In-band optical signal-to-noise ratio monitoring for suppression of effects of both polarization mode dispersion and the polarization extinction ratio of a polarization beam splitter based on enhanced tracking of the principal states of polarization

An improved in-band, optical signal-to-noise ratio (OSNR)-monitoring method suppressing the effects of both polarization mode dispersion (PMD) and the polarization extinction ratio of a polarization beam splitter (PBS) by using enhanced tracking of the principal states of polarization is proposed and theoretically and experimentally demonstrated. The experimental results show that the OSNR measured by using the proposed method agrees well, within an error of 1 dB, with the OSNR measured by using an optical spectrum analyzer (OSA). The proposed per-channel OSNR monitoring method was demonstrated to be applicable to future dynamically-reconfigurable wavelength-division-multiplexed (WDM) optical networks.