Optical Light Sources and Drains

Regarding optical communication engineering and fiber sensor techniques, semiconductor devices are predominantly used as light sources and light drains. Relating to semiconductor light sources and drains, generation and absorption of light can be demonstrated by means of the energy‐band model in semiconductors. Concerning the used light sources for optical communication and sensor techniques, light emitting diodes (LEDs) and semiconductor lasers are primarily applied. The cleaved‐coupled cavity laser consists of two coupled active resonators being adjusted by the injection current. The distributed Bragg reflection laser eliminates the Fabry‐Perot reflection at the ends of the laser by means of two grating reflectors outside the active layer. In general, photodiodes are operated in a reverse biased direction. Photons, which possess a higher energy than the band gap, are able to generate electron‐hole pairs in semiconductor materials. The types of photodiodes are PIN photodiode and avalanche photodiode.