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| 1.1 |
Introduction |
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A light emitting diode (LED) is a device which converts electrical energy to light energy. LEDs are preferred light sources for short distance (local area) optical fiber network because they: |
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are inexpensive, robust and have long life (the long life of an LED is primarily due to its being a cold device, i.e. its operating |
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temperature being much lower than that of, say, an incandescent lamp), |
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can be modulated (i.e. switched on and off) at high speeds (this property of an LED is also due to its being a cold device as it |
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does not have to overcome thermal inertia), |
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couple enough output power over a small area to couple to fibers (though the output spectrum is wider than other sources |
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such as laser diodes). |
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The circuit symbol of an LED is shown alongside. There are two leads, a short one, cathode, labelled  or k and a long one, anode, labelled a or +. |
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