To improve the robustness of the polarization modulation (PM) technique applied in dual-polarized satellite systems, a zero-forcing aided demodulation (ZFAD) method is proposed to eliminate the impairment to the PM from the depolarization effect (DE). The DE elimination is traditionally dependent on the pre-compensation method, which is based on the channel state information (CSI). While the distance between communication partners in satellite systems is so long that the CSI can not be always updated in time at the transmitter side. Therefore, the pre-compensation methods may not perform well. In the ZFAD method, the CSI is estimated at the receiver side and the zero forcing matrix is constructed to process the received signal before demodulating the PM signal. In this way, the DE is eliminated. In addition, we derive the received signal-to-noise ratio expression of the PC and ZFAD methods with the statistical channel model for a better comparison. Theoretical analysis and simulation results demonstrate the ZFAD method can eliminate the DE effect effectively and achieve a better symbol error rate performance than the pre-compensation method.

In this letter, a novel transmission scheme is proposed to eliminate the polarization dependent loss (PDL) effect in dual-polarized satellite systems. In fact, the PDL effect is the key problem that limits the performance of the systems based on the PM technique, while it is naturally eliminated in the proposed scheme since we transmit the two components of the polarized signal in turn in two symbol periods. Moreover, a simple and effective detection method based on the signal's power is proposed to distinguish the polarization characteristic of the transmit antenna. In addition, there is no requirement on the channel state information at the transmitter, which is popular in satellite systems. Finally, superiorities are validated by the theoretical analysis and simulation results in the dual-polarized satellite systems.

Some optical components have polarization dependent loss (PDL), which degrades the performance of optical measurement systems. Various PDL suppression methods have been proposd, most of them have rather complicated structures. In this paper we propose a new simple method for PDL suppression, in which a single birefringent element is concatenated to a PDL device with their birefringent axes offset by π/4. The effectiveness of the proposed method is verified by experiments, that is, polarization dependent loss variation amplitude V of a device relative to its average loss is reduced from 90% to 2% by using a 2 m long PANDA fiber for an LED light source whose central wavelength λ0 and spectral width Δλ are 847 nm and 55 nm, respectively. Furthermore, for an SLD light source with λ0=1539 nm and Δλ=71 nm, V as much as 80% is reduced to 2% by using the same PANDA fiber.