DIRECT ANSWER
The selection rule
Do not select Type A, B or C from the trunk alone. Start with the equipment interfaces and required transmit-to-receive mapping, then document every component in the channel. The approved polarity drawing—not a generic product name—controls production.
What Type A, Type B and Type C describe
The method names describe fiber-position mapping. They do not by themselves define connector gender, key orientation, fiber grade, polish, loss class or the final equipment interface.
| Method | Position mapping | Procurement note |
|---|---|---|
| Type A | Positions are maintained through the Type A trunk | A polarity transition must be provided elsewhere in the documented channel |
| Type B | The full fiber array is reversed end to end | Often used in parallel-optics designs; verify transceiver and adapter orientation |
| Type C | Adjacent fiber pairs are flipped | Commonly associated with duplex presentation; verify cassette and patch-cord mapping |
Map the complete optical channel before production
A technically correct trunk can still produce the wrong transmit-to-receive mapping when combined with incompatible adapters, modules or patch cords. Freeze the topology before approving labels or pinning.
- Equipment A and B interfaces, lane count and transceiver type.
- MPO fiber count, connector gender, keying and adapter orientation.
- OS2, OM3, OM4 or OM5 fiber grade and connector polish.
- Cassette or breakout LC presentation and port numbering.
- Insertion-loss budget, testing method, labels and end identifiers.
Minimum MPO/MTP RFQ fields
Attach a topology or lane map whenever possible. If a field is unknown, mark it as open for technical review rather than copying a polarity from another project.
| Field | Confirm before quotation |
|---|---|
| Topology | Parallel optics, duplex conversion, backbone or equipment breakout |
| Interfaces | MPO/MTP and LC endpoints, transceiver types and port count |
| Connector | Fiber count, male/female, keying and polish |
| Cable | Fiber grade, jacket, length and pulling-eye requirement |
| Performance | Standard or low-loss target and end-to-end loss budget |
| Identification | Polarity map, port numbering, labels and test-record format |