Cartridge Fiber Reach Limits

Sloan Digital Sky Survey Telescope Technical Note 20020212

Larry Carey

Each spectrographic cartridge consists of 32 fiber bundles, with 20 fibers per bundle. Each bundle of fibers is clamped below the plate (in sky orientation) by an aluminum anchor block. The fiber emerges from this anchor block with heavy jacketing and is terminated with a precision ferrule which is plugged into a hole on the plate. The reach of a fiber is determined by the point at which it emerges from the anchor block.

In the fall of 2001 the fiber reach of the science and guide fibers in a typical spectrographic cartridge was measured by Russell Owen and Larry Carey. The measurement method consisted of the following steps:

1: Fix the test cartridge in the plugging station in preperation for plugging.

2: Place a sheet of paper directly on the surface of the plate to be plugged.

3: Select a representative fiber and hold it with thumb and index finger, approximately 1" above the ferrule.

4: Mark the paper to document the limits of free (ie. non-stressed) motion of the fiber in all directions with the ferrule oriented vertically, and held as described above.

5: Using a plumb-bob, mark the paper directly below the location where the fiber emerges from its clamp.

Using this technique to measure several fibers, we deteremined that each fiber can reliably reach holes within a circle of radius 7" centered at a point 1.5" beyond where the jacketed fiber emerges from the anchor block.

For a plate to be pluggable, each fiber must have a free hole available within its unique 7" radius circle.

Date Created: 02/12/2002