However, high overhead codes may be powerful enough to perform better than a lower overhead code if the useful data-rate (rate without overhead of parity bits) are kept the same by increasing the bit-rate of the high overhead code. With everything else equal, low overhead codes are clearly desirable since lower overhead represents a more efficient use of available bandwidth. In the simulations conducted, the DGD per uncoded bit is varied from 0 to 103% of the bit period. In conventional systems, the impact of PMD is normally negligible if the average DGD per bit period is less than 10%. The performance of several different FEC codes is studied here via Monte Carlo simulations employing a realistic PMD channel model. There have been studies into the possibility of combining different types of RS codes in an iterative fashion to raise the tolerance level of differential group delay (DGD), but few studies have been made on more effective FEC techniques such as Turbo codes. The weakness of currently employed RS codes is their apparent inability to cope with moderate or high PMD. The advantage of RS codes is that they are well known and easy to implement, and are thus very practical for real world systems. The RS codes employed are capable of correcting multiple bit errors in every codeword while only adding 7% parity bits to incorporate the redundant information needed to correct errors. The current fiber optics industry standard uses low overhead Reed Solomon (RS) codes. Generally, FEC codes add redundant bits so that, when decoded, a number of errors can be detected and/or corrected. This will cause different polarizations to traverse down the fiber at different speeds, causing inter-symbol-interference (ISI).ĭeployed fiber optic communication systems have utilized some form of forward error correction (FEC) coding to detect and correct errors. PMD occurs when the cylindrical symmetry in a fiber is broken due to a noncircular core or a noncircular symmetric stress. Polarization-Mode Dispersion (PMD) is one of the obstacles preventing transmission rates greater than 10 Gb/s in fiber optic communications. This is in contrast to the case of negligible PMD, where high overhead codes perform best. It is demonstrated that for a fixed level of PMD and a fixed data-rate, there is an optimal code overhead. We investigate numerically the usefulness of Turbo and Reed-Solomon coding in the presence of Polarization-Mode Dispersion (PMD) using computer simulations. Note: Author names will be searched in the keywords field, also, but that may find papers where the person is mentioned, rather than papers they authored.Use a comma to separate multiple people: J Smith, RL Jones, Macarthur.Use these formats for best results: Smith or J Smith.For best results, use the separate Authors field to search for author names.Use quotation marks " " around specific phrases where you want the entire phrase only.Question mark (?) - Example: "gr?y" retrieves documents containing "grey" or "gray".Asterisk ( * ) - Example: "elect*" retrieves documents containing "electron," "electronic," and "electricity".
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