Reels for fiber optic cable

What makes a fiber reel different

Copper cable is limited by weight. Fiber is limited by bending. The glass inside a loose tube or ribbon cable can take a lot of pulling tension along its length but does not like being curved too tightly, and if it is, the signal loses light or the fiber cracks. Every fiber cable maker publishes a minimum bend radius for its product, one figure for when the cable is under pulling load and a smaller one for when it is at rest. The drum of the reel has to be at least that large, and in practice a good deal larger.

The packaging standard puts numbers on it. NEMA WC 26, as tabled in Anixter's handbook, sets the minimum drum for fiber optic cable at 20 times the cable's outside diameter and never under 12 inches, and notes that some manufacturers recommend 30 times. Corning's procedure for cutting and re-spooling fiber asks for a drum of at least 30 times the cable outside diameter or 8 inches, whichever is larger, and warns that a smaller drum can raise attenuation and damage the cable for good. Compare that with 10 times for nonshielded power cable up to 2,000 volts in the same NEMA table, and you see why fiber reels carry fat drums for their flange size.

Arithmetic from the published multiples. Always check the cable maker's own data sheet, which can be stricter.

The inner end and testing on the reel

Fiber crews test cable before it goes in the ground and again after. To test a full reel without unwinding it, both ends must be reachable. The outer end is easy. The inner end is brought out through a slot or hole in one flange near the drum and protected in a small pocket or box on the outside of the flange. A reel that carried fiber usually shows the marks: an extra hole near the drum, screw holes where a cover was fixed, or a cut-out in the flange.

If you are buying an empty reel to wind fiber on, check that it has a usable exit for the inner end, or that you can drill one without weakening the flange. A clean, round tie-off or start hole near the drum is the easiest version. A torn one can be repaired, but on a fiber reel a sharp edge at that exit is exactly where a cable gets nicked.

That exit side matters when moving the reel. Corning tells crews never to pick up a reel with a forklift from its tail-flange side, where the inner end and its protection sit, and to make sure every flange bolt is tight before loading, since changes in temperature and humidity loosen them.

Who buys and sells empty fiber reels

Broadband construction is the big source. Every one of the 56 state and territory BEAD final proposals has now been approved, with about $18.19 billion planned for deployment across 3.79 million locations, and roughly 62.9 percent of those locations are planned for fiber. That build-out runs through contractors who pull, blow or lash cable off reels, and it leaves empties at every staging yard.

On the buy side, the reels go to people who need to put fiber back onto something. A splicing crew splitting a long reel into shorter segments for a series of drops. A contractor recovering cable from a cancelled route. A distributor of fiber and microduct cutting to order. An enterprise or campus network team keeping spare backbone cable for repairs. Each wants a reel with a smooth drum and sound flanges, in a size that suits the length and their trailer or stand.

Checking a used reel for fiber

Fiber jackets are tough, but a reel that would be fine for rope can still do damage to fiber if it has the wrong defects. The checks are mostly about the surfaces the cable touches.

• Drum staves smooth and flush: a raised or split stave edge presses into the first layers, which carry the most load once the reel is full.
• No missing staves: a gap in the drum lets the inner wraps sag into it, which puts a tight local bend in the cable.
• Inner flange faces clean: no nails, staples or splinters standing proud, and no old tape or wire ties left behind.
• Drum diameter at or above the cable's bend limit: read the cable's data sheet, then measure the drum. If the drum is smaller, no grade of reel fixes it.
• Arbor hole sound: fiber is light, so arbor wear matters less than on power cable, but the reel must still spin true for a smooth payoff during a blow or pull.
• Flanges flat: a warped flange makes the cable wind unevenly at one side and pile up.

Placing methods and what they ask of the reel

How the cable is placed changes what the reel must do. For aerial lashing, the reel rides on a trailer or truck-mounted stand and pays off slowly as the lasher runs along the strand. A reel that wobbles makes uneven tension, so a true arbor hole and flat flanges matter. For underground pulls, the reel sits at the pulling end with a brake, and the reel has to tolerate stop-start loads. For air-blown cable into duct, the payoff is fast and continuous, and the cable is often first laid out in a figure-eight on the ground at a midpoint so the remaining length can be fed in the other direction without twisting.

Wherever the reel sits, mind the out-to-out width. It sets whether the reel fits the stand or trailer the crew owns, and fiber crews tend to standardize on one or two trailer types.

Sizing a reel for a fiber length

Fiber cable is thin, so the capacity formula usually gives large footages on mid-size reels. With footage ≈ (H + D) × H × T × 0.2618 / d², a 36x24x17 reel with a 2 inch clearance holds about 2,053 feet of a 0.75 inch cable, but about four times as much of a cable half that diameter, because capacity rises with the inverse square of d. The bend limit, not capacity, is often what pushes a fiber buyer to a bigger reel.

Superior Essex publishes its standard outside-plant fiber wood reels and what they hold. The chart flags any reel whose drum is under 20 times the cable diameter, its recommended bend limit, which is why its 30-inch and 36-inch reels are marked for a 1.00 inch cable.

So work out two things before you choose: the drum the cable needs, and the footage that drum and traverse can hold. Then pick the smallest flange that does both, which keeps the freight sensible.

Superior Essex notes its chart applies to round cable only and may be further limited by the design of the cable.

Selling fiber reels from a staging yard

Fiber projects move fast and the empties pile up where the crew was staged. Most of those reels are non-returnable and belong to the contractor or the network owner. Some cable makers run return programs, but those generally cover only their own reels and often only full loads. Reels from several makers in several sizes, the usual state of a staging yard, rarely fit.

We buy them as a lot. Group them by flange, traverse and drum, count them, and send a stencil photo. Tell us if inner-end boxes or hardware are still fixed to the flanges; we do not mind, but the buyer will want to know.