Waveguide Optics

Teacher : Lilin YiEmail : lilinyi@sjtu.edu.cnOffice : SEIEE buildings 5-517Tel ：34204596

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State Key Lab of Advanced Optical Communication System and Networks

Chapter 11 Beyond 100G

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Outline

Technical trends beyond 100GLower power consumption for 100G transponderTechnical Options for 400G or 1TSystem vendors viewCarriers viewBusiness view

Technical Trend beyond 100G

DSP = doesn’t save powerHow to reduce the power consumptionBeyond 100G options400G or 1T?higher bit rate per channelFlexible grid - WSSBroadband amplifiers – Raman and hybrid Raman/EDFA

Outline

Technical trends beyond 100GLower power consumption for 100G transponderTechnical Options for 400G or 1TSystem vendors viewCarriers viewBusiness view

Example ADC/DAC/DSP applications

What is driving ADC/DAC/DSP choices

Single chip CMOS ADC/DAC/DSP

Power consumption for ADC/DAC

ADC power consumption ~1.5W/ch in 40nm~6W for Rx DAC power consumption ~0.75W/ch in 40nm~3W for Tx

Power consumption for DSP

4k bits at ADC/DAC, >90% power dissipation is in interconnectInitial power estimates are “always” too lowEven experienced digital designers underestimate “power creep”Once a team has done 100G, then you can believe the power numbers…

Thermal performance

A “gold-plated” package solution

Example 100G chip and HiTCE LTCC substrate

Future challenges - technical

Future challenges - commercial

Outline

Technical trends beyond 100GLower power consumption for 100G transponderTechnical Options for 400G or 1TSystem vendors viewCarriers viewBusiness view

Modulation formats background

Modulation formats background

Outline

Technical trends beyond 100GLower power consumption for 100G transponderTechnical Options for 400G or 1TSystem vendors viewCarriers viewBusiness view

System vendor view - NSN

Transponder architectures beyond 100G Transmitter and receiver remains little changed (PDM-QPSK PDM-16QAM)Optical components spec is more stringent for QAM modulation, requiring ADC with higher number of effective bits, laser with smaller linewidth, more advanced DSP algorithmMajor challenge is the line system itself

System vendor view - NSNOSNR penaltyQPSK 16 QAM, 3.7dB ↑100G PDM-QPSK 200G PDM-16QAM, 6.7↑14dB @ 1E-3 BER vs. 20.7dB @ 1E-3 BER Non-ideal transmitter architecture, 24-26dB @ 1E-3 BER for 200G PDM-16QAM

Nonlinear threshold penaltyThe highest maximum power of a constellation point increase relative to the average power of the signal100G PDM-QPSK 200G PDM-16QAM, at least 5dB power penalty

Maximal reach100G PDM-QPSK 400G PDM-256QAM, 3% reachIt is impossible to transmit 400G line rates within a 50-GHz WDM grid as the maximal reach is only several hundreds of kms for even the most optimum system400G and 1T is more than a change of the modulation format

System vendor view - NSNCurrent fixed-grid networks

• PDM-QPSK, 4b/s/Hz in theory vs. 2b/s/Hz in reality (50GHz grid) • After 20 cascaded WSS with 4th order Gaussian 3-dB bandwidth of

45GHz, the bandwidth becomes 31GHz, corresponding to 31Gbaud/s signal. Only 62% (31/50) of the actual bandwidth is used with the current WSS technology.

System vendor view - NSNSuper channels: multiple signals or spectral bands are transmitted as a single entity, enabled by flexible WSS technology – a software defined definition of the filter passband. (flexi-grid networks)

• 400G – combine four bands of 100G PDM-QPSK, cosine pulse shaping “square” optical spectrum, 400G line rate 132GHz bandwidth 150GHz flexi-grid channel spacing 88% effective bandwidth (2.67b/s/Hz)

• 400G – combine of two bands of 200G PDM-16QAM 66G bandwidth 87.5GHz flexi-grid channel spacing 76% effective bandwidth

• 1T – combine 5 bands of 200G PDM-16QAM 165G bandwidth 187.5G flexi-grid channel spacing maximal capacity of 25Tb/s in C band

To use 90% of the actual bandwidth, a 225GHz channel spacing is required with the current WSS technology (solid line, 4th

order, 45GHz ) . For next-generation high-definition WSS (dotted line, 6th order, 47GHz), the channel spacing is reduced to 150GHz.

System vendor view - NSN

Fiber infrastructure optimizationNew fiber with low span loss and low nonlinearity – large effective area pure-silica-core fiber (LA-PSCF) 0.16dB/km, 130um2

It remains to be seen if the increase in fiber capacity outweighs the immense deployment cost of new fiber infrastructureHybrid EDFA/Raman amplification – improve OSNR

System vendor view - Ciena

Current situations100G performance is now similar to 10G, only after applying DP-QPSK modulation coupled with a coherent receiver and advanced FEC.

ProblemsFEC is approaching the Shannon limitMore complex modulation formats, such as 16 QAM, have a higher sensitivity to noise, requiring more frequent regenerationChannel power cannot be increased significantly due to nonlinearities.

SolutionsFlexible grid ROADM – arbitrary configuration is difficultMaximize the symbol rate based on the current coherent detection technologySoftware configurable modulation formats Supper-channelNew fibers, new amplifier technologies and different amplifier spacing

Outline

Technical trends beyond 100GLower power consumption for 100G transponderTechnical Options for 400G or 1TSystem vendors viewCarriers viewBusiness view

Carrier view – Verizon100G live deployment Paris to Frankfurt 893km13 spansno regenerationOperational Dec. 2009Add 100Gb/s router in 2010

Carrier view – VerizonThirst for more

Carrier view – VerizonBandwidth scalability

Carrier view – VerizonFlexible Bandwidth Grid

Carrier view – VerizonFlexible Layer1 Network

Carrier view – VerizonWhat’s Next?

Carrier view – Verizon

Carrier view – AT&T

Coming soon in fiber transmission An integrated photonic module and a MSA transceiver module for 100G PDM QPSK

Coming soon in photonic networkManual reconfigurable RODAM Software configurable CDC ROADM + tunable transponder

Carrier view – AT&T

Beyond soon in fiber transmissionWhat will follow the 100G, coherent systems?CD with DSP is powerful, but new for fiber community and its evolution is unclearThe current system is approaching its capacity limit, modification is required to mitigate fiber nonlinearitySingle carrier multi carrier, although “flexible grid” improve the spectral efficiency, come at a painful price in terms of operational complexity

Beyond soon in photonic networkFully configurable ROADM will be a big improvement, but connecting “clients” to the transponders is still a manual processSimplify and speed up installation and turn-up of connections by inserting a “client-side” cross-connect

Carrier view – AT&T

ConclusionsCarrier today must: 1. Learn how to handle transmission systems with coherent detection and DSP; 2. Develop new processes to take advantage of colorless and non-directional ROADMs to enable efficient and agile photonic networks.In a few more years, 400G at the expense of shorter reach, the need for Raman amplification and/or new fiber installations. It is quite possible the per bit cost will not be less than the previous generation. Feasibility? Will come down to the overall network economics.

Outline

Technical trends beyond 100GLower power consumption for 100G transponderTechnical Options for 400G or 1TSystem vendors viewCarriers viewBusiness view