In order to ensure the accuracy of the polarity in the MPO network system, it is first necessary to understand the performance of each MPO product. This section will briefly introduce the MPO products in the MPO network system.

MPO connector

An MPO connector can support 12-core, 24-core, 36-core and 72-core fiber optic connections. There is a keyway on each MPO connector. When the keyway is in the upper half of the connector, it is called keyway up (Key up) MPO connector, when the keyway is in the lower half of the connector, it is called an MPO connector with the keyway down (Key down). There is a point on one side of the MPO connector to mark the position of the first core hole.

MPO Fiber Link

MPO adapter

MPO connectors (male) and MPO connectors (female) are paired with MPO adapters. MPO adapters come in two types, Type A and Type B: Type A—A Type A adapter with the keyway up on one side and the keyway down on the other side. Therefore, when connecting two MPO connectors, the keyways of the two connectors are on parallel lines. Type B—The keyways inside both sides of the Type B adapter face up, so when connecting two MPO connectors, the keyways of the two connectors are in a straight line.

MPO optical cable

Both ends of the MPO trunk cable are pre-terminated with (male/female) MPO connectors, which can support 12-core, 24-core, 48-core and 72-core optical fiber connections. MPO branch cable: One end of the MPO branch cable is pre-terminated with a (male/female) MPO connector, and the other end is pre-terminated with multiple duplex LC/SC connectors, supporting multi-core optical cables to single-core or dual-core Conversion of fiber optic cables. MPO transfer module box: The MPO transfer module box adopts a closed box structure, which can accommodate 12-core or 24-core pre-terminated MPO branch optical cables.

Polarity classification of MPO backbone optical cables: MPO backbone optical cables are divided into three types: straight-through, fully crossed and pair crossed, namely, Type A (key up - key down straight through), Type B (key up - key up/key down-key down fully crossed), Type C (key up - key down pair crossed).

Type A straight-through MPO trunk cable

The straight-through MPO trunk cable uses a straight-through cable, and the two ends are pre-terminated with an MPO connector with the keyway facing up and an MPO connector with the keyway facing down. Therefore, the corresponding positions of the optical fibers at both ends of the cable are the same, that is, the left connector The position of the first core hole corresponds to the position of the first core hole of the right connector.

Type B fully crossover MPO trunk optical cable

The fully crossover MPO trunk optical cable uses a reversed cable, and both ends are pre-terminated with MPO connectors with keyways facing up. The position of the first core hole of the machine corresponds to the position of the 12th core hole of the right connector.

Line pair crossover MPO trunk cable

The pair crossover MPO trunk cable is the same as the straight-through MPO trunk cable. The two ends are pre-terminated with the MPO connector with the keyway up and the MPO connector with the keyway down. However, in the line-pair crossover MPO trunk cable, one end of the cable is adjacent. The corresponding positions of the two optical fibers at the other end are opposite to those of the two adjacent optical fibers at the other end, that is to say, the position of the first core hole of the left connector corresponds to the position of the second core hole of the right connector, and the position of the second core hole of the left connector The positions of the two core holes correspond to the position of the first core hole of the right connector.

Duplex jumper type

Three polarity connection methods Different polarity methods use different types of MPO trunk cables. However, all methods utilize duplex patch cords to form fiber optic links. The TIA standard also defines two different types of LC or SC duplex fiber optic jumpers to complete end-to-end duplex connections: A-A (crossover) jumpers and A-B (straight-through) jumpers.

How to manage polarity

This section describes how to ensure the correctness of the connection polarity of the MPO optical device under the TIA standard. The three polarity methods specified in the TIA568 standard are called Type A, Type B, and Type C.

Type A method

A straight-through wiring module and 2 different jumpers are used, one jumper is a straight-through pair, and the other jumper is a reversed pair. The figure below (Rx means receiving, Tx means transmitting) reflects the type A connection mode, which uses a straight-through MPO backbone optical cable. In order to ensure the accuracy of the polarity, the left side of the optical fiber link uses a standard duplex Type A-B jumper wires, A-A type jumper wires are used on the right side.

Class B method

A straight-through wiring module and a straight-pair jumper are used. The figure below reflects the type B connection. This connection method uses a fully crossed MPO trunk cable. Since the corresponding positions of the fibers at both ends of the fully crossed MPO trunk cable are opposite, standard A-B jumpers are used at both ends of the fiber link.

C class method

The polarity is corrected by flipping the pairs in the backbone cable, using the same module and the same jumper. The figure below reflects the type C connection. The type C connection uses a line-to-cross MPO backbone optical cable, and standard A-B jumpers are used at both ends of the optical fiber link.