A novel concept of filters-matching with-demultiplexing window(FMDW) is presented.Spectrum compression based on filters for improving spectral efficiency is analyzed and demonstrated experimentally in 4×10 Gbit/s OTDM systems.Arrayed waveguide grating(AWG) is used as compact spectral device.A home-made multiplexer is applied,and demultiplexing and clock recovery are implemented simultaneously utilizing a simple loop that consists of electro-absorption modulator (EAM) and 10 GHz clock recovery mo...