Additionally, because VCSELs emit the beam perpendicular to the active region of the laser as opposed to parallel as with an edge emitter, tens of thousands of VCSELs can be processed simultaneously on a three-inch gallium arsenide wafer. This reduces the fabrication cost of the devices. VCSELs are cheap to make and are quite adequate for distances of around 500 meters or less.īecause VCSELs emit from the top surface of the chip, they can be tested on-wafer, before they are cleaved into individual devices unlike edge emitters which can be tested only after production. Transceivers typically use 850nm wavelength VCSELs. VCSELs: The vertical-cavity surface-emitting laser, or VCSEL is a type of semiconductor laser diode which emits laser beams perpendicular from the top surface, contrary to conventional edge-emitting semiconductor lasers (also in-plane lasers) which emit from laser cavities in the middle of a chip. There are 3 main types of lasers in the market today for fiber optic transmitters – VCSELs, FP lasers and DFB lasers. Lasers have proven to be ideal light sources because of their high bandwidth capability and narrow spectral output. Light sources used for fiber optic transmission need to meet several criteria: they must be the right wavelength, be able to be modulated fast enough to transmit data and be efficiently coupled into fiber.
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