Beyond 10 Gb E Looking Ahead Qwest Communications

Beyond 10 Gb. E – Looking Ahead Qwest Communications International Mark Stine, CTO Government Services Division February 2005 Qwest Proprietary and Confidential © 2004 Qwest Communications International Inc.

Some of the Panel’s Questions What problem are we trying to solve ? How does price/technology/demand determine next step beyond 10 Gbps ? Where are we now ? 40 Gbps/ OC-768 or 100 Gbps ? Qwest Proprietary and Confidential © 2004 Qwest Communications International Inc. 1

What problem are we trying to solve? For Qwest any new technology must result in: Revenue improvement • • Enable new services Product line consolidation Increase market coverage; provide services faster Manage disruption of legacy revenue • • • Increase utilization Reduce ports; minimize metallic interfaces Increase power efficiency and equipment density Minimize revisits to equipment Remote operation • • Convergence, integration of networks Ease provisioning, network configuration changes Improve inventory management Reduce engineering and planning complexity Cost reduction Operations simplification Business goals driven by – demand, capital, competition, relationships Qwest Proprietary and Confidential © 2004 Qwest Communications International Inc. 2

Qwest Multi-service, Packet Centric Infrastructure Service Data & Control MPLS/IP Domain (switching, aggregation, & Layer 2/3 service intelligence) AS SCP SBC Last Residential Mile Control/Applications Domain (distributed intelligence & IP enabled service creation) MPLS/IP Core Physical Domain (next gen optical) Multi-service Delivery Edge NG-ADM , sub- Edge Broadband Access Pipes • Optical, Packet, Wireless Optical Connectivity DW DM Last Business Mile NG-ADM DW DM Other Carriers OC-n, Ethernet Edge Next Generation OSS Qwest Proprietary and Confidential © 2004 Qwest Communications International Inc. 3

How does 40 Gbps and 100 Gbps help? More efficient aggregation of traffic • • Today’s large metro, West coast and East coast routes have sufficient demand to support higher TDM rates beyond 10 Gbps Traditionally higher TDM rate easier to manage than DWDM Minimizes or eliminates WDM channels • Could be fairly significant in the metro environment as cost avoidance to deploying a metro DWDM system Reduces the number of customer interfaces to manage Cheaper – 40 Gbps getting closer • Higher TDM rate interface cards typically prove in at 2. 5 times the cost for 4. 0 times the bandwidth. For example, 10 Gbps proved in at 2. 5 times the cost of 2. 5 Gbps Solves customer application ? ? ? Qwest Proprietary and Confidential © 2004 Qwest Communications International Inc. 4

Where are we today ? Qwest has demonstrated the largest known 10 G/40 G BW * D Field Trial Critical achievements: • ULH DWDM propagation of 85+ 10 Gbps channels at >3000 km with mixed span lengths on Qwest TWC fiber • 3 x 40 Gbps and 88 x 10 Gbps propagated over 1516 km System performance met or exceeded all key advertised features and satisfied Qwest requirements - Very good performance as measured by both pre- and post-FEC BER Key caveats • System was based mostly upon GA or near GA equipment and results are realizable in real world • Configuration is not fully optimal and better performance may be achieved - PMD not known (probably very low – less than. 07 ps/sqrt-km) - CD map optimized for 10 Gbps (but sufficient for 40 Gbps) • The results do not include tolerances for best practice engineering (link margins, end-of-life, etc…) Qwest Proprietary and Confidential 10 Gb/s channel 40 Gb/s channels © 2004 Qwest Communications International Inc. 10 Gb/s channel 5

40 G Trial Configuration: 1516 km • 14 tunable 10 Gbps (50 GHz) transponders • 3 fixed 40 Gbps (100 GHz) transponders • 74 CW lasers Qwest Proprietary and Confidential © 2004 Qwest Communications International Inc. 6

Where are we going? Key Trends in Transport Metro Optical Networking – • • Large scale EXC/MSPP with optical interfaces 160 Gbps-1. 28 Tbps capacity OC-3 c – OC-768(c) VCAT combined with L 2 capabilities • • Carrier grade L 2 devices Options for MPLS or VLAN traffic management/organization Ethernet over dark fiber and over DWDM Fast-E through 10 G LAN PHY • • Expansion of Ethernet in carrier transport space – Ethernet aggregation Agile optical switching (OXCs, ROADMs) Integrated 10 G and 40 G DWDM systems Tunable and integrated optics Optical control plane: GMPLS G. 709 digital wrappers Ultra FEC Raman amplification options Metro Optical Ethernet – Long Haul Optical Transport Qwest Proprietary and Confidential © 2004 Qwest Communications International Inc. 7

Key Disruptive Optical Trends to Watch Optical component consolidation • Price disruption may drive optical architectures around these optical components. Coherent modulation • May help enable 40 and 100 Gbps bit rates with lower symbol rates Debate over opaque (digital) and transparent (analog) architectures • Depends on the network physical topology, demand set, applications, • etc. Some elements of both architectures will be optimal Qwest Proprietary and Confidential © 2004 Qwest Communications International Inc. 8

Optical component consolidation 9 For the last 10 yrs we have been reducing the number of lasers in an optical transport network to reduce cost • Ultra Long Haul transponders/modulators, FEC, Raman • to improve reach and reduce regeneration Transparency to reduce through traffic regeneration What if the costs of lasers and optical components became cheap? Different paradigm. Very disruptive. • Consolidation of multiple discrete optical components onto silicon • Chip yields in full production environment? ? Qwest Proprietary and Confidential © 2004 Qwest Communications International Inc.

Coherent Modulation - Radio Communications 101 Today’s optical transport equipment uses OOK modulation • Some version of NRZ, & CS-RZ formats Future coherent modulation is disruptive in the long haul • QPSK, d. PSK, QAM, etc • Offers up to a theoretical gain of 3 d. B OSNR over OOK • More complex receiver design • Appears to be more tolerant to some nonlinear effects, chromatic dispersion and PMD Qwest Proprietary and Confidential © 2004 Qwest Communications International Inc. 10

Optical Networking Choices Opaque (Digital) network 11 Transparent (Analog) Network Passthru Wavelengths TR SR EXC EXC Opaque (Digital) • Additional grooming points • Simpler design • More optical signal regeneration on passthru wavelengths Transparent (Analog) • Longer reach, More complex modulation and amplification system • Low cost passthru wavelengths • More upfront cost with more all optical components Answer: For Metro and Long Haul Some of both Qwest Proprietary and Confidential © 2004 Qwest Communications International Inc.

40 Gbps - Challenges and Answers Challenges Fiber • PMD on older single mode fiber Costs • Not quite there Answers • The technology is in-place and emerging with GA products • Qwest has demonstrated in the field that 40 Gbps is viable over real fiber over varying span lengths in the metro and long haul network • Good Polarization Mode Dispersion characteristics on True. Wave fiber • Likely sweet spot for metro transport as a cost avoidance to DWDM • Coherent modulation schemes will improve long haul economics Qwest Proprietary and Confidential © 2004 Qwest Communications International Inc. 12

100 Gbps - Challenges and Answers Challenges Fiber • • PMD serious problem on today’s fiber, requires PMD compensators Dispersion managed fiber likely required and active dispersion compensators Component and material limitations • • • Transmitter/Receivers – near electro-optics limits, may require OTDM vs ETDM Lasers – very narrow, high repetition pulse rate with low jitter Processors – processing at line rate challenging (limits FEC, for example) System concerns • Channel spacing fairly wide to avoid FWM • OSNR challenged for current long haul amplifier spacing • Nonlinear effects: SPM, XPM Answers • Not yet clear whether 100 Gbps offers net benefits • 100 Gbps line rate very tough; may need new fiber for long haul transport • Coherent modulation and Inverse Muxing appear most promising Ø Allows 100 Gbps to be transmitted as multiple 10/20 Gbps signals Qwest Proprietary and Confidential © 2004 Qwest Communications International Inc. 13