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通常的光纤主要是由两种透明材料制成的:中心是高折射率的玻璃纤芯,外面是低折射率的硅玻璃包层。光线在纤芯中传送,当射到纤芯和包层的界面时,就反射回来,然后在纤芯内继续向前传送。光缆虽然适合远距离传输信号,但是在某些特殊的场合,比如外层大气或者核反应堆内,我们却无法铺设。若让信号直接在空气中传播呢,则又发散得太快,这跟我们在100米内还可看见一盏灯,1000米外就见不到了,是一个道理。现在,美国科学家想出一个办法,让空气来模拟光纤。他们先在空气中发射4束激光。这4束激光很细,
The usual optical fiber is mainly made of two kinds of transparent materials: the center is a high refractive index glass core, outside is a low refractive index silicon glass cladding. The light is transmitted in the core and, when it hits the interface between the core and the cladding, it reflects back and then travels forward within the core. Although suitable for long distance signal transmission cable, but in some special occasions, such as the outer atmosphere or nuclear reactor, we can not be laid. If the signal is transmitted directly in the air, it will diverge too fast, which can be seen with us in a 100-meter lamp, it can not see 1000 meters, is a reason. Now, scientists in the United States come up with a way for the air to simulate fiber. They first fired four lasers in the air. This 4 laser is very thin,