AWG: Arrayed Waveguide Grating Basics for Optical MUX/DEMUX

This page describes the basics of an AWG (Arrayed Waveguide Grating) used in optical fiber communication. It explains the operation of an Arrayed Waveguide Grating (AWG) as an optical MUX and DEMUX. The features and characteristics of the Optical Arrayed Waveguide Grating are also discussed. AWGs work on the principle of interferometry and are widely used as optical multiplexers and demultiplexers.

Operation of AWG (Image):

Image alt: Arrayed Waveguide Grating based Optical MUX DEMUX

Let’s delve into the operation of an AWG as an optical demultiplexer:

• Step 1: As shown in the image, an incoming light signal containing all wavelengths ($\lambda_1$, $\lambda_2$,…, $\lambda_n$) is fed through an optical fiber (F) into the input cavity or input coupler (designated as ‘S1’) of the optical AWG.

• Step 2: This multiplexed signal then passes through the free space portion of ‘S1’.

• Step 3: Next, the light is divided into an array of waveguides. Here, a phase delay proportional to the wavelength is introduced to the optical signals as they pass through the different waveguides, which have varying lengths.

• Step 4: These phase-delayed signals are then directed to the output cavity or output coupler (designated as ‘S2’). This cavity is connected to multiple optical fiber cables. At this stage, after passing through different lengths of waveguides, the light signals interfere with one another. Consequently, each output optical fiber receives a unique wavelength of light with maximum amplitude.

• Step 5: Finally, using multiple optical fiber cables, the different wavelengths of light are extracted as separate outputs.

For an AWG to function as an optical multiplexer, the reverse operations of the steps mentioned above take place. Individual light signals with different wavelengths are provided as input at location ⑤ of the AWG, and the multiplexed output is derived from location ① of the AWG.

Features or Characteristics of Optical Arrayed Waveguide Grating

The following are the key features of Optical Arrayed Waveguide Gratings:

• As mentioned, they are used as optical multiplexers. This application is crucial in DWDM networks to multiplex various WDM channels into a single fiber cable.

• They are also used as optical demultiplexers at the receiver end of DWDM networks.

• AWGs find application in OADMs (Optical Add-Drop Multiplexers), which are essential components of long-haul fiber optic communication systems.

• They are employed in FTTx optical systems, for example, as CWDM MUX and DEMUX units.