PMD is an open source tool for analyzing Java code errors. Unlike other analysis tools, PMD learns code errors through static analysis. In other words, report an error without running a Java program. PMD comes with many rules that can be used directly, which can be used to find many problems in Java source programs.

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Polarization mode dispersion (PMD) refers to the polarization dispersion in single-mode fiber, which is caused by the tiny asymmetry of the fiber cross section. This asymmetry causes two fundamental polarization modes perpendicular to each other to propagate at different speeds. Because of dispersion, that is, pulse broadening, when the receiver receives this composite pulse, it is wider than the pulse at the transmitting end.

In the actual single-mode fiber, the fundamental mode contains two mutually perpendicular polarization modes. In the process of propagating along the optical fiber, due to external influences such as temperature and pressure, the two modes are inevitably coupled, and their propagation speeds are different, which leads to the broadening of the optical pulse, which is equivalent to random dispersion. With the increase of transmission rate, the influence of this dispersion on communication system becomes more and more obvious, which cannot be underestimated. have