Klaus Grobe delivered a keynote at today's ITG-Fachtagung Photonische Netze event in Leipzig. Check out the accompany slides he presented

1. 15. ITG-Fachtagung Photonische Netze, Leipzig, May 2014
Dr. Klaus Grobe, ADVA Optical Networking SE, Advanced Technology
Next-Generation Access/Backhaul based on ITU G.989, NG-PON2

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Content
• NG-PON2 Applications
• NG-PON2 Status and Variants
• Conclusion

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NG-PON2 Applications

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NG-PON2 Applications
• Residential access – shared, TWDM
• VDSL2 (FTTCab) / G.fast (FTTdp) backhaul – TWDM or PtP
• Broadband business access (shared or dedicated) – TWDM or PtP
• Mobile backhaul (MBH, D-RAN) – TWDM, PtP
• Fronthaul (MFH, C-RAN) – dedicated, PtP
• Hybrid Fiber/Coax (HFC, 2nd-ary Headend backhaul) – TWDM, PtP

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Application Examples
BBU(H) Base Band Unit (Hotel)
CPRI Common Public Radio Interface
C-RAN Centralized (BBUH), Co-operative (multi-point radio), Clean (systems), and Cloud (infrastructure)
RRH Remote Radio Head
DPU Distribution Point Unit
C-RAN, a.k.a. Fronthaul
BBUH
BBU
BBU RRH
Backhaul
CPRI
RRH
RRH
S1
ONU
Evolved
Packet
Core
WM
OLT
WM
Local
Exchange
New CO
AGS
DPU
Cabinet
ONU
G.fast
<250 m
ADSL <7 km
VDSL <1.5 km
CP
WM
CP
CP
OLT

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NG-PON2 Status and Variants

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NG-PON2 Main (Operators’) Requirements
• 40G DS, 10G US minimum
• 20…40 (60) km passive reach
• 1:256 split to be supported
• Legacy (ODN) support and coexistence w/ G-PON, XG-PON1
(but filtered ODN is allowed as an option, e.g., for greenfield)
• Pay-as-you-grow approach
• Colorless ONUs, tunable lasers
• Optional PtP WDM overlay

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NG-PON2 Solutions discussed earlier
• 40-Gb/s single-wavelength TDMA (XLG-PON)
• Various WDM-PONs
• Coherent UDWDM
• Self-seeded / reflective
• Wavelength re-use (downstream-seeded / reflective)
• Externally (ASE) seeded / reflective
• … and the “winner” in the WDM-PON camp: tunable lasers
• OFDM(A)-PON (IM-DD, WDM-OFDMA, Coherent OFDMA)
• … and the main “winner”: TWDM

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NG-PON2 Main Variants
• Shared vs. Expanded Spectrum (co-existence w/ legacy PON generations)
• TWDM vs. PtP WDM
• 4, 8, more wavelength pairs
• TWDM 2G5 vs. 10G (US and/or DS), PtP WDM w/ 1G, 2G5, 3G, 5G, 6G, 10G, …
• Power split (preference) vs. filtered ODN
• N1 vs. N2 vs. E1 (vs. E2) reach options
• More (DFB vs. DBR lasers, cyclic AWG vs. TFF, …)
Loss N1 N2 E1 E2
Min. 14 dB 16 dB 18 dB 20 dB
Max. 29 dB 31 dB 33 dB 35dB

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A first NG-PON2 Configuration
• Co-existence of TWDM and PtP WDM (shared spectrum)
• Potential co-existence w/ G-PON, RF, XG-PON1 (brownfield)
• Up to 8 wavelength pairs for TWDM (8  32…64 users)
• Up to 16 PtP WDM wavelength pairs possible (best practice could be 8)
• Total split 256…512 will most likely require RE (27…31 dB power-splitter insertion loss)
…R/S
PtP ONU 1
PtP ONU N
WM
CEx
… S/R-CP
S/R-CG
… S/R-CP
WM
OLT Port 1
OLT Port 8
OLT PtP 1
OLT PtP 8
(L-/C-)
(L+)
…R/S
TWDM ONU 1
TWDM ONU N
1:k
Just an example
1:N
1:N
ODN (remember the reach classes…)
Just one possibility

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A Possible WM Implementation
Channel plan of a cyclic
8-skip-0 AWG (may slightly
change w/ final specification)
PtP US PtP DS
f0 187.6 THz M 21 f [THz] λ [nm] M 20 f [THz] λ [nm] M 19 f [THz] λ [nm] M 18 f [THz] λ [nm]
c0 299792458 m/s Ch -3 195.8433 1530.78 Ch -3 195.4436 1533.91 Ch -3 195.0439 1537.05 Ch -3 194.6442 1540.21
FSR 400 GHz Ch -2 195.8955 1530.37 Ch -2 195.4957 1533.50 Ch -2 195.0959 1536.64 Ch -2 194.6962 1539.80
Delta Grid 0.106609808 GHz Ch -1 195.9478 1529.96 Ch -1 195.5479 1533.09 Ch -1 195.1480 1536.23 Ch -1 194.7481 1539.39
df M0 50 GHz Ch 0 196.0000 1529.55 Ch 0 195.6000 1532.68 Ch 0 195.2000 1535.82 Ch 0 194.8000 1538.98
M-1 49.89339 GHz Ch 1 196.0522 1529.15 Ch 1 195.6521 1532.27 Ch 1 195.2520 1535.41 Ch 1 194.8519 1538.57
M-2 49.78678 GHz Ch 2 196.1045 1528.74 Ch 2 195.7043 1531.86 Ch 2 195.3041 1535.00 Ch 2 194.9038 1538.16
M-3 49.68017 GHz Ch 3 196.1567 1528.33 Ch 3 195.7564 1531.46 Ch 3 195.3561 1534.59 Ch 3 194.9558 1537.75
M-4 49.57356 GHz Ch 4 196.2090 1527.92 Ch 4 195.8085 1531.05 Ch 4 195.4081 1534.19 Ch 4 195.0077 1537.34
M-5 49.46695 GHz
M-6 49.36034 GHz M 1 f [THz] λ [nm] M 0 f [THz] λ [nm] M -1 f [THz] λ [nm] M -2 f [THz] λ [nm]
M-7 49.25373 GHz Ch -3 187.8497 1595.92 Ch -3 187.4500 1599.32 Ch -3 187.0503 1602.74 Ch -3 186.6506 1606.17
M-8 49.14712 GHz Ch -2 187.8998 1595.49 Ch -2 187.5000 1598.89 Ch -2 187.1002 1602.31 Ch -2 186.7004 1605.74
M-9 49.04051 GHz Ch -1 187.9499 1595.07 Ch -1 187.5500 1598.47 Ch -1 187.1501 1601.88 Ch -1 186.7502 1605.31
M-10 48.93390 GHz Ch 0 188.0000 1594.64 Ch 0 187.6000 1598.04 Ch 0 187.2000 1601.46 Ch 0 186.8000 1604.88
M-11 48.82729 GHz Ch 1 188.0501 1594.22 Ch 1 187.6500 1597.62 Ch 1 187.2499 1601.03 Ch 1 186.8498 1604.46
M-12 48.72068 GHz Ch 2 188.1002 1593.79 Ch 2 187.7000 1597.19 Ch 2 187.2998 1600.60 Ch 2 186.8996 1604.03
M-13 48.61407 GHz Ch 3 188.1503 1593.37 Ch 3 187.7500 1596.76 Ch 3 187.3497 1600.18 Ch 3 186.9494 1603.60
M-14 48.50746 GHz Ch 4 188.2004 1592.94 Ch 4 187.8000 1596.34 Ch 4 187.3996 1599.75 Ch 4 186.9991 1603.18
M-15 48.40085 GHz
M-16 48.29424 GHz M -3 f [THz] λ [nm] M -4 f [THz] λ [nm] M -5 f [THz] λ [nm] M -6 f [THz] λ [nm]
M-17 48.18763 GHz Ch -3 186.2510 1609.62 Ch -3 185.8513 1613.08 Ch -3 185.4516 1616.55 Ch -3 185.0519 1620.05
M-18 48.08102 GHz Ch -2 186.3006 1609.19 Ch -2 185.9009 1612.65 Ch -2 185.5011 1616.12 Ch -2 185.1013 1619.61
M-19 47.97441 GHz Ch -1 186.3503 1608.76 Ch -1 185.9504 1612.22 Ch -1 185.5505 1615.69 Ch -1 185.1506 1619.18
M-20 47.86780 GHz Ch 0 186.4000 1608.33 Ch 0 186.0000 1611.79 Ch 0 185.6000 1615.26 Ch 0 185.2000 1618.75
M-21 47.76119 GHz Ch 1 186.4497 1607.90 Ch 1 186.0496 1611.36 Ch 1 185.6495 1614.83 Ch 1 185.2494 1618.32
M-22 47.65458 GHz Ch 2 186.4994 1607.47 Ch 2 186.0991 1610.93 Ch 2 185.6989 1614.40 Ch 2 185.2987 1617.89
M-23 47.54797 GHz Ch 3 186.5490 1607.04 Ch 3 186.1487 1610.50 Ch 3 185.7484 1613.97 Ch 3 185.3481 1617.46
M-24 47.44136 GHz Ch 4 186.5987 1606.62 Ch 4 186.1983 1610.07 Ch 4 185.7979 1613.54 Ch 4 185.3974 1617.03
The same CAWG can be used
for TWDM and PtP WDM

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Completely different NG-PON2
• No co-existence w/ TWDM, G-PON, XG-PON1, and/or RF
• Considered greenfield only
• Overlap with SG15-Q.6 G.metro pWDM / WDM-PON
• Will most likely have 40…48 WDM channel pairs
• Power-split or filtered ODN (cyclic AWGs acc. to G.698.3 shown here)
• Full-band tunables lasers
G.698.3CAWG
OLT PtP 1
S/R-CG
…
OLT PtP N
… S/R-CP R/S
G.698.3CAWG
PtP ONU 1
PtP ONU N
ODN

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Another ODN Variant…
WM
…R/S
PtP ONU 1
PtP ONU N
L-
L+
WM
…R/S
TWDM ONU 1
TWDM ONU N
1:k
1:k
• Not the preferred variant, but not explicitly forbidden
• Co-existence possible, but unlikely (greenfield more likely since OTDR wouldn’t work properly)
• Total split 8  32…64 + 8…16, can be done passively (max. 19…23 dB IL)
• Could avoid tunable ONU RX filters
WM
CEx
… S/R-CP
S/R-CG
… S/R-CP
WM
OLT Port 1
OLT Port 8
OLT PtP 1
OLT PtP 8
(L-/C-)
(L+)

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Some NG-PON2 Challenges
• Crosstalk, SMSR of transmitters
• Crosstalk, Raman depletion of RF channel at 1555 nm
• Laser tuning: silent start, control, signaling, step width, speed,
anti-rogue measures, … (not covered hereinafter)

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Coherent Intra-Channel Crosstalk
f
Incoh. XT
SMSR
Incoh. XT
Co. XTCo. XT
Amplitude
Interferometric Crosstalk [dB]
-15-20-25-30-35-40
0
1
2
3
Penalty[dB]
Ideal Signal
6 dB ER
Wanted Signal, single Interferer:
• Coherent intra-channel crosstalk is the
most severe linear crosstalk in NG-PON2
• Caused by interferer side modes
• In upstream direction and for non-filtered
ODN only (side modes cannot be rejected
in OLT demultiplexing filter)
From ITU-T Rec. G.Sup39

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Counter-acting Intra-Channel Crosstalk
Tighten several parameters simultaneously
Compared to initially targeted values, several parameters have to be tightened. A possible combination is:
• Increase crosstalk penalty from PEN = 0.1 dB to PEN = 0.5 dB
• Higher ER, optimized threshold of transceivers. May give ~4 dB.
• Limit number of WDM channels to 4 only (per TWDM or PtP)
• Mandatory FEC w/ NECG = 6 dB (FEC was optional)
Leads to 46 dB SMSR (i.e., no VCSELs!). Increased PEN = 0.5 dB means that launch power must be increased.
Provide additional filter isolation
As an alternative to parameter tightening, and as means for allowing higher channel count, additional filter isolation can be used.
• Add ODN multiplexer isolation. This can give >20 dB XT improvements.
• Still requires slightly increased PEN = 0.2 dB
Filtered ODN! Alternatively, isolation can be added by per-ONU tunable TX filter (higher cost, higher total insertion loss).
Provide ONU power-level control
With added ONU power-level control, the differential path loss can be equalized. Further parameters have to be tightened.
• Power-level control. Relaxes XT requirements by >10 dB.
• Allow higher PEN = 0.5 dB
• Higher ER, better threshold
ONU power-level control is not common in ITU PONs so far.

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NG-PON2 Spectrum and Raman Crosstalk
• Low-frequency part of RF channel most affected – Raman depletion
• Caused by co- or counter-propagation waves (intensity-dependent)
• Counter-measures discussed include interferer high-pass filtering, interferer polarization control,
a dedicated Raman XT equalization transmitter, and PSD shaping, e.g., through line codes
Guard
Bands
1400 1480 16001500 1650
OH- Peak
1440 1550
RF
13001250 1350
TWDMDS
GPONUS
(narrow)
GPONDS
XG-PONUS
PtPUS
PtPDS
XG-PONDS
OTDR
Typical SSMF Attenuation
Raman Gain Curve
TWDMUS
E-Band S-Band C-Band L-BandO-Band U-Band

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Conclusions

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Conclusion
• NG-PON2 can come in many different variants
• It can provide high dedicated or shared bandwidth
• It can support various access, backhaul and fronthaul applications,
including the network consolidation for these applications
• Some parameters and specs are still subject to standardization…
• … nonetheless, it’ll become a strong standard

20. KGrobe@ADVAoptical.com
Thank You
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