Hello Tayyab
Basically AWG is a component or devise used to combine or saprate the signals with different wavelengths.For better understanding you can go through the link i have mentioned below
http://www.rp-photonics.com/arrayed_waveguide_gratings.html
According to your Question use of NxN array waveguide grating as 1×4 array waveguide grating,you can use this as the 1×4 AWG as this depends on several values like number of wavelengths,coarsness,on which port you applying the signal.For detailed information about AWG working and concept,go to optisystem samples and component detailed description.Here i have mentioned some papers from optiwave smaples and a paper link with practical specification Data sheet of AWG.
http://www.enablence.com/media/pdfs/Datasheet_OCSD_AWG_Other_NxN_APRTE_0.pdf
For better information please specify the objectives,so that all optiwave members able to help you.
Regards