Modal gain measurements in a fiber Bragg grating stabilized laser module for erbium-doped fiber amplifiers

Novel modal gain spectral measurements are presented in an EDFA 980 nm diode laser pump module with a fiber Bragg grating (FBG) that provides wavelength-selective optical feedback. Measurements are shown at several device temperatures and injection currents. Gain clamping is observed at the wavelength of the FBG and the wavelength of the free-running laser, depending on the device current and the spectral detuning between the laser and the FBG. The paper provides key experimental evidence for the basic theory of the locking range.