Safety concerns - Heating PMMA (acrylic glass) and fluorinated polymers
One problem is bonding of the bundle.  The contact surface is the fluororesin cladding that allows more nearly perpendicular rays to be totally internally reflected.  If you nick the cladding you get a light leak.  Will the cladding fuse when heated?

If you ligthly bond a bunch of cylinders you get air gaps where they touch.  Those will be a triangular grid off dark spots, 9.3% of the area of the image.

http://en.wikipedia.org/wiki/Circle_packing