Transcript
AT&T Labs-Research
WDM Overlay of APON with EPON - a carrier’s perspective Nicholas J. Frigo & Cedric F. Lam Optical Systems Research Dept., AT&T Labs - Research 200 S. Laurel Ave., Middletown, NJ 07748, USA
Wavelength Allocation in ITU-T Rec. G.983.3 AT&T Labs-Research
customer premise central office WDM
APON OLT
APON ONU EONU
1:32 WDM
EOLT
Enhanced band (option 2): For video distribution Enhanced band (option 1): For future additional digital APON use service downstream
APON upstream
For future use
L-band 1260
1360
1480 1500 1539 1550 1560 1565
EOLT: enhanced OLT
EONU: enhanced ONU
wavelength (nm)
The Value of Fiber Plant AT&T Labs-Research
Estimated Cost per Building to Deploy Fiber in a Passive Optical Network $ per building Aerial Exist Conduit Trench New Conduit
Outside Plant 4,161 4,161 4,161 4,161
Labor 3,787 4,436 14,199 26,299
ONU 4,435 4,435 4,435 4,435
OLT 1,247 1,247 1,247 1,247
Total Cost $13,630 $14,279 $24,042 $36,142
Source: Merrill Lynch, Corning Cable Systems
1.5µ µm Optical Window
“Infinite” Bandwidth
≈
10,000 GHz
1.3µ µm Optical Window 10,000 GHz
100 GHz 1 GHz Coax Capacity
1 GHz Satellite Capacity
Low Cost Coarse WDM Technology AT&T Labs-Research
!
DWDM: " "
!
Intensity
High-cost, high-capacity Core network technology
100GHz
DWDM (Dense)
CWDM: Low-cost, moderate-capacity " Suitable for metro & access (i.e.: the FIRST MILE) "
CWDM (Coarse) 20nm
Wavelength
CWDM Usage !
10GBASE-LX4 (IEEE802.3ae): " "
!
Low cost CWDM parallel PHY standard for 10Gb/s Ethernet 20nm bands centered at: 1290, 1310, 1330 & 1350nm
De facto standard: " 20nm bands centered at 1491, 1511, 1531, 1551nm...
Wavelength Accuracy Requirements AT&T Labs-Research
!
ITU-T 983.3 standard temp requirements. " " "
!
DFB laser accuracy "
!
temp coefficient: 0.08nm/oC ⇒ 7.2nm over 90oC for uncooled DFB
Athermal thin film CWDM "
!
OLT: 5 to 40oC Indoor ONU: -5 to 45oC Outdoor ONU: -45 to 45oC
temp coefficient: 2pm/oC ⇒ 1.8nm over 90oC
Use 10nm band with 20nm separation "
15 available bands between 1300nm and 1600nm
Cost Considerations AT&T Labs-Research
!
DWDM. " " "
!
ITU grid DFB laser: $1,000 DWDM Mux-Demux: $200 - $500 per wavelength Temperature control required.
CWDM " "
Uncooled DFB: $50 - $100 CWDM: $50-100 per wavelength Fiber plant costs at least ~$14,000 per user...
!
Need a standard for “plug-N-play” CWDM technology
Emerging Low Cost WDM Components … AT&T Labs-Research Intensity
Band 1.3- 1.3+ 1.4- 1.4+ 1.5- 1.5+ Wavelength (µm)
1.3-
1.4-
1.5-
Sorter 1.3+
1.4+
Intensity
Band 1.3 1.3 +
1.5 1.5 - +
1.3 -
1.5 -
Sorter
Wavelength (µm)
• Gratings • Thin films • Planar waveguide circuits
1.3 +
1.5 +
1.3/1.5 WDM “diplexer”
1.5+
… Overlaying APON with EPON AT&T Labs-Research
Pave the way for diverse future services. Central Office
Band PS
EPON OLT
Sorter
Feeder Fiber
Sorter
T EPON R ONU 1
...
Backbone Network
APON OLT
Band
T APON R ONU 1
Band Sorter
• 2 PONs for 1 infrastructure – Low cost CWDM (band sorter) overlay – $ band sorter << $ ONU << $ fiber • Flexible service provisioning – e.g. video overlay in other bands like in ITU-T Rec. 983.3
T EPON R ONU2
Which One to Choose? AT&T Labs-Research
Option 1: band sorter
1.3-
1.3+
1.4-
1.4+
Option 2: ITU-T Rec. G.983.3
1.5-
Enhanced band (option 1): For future additional digital APON use service downstream
APON upstream
1.5+
wavelength (nm)
Enhanced band (option 2): For video distribution For future use
L-band 1260
1360
1480 1500 1539 1550 1560 1565
wavelength (nm)
Option 3: de facto CWDM standard
20nm
wavelength (nm)
Power Budget Consideration AT&T Labs-Research
!
ITU-T REC 983.3 " "
!
class B: 25dB between OLT and ONU class C: 30dB between OLT and ONU
CWDM: Extra wavelength filters add additional loss " 8dB (4dB mux + 4dB demux) CWDM loss (average value for commercial 8 band CWDM devices) " EPON/GbE (1.25Gb/s) requires 3dB more power than 622Mbps APON " Amplification over 200-300nm wide optical band is not easy "
!
Solutions: " " " " "
Apply higher power LDs (lasers are getting better everyday!) Use APD detectors (10 to 15dB gain) Use FEC (~10dB gain) Reduce splitting ratio Reduce fiber reach
