In this paper, we propose multi lambda injection locking in a single mode Fabry-Perot laser diode and experimentally analyze its effect on various characteristics of Fabry-Perot laser diode. We consider mode of the injected beam, number of input injected beams, wavelength detuning, and injected power as important parameters in the analysis of suppression of the dominant mode and hysteresis width. The power required for injection locking is proportional to wavelength detuning, which is one of the important parameters for implementing latching device, switching device, and various other optical devices using single mode Fabry-Perot laser diode. In multi-lambda injection locking, the amount of power required for the injected beam with and without suppression of self-injected mode plays an important role, and hence, is Laken into account in our experiment. The spectrum domain output of three- and fourinput NAND gate is shown to verify the concept of multi-lambda injection locldng. We observe ON/OFF contrast ratio of more than 40 dB when all beams are injection locked, whereas about 1.5 dB ON/OFF contrast ratio in all other combinations of input beam injection. The analysis of multi-lambda injection locking can be used for multi-input optical devices such as multi-input logic gates, latches, and switches.