Wavelength-Enhanced Passive Optical Networks with Extended Reach Ken Reichmann and Pat Iannone Optical Systems Research AT&T Labs, Middletown NJ Thanks to Han Hyub Lee, Xiang Zhou, and Pete Magill
Wavelength-Enhanced Passive Optical Networks with Extended Reach I. TDM-PON Overview
Broadband Access Architectures Single star star Secure Costly entrenched BB access Triple-play today Hybrid Fiber -Coax Hybrid Fiber- Coax Active double star Active double star More economical than single star for long fiber runs No actives in field Reduced maintenance and operations Passive Optical Network(Fiber (Fiber to to the the Home) Home) Passive Optical Network BB Access with Fixed Wireless Drops Low cost drop Make the business Case at lower take rates Single star, radio drop PON, radio drop Lower cost per sub than FTTH Less BW than FTTH Fiber Fiber to to the node curb (or Fiber to the Node) curb) Active electronics Passive optics Fiber Copper Radio
Passive Optical Network Types (PONs: no actives or powering in outside plant) Power Splitting Star electrical WDM Star λ Users share bandwidth Systems available today Cheap optics Unamplified WDM Hubbed Ring (e.g. ITU G.983) Users Dedicated λ per user Low loss, high BW More expensive than power splitting (e.g. CWDM for business, DWDM w/ Colorless ONTs, etc) Hub OADM Dedicated λ per user Low loss, high BW OADMs in Multiple locations (e.g. Cogent s CWDM FTTB network)
622 Mb/s downstream, 155 Mb/s upstream 20 km logical reach layer 2 protocol: ATM TDM PON Standards APON, BPON (ITU G.983.1 to G.983.8 ratified from 1998 to 2003) GPON (ITU G.984.1 to G.984.4 ratified from 2003 to 2004) 2.5 Gb/s downstream, 1.25 Gb/s upstream 60 km logical reach, 20 km differential logical reach, up to 1:128 split Layer 2 protocol: Ethernet over GEM (generic encapsulation method) Improved bandwidth efficiency (92% downstream) EPON (IEEE 802.3ah ratified 2004) 1.25 Gb/s downstream, 1.25 Gb/s upstream 20 km logical reach Layer 2 protocol: Ethernet Takes advantage of Ethernet cost structure Line Rate (Mb/s) 10000 1000 100 APON BPON GPON EPON downstream upstream Lower bandwidth efficiency (72% downstream) 10 1996 1998 2000 2002 2004 2006 2008 Year
GPON is FTTH Network of Choice in N. America Natural migration from BPON: Supports legacy TDM svcs, Ethernet, IP Video is essential: Delivered over IP (IPTV) or over a separate optical band as conventional analog subcarriers (Enhancement Band as per BPON, G.983.3) Reach: Class B+ (28-dB) link budget allows 1:32 split with 20 km reach (1:128 split, 60 km logical reach permitted by standard but not practical today) 20 km CO OLT TDM down 1480-1500 nm TDMA up 1260-1360 nm Passive Splitter ONT ONT Video OLT Video 1550 nm OLT = Optical line terminal ONT = Optical network terminal Up to 32 ONTs ONT
Wavelength-Enhanced Passive Optical Networks with Extended Reach II. PON Evolution Beyond Current GPON (EPON)
ONT Blocking Filters Permit λ Upgrades Standard GPON ONT 1 CO = Blocking filter ONT 8 ONT 9 PON OLT TDM down 1480-1500 nm 1:32 Splitter ONT 17 ONT 16 TDMA up 1260-1360 nm ONT 25 ONT 24 The addition of an inexpensive blocking filter to the standard GPON ONT allows unaffected GPON operation as new wavelengths (future services) are added for some users ONT 32
ONT Blocking Filters Permit λ Upgrades C+L-band blocking filter will likely be standardized by ITU-T later this year Upgraded GPON (showing two new services) 3-D TV Gig E PON OLT CO W D M New λs TDM down 1480-1500 nm TDMA up 1260-1360 nm 1:32 Splitter 2 λs per symmetrical svc (e.g. Gig E) 1 λ per asymmetrical svc (e.g. 3-D TV) Only upgrade ONTs requiring new service = Blocking filter ONT 1 ONT 8 ONT 17 ONT 24 ONT 25 ONT 32 ONT 9 ONT 16
TDM PONs with Extended Reach / Split I. Tactical use of a TDM PON Extender Box TDM down 1480-1500 nm Remote Node (Primary Flexibility Point) ONT 1 PON OLT TDMA up 1260-1360 nm Common Cable Extender Box 1:32 ONT 2 ONT 32 20-60 km Extend current generation GPON (within 60 km logical limit) 40 km would likely be sufficient given current placement of AT&T COs Use extender box only for those GPONs that would otherwise require remote OLT Extender box has cost advantages (capex and opex) over powered remote OLT Consider OEO or optical amp-based extender box One extender box circuit per PON minimizes change to GPON architecture No additional wavelength or electronic muxing (thus minimizing changes to OSS)
TDM PONs with Extended Reach / Split I. Tactical use of a TDM PON Extender Box OEO version: Zenko Technologies (Yusuke Ota) Repeater Optically-amplified version (SOAs): Alphion 1550 nm external video optical amplifier (EDFA) (optional) 1310 nm 1490 nm 1555/ (1490,1310) WDM 1310 nm 1310 nm 1310 nm 1490 nm 1490 nm photo diode 2x2 tap coupler 1310/ 1490 WDM 1490 nm photo diode BPF 1310 nm 1490 nm 1490 nm SOA 1310 nm SOA control electronics BPF 1310/ 1490 WDM 1310 nm photo diode 2x2 2x2 fused tap fiber coupler coupler 1310 nm 1490 nm 1555/ (1490,1310) WDM photo diode 1490 nm 1310 nm 1490 nm
TDM PONs with Extended Reach / Split II. Strategic (long term) Use of Extender Box BT s Long-Reach PON Strategy CO Serving Area (20 km radius) Central Office Red lines represent subset of individual PONs
TDM PONs with Extended Reach / Split II. Strategic (long term) Use of Extender Box BT s Long-Reach PON Strategy (see Davey and Payne, ECOC 05, paper WE2.1.3) Long-reach PONs (60 100 km max reach) Eliminate majority of COs Saves on: powering, real estate Avoids remoting OLT Possibly increase users per PON WDM or TDM muxing between OLT and Extender Box Shares feeder fiber Reduces fiber management issues New Central Office Red lines represent subset of individual PONs
TDM PONs with Extended Reach / Split II. Strategic (long term) Use of Extender Box Bi-Directional Extender Box Based on Hybrid SOA-Raman Amplifiers Downstream CWDM λ s (nm) 1490 1510 1530 1550 1290 1310 1330 1350 1.3/1.5 µm MUX 1.5 µm SOA Raman Fiber 1272 nm 4.5 km Raman Pumps 3.5 km 1456 nm 1500-nm SOA: 300mA 4.5-km Raman Fiber Raman pump: 247 mw@ 1456 nm Upstream 1300-nm SOA: 300mA 3.5-km Raman Fiber Raman pump: 310 mw@ 1272 nm 24 SRHA : Gain NF PDG SOA Gain RFA Gain 30 Hybrid : Gain NF PDG SOA gain RFA gain 20 25 Downstream Gain / NF (db) 16 12 8 4 GPON band Enhancement band Gain / NF (db) 20 15 10 5 Upstream 0 0-4 1460 1480 1500 1520 1540 1560 Wavelength (nm) -5 1280 1300 1320 1340 1360 Wavelength (nm)
Experimental Set-Up CO OLT Tx Remote Node ONT 1.5 µm Rx 1490 nm DFB-LD 1510 nm DFB-LD 1530 nm DFB-LD 1550 nm DFB-LD CO OLT Rx 1290 nm Rx 1310 nm Rx 1330 nm Rx 1350 nm Rx C W D M C W D M 60 km 1.5-μm Hybrid Amp 1.3-μm Hybrid Amp C W D M C W D M 2:2 2:2 2:2 2:2 1:16 1:16.... 1.3 µm Tx 1490 nm down 1310 nm up 1510 nm down 1290 nm up 1530 nm down 1330 nm up 1550 nm down 1350 nm up 1.3/1.5 μm Mux 2.488 Gbps, 2 31-1 PRBS, Up and Down Note: The erbium-doped fiber amplifier (EDFA) revolutionized optical communications with its capability of simultaneously amplifying a multiplicity of WDM channels. Due to low cost and high performance, it remains the only broadly deployed optical amplifier technology despite the fact that it has a limited optical bandwidth the hybrid amplifier may fill the niche for broadband (multi CWDM or DWDM) gain at any wavelength.
Error Probability (10 -Y ) 3 4 5 6 7 8 9 10 1.5 um Amp + 1.3 um Amp + 60 km Up Down 1490 nm 1510 nm 1530 nm 1550 nm 11-37 -36-35 -34-33 -32-31 -30-29 Received Power (dbm) Experimental Results Error Probability (10 -y ) 3 4 5 6 7 8 9 1290 nm 1310 nm 1330 nm 1350 nm 10 11-37 -36-35 -34-33 -32-31 -30-29 Received Power (dbm)
Summary Potential enhancement strategies for TDM-PONs A. Wavelength upgrades permitting increased capacity or additional services B. Increased link budget for moderate extended reach / split Hybrid amp suitable for non-erbium band amplification in access and metro enables A & B simultaneously Broad bandwidth (>80 nm) Reasonable and Bidirectional gain (> 18 db in latest demonstration) Flexible design: flat gain in any band in optical fiber Four 60 km PONs sharing a common infrastructure
Backup Slides
DWDM PON with Colorless ONTs Impressive technological achievement Colorless ONTs Futureproof outside plant But not ready for volume FTTP deployment (despite KT roll-out) BLS (Broadband Light Source) output power requirements Cost per user Polarization dependence Susceptibility to discrete and distributed reflections Channel amplitude variation Will low-cost DFBs be available by time real demand appears? Source: White paper by Novera Optics, Inc.