MTP®/MPO Cassette Type A vs Type B
Updated at Jan 7th 20251 min read
With the rapid advancement of information technology, MTP®/MPO cassettes play a crucial role in modern communication. Type A and Type B MTP®/MPO cassettes are two common types of fiber cassettes, and many users may have questions about the difference between them and want to know how to choose the correct MTP®/MPO cassettes. Today, this essay will answer all your questions.
MTP®/MPO Cassette Type A vs Type B: What Are They
An MTP®/MPO cassette is a compact, modular device designed to organize and manage fiber optic connections in high-density environments like data centers and enterprise networks. One side features an MTP®/MPO connector pre-terminated with multiple fibers, while the other side has individual connectors such as LC or SC, facilitating connections to equipment or patch cords. By maintaining proper polarity to ensure precise signal transmission between transmitters and receivers, MTP®/MPO cassettes simplify network installations, reduce maintenance complexity, and enhance scalability. These cassettes are typically categorized into two types—Type A and Type B—based on their internal wiring configurations, which determine fiber alignment and signal direction, making their correct selection vital for reliable structured cabling systems.
MTP®/MPO Type A Cassettes
Type A MTP®/MPO cassettes, also known as straight-through cassettes, use a straight-through cabling configuration. Within the cassette, the internal connection follows a “Key Up to Key Down” orientation. This design maintains a consistent fiber sequence between the MPO internal connector and the MPO array cable connector. For instance, the P1 fiber at one end of the connector passes through the cassette and terminates at the P1 position on the opposite side.
MTP®/MPO Type B Cassettes
Type B MTP®/MPO cassettes use a crossed (flipped) cabling configuration, where the fiber bundle is reversed at the ends. These cassettes follow a “Key Up to Key Up” design, meaning the fiber positions at both ends are mirrored. For example, the P1 fiber on one connector is mapped to the P12 position on the opposite connector.
MTP®/MPO Cassette Type A vs Type B: What Are The Differences
Polarity: The main difference between Type A and Type B cassettes lies in their polarity configurations, with Type A being straight-through and Type B being flipped. Proper polarity configuration ensures optical signals are transmitted correctly from the sender to the receiver.
Applications: Type A is typically used for standard direct connections, while Type B is employed when fiber core inversion is required to match the polarity of the fiber optic network.
Expandability: Although both cassettes can be used to expand fiber optic networks, they have different applicable scenarios. Type B MTP®/MPO cassettes are more commonly used in the expansion and migration of high-rate networks.
MTP®/MPO Cassette Type A vs Type B: Which to Choose
The connector transition inside the MTP®/MPO cassette is factory-installed and supports all three polarity methods defined by the TIA standard. The adapter mounted at the rear of the cassette determines whether the cassette is configured for Method A or Method B, ensuring proper signal transmission in the fiber optic link. Regardless of the polarity method, the internal connections of the cassette remain the same, simplifying installation and maintenance.
In the market, the majority of fiber optic cassettes are of type A, as type A is easier to deploy, suitable for both single-mode and multimode channels, and can easily support network expansions. The biggest limitation of type B fiber cassettes is that they do not allow the use of angled physical contact (APC) single-mode connectors. However, the selection of an MTP®/MPO cassette depends on the choice of MTP®/MPO cable, and the MTP®/MPO cassette should be perfectly compatible with MTP®/MPO connectors at both ends of the MTP®/MPO cable.
Conclusion
Understanding the differences between Type A and Type B MTP®/MPO cassettes is critical for deploying a reliable and efficient fiber optic network. By selecting the appropriate cassette type and ensuring compatibility with your cabling standards, you can optimize network performance and minimize potential issues. You can also refer to our white paper Understanding Fiber Polarity for a completed fiber polarity guide of our products.