Applications of Serial Transmission and Parallel Transmission in Network

In the age of the Internet, we are not unfamiliar with data communication, which refers to the process of transferring data signals between two or more devices. Basically, there are two methods used to transmit data signals: serial transmission and parallel transmission. To put it simply, serial transmission sends data bits one after another over a single channel, while parallel transmission sends multiple data bits at the same time over multiple channels. Both of them are commonly used in network applications and this article will focus on applications of serial transmission and parallel transmission in network.

serial transmission and parallel transmission

Application of Serial Transmission

As in serial transmission, bits are sent sequentially on the same channel (wire), one bit at a time, the cost for wires is low but the speed of transmission is slow. In 10G network, serial transmission is usually utilized. For example, a duplex LC fiber that consists of one fiber for transmitting 10G data signals and one fiber for receiving 10G data signals is typically used to completer the data link. In high-density network applications, it is easy to find LC duplex patch cables deployed to connect different network devices.

serial transmission for 10G network

Application of Parallel Transmission

In parallel transmission, multiple bits (usually 8 bits or a byte/character) are sent on different channels (wires, channels) simultaneously over the same cable. Compared with serial transmission, parallel transmission has a faster bit rate, and the higher cost since multiple wires cost more than one single wire. Parallel transmission is usually used in 40G and 100G network because it can transfer more data signals and achieve higher speeds. For example, MTP trunk cable, terminated with MTP/MPO fiber connector on each end, can be used to achieve the connectivity. In 40G networking applications, a 12-fiber MTP fiber connector is used: 10G is sent along each channel or fiber strand in a transmit and receive direction, and 8 of the 12 fibers are used to provide 40G parallel transmission; in 100G network applications, a 24-fiber MTP fiber connector is used: 10G is sent along each channel or fiber strand in a transmit and receive direction, and 20 of the 24 fibers are used to provide 100G parallel transmission.

parallel transmission for 40G network

Note: Parallel transmission can also be applied to 25G duplex fiber pairs to reach even higher speeds or reduce the number of fibers required at a given speed. For instance, a 100G channel would require four 25G duplex fiber pairs instead of ten 10G duplex fiber pairs.


In network applications, serial transmission is often used in 10G connectivity, while for 40G and 100G connectivity, parallel transmission is preferred. Hope you could acquire some useful information from the article, and have a better understanding of these two data transmission methods. In addition, you can find fiber optic cables mentioned above in FS.COM. Some other fiber optics are also available here, such as 24-fiber MPO MTP loopback, MTP to LC breakout cable, MPO fiber patch panel and so on. If you want to know more details, please visit our site.

Talk About MPO Connector

As high-density cabling in data center has become a trend, network components characterized by saving space become popular among data center managers. There is a type of multi-fiber connector—MPO connector, which is now widely used around the world. MPO connector not only allows for more fiber ports per unit of rack space, but also satisfies the need of parallel optical interconnections for multi-fiber connection. This article is going to introduce the detailed information about MPO connector.

Structure of MPO Connector

Each MPO connector has a key on one side of the connector body. When the key sits on top, this is referred to as the key up position. On the contrary, when the key sits on bottom, we call it key down position. Each of the fiber holes in the connector is numbered in sequence from left to right, and we call these fiber holes as positions, or P1, P2, etc. Besides, as shown in the following figure, there is a white dot on the connector body to designate the position 1 side of the connector when it is plugged in. Generally, MPO connector is pin and socket connector, which requires a male side and a female side. From the figure below we can find that MPO male connector has pins, while MPO female connector has no pins.

MPO Connector Types

Originally designed for ribbon fiber, MPO connector is available in 12, 24, 48 and 72 fiber variants. Generally, there are two popular MPO connector types: 12 fiber MPO connector and 24 fiber MPO connector. The following part will introduce these two types of MPO connectors to you.

12 Fiber MPO Connector

In theory, the 12 fiber MPO connector can deliver 6x10G transmit fibers and 6x10G receive fibers. However, it actually only delivers 40G since the transceivers and the equipment are only capable of supporting 40G data rates. That means 33% fibers of the connector are not being used, only 8 fibers are being used at the transceiver while the other 4 fibers are just spares. From the figure below, you can have a better understanding of this.

12 fiber MPO connector

Accommodating 12 fibers, the 12 fiber MPO connector provides up to 12 times the density, thereby it can save space in the rack. It is the first connector which has enough repeatable performance to be accepted in data centers. If you build a backbone with a 12 fiber MPO connector, basically you can put any connection on the end to be future proofed, such as LC, SC, etc. Thus most of data centers choose 12 fiber MPO connector cabling in the backbone and MPO-LC harnesses cable connecting to equipment like switches and servers. Many equipment today still has LC transceiver interface, therefore the harness is required to convert from MPO in the backbone to LC at the port.

24 Fiber MPO Connector

With development of data centers, many data center managers come across the problem that the promoted 12 fiber MPO connector no longer matches the requirement of the data centers. Every equipment applied in the data center is either 40G (8 fibers) or 100G (24 fibers). 12 is not divisible by 8, but 24 is. If you combine 2×12 fiber MPO connectors in the backbone, you can connect 3×8 fiber MPO connectors with zero fiber waste at the switch. The 24 fiber MPO connector has similar performance to the 12 if not exactly the same.

24 fiber MPO connector

As shown in the above figure, the 24 fiber MPO connector has two rows of 12 fibers. And this additional row of fibers require an increase in the spring force to push all of those fibers together, actually double what you need for 12. With the same size as a 12 fiber MPO connector, the 24 fiber MPO connector has double the amount of fibers and reduces the amount of cable required at the back end because a 24 fiber cable is only marginally bigger than a 12 fiber cable. Moreover, when you can just have 1×24 fiber MPO connector converting to 3×8, there is no need to combine 2×12 fiber MPO connectors to make 3×8. The 24 fiber MPO connector can also satisfy the demand for 100G data rates over a single connector and 20 fibers are used for 100G (10x transmit and 10x receive).


MPO connector delivers the optical, mechanical and environmental performance that service providers need to expedite the addition of fiber capacity and to support higher data-rate services. It plays an important role in the high-density cabling solutions. I hope after reading this article, you can have in-depth understanding of MPO connector.