A simple M-branch diversity receiver model for PMD-induced penalty mitigation in IM-DD optical transmission systems

We propose a novel M-branch diversity receiver for PMD mitigation in an intensity-modulated direct-detection (IM-DD) optical transmission system. The receiver diversity is realized in the optical domain by means of a few additional fixed optics, whereas the dispersion penalty is mitigated in the electrical domain after optical-to-electrical conversion by incorporating a normalized-threshold generalized selection and combining (NT-GSC) diversity technique, which has gained a lot of attention more recently. The major motivation behind the proposition of this scheme is not to authorize a substantial increase in the receiver complexity, yet attaining a significant gain. Numerical results show that even without deploying any costly optics/electronics, complex electronic equalizer, or an unrealistic dynamic polarization controller, the proposed scheme exhibits a reasonable improvement in PMD tolerance of about 1.7 times over a conventional IM-DD receiver at an optical signal-to-noise ratio (OSNR) penalty of 1 dB for a bit error rate (BER) of 10
^-3
in 40 Gb/s transmission scenario, when the number of diversity branches of M = 3. Furthermore, we show that the NT-GSC scheme can contribute to reduce noise in the resultant signal, which enables to achieve a gain of 1.2 dB in the case of a back-to-back transmission. In addition, we demonstrate by a simulation study that a supplementary gain can be attainable by further increasing the number of diversity branches, which will increase the cost and complexity of the proposed receiver.