What is AWG (Arrayed Waveguide Gratings)?

http://www.fiberoptics4sale.com/wordpress/what-is-awg-arrayed-waveguide-grating/ http://www.fiberoptics4sale.com AWG stands for Arrayed Waveguide Gratings. AWG is mostly used as multiplexers and demultiplexers in WDM fiber systems. The function of a multiplexer is to combine different wavelengths, which means different colors, of optical signals from different fibers into one single fiber. As shown in this picture. The input is a ribbon fiber, which is a bunch of individual fibers bonded in a ribbon. Each fiber carries a different wavelength of light, such as red in one fiber, blue in another fiber, yellow in another fiber, etc. These different colored lights are combined by the AWG, which is packaged in the box, into a single fiber. This single fiber then carries the signals along a long distance to the far end. This significantly saves fiber cost and increases the capacity of the communication system. In the far end receiving side, the different colored lights need to be separated into different fibers for signal processing. This is when a Demultiplexer comes to place. A Demultiplexer is actually a multiplexer used in the reverse direction. Different colored lights come in a single fiber, and enters from the right side. These different colored lights are then separated by the AWG into different fibers in the ribbon. Red goes to fiber one, blue goes to fiber 2, etc. So now you know what is a multiplexer and demultiplexer, and the role that AWG plays. Now let's get inside the package and see exactly how a AWG works to separate and combine different colored lights. A AWG is made of five parts. These five parts are all made on a silica chip. The first part is the input waveguide, light that includes many channels, such as 16, 32 channels gets in from the input waveguide. The second part is a free propagation region. This is a bulk area where light gets freely dispersed and diffracted. The third part is the arrayed waveguides. There is a fixed length difference between neighboring waveguides. In such a way, that waveguide 1 is ΔL longer than waveguide 2, waveguide 2 is ΔL longer than waveguide 3, and so on. The fourth part is another free propagation region where like gets freely dispersed and diffracted again. And the last part, the fifth part, is output waveguides, where each color goes to a different waveguide, dark blue goes to 1, light blue goes to 2, green goes to 3, and so on. Now let's see how these parts all work together to separate the colors. The incoming light, which includes many channels, gets in from the input waveguide. Then it enters the free propagation region. Here is light diffraction happens. Each color, which means each channel of light, are separated into many copies, so each waveguide in the array has a copy of each color. Then in the third part, the arrayed waveguides, each copy gets a different phase delay since they are travelling different length of paths. Then in the fourth part, each copy is diffracted again, and are separated into many copies themselves as shown here. So now at the input edge of the output waveguides, the same color copies are having a interference. Now remember each copy has a different phase delay, So there is only one interference this is constructive, so all signal powers for this color get focused here. This is more clear shown in the right side picture. All other output waveguides also get interference for this particular color, but they are out of phase so no signal power actually gets coupled into them. Since each color has a difference wavelength, the phase delays are different from color to color in the arrayed waveguides, so each color has a different constructive interference spot, that is dark blue color get constructive interference on port 1 in the output waveguide, light blue color gets constructive interference on port 2, green color gets constructive interference on port 3, and so on. This is how a AWG works as a demulplexer to separate different colored light into their own individual fiber. A multiplexer works in the same principle, only this time, it is working in the reversed way. So there you have it. Please leave your comment below if you'd like to see other topics. Don't forget to visit fo4sale.com for more free fiber optic tutorials. I will see you in the next video!