What Is Polarization Maintaining Fiber Patch Cable?

The inherent advantages of light are doomed to play an important role in human history. With the booming of human technology, the development of optical fiber communication has made new progress. In the field of optical fiber communication, the most familiar thing for us should be fiber optic cable and patch cable. However, in addition to conventional fiber patch cable, there are some special kinds of fiber patch cable that we have never known. Today, let’s talk about a kind of special optical fiber patch cable: polarization maintaining fiber patch cable (PM Fiber).

Polarization Maintaining Fiber Patch Cable

Polarization Maintaining Fiber Patch Cable

What Are Polarization and Polarization Maintaining Fiber Cable?

If we want to understand PM fiber, we must first understand what polarized light is. Light is a kind of electromagnetic wave. It consists of an oscillating electrical field and a magnetic field. Its properties can be described by studying its electrical field, although we can also describe light and its effects in terms of magnetic field. Light waves can vibrate in many directions. When light vibrate in one direction, such as up and down in a single plane, they are called polarized light. When light vibrate in multiple directions, such as up/down and left/right, on more than one plane, they are called unpolarized light.

What Is Polarization Maintaining Fiber Patch Cable?

The polarization of light propagating in the fiber varies gradually in an uncontrolled (wavelength-dependent) manner, depending on its temperature and any bending of the fiber. Special optical fiber is needed to achieve optical performance, which is affected by the polarization of light passing through the optical fiber. Many systems such as fiber interferometers and sensors, fiber lasers and electro-optic modulators also suffer from polarization-dependent losses (PDL) that may affect system performance. In order to solve this problem, polarization maintaining fiber patch cable was developed. It is a special type of single mode optical fiber. Ordinary single mode optical fiber can carry random polarized light. However, the polarization maintaining fiber patch cable is designed to propagate only one polarization of the input light.

Types of Polarization Maintaining Fiber Patch Cable?

There are many kinds of polarization maintaining fiber patch cable, which support different data rates and are suitable for various connector types. According to different classification standards, polarization maintaining fiber patch cable can be classified into various types.

  • Classified according to connector type – The ends of polarization maintaining fiber patch cable are sealed by optical fiber connectors. The connectors commonly used at both ends of PM fiber are FC, SC, LC and ST. Therefore, according to the connectors at both ends, there are many different types of PM fiber, such as LC-FC, SC-FC or FC-FC polarization maintaining fiber patch cables.
  • Classified according to fiber type – PM fiber is made up of polarization maintaining fiber. To ensure the polarization of the input and output light in PM fiber, we use several different shapes of rods, and the resulting fibers are sold under trademarks such as “Panda” and “Bow-tie”.

Applications of Polarization Maintaining Fiber Patch Cable

Polarization maintaining fiber patch cable is also commonly used in telecommunications for the connection between source lasers and modulators. Because modulators require polarized light as input. Furthermore, it is used for special applications, such as quantum key distribution, interferometry and optical fiber sensing. But, they are rarely used for long haul transmission because Polarization Maintaining Fiber Patch Cable are more expensive and more attenuated than single-mode fibers.


In today’s optical fiber communication systems and applications, it’s necessary to understand polarization. And, it’s important to understand how to characterize and process polarization effects in order to maximize the performance of systems involving polarization sensitive devices. Polarization maintaining fiber patch cable is based on high-precision butt joint technology to maintain polarization. You can contact FS.COM, if you want to know more information.

SFP+ Cable: How Much Do You Know?

Recently, the popularization of SFP+ cable has become the trend of data center interconnection. However, what is SFP+ cable? To this end, different SFP cable manufacturers have different presentations and descriptions. Here, let’s discuss the exact meaning and classification of SFP+ SFP+ cables.

What Is SFP+ Cable

SFP+ cable refers to the high-speed cable that are equipped with transceiver (without components, can only transmit signals) at both ends. It was widely used in storage area networks, data centers and high-performance computer connectivity. SFP+ cable supports 10G Ethernet, 8G Fiber Channel, 10G FCoE, 10G InfiniBand and various unified architecture link applications.

SFP+ Cable Types

Today, several types of SFP+ cables are accessible, such as SFP+ direct attach cables, and SFP+ active optical cables. In additional, there are two types of SFP+ direct attach copper cable: SFP+ active direct attach copper cable and SFP+ passive direct attach copper cable.

SFP+ Direct Attach Copper Cable

Also known as twinax cable, SFP+ direct attach copper cable is used in rack connections between switches and servers, containing a high-speed copper cable and two SFP+ copper modules. With the low cost and low power budget, the SFP+ direct attach copper cable has the advantage of high-end port density, configurability, and utilization. The cables are thermally removable and insertable, meaning that you can remove and replace them without turning off the switch or breaking the switch function.

SFP+ cable: SFP + Direct Attach Copper Cable

Figure 1: SFP+ Direct Attach Copper Cable

SFP+ Active Copper Cable: To enhance the signal and driven from the port without additional power requirements, SFP+ active direct attach copper cable assembly contains a low power circuit in the connector. As a low-cost alternative to optical transceivers, the active version is often used in row or intermediate row data center architectures for interconnection distances up to 15 meters.

SFP+ Passive Copper Cable: As a high performance connectivity solution, SFP+ passive direct attach copper cable assembly supports 10GB Ethernet and Fibre Channel applications. Besides, it has higher reliability and fewer components with lower cost.

There is no real visual way to distinguish the difference between active and passive twinax cables. The active or passive twinax cable assembly can be directly connected to the SFP+ shell. Active twinax cables have active electronic components in the SPF+ housing to improve signal quality; passive twinax cables are only a straight line “wire” without active components. Typically, a twinax cable less than 5 meters in length is passive and a cable longer than 5 meters is active, but this is a general rule, depending on the supplier. Most manufacturers will have some kind of marking on the cable connector head, which will mark the cable as active or passive.

SFP+ Active Optical Cable

With a full-duplex construction, SFP+ active optical cable can transmit data at 10Gb/s. In additional, it can support a single transmission between 1 and 100 meters. Supporting single-channel and high-speed data link applications, SFP+ active optical cable is fully compatible with Fibre Channel, and Ethernet. As a cost-effective interconnect solution, SFP+ active optical cable has the edge of high speed, longer cable length, and enhanced signal integrity.

SFP+ cable: SFP+ Active Optical Cable

Figure 2: SFP+ Active Optical Cable


It is no doubt that SFP+ cables have many advantages after a brief introduction to the three SFP+ cables. First, SFP+ cables are interchangeable and hot-pluggable, which means that when the device is working too early, you don’t have to completely shut down the system to replace the device. Second, it is compatible with other protocols such as Ethernet, Fibre Channel, and PON standards, maintaining the speed and integrity of the signal as it travels over long distances. Third, the SFP+ cable is not too expensive, making it more and more popular. FS.COM can provide you with the reasonably priced and high quality cables. By the way, we also has very excellent SFP modules. If you have any need or question about SFP+ cables, please contact us.