Low-Cost Polarization Scrambling Using a Single Re-Entrant Polarization Controller

We present a low-cost mechanical polarization scrambler capable of near 100 KHz scrambling speed using a single modified Lefevre controller. By reusing the same controller, many sections can be implemented and the scalability promises higher scrambling rates. The device is wideband, polarization-independent and low-loss providing a degree-of-polarization of less than 5%

I. INTRODUCTION

POLARIZATION effects in optical components and equipment can often be mitigated by depolarizing the input light with polarization scramblers [1]–[6]. Polarization scramblers have also been employed in optically amplified communication systems to combat polarization hole burning (PHB) [7]–[8] in the erbium-doped fiber amplifiers (EDFA) and polarization dependent gain. Polarization scrambling is useful in eliminating the polarization sensitivity of certain measurements and in the mitigation and emulation of PMD [9]. Fast polarization scrambling is also useful when using sub-burst error distributed polarization scrambling to mitigate the effects of PMD [10]. Such fast scramblers are typically made of lithium niobate [4], [5] or acousto-optic crystals [6] and can therefore be polarization sensitive, have high insertion loss and/or may be costly. Designs have been demonstrated based on interferometric depolarization [1], [2] but such methods tend to distort data signals and can only be used before modulation.