Perlin Noise has nothing to do with the combination of different octaves.
Noise that is generated by adding up octaves is generally called FBM ( Fractal Brownian Motion ).
Althoug the article you refered is confusing about that, it is a good introduction to FBMs.
To create the FBM, you need some way to generate noise at different frequencies.
Perlin Noise is a method you can use to generate such octaves, it belongs to
the family of gradient noise methods.
Ken Perlins [url="http://www.noisemachine.com/talk1/"]website [/url]introduces the algorithm.
[url="http://mrl.nyu.edu/~perlin/noise/"]Here [/url]you can find the reference implementation of Perlins latest algorithm.
However most tutorials use value noise to generate the octaves and falsely call it "perlin noise".
A tutorial that shows a simple value based noise is devmag.org.za/2009/04/25/perlin-noise/. ( the author calls it "perlin noise" but in fact it is simple value noise )
Value noise is faster to compute but has a lower quality.