Passive fiber ring flip-flop memory based on polarization dynamics

Abstract

Optical storage devices are essential elements of future ultra-high bit-rate fiber communications systems in which they will find applications to various vital functions. Pulse pattern storage has been demonstrated in various fiber loop devices [1] that involve pulse control techniques in order to provide timing stability of the bit patterns. Most of these stabilization techniques are based on electrooptic modulation which limits the bit rates to a tenth of Gb/s. Moreover, erasing the data in these storage fiber loops requires switching off the system elect rooptically. Individual bit addressing is therefore impossible, which considerably restricts the functionality of the devices. We investigate here the possibility of developing a new type of all-optical fiber loop storage device. This device consists of a simple nonlinear passive fiber ring resonator synchronously and coherently pumped by a cw mode-locked train of ultrashort pulses. It is well known that this system exhibits rich nonlinear dynamics, in particular, optical bistability which is a feature naturally suited for applications to optical storage. However, erasing the data in an optical bistable element requires to switch off the holding beam and is therefore not practical. Recently, Haelterman et al. [2] have studied the polarization dynamics of nonlinear dispersive ring cavities with cw pump and have shown that these devices exhibit a polarization symmetry breaking characterized by a pitchfork bifurcation. This feature can be applied to the development of a set-reset flip-flop all-optical fiber loop pulsed memory. This work aims at presenting the results of a preliminary investigation of such a storage device.