MPO, short for Multi-fiber push-on, is designed by NTT for ribbon fiber connections. MPO connector is compliant with the IEC 61754-7 standard and the U.S. TIA-604-5 standard. Defined as an array connector having more than 2 fibers, the MPO Connectors typically come with 8, 12, or 24 fibers usually used for 40G/100G, and the latest 16 fibers for short-reach 400G cabling for hyper-scale data centers.
MTP®, short for Multi-Fiber Pull Off, is a registered trademark by US Conec, an improved version of MPO, both in terms of mechanical and optical performance. It is backward compatible with MPO and has higher specifications.
It is well known that MTP® overmatches MPO. Compared with MPO, the MTP® connector is a multiple-engineered product enhancement. Why? Should we always choose the MTP® cables? We’ll address these problems below.
MPO/MTP® cable consists of a corresponding connector plus optical fiber. The MPO/MTP® connector has a male and a female version, i.e., the male connector has pins to finish precision alignment, and the female connector has guide holes without pins. The detailed structure can be seen in the figure below.
Figure 1: MTP®/MPO Connector Structure.
The MTP®/MPO connector, compared to the normal factor connector like SC, ST, FC, or small form factors like LC, MU, or E2000, dramatically expands the cable density with a much smaller footprint; thus, they’re very suitable for high-density high applications, such as current 40G/100G cabling in data centers, and are future proof for future network speed upgrades.
Types of MTP®/MPO Cables
There’re several variants of MTP®/MPO Cables, including MTP®/MPO trunk cables, MTP®/MPO breakout cables, and MTP®/MPO conversion cables.
MTP®/MPO cables are multimode OM3/OM4 and single-mode OS2 cables. Regarding the fiber mode, you can refer to Single mode patch cord vs multimode patch cord.
In short, multimode OM3/OM4 cables are suitable for short distances less than several hundred meters. The multimode OM3/OM4 MTP®/MPO cables have a maximal transmission distance of 100m (OM3) or 150m (OM4) at 40 Git/s. Single-mode OS2 MTP®/MPO cables have theoretically no bandwidth limit. It is the proper choice for long-reach transmission and is widely deployed in carrier networks.
MTP®/MPO jackets can be divided as LSZH (Low Smoke Zero Halogen), OFNP (Optical Fiber, Nonconductive, Plenum), CMP (Communications Multipurpose Cable, Plenum), etc.
The polarity of MTP®/MPO
The big difference between MTP®/MPO and other non-ribbon connectors lies in the polarity.
Simply put, polarity refers to matching the optical transmitter and receiver inside the cable to ensure the right transmitter (TX) goes to the correct receiver (RX). Traditional connectors like LC and SC don’t have this polarity issue as they can easily match each other. In contrast, MTP®/MPO has to deal with polarity properly, thanks to their unique design. TIA 568 regulates three connectivity methods: Method A, B, and C. Each method requires a specific type of MTP®/MPO cable. See the figure below for a visual illustration.
Figure 2: 12-Fiber MTP/MPO Cable Polarity.
The Comparison of MPO and MTP®
Due to the mechanical features, MTP® performs better than MPO. Let’s dive into the details.
Regarding the MPO’s plastic pin clamps which may result in pins breaking, MTP® uses a metal pin clamp to ensure firmly clasp and avoids inadvertent damage during frequent mating.
MTP® adopts the floating ferrule that MPO doesn’t take. The floating ferrule design helps keep physical contact over a mated pair under an applied load, leading to better mechanical performance.
Guide Pins are essential to precision alignment. MTP® adopts tightly held tolerance stainless steel elliptical guide pin tips, which contribute to minimizing the debris, yet MPOs’ chamfered-shaped guide pins will produce more debris.
Like floating ferrule, this is one of the unique features of MTP®. It permits access to performance testing, to smooth revert the gender at any moment, and to rework or repolish the MT ferrule. All these features are not available in MPO.
MTP® improves issues like insertion loss, dropped packets, etc. The precision alignment significantly reduces the insertion loss and return loss. Now, the optical performance of MTP® comes closer to the single fiber connectors.
Some additional improvements, like the redesign of internal components and the elliptical shape of the lead-in on the precision alignment guide pins, combined to stand frequent mating without damage, reducing the wear and tear and debris generation, resulted in improved stability and durability performance.
MTP® or MPO: which one to choose for high-density cabling systems?
Both perform well, but MTP® does better. In terms of mechanical performance, optical performance, reliability, and future upgrades, MTP® is the preferred solution. Needless to say, it costs more than MPO.