Operating regimes of an optical coupler combined fiber laser system

Rate equations have been used to study an optical coupler combined Er3+-doped fiber laser system, in which a common mirror attached at one of the coupler output ports is shared by two constituent lasers. Three regimes may be identified for the system depending on the relative magnitude of the wavelength difference δλ between the two constituent laser fields to the reflection band of the fiber gratings. Taking into consideration the transmission features of the coupler-mirror combination, appropriate boundary conditions have been established according to the operation regimes of the compound system. After neglecting the backgrounds losses of the fiber, rate equations have been simplified to a set of algebra equations. Based on the algebra equations, we discussed in detail the case where the laser field generated by the first laser with a wavelength slightly different from that of the field oscillating inside the second laser, is injected into the other laser by the common mirror, leading to a decreased gain for the oscillating field.