From Fiber Optic Essentials

In WDM systems a number of wavelength channels carry independent signals through
the optical fiber. Thus, there is a need to multiplex and demultiplex a number of
wavelengths, and arrrayed waveguide gratings are devices that can perform this
operation very efficiently with low losses. AWGs capable of multiplexing up to 1080
channels with 25-GHz spacing have also been demonstrated. The AWG is a planar
device (usually fabricated on a silicon substrate) and consists of a series of input
waveguides connected to a planar waveguide that is coupled to an arrayed waveguide
structure as shown in Fig. 12.13. The arrayed waveguides are then connected to a
series of output waveguides via another planar waveguide. The adjacent waveguides
of the arrayed waveguide system differ in length by fixed amounts. Light at different
wavelengths input into one of the input waveguides gets diffracted in the planar
waveguide and gets coupled to the waveguides of the arrayed waveguide structure.
Since the individual waveguides of the arrayed waveguide structure are of different
lengths when the light waves arrive at the second planar waveguide, they interfere
such that different wavelengths get focused at different points and subsequently get

FIGURE 12.13 Arrayed waveguide grating device.

FIGURE 12.14 Demultiplexed output from an AWG.

coupled to different output waveguides. Thus, the various wavelengths that were
coupled into a single input waveguide get demultiplexed and exit from different
outputs. If this device operates in reverse, it will act as a multiplexer.

Figure 12.14 shows the demultiplexed output from different waveguides of an
AWG; the channels are spaced by as little as 50 GHz (corresponding to a wavelength
spacing of 0.4 nm). The insertion loss of the device is typically less than 5 dB, the
wavelength accuracy is typically better than 0.02 nm, and the bandwidth is about
0.2 nm.

Products & Services
Optical Linear Encoders
Optical linear encoders use fiber optic technology to sense position and displacement.
Interferometers measure distance in terms of wavelength and determine the wavelengths of light sources.
Optical Isolators
Optical isolators are optical devices that allow light to be transmitted in only one direction. They are most often used to prevent any light from reflecting back down the fiber, as this light would enter the source and cause feedback problems.
Fiber Optic Couplers
Fiber optic couplers are optical devices that connect three or more fiber ends, dividing one input between two or more outputs, or combining two or more inputs into one output.
Fiber Optic Cleaning Tools
Fiber optic cleaning and splicing tools are used to connect, adapt, polish, repair, fiber and fiber optic cables. This area includes fiber optic consumables such as polish, swabs, wipes, etc.

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