NASA and the Speed of Light

By John Nixon 27/09/2011 1


NASA moves from Radio to Laser Light for data transmission.

We have often heard the argument that FTTH is really not needed now that G3 and G4 wireless technology is available. I’m sure I’ve mentioned previously that any radio (wireless) data transmission system will NEVER HAVE the bandwidth of a fibre network. The reason is simple. The amount of information you can modulate onto a given carrier frequency has finite limitations. The higher the carrier frequency, the more modulation you can impress on the carrier. With fibre, the carrier is of course light, not a radio wave. The frequency (or wavelength) of light is almost unimaginably higher than the highest frequency radio carriers available for use.

Today I picked up this very interesting article “NASA to demonstrate Laser beam communications system“. Although it describes communications in space, the principle remains the same. NASA has just run out of bandwidth using wireless and will now adopt light as the communications carrier.

Communications in Outback Australia

Bush telephone R

I’ve been fortunate to have travelled to many countries during my life, but I still continue to enjoy exploring the great Australian outback in my trusty Jeep Cherokee.

Not so long ago I drove from my home on the Gold Coast out to the cotton country in West Queensland, down to Bourke, then Broken Hill, and across to the East coast following the Murray River.

There are smallish towns along the way that always have an interesting history. One also always finds an amazing sense of humour amongst the locals.

I found this makeshift telephone booth in the middle of a quite up-market caravan park somewhere way out in Western New South Wales.

I can’t help feeling that the shack may have been a toilet in a past life, something we call a “dunnny” in Australian argot.

But now it hosts a coin-in-the-slot Telstra telephone.

Fibre-to-the-TV

I receive regular news from the three main FTTH Councils: Asia-Pacific, USA and Europe.

Right now, I must say that from my point of view the European Council provides the most interesting and focussed information.

Their most recent newsletter contained a very interesting paper entitled “Fibre-to-the TV – Taking broadcasting to the next level“.

FTTH is an excellent way of distributing television programming, and there are currently two technologies commonly used to deliver TV channels over fibre.

IPTV or Internet Protocol Television takes a television program or channel and converts the audio/video components into IP packets which are then transmitted over the fibre data link. These packets are interspersed with all the other data traffic: browsing, data downloads and uploads, all the usual internet stuff. But the TV signals require quite large amounts of bandwidth, particularly as we move into HD or high definition images. Thus IPTV can cause bottlenecks on the data link. The second technology, called RF Overlay, can allow broadcasting of hundreds of TV channels without affecting the data throughput.  This is done by adding a third lambda or light wavelength to the two existing ones. This third light “colour” is only used for transmitting TV channels and consequently does not “hog” the data channels.

If a country has an established collection of TV channels (including terrestrial free-to-air and satellite pay TV) it is extremely simple to distribute these over the third wavelength without any modification or processing. Conversion to IP however does require equipment and cost that has to be considered.

For those interested, further information is available on my website: www.onefibre.com.

Another snappy FTTH promotion clip

Again thanks to FTTH Council Europe, a really neat promo clip for FTTH is available in several languages.


One Response to “NASA and the Speed of Light”

  • John, I agree with you that wireless system will always be inferior in comparison to optical communication/fibre system. There is no control whatsoever over the properties of the wireless transmission medium (atmosphere), which it can affect the speed/bandwidth of the transmission signals, however the fibre medium for optical communication signals can be controlled (in their design & manufacturing) to minimize certain physical limitation factors (quantum/shot-noise can be minimized or minimize the wave-guide/material dispersion, etc…) which does affect the bandwidth.

    To control wave dispersions, engineers/physicists have developed soliton fibre cables, soliton lasers, etc… I read in Physics Today magazine a few years ago that physicists had developed some prototype squeezed-state lasers (as an optical transmitter) based on the squeezed coherent quantum state theory. This is how quantum/shot-noise can be minimized (or totally eliminated), because this noise type is the most difficult of all to be eliminated in any communication system. It is present in all wave emitters/transmitters (be it microwave or photonics system). I’m not sure if these squeezed quantum state based devices have been made commercial yet.

    Late Prof. Dan Walls from the University of Auckland was the pioneer in the development of the theory of quantum squeezed light/photon. Many scholars in Physics (both local and overseas) thought that Prof. Dan Walls was our prominent local academic to have come close to be someone who deserve to win a Physics Nobel Prize.