Suppression of the intensity noise in distributed feedback fiber lasers by self-injection locking

We proposed an experimental investigation into the relative intensity noise (RIN) characteristics of erbium-doped distributed feedback fiber lasers (DFB-FL), and presented a simple self-injection locking (SIL) configuration of DFB fiber laser to suppress its RIN in this paper. Performance of self-injection gives a sufficient proof, that it can suppress the RIN effectively by injecting the feedback laser into the cavity. When pump power is 25 mW, the RIN of the DFB-FL is suppressed about16 dB/Hz by the self-injection locking method around the relaxation oscillation frequency, and the resonance peak of the DFB-FL shifts to lower frequencies obviously from 74.5 to 41.0 kHz. Then, the relaxation oscillation frequency and RIN characteristics are measured at different pump powers. With the increasing of pump power from 15 to 35 mW, the relaxation oscillation frequency has a slower increase in the slope efficiency in the locked fiber laser than the unlocked, and the RIN has a more rapidly decrease in the same condition. The results have potential application in high sensitive fiber sensors and optical communication.