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Polarization Mode Dispersion (PMD) Diagnostics of Installed Fiber Networks


Advanced characterization of installed fibers and specialized diagnostics of PMD have become fundamental before any new fiber network investment.

Polarization Mode Dispersion (PMD) has become the main threat for last generation's optical communication technologies. PMD limits the information transmission capacity in long distance optical telecommunication systems. FiberWork Optical Communications has been worried about this phenomenon for years, specializing itself as one of the most important companies to provide specialized PMD characterization of installed fiber plants.

An audit conducted by FiberWork, involving 2,140 fibers installed between 1997 and 2002 in Brazil, reveals that 19% of such fibers present high levels of PMD and therefore do not comply with the requirements of current transmission technologies such as 10 Gb/s systems. A per-route balanced analysis of the same data shows even worse results: 30% of the sampled route fibers will not comply with 10 Gb/s transmission channels.

PMD requirements for future transmission technologies, such as 40 Gb/s systems, are much tighter. Consequently, the percentage of fibers that will not comply with this technology is even greater, reveals FiberWork´s audit.

According to FiberWork's chief technology officer, Dr. Sergio Barcelos, PMD is a serious problem for 10 Gb/s and for the new optical communication technology that are yet to come.

"High PMD levels mean that fiber network owners will find it difficult to exploit high transmission rates per DWDM channel and will light fewer DWDM channels, thus limiting the future of their fiber networks. Certainly, carriers should avoid spending millions of dollars on the latest high-speed, high-channel-count DWDM system if their installed network PMD can accommodate only a half-dozen 2.5-Gb/s channels.

Although PMD compensation and forward error correction can alleviate the problem, it does it at the cost of bringing complexity and higher investments to the network. Fiber networks are expected to have a profitable lifetime of 25 years. However, if a newly installed fiber bears PMD levels higher than those required by current commercial transmission technologies, then such an investment has not been wise" says Dr. Barcelos.

FiberWork´s chief technology officer, Dr. Barcelos, has introduced a paper on PMD field measurements entitled "Polarization Mode Dispersion Field Measurements - Audit of Newly Installed Fiber Plants" at OFC/NFOEC 2005. He also has taked part of the panel discussion in the workshop "PMD-Induced Service Outages", at the same event.

An article by FiberWork discussing the investment losses due to PMD impairments has just been published by the LightWave magazine (February 2005 issue). The article is also available online at Lightwave's Website or PDF simple text version or PDF version of the magazine.