Long Length Fiberoptic Cables

By on February 5, 2020 in 90° Probes, Displacement Sensor, Fiber Optic Vacuum Passthru, Fiberoptic Sensors, Magnetic Fields, Non-Contact Sensing, Quartz Fibers

PROBLEM
Quartz fibers have excellent transmission over long lengths, but they are very expensive and usually cost prohibitive. A recent customer asked for a model D171 sensor with 45 meter length for displacement measurements in vacuum and high magnetic field.

SOLUTION
A 3-piece cost saving system was devised where only nineteen 200µm quartz fibers were used to illuminate 10% of the model D171 probe area.
Part A – Two Ø 1000 µm Hard Clad Silica Fibers, 20 m long in air
Part B – Two Ø 1000 µm Bundles of Ø 200µm Silica/Silica (Quartz) Fibers, 24.5m long in vacuum
Part C – Ø 4320 µm D171 Glass Fibers, 0.5 m long in Vacuum

Part A has two Ø1000µm fibers at the connector interface:

1000 µm HCS Fiber

Part B Ø1000 µm fiber bundles each have 19 fibers at the connector interface:

one transmits light and one returns reflected light.

Part B transmit fibers were randomly mixed with Part C glass fibers. Although Part B fibers illuminated just 10% of Part C fibers, this D171 sensor calibrated to an acceptable 70 mm displacement range. And therefore, the system cost was much lower than it would otherwise have been if all of the D171 fibers had been illuminated by quartz fibers.

Model D171 has several thousand 50µm glass fibers in a 4320µm diameter bundle.

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