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WDM Nice: Rough Travel Guide to 100G
By Mark Lum, independent telecoms consultant
So here we are at the must-attend 100G showcase, with no fewer than seven vendors jostling for position on the stage in front of a baying crowd*. The only qualification? To have a published field trial with an operator. However, one does not… I leave as an exercise for the alert reader to discover which!
I’ll try to encapsulate each trial/vendor in a few highlights, which will doubtless cause trouble for omitting some important aspect — there’s no substitute for being here! As the 100G alphabet soup is cooked, I suspect the session will run late.
Alcatel-Lucent: First 100G trial with Verizon 16/11/07. 500 km Tampa-Miami. DQPSK-NRZ/RZ modulation also with 10G channels. Has published 13 R&D papers since 2005. Conclusion: 100G PDM-QPSK (25 Gbaud) with coherent detection and digital post-processing, also compatible with 10G NRZ and 40G.
Ciena: 100G trial with Caltech over 1500 km. Agrees with Alcatel-Lucent on system technology: ADC plus DSP ASICs also photonic integration. 30-50% p.a. traffic growth means capacity exhaust, even 40G will be insufficient in 2012. There will be much secret sauce from different vendors.
Cisco: 1st 100 GbE 802.3ba-based router demo with Comcast (6/08). Key requirement is compatibility with 10G links @ 50 GHz. Conclusion: PM-QPSK modulation (25 Gbaud). Sees 100G in routers for IPoWDM architectures, but also transponders. Vision shows 200G, 400G, 1T, CO-OFDM, software-defined optics.
Ericsson: 112Gbit/s trial with Deutsche Telekom over 633 km including four ROADMs. PM-RZ-DQPSK modulation with fast LiNbO3 polarization tracking plus 10G and 40G neighbouring channels. Conclusion: PM RZ-DQPSK @ 50GHz needing no ADCs or DSP since polarization tracker is used for PMD tolerance. Investigating OFDM, SCM, nQAM.
Huawei: Several options available. OPFDM-DQPSK or OPDM-DQPSK — no ADC/DSP is needed so cost-effective. ePDM-DQPSK provides best performance, >1,000km but is more complex. Market timing is critical, as is ASIC complexity and availability. Sees a five-year delay between 40G and 100G deployments.
Nokia Siemens: 107 Gbit/s trial with AT&T in 2006, 2x 80km direct optical. First CP-QPSK in 2007. 111 Gbit/s trial with Verizon in 2008, 1040 km and mixed 100G, 10G and 40G channels. Believes that coherent CP-DQPSK is the way forward, hero experiments are now finished, and need to make real commercial products.
Nortel: 100G trial with Comcast (3/08), 335km link including ROADM. Many network demos 2008-09, including Verizon 73 km link that could not carry standard 10G. Conclusion: coherent FDM-DP-QPSK (14Gbaud) @ 50GHz. Vision that coherent plus WDM gives next big jump in fibre capacity.
I have the feeling of an industry — at least most of the vendor side — in a hurry, pushed by an invidious mix of public demand from a few high-profile carriers, the prospect of competitive IEEE interfaces, intense vendor competition plus a driving technological rivalry to scale the 100G mountain.
I remain most concerned about gaining sufficient economy of scale, but despite appearances, the industry is largely converged on DP-QPSK with coherent detection. And whilst vendors may be reluctant to highlight it, the OIF’s MSA functional standardisation is a critical first step towards economy.
The showcase session has indeed run late and we are now behind schedule: let’s see how 100G deployments in production networks fare in the coming years.
[* I mean: an enthusiastic and receptive audience]
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