Fiber bundles

Illustration of a single ended fiber bundle and bifurcated fiber bundle.

Illustrations of a circular, square, rectangle, fishtail, spot within circle and dual semi-circle fiber bundle.

Fiber bundles or light guides are made using small diameter glass or silica fibers typically 50-100 µm. These thin fibers are very flexible and allow large diameter fiber bundles to be fabricated with much smaller bend radii than is possible with single fibers of similar diameter. They also allow light 'splitting' where a single input can be split equally or unequally into two or more outputs.

For high performance, silica fibers of the HPSUV or HPSIR type are used. These give transmission down to 180 nm in the UV or up to 2.5 µm in the IR respectively.

For simple light transmission in the visible region, lower cost glass or polymer fibers can be used. Spectral attenuation data for these types is shown below.

Protective jackets in plastic or stainless steel can be fitted. For small diameter bundles an SMA connector can be fitted. For larger diameter bundles ferrules of brass or stainless steel are used.

bundle with brass ferrules
Brass ferrules and silicone rubber jacket

bundle with stainless steel ferrules
Steel ferrules and jacket

Ultra low fluorescence bundles

For applications demanding ultra low fluorescence our optical fiber bundles made from CuBall metal-coated fibers offer the optimum solution. Since no epoxy is used in the construction, and only metal-coated optical fibers are used, these bundles are fluorescence free.

Examples of spooled CuBall coated fibers.
CuBALL coated fibers soldered in a brass ferrule

For low cost optical fiber bundles we recommend either glass fibers or polymer fibers. Glass fibers have an N.A of 0.57 and polymer fibers have an N.A. of 0.50. High N.A or wide acceptance angle is usually an advantage in lighting applications.

Glass fiber specification



Core diameter µm
45
Cladding diameter µm
50
Core refractive index
1.62
Cladding refractive index
1.52
Numerical aperture (N.A.)
0.57
Acceptance angle deg.
70
Minimum bend radius (typ. jacket) mm
20


Polymer fiber specification



Core diameter µm
0.25, 0.5, 0.5, 1.0, 1.5, 2.0, 3.0
Core material
Polymethyl methacrylate
Cladding diameter
Flourinated polymer
Cladding refractive index
1.52
Numerical aperture (N.A.)
0.52 (nominal)
Acceptance angle deg.
60
Minimum bend radius
10 times fiber diameter
Maximum operating temperature deg. C
70