1. Wavelength Issues in the Downstream Direction James O. “Jim” Farmer Alan M. Brown Enablence Technologies (Wave7 Optics) IEEE 802.3av meeting, November 2008

2. Wavelength Issues in the Downstream Direction V-OLT OLT Upstream Broadcast (extended services) Downstream data Upstream data Optical subassembly Passive optical network (PON) down WDMWDM 1550 Must attenuate opposite signal >30 dB ONT

3. Wavelength Establishing View (Wavelength is to Scale) 12701320137014201470 Wavelength (nm) 1 Gb/s upstream 10 Gb/s upstream Today’s 1 Gb/s downstream (1490 nm) Broadcast 1550 nm 1577 +/-3 nm downstream 1590 nm down- stream 14 nm nominal transition Today’s 50 nm nominal transition (comfortable) 1520 20 nm nominal transition 1570

4. But Wait! It Gets Worse ) When we take tolerances and temperature drift into account, the situation gets worse 5 So we will make certain concessions to the real world 5 Broadcast (extended services) band 5 Was 1550 - 1560 nm (existing transmitters) 5 Make it 1550 - 1555 nm 5 1577 nm data down 5 Was and is 1577 +/-3 nm 5 1590 nm data down (currently not in standard) 5 Was 1590 +/-10 nm 5 Make it 1590 +/-3 nm 5 Makes OLT somewhat more expensive, but maybe not prohibitively so. Makes ONT easier ) We shall make these assumptions and look at the implication for using broadcast with downstream data. We will not look at upstream data transmission at this time. Those messy, practical details

5. Assume we try to use 1577 nm with broadcast 15401550156015701580159016001610 Wavelength (nm) Reduced broadcast wavelength 1. Specified 1577 nm data wavelength 2. Practical filter bandwidth after taking into account temperature drift and initial center frequency tolerance

6. Assume we try to use 1577 nm with broadcast 15401550156015701580159016001610 Wavelength (nm) Reduced broadcast wavelength Practical filter Filter center frequency is low, and temperature forces it even lower 1 nm transition - Impossible!!!

7. Now try it with a downstream wavelength of 1590 nm 15401550156015701580159016001610 Wavelength (nm) Reduced broadcast wavelength 1. Specified 1590 nm data wavelength (reduced bandwidth) 2. Practical filter bandwidth after taking into account temperature drift and initial center frequency

8. 15401550156015701580159016001610 Wavelength (nm) Now try it with a downstream wavelength of 1590 nm Reduced broadcast wavelength Practical filter Filter center frequency is low, and temperature forces it even lower 14 nm transition. Tight, but much better than 1 nm

9. Conclusion ) Use of the broadcast overlay with a 1577 nm data carrier is impossible ) Use of the broadcast overlay with a 1590 nm data carrier is difficult, but should be feasible ) We do not object to use of 1577 nm for PR(X)30 ) We seek reinstatement of the 1590 nm wavelength in order to preserve use of the broadcast overlay, which we have agreed is still important