個調制解調器（與電話或寬帶網線相連）連接，一如Wi-Fi路由器。
Incandescent light bulbs and fluorescent tubes are not really suitable for modulation, but they are yesterday's lighting technology.
白熾燈和日光燈的光其實并不適合調制，不過它們已是舊式的照明技術了。
Tomorrow's is the light-emitting diode. LEDs are rapidly replacing bulbs and tubes because they are more efficient.
新式的照明技術是發光二極管（LED），LED正憑借其更高的能量利用率迅速取代電燈泡和燈管。
And because they are semiconductor devices, tinkering with their electronics to produce the flickering signals required for data transmission is pretty straightforward, according to Gordon Povey, who is working on light communication with Harald Haas and his colleagues at the University of Edinburgh, in Britain.
歌登?波文在英國愛丁堡大學與哈拉爾德·哈斯及其同事一起研究光通信；他說，因為LED是半導體器件，調整一下其電路就能很輕易地產生傳輸數據所需的閃光信號。
The rate of data transfer is also good.
用可見光傳輸數據的速度也相當可觀。
Dr Povey's group is already up to 130 megabits a second (faster than some older Wi-Fi routers) over a distance of about two metres, using standard LEDs.
波文博士的研究小組已能利用標準LED在約兩米內以最高每秒130兆位的速度（比一些老式Wi-Fi路由器還快）傳輸數據。
Dr Povey, who is also the boss of VLC, a firm set up to commercialise the technology, thinks such devices should be able to reach 1 gigabit per second (Gbps), and do so over greater range.
同時也是VLC公司（為使這種技術商業化而成立的公司）的老板的波文博士認為這種器件應能達到每秒1千兆比特（Gbps）的傳輸速度，且傳輸距離可以更遠。
Specially constructed LEDs would be even faster. The Li-Fi consortium reckons more than 10 Gbps is possible.
采用特制LED所達到的速度將會更高。Li-Fi聯盟估計傳輸速度可能達到10 Gbps以上。
In theory, that would allow a high-definition film to be downloaded in 30 seconds.
理論上，這個速度意味著不到30秒就能下載一部高清電影。
Dr Povey believes that adapting existing LEDs to work with the sensors and light sources-cameras, ambient-light detectors, screens, flashbulbs, torches and so on-already found in smartphones and similar devices will be the fastest way to bring Li-Fi to market.
波文博士認為，改造現在的LED使之適應智能手機及類似設備上已有的感應器及光源，如攝像頭、環境光感應器、屏幕、閃光燈泡、手電筒等，是將Li-Fi推向市場最快的方法。
VLC has already produced a smartphone app which allows low-speed data transmission between a pair of iPhones.
VLC已設計了一款智能手機軟件，兩部iPhone能用此軟件以低速傳輸數據。
It has also made an experimental optical transceiver that plugs into a laptop to receive and send light signals.
該公司也制造了一臺用作試驗的光收發器，可插入筆記本電腦以收發光信號。
Later this year it will bring out Li-Fi products for firms installing LED-lighting systems.
今年再過不久，VLC將面向安裝了LED照明系統的企業推出Li-Fi產品。
There are limitations to using light, of course. Unlike radio, light waves will not penetrate walls.
當然，利用可見光通信也存在局限性?？梢姽獠煌跓o線電波，無法穿透墻壁。
Yet for secure applications that could be a bonus.
但對于安全應用而言這可能是個意外的優點。
And light bulbs—some 14 billion of them around the world-are almost everywhere and often on.
而全球大約共有一百四十億個燈泡，它們幾乎隨處可見，而且經常亮著。
As they are gradually replaced by LEDs, every home, office, public building and even streetlight could become a Li-Fi hotspot.
隨著電燈泡逐漸被LED所取代，每家每戶、辦公室、公共建筑物、甚至路燈都可能成為一個Li-Fi熱點。
Having a line-of-sight connection with the LED in question would undoubtedly improve the signal, but light reflected from walls or ceilings might often be enough.
若你正在使用的LED光源處于視線范圍內，信號強度無疑會有所增加，不過僅靠墻壁或天花板的反射光可能往往也足夠了。
In any case, having a good line of sight helps Wi-Fi as well. And spotting a nearby light in order to sit next to it is certainly easier than finding the location of a Wi-Fi router.
同樣，不論如何，若在視線之內有Wi-Fi信號源，信號當然也會更強。而在身邊找一個光源就近使用之當然要比尋找Wi-Fi路由器來得容易。
Communication, though, is a two-way street. That means the LEDs involved in Li-Fi would need photodetectors to receive data.
不過通信是雙向的。這意味著Li-Fi中的LED需要有光電探測器來接收數據。
Some LED systems have such sensors already (to know when to turn on at night).
一些LED系統已經配備這種探測器了（以便在夜間判斷何時開燈）。
But even if LEDs are not modified Dr Povey reckons hybrid systems are possible: data could be downloaded using light but uploaded (typically a less data-intensive process) using radio.
但即使不對LED進行改造，波文博士認為混合系統也可能行得通：通過光下載數據，而上傳數據則使用無線電波（這一過程的數據量通常小些）。
In an office, for example, an LED-powered desk lamp could work as a Li-Fi router, able to link up with any networked device placed on the desk.
例如在一個辦公室里，一盞LED臺燈也可以是一個Li-Fi路由器，它能連接桌上任何一個已經聯網的設備。
A big advantage of light is that it can be used in areas which contain sensitive equipment that radio signals might interfere with, such as aircraft and operating theatres.
可見光通信的一大好處在于：它在裝有可能會受無線電信號干擾的敏感設備的場所能派上用場，如飛機上及手術室內。
LEDs in the ceiling of an airliner would not only allow internet access but could also transmit films on demand to individual seats, removing the need for lots of expensive and heavy cabling, thus saving airlines fuel.
將LED安裝在大型客機的艙頂，不僅能提供網絡服務，還能將旅客點播的電影傳送至他們的座位上，這樣就不必安裝許多昂貴而又笨重的線纜，如此一來也會節省燃油。
That alone could be enough to, as it were, make this idea fly.
光是這一點，似乎就足以令這項技術騰飛。
