Scaling PON OLT port utilization: HFC-style Panel NM3J: PONs as Used by MSOs Monday, 18 March 2013
David Piehler
[email protected]
Piehler · Scaling PON OLT port utilization: HFC-style · Panel NM3J · OFC/NFOEC-2013 · Anaheim · 18 March 2013
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Lessons from early cable-modem deployment ● All-digital HFC technology shares many features with PON technology – Both are point-to-multipoint access networks » Broadcast downstream; TDMA upstream » Shared transmission medium (coax + fiber; fiber) » Tree and branch structure, with (RF/optical; optical) splitters
● But, the cable network is not passive between the CMTS* and CM – Use of hybrid fiber-coax (HFC) optical transmission and bi-directional RF amplifiers enabled > 100 km reach and > 10,000:1 split ratios for the first CM deployments in the 1990s. coax
ONU OLT
fiber
ONU ONU
CMTS
RF/O
CM fiber
CM
O/RF bi-di RF amp
PASSIVE OPTICAL NETWORK
CABLE ACCESS NETWORK
distance / split ratio (presently limited) by ~ 30 dB optical budget: ~1:128 at 2 km ~1:64 at 10 km ~1:32 at 20 km ~1:16 at 30 km
distance / split ratio can be > 100 km / > 10,000:1
CM
*CMTS = cable modem termination system (analogous to PON OLT)
Piehler · Scaling PON OLT port utilization: HFC-style · Panel NM3J · OFC/NFOEC-2013 · Anaheim · 18 March 2013
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Pay-as-you-grow – a key part of the cable modem story ● For the first cable modem deployments in the mid-1990s, one CMTS might serve an entire city. – A >10,000:1 split-ratio enabled the MSO to market CM service to every home in that city on day-one of deployment. – A >10,000:1 split-ratio enabled the MSO provide CM service to the first N customers, who might live anywhere in that city. – Only after the first N customers began to consume the bandwidth of the first CMTS, the MSO installed their second CMTS. – MSO’s CMTS CapEx was linked to the growth of the customer base, and revenue. • Today, 15 years later, MSOs are approaching 128 homes passed per DOCSIS service group (CMTS port).
● Initial cable modem deployments would have failed if CMTS ports were limited to 128:1 split-ratios or few-km reach. – Successful cable modem deployment required a pay-as-you grow economic model – CMTS must support large split-ratios and long reaches on day-one.
● Today MSOs aggressively implement port-licensing models to align bandwidth utilization and growth with costs.
Piehler · Scaling PON OLT port utilization: HFC-style · Panel NM3J · OFC/NFOEC-2013 · Anaheim · 18 March 2013
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But… physics rules! (the PON link budget) ● PON link-budgets, distances and split-ratios have been determined by optical physics, not by economics or business requirements ● Questions to ponder: – Is a 32- or 64-ONU service group optimum for MSO requirements? – Is 128:1, 256:1 or 2[some big number]:1 a more appropriate ONU per OLT port ratio for today?
● A higher-split-ratio PON would enable: – A lower first-deployment cost for carriers (pay-as-you grow economics). – Centralization of central offices / headends for lower real-estate costs. – Energy savings (fewer PON OLT ports are lit up on day-one.)
● The mode-coupling receiver breaks gets around the physics rules.
Piehler · Scaling PON OLT port utilization: HFC-style · Panel NM3J · OFC/NFOEC-2013 · Anaheim · 18 March 2013
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The mode-coupling receiver (MCR) From: D. Piehler, “PICs in PONs,” OFC-2012, NTu1J.6.
6+ dB loss (1310 nm)
APD
(1490 nm)
DFB
1×4 singlemode splitter
WDM
PON OLT transceiver + external 1×4 splitter 6 dB of loss in both directions
6+ dB loss active area of APD (Φ~50-μm)
0+ dB loss WDMs
mode coupling receiver
4-port PON OLT transceiver with integrated splitter / MCR loss-less in upstream direction photonic integrated circuit (PIC)
All functionality (←) integrated onto a < 20 mm PIC Downstream power is boosted to accommodate splitter loss
DFB
1×4 splitter 6+ dB loss
Packaged into standard SFP module, with four-fiber MTP connector. (< 10 mm longer than standard GPON OLT SFP)
Piehler · Scaling PON OLT port utilization: HFC-style · Panel NM3J · OFC/NFOEC-2013 · Anaheim · 18 March 2013
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Minimizing headend CapEx, maximizing bandwidth utilization Conventional
32 homes passed per OLT port
Four PON OLT ports with four standard SFP transceivers
Reduction in:
PON OLT line-card Replaced by
28 dB OSP link-budget
128 homes passed per OLT port
• • • •
transceivers line-cards space power
one PON OLT port and one MCR SFP tranceiver fiber distribution frame From: D. Nesset, D. Piehler, K. Farrow and N. Parkin, “GPON SFP tranceiver with PIC-based mode-coupled receiver,” ECOC-2012, Tu.3.B.4. Piehler · Scaling PON OLT port utilization: HFC-style · Panel NM3J · OFC/NFOEC-2013 · Anaheim · 18 March 2013
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The MSO’s business case for the mode-coupling receiver Base case:
Pay-as-you-grow with MCR:
• 4 OLT ports with standard SFPs deployed on day-one
• One OLT port with one 4-port MCR SFP on day-one; standard SFPs for future growth
• OpEx assumed at 10% of CapEx • Discount rate of 10% / year • Fully loaded OLT port price on day-one = 100 units
Total cost in today’s money after 8 years: Base case: 630 units Pay-as-you-grow: 350 units
• OpEx assumed at 10% of CapEx • Discount rate of 10% / year • Equipment prices drop 10% / year
Value of one MCR OLT SFP to the MSO: 280% × (loaded cost) PON OLT port
Piehler · Scaling PON OLT port utilization: HFC-style · Panel NM3J · OFC/NFOEC-2013 · Anaheim · 18 March 2013
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The mode-coupling receiver reduces headend power consumption by 74%
From: S. Gosselin, F. Saliou, F. Bourgart, E. Le Rouzic, S. Le Masson and A. Gati, “Energy consumption of ICT infrastructures: An operators viewpoint,” ECOC-2012, We.1.G.4. Piehler · Scaling PON OLT port utilization: HFC-style · Panel NM3J · OFC/NFOEC-2013 · Anaheim · 18 March 2013
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Scaling up – 1×2048 10G-EPON (IEEE 802.3ab) using an L-band EDFA and mode-coupling receiver ● Use relaxed spec L-band EDFA and mode-coupling receiver to create 10G-EPON OLT supporting 1×2048 split ratio. – Simple L-band EDFA • Single wavelength – (1565–1605 nm operating range) → (1575–1581 nm operating range) – No gain flatness requirement
10G PON OLT LINE CARD
• Constant +21 dBm output power
TO OLT MAC
CDR
L‐band EDFA FROM OLT MAC
10G Tx
1×32 single‐mode Splitter (1 dB excess loss)
1×64 WDM1
optical splitter
WDM2 (0.5 dB excess loss)
…
TIA
32×1 single‐mode fiber to photo‐ detector coupler (1 dB loss)
32 ports each with Pout = +4 dBm Psens = –28.0 dBm
use two for 64port line-card
WDM31 WDM32
From: D. Piehler, “Implementing High [>2048] Split Ratios in any PON,” OFC-2011, paper NThF4. Piehler · Scaling PON OLT port utilization: HFC-style · Panel NM3J · OFC/NFOEC-2013 · Anaheim · 18 March 2013
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Summary
● Mode-coupling receiver technology lets PON OLT ports act like a CMTS ports. – Providing a very-high split-ratio on day-one of deployment. – Allows (truck roll free) network splitting for smaller MAC-domain service groups* as subs increase and higher-bandwidth services are deployed.
*homes passed per PON OLT port Piehler · Scaling PON OLT port utilization: HFC-style · Panel NM3J · OFC/NFOEC-2013 · Anaheim · 18 March 2013
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