The information capacity of optical fibers is limited by the lengthening of pulses that are transmitted. The shortness of the pulses makes them difficult to measure electronically. Thus a number of different optical methods have been designed based on autocorrelation using spectroscopy, interferometry, or holography. The advantage of the last method is that it not only measures the length of the pulse from nose to tail, but it also produces an image of the total pulse shape. For demonstration we studied a step-index multimode fiber using light-in-flight recording by holography in a similar way as it has been used to study wavefronts of light or the 3-D shape of objects.