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I am curious to know how exactly does the fiber optics works. I understand the basic concepts of the fiber optics communications but am curious to know if there is a way to send multiple signals in same core at the same time in the fiber optics? How is it possible? Is there a way you can send light of different wavelength and able to detect them at the rx end?

dr3patel
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  • Same way as with those other photons we use. Only the mixing and discrimination differ. – Ignacio Vazquez-Abrams Mar 22 '15 at 00:43
  • Different color sources & detectors. – Optionparty Mar 22 '15 at 00:58
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    It's called WDM for "wavelength-division multiplexing", in direct analogy with FDM (frequency-division multiplexing) used in RF communications. – Dave Tweed Mar 22 '15 at 01:09
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    Light is an electromagnetic wave just like the radiofrequencies, so you can use it exactly in the same manner: send different signals one after the other, on different frequency bands (<-> wavelength, giving the color for the waves in the visible frequency range), or using encoding. – Mister Mystère Mar 22 '15 at 01:22
  • @Mister Mystère, there's no need to send signals on different frequencies one after the other, indeed, sending them simultaneously (or at random times) is the point of multiplexing. – Jeanne Pindar Mar 22 '15 at 04:55
  • That is not what I said, I said "or". Those are independent techniques, which could be combined but which generally aren't. – Mister Mystère Mar 22 '15 at 11:52

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This is somewhat oversimplified, but it gets the basics right.

Think of a beam of white light shining into a prism. The output will be a rainbow, which means that the different colors exit the prism at different angles.

A prism will work just fine "in reverse". That is, if you take a series of lasers of different colors, place them where their colors appear in the spectrum from the prism and point each one back into the prism, they will combine to form a multi-colored beam. Send this beam into another prism, and it will split the beam back into its' separate colors. And that's the basic idea.

The details are different, the biggest change being that nobody uses prisms, but dichroic filters instead.

WhatRoughBeast
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In optical fibre, most modulators are laser based. Just like many bandwidths exist in copper wires, a laser can be modulated to occupy many channels too but unlike copper wire, it allows infinite bandwidth provided you are able to use it. There are adders that can add two fibre optic channels. So for example lets say a voice channel and a TCP/IP channel can exist in the same fibre optic link. Or your modulator will allow existence of two or more channels. This is the one main reason we are using Fibre communication. The good example is the country Denmark. There, Radio, TV, Internet are sent over one single fibre link. That is one beautiful country where at the receiver end you can demodulate and send radio signal to the radio, tv signal to tv and network signals to access point/router. So answer to your question is yes.

Although you have to understand when it comes to fibre communications, things are working in the nano or even smaller scale. So Quantum theories come into play especially in demodulation and modulation etc. As the matter of fact some good modulators are based on quantum theories such as "wave particle duality" If you want to learn and understand more of these topics, I suggest you read a book that provides proper basics.

Also note, attenuation of certain bandwidths differ on wavelength. There are mathematical models that take inputs of wavelength and characteristics of laser and fibre optic line and calculate loss. So yes, there can be attenuation is fibre lines too, but far less than copper.

Denis
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    The bandwidth of optical fiber isn't "infinite". It's very high, but still theoretically limited by the carrier frequency. Practically, the total number of channels in WDM is limited by nonlinear behavior in the fiber that starts to degrade the signals when the total power (of all the WDM channels) is too great. – The Photon Mar 22 '15 at 05:20