Feasibility of 800G LR4 and 800G ER8 with PAM4 IMDD

1

Feasibility of 800G LR4 and 800G ER8 with PAM4 IMDD

Rang-Chen (Ryan) Yu, SiFotonicsFrank Chang, Source Photonics

IEEE 802.3 B400G Study Group, August 19, 2021

2 R. Yu and F. Chang, Feasibility of 800G LR4 and ER8 with PAM4 IMDD, IEEE 802.3 B400G Study Group, August 19, 2021

Supporters• Andy Bechtolsheim, Arista• Ed Ulrichs, Intel• Ali Ghiasi, Ghiasi Quantum• Drew Guckenberger, Maxlinear• Marika Herod, Credo• Han Li, China Mobile• Junjie Li, China Telecom• Jeff Maki, Juniper• Vasudevan Parthasarathy, Broadcom• Shikui Shen, China Unicom• Charles Su, Huawei • Zhan Su, ZTE• Philip Sun, Credo • Xi Wang, Marvell• Xue Wang, H3C• Helen Xu, Huawei• Kevin Zhang, Renesas


800G LR Objective and This Contribution Focus• 800G LR objective adopted by IEEE B400G Study Group• Many options under considerations

• T. Zhang, et al, “Considerations on the "10km @ 800Gb/s" objective”, July 19, 2021, IEEE B400G SG

• C. Lam, et al, “Coherent-Lite for beyond 400GbE”, July 21, 2021, IEEE B400G SG• T. Zhang et al, “Technical Feasibility of 800K 10km Objective”, August 10, 2021, IEEE B400G SG

• This contribution focus on 800G LR4, with 4x200G PAM4 as main technical option• Channel plan with reasonable dispersion level tolerance• Target to take advantage of DSP developed for 800G DR4/FR4• Leverage of work done within the industry for 100Gb/s extended reach optical specs

• Proper scaling of dispersion tolerance with proper wavelength channel plan • Potential cost advantage vs. alternatives

https://www.ieee802.org/3/B400G/public/21_07/lam_b400g_01a_210720.pdf

https://www.ieee802.org/3/B400G/public/21_08/zhang_b400g_01_0812.pdf


Tech. Feasibility: CD Tolerance Range for 200G PAM4

DP < 2.7dB

• Choose MLSE, EQ> 5Tap as DSP option baseline

• CD_min. ~ -21.5 ps/nm• CD_max ~ +11 ps/nm


Tech. Feasibility: CD Tolerance Relate to Wavelengths• #1 tech. Concern is dispersion tolerance• Dispersion range defined by ITU spec. for 10km, for different wavelength l

• CD_Min= 0.2325*l*(1-(1300/l)^4)• CD_max=0.2325*l*(1-(1324/l)^4)

CD_max ~ +11 ps/nm

-30.0

-25.0

-20.0

-15.0

-10.0

-5.0

0.0

5.0

10.0

15.0

1295 1297 1299 1301 1303 1305 1307 1309 1311

CD_maxCD_min

Disp

ersio

n (p

s/nm

)

Wavelength (nm)

CD_min. ~ -21.5 ps/nm


Tech. Feasibility: LR4 Channel Wavelengths Choice

CD_max ~ +11 ps/nm

-30.0

-25.0

-20.0

-15.0

-10.0

-5.0

0.0

5.0

10.0

15.0

1295 1297 1299 1301 1303 1305 1307 1309 1311

CD_maxCD_min

Disp

ersio

n (p

s/nm

)

Wavelength (nm)

CD_min. ~ -19ps/nm

• Propose to adopt wavelengths with 400GHz Channel SpacingChannel # Min. Typical Max. Unit

l0 1304.06 1304.58 1305.1 nm

l1 1306.33 1306.85 1307.38 nm

l2 1308.61 1309.14 1309.66 nm

l3 1310.9 1311.43 1311.96 nm


800G LR4 Channel Plan vs. LWDM, CWDM

-60.0

-50.0

-40.0

-30.0

-20.0

-10.0

0.0

10.0

20.0

30.0

40.0

1260 1270 1280 1290 1300 1310 1320 1330 1340

CD_max

CD_min

Disp

ersio

n fo

r 10k

m (p

s/nm

)

Proposed 800G LR4 CD:-19 to +11ps/nm

LWDMCD: -28.4 to +9.4ps/nm CWDM4

CD:-58.8 to +33ps/nm

800G LR4

LAN WDM


DSP Requirement for 800G LR4 vs. LWDM, CWDM

Channel Plan(nm)

Max. Dispersion(Ps/nm)

Min. Dispersion DSP Requirement

800G LR4 Proposal L0=1304.58L1=1306.85L2=1309.14L3=1311.43

+11 -19 MLSE + Modest # of Taps (>5)

LAN WDM L0=1295.56L1=1300.05L2=1304.58L3=1309.14

+9.4 -28.4 MLSE + Large # of Taps (> 21), Feasibility not clear

CWDM L0=1271L1=1291L2=1311L3=1331

+33 -58.8 Out of the question for IMDD


Tech. Feasibility: RX sensitivity @ 224G Initial MZM vs EML Evaluation results Reference

Source: Technical feasibility of 200G/lane optical (ieee802.org)

MZM EML

https://www.ieee802.org/3/B400G/public/21_05/kuschnerov_b400g_01_210503.pdf


Tech. Feasibility: Preliminary Link Budget DiscussionThe published 100G Lambda MSA 400G LR4-10 specification can be informative to develop a baseline proposal for the SG (100G Lambda MSA 400G LR4 Spec. Hyperlink)• Detail spec. will be discussed later, with options to adjust Tx/Rx spec.

Option #2Option #1

0.3 dbm–1.1 dbm+ TDECQ

–6.8 dbm–8.2 dbm+ TDECQ

+1.3 dbm –0.1 dbm+ TDECQ

–5.8 dbm–7.2 dbm+ TDECQ

https://100glambda.com/specifications/send/2-specifications/10-400g-lr4-10-technical-spec-rev1-0


800G LR4 Feasibility Summary• 800G LR4 Technical feasibility Proposed• Channel wavelength plan proposed at • L0=1304.58nm• L1=1306.85nm• L2=1309.14 nm• L3=1311.43nm

• CD tolerance levels• Max. +11ps/nm• Min. -19ps/nm

• Link budget proposal with 2 options: #1 option: Tx/Rx stay the same as 400G LR4-10#2 Option: increase Tx power, with relaxed Rx sensitivity by 1dB


800G ER8 Objective and This Contribution Focus• 800G ER objective adopted by IEEE BY400G WG

• Define a physical layer specification that supports 800 Gb/s operation: • over a single SMF in each direction with lengths up to at least 40 km

• This contribution focus on 800G ER8• Channel plan with reasonable dispersion level tolerance• Target to piggyback DSP silicon developed for 8x100G

• leverage related work done in the industry for 100Gb/s extended reach optical specs Proper scaling of dispersion tolerance with proper wavelength channel plan

• Potential cost advantage vs. alternatives


CD Penalty at 53GBaud for EML Transmitter

• Solid line reference from Yu Xu, et al, “Further Technical Study for 400GE with 4*100G PAM4”, May 23, 2019, IEEE 802.3cu Task Force Interim Meeting

• Dash line extrapolated for positive chirp data on negative dispersion side

• EMLs tend to have positive chirp, incur higher penalty with higher positive dispersion, and much more tolerance for negative dispersion

• With chirp +0.5 as baseline, it is feasible to extend negative dispersion to -85ps/nm, if we set 2.7dB as max. for dispersion penalty

Chirp Factor 1

Chirp Factor +0.7

Chirp Factor +0.5

Chirp Factor +0.2Chirp Factor +0

-85 -80

Extrapolated for negative CD

-70 -50 -20 0 +10 +20 +30 +35+40

1

2

3

4

CD Penalty vs. EML Chirp Factor

DP < 2.7dB

https://www.ieee802.org/3/cu/public/May19/yu_3cu_01a_0519.pdf


Test Data on Silicon Photonics MZM

0

0.5

1

1.5

2

2.5

3

-80 -60 -40 -20 0 20 40 60 80

Sample#1

Sample#2

Dispersion (ps/nm)

Disp

ersio

nPa

nelty

(dB)

Max. TDECQ-TECQ< 2.7dB

Min

.Disp

ersio

n 59

.6ps

/nm

Max

.Disp

ersio

n +3

7.1p

s/nm

R. Yu and D. Pan, OFC’2021, M36A.5, “Silicon Photonics Applications for 5G and Data Centers”


Tech. Feasibility: CD Tolerance for 40km Reach• Dispersion range defined by ITU spec. for different wavelength l, per Km of transmission

• CD_Min= 0.02325*l*(1-(1300/l)4); CD_max=0.02325*l*(1-(1324/l)4)• If we limit CD tolerance to -60 to +37ps/nm, then wavelengths need to be limited to 1308-1309nm,

very tight to fit 8 wavelengths

-100.00-95.00-90.00-85.00-80.00-75.00-70.00-65.00-60.00-55.00-50.00-45.00-40.00-35.00-30.00-25.00-20.00-15.00-10.00-5.000.005.00

10.0015.0020.0025.0030.0035.0040.0045.0050.0055.0060.0065.00

1300.00 1302.00 1304.00 1306.00 1308.00 1310.00 1312.00 1314.00 1316.00

MIN. D-40KM

MAX. D-40KM

+37ps/nm

-60ps/nm


Tech. Feasibility: CD Tolerance for 40km Reach

-100.00-95.00-90.00-85.00-80.00-75.00-70.00-65.00-60.00-55.00-50.00-45.00-40.00-35.00-30.00-25.00-20.00-15.00-10.00-5.000.005.00

10.0015.0020.0025.0030.0035.0040.0045.0050.0055.0060.0065.00

1300.00 1302.00 1304.00 1306.00 1308.00 1310.00 1312.00 1314.00 1316.00

MIN. D-40KM

MAX. D-40KM

+37ps/nm

-85ps/nm

• If we can relax dispersion tolerance to -85 to +37ps/nm, wavelengths can be much wider from 1301.6 to 1310nm.

• Possible to fit 8 channels from 1302.31nm to 1310.28nm, with 200GHz Channel spacing

1310

.28n

m

L0=1302.31nmL1=1303.45nmL2=1304.58nmL3=1305.72nmL4=1306.85nmL5=1308.00nmL6=1309.14nmL7=1310.28nm

1309

.14n

m

1308

.00n

m

1306

.85n

m

1305

.72n

m

1304

.58n

m

1303

.45n

m

1302

.31n

m


Link Budget Discussion

-15

-10

-5

0

5

10

0 0.5 1 1.5 2 2.5 3 3.5 4

Link Budget Baseline Reference

Tx_OMAouter (max)

Tx_OMAouter (min)

Rx Sens_OMAouter (max)

TDECQ or TECQ

OM

Aout

er(d

bm)

4.7dbm3.3+TDECQ

-13.8dbm-15.2+TDECQ or TECQ

18.5

dB

• Tx and Rx spec.:A future baseline proposal would be able to developed leveraging knowledge gained from the published 100G Lambda MSA’s 100G ER1-40 specification(100G Lambda MSA 100G ER1-40 spec. hyper link)

https://100glambda.com/specifications/send/2-specifications/11-100g-lr1-20-er1-30-er1-40-technical-specs-rev-1p1


800G ER8 Feasibility Summary• 800G ER8 Technical feasibility Proposed

• Channel wavelength plan proposed at • L0=1302.31nm• L1=1303.45nm• L2=1304.58nm• L3=1305.72nm• L4=1306.85nm• L5=1308.00nm• L6=1309.14nm• L7=1310.28nm

• CD tolerance levels• Max. +37ps/nm• Min. -85ps/nm

• Tx and Rx link budget proposal with 100G Lambda MSA 100G ER1-40 as a baseline starting point


Thank You!

Feasibility of 800G LR4 and 800G ER8 with PAM4 IMDD

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