i fiber optics lecturewe are going to talk about wavelength division multiplexinga technique used to share an optical fiber among many different signals hall simultaneaouslywavelenght division multiplexing uses that fact that light can be traveling down the fiber simultaneously from many diferent colors of why without mixing or interfering with each other.we've seen this all the time I liked being dispersed fire prism where all the different colors is like a are able to move through the air simultaneously until the reach the prism which separates them into their component colors we can do exactly the same saying apple fiber so let's use a large core plastic fiber and some laser pointers to see exactly what's happening wavelength division multiplexing is used1.21:this is a large stick fiber and will use a red laser pointerandrew modulated to show how signals are typicalle modulatedand the optical fiber now to I read laser pointer lets a degree major pointer and as you can see weekend modulate the green light other red light isn't bothered at all by the second light traveling in the fiber if we had other colors and laser pointers we can even had more colors and this is a good example how to callers can be transmitted simultaneously down the fiber without interfering whit each otherchester show france for the collars let's reverse it will take the green ligh and send it down the center is a5 her and then we'll start sending red light through separately and as you can see exactly the same thing happens the green light is not bother to now and the modulation is a red light in same fighter.this technique was first used wavelength division multiplexingin sending ste two signals over 1 fiber the same time simply need to cut waste to couple the light and two and have the fighter to different sources to differ receivers and optical filters those filters stop one color flight and let the other trough so the two branches of the collar coupler on the receiver and can carry different signals to read detectors simultaneously actually that pine systems passive optical networks for fiber to the home work somewhat similar to this today except they're sending fiber signals and opposite directions and different colors the same technique applies 3.31it's typical sense networks today to use wavelength division multiplexing i'm very long distance lakes here we use dense wavelength division multiplexing made more than sisty channels tightly spaced with fiber amplifiers for repeaters we also can use coarse wavelength division multiplexing with fewer channels wider spaced for those we need low water P fiber