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LightABLE Production Status. ID Week May 2014. LTx Project. Aim: use commercial package for VCSEL array to improve reliability. Integration into fully backward compatible TX PCB Electrical and optical connections Space constraints. LightABLE OSA (Reflex Photonics). Production Status. - PowerPoint PPT Presentation
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Tony Weidberg 1
LightABLE Production Status
ID Week May 2014
ID Week May 2014
Tony Weidberg 2
LTx Project
• Aim: use commercial package for VCSEL array to improve reliability.
• Integration into fully backward compatible TX PCB – Electrical and optical
connections– Space constraints
ID Week May 2014
LightABLE OSA (Reflex Photonics)
Production Status
• 363 LightABLEs delivered (500 ordered).– Delivery late because of problems with the assembly
company. – Final batch now promised for end May.
• Two flavours of PCB produced and components mounted (except LightABLE).
• > 301 LTx assembled.– 101 wire bonded– 84 completed burn-in
• Production rate between 20 to 40/ week.ID Week May 2014 Tony Weidberg 3
Tony Weidberg 4
Power QA @ Oxford
• DC power only at this stage
• Problem is that LightABLE devices have large offset power and we only use modulation (ac coupled links).
• Better power QA @ Cambridge
ID Week May 2014
Tony Weidberg 5
Change after Burn-in
• Burn-in: 72 hours @ 70c and 10 mA drive current
• No large change observed.
• Need to re-measure one underflow
ID Week May 2014 Change (dB)
Tony Weidberg 6
Cambridge QA
• Based on existing system to test AC performance– Loopback test TX RX
• Measure BER and perform timing scan width of eye diagram
• Measure power while adjusting modulation amplitude – requires programming uProc on LightABLE– Trick to deal with large baseline power (resistors added
to DRX-12 to bleed current). – Work in progress …
ID Week May 2014
Tony Weidberg 7
Plans
• Complete production and QA for LTx• Develop BOC s/w to allow operation of LTx or
AOC.• Install LTx in one crate in June.• Check performance– Ipin– BER in physics mode tests
• Install LTx in more crates ?
ID Week May 2014
Tony Weidberg 8
Backup
ID Week May 2014
Tony Weidberg 9
Changes Since Design Review
• Essential: – Make it easier for Infineon SMC connector to
connect to LTx in USA15– Improve thermal management
• Highly desirable: Allow option of decreasing optical power from LTx in case of saturation for DORIC4A.
• Mechanical reliability, consider use of under-fill for LightABLE BGA.
ID Week May 2014
Tony Weidberg 10
Mechanical Changes• Make mate/demate with Infineon
SMC easier.– Shortened length of MT guide
pins.– Added groove near end that was
cut to help with gluing. End sticking out is the uncut end.
– Use long guide pins in jig during reflow. Ensures that guide pins will be in the correct location and pointing the correct way.
ID Week May 2014
Tony Weidberg 11
Underfill
• Decided against use of underfill for BGA– Mismatch in CTE.– Very little insertion force required.– 100 mate/demate cycles with monitoring of power every
10 cycles no changes– Thermal cycling: no change in power.
ID Week May 2014
Tony Weidberg 12
Cooling• Thermal path from LightABLE to front panel
via Thermal Gap Filler (3 Wm/K)• OSA analysis DT from junction to ambient
=20°C ( next slide).
ID Week May 2014
Tony Weidberg 13
OSA Analysis
• Measure Peak wavelength lp• Scan Mark: Space Ratio (MSR)
and measure lp• Plot lp versus MSR• Fit slope and extrapolate to
50%.• Use calibration dlp/dT DT• Fit Results variable in quality
but reasonable consistency
ID Week May 2014
Tony Weidberg
AtLinks LightABLE- uProc
We can use a microprocessor to drive the LightABLE Engine’s I2C inputs, and the SPI lines currently used for the MDACs can be used to drive the µProc
But the MDACS we must still give the right output current for the interface circuit• This could be done using the µProc’s SPI lines• It could be carried out when the µProc is initialised• The MDAC_CLR command (one of the BOC_SPI signals) could be
used to force a uProc initialisation
This is what it would look like:
ID Week May 2014 14
Maurice Goodrick
Tony Weidberg
AtLinks LightABLE- uProc Connections
ID Week May 2014 15
Z PCB
Maurice Goodrick
Tony Weidberg 16
QA: Optical Power
ID Week May 2014
1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 More0
5
10
15
20
25
30
35
40
45
LTx
Power (mW)
Freq
uenc
y
-2.4 -2 -1.6 -1.2 -0.8 -0.4 0 0.4 0.8 1.2 1.6 2 2.40
5
10
15
20
25
30
35
40
LTx
After - Before Burn-in (dB)
Freq
uenc
y
<Optical Power> @ 50% duty cycle,after burn-in
Change with burn-in (72 hours @70C)
Tony Weidberg 17
LTx in SR1
• LTx optical power.• No T correction• Initial decrease
~1%.– No burn-in
preformed for this array probably ok but should run longer
Steve McMahon
Opti
cal P
ower
(mV)
Time (days)ID Week May 2014
Tony Weidberg 18
Steve McMahonO
ptica
l Pow
er (m
V)
Time (days)ID Week May 2014
Tony Weidberg 19
Summary
• Improvements following design review have been implemented.
• Production well underway.• Populate one crate in USA-15 in May• Need to continue long-term optical power
monitoring in SR1 and USA-15.
ID Week May 2014
Backup Slides
ID Week May 2014 Tony Weidberg 20
Tony Weidberg 21
OSA Thermal Studies• New metalwork for front panel of BOC
– Takes heat through thermal pad metalwork outside crate• OSA measured for 12 channels from first LTx with micro on board.• OSA spectra taken at MSR settings of 0, 10, 20 and 24 (maximum
value which gave clean waveform).• Very crude peak finding
– Found lmax corresponding to maximum power
– Found l1 and l2 corresponding to peak power -3dB
– Best estimate lpeak= (l1 + l2)/2
– Used difference between lpeak and lmax as estimate of error.– Error on MSR set to 1% (guess)– Fit lpeak vs MSR next slides
ID Week May 2014
Tony Weidberg 22
Fit Results variable in quality but reasonable consistency
ID Week May 2014
Tony Weidberg 23
Check this point (see next slide)
ID Week May 2014
Tony Weidberg 24ID Week May 2014
Tony Weidberg 25
Check Channel 8 MSR=20• Spectra looks ok• Programme found reasonable results• 3 sigma effect doesn’t change conclusions
855 855.05 855.1 855.15 855.2 855.25 855.3 855.35 855.40.00E+00
5.00E-03
1.00E-02
1.50E-02
2.00E-02
2.50E-02
3.00E-02
3.50E-02
ch 8 MSR=20
ch 8 MSR=20
From programme:Max power @ 833.330 nmPeak @ 833.327 nmLooks ok?
ID Week May 2014
Tony Weidberg 26
Summary
• Fits to each channel for slope• Use Carlos’s analysis for temperature
sensitivity– dl/dT=0.0673 nm/K
• Extrapolate to 50% duty cycle• DT = 20 ± 4 C• Improved thermal performance compared
to previous study DT = 29 to 43 C. – Improved metalwork takes heat through
thermal pad to outside of crate.
channel slope
0 0.0273
1 0.0235
2 0.0242
3 0.0296
4 0.0241
5 0.0251
6 0.0260
7 0.0251
8 0.0445
9 0.0271
10 0.0280
11 0.0259
ID Week May 2014