Lumiloop LSProbe 1.2 Installation and operating instructions
Application Note 4,
Reliable Operation of LSProbe 1.2
Laser-Powered Electric-Field Probes
November 23, 2020
Contents
1 Introduction 2
2 Fiber Failure Mechanism 3
3 Sacrificial Cable Kits for LSProbe 1.2 Field Probe Systems 4
4 Fiber Connector Cleaning Instructions 6
5 Replacing Sacrificial Cables 8
6 Fiber Handling Recommendations 9
Application Note 4 Reliable Operation of LSProbe 1.2 Field Probes
1 Introduction
Electric-field probes fall into one of two categories – battery-powered and laser-powered.
Laser-powered probes offer the significant advantage of unlimited continuous operation.
They save both time and effort for recharging or exchanging batteries or field probes.
However, most laser-powered field probes face a common issue. Contamination of the fiber
connector end-faces can result in burn-in defects and thus system failures. Fig. 1 shows the
end-faces of a clean, a contaminated and a defective (burned-in) fiber connector.
clean
Core
62.5 µm
Cladding
125 µm
contaminated
defecve
(burned-in)
Figure 1: End-faces of optical fiber connector, viewed through fiber microscope
To mitigate this issue and enable reliable operation, LUMILOOP has developed sacrificial
cable kits that are included in every LSProbe 1.2 Field Probe delivery.
The sacrificial cable kits operate as connector savers for the FC/ST connectors of Field
Probe, Computer Interface and extension cable. They provide two defined and convenient
points for disconnecting the Field Probe from the Computer Interface using the E2000 con-
nectors of the sacrificial cable kits.
Due to the integrated shutters, burn-in defects at the E2000 connectors are significantly
less frequent. However, in the case of a burn-in defect at an E2000 connector, the sacrificial
cable kit can easily be replaced with a spare kit. That means, the system is quickly ready
for use again. A spare sacrificial cable kit is provided with each LSProbe 1.2 Field Probe.
To avoid further progression of burn-in defects, the complete kit including both sacrificial
cables and the E2000 coupler shall always be replaced.
This document gives detailed instructions on operating laser-powered field probes both
reliably and effortlessly, it contains four more sections:
• Section 2, page 3, the mechanism of fiber failures,
• Section 3, page 4, purpose and application of sacrificial cables kits,
• Section 4, page 6, fiber connector cleaning instructions,
• Section 5, page 8, replacement of sacrificial cable kits,
• Section 6, page 9, fiber handling recommendations.
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Application Note 4 Reliable Operation of LSProbe 1.2 Field Probes
2 Fiber Failure Mechanism
LUMILOOP’s statistics show that more than three quarters of the field probes that are
turned-in for analysis have fiber issues caused by improper handling.
For transparency, LUMILOOP creates a detailed report for every returned field probe, con-
taining failure analysis and corrective measures. Fig. 2 shows images taken out of a typical
repair report. In the shown case, the user had plugged the optical fibers frequently without
cleaning. Additionally, the sacrificial cables had been removed by mistake. Consequently,
both faces of an FC fiber connector pair, which carries the optical power for the field probe,
suffered a burn-in defect.
(a) Field Probe - FC before / after cleaning (b) Field Probe - ST before / after cleaning
(c) Extension cable - FC before / after cleaning (d) Extension cable - ST before / after cleaning
Figure 2: Example for contaminated FC (power) and ST (data) fiber connectors
As suggested by the name, burn-in defects are caused by excessive heating, leading to crack-
ing and/or melting of the fiber core where two fibers interface. A sound optical fiber inter-
face introduces less than 0.5 dB of attenuation. Contamination, e.g. by dust particles, will
result in a higher attenuation, and thus a significant fraction of the optical power to be
converted into heat.
= x 1000
Figure 3: Power density comparison: 1 Watt fiber core vs. 1 Kilowatt hot plate
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Application Note 4 Reliable Operation of LSProbe 1.2 Field Probes
LSProbe 1.2 field probe systems can launch up to 1 Watts of optical power into a 62.5 µm
optical fiber core. The resulting power density is more than a thousand times greater than
that of a typical hot plate.
3 Sacrificial Cable Kits for LSProbe 1.2 Field Probe Systems
The LSProbe 1.2 Field Probe System consists of a Field Probe and a Computer Interface,
connected by duplex fiber optic cables. Any Field Probe can be operated by any Computer
Interface, both are identified by separate serial numbers.
Sacrificial cable kits serve as connector savers for all FC/ST connectors. Sacrificial cable kits
are easily recognizable by their blue fiber jackets. As suggested by their name, sacrificial
cable kits are meant to be sacrificed, i.e., thrown away, in the event of an fiber connector
burn-in.
In a typically busy lab environment fiber cleaning as outlined in Section 4 can be difficult
to enforce – human error can never be ruled out completely. Sacrificial cable kits introduce
an easy-to-use pair of E2000 connectors. E2000 connectors are significantly less prone to
contamination and thus to burn-in defects because of their integrated automatic shutters.
Consequently, E2000 connectors may be plugged without cleaning, consciously accepting
that contamination will accumulate with each plugging cycle and lead to a burn-in defect
eventually.
Once a burn-in defect has occurred, the complete sacrificial cable kit must be replaced, in-
cluding the E2000 coupler. Failing to replace one half of the sacrificial cable kit will inevitably
lead to the replacement cable’s burn-in.
Every LSProbe 1.2 System comes with a fiber extension cable and three sacrificial cable
kits: one connecting the Computer Interface and fiber extension cable, one connecting
fiber extension cable and Field Probe and one spare sacrificial cable kit.
ST-Coupler
FC-Coupler
E2000-Coupler
ST ST
Sacricial Cable Kit
Sacricial Cable Sacricial Cable
FC FC
ST
ST
FC FC
ST
ST
E2000 E2000
ST-Coupler
FC-Coupler
E2000E2000
Figure 4: Sacrificial cable kit, consisting of two sacrificial cables, one E2000 coupler, one FC cou-
pler and one ST coupler
The components of a connected sacrificial cable kit are shown in Fig. 4. A sacrificial cable kit
consists of a pair of short fiber cables with FC/ST connectors at one end and E2000 con-
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Application Note 4 Reliable Operation of LSProbe 1.2 Field Probes
nectors at the other end. The two sacrificial cables are connected by an E2000 coupler.
The FC/ST connectors at either end of the sacrificial cable kit connect to and protect the
FC/ST connectors of the Field Probe, the Computer Interface and the fiber extension cable.
Fig. 5 shows the fiber connections of a typical LSProbe 1.2 Field Probe System.
Figure 5: Typical LSProbe 1.2 Field Probe System with sacrificial cable kits
As highlighted in Fig. 6, the optical link should always be disconnected using E2000 connec-
tors. Do not disconnect any FC/ST connectors unless absolutely necessary. When plugging
FC/ST connectors make sure to observe the cleaning instructions in Section 4.
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Figure 6: Fiber connections of a typical LSProbe 1.2 Field Probe System
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Application Note 4 Reliable Operation of LSProbe 1.2 Field Probes
4 Fiber Connector Cleaning Instructions
There are two methods for cleaning fiber-optic connectors: dry cleaning and wet-to-dry
cleaning. Dry cleaning is suitable for minor contamination. Wet-to-dry cleaning is suitable
for severe contamination caused by skin oils, skin flakes, dust particles, etc. Therefore,
LUMILOOP recommends the wet-to-dry cleaning method, detailed in this section.
Regardless of the method, the following sequence of steps should be observed:
1. Inspect the connector end-faces for contamination using a fiber microscope. Always
ensure that the Computer Interface is switched off and cannot be turned on inad-
vertently during fiber inspection. Note that the focal plane for for E2000 and ST/FC
connectors differ and must thus be adjusted.
2. Clean the connector end-face.
3. Reinspect the connector end-face, go back to step two, if there is any contamination.
4. Connect the fiber connectors, do not put the connector down. Do not apply dust caps
between cleaning and connecting.
LUMILOOP’s cleaning kit shown in Fig. 7 includes:
• a 400x optical fiber microscope,
• two packs lint-free cassette cleaner wipes
(Chemtronics, Foccus QbE Pleaning Platform, part no. QBE),
• a fiber-optic cleaning pen
(Chemtronics, Foccus Fiber-Wash Precision Cleaner, part no. FW2170)
• an unfilled isopropyl alcohol (IPA) pipette/bottle,
• spare FC/ST dust caps and two E2000 locking caps.
Figure 7: LUMILOOP fiber-optic cleaning kit
Fig. 8 shows how to clean the fiber connectr end-faces of ST/FC and E2000 connectors.
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Application Note 4 Reliable Operation of LSProbe 1.2 Field Probes
Step 1: Only for E2000 connectors, unclip the con-
nector pair and apply an E2000 locking cap.
Step 2: Expose a fresh area of the lint-free fiber op-
tic cleaning platform.
Step 3: Moisten one corner of the cleaning wipe us-
ing the fiber-optic cleaning pen or IPA pipette.
Step 4: Press the fiber end-face flatly against the
moist area of the wipe and slide it into the dry area
of the wipe.
Step 5: Only for E2000 connectors, remove the
E2000 locking cap, re-clip the connector pair after
cleaning both connectors.
Figure 8: FC/ST/E2000 fiber-optic connector wet-to-dry cleaning method
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Application Note 4 Reliable Operation of LSProbe 1.2 Field Probes
5 Replacing Sacrificial Cables
If a burn-in defect is observed at an E2000 connector, the complete sacrificial cable kit must
be replaced. A step-by-step description of the recommended procedure is given below:
1. Preparare replacement
a) Disconnect the complete sacrificial cable kit including its E2000 coupler and dis-
pose of it to prevent mix-up of cables or couplers.
b) Unpack a spare sacrificial cable kit. Skip step 2 for originally packed cables sup-
plied by LUMILOOP.
2. Clean E2000 connectors
a) Unplug both E2000 connectors from the E2000 coupler.
b) Clean the connector pair of the first E2000 connector as described in Sec-
tion 4 (Fig. 8) and plug it into the E2000 coupler.
c) Clean and connect the second E2000 connector.
3. Clean first end of sacrificial cable kit
a) Disconnect both FC connectors from the coupler.
b) Clean the first FC connector and connect it to the coupler.
c) Clean the second FC connector and connect it to the coupler.
d) Repeat steps a) through c) for the ST connectors.
4. Repeat step three for the second end of the sacrificial cable kit.
5. Consider ordering a new spare sacrificial cable kit.
Fixing burned-in FC/ST connectors: In case of a burn-in defect at a ST or FC connector
due to improper handling, replacement is required. There are three destinct cases:
• In case of a burn-in defect at a fiber extension cable, the sacrificial cable kit and the
extension cable can be replaced with spares. Please contact LUMILOOP for support.
• In case of a burn-in defect at the Computer Interface, experienced users may remove
and replace the short orange fiber cable attached to the Computer Interface shown
in Fig. 9. Please contact LUMILOOP for detailed instructions. Computer Interfaces
without this short cable and associated cover can be refitted for improved system
reliability. For older systems the sacrificial cable is attached directly to the Computer
Interface. Please contact LUMILOOP support for more information.
• In case of a burn-in defect at the Field Probe, the system needs to be sent-in for repair.
Please contact LUMILOOP for support.
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Application Note 4 Reliable Operation of LSProbe 1.2 Field Probes
Figure 9: Rear view of Computer Interface with short fiber-optic cable fixed to its housing
6 Fiber Handling Recommendations
Observing the handling recommendations stated below will ensure the continuous, reliable
operation of the LSProbe 1.2 Field Probe System. The recommendations should be brought
to the attention of all staff operating the system. In general, always handle fiber-optic sys-
tems with care.
• Avoid bending of fiber optic cables more than the criticial radius. For the fiber-optic
cables supplied with the LSProbe 1.2 Field Probe, the critical bending radius can be
given with 60 mm for short term and 100 mm long term bending.
• Avoid tensile strain on fiber-optic cables. Fiber-optic cables shall not carry the weight
of the connectors.
• Always use two sacrificial cable kits – one between Computer Interface and extension
cable and one between extension cable and Field Probe.
• Always disconnect the optical fiber connection using the E2000 connectors of the
sacrificial cable kits.
• Do not open any FC/ST fiber connectors unless absolutely necessary.
• Cover all open fiber-optic connectors using the supplied dust caps.
• Before connecting any FC/ST connectors, e.g., when replacing a sacrificial cable kit,
clean all connectors as described in Section 4. Use a fiber microscope to ensure that
the connector end-faces are immaculate.
• When a sacrificial cable kit has burned-in at the E2000 coupler, replace the complete
sacrificial cable kit including the E2000 coupler and clean all FC/ST connectors as
described in Section 4.
November 23, 2020 Page 9/9
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