Duplex LC vs MPO-12 and MPO-16, polarity types A/B/C, pinned vs unpinned, and breakout cabling.
Updated October 2026 · AltoChip team · General reference — project specifics are confirmed in each quotation.
LC duplex carries one transmit and one receive fiber — used by SR, CWDM4, FR4, LR4 and most single-lane optics. MPO (MTP is a branded MPO) carries many fibers in one ferrule — MPO-12 for 4-lane parallel optics such as SR4 and DR4, MPO-16 for 8-lane optics such as SR8 and DR8. MPO-12 and MPO-16 are keyed differently and are not interchangeable.
A parallel link only works if each transmitter reaches the matching receiver. Trunk cables are built to polarity Type A, B or C, and MPO ends are pinned (male) or unpinned (female). Module-to-module links typically use Type B, female-to-female MPO cables — but the right answer depends on any cassettes or panels in between, so we confirm polarity against your cabling plan instead of assuming.
One 400G DR4 port can feed four 100G single-lane ports through an MPO-to-4×LC breakout, when both ends support it. Breakouts need the switch port configured for breakout mode and the far-end optics to match the lane type.