Tag Archives: LC connectors

Serial Transmission vs. Parallel Transmission

We know that in data centers and server farms, when peripherals are attached to a computer, a physical cord is required to send signals back and forth. In this case, the processor can communicate with these devices and send data to them. Communication occurs when the computer sends electronic pulses to the peripheral or vice-versa. Basically, there exist two primary types of digital data transmission: serial transmission and parallel transmission. Then, is there any difference between these two methods of data transmission? How to apply them in data center connectivity? This is what exactly we are going to discuss.

Serial Transmission and Parallel Transmission Overview

For each and every data transfer, the same protocol should be applied to the emitter and the receiver. It enables them to have the same level of information and to know the transfer speed of the data. There are numerous protocols though, and all protocols rely on these two transmission methods: serial transmission and parallel transmission.

serial transmission vs. parallel transmission

Serial Transmission

In serial transmission, bits are sent sequentially on the same channel (wire), one bit at a time. In this way, it reduces costs for wire but also slows the speed of transmission. Also, for serial transmission, some overhead time is needed since bits must be assembled and sent as a unit and then disassembled at the receiver. Serial transmission can be either synchronous or asynchronous.

Parallel Transmission

In parallel transmission, multiple bits (usually 8 bits or a byte/character) are sent on different channels (wires, channels) simultaneously within the same cable, or radio path, and synchronized to a clock. Parallel devices can transfer data in words of one or more bytes at a time. Consequently, there is a speedup in parallel transmission bit rate over serial transmission bit rate, and the cost increasing parallelly since multiple wires cost more than a single wire. As the cable gets longer, the synchronization timing between multiple channels becomes more sensitive to distance. Unlike serial transmission, parallel transmission is considered synchronous.

Transmission Methods Applied in Data Centers

We know that both serial transmission and parallel transmission take a seat in data center connectivity, but in different situations and applications. In the following parts, we will illustrate it in details.

Serial Transmission for 10G Network

Serial transmission approach is usually employed in 10G fiber connectivity where the data are sent sequentially. A duplex fiber pair that consists of one dedicated transmission fiber and one dedicated reception fiber creates the 10G channel to complete the data circuit. Typically, serial connectivity is achieved by using a duplex LC connector. The LC connector is the most commonly deployed interconnect in data centers, especially for high-density network applications.

serial transmission for 10G connectivity

Parallel Transmission for 40G Network and Above

Currently, it’s still not feasible yet possible to adopt a single duplex fiber for beyond 10G network. Although, the technical advancements in serial transmission have raised the limit to 25G, 40G network and above demands for parallel transmission since it can transport more data and achieve higher speeds. For example, parallel transmission achieves the 40G speed by combining four 10G duplex fiber pairs to create a 40G channel. A 100G channel would include ten 10G duplex fiber pairs, and so on. The same principle applies for 120G network and higher.

parallel transmission for 40G and beyond

However, parallel transmission principles 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 parallel transmission, MPO/MTP connectors are used to achieve connectivity. They either house 12 or 24 fibers (6 or 12 duplex fiber pairs). This connectivity option finds itself a better place in data centers because it can take advantage of low-cost lasers and multi-mode cables. Equipment designed for speeds of 10G or less has two-strand, duplex fiber ports for serial transmission, while 40G and 100/120G equipment has 12- and 24-strand MPO/MTP fiber ports for parallel optics transmission.

Conclusion

As the basic digital data transmission approaches, serial transmission is often used in 10G connectivity or data transfer with great distances. While for 40G and beyond or short distance transmission, 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.

Know Enough About Fiber Connectors?

As there exists a wide range of splice options for fiber network available on the market, selecting the right connector for your application can sometimes be tough and confusing. While choosing the fiber connector, various factors like cost and availability should be considered, which naturally lead to even less thought goes to connector itself. Since each connector has its own unique design as well as merits and demerits, it can pose a significant influence on deployment speeds and costs in the long run. So before making your decision, you’d better have an overall understanding of fiber connectors, and this is what we will talk about.

Fiber Connectors Overview

In this part, we will introduce some fiber connectors that are commonly used in the network applications. The following diagram directly explains the differences among them in performance.

Name Mating Cycles Ferrule Size Typical Insertion Loss (db) Application Features
SC 1000 2.5 mm Ceramic 0.25-0.5 Mainstream, Reliable, Fast deployment, Field fit
LC 500 1.25 mm Ceramic 0.25-0.5 High density, Cost effective, Field fit
FC 500 2.5 mm Ceramic 0.25-0.5 High precision, Vibration environments, Field fit
ST 500 2.5 mm Ceramic 0.25-0.5 Military (legacy), Field fit
MTP/MPO 1000 6.4*2.5 mm molded 0.25-0.75 High density, Aggregate networking, Fast deployment
SC Connector

SC connector was one of the first connectors presented on the market following the advent of ceramic ferrules. It has a push-pull coupling end face with a spring loaded ceramic ferrule. Initially intended for Gigabit Ethernet networking, it became increasingly popular as manufacturing costs came down. The SC connector has held a dominated position in fiber optics for over a decade with only the ST rivaling it. And it still remains the second most common connector for polarization maintaining applications. The SC is ideally suited for datacoms and telecoms applications including point to point and passive optical networking.

SC fiber connectors

LC Connector

Considered to be the modern replacement of the SC connector, LC connector is also a push-pull connector, but it utilizes a latch as opposed to the SC locking tab and with a smaller ferrule it is known as a small form factor connector. LC connector shares huge popularity in datacoms and other high-density patch applications. And its small size and latch feature make it an ideal alternative for densely populated racks and panels. Since LC compatible transceivers and active networking components have been introduced, LC connector is likely to continue to grow steadily.

LC fiber connectors

FC Connector

FC connector leads the trend to use a ceramic ferrule, but unlike the plastic bodied SC and LC, it utilizes a round screw-type fitment made from nickel-plated or stainless steel. In spite that the manufacturing and installation of FC connector are much more complex, it’s still an optimum option for precise measuring equipment such as OTDRs. Moreover, FC connector is particularly effective in high vibration environments, ensuring that the spring-loaded ferrule is firmly mated.

FC connectors

ST Connector

ST connector looks much like FC connector, but it uses a bayonet fitment rather than a screw thread. Deployed predominately in multi-mode datacoms, it is most common in network environments such as campuses, corporate networks and in military applications where the quick connecting bayonet had its advantages at the time. However, it cannot be terminated with an angled polish, which limits use in single mode fiber and FTTH applications.

ST connectors

MTP/MPO connector

MTP and MPO connector falls into the category of multiple fiber push-on/pull-off connector. It is larger than other connectors since it can support up to 24 fibers in a single ferrule. It is currently extensively used in high density patch environments such as data centers, both at single mode and multi-mode wavelengths. MTP/MPO connector is often supplied with a fan-out assembly at the opposing end (such as LC, SC FC etc.). This allows the operator to change channels simply by re-patching the fanned-out side of the cable.

MTP/MPO connectors

Conclusion

Getting to know the differences between various types of fiber connectors simply contribute to the primary stage of selecting the right one. And when it comes to the planning process of fiber deployments, the differences can be much more clearly. So, make sure to invest enough time to select the right fiber connector, which will do you a good return in the long run.