Arrayed waveguide gratings (AWG) are commonly used as optical (de)multiplexers in wavelength division multiplexed (WDM) systems. These devices are capable of

multiplexing In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource� ...

many

wavelength In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same ''phase (waves ...

s into a single

optical fiber An optical fiber, or optical fibre, is a flexible glass or plastic fiber that can transmit light from one end to the other. Such fibers find wide usage in fiber-optic communications, where they permit transmission over longer distances and at ...

, thereby increasing the transmission capacity of optical networks considerably. The devices are based on a fundamental principle of

optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of optical instruments, instruments that use or Photodetector, detect it. Optics usually describes t ...

, which states that

light wave In physics, electromagnetic radiation (EMR) is a self-propagating wave of the electromagnetic field that carries momentum and radiant energy through space. It encompasses a broad spectrum, classified by frequency or its inverse, wavelength, ra ...

s of different wavelengths do not interfere linearly with each other. This means that, if each channel in an

optical communication Optical communication, also known as optical telecommunication, is communication at a distance using light to carry information. It can be performed visually or by using electronic devices. The earliest basic forms of optical communication date ...

network makes use of

light Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400– ...

of a slightly different wavelength, then the light from many of these channels can be carried by a single optical fiber with negligible

crosstalk In electronics, crosstalk (XT) is a phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. Crosstalk is usually caused by undesired capacitive, ...

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 In electronics, a multiplexer (or mux; spelled sometimes as multiplexor), also known as a data selector, is a device that selects between several analog or digital input signals and forwards the selected input to a single output line. The sel ...

s to retrieve individual channels of different wavelengths at the receiving end of an optical communication network.

Operation of AWG devices

Conventional

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...

-based AWGs, as illustrated in the figure above, are planar lightwave circuits fabricated by depositing layers of doped and undoped silica on a silicon substrate. The AWGs consist of a number of input ''(1)'' and output ''(5)'' couplers, a free space propagation region ''(2)'' and ''(4)'' and the grating waveguides ''(3)''. The grating waveguides consists of many waveguides, each having a constant length increment (ΔL). * Light is coupled into the device via an optical fiber ''(1)'' connected to the input port. * Light diffracting out of the input waveguide at the coupler/slab interface propagates through the free-space region ''(2)'' and illuminates the grating with a

Gaussian distribution In probability theory and statistics, a normal distribution or Gaussian distribution is a type of continuous probability distribution for a real number, real-valued random variable. The general form of its probability density function is f(x ...

. * Each wavelength of light coupled to the grating waveguides ''(3)'' undergoes a constant change of phase attributed to the constant length increment in grating waveguides. * The diffracted light from each waveguide within the grating undergoes constructive interference, resulting in a refocusing of the light at the output waveguides ''(5).'' The spatial position of the output channels is wavelength-dependent, determined by the array phase shift induced by the constant length increment in the grating waveguides.

References

{{Reflist Optical devices Photonics Fiber optics Multiplexing