Nexans to manufacture plastic optical fibre

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By Matthew Peach, Lyon

French cable manufacturer Nexans, the former cable division of Alcatel, plans to start commercial production of plastic optical fibre (POF) in 2003.

Speaking at his new research centre in Lyon, manager Gilles Widawski told Lightwave Europe, "Our intention is to become a fibre manufacturer. Nexans is currently a cable maker but there's a risk that we could lose our position if we do not become a fibre maker too. We will digest the telecoms industry crash, invest again, and develop our own POF."

Currently the only manufacturers of stepped-index and graded-index POF are based in Japan, apart from one small manufacturer in the USA.

Nexans is looking to produce a range of POFs, but with higher temperature resistance (up to 150°C) than conventional POF (which degrades above 80°C).

"We will try to compete with established Japanese Cytop technology, based on a fluorinated, amorphous polymer."

The company plans to develop GI-POF with an external diameter of 500-1000µm and attenuation below 130dB. Compared to silica, the main problem with manufacturing POF is contamination. However, this can be overcome with gas treatment. Nexans last month completed four Class 1000 cleanrooms in Lyon, where it will develop and produce its fibre.

There are likely to be two types of polymer fibre produced.

Step index (SI-POF), with its higher attenuation of 130dB/km, is intended for 650nm trans-mission, short links up to 200m and rates of up to 200Mbit/s.

The second type will be graded index (GI-POF), based on Cytop, with low attenuation of 30dB/km, carrying signals at 650, 850 and 1300nm. This would be for repeaterless links up to 1km at rates of 1-10Gbit/s. The Cytop

GI-POF fibre offers an attenuation of 30dB/km compared with conventional PMMA POF, which has an attenuation up to 150dB/km.

"In theory, Cytop GI-POF could end up performing as well as mono-mode silica fibre," said Widawski.

There are several practical advantages of POF. Its large core diameter - up to 1000µm - makes it easier to connect. The larger core size also allows mode-mixing, which in turn allows higher bandwidth than possible in silica. There is no need to polish the fibre nor to coat it, as silica requires. Splicing and attaching devices is therefore simplified. Another advantage is that it can be cut with a pair of scissors. A polymer fibre can undergo micro-bending without loss or aging damage that silica tends to suffer.

The traditional drawback has been POF's poor resistance to temperatures above 80°C. While this is not an issue in LAN applications, it can pose problems in vehicle communication applications, one of POF's key deployment areas.

Widawski continued, "Plastic optical fibre could suit the LAN but probably not long-haul applications because of its high attenuation [silica fibre has attenuation of only 1dB/km].

"But, considering the development of hollow fibre, that kind of technology could mean that polymer fibre could possibly be suitable for longer hauls.

"Opportunities for POF lie in residential home access, which is currently at least 90% copper in Europe. So, at the upgrade point there is an opportunity for us; copper could be replaced by POF."

Prototyping will start in early 2003 and commercial production later in the year. The research centre will also perform tests on POF profiles, fire resistance, and the effects of aging and climate.

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