The influence of InGaAlAs waveguide layer composition on the photoluminescence and electroluminescence in the 1550-nm spectral range of heterostructures based on thin strained In0.74Ga0.26As quantum wells has been studied. An approach is proposed that allows based on the analysis of electroluminescence.to carry out a comparative analysis of the deferential gain in fabricated laser diodes. It is shown that decrease of the molar fraction of aluminum in waveguide InGaAlAs layers matched in lattice constant with indium phosphide leads to falling of integrated photoluminescence intensity, however, laser diodes with In0.53Ga0.31Al0.16As waveguide layers demonstrate a higher differential gain compared to laser diodes with In0.53Ga0.27Al0.20As waveguide.