. The new wave is known as the idler . Four wave mixing causes undesirable effect in optical transmission when the probe wavelength is close to the signal wavelength as the resulting wave has the frequency of the input signal. For instance, in DWDM channels which are separated by 100 GHz, three waves of frequencies GHz and GHz will give rise to a wave of frequency GHz, which is another channel in the WDM. Thus four wave mixing would cause noise and cross talk.
When the frequencies of the pumping waves are equal ( ), one gets what is known as Degenerate Four Wave Mixing (DFWM) for which the idler frequency is
, where is the frequency of the probe signal. Thus if we take two continuous pumping waves of same wavelength and a signal of a different wavelength, the output would be modulated the same way as the signal, though with a converted frequency.
DWDM Network Topology
DWDM was originally meant to be supported by a point-to-point network topology. Point-to-point topology in its most elementary form, consists of a transmitter and a receiver with a fiber link between them. The first generation WDM
. The new wave is known as the idler . Four wave mixing causes undesirable effect in optical transmission when the probe wavelength is close to the signal wavelength as the resulting wave has the frequency of the input signal. For instance, in DWDM channels which are separated by 100 GHz, three waves of frequencies 
GHz and 
GHz will give rise to a wave of frequency 
GHz, which is another channel in the WDM. Thus four wave mixing would cause noise and cross talk.
), one gets what is known as Degenerate Four Wave Mixing (DFWM) for which the idler frequency is 
is the frequency of the probe signal. Thus if we take two continuous pumping waves of same wavelength and a signal of a different wavelength, the output would be modulated the same way as the signal, though with a converted frequency. 
