Who Makes What: 40- & 100-Gbit/s Systems
Basic 40G transmission systems have been around for a while in ultra-long-haul and long-haul applications, but 40G is now spreading through the core to other parts of the network, particularly for metro ROADMs, as 40G becomes more generally deployed (see Table 1). Market research company Ovum Ltd. has estimated that by late 2008, more than 30 network operators worldwide had spent over $250 million since 2005 in deploying 40G.
And the future looks potentially bright. According to market research company Infonetics Research Inc. , the global market for 40G and 100G optical network equipment should grow at a compound annual growth rate (CAGR) of around 46 percent from 2009 to 2011 to reach US$5.1 billion. Of course, the current economic slowdown is clouding the issue, and Infonetics stresses that, for optical networks generally, much depends on whether service providers do follow through during the second half of 2009 with their indicated spending.
Vendors are naturally responding. An early commercial product exemplifying of the trend to end-to-end 40G is Huawei Technologies Co. Ltd. ’s E2E 40G Internet Protocol (IP) and optical transport solution, announced in February at the MPLS & Ethernet World Congress 2009 in Paris. This supports IP-based ultra-broadband services by combining the company’s NetEngine5000E high-end router and 40G DWDM transport system.
Essentially, the move to 40G now and 100G later (but the sequence is disputed – see Page 4: Sticky Questions) rests on the standard telecom bandwidth-growth story. Bandwidth demands on the core are increasing because of the growth of IP traffic, video, and so on. Video traffic, in particular, has emerged as a major driver for more bandwidth – Cisco has estimated that video will represent half of consumer IP traffic by 2012 (and total IP traffic will be six times greater then than in 2007) – and 40G is seen by its adherents as a key way of handling router interconnection in this environment by aggregating multiple existing 10G links onto a smaller number of 40G ones. Another very important driver is fiber exhaust, both on metro and long-haul routes, which makes it important to squeeze more traffic onto existing fiber.
Although it is possible to stack multiple 10G streams onto fiber to achieve a 4x10G equivalent to 40G capacity, for example, 40G supports point out that this is not efficient in terms of router port usage – a 4x10G interface on a router port is less efficient than a single 40G one. Although such a single 40G interface is more expensive than a single 10G one, the cost factor (which has improved considerably over the last couple of years or so) is likely to approach about 2.5 times that of a single 10G interface.
So the industry is hoping that 40/100G will score twice with operators: It will cope with the traffic/bandwidth explosion and will save money by both reducing port counts (and associated operational expenditures) and extending the life of existing fiber assets.
100G is still under development, but first standards are scheduled to appear end-2009 and during 2010 (see below). There have been various demonstrations and trials, and research initiatives established, as Table 2 indicates.
Table 2: Recent 100G Demonstrations, Trials & Initiatives
|AT&T1, NEC Corporation of America and Corning Inc.||USA/May 2008||Transmission of data at 114G over each of 320 separate optical channels on a single 580km optically amplified link|
|Banverket||Sweden/April 2009||Live field trial, running 10G/40G/100G simultaneously on existing fiber network between Sundsvall and Stockholm|
|Deutsche Telekom and Ericsson||Germany/March 2009||100G R&D field trial on existing optical platform as part of European 100Gbit/s Carrier-Grade Ethernet Transport Technologies Project|
|Ciena||USA/August 2008||Demonstration of single wavelength transmission of a 100G data stream, through 80 km of fiber with Caltech|
|Georgia Institute of Technology||USA/March 2009||Establishes the Georgia Tech 100G Optical Networking Consortium with 10 companies to perform multidisciplinary research in all aspects of 100G transmission|
|Global Access and Infinera||Japan/January 2009||Complete Japan's first 100G Ethernet demonstration between Tokyo and Osaka|
|Neos Networks||UK/March 2009||Trial of 100G DWDM optical system between Manchester and London|
|Verizon||USA/September 2008||Moves 100G trials program to next stage with over 1000km runout on Richardson, Texas, network|
|Source: Light Reading, 2009|
Particularly in the context of a 100G optical transmission system, it’s important to be clear on the difference between the external (client) interface and the system’s internal (line) interface. Although a system may present a 100G client interface, the fiber line transmission could be handled by, say, 10 optical wavelengths of 10G each (10x10G format), or by multiple 40G optical wavelengths. The goal, however, is to match both the client and line rates, so that a single 100G optical signal goes onto a single DWDM wavelength – which is why Ciena trumpeted its Caltech demonstration in Table 2, as it said that this was the first true, single-wavelength transmission of a 100G data stream through 80 km of fiber.
From the point of view of more traditional telecom protocols, 40G has been standardized for some time – it’s 40G Synchronous Optical Network (Sonet)/SDH OC-768/STM-256, which can be transported in turn by the International Telecommunication Union, Standardization Sector (ITU-T) ’s G.709 digital-wrapper technology (Optical Transport Network – OTN) 43-Gbit/s OTU3s. Work has been under way for a couple of years or so on the next level up for OTN, which is very logically OTU4 and, equally logically, is intended to be available to transport 100G Ethernet. The ITU’s Study Group 15 recently (April 2009) approved an amendment to the 2003 second version of Recommendation G.709/Y.1331 that "specifies 100Gbit/s ODU4/OTU4, support of gigabit Ethernet services via ODU0, ODU2e, ODU3 and ODU4, multi-lane OTU3 and OTU4 and the Lower Order and Higher Order ODU concept to align with the 'one-stage multiplexing' specification described in clause 9.2 of Recommendation G.872." Which presumably means in standards-speak that all technical bases are covered.
Ethernet, and especially 100G Ethernet, is the real focus of interest because of its relentless rise as a universal Layer 2 network technology to underpin IP. Since December 2007, the Institute of Electrical and Electronics Engineers Inc. (IEEE) ’s P802.3ba Task Force has been working to define both 40 and 100G Ethernet standards, with a target date of 2010 for completion. Because Ethernet is now used over a range of scales, from meters to tens of kilometers, the eventual standards will embrace different Physical Layers, those most relevant to telecom network application being:
- 10km range on singlemode fiber – both 40 and 100G
- 40km range on singlemode fiber – 100G only
In summary, 802.3ba aims to:
- Support full-duplex operation only
- Preserve the 802.3/Ethernet frame format utilizing the 802.3 MAC
- Preserve the minimum and maximum frame sizes of the current 802.3 standard
- Support a BER better than or equal to 10E-12 at the MAC/PLS service interface
- Provide appropriate support for OTN
- Support MAC data rates of 40 and 100 Gbit/s
Overall, this activity means that the 40/100G client interface is Ethernet, and the WAN interface is either OTU3/OTU4 or Ethernet for shorter spans.
As always, interoperability issues, gap filling, and other matters will loom large in the commercialization of 40/100G Ethernet, and various industry initiatives have already sprung up. For example, the short-lived Road to 100G Alliance (later merged with the Ethernet Alliance) formed a technical committee in June 2008 “to identify gaps in technology and standards that could impact the rollout of 100G OTN and Ethernet networking platforms,” as the Alliance states.
Multi-source agreements (MSAs) have long been a feature of the telecom equipment industry, as they commit groups of suppliers to supporting certain standardized module or device form factors, interfaces, and characteristics – and 40/100G is no exception. In March 2009, for example, Finisar, Opnext, and Sumitomo Electric Industries Ltd. / ExceLight Communications Inc. formed the CFP MSA, whose aim is to define a hot-pluggable optical transceiver form factor to enable 40 and 100G applications, including 40GbE, 100GbE, OC-768/STM-256, and OTU3 protocols, multimode and singlemode fiber optics, and various link distances.
The earlier XLMD-MSA, formed by Eudyna Devices Inc. , Mitsubishi Electric Corp. (Tokyo: 6503), NEC Electronics Corp. , Oki Electric Industry Co. Ltd. , Opnext Inc. (Nasdaq: OPXT), and Sumitomo Electric Industries in 2007, had the more limited aims of establishing compatible sources of 40G optical transmitter and receiver devices embedded into 40G optical transceiver modules.
In between, in May 2008, the Optical Internetworking Forum (OIF) , concerned that device and module vendors in particular were beginning to scramble in different, incompatible directions over 100G, formed a consensus to use DP-QPSK modulation with a coherent receiver in 100G long-distance DWDM transmission, and later launched two more initiatives to look at photonic integration and the use of Forward Error Correction (FEC) in such systems.
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