With ever-greater bandwidths and network connections to deal with in data centers, conventional dual-fiber patch cables like LC cable can no longer meet the demands. To solve this problem, MTP/MPO cables accommodating more fibers in one multi-fiber MTP/MPO connector came into the market, which proves to be practical solutions for 40G/100G/400G high-density cabling in data centers. This article is going to introduce different MTP/MPO cable types and their applications.
MPO (Multi-Fiber Push-on) is the first generation of clip clamping multi-core optical fiber connector. MTP® is a registered trademark of US Conec Ltd. , which is an advanced version of MPO, with better mechanical and optical performance. They look alike and are completely compatible and intermateable. MTP/MPO cables are composed of MTP/MPO connectors and optical fibers. MTP/MPO connectors have a female type (without pins) or a male one (with pins) as shown in Figure 1. The position of guide grooves also results in “Key Up” and “Key Down” MTP/MPO connectors. And a white dot is for identifying fiber position in connectors. MTP/MPO connectors largely increase the cable density and save circuit card and rack space, which are well suited for current 40G/100G cabling and future network speed upgrades.
Figure 1: MTP/MPO Connector Structure.
A variety of MTP/MPO cables are available for different application environments and requirements based on functions, polarity, fiber count, fiber mode and jacket rating.
MTP/MPO trunk cables, MTP/MPO breakout cables and MTP/MPO conversion cables are ideal for high density cabling network, offering better network capacity and flexibility.
MTP/MPO Trunk Cables
MTP/MPO trunk cables are terminated with an MTP/MPO connector (female/male) on both ends, which are available in 8-144 fiber counts for users’ choices. Typically, these multi-fiber MTP/MPO trunk cables are ideal for creating a structured cabling system, including backbone and horizontal interconnections such as 40G-40G and 100G-100G direct connections, so as to achieve a simple and efficient high-performance networking.
Figure 2: 40G-40G Direct Connection with MTP/MPO Trunk Cable.
MTP/MPO Breakout Cables
MTP/MPO breakout cables (aka. harness cables or fanout cables) are terminated with a female/male MTP/MPO connector on one end and 4/6/8/12 duplex LC/FC/SC/ST connectors on the other end, such as 8-fiber MTP/MPO to 4 LC harness cables and 12-fiber MTP/MPO to 6 LC harness cables. Typically, these breakout cables are ideal for short-range 10G-40G and 25G-100G direct connections or for connecting backbone assemblies to a rack system in the high-density backbone cabling.
Figure 3: 25G-100G Direct Connection with MTP/MPO Breakout Cable.
MTP/MPO Conversion Cables
MTP/MPO conversion cables have the same fanout design as MTP/MPO breakout cables but are different in fiber counts and types. They are terminated with MTP/MPO connectors on both ends. Specifically, commonly-used ones are 24-fiber to 2×12-fiber, 24-fiber to 3×8-fiber, 2×12-fiber to 3×8-fiber MTP/MPO conversion cables. They are especially ideal for 10G-40G, 40G-40G, 40G-100G, 40G-120G connections, which eliminate fiber wasting and largely increase the flexibility of the existing 12-fiber and 24-fiber MTP/MPO cabling system.
Figure 4: 40G-120G Direct Connection with MTP/MPO Conversion Cable.
Polarity refers to the matching of the optical transmitter and receiver at both ends of a fiber link. In traditional cabling systems, connectors like LC/ SC can be easily matched, so there is no polarity issue. However, due to the special design of MTP/MPO connectors, polarity issues must be addressed in high-density MTP/MPO cabling systems. To ensure proper polarity, the TIA 568 standard defined three connectivity methods called Method A, Method B, Method C. So there are Type A, Type B and Type C MTP/MPO cables with different structures according to these methods. These MTP/MPO cables usually connect with different MTP/MPO cassettes and fiber patch cables to ensure the right polarity of the optical circuit. Read the white paper Understanding MTP/MPO Cable Polarity for more information about common 8/12/24-fiber MTP/MPO cable polarity and connectivity methods.
Figure 5: 12-Fiber MTP/MPO Cable Polarity.
8/12/24-fiber MTP/MPO cables are usually used for 40G/100G and the latest 16-fiber cables are especially designed for short-reach 400G cabling in Hyperscale data centers. 12-fiber MTP/MPO cable is the earliest developed and most commonly-used solution in 10G-40G, 40G-100G connections. But when using it to transmit 40G QSFP+ module or 100G QSFP28 module, 4 fibers will be left unused, leading to much lower fiber utilization than 8-fiber cables. While 8-fiber MTP/MPO cable system can transmit the same data rate as 12-fiber cabling with less cost and insertion loss, making it a more cost-effective solution. 24-fiber MTP/MPO cable is commonly used to establish 100GBASE-SR10 links between CFP to CFP transceivers. It allows the use of the ratified 100GBASE-SR10 20-fiber technology today, maximizing the infrastructure investment in the event of 4×25 Gb/s ratification.16-fiber MTP/MPO cables utilize the same external footprint as traditional 12-fiber MT (Mechanically Transferable) ferrule. MTP/MPO-16 solution is ideal for aggregation of multiple 8-fiber parallel transceivers and direct coupling to emerging 16-fiber parallel optic links such as 400G QSFP-DD and OSFP.
MTP/MPO cables fall into multimode OM3/OM4 and single-mode OS2 cables. Multimode OM3/OM4 MTP/MPO cables are mostly used for short distances such as inside a building or campus, allowing maximal transmission distance of 100m (OM3) or 150m (OM4) at 40 Git/s. Single-mode OS2 MTP/MPO cables are suitable for long-reach transmission and widely deployed in carrier networks, MANs (Metropolitan Area Network) and PONs (Passive Optical Network). With less modal dispersion, the bandwidth of OS2 is higher than OM3/OM4.
According to different fire rating requirements, MTP/MPO jackets are classified as LSZH (Low Smoke Zero Halogen), OFNP (Optical Fiber Nonconductive, Plenum), CMP (Communications Multipurpose Cable, Plenum) etc. LSZH MTP/MPO cables are free of halogenated materials (toxic and corrosive during combustion), which are ideal for confined places due to better protection for people and equipment during a fire. OFNP MTP/MPO cables contain no electrically conductive elements and are designed with the highest fire rating, which can be installed in ducts, plenums and other spaces for building airflow. CMP MTP/MPO cables can restrict flame propagation and smoke exhaust rate during a fire, which are suitable for plenum spaces, where air circulation for heating and air conditioning systems are facilitated.
MTP/MPO cables are well-received for high-density cabling in data centers, as they are capable of accommodating multi fibers within a single interface, which largely increases network capacity, saves much space and offers ease of cable management. With a variety of MTP/MPO cables available in terms of cable function, polarity, fiber count, fiber mode and jacket rating, it would be better to consider specific needs when choosing suitable MTP/MPO cable solutions.