FOA Guide

Fiber Optic Microcables

As fiber optic communications systems are expanded to accommodate rapidly growing communications needs, thre has been a demand for higher density cables with higher fiber count. This has led to two new cable designs, microcables with up to 288 or even 432 fibers and high fiber count cables. High fiber counts began with loose tube cable at 432 fibers, doubled to 864 fibers, then grew into designs for data centers and metro backbones with 1728, 3456 and 6912 fibers. Microcables are optimized for small size not large fiber counts, and are aimed at installations where their small size simplifies installation and reduces cost.

Fiber Optic Microcable

144 fiber Corning Microcable

Microcable is a term applied to a new class of cables that are very high density cables with greatly reduced the cable diameter. Two fiber developments make a microcable feasible. Bend insensitive fiber allows fibers to be packed into cables with much higher density since the fibers are not as sensitive to the stress caused by the crowded fibers. In addition, the bend insensitive fibers can be coated with smaller diameter primary buffer coatings, 200 microns or less compared to 250 microns for conventional fibers, allowing more fibers to be packed into a smaller space.

Corning microcables - 288 fiber (top) and 144 fiber (middle) compared to a pencil

The differences between conventional and micro cables are substantial. A 144 fiber loose tube cable is typically 15-16mm diameter while a comparable micro cable is only about 8 mm diameter - half the size and about one-third the weight. The smaller size allows for much larger fiber counts, up to 6912 fibers in some high fiber count designs, Microcables generally have a large stiff strength member in the center to allow installation by blowing the cable into microducts.

Microducts come in a variety of sizes and shapes, including versios not show her that are flat, say 6 microdcuts in a row, intended for installation in very narrow grooves cut in microtrenching. Multiple tubes are often installed to allow for future network expansion by simpler installation of future cables without any construction, reducing costs and disruption in the area of construction..

cable in ducts
Corning Microcables in microducts compared to a normal cable in duct (R)

Microcables are available for both premises and outside plant installations. Their small size allows a different installation technique where the cable is "blown" into micro ducts, plastic tubes much smaller than conventional fiber innerducts or conduits. The cable is not really blown into the duct but floated on air to reduce friction then pushed into the duct.

blowing microcable
Blowing cable

Careful design, construction and installation can make microcables almost invisible, as in this installation along the seam between a curb and the roadway paving.


Microducts can also be installed by directional boring, often along with conventional ducts, as shown here. There is a bundle of 6 microducts installed along with 3 conventional 1.25 inch fiber ducts.


After installation, microcables can be prepared and spliced using conventional techniques.

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