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Fiber Optics

FIBER OPTIC CABLE CONSTRUCTION

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Fiber Optics

We’ve already looked at the difference between SM and MM fiber and the core, cladding and buffer differences between them.

That is the preliminary composition of fiber.

The construction process adds strength members such as aramid yarn (Kevlar) and cable jacketing.

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Fiber Optics

In some cases a fiber glass rod is added in the center of the cable assembly to maintain the proper bend radius.

If fiber is installed outdoors a metal sheath is added along with two layers of rigid jacketing and has a gel like material for moisture resistance.

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Fiber Optics

All of these different construction types fall under one of three categories:

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Fiber Optics

1. TIGHT BUFFERED:

These cables consist of several 900um fiber strands surrounded by strength members and bundled in a single jacket.

In some cases it is 900um fiber surrounded by aramid yarn and a jacket, i.e. simplex fiber

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Fiber Optics

Some examples are:

1. Simplex 2. Zip cord/ patch cords

3. Distribution 4. Breakout

Distribution type fiber is the typical type of cable installed in today's backbones.

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Fiber Optics

Tight buffered fiber used in the field

PATCH CORDS TWO SIMPLEX

CABLES

DISTRIBUTION FIBER

BREAK OUT FIBER

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Fiber Optics

Currently fiber installs are done with MC type distribution fiber for todays backbones.

MC is a interlocking metal clad that surrounds the distribution style fiber, like the cables electricians use to wire commercial building lights.

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Fiber Optics

This MC style cable is color coded to indicate the three types of fiber we install.

ORANGE = MM 62.5/125

BLUE = OM3 50/125

YELLOW = SM 8.3/125

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Fiber Optics

By using this MC type we do not have to install conduit or inner-duct to protect the fiber backbone, therefore it is a labor saving solution, which is why it is so popular.

The challenge is removing the interlocking armor from the cable jacketing, this is done with a roto split tool.

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2. LOOSE TUBE CABLES:

Loose tube cables consist of color coded tubes that contain either 6 or 12 strands.

All the tubes are surrounded by a strength member (aramid yarn), as well as a fiberglass bend radius rod and additional PVC cords to maintain the concentricity of the cable.

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Loose tube fiber

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All of this is then coated by a heavy duty outside jacketing.

Loose tube cables are typically used for OSP applications.

They also can have both MM and SM types of fiber in one cable assembly, remember that SM has a smaller buffer, that being the case the MM strands will also have the same size buffer.

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Loose tube cables also contain a water proofing gel and may also contain icky-pic.

This gel requires hydrasol to clean and prep the cable for termination it is similar to citrus type cleaners.

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3. RIBBON CABLE:

Ribbon cable is just as it sounds. Multiple strands of fiber are bonded together to form a flat ribbon. These ribbons can then be stacked to form multiple layers.

This type of fiber allows for very high counts that utilizes a small space.

Transatlantic / Transpacific applications

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Fiber Optics

Ribbon fiber

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Hybrid fiber is any fiber optic cable that has both SM and MM fibers, SM is always the first in the count.

For example if you are installing a 96 strand fiber the cable jacket will have the following information on it; SM 24/MM 72.

When terminating this cable the first 24 strands are single mode and the rest is multimode fiber.

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Fiber Optics

Here is an example of a hybrid composite tight buffered fiber optic cable with the product description;

Hybrid cables offer the same great benefits as our standard indoor/outdoor cables, with the convenience of installing multimode and singlemode fibers all in one pull. Our composite cables offer optical fiber along with solid 14 gauge wires suitable for a variety of uses including power, grounding and other electronic controls.

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Fiber Optics

Fiber optic cables can be further classified as defined in NEC article 770.9 Types;

Nonconductive: These cables contain no metallic members and no other electrically conductive materials.

Conductive: These cables contain non current carrying conductive members such as metallic strength members, metallic vapor barriers, and metallic armor or sheath.

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Composite: These cables contain optical fibers and current carrying electrical conductors, and shall be permitted to contain non current carrying conductive members such as metallic strength members and metallic vapor barriers.

In the code these cable designations are;

OFN (optical fiber non-conductive)OFC (optical fiber conductive)

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Composite fiber is OFC (optical fiber conductive).