The authors have investigated the most optimal configuration of high density combined wavelength division multiplexing (HDWDM) system. Generally our investigated combined WDM system model is offered as an optical network for future Internet design and this transmission system model can be also considered under the concept of next generation optical network (NGON). As well as, cannot be excluded that such optical signal transmission mode can be topical in case of different telecom operator networks convergence. These will result as a necessity to transmit over single optical fiber signals with different modulation formats and / or different bit rates.