Thank you so much alistu. but my concern is not using RZ /NRZ or ofn-off keying but as we increase dat rate upto 100 Gbps or 112 Gbps obviously we need modulation formats which accomodate more than 2 bits per symbol such as QAM, PM-DPQSk etc which require a coherent detection system. it is ok to see output by putting all for single channel and checking the output(though i hhhave not tried) but whenever i start design and with all recent research available if i intend to design a 100 channel WDM high data rate system with these advance modulation formats it is tiring to design or externally connect transmitter to each channel. i want to know if i can design such system using a single module as WDM transmitter and simply chosing a new format .