Maximum fractional delay achievable on slow light propagation through an erbium-doped optical fiber

The important issue in slow light delay lines is not merely the achievement of large time delay but to produce large fractional since this parameter roughly measures the information storage capacity of the optical medium. We will study delays for power-modulated signals. The modulation can be directly imposed on the beam by driving the laser control box from a function generator, and we define fm as the modulation frequency. The fractional delay is defined as F=tdfm, where td is the time delay and fm is the modulation frequency. The modulation frequency is called the optimal modulation frequency corresponding to the largest fractional delay. In this paper, we study the maximum fractional delay achievable by slow light propagation in an erbium-doped optical fiber at room temperature. Influences of the ion density, fiber length and the input power on the fractional delay are studied. Based on our discussion the optimization parameters should be selected in order to obtain relatively large fractional delay and slowdown of group velocity.