Fiber Optic Filament

Fiber optic filament is the light-carrying medium at the heart of every fiber optic lighting installation.

Read full description & FAQ ↓

9 Items

Fiber optic filament is the light-carrying medium at the heart of every fiber optic lighting installation. Made from PMMA (polymethyl methacrylate) — a flexible, shatter-resistant acrylic polymer — each strand acts as a light pipe that channels photons from a source LED at one end to an emission point at the other. No electricity flows through the fiber itself: the strand is optically active but electrically inert, which makes fiber optic filament inherently safe for wet locations, children's rooms, and any environment where exposed electrical conductors are prohibited or undesirable. We carry two glow types: end-glow filament, which emits light only from its polished tip, and side-glow filament, which radiates light along its entire length as a continuous luminous line.

End-glow filament is by far the more common of the two types and the basis of nearly every fiber optic lighting project you will encounter. Light enters the polished input face, bounces along the core via total internal reflection, and exits only at the far tip — the fiber's outer surface stays dark during operation. This principle is what makes star ceilings possible: hundreds of individual strands are threaded through a ceiling panel, each one producing a single bright point at the surface while the rest of the fiber is hidden above. A single high-output LED can illuminate an entire bundle of end-glow fibers simultaneously, and changing the LED color changes every strand at once. Strand diameters range from 0.25mm (thinner than a human hair, suitable for dense background star fields and N-scale model railroad windows) up to 3.0mm (bright enough for task-level accent lighting and large decorative installations). We stock individual strands in diameters of 0.25mm, 0.50mm, 0.75mm, 1.0mm, 1.2mm, 1.5mm, 2.0mm, 2.5mm, and 3.0mm — browse End Glow Fiber Optic Filament for the full selection.

Side-glow filament uses a modified cladding layer that intentionally leaks light along the fiber's length rather than trapping it for tip emission. The visual result is a continuous glowing line — similar in appearance to EL (electroluminescent) wire or flexible neon tubing, but driven by a simple low-voltage LED instead of a high-voltage AC inverter. Side-glow fiber is the go-to material for Tron-style cosplay costumes, pool and spa perimeter outlines, bar countertop accent lines, staircase riser lighting, and any architectural or decorative application where a luminous contour is the desired effect. It can be cut to any length and bent around moderate curves without breaking. Browse Side Glow Fiber Optic Filament for available diameters and lengths.

Choosing the right filament diameter is the most important specification decision. Thinner fibers (0.25mm through 0.75mm) are extremely flexible, nearly invisible when unlit, and ideal for high-density point-source arrays like star ceilings and miniature model lighting. They require smaller drill holes (a pin vise with a 0.5mm bit is sufficient for the thinnest strands) and can be routed through tight curves without cracking. Thicker fibers (1.5mm through 3.0mm) transmit dramatically more light per strand — a 3.0mm fiber delivers roughly 36 times the cross-sectional area of a 0.5mm fiber, which translates directly into brighter tip output. The trade-off is reduced flexibility and larger mounting holes. For star ceilings, most builders mix multiple diameters: 0.75mm or 1.0mm for the bulk of the field, with scattered 1.5mm and 2.0mm strands to simulate brighter first-magnitude stars. For single-strand accent lighting or indicator applications, 1.5mm to 3.0mm provides the best visibility.

Preparing the fiber ends is critical to brightness. A rough-cut end scatters light in all directions and can reduce transmission by 30-50% compared to a polished surface. After cutting with sharp scissors or a blade, polish the end face by wet-sanding with 400-grit then 800-grit sandpaper, or by briefly passing the tip through a lighter flame to melt the surface smooth (one to two seconds — just enough to glaze, not deform, the fiber). Polish both ends: the coupling end where the LED meets the fiber, and the emission end where the viewer sees the light. For star ceiling builds, polishing every strand is time-consuming but makes a dramatic difference in the finished result — budget the time and do not skip it.

Coupling multiple fiber strands to a single LED is straightforward. Bundle the polished input ends together, pack them tightly into a short section of heat-shrink tubing or a drilled ferrule, and position the bundle directly against the LED lens face. Clear-top DIP LEDs with narrow beam angles (15-30 degrees) concentrate their output into the fiber acceptance cone and provide the best coupling efficiency. A 5mm clear white LED can comfortably drive 20-50 thin strands; larger bundles benefit from a 10mm LED or a dedicated high-power illuminator module. For color-changing effects, use an RGB LED or a color-cycling animated LED — the fiber transmits whatever color is fed into it, so one LED swap changes the entire installation.

PMMA fiber is suitable for all indoor installations and sheltered outdoor use. Direct prolonged UV exposure from sunlight will gradually yellow the material and reduce light transmission, so permanently exposed outdoor runs should be protected with UV-stabilized conduit or sleeving. In wet or submerged environments (pools, spas, fountains, aquariums), the fiber itself is completely safe to immerse — only the LED source needs to remain dry and accessible. For temperature extremes, PMMA fiber operates reliably from roughly -40C to +70C, covering essentially all residential and commercial environments. Browse our full Fiber Optics section and pair your chosen filament with a source LED from our Component LEDs catalog.

Frequently Asked Questions

End-glow filament channels light through its core and emits it only at the polished tip — the fiber body stays dark. This is the type used for star ceilings, indicator points, and model lighting. Side-glow filament leaks light along its entire length, producing a continuous glowing line similar to neon or EL wire. Side-glow is used for contour lighting, costume accents, pool edges, and architectural outlines. Both types are driven by the same LEDs — the difference is in the fiber cladding, not the light source.
We stock end-glow fiber optic filament in nine diameters: 0.25mm, 0.50mm, 0.75mm, 1.0mm, 1.2mm, 1.5mm, 2.0mm, 2.5mm, and 3.0mm. Thinner fibers are more flexible and produce smaller, subtler points of light — ideal for dense star ceiling fields and miniature model lighting. Thicker fibers transmit more light and produce brighter endpoints — better for accent lighting, indicator points, and single-strand applications where visibility is the priority.
A standard 5mm clear-top DIP LED can comfortably illuminate 20-50 thin strands (0.25mm to 0.75mm) when the polished bundle is pressed against the lens face. A 10mm LED or dedicated illuminator handles larger bundles of 100+ strands. The limiting factor is the LED's emitting surface area versus the total cross-sectional area of the fiber bundle — strands at the outer edge of an oversized bundle will receive less light. For very large star ceiling projects (500+ strands), split the fibers across multiple LED sources or use a high-power illuminator with a focusing lens.
No. Fiber optic filament is a passive plastic strand that transmits light only — no electrical current flows through it at any point. This makes it inherently safe for wet locations (pools, spas, fountains), children's sensory rooms, and anywhere exposed conductors are a concern. The only electrical component is the source LED, which can be mounted in a remote, dry, accessible location. The fiber strands themselves can be safely immersed in water, handled by children, and routed through areas where wiring would be prohibited by electrical code.
The fiber itself is color-neutral — it transmits whatever color the source LED produces. To change the color of your entire fiber optic installation, simply swap the LED at the input end. Use a white LED for clean white light, a colored LED for a fixed color, or an RGB LED with a microcontroller for user-selectable colors. An animated color-cycling LED will automatically shift through the spectrum with no external controller required — an easy way to add dynamic color to a star ceiling or accent installation.
PMMA plastic optical fiber has an attenuation rate of roughly 0.2-0.5 dB per meter in the visible spectrum, which means noticeable brightness loss begins at runs beyond about 3-5 meters for decorative applications driven by a standard 5mm LED. For runs under 2 meters — which covers the vast majority of star ceiling, model, and accent lighting projects — attenuation is negligible. Longer runs require a higher-output source (10mm LED or dedicated illuminator) and thicker fiber to compensate. Tight bends also increase loss: maintain a minimum bend radius of roughly 10 times the fiber diameter to avoid excessive light leakage at the bend point.