To realize InP-based monolithic integrated optoelectronic devices and systems, the quantum well intermixing (QWI) technology has been experimentally investigated for the InGaAsP/InGaAsP confinement heterojunction multiple quantum well laser structures herein. The active-area QWI technology realized under P-ion implantation with different energies, different rapid thermal annealing (RTA) conditions, and cycle annealing is investigated, and the experimental results are characterized using photoluminescence (PL) spectra. Experimental results show that the QWI effect can be observed for all the samples with different variables, where the annealing temperature has the most significant effect and the cycle annealing can further enhance the QWI effect. The blue-shift in PL spectra increases with the annealing temperature and time and implantation energy, and the annealing temperature has the greatest effect on the blue shift. Finally, the maximum blue-shift achieved is approximately 116 nm with secondary annealing at 750 ℃ for 150 s when the injection dose and energy are 1×10 ¹⁴ ion/cm ² and 600 keV, respectively. Our findings will benefit future design and fabrication of monolithic integrated optoelectronic devices and systems using QWI technology.