Two section fibre approach to suppression of polarization dependent gain in low PMD distributed fibre Raman amplifier

Application of broadband distributed Raman amplification in low polarization mode dispersion (PMD) fibre can reduce transmission system cost, increase the amplification bandwidth, and extend the link span in the case of suppression huge polarization dependent gain which is the main transmission impairment for low PMD fibre Raman amplifiers (FRAs). To suppress PMD, we report herein a novel approach to optimize parameters for the first section of fibre, namely the length and PMD. In addition, we calculate the polarization dependent gain (PDG) for the case of periodically spun fibre as a function of pump light degree of polarization (DOP). The low value of pump DOP can be provided with the help of depolarizer or polarization multiplexing of pump laser diodes. As a result of temperature fluctuations, pump DOP can reach 10%, and, therefore, PDG value increases to 1 dB. Thus, the suggested cost-effective approach to simultaneous mitigation of PMD and PDG based on two-section fibre shows better results as compared to the results of application of pumps polarization multiplexing or depolarizer.