An amplifier for amplifying an input signal in a frequency band, has a quadrature signal divider for dividing the input signal into first and second components. The multimode fiber amplifier includes a core configured to receive an input image that includes a plurality of input beams spanning a range of incidence angles and to propagate at least some of the input beams as different ones of a plurality of transverse modes along the core. The destination may be a secondary storage device. The system also includes a detection system. The digital logic circuit that receives the first frequency divider output signal and the first time-delayed clock signal and outputs a signal indicating the loss of the input clock signal if there is no first time-delayed clock signal for a cycle of the first frequency divider output signal.