Arrayed waveguide grating
2271614
197141780
2008-03-10T02:16:27Z
207.172.132.245
'''Arrayed waveguide gratings''' (AWG) are commonly used as [[Optical add-drop multiplexer|optical (de)multiplexer]]s in [[wavelength division multiplexing|wavelength division multiplexed]] (WDM) systems. These devices are capable of [[multiplexing]] a large number of [[wavelength]]s into a single [[optical fiber]], thereby increasing the [[Transmission (telecommunications)|transmission]] capacity of [[optical communication|optical networks]] considerably.
The devices are based on a fundamental principle of [[optics]] that [[light wave]]s of different wavelengths [[Interference|interfere]] linearly with each other. This means that, if each [[channel (communications)|channel]] in an [[optical communication]] network makes use of [[light]] of a slightly different wavelength, then the light from a large number of these channels can be carried by a single optical fiber with negligible [[crosstalk (electronics)|crosstalk]] between the channels. The AWGs are used to multiplex channels of several wavelengths onto a single optical fiber at the transmission end and are also used as [[demultiplexer]]s to retrieve individual channels of different wavelengths at the receiving end of an optical communication network.
== Operation of AWG devices ==
[[Image:Arrayed-Waveguide-Grating.svg|center|frame|The incoming light '''(1)''' traverses a free space '''(2)''' and enters a bundle of optical fibers or channel waveguides '''(3)'''. The fibers have different length and thus apply a different [[Phase (waves)|phase shift]]. At the exit of the fibers '''(3)''' the light traverses another free space '''(4)''' and interferes at the entries of the output waveguides '''(5)''' in such a way that each output chanel receives only light of a certain wavelength. The orange lines only illustrate the light path. The light path from '''(1)''' to '''(5)''' is a demultiplexer, from '''(5)''' to '''(1)''' a multiplexer.]]
Conventional [[silica]]-based AWGs schematically shown in the above figure, are [[planar]] lightwave circuits fabricated by depositing [[doping (semiconductor)|doped and undoped]] layers of silica on a [[wafer (electronics)|silicon substrate]]. The AWGs consist of a number of input ''(1)'' / output ''(5)'' couplers, a free space [[wave propagation|propagation]] region ''(2)'' and ''(4)'' and the grating [[waveguide]]s ''(3)''. The grating consists of a large number of waveguides with a constant length increment (ΔL). Light is coupled into the device via an optical fiber ''(1)'' connected to the input port. Light [[diffraction|diffracting]] out of the input waveguide at the coupler/slab interface propagates through the free-space region ''(2)'' and illuminates the grating with a [[normal distribution|Gaussian distribution]]. Each wavelength of light coupled to the grating waveguides ''(3)'', undergo a constant change of [[phase (waves)|phase]] attributed to the constant length increment in grating waveguides. Light diffracted from each waveguide of the grating [[interference|interferes]] constructively and gets [[focus (optics)|refocused]] at the output waveguides ''(5)'', with the spatial position, the output channels, being wavelength dependent on the array [[Phase shifting|phase shift]].
[[de:Arrayed-Waveguide Grating]]
== External links ==
* [http://www.c2v.nl/products/software/support/files/A1998003B.pdf Nice images]
[[Category:Optical devices]]
[[Category:Photonics]]
[[Category:Optics]]
[[Category:Fiber optics]]
[[Category:Multiplexing]]