An approach has been suggested for the simulation of a quantum dot reflective semiconductor optical amplifier (RSOA) with wideband optical gain. This model is implemented by superimposing different quantum dot groups with various radii using solution process nanotechnology, which is both practical and frugal. Also, few works have been done, superimposing QD groups in RSOAs. A numerical method has been used for solving coupled rate equations. This method is a perfect approximation for understanding this device; because analytical solutions are not possible to further investigate the model. Using this method, a wideband optical gain of about 30 dB, covering broadband from 460 to 730 nm, has been obtained by using CdS_xTe_{1  -  x} with different mole fractions. Furthermore, this optical gain is not even limited to this value if more groups get exploited. The proposed model results in about 270 nm optical bandwidth, making this device suitable for implementing wavelength division multiplexing in optical networks by designating different channels to various signals. In addition, it shows a high signal-to-noise ratio (about 1000), making it a great candidate for use in optical communications. Using this technique, one step is taken to the development of high-speed broadband WDM passive optical networks. Also, different bands in the lightwave spectrum can be used and only one needs to choose suitable materials for synthesizing QDs to operate in the desired wavelengths.