this conclusion is crucial for the interpretation of fringes:
source: http://earth.esa.int/workshops/ers97/program-details/speeches/rocca-et-al/
Accordingly, one color cycle means an elevation change of half the wavelength of the sensor along the line of sight.
To get absolute change values, these fringes need to be unwrapped (subsequently explained with ALOS data [24 cm wavelength])
Source: http://vldb.gsi.go.jp/sokuchi/sar/mechanism/mechanism04-e.html
This is also a nice text written in ‘normal’ words.
It originates from a straight-to-the-point FAQ about interferometry:
http://vldb.gsi.go.jp/sokuchi/sar/qanda/qanda-e.html