Submittal

Fiber Systems:

Polarity Best Practices

Male

Array

Connector

Female

Array

Connector

Array

Adapter

Pins

Key Up

No Pins

Key Down

White Dot

White

Dot

Key Up

Pin Location

Fiber Position

Figure 3. Array Connector Schematic (left) and End View (right)

Cassettes. A cassette is a packaged, pre-terminated cabling assembly that transitions from small form factor

ribbon-style fiber cables and array connectors to traditional single-fiber connectors (see Figure 4). The primary

function of cassettes is to provide quick, scalable plug-in network deployment of up to 12 fiber ports (24 fibers)

in a single assembly to support high-density applications. Array adapters at the rear of cassettes are also keyed

to ensure proper orientation with keyed array connectors.

Patch Cords. Duplex patch cords used to complete serial duplex pair connections are available in two types

(see Figure 5), depending on which polarity technique is used. The “A-to-B” patch cord connects position A on

one end of the cord to position B on the other end; this is termed “straight-through” wiring. The “A-to-A” patch

cord connects position A on one end of the cord to position A on the other end, and is known as “crossover”

wiring.

Ribbon Cable Assemblies. Factory-assembled modular fiber cassettes are connected to one another with

connectorized ribbon cables. Each 12-fiber ribbon (or “trunking”) cable translates into six 2-fiber serial optical

circuits that require polarity management. Figure 6 shows the three fiber-and-connector trunk combinations

described in TIA/EIA-568-B.1 Addendum 7 for polarity management when using fiber array cables; the chart

indicates the transformation of fiber position along each circuit.

Figure 4. Fiber Arrangement in Cassette

Figure 5. A-to-A and A-to-B Patch Cords