1. EXTENDING THE REACH OF VCSEL BASED 100 GB/S
MULTIMODE PARALLEL OPTIC LINKS

2. Presentation Outline
• Fiber Optics 101
• The Fiber Optic Link: Test Points and Measurements
• 100 Gb/s Multimode Links in the Network
• Link Distance: Limiting Factors and the Need to Extend
• Test Module Description
• Transmitter Module Test Setup and Results
• Receiver Module Test Setup and Results
• Conclusions

3. Fiber Optics 101
Optical Wave-Guide
E
O
O
E
Transmitter
(TOSA)
Receiver
(ROSA)
Transmitter includes:
(1) LED or LASER
(2) Laser Driver circuit
The driver circuit converts diff
signaling into bias/modulation
current to the laser. The LASER
converts the electrical signal to an
optical signal.
Receiver includes:
(1) PiN or APD Photo Detector
(2) Receiver circuit
The Photo Detector converts the
optical signal to an electrical current
while the Receiver circuit performs
signal conditioning and quantization.
Transmission of the optical signal
is accomplished by a wave-guiding
medium such as a step, or a
graded index optical fiber
Digital communication using pulses of light that propagate through long, thin, solid glass or plastic waveguides

4. Fiber Optics 101: Singlemode vs Multimode
Optical Fiber Type
• Single-mode glass (SMF), 9um diameter
• Multi-mode glass (MMF, graded), 50um/62.5um diameter
• Multi-mode glass (HCSF, step), 200um/400um diameter
• Multi-mode plastic (POF, step), 1000um diameter
Single mode for link distances > 1 km
Multimode for link distances < 300 m

5. Fiber Optics 101: Singlemode vs Multimode
Optical Source Type
• Vertical Cavity Surface Emitting Laser (VCSEL)
• Fabry-Perot Edge Emitting Laser (FP)
• Distributed Feedback Laser (DFB)
FP and DFB Lasers for link distances > 1 km
VCSELs for link distances < 300 m

6. The Fiber Optic Link
• Optical / Electrical Signals are specified defined Test Points (TP)
• Electrical Test Points:
TP0: SERDES / ASIC output at package
TP1: SERDES / ASIC output at input of FO module electrical connector
TP1a: SERDES / ASIC output at output of FO module electrical connector
TP4a: FO module electrical output at package
TP4: FO module electrical output at output of FO module electrical connector
TP5: SERDES / ASIC input at package
• Optical Test Points:
TP2: FO module optical output after ~1meter fiber patch cord
TP3: FO module optical output after propagation over X meters optical fiber
Fiber
Optic
TX
Fiber
Optic
RX

7. The Fiber Optic Link
• Rise / Fall Time (20% to 80%)
• Timing Jitter
• DJ, RJ, TJ
• J2, J9
• Amplitude
Example of electrical eye mask taken from 100GBASE-SR10 IEEE
802.3ba specification
• Electrical Eye Mask
Fiber
Optic
TX
Fiber
Optic
RX

8. The Fiber Optic Link
• Optical Modulation Amplitude (OMA)
• Average Optical Power
• Extinction Ratio
• Timing Jitter
• DJ, RJ, TJ
• J2, J9
Example of optical eye mask taken from 100GBASE-SR10 IEEE
802.3ba specification
• Optical Eye Mask
Fiber
Optic
TX
Fiber
Optic
RX

9. The Fiber Optic Link
• TP3 is typically specified with respect to the FO RX performance
• RX center of the eye sensitivity with ideal TX source
• Optical power required to achieve 1e-12 bit error rate
• RX stressed sensitivity
•TX source is distorted to simulate propagation through a worst case optical fiber
Fiber
Optic
TX
Fiber
Optic
RX

10. The Fiber Optic Link
• Rise / Fall Time (20% to 80%)
• Timing Jitter
• DJ, RJ, TJ
• J2, J9
• Amplitude
Example of electrical eye mask taken from 100GBASE-SR10 IEEE
802.3ba specification
Fiber
Optic
TX
Fiber
Optic
RX
• Electrical Eye Mask

11. The Fiber Optic Link
Agilent BERT
Agilent DCA-X with
Precision Waveform
Analyzer
QSFP+ TX QSFP+ RX100m Fiber
TP1 TP1a TP2
TP4

12. 100 Gb/s Multimode Links in the Network
Typical Data Center Network Architecture

13. 100 Gb/s Multimode Links in the Network
Typically passive or
active copper cable
(1Gb/s-10 Gb/s)

14. 100 Gb/s Multimode Links in the Network
40 Gb/s multimode
parallel optical links
moving to 100 Gb/s
4 x 10 Gb/s
10 x 10 Gb/s

15. 100 Gb/s Multimode Links in the Network
100 Gb/s optical links

16. 100 Gb/s Multimode Links in the Network
• Standards define both the high level communication protocol and the low level physical
implementation
• Examples of major standards that support multimode parallel optical links at or above 100
Gb/s
100GBASE-SR10
10 lanes @ 10.3125 Gb/s
Generation 3
16 lanes @ ~8 Gb/s
Quad Data Rate (QDR)
12 lanes @ 10 Gb/s

17. • Addresses the needs of computing, network aggregation and core networking applications
• Common architecture for both 40 Gb/s and 100 Gb/s Ethernet
• Uses IEEE 802.3 Ethenet MAC and frame format
• The architecture is flexible and scalable
• Leverages existing 10 Gb/s technology where possible
• Defines physical layer technologies for backplane, copper cable assembly and optical fiber
medium
100 Gb/s Multimode Links in the Network
40G / 100G Ethernet

18. Link Distance Limiting Factors
Optical Attenuation:
• Reduces the amplitude of the signal at
the receiver
Causes include:
• Absorption
• Scattering
• Micro and Macro bending
Wavelength Dependant
• Typical losses of <3.5db/km for 850nm
• Typical losses of <1db/km for 1300nm
• Typical losses of <0.5db/km for 1550nm
* Attenuation is independent of data rate
Typical 62.5um Fiber Attenuation vs. Wavelength

19. Link Distance Limiting Factors
Modal Dispersion:
• Dominates in MM fiber links
• Multiple propagation Modes
• Different propagation lengths for each
mode
• Creates pulse spreading in time

20. Link Distance Limiting Factors
Chromatic Dispersion:
• Dominates in long SM links
• Distribution of optical power with
wavelength
• Speed of light in glass is wavelength
dependent
• Creates pulse spreading in time

21. Link Distance Limiting Factors
•Inter-symbol Interference (ISI)
due to dispersion results in the
largest power penalty at the
receiving end of the fiber optic
link
•ISI can be reduced by
• Using higher bandwidth
optical fiber
• Laser pre-emphasis
• Receiver equalization

22. Link Distance: Need to Extend
•As Data Centers continue to
grow in scale, switch to switch
link distance will exceed 100
meters
•There is a strong desire to
continue using 100 Gb/s
capable multimode parallel
optic modules over these
longer link distances.
Next Generation Mega Data Center
Image from IEEE Spectrum Magazine

23. Test Module
• Mid-Board mounted (embedded) parallel optics
• Separate Transmitter and Receiver Modules
• 12 Channels of unidirectional high-speed data
• Maximum data rate per channel: 10.3125 Gb/s
• Each module includes comprehensive
diagnostic monitoring features
• Optical Connectivity through a PRIZMTM Snap-
On optical connector and 12 fiber round or flat
cable
• High Density Electrical MegArrayTM connector
9x9 (81 pin) Electrical connector (22 mm x 18.5
mm)

24. Transmitter Module Test Setup
Transmitter
Test Parameter Unit VCC Temperature Rate (Gbps) Pattern
Spectral Width nm 3.3V +/- 5% 0C, 25C, 75C 10.3125 PRBS-31
Optical Modulation Amplitude uW 3.3V +/- 5% 0C, 25C, 75C 10.3125 K28.7
VECP dB 3.3V +/- 5% 0C, 25C, 75C 10.3125 PRBS-31
Mask Margin % 3.3V +/- 5% 0C, 25C, 75C 10.3125 PRBS-31
Jitter mUI 3.3V +/- 5% 0C, 25C, 75C 10.3125 PRBS-15
Sample size is 20 pieces (120 channels) unless otherwise noted in the report.
Jitter UI
TP1
J2 0.17
J9 0.29
Worst case TP1a

25. • These test results show the average Spectral Width is ~0.4 nm with a 3σ limit of less
than 0.6 nm. The IEEE 802.3ba 100GBASE-SR10 standard limit for the transmitter
spectral width is 0.65 nm.
Transmitter Test Results: Spectral Width (SW)

26. • These test results show the average Mask Margin degradation between TP2 and TP3
due to the fiber is less than 10% with a maximum difference of 21%.
Transmitter Test Results: Mask Margin (MM)

27. • The data shows a liner trend of increasing mask margin delta versus spectral width as
expected. The rate is ~2.2% per 0.1 nm increase. This result agrees with the previous
measurement of an average Mass Margin decrease of 10% with the given spectral width
distribution
Transmitter Test Results: Mask Margin vs. Spectral Width

28. • The test results show an increase in the average VECP when moving from TP2 to TP3.
The average increase is less than 0.6 dB with a high limit of 1.7 dB
Transmitter Test Results: Vertical Eye Closure Penalty (VECP)

29. • These test results show the average Optical Modulation Amplitude difference is less
than 0.8 dB with a maximum delta of 1 dB
Transmitter Test Results: OMA difference (at TP2 and TP3)

30. • The increase in jitter of 30-50
mUI due to the 300m of fiber
does not appear to be
significant.
Transmitter Test Results: Jitter

31. Receiver Module Test Setup
Receiver
Test Parameter Unit VCC Temperature Rate (Gbps) Pattern
Stressed Receiver Sensitivity dBm OMA 3.3V +/- 5% 0C, 25C, 75C 8.5, 4.25 PRBS-31
Receiver Output Jitter UI 3.3V +/- 5% 0C, 25C, 75C 8.5, 4.25 PRBS-15
Mask Margin % 3.3V +/- 5% 0C, 25C, 75C 8.5, 4.25 PRBS-31
Sample size is 20 pieces (80 channels tested) unless otherwise noted in the report.
Jitter UI
TP1
J2 0.17
J9 0.29
Worst case TP1a
To test Interoperability with 10GBASE-SR transceivers, a 10GBASE-SR SFP+ module was
modified to produce optical signal with a VECP of 3.5 dB with -3.2 dB OMA

32. • With positive margin, these test results verify that the Parallel receiver, meets the
IEEE802.3ba TP4 mask requirement over 300m of worst case OM3 fiber using either a
worst case Parallel or worst case 10GBASE-SR SFP+ transmitter
Receiver Test Results: TP4 Mask Margin

33. • These test results verify that the Parallel receiver, meets the IEEE802.3ba TP4 Total jitter
specification over 300m of worst case OM3 fiber using either a worst case Parallel or
worst case 10GBASE-SR SFP+ transmitter.
Receiver Test Results: TP4 Total Jitter

34. • These test results verify that the
Parallel receiver, meets the
IEEE802.3ba TP4 jitter
specification over 300m of worst
case OM3 fiber using a worst
case Parallel or worst case
10GBASE-SR SFP+ transmitter
Receiver Test Results: TP4 J2/J9 Jitter
Jitter UI
TP4
J2 0.42
J9 0.65
Max TP4 Jitter

35. 2000 MHz.Km
Receiver Test Results: Stressed Receiver Sensitivity Test
• Measurements were performed while varying case
temperature from 0C to 75C using a PRBS31 test
pattern.

36. • These receiver sensitivity results show significant margin to the IEEE802.3ba SRS limit
of -5.4 dBm
Receiver Test Results: Stressed Receiver Sensitivity

37. Conslusions
•As modern data centers continue to grow in physical size, there is a strong desire
to continue to use lower cost VCSEL based parallel optic modules in longer distance
100 Gb/s interconnect applications.
• While the current 100GBASE-SR10 Ethernet standard specifies a link distance of
only 100m over OM3 fiber, we show that certain commercially available 100GBASE-
SR10 VCSEL based parallel optic modules can successfully operate over 300m of
worst case specified OM3 fiber without a significant degradation in transmitter or
receiver performance.
• Furthermore, we show that these parallel optic modules can inter-operate with
single channel small form pluggable (SFP+) transceiver modules in 100GBE to 10x
10GBE break out applications with link distances up to 300m over OM3 fiber.

38. Thank You