FEATURE 100G NETWORKS
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Optical vendors juggle terabit trade-offs
While the 100G market is now established, Pauline Rigby finds that it’s not yet clear what the next step will be
I
ndustry observers have described 2013 as ‘the year of 100G’. According to Infonetics Research, spending on wavelength-division multiplexed (WDM) equipment accelerated dramatically as
a result of new 100G deployments. In fact, the market-research firm says that worldwide spending on 100G equipment is close to 15 per cent of all optical hardware spending, which itself totalled $3.3 billion (€2.4 billion) in the second quarter of this year. Some kind of celebration seems justified,
because the 100G market took a long time to reach maturity. Ciena, through its purchase of Nortel Networks’ optical division, has been selling 100G coherent optical systems since 2009. And, as the
company recounts on its website, the preparatory work began a decade earlier, when engineers realised just how hard they would have to push the optics to achieve serial 100-Gbps transmission. As the symbol rate on the optical fibre
increases, non-linear effects such as chromatic dispersion and polarisation-mode dispersion (PMD) increase as the square of the symbol rate. Unsurprisingly, this increase in noise reduces the reach of the optical signal dramatically. In 1999, Nortel engineers had managed to achieve 80-Gbps serial optical transmission under laboratory conditions, but realised that their approach would only work in the real world if carriers put more signal regenerators into their
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FIBRE SYSTEMS Issue 1 • Autumn 2013
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