The effect of narrow band-pass filter's group-delay ripples on WDM optical communication systems

We have investigated the effect of narrow band-pass filter's group delay ripples on the 10 Gbit/s amplitude-shift-keying non-return-to-zero (ASK_NRZ) and differential-phase-shift-keying non-return-to-zero (DPSK_NRZ) wavelength-division-multiplexing (WDM) optical communication systems, which support the huge capacity in the information transmission and display backbone networks. For both ASK and DPSK, there is a peak at a ripple frequency close to the signal data rate in the EOP (eye-opening penalty) vis Frequency of Ripple curve. The EOP of DPSK_NRZ is better than that of ASK_NRZ in the higher ripple frequency region. Through numerical simulation, it's found that the ripple amplitude basically determines the system performance. These results will be helpful to design the large-scale transmission systems and define such narrow band-pass filter design parameters.