Tag Archives: 12-fiber MTP

8-Fiber MTP VS. 12-Fiber MTP Cables

MTP fiber cable in data center becomes increasingly popular in data center with the wide deployment of 40G and 100G network. It is common that 40G and 100G network usually based on 12-fiber MTP networking system. However, not all the 12 fibers of MTP cable are used.8-fiber MTP cable

12-Fiber MTP Cable During Transmission

There are usually 4 fibers left unused, if you are using a 12-fiber MTP cable to transmit 40G with QSFP+ module or 100G with QSFP28 module. The following shows how 12-fiber MTP fiber cable works when it is used to be connected with 40Gbase-SR4 QSFP+ module. If more 12-fiber MTP cables are used, more optical fibers will be wasted. As IEEE standards like 40GBASE-SR4 and 40GBASE-SR10 uses only 8 fibers for dual-way transmission, manufacturers provide new versions of MTP fiber cable which contains only 8 optical fibers but still used the standard MTP interfaces.40gbase-sr4

Base-8 MTP for Higher Density and Lower Utilization

Network built with 8-fiber MTP system can transmit the same data with less cost and higher density compared with 12-fiber MTP system. All fiber will be 100% utilized in base-8 MTP products. It could be a cost-effect solution for both 40G to 40G transmission and 40G to 10G transmission. 8-fiber MTP trunk cables and 8-fiber MTP-LC harness cable are already provided in the market. There are also rack designed 8-Fiber MTP breakout panels for 40G to 10G applications.

MTP-LC-harness-cable MTP-LC-harness-cable
MTP-LC Harness Cable MTP-LC 40/100G Breakout Panel

Convert 12-Fiber MTP to 8-Fiber MTP Cabling System

However, most MTP cabling systems are based on 12-fiber or 24-fiber MTP system, especially for backbone cabling. MTP conversion cables are provided in the market which offer conversion between 12/24-fiber MTP and 8-fiber MTP cabling systems. The following shows two types of 8-fiber MTP conversion cables which can provide 12-fiber to 8-fiber MTP conversion and 24-fiber to 8-fiber MTP conversion separately.

24 to 8 fiber MTP conversion cable 12 to 8 fiber MTP conversion cable
1*3 MTP Conversion Cable 2*3 MTP Conversion Cable

If you have already deployed 12-fiber MTP cabling system in your data center, 2*3 MTP conversion cable is suggested to be used. With one end terminated with two 12-fiber MTP cable and the other end terminated with three 8-fiber MTP connectors, 12-fiber to 8-fiber MTP cabling conversion could be achieved, as well as 100% optical fiber utilization in 12-fiber MTP system.

1*3 MTP conversion cable has a 24-fiber MTP cable on one end and three 8-fiber MTP cable on the other end. With this cable, a length of 24-fiber MTP cable can provide three ways of 40G signal dual-way transmission. All the fibers in a 24-fiber cabling system cable be used.


It is clear that the 8-fiber, 12-fiber based and 2-fiber based cabling system will exist for a long term in 40/100G network. 8-fiber MTP cabling system can provide higher optical fiber utilization with lower cost and higher cabling density. If you want to transfer 12-fiber MTP system to 8-fiber MTP system, you can use MTP conversion cables. 8-base MTP system, could be regarded as an additional option for the existing fiber network infrastructure.

Difference Between 100G-QSFP-PSM4, 100G-QSFP-SR4 and 100G-QSFP-LR4

QSFP28 fiber optic transceiver is becoming the preferred solution for 100G network. It has the same outside looking as the 40G QSFP+ transceiver. But it has a 4*25G electrical interfaces which can transmit optical signals up to 100G. The part numbers of the QSFP28 transceivers are usually market as 100G-QSFP-xx. Now there is a wide selection of 100G QSFP28 modules for 100G Ethernet link, including fiber optic transceiver and direct attached cable. Different part numbers of 100G modules are making customers confused. This post will introduce the differences between the three 100G QSFP28 modules: 100G-QSFP-PSM4, 100G-QSFP-SR4 and 100G-QSFP-LR4.


Transmission Mode

It is known that QSFP28 modules generally use four lanes to transmit 100G with each lane supporting 25G. Thus, the transmission method is just like 40G QSFP+ transceiver. 100G QSFP28 SR4, LR4 and PSM4 all use the 4*25 transmission mode. However, both the QSFP28 SR4 and QSFP28 PSM4 use a 12-fiber MTP interface which achieves dual-way 100G transmission over 8 fibers at the same time. QSFP28 LR4 uses a LC duplex fiber optic interface for 100G transmission on two directions at the same time. QSFP28 LR4 transmit optical signals over four different wavelengths around 1310nm with each wavelength carrying 25G optical signal. The wavelength ranges of the four lanes are as following:

  • 1294.53nm-1296.59nm
  • 1299.02nm-1301.09nm
  • 1303.54nm-1305.63nm
  • 1308.09nm-1310.19nm
Transmission Media and Distances

The three modules can support different transmission distances. 100G-SR4 QSFP28 module works over wavelength of 850nm and is used with 12-fiber MTP OM3 or OM4 multimode fiber cables for short transmission distances up to 100m. 100G-LR4 QSFP28 module is suggested to be used with single-mode fiber. It works over 1310nm wavelengths and can transmit 100G signals up to 2km. 100G-PSM4 QSFP28 is also used with 12-fiber MTP fiber cables but the fiber type is single-mode and the transmission distance is up to 500m.


Cabling Structure

The transmission mode of the fiber optic transceiver plays an important role during fiber cabling. 100G-QSFP-SR4 and 100G-QSFP-LR4 are invented for short distance transmission and long distance transmission separately. However, the have different cabling structure. The former requires a multi-fiber cabling structure based on 12-fiber MMF MTP interfaces. While 100G-QSFP-LR4 just required the traditional two-fiber SMF cabling structure. In this case, the conversion between multimode fiber to single-mode fiber would be complex as they used totally different cabling structure. Thus, 100G-QSFP-PSM4 is invented which runs over single-mode fiber, but uses the same cabling structure as 100G-QSFP-SR4. With 100G-QSFP-PSM4, the conversion between multimode and single-mode would save more without changing the existing fiber cabling structure.

100G QSFP28 Transceiver Data Rate Interface Fiber Type Transmission
Wavelengths Cabling Structure
100G-QSFP-SR4 4*25G MTP MMF 70m (OM3);
100m (OM4)
850nm 12-Fiber MTP
100G-QSFP-LR4 4*25G LC SMF 2km 1310nm LC Duplex
100G-QSFP-PSM4 4*25G MTP SMF 500m 1310nm 12-Fiber MTP

The above table listed the basic information of the three modules for your referent. 100G-QSFP-SR4 are suitable for short distance transmission over OM3 or OM4 fiber using 12-MTP fiber cabling system. 100G-QSFP-PSM4 also has a 12-fiber MTP interface but it can support a transmission distance up to 500m over SMF. 100G-QSFP-LR4 is suitable for long transmission distance up to 2km over two single-mode fibers.

Related Article: 40G vs 100G: Which One Is Worth the Investment?