What is optical multiplexing and what could it mean for technology?

Fortunately for the world’s current connectivity needs, the technical characteristics that make fibre optic possible are very basic – scientifically speaking, of course. However, this also means that innovations could be discovered very frequently indeed, and fibre optic will increasingly be used to transmit data more efficiently in the future.



Physics is what makes the “magic” of fibre optic possible

Light travels at almost 300,000kph. There’s no faster element in the known universe, at least according to the laws of physics as we understand them so far. Because of its speed and ability to manifest itself on different wavelengths, interestingly, there are actually different “types” of light, including the light visible to the naked eye, ultraviolet, infrared, etc.


When it comes to connectivity, we’re most interested in the technical characteristics of fibre optic. That’s the glass filaments – about the thickness of a human hair – that can transmit light pulses over long distances without any breakups or distortions. Crucially, electro magnetism doesn’t come into play with fibre optic, as is the case with other types of cable, such as copper.



Multiple wavelengths mean multiple signals

The fact that light moves through space on certain wavelengths means it’s possible to actually increase its versatility as a means of connectivity by making very slight modifications. We can make tiny alterations to light waves without modifying their nature within the spectrum of light that can be seen by the human eye. And that’s exactly how we end up with both monomodal fibre optic and multimodal fibre optic. The former moves a single beam of light through the fibre, while the latter uses the same filament – albeit a bit thicker – to carry more than one beam over different wavelengths.



Optical multiplexing (OM)

The virtues and reliability of fibre optic as a means of transmission are clear, given it’s now practically the standard in wired connectivity. But because light is a property of the physical world, it has no qualities that the digital world can really harness. Receivers are needed at the end of a fibre optic cable to “translate” the presence or absence of light within a pulse into ones and zeros respectively.


These types of signal receivers and decoders are better known as optical multiplexers (OM). They’re essentially used to isolate and “translate” light pulses across different wavelengths that have been transmitted over a single multimodal fibre optic cable. Using an OM means you can exponentially increase the capacity of an individual signal transmission system to deliver huge amounts of data, often over hundreds or even thousands of kilometres.



The difference between DWDM and CWDM

DWDM means dense wavelength-division multiplexing. Essentially, that means you can transmit and decode a number of compacted signals over different wavelengths, allowing for greater volumes of information to be transmitted with each signal. CWDM stands for coarse wavelength-division multiplexing.


This type of OM is used for transmitting a maximum of up to eight simultaneous signals over fibre optic, but at a lower cost than other optical multiplexing systems. It also requires less energy, making it more sustainable in the longer term.

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