Crosstalk reduction in fiber links using double polarization

The fiber optic link is one of the main segments of up-to-date telecommunication systems. Developing low cost, ultra reliable systems with very low latency for massive machine to machine and enhanced broadband mobile networks is a hot research topic. Motivated by this we investigated the polarization multiplexing technique applicable in fiber optic links because it can be used for increasing the transmission capacity. In the present paper a novel approach, the double polarization multiplex method is investigated. In that case the crosstalk between two polarization states is one of the main issues. As a result of crosstalk, the two channels composed by double polarization can disturb each other significantly. Crosstalk can appear due to any imperfection in the fiber and in the optical circuitry of the transmitter and receiver. In this paper, we propose a new method for reducing the effect of crosstalk even in the case of high-speed long-distance transmission. The applicability of the new concept is validated by experiments. A bit error rate better than 10 −6 has been achieved over a 7 km long fiber carrying 12 Gbit/s NRZ modulation. That result is significantly better than the already published experimental data using 2, 5 Gbit/s bit rate. The cross polarization discrimination is also improved by 10–15 dB.