JOHN WILLIAMSON WDM
RIDING THE WAVE
Wavelength Division Multiplexing (WDM) has become both a mainstay and a fast-growing element of high capacity optical networking. According to Zion Market Research, the global WDM market was valued at around US$14.10 billion in 2017 and was expected to reach approximately US$28.43 billion in 2023, growing at a CAGR of slightly above 12.4% between 2018 and 2023. John Williamson looks at the issues.
G etting more bandwidth out of existing fibre with Coarse WDM (CWDM) and Dense WDM (DWDM) has obvious attractions. At the same time, the growth of dark fibre availability – a market opportunity forecast by Credence Research to be worth US$11.57 billion by 2026 – adds an additional dimension to the WDM proposition. “WDM and dark fibre definitely go hand- in-hand,” judges Anthony Clarkson, EMEA service provider sales manager at optical transceiver specialist ProLabs. Historically, some of the well- documented differences between CWDM and DWDM have been capacity, range and cost. Depending on fibre type and the distance involved (up to 120 km) CWDM is standardised to theoretically support up to 18 wavelengths per fibre pair, although many commercial systems support just 8. Traditionally CWDM has been the lower cost undertaking. DWDM with amplification can operate over 1,000 km (and above), and support up to 96 wavelengths (and above). An emerging DWDM variant is 400G ZR. As noted by Ferris Lipscomb, VP marketing, at photonic integrated circuit module specialist NeoPhotonics, 400G
capacities. “I think CWDM still has quite a good future,” he contends. “We’ve already seen the start of some
ZR is essentially a purpose-built, cost- sensitive, point-to-point specification for a DWDM link with a reach of 80 km and targeted at the DataCentre Interconnect (DCI) market. “400ZR is mainly intended to be implemented within the size and, mostly, the power envelop of emerging 400G client-side form factors such as OSFP and QSFP-DD to reduce the cost and increase density relative to current pizza box solutions,” comments Lipscomb. “This places restrictions on the optical components and, in addition, requires an interoperable 7nm DSP as a key enabling device in a 400ZR module.” ON COARSE There are various views about what the future holds for CWDM. Koby Reshef, CEO of DWDM and optical fibre networking solutions provider PacketLight Networks Ltd, doesn’t see very bright prospects. “The cost of 10G CWDM today is higher than DWDM. It can be used in different low-cost client interfaces for 100/200/400G solutions but not for the line side,” he states. “100G/200G/400G line side tunability requires at least 48 wavelengths with amplifiers, making CWDM a bad fit.” Clarkson has a different take, particularly as regards boosting CWDM’s
KOBY RESHEF CEO PACKETLIGHT NETWORKS
sub-channel CWDM technologies. And about two years ago we launched a bi- directional CWDM system that allowed you to do CWDM over a single fibre or to get transmit and receive over a single wavelength.” Clarkson also references conversations with technology partners in which the possibility of carrying up to 16 CWDM sub-channels on a single wavelength has been broached. Added to this, he reckons there’s growing pressure on the consumption of WDM frequencies used by new generation PONs in access networks. “So, you could end up here looking at some of the CWDM bands, maybe in the 1430 to 1450 range,” he ventures. It’s worth
noting here, though, that different types and tiers
JAY GILL DIRECTOR OF MARKETING, INFINERA
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| ISSUE 16 | Q1 2019
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