Things Should Be Noticed Before Choosing 24-Fiber MPO Cable

In the process of migrating to greater bandwidth 40G and 100G network, MTP cabling system which provides high density and high performance plays an important role. Whether to use 12-fiber or 24-fiber MPO cable has been a hot topic in higher speed networking migration. In my previous blog Choosing 24-Fiber MPO/MTP Cabling for 40/100G Migration, we have indicated that MPO 24 fiber cable is more suitable for 40G and 100G network. Besides, with active equipment planning to use a single 24-fiber MPO interface for 100G and the channel currently requiring 20 fibers, many IT managers are also considering the use of 24-fiber MPO solutions. However, before choosing 24-fiber MPO cable, there are some facts that should be noticed.

The Higher the Fiber Count, the Higher the Loss

Optical loss budget is a big concern among data center managers, and due to limitations in the protocol, standards now require a total connector loss budget of 1.0 dB for 40G and 100G, but a 24-fiber MPO connector typically has a loss of 0.5dB which is much higher than 0.2dB that 12-fiber MPO connector has. This is mainly due to the fact that the more the fiber count, the higher the loss. The higher loss of the 24-fiber MPO limits data center managers to having just two mated pairs in a channel.

Note: Current proper polishing technique can address 24-fiber MPO to meet the low loss requirement as 12 fiber MPO connector. For example, 24-fiber MTP trunk cable in FS.COM only has 0.35dB insertion loss.

The Higher the Fiber Count, the More Difficult to Control End-Face Geometry

In a quality fiber connector, the fibers protrude slightly beyond the ferrule. When two fibers are mated using the right pressure, the fibers will deform slightly to fill in any gaps and provide a solid mating. Any variance in the pressure can impact the insertion loss and return loss on a fiber-to-fiber basis. To achieve consistence pressure, it is important to have a very flat ferrule after polishing with all the fibers protruding equally. With higher count arrays, like 24-fiber MPOs, there are more fibers to control, which can significantly increase the odds for height variance. For example, in the following 72-fiber array, if we look at this graphic of the middle two rows of fibers, we can see the variance in the height profile. The height variance becomes even more pronounced across more rows of fibers. Besides, it is more difficult to achieve a flat ferrule polishing on a large array area.

Although the polishing technique has been significantly improved, there still exists limitation to achieve a flat end-face and equal pressure over the array.

Standards and Testing Remain an Issue to 24-fiber MPO Cabling

100GBase-SR4 standard has be a reality and that most of users is running 100G over 8 fibers, rather than 20, which will render the 24-fiber MPO a dated interface for 100G Ethernet. In addition, the MPO cabling testing is far more complicated than duplex cabling testing. You have to gain very professional training, tools understanding that you can efficiently conduct multifiber testing. In other words, if there is any issue with the multifiber cabling, it’s not easy to troubleshoot it.

It's Still Your Choice

With the significant demand for higher speed 40GbE and 100GbE, MPO cabling has become more popular than ever. We have indicated that 24-fiber MPO cable reveals more advantages than 12-fiber MPO cable, however, before choosing it, there are more factors we have talked above that should be taken into consideration.

Decoding Four types of 100G QSFP28 Transceiver

With the development of IP-based multimedia service, especially video service, network traffic has been continuously rising. As a result, 40G and 100G have emerged as the key technologies capable of supporting the growth in network bandwidth. After a lengthy period of hype, 40G technologies have finally widely been deployed. And now it is 100G’s turn. While 100G networking may seem excessive to many right now, there are many industries where that 100G speeds are quickly becoming necessary. This post will introduce four QSFP28 transceiver types that are commonly used in 100G data center.

QSFP-100G-SR4

QSFP-100G-SR4 or 100GBase-SR4 QSFP28 optical transceiver is a full duplex, photonic-integrated 100G module, which uses 4 fibers for transmit and 4 for receive, with each lane supporting 25Gbp, providing an aggregated data rate of 100Ggps as shown below on up to 70m of OM3 MMF and to 100m of OM4 MMF. Like 40GBase-SR4, 100Gbase-SR4 uses a MPO 12 cable with 4 strand for transmit and 4 for receive, allowing for existing 40GBase-SR4 fiber assemblies to be reused when higher performance is needed. This interface standard has been introduced alongside the 100G QSFP28 offerings now, arriving on the market in order to make any 40GbE to 100GbE upgrade as seamless as possible.

QSFP-100G-LR4

QSFP-100G-LR or 100GBase-LR4 QSFP28 is another 100G standard, which focuses on longer data transmission up to 10km over single-mode fiber. Like 40GBase-LR4, the 100GBase-LR4 is also a multilane optic. However, each lane’s data rate is increased to 25Gbps. It has duplex LC interface and uses WDM technologies to achieve 100G dual-way transmission over four different wavelengths around 1310nm that can be seen in the image below.

QSFP-100G-PSM4

Targeted to service the need on a parallel single-mode infrastructure, QSFP28 PSM4 module is a low cost solution to long reach data center interconnect. It uses four parallel fibers (lanes) operating in each direction, with each lane carrying a 25G optical transmission as shown below. Interfaced with MPO connector, it can support distance up to 500 meters over single-mode fiber, which covers a wide rage of applications in data center.

QSFP-100G-CWDM4

Backed by the CWDM4 MSA Group, QSFP28 CWDM4 is a 100G interface that address data communication links up to 2km in the data center. The CWDM4 architecture employs 4 lanes of 25Gbps using CWDM technology to transport 100G optical traffic across duplex LC single-mode fiber. Compared to 100GBase-LR4, CWDM4 is an alternative for long transmission distance in data center. The working principle can be seen in the following image.

Summary

100G Ethernet is no longer a fantasy, and it is on the way. QSFP28 is a key to the 100G deployment. In the part above, we have introduced four types QSFP28 modules widely used in 100G network. All of these modules that have been tested and are 100% compatible can be purchased in FS.COM. If you have any related requirement, kindly visit FS.COM.

The Differences Between MPO and MTP

With the advent of MTP and MPO connectors, it has become common practice in the custom cable field to use these two acronyms interchangeably when referring to certain kinds of fiber optic cable. It is said that all MTP connectors are MPO connectors, however not all MPO connectors are MTP connectors. This article is intended to clarify the differences between the terms—MTP and MPO.

What are MPO Connector and MTP Connector?

The MPO connector is a frequently used abbreviation which stands for “muti-fiber push on” and refers to the family of fiber optic connectors used to connect or cross-connect equipment and cables with minimum attenuation and reflection. It is a multi-fiber connector which is standardized within the international regulatory framework (the ICE 61754-7 standard) and also the U.S. (TIA-604-5 standard). There are more than 100 different brands and styles of MPO cables on the market nowadays, each with different strengths, weakness and best-fit applications.

The term MTP is registered trademark of US Conec and is described as “a high performance MPO connector with multiple engineered product enhancements to improve optical and mechanical performance when compared to generic MPO connectors.” It means that MTP connectors are fully compatible and compliant with all MPO connectors standards, regulations, and requirements; however, they also have a number of other features that most generic MPO connectors do not possess. For example, MTP connectors have a removable housing allowing users to rework, re-polish, and scan the ferrule, as well as change the gender, even after assembly or in the field.

Differences Between MTP and MPO

The main difference between MTP and MPO is in relation to its optical and mechanical performance. The MTP connector features a ferrule float which will help improve physical contact and the MT ferrule can float inside the MTP to keep two mated ferrules maintaining contacting if you have overused about the cable, while generic MPO connector do not have the ferrule float feature. In addition, the MTP has a connector spring designed to maximum ribbon clearance and prevent fiber damage. The MTP has elliptical shaped guide pins which can reduce ferrule wear, while generic MPO connectors have chamfered shaped guide pins. The elliptical shaped does not chip the ferrule material being MPO’s chamfered guide pins. And it serves to reduce the amount of debris that may fall into the guide pin holes or on the ferrule end face. Furthermore, MTP connectors’ exceptionally dense fiber count, in relation to their relatively small footprint, makes them a popular choice in data centers that are actively trying to converse space. Their plug-and-play capabilities make them easy to install and efficient to operate.

Conclusion 

As technology still grows fast, MTP and MPO are used in many applications. However, MTP has a few functional improvement of MPO, so we used MTP a lot better than MPO in applications, like MTP cassettes that can allow for the fan-out of up to 24 connections, and MTP trunk cables that can be used as the backbone of a modern data center. Although MTP and MPO are not perfectly interchangeable, they are both inextricably linked as the industry grows.