| 单词 | optical fibre |
| 释义 | optical fibre A wave guide through which light can be transmitted with very little leakage through the sidewalls. In the step-index fibre a pure glass core, with a diameter between 6 and 250 micrometers, is surrounded by a coaxial glass or plastic cladding of lower refractive index. The cladding is usually between 10 and 150 micrometers thick. The interface between core and cladding acts as a cylindrical mirror at which total internal reflection of the transmitted light takes place. This structure enables a beam of light to travel through many kilometers of fibre. In the graded-index fibre , each layer of glass, from the fibre axis to its outer wall, has a slightly lower refractive index than the layer inside it. This arrangement also prevents light from escaping through the fibre walls by a combination of refraction and total internal reflection, and can be made to give the same transit time for rays at different angles. Fibre-optic systems use optical fibres to transmit information, in the form of coded pulses or fragmented images (using bundles of fibres), from a source to a receiver. They are also used in medical instruments (fibrescopes ) to examine internal body cavities, such as the stomach and bladder |
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