Lumitex uses sheets of UniGlo Fiber Optic Cloth cut into specific sizes and shapes to create a thin flexible lighting layer that goes between the overlay and the dome switches.  The product is typically 0.013" (0.33mm) thick and anywhere from 1 sq inch to over 100 sq inches.

The optical fibers coming off one end of the panel are bundled into a circular ferrule and coupled to one or more LED light sources.

Lumitex Fiber Optic Membrane Switch backlighting provides long life, low power, inert, maintenance free backlighting for all membrane switch, overlay, label, keypad and keyboard designs.

Longer Life - Durable fiber optic panel never needs replacement. Remote light source offers 20,000 to 100,000 hours life and easy replacement.

Lower Power - Sources require less power than EL, or LED Array and no inverter.  As low as 5-20mA at 2-4vdc
 
Compact Size - Panels are thin and sources are smaller than EL inverters.
 
Heat/EMI Free - Fiber optic panel adds no heat or EMI to interfere with switch operation
 
Durable - UniGlo has been tested in Membrane Switch applications for over 5,000,000 cycles.  Optical Fibers are not affected by extremes in humidity (0% to 100%) and temperature (-40 to +80 deg C)

Very Low Startup Costs - Minimal Engineering charge and usually no tooling.  Low prototyping cost with no minimums.
 
Design Flexibility - Fiber Optic technology allows designers to solve unique problems.
 
Thin, Low Profile - Typical construction is 0.013 inches thick (0.33 mm).  Thinner constructions are available.
 
Reduced Assembly and Maintenance - Simply apply panel in between dome switches and overlay.  Fiber Optic panel doesn't need replacing, long life light sources are easily replaceable.
 
Additional Information:
Membrane Switch Backlighting User's Guide

Membrane Switch Backlighting Application Pictures
Membrane Switch Backlighting FAQ’s

Technologies – UniGlo Fiber Optics