Methods include the entire link while Type is the polarity of the MPO cable. At some point the link usually will convert the TX to a RX (i.e. LC Pin 1 and Pin 2 will be swapped). In the diagrams below, this is being accomplished in three separate methods.
Method A - creates the swap by having two different configurations of patch cables on each end. On one side the patch cable is pair-flipped, while on the other it is straight through. The cassettes are both straight through and the Type A trunk cable is also straight through (See “Cable Types Diagram”).
Method B - creates the swap by having special “Key-up/Key-up” adapters on the straight through cassettes on each end, and a Type B rollover cable as the trunk.
Method C - creates the swap by having the trunk cable perform the swap using a Type C “Pair-Flipped” trunk cable.
Cable Types Diagram
The MPO/MTP® Type A is considered “straight through” (Pin 1 to Pin 1)
Type B is considered “Reversed”, “Crossed” or “Rollover” (Pin1 to Pin 12)
Type C is considered “Flipped”, “Pair-Flipped”, or “Swapped” (Pin1 to Pin2/Pin2 to Pin1)
Note: Type A and Type B can be interchanged by removing and reversing the housing on one side of the cable which will switch the cable from a Straight Type A to a Rollover/Reversed/Crossed Type B or vice versa. Type C cannot be changed.
Understand Multi-fiber connector basics & terminology
- Differentiate between polarity "Types" & "Methods"
- Identify and Compare:
- Type A vs Type B
- Method A vs Method B
- Trace a channel in its entirety from transmitter to receiver
Why is this important?
- Data Center trends
- Multi-fiber connectors are increasingly popular in Data Centers, Telecom, and many other applications
- Common to have single-fiber connectors in the same link (e.g. LC's to MTP's back to LC's)
- More fiber is just inherently more challenging to keep track of
- Concatenation of multiple patchcords, trunks, and cassettes
- Multi-row transceiver modules
- Equipping yourself with some basic knowledge can enable you to overcome these challenges
Connector vs Ferrule
- "Ferrule" = Inner component which the fiber ribbon is terminated (i.e. epoxied, cured, polished)
- "Connector" = Outer component which holds the ferrule and provides a more robust connection
Multi-fiber = Multiple fibers in one connector
- Fibers are typically bundled in 12-fiber ribbons, with each individual fiber identified by a standard sequence of unique colors (TIA-598-D)
- Ribbon is typically manufactured in a flat factory ribbon, or as loose individual fibers in a round tube/cable
MPO vs MTP® vs MT
- MT = Most common multi-fiber ferrule
- MPO = Most common multi-fiber connector
- MTP is US Conec's brand of MPO connector
- Both connectors are intermateable per TIA-604-5-E (FOCIS 5) industry mechanical standard
- Both available in SMF and MMF variants
- 12-fiber MTP is most common variant (one row of 12 fibers)
- 24-fiber MTP increasing in popularity (two rows of 12 fibers)
- Both available in multiple alternative fiber and row counts
MPO Polarity Industry Standards
- TIA = Telecommunications Industry Association
- Leading industry standard providing guidance on MPO polarity
- Important update:
- In October 2016, TIA published TIA-568.3-D (i.e. revision D)
- Rev D adds new guidance on two-row MPO polarity (e.g. 24-fiber)
- Previously, MPO polarity was spread across two TIA documents (TIA-568-C.3 & TIA-568-C.3-1)
- Provides guidance on how to:
- Manufacture individual assemblies (e.g. patchcords, adaptors, trunk cables).
- Concatenate these assemblies into a proper link (i.e. transmitter channels connect to the receiver channels)
- Using consistent terms is critical to avoid confusion.
- Important Terms:
- Polarity Types: Individual fiber optic assemblies (i.e. patchcords, adaptors, trunks)
- Polarity Methods: Concatenation of fiber optics assemblies above
Note: TIA defines multiple polarity Types and Methods. While both are labelled A, B, & C, we will show how these are two entirely different sets of items.
- Fiber Number: Sequential number that corresponds to the Blue-Aqua TIA color sequence
- Position Number (or Fiber Position Number): Sequential number that Hole location on the MPO ferrule
Note: Typically these numbers are both 1-12, but we will show that the Fiber Number does not always match the Position Number.
- Top Row: Row of fibers closest to the MPO key
- Bottom Row: Row of fibers farthest from the MPO key
- Near End: Connector on left side of TIA drawings
- Far End: Connector on right side of TIA drawings
- KeyUP to KeyDOWN: Assembly which the keys of the mated MPO pair are opposed
- KeyUP to KeyUP: Assembly which the keys of the mated MPO pair are aligned