qa for fibre bundling

28 October 2004 Brunel QA for the Fibre Tracker

QA for fibre bundling

Dr Paul Kyberd and Dr Peter HobsonSchool of Engineering & DesignBrunel University, UK


SummaryPropose a non-destructive method to check that the fibres have been correctly bundled into groups of 7.

To assist with QA of fibres once in connectors (breaks, relative light yield)

To design, construct, deliver and maintain a precision optical assembly, 400 mm travel precision stage and associated computer control system for QA laboratory.


Overall system concept

Precision illumination to excite only the bundle of 7 fibres OR

System to illuminate two bundles of 7 either side of the desired “dark” bundle– Fits better with the symmetry of the problem

– May be easier to arrange

– Step through all the groups of 7 to aid in assembly of fibres into ferrules.

Can use the same system afterwards to check that there are no significant breaks in the fibres.

Use a video camera to aid in the original alignment of the illuminator with respect to a datum on the plane.


Scanning Light source

Excite the 3HF fluorescence with light around 390 nm.

Use low average power to preserve fibre secondary fluorescence (pulse the light source?).

Excite group of 7 fibres (3+4 in the two planes) then step on to next 7 etc.

Still at the concept stage, but simulations underway, and experimental tests on fibres now underway (October 2004).


Simulations – convergent beam

True 3D simulation (non-sequential).

Includes ray splitting, polarisation, scatter and absorption effects.

Horizontal lines through fibres on this view are “detector” planes to measure the energy passing through the mid-planes of the fibres.

Cuboid volume represents the inter-plane glue.

Virtual source


Simulations – convergent beam

Power crossing the midline of the upper 4 fibres. Energy in gaps doesn’t excite these fibres (but does excite the 3 fibres in the bottom row)

A lot of optimising to do to get the best discrimination for the lower row and to understand what sort of illumination would be best (e.g. narrower but more collimated etc.)

Fibre

Gap


Simulations – collimated beam

Power crossing the midline of the upper 4 fibres, with ~collimated illumination.

Basic simulation principle developed and it doesn’t seem to be a priori impossible.

Upper 4

Lower 3 Light inside fibre


Programme of work 1

Test basic principle in Brunel laser laboratory with non-critical lengths of fibre.

Check fibres for any induced change of properties.


Recent “proof-of-principle”

This October we have made some rather simple tests to see if this technique is viable.

We have evaluated a number of violet and near-UV LED sources.– Violet (peak emission around 400 nm) are not

useful.

– Near-UV (around 370 nm) can excite green fluorescence strongly.


Fibre plane tests

Imperial College have recently lent us an old fibre plane for tests.

We have demonstrated that one can excite single fibres, or groups reasonably easily.

Green fluorescence is easily seen even with fairly low levels of excitation light.


Glows in the dark

Many fibres illuminated at once. Red background is from the laboratory “safe” light

Using a simple mask one fibre can be strongly excited (plus a few others very weakly, here seen in blue)


Programme of work 2

Design optical illumination system and prototype

Purchase 400 mm travel precision stage – absolute accuracy ~ 10 µm– precision ~ 1 µm

Design and implement LabView DAQ system.


Stage specification

Travel Range (mm) 400

Resolution (µm) 0.1

Minimum Incremental Motion (µm) 0.1

Bi-directional Repeatability (µm) 0.2 typical

Absolute Accuracy ±1.25 µm per 100 mm, typical

Speed Range 0.01 µm/s to 100 mm/s

Speed Regulation ±1% RMS typical above 10 µm/s

Acceleration Range (g) 0.001–0.25

Normal Load Capacity (N) 680

Straightness/Flatness (over center 80% travel) (µm) 4.0


Programme of work 3

Commission final system at BrunelDeliver working system to Imperial CollegeProvide calibration, documentation,

support, maintenance and repair during the fibre-plane assembly phase of the project.


Resources

Dedicated technician support for construction, commissioning and maintenance (~ 0.5 FTE per year for two years)

Precision stage and control computer– On loan to MICE UK– No cost to MICE UK

Specific equipment, e.g. light source, optics etc. are a small call on the MICE UK equipment budget.

qa for fibre bundling

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