Optical components – access lessons learned applied to datacenters David Piehler Fields and Waves, Los Gatos, California
[email protected] OFC Workshop S1D Short Reach Optical Networks – Highly Synergistic or Different Worlds? 22 March 2015, Los Angeles 1
Some history FTTH pre-history: (1) Optical integration will enable low-cost subscriber units. (2) Industry developed PIC-based transceivers and triplexers. NeoPhotonics (2005)
Historic record: 2009 – 2012 surge (due to China FTTx and mobile growth) in single-mode sources was served by TO-can-based TOSAs and BOSAs.
Lasers shipped (× 106)
80 70 60 50 40
GaAs VCSEL (multimode) InP edge-emitter (single-mode)
30 20 10 0 2000
2005
Year 2010
2015
lasers in TO-cans
transmitter optical sub-assembly (TOSA)
bi-directional optical sub-assembly (BOSA)
Source: Karen Liu, Ovum, 2014.
TO-can was not originally intended for optics or high speed, yet it dominates today at 10 Gb/s (and 16GFC). Experiments show TO-can-based TOSAs and ROSAs working at > 50 Gb/s.
Sony Discman D-50 (1984) Contained Fabry–Pérot laser and photodiode in TO-cans ($395)
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Building a TO-can-based TOSA aspheric or BOSA isolator lens-cap TO-header laser
WDM AR
fiber stub
photodetector (+TIA) in TO-can with ball lens Key points: (1) Cost (not price!) of single-mode TOSA package (including hermeticity, isolator, coupling, labor, overhead) MINUS laser cost ≤ $5*. (2) Cost (not price!) of single-mode BOSA MINUS laser cost, MINUS photodetector/TIA cost ≤ $9* Packaging cost is nearly (ask me why) speed independent. *Ferris Lipscomb, “PIC vs. Si Photonics: Hype or Reality,” Market Watch, OFC-2014. www.ofcconference.org/library/images/ofc/2014/Market Watch and SPS/ferris.pdf
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Why love BOSAs? • Low-cost • Predictable-cost (> 10M shipped annually) • Pain-free WDM • Filter is simple high/low-pass design • Laser-to-fiber coupling (> 60%, over all conditions with asphere); robust against astigmatism due to WDM filter. • Photodetector's WDM loss penalty < 0.3 dB.
• Only slightly larger than a TOSA. • SFP (and MMF QSFP) modules exist with two BOSAs
40GBASE-SR-BD QSFP (multimode fiber)
(single-mode fiber) Source: GigaLight
Source: Cisco
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Moving 100G in the datacenter – 10λ → 4λ → ? Tx λ Tx λ 1
Tx λ2 Tx λ3 Tx λ4 Tx λ5
Rx λ1 Rx λ2 Rx λ3 Rx λ4 Rx λ5
6
Tx λ1
Tx λ7
Tx λ2
Tx λ8
WDM
Tx λ9
Tx λ3
WDM
Tx λ1 Tx λ2
WDM
Tx λ4
Rx λ1
Rx λ7
Rx λ2
Rx λ8 Rx λ9
WDM
Rx λ3
Rx λ2
WDM
TOSA
BOSA1
Tx λ10 Rx λ6
Tx λ1
WDM
Rx λ1
WDM
Rx λ2
Rx λ4
Tx λ2
WDM
ROSA
Rx λ1
BOSA2
Rx λ10
2-λ wrong way (ask me why)
2-λ 2-BOSA
1-λ 5
Moving 100G in the datacenter – 10λ → 4λ → 2λ End-game: 2-λ, 2-BOSA transceiver is always best Dramatic (single-mode) optical packaging cost-reduction happens when N×λ → 2×λ, not when N×λ → 1×λ • • • •
It’s fairly painless to turn any TOSA into a BOSA BOSA size is ~ ½ × (TOSA+ROSA) Fiber utilization increases by 2× Minimal cost impact (< $3)
Tx λ1 Rx λ2
TOSA
BOSA1
BOSAs are happiest in pairs creating universal transceivers.
Tx λ2
(e.g. the Cisco QSDP BD on slide 4. Ask me how to use statistical DWDM to make single fiber 2-λ universal transceivers: Piehler, ECOC-2013, Tu.1.B.1)
Rx λ1
Use the 2-λ, 2-BOSA architecture in two ways: (1) Simplify a 100G serial problem into two easier 50G serial problems (lower-cost electronics and optics) (2) If (2-fiber) 100G serial is no problem, then immediately upgrade to a (2-fiber) 200G transceiver
WDM
WDM
ROSA
BOSA2 2-λ 2-BOSA
1-λ 6
Another lesson learned – angled connectors Ask me how.
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