Tag Archives: CFP

Preparation for 40G/100G Migration

10G is now common in large enterprises. New network trends continue to drive the demand for high-speed Ethernet, such as the virtualization trend, network storage trend, I/O convergence trend, and data centre network aggregation trend. So 40G and 100G as well as corresponding equipment are introduced into the market. The migration from 10G to 40G/100G is inevitable.

IEEE and TIA Standards

Before planning for migration to 40G/100G network, we should better know well about high-speed Ethernet. The following will talk about it from the side of standards. Because structured cabling systems design is always guided first by standards. The standards for 40G and 100G are significantly different from previous generations; active equipment and how information is transmitted are unique.

First, it’s IEEE standards. IEEE creates the standards that define performance parametres. IEEE 802.3ba 40Gb/s and 100Gb/s Ethernet is the only current standard that addresses the physical layer cabling and connector media maximums for 40/100G fibre channel requirements. IEEE 802.3ba-2010 standard was approved at the June 2010 IEEE Standards Board meeting. The standard is shown in the following table.

Fibre Type Max Distance Max Channel

Insertion Loss

Max Channel Connector

 Insertion Loss

10G OM3 300m 2.6 dB 1.5 dB
10G OM4 550m 2.6 dB 1.5 dB
40/100G OM3 100m 1.9 dB 1.5 dB
40/100G OM4 150m 1.5 dB 1.0 dB

Second, it’s TIA (Telecommunications Infrastructure Standard). For data centres, TIA defines how to apply the parametres to structured cabling systems. It establishes design criteria including space and layout, cabling infrastructure, tiered reliability, and environmental considerations. The standard recommends using the highest capacity media available to maximize infrastructure lifespan.

40G/100G Using MPO/MTP Interface

1G and 10G networks use GBIC (Gigabit interface converter). For example, generally the transceiver SFP+ (small form-factor pluggable) is for 10G network. Later the fibre connectivity in high-speed active equipment becomes condensed and simplified. Transceivers for 40G and 100G are QSFP (quad small form-factor pluggable), CFP and CXP (100G form-factor pluggable). MPO/MTP is the designated interface for multimode 40/100G, and it’s backward compatible with legacy 1G/10G applications as well. Its small, high-density form factor is ideal with higher-speed Ethernet equipment.


Figure1. MPO/MTP Connector

40G and 100G Ethernet employ parallel optics. Data is transmitted and received simultaneously on MTP interfaces through 10G simplex transmission over each individual strand of the array cable.

After introducing some basics of the high-speed Ethernet, we’ll discuss the structured cabling system of migration to 40G and 100G networks in the simplest and most-effective way.

12- or 24-Fibre Cabling Infrastructure

The system includes configurations for 10G to 40G/100G networks over 12- or 24-fibre MTP cabling. What’s the difference between the two methods? Which one is better? The sections will compare the two from the sides of migration, density and congestion.

Migration To achieve the migration, components like trunks, harnesses, array cords, modules, and adapter plates are needed. With the 40G 12-fibre legacy configurations, a second trunk and another set of array harnesses will be needed to achieve 100% fibre utilisation (as shown in Figure 2). For 100G, it also needs these additional components with 12-fibre legacy configuration. But with 24-fibre trunks, a single cable can support a 1G-100G channel and simplify network upgrades immensely (as shown in Figure 3). When equipment is upgraded, there is no need to install new trunks. In addition, limiting changes can reduce the inherent risks to network security and integrity.


Figure2. 12-Fibre Cabling


Figure3. 24-Fibre Cabling

Density The higher density connectivity, the more rack space for active equipment. Thus less floor space is needed. In this way, 24-fibre cabling has the obvious advantage. If the active equipment is configured for 24-fibre channel/lane assignments, there will be twice as as many connections with the same number of ports compared to 12-fibre.

Congestion The more connectivity you are able to run in the same footprint, the more crowded it can become at the rack or cabinet. Fewer trunks reduce cable congestion throughout the data centres. Using 24-fibre MTP trunks for the cable runs will save half the number of cables versus 12-fibre in the network. Runs carry a lighter load, fibres are easier to manage, and improved airflow reduces cooling costs. So 24-fibre MTP trunks offer a huge benefit.


The high-speed network will become more and more popular. It’s very important to know something about the migration to 40G/100G. To upgrade your network, 24-fibre MTP will be a better fibre cabling choice compared with 12-fibre. Do you prepare well for the great migration?

Which One Will You Choose for Your 40/100G Network, OM3 or OM4?

40G has been widely used in data centres. 100G will also come soon. To meet these high bandwidths, related fibre cables are needed. OM3 and OM4 can be used to transmit parallel optical signal. But what is their difference? Which one will you choose for your network?

Both OM3 and OM4 are laser optimized fibre. Their cores size is 50/125. Connectors are the same and both operate 850nm VCSELS (Vertical-Cavity Surface-Emitting Lasers) transceivers. So the difference lies in the construction of the fibre cable, which means OM4 cable has better attenuation and can operate at higher bandwidth than OM3.


Attenuation is the reduction in power of the light signal as it is transmitted (dB). Attenuation is caused by losses in light through the passive components, such as cables, cable splices, and connectors. As the connectors are the same, so the difference in OM3 and OM4 performance is in the loss (dB) in the cable. The maximum attenuation of OM3 allowed at 850 nm by the standards is less than 3.5 dB/km, and less than3.0 dB/km for OM4.

Another factor influencing the cable function is dispersion. Dispersion is the spreading of the signal in time due to the different paths the light can take down the fibre. It has two types: chromatic and modal. In multimode fibre transmission, chromatic dispersion is negligible and the modal dispersion is the limiting factor.

The modal dispersion determines the modal bandwidth that the fibre can operate at and this is the difference between OM3 and OM4. Modal bandwidth represents the capacity of a fibre to transmit a certain amount of information over a certain distance and is expressed in MHz*km. The higher the modal bandwidth the more information can be transmitted. The modal bandwidth of OM3 is 2700 megahertz*km while the mod0al bandwidth of OM4 is 4700 megahertz*km. Thus, OM4 allows the cable links to be longer.

Compared with OM3, OM4 has a lower attenuation and operates at a higher modal bandwidth. That means over OM4 less power is lost during the signal transmission and the signal can be transmitted further or through more connectors (which add to the losses). The following table shows the Ethernet distances at 850 nm supported by OM3 and OM4 respectively.

1Gb 10Gb 40Gb 100Gb
OM3 1000m 300m 100m 100m
OM4 1000m 500m 150m 150m

So why is the standard for 40G only 100m on OM3 and 150m on OM4 compared to 300m and 500m for 10G? There are two reasons. First, when the IEEE 802 standard was created they decided to create a standard based on “relaxed” transceiver specifications so that smaller and lower cost transceivers could be used. Two functions of 10G transceivers (clock recovery and attendant re-timing) are absent in both QSFP+ (40G) and CFP (100G) devices. Second, the standard allows for transceivers with wider spectral width lasers which increase chromatic dispersion (pulse spreading). The quality of transceivers is also a factor.

Which will you choose for your 40/100G network, OM3 or OM4? Except the transmission distance and the cable costs, there are additional factors to consider such as the number of cross connects required and the mix of 40G port to 40G port and 40G port to 10G port. Because 40G signal is transmitted across eight pairs of fibre each with 10G. Similarly, it is important to take into account the likely location of future 100G equipment and the possible 100G to 100G, 100G to 40G and 100G to 10G connectivity requirement.