The thermal activation of the bismuth active center associated with silicon (BAC-Si) in bismuth/erbium-codoped optical fiber (BEDF) has been investigated in terms of temperature, dwell time, and cooling rate. The experimental results show that temperature and dwell time have significant effects on activation of BAC-Si, and the underlying mechanism is further discussed. Especially, through the optimization of these dynamic parameters, the thermal activation of BAC-Si is achieved with a maximum enhancement ∼ 2.5 times of peak luminescence intensity and 1.6 dB/m increment of the on–off gain at ∼ 1405 n m . Such discovery clearly indicates that thermal treatment with optimized temperature, dwell time, and cooling rate could be an effective way to activate BAC-Si in BEDF.