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Optical PAM4 Technology for Data Center and Next Gen. Wireless Applications

ECOC 2016Market FocusRang-Chen (Ryan) Yu, Oplink Communications, LLC, a Molex Company



Molex Overview

Molex Optical Solution Group

• Connectivity Solutions

• Optoelectronic Solutions

• Passive Solutions

moving from

connectors to total

electronic solutions



New Age of “Cloud” Computing

3

Any App..

Any Time..

Anywhere..

Anybody..



Behind the “Cloud”..

4



Behind the “Cloud”..

5

Metro Networks

Data Center/

Web Companies

Wireless Networks



Optical Networking Speed Evolution

Data Center:

• Servers NIC: 10G 25/50G

• ToR/SPINE-LEAF:

• 40G 100G Now

• 400G @ 2018-2019

Wireless Front Haul:

• 4G/LTE 10G CPRI Now

• 4G+/5G 25/50/100G

Metro Core

• 10G 100 Coherent DWDM now

• 400G Coherent soon



NRZ OOK Modulation Challenges

• NRZ OOK modulation technology choice since

the dawn of optical communication

• 1st

live phone optical transmission @ 6Mbps

in 1977 by GTE

• Pros:

• Simple: low cost component/IC

• Robust: SNR tolerance

• Cons:

• Inefficient @ symbol rate

• High Baud rate

higher cost components

Much larger impairment over distance,

e.g, from fiber dispersion



PAM4 Solutions

• PAM4: 4-Level Pulse Amplitude Modulation

• NRZ OOK equivalent to PAM2

• Pros:

• 2x Bit rate at same baud rate reduce

component cost

• Reduce fiber impairment effect (e.g., CD)

• Cons:

• Linearity requirements on Tx and Rx

components

• Increased sensitivity to SNR



Critical Factors for PAM4 Success • Broad industry support

• e.g., PAM4 vs. DMT debate

• IEEE standard converging to PAM4 for 400GbE

• DSP Capabilities

• Low Power with advanced CMOS node

• ~1.2-1.5W / 100G with 16 nm CMOS

• Equalization Performance

• Advanced DSP algorithm enabling compensation for

component imperfection and fiber impairments

• Cost advantage

• 56GB-PAM4 vs. LR4/CWDM4/PSM4 4x advantage in # of OE

elements



NRZ OOK to PAM4 Transition Roadmap

25G NRZ OOK

50Gbps

200Gbps

400Gbps

25GB-PAM4 56GB-PAM4

LR4: 4x25G NRZ*

CWDM4: 4x25G NRZ**

PSM4: 4x25G NRZ**

SR4: 4x25G NRZ*

FR4: 4x25GB-PAM4***

DR4: 4x25GB-PAM4***

DR: 1x56GB-PAM4***

• LR: 10 Km

• FR: 2km

• DR: 500m

• SR: 100m

DR4: 4x56GB-PAM4***SR16: 16x25G NRZ* LR8: 8x28GB-PAM4*

FR8: 8x28GB-PAM4*

100Gbps

SR: 1x25GB-PAM4***



Roadmap Towards Terabit

11

10

100

1000

2000 2005 2010 2015 2020

Single-Ch. Quad-Ch. 8-10 Ch.

10G25G

40G50G

100G

400G

200G

PAM4 Enabled



Optoelectronics Options for PAM4

• DML:

•Challenging to scale PAM4 modulation beyond 28GB

• Likely candidates for 56GB+ PAM4:

• InP based EML, or MZL

• Silicon Photonics MZ + InP Laser (SiMZL)

• Si MZL vs. InP EML/MZL

• Modulators BW can support ~30GHz bandwidth

• Less sensitivity over wide wavelength change

• Same modulator over O-band or C-band range

• Much easier/lower cost for Multi-Channel array over wavelength

range (e.g., CWDM)

• No need for cooling

• Less Power Dissipation



Intra Data Center Application Examples

Tx

Rx

112Gbps (56GB-PAM4)

100G “DR”

4x112Gbps (56GB-PAM4)

Tx

Rx

400G DR

Servers

“SPINE”

“LEAF”

ToR

Tx

Rx

56Gbps (28GB-PAM4)

50G “SR”



Inter-Data Center Applications Examples

Tx

Rx

56GB-PAM4

DWDM wavelengths

100G DWDM QSFP28

• Increasing demand for economical

solutions for DCI within Metro

• Majority served < 80km

• Up to 8 Tbps/Fiber between DC

• Coherent solution high power/high cost

• 56GB-PAM4 DWDM

• < 4W/100G

• Cost << Coherent

• Strong DSP (e.g., MLSE like algorithm)

enhance dispersion tolerance and channel

imperfection

• Careful OSNR/Dispersion management

80x100Gbps=8Tbps



Tx

Rx

Metro 100G “ZR” Applications Examples

• “ZR” supporting up to 80Km had been a

metro requirement for 1G and 10G

• Coherent 100G “ZR” high cost

• 3x higher $/Gbps vs. 10G

• 4x14GB-PAM4 enabling direct detection

>80km reach without dispersion

compensation

• $/Gbps << Coherent

• Power dissipation << Coherent

• Can also support DWDM

100G ZR

4x14GB-PAM4



5G Wireless Applications

Source: Huawei

• 5G wireless will start commercial deployment ~2019,

with 4G+ starting now (e.g., Verizon)

• Expanded spectrum with massive MIMO drive for

huge front haul BW

• 64x64 MIMO need up to 2.4T with CPRI

• New eCPRI standard reduce BW requirement by

90%

• Scalable eCPRI C-RAN Front-Haul:

• 14GB-PAM4 DWDM

• Re-use 10G components to reduce cost

• Support 40x25G = 1Tbps total capacity per fiber

pair

• WDM Add/Drop allow flexible high bandwidth

connectivity between BBU and RRU

Tx

Rx

14GB-PAM4 DWDM



Form Factors Supporting PAM4 Solutions

QSFP DD MSA:

• Additional 4 lanes supporting 8x25G NRZ, Allow

32x200G=6.4T for 1RU switch density

• 200G (Optical: 4x28GB-PAM4)

• 2x100G (Optical: 2x56GB-PAM4)

• Support 8x56G PAM4 Electrical Interface, allow

32x400G=12.9T for 1RY switch density

• 400G or 4x100G (Optical: 4x56GB-PAM4)

CFP8 MSA:

• ~ CFP2 Size

• Allows 8x400G ~ 3.2T for 1RU switch density

• First Gen. 400G for Router interface, unlikely to

be deployed in data center in large scale

Consortium for On-Board Optics will start with 400G+



Summary

Optical PAM4 becoming critical building block for next

gen. optical networking powering internet “cloud”

Advanced DSP enabling optical PAM4 for wide range

of applications

— Intra-Data center

— DCI

— Metro

— 5G wireless front haul



Thank You!

Documents

Optical PAM4 Technology for Data Center and Next Gen ... 2016 Market... · Optical PAM4 Technology for Data Center and Next Gen. Wireless Applications ... Huawei • 5G wireless will