A tunable laser operating near 944 nm is important for micro LIDAR systems. The high power laser would consist of a tunable (and possibly Q-switched) low power fiber laser, the output of which would be amplified using a double clad fiber amplifier. A model of a Nd doped laser using a Gaussian beam approximation for both the propagating pump and the laser mode has been developed. The threshold power and output power for various parameters such as pump absorption and reflectivity have been calculated. The spectral width (linewidth) of a fiber laser under CW operation has been calculated. The laser linewidth varies inversely as the square of the fiber length and inversely as the output power. Shorter pulse width and higher peak power is obtained using a small fiber core under Q-switched operation.