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Updates on Optical Projects June, 2011
B. Fernando, P.M. DeLurgio, R. Stanek, B. Salvachua, D. Underwood ANL-HEP
D. Lopez ANL Center for Nanoscale Materials
April 10, 2023 1
Motivation• Develop and adapt new technologies to improve
optical communication in HEP experiments– Increase speed, reduce the mass of the system, Increase
reliability
• Test operation of new devices with the environmental conditions of – Radiation hardness, low temperature operation, Reliability
• Introduce the technologies to real detectors• Investigate techniques to eliminate fibers, cables
and connectorsApril 10, 2023 2
Issues with Current HEP Optical Links• Most LHC optical link failures are due to VCSEL failures and
broken solder joints – More spare links (?)
• VCSELs need– High current driver chips (radiation hard) which need a lot of power
and control wires– Power cables (to supply current)– Need to tune links individually (need control wires) – Cooling/Heating
• ESD/moisture sensitivity– Issue with custom packaging (non industry)
• High current density • Radiation tolerance
– Commercial VCSEL's have only limited radiation tolerance, which is probably not adequate
IncreaseAmount of material inside detector
3
Reliability issues
Proposed Optical Scheme (ideal)
April 10, 2023 4
PowerOn detector (n=12?)Outside (counting room)
Fibers /free space links
CW laser Fibers
Single chip
Modulator*n
PIN diode*nData, TTCTIA
AMP
Single chip (possibility in future)
Modulator*n
PIN diode*n TIA*n
AMP*n Control Chip /sensors
High bandwidth: no chirp commercial systems work >10 Gb/s/channel
Low material budget : Less total power inside detector less cooling needed (stainless steel/copper) Fewer control wires
Higher reliability: Laser sources outside the detector, Don’t need separate high current drivers, less radiation/ESD/humidity sensitivity
Smaller in size Modulators/PIN diodes can be integrated into a single die
n
n
Detector Applications: Requirements• Calorimeters (Tile, Liquid Argon):
– Highly serialized data fast (8-10 Gb/s links)– Less radiation ( ~1013 Protons/cm2 )– Standard interface with industry standards (snap 12?) – Reliability is an issue because there can be no access for years
• Tracker(pixel detector, silicon tracker)– More data fast (atlas pixel: 5Gb/s out)– High radiation (~1015 Protons/cm2 ) – Low temperature operation (~-20 C )– Reliable (no access after the detector closed)– Low power consumption (VCSEL based ~40mW/channel)– Less mass (material inside)– Custom interface (LVDS input)
5
MODULATORSTechnologies
April 10, 2023 6
7
on
off
a-Si GeSi a-Si
a-Si GeSi a-Si
Tapered vertical coupler
MIT Design of GeSi EAM Device Structure
Liu et al, Opt. Express. 15, 623-628 (2007)
MIT Modulators
7
• Fabricated with 180 nm CMOS technology• Small footprint (30 µm2)• Extinction ratio: 11 dB @ 1536 nm; 8 dB at 1550 nm• Operation spectrum range 1539-1553 nm (half of the C-band)• Ultra-low energy consumption (50 fJ/bit, or 50 µW at 1Gb/s)• GHz bandwidth• 3V p-p AC, 6 V bias• Same process used to make a photodetector
8
41 mW at 5 Gb/sec
100 u long x 10 u wide
Thin, order u
Broad spectrum 7.3 nm at 1550
80 u long delay line internal
1V p-p AC, 1.6V bias
8
IBM Modulators
9
Advances are Needed in Procuring Modulators ANL Bench tests use LiNO3 modulators – fast, rad hard, but not small MIT and IBM have prototypes of modulators to be made inside CMOS chips
It would cost us several x $100k for 2 foundry runs to make these for ourselves Currently both designs are not being actively pursued
We may have found a vendor (Jenoptik) for small modulators who will work with us on ones which can be wire-bonded and have single-mode fiber connections Need to test for radiation hardness of these
There are commercial transceiver of small size such as LUX5010A (http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4528356&tag=1) Fit most of the requirements, need to find out radiation hardness and low
temperature operation9
Collaboration with industry
• Testing radiation hardness of commercial modulators
• Design and construct a radiation-hard silicon modulator chip
• Building a transceiver• Communication within different layers to
improve the trigger efficiency
April 10, 2023 10
The Luxtera/Molex Commercial Devices
Good Unknown
Fast (4x 10G) Radiation hardness
Design is very close to our ideal design Low temperature operation
Fibers are pure glass, no plastic inside
No need of connectors, drivers pin diodes, etc.
Very small
11
The Luxtera/Molex design [link]
12
Testing Plan for (Jenoptik/Molex) • Test the operation at -20C• Few Total Ionizing Dose (TID) testing rounds at
ANL with electrons– Test unmodified devices first.– Can give some feedback and If request for
modifications to standard device is accepted these also to be tested
– Test using 200 MeV protons up to 1015 Protons/cm2 – Couple of batches (improve/unmodified..etc)
13
FUTURE
14
Future Directions Test radiation hardness and low temperature operation of
Commercial modulators and improve it for HEP optical links Build HEP modulators if funding obtained (collaboration with
industry ) More robust long distance optical link Local triggering using optical communication between tracking
layers
15
Some concepts for interlayer communication for input to trigger decisions
Backup
April 10, 2023 16
Optical links failures at LHCVCSEL failures in ATLAS before beam
http://www.sciencedirect.com/science/article/pii/S0168900208010474VCSEL failures meeting https://indico.cern.ch/getFile.py/access?
contribId=8&resId=0&materialId=slides&confId=103879 ACES meeting on optical links
https://www.ncc.unesp.br/its/attachments/download/119/OptoWG_ACES2011.pdf shows few failures in CMS
TWEPP 2010 CMS operations "We continue to have failures of the optical links" (off detector)https://wiki.lepp.cornell.edu/lepp/pub/People/AndersRyd/100924_TWEPP.pdfLHCB VCSEL failures https://indico.cern.ch/getFile.py/access?
contribId=3&sessionId=0&resId=1&materialId=slides&confId=126772CERN Twiki on VCSEL failures (TT and IT ) https://lbtwiki.cern.ch/bin/view/ST/VCSELs
17
BEAMS IN AIRTechnologies
April 10, 2023 18
19
Technology : Free-Space Communication to replace fibers and cables
• Advantages:
– Low Mass
– No fiber routing
– Low latency (No velocity factor)
– Low delay drift (No thermal effects such as in fibers)
– Work over distances from few mm (internal triggers) to ~Km
(counting house) or far ( to satellite orbit)
– Communicate between ID layers for trigger decisions.
19
Main Parts of Project1. Design of lens systems to send and receive
modulated laser light through free space. 2. Incorporate modulators to modulate the laser beam3. Use MEMS mirror to guide the beam to the receiver
and the use of a feedback mechanism to keep the beam locked to the receiver.
4. Setup for bit error rate testing5. Demonstrate practical application, e.g. ANL DHCAL at
Fermilab (this application not yet funded)
April 10, 2023 20
21
The commercial MEMS mirrors have ~40 dB resonance peaks at 1 and 3 KHz.
To use the direct feedback, developed an inverse Chebyshev filter which has a notch at 1 kHz, and appropriate phase characteristics (Left Figure)
With the filter we were able to make the beam follow a reflecting lens target within about 10 μm when the target moved about 1 mm (Right Figure).
Still has some fundamental issues at large excursion (~1 cm)
A separate feedback link solves this issue
The amplitude-frequency map of our analog feedback loop, demonstrating phase stability at 100 Hz.
A test setup used to demonstrate MEMS mirror steering with an analog control loop which compensates for the mirror resonances at 1 and 3 KHz.
21
Studies of Direct Feedback Concept
Feedback from Reflections• A quadrant detector is used to find the position of the
receiver– Is it possible to find the absolute position of the
receiver? – Effects of:
• Size of the beam spot at detectors• Surface radius of the reflecting lens (hard to find many lenses)• Size of the reflecting lens• Distance between the detectors
April 10, 2023 22
Different issues we understood and later fixed
Beam too small Detector too small
After Quadrant Detector and Alignment Beam Fixed • Quadrant detectors are now designed for optimum sensor
separation– Limited working range is due to the size of the reflecting lens
April 10, 2023 23
x y
This is better since the x-y correlations are insignificant and most of the part is it linear.
Different Feedback Mechanisms
April 10, 2023 24
Distance in X (mm)Distance in Y(mm)Distance in X (mm)
Dis
tanc
e in
Y(m
m)
Implemented few feedback systems to study the capture efficiency. In order to understand the efficiency we measured the captured optical power
transmitter
receiverMEMS(fixed)
No feedback: receiving lens was moved (simple x-y translation) and power measured and fit the distribution to a 2D Gaussian
FWHM: 1.33 mm
Different Feedback Mechanisms (2)
April 10, 2023 25
Simple feedback: Here, the feedback from the quadrant detector, with an X and Y analog calculator, is used to move the MEMS mirror so that the reflected beam is again centered on the quadrant detector while the receiving lens is translated.
transmitter
receiverMEMS(moving)
feedback
FWHM: 4.3 mrad
reflector
Different Feedback Mechanisms (3)
April 10, 2023 26
Power feedback: Quadrant detector not used. Here, the feedback from the captured power is used to move the MEMS mirror so that the beam gives maximum receiver power while the receiving lens is translated.
transmitter
receiver
MEMS(moving)
feedback
FWHM: ~20 mrad
Different Feedback Mechanisms (4)
April 10, 2023 27
• Mapped feedbacks : The quadrant detector (QD) response is mapped to movement of the receiver in an initial alignment phase. The initial alignment done
transmitter
receiver
MEMS(moving)
feedbackfeedback
FWHM: ~10 mrad FWHM: ~9.5 mrad
1. With power feedback and used a fit2. Alignment link separately which fill a Look
Up Table (LUT)
12
28
Our Current Version
28
CW LASER1550 nm
optical electricADC TIA
DAC
SPI
SPI
X
Y
X
YAmpMEMS Mirrorto steer
Small Prism
850 nm LASER For alignment
ReflectionReflective lens
Rigid Coupling
GRIN lens to Capture
wires
wires
1550 LASER Beam
Modulator
Asphere Lensto launch
Si Detectors
This Assembly moves
SFP
FPGA Bit Error Tester
FPGAFPGA
Lookup table
Lookup table
Digital filter
Digital filter
29
RECEIVER
Digital Processing MEMS Steering Setup
Reflecting Lens
GRIN LENS
To Fiber
FPGA Pseudo Random Data, Bit Error Rate
Standard Fiber Receiver
Modulator
Launch Lens
MEMS Mirror Quad
Detector and Steering Laser
29
30
The figures show a 3D finite element analysis of the MEMS designed. The upper panel shows the top view of the mirror and the bottom panel a bottom view.
Argonne Center for NanoScale Materials, CNM, has designed and simulated novel MEMS mirrors that should solve the problems of commercial mirrors
The mirror is supported laterally and it can be actuated using 4 torsional actuators located in the vicinity.
More stable mirror with better mechanical noise rejection.
Under fabrication and we expect to have them available for testing very soon.
Technology : Argonne MEMS Mirrors
30
Accomplishments in Beams in Air
• Steering using reflections from the receiver system, without wires. We made a major improvement by separating data link and the alignment link.
• Found ways to form beams and receive beams that reduce critical alignments, reducing time and money for setup.
• 1.25 Gb/s over 1550 nm in air, using a modulator to impose data, and FPGA to check for errors, <10-14 error rate, with target moving about 1 cm x 1 cm at 1 m.
• Control of MEMS mirror which has high Q resonance (using both Analog and Digital filter)
April 10, 2023 31
LONG DISTANCES Applications
32
33
1 Gb/s over 80 Meters
Long Range Free-Space Communication Telescope
33
Building a fast small distance positioner for the receiver with tiny servos
34
Technology : MEMS Mirrors
34
The Lucent Lambda Router:A commercially available MEMS mirror (Developed at ARI, Berkeley)
• Studied in detail the properties of asphere and GRIN lenses to find the best option to send/receive the laser beam in air• Transmitter on MEMS mirror (Data Laser)
• We knew that aspheres can produce the best beam to transmit but aspheres have very restricted acceptance angle. Important for capture lens.
The Lens System(s)
April 10, 2023 35
Asphere Lens Type Beam FWHM (mm) at 1m Beam Peak Power at 1m(uW/(0.2 x 0.2) mm2)
Short (EFL=6.24mm) 1.00 96.51
Medium (EFL=11 mm) 1.68 39.22
Long (EFL=15.3 mm) 2.26 22.60
Lens Types Beam FWHM (mrad) at 1m Total Captured Peak Power (μW)θ φ
Short Asphere (EFL=6.24mm) 1.64 1.73 179.7
Long Asphere (EFL=15.3 mm) 2.09 1.82 198.4
GRIN with SM 2.66 2.81 48.9
GRIN with MM 20.34 18.60 85.11
36
Beams in Air: Size vs DistanceDue to diffraction, there is an optimum diameter for a beam for a given
distance in order to reduce 1/r2 losses
The Rayleigh distance acts much like Beta-Star in accelerators – Relates waist size and divergence– Depends on wavelength
If we start with a diameter too small for the distance of interest, the beam will diverge, and will become 1/r2 at the receiver, and we will have large losses (We can still focus what we get to a small device like an APD or PIN diode ). This is typical of space, Satellite, etc. applications.
If we start with an optimum diameter, the waist can be near the receiver, and we can capture almost all the light and focus it to a small spot
Examples, ~ 1 mm for 1 m, ~ 50 mm for 1 Km
Bit Error Tester
• FPGA based bit error tester that can be customized for – line rate, datapath width, TX pre-emphasis and post-emphasis, TX
differential swing, RX equalization– Different patterns PRBS 7-bit, PRBS 15-bit, PRBS 23-bit, PRBS31-bit,
user defined.
April 10, 2023 37
• Control through the computer to sweep , TX pre-emphasis and post-emphasis, TX differential swing, RX equalization, Rx sampling point to optimize the error free region