Gain Flattening Approach to Physical EDFA for 16 × 40 Gb/s NRZ-DPSK WDM Optical Communication Systems

We are using different approaches to gain flattening in EDFAs without using additional components; i.e., gain flattening filter, dispersion shift fiber, periodic gratings, etc. By using gain flatten approach 3, it is possible to achieve the transmission of sixteen channels at 40 Gb/s wavelength division multiplexing (WDM) over a transmission distance of 490 km by single-mode fiber and dispersion-compensating fiber at a span of 70 km with channel spacing of 200 GHz. We observed the bit error rate less than 10^-9 and power of received signal more than -5 dBm with NRZ-DPSK format.