Abstract This work demonstrated the distributed feedback laser grating order effects on optical system in the presence of NRZ-RZ line coding schemes. Max lighted signal form power variations are studied with spectral base wavelength band variations through optical fiber based on first various distributed based band feedback laser (DFB) grating order. The total lighted form base power band through optical fiber based on first different DFB laser grating order is estimated. The max electrical base signal band power form variations with spectral base frequency form band variations through photo-detector based on various DFB laser grating order is demonstrated. Total electrical based power band form through photo-detector based on various DFB laser grating order is also clarified. Max base band power form band amplitude with time through photo-detector based on different DFB laser grating order is clarified. Max Q base band form is studied numerically with DFB laser grating order variations.