Datarate Adaptation for Night-Time Energy Savings in Core Networks

Irfan Ullah Department of Information and Communication Engineering Myongji university, Yongin, South Korea

Published in Journal of LightWave Technology, vol. 31, no. 5, 2013 Copyright © solarlits.com

Contents

1. Objective2. Elastic transceiver3. Format adaptation4. Symbol rate adaptation5. Results6. Conclusions

• Datarate adaptive transceivers can be used to follow the variations in requested bandwidth in core networks.

• Energy savings • Datarate adaptive transceivers > Static networks (peak traffic all the times)

• Schemes for datarate adaptation in optical transceivers1. Modulation-format adaptation

2. Symbol-rate adaptation

• Tested for • European backbone network (energy saving up to 30%)

Objective

• 100-Gb/s PDM-QPSK transmitter1. Transceiver receives a client data and payload is integrated

2. Each MZM modulates different BPSK signal

3. I1, Q1, I2 and Q2 are then amplified

4. BPSK signals are then multiplexed in phase and Polarized through phase shifters and polarization beam combiners (PBC)

5. Finally, 28-Gbaud PDM-QPSK

Elastic Transceivers

Polarization beam combiners (PBC)

Forward error correction (FEC)

Mach–Zehnder modulators (MZM)

Polarization-division-multiplexed quaternary phase-shift keying (PDM-QPSK)

Gray blocks indicate the reconfigurable modules that offer format flexibity

• Receiver1. Polarization-diverse 90 hybrid

2. Linear digital representation sampled in phase and quadrature of two arbitrary but orthogonal polarizations

3. DSP includes compensation of the cumulated chromatic dispersion

4. Equalizer then compensates inter-symbol interference (ISI), which separates the two polarizations

5. Remove the frequency and phase offset between the received signal carrier and the local oscillator.

6. decision stage attributes a value to each received symbol

Elastic Transceivers

Gray blocks indicate the reconfigurable modules that offer format flexibity

• Optical reach of 100-Gb/s PDM-QPSK signals is approximately 1200 km

• No dispersion compensation

Elastic Transceivers

• Polarization binary phase shift keying (SP-BPSK): 25-Gb/s payload

• PDM-BPSK: 50-Gb/s

• PS-QPSK: 75-Gb/s

• PDM-QPSK: 100-Gb/s

Modulation format adaptation

Format-adaptation allowed by precoding in a 100-gb/s pdm-qpsk emitter

• 100-km SSMF spans

• EDFA amplification with 6-dB noise

• At optimized channel power• 3600 Km -> 25 Gb/s

• 2500 Km -> 50 Gb/s

• 1800 Km -> 75 Gb/s

• 1200 Km -> 100 Gb/s

Modulation format adaptation

Reach of optical signals versus channel input power for the different modulation formats available to a format-tunable transponder.

Symbol rate adaptation

PDM-QPSK

Reach of optical signals versus channel input power for symbol-rates allowing the transmission of PDM-QPSK with 25-, 50-, 75-, and 100-Gb/s payloads.

List of possible configurations for a format and symbol-rate adaptive transponder for 25-, 50-, 75-, and 100-gb/stransmission

• Format-adaptation allows efficient tradeoffs between line-rate and optical reach

• Switch off unnecessary optoelectronic regenerators at off-peak hours can save 700 W every time.

• Symbol-rate adaptation does not allow to completely switch off interfaces at any time

• allows one to modulate the power consumption of all transponders and regenerators

• Format change does impacts the reach

• Symbol-rate change impacts the power consumption

Mixed format and symbol rate adaptation

FormatSP-BPSKPDM-BPSKPS-QPSKPDM-QPSK

Symbol rate25 Gb/s50 Gb/s75 Gb/s100 Gb/s

Network Scenario

• Orange international backbone network

• 32 nodes and 42 Links

• physical links (dashed lines)

• 10 to 930 km with a mean of 280 km

• The traffic (solid lines) aggregated into 20 demands

• Peak traffic 7, 10, and 15 Tb/s

Results

• Format-adaptation saves 14.5% at 7-Tb/s traffic load to 21.5% at 15 Tb/s

• Symbol-rate adaptation provides an energy saving of 24.7%

Conclusions

• Two schemes for power saving• Format adaptation• Symbol rate adaptation

• Format-adaptation requires a high power consumption at the transponder level• bypass unnecessary optoelectronic regeneration at off-peak hours yields 21% energy

savings

• Symbol-rate adaptation allows a very efficient modulation of the energy consumption of a transponder• This yields 24.7% energy saving

• Combining both techniques can save 30% energy

Thanks ?