The development trend of micro optical cables: smaller, faster, and stronger

Smaller, faster, better  – this has been the trend for fiber optic cables for many years. With the invention of dispersion compensation technology and people's attention to issues such as improving fiber reliability, "faster and better" was undoubtedly the goal advocated in the 1990s.

　　In recent years, the industry has focused on reducing the footprint of fiber networks. The trend toward smaller cables and hardware arguably began around 2005 with the development of short bend radius (RBR) fiber by fiber vendors. Soon after these new optical waveguide designs were introduced, an international standard was developed to regulate them, namely ITU G657. Subsequently, these “knottable” fibers began to allow for smaller cable designs as the fiber’s tolerance to macro and micro bends increased.

　　Macro and micro benefits of small bend radius optical fiber

　　Macrobending is a simple phenomenon that is easy to understand. ITU G657 specifies specific optical loss specifications at specific bend radii for macrobend performance. However, some argue that the improved performance of microbends comes from the primary property of small bend radii, which allows for smaller, higher performance cabling. One way to actually analyze the difference between macrobends and microbends is to imagine wrapping a fiber around your finger and measuring the fiber loss (macrobend), pressing a piece of sandpaper against the fiber and measuring the corresponding loss (microbend loss), and then comparing the difference between the two.

　　The underlying optical phenomena that cause signal loss in these two cases are very different. When a cable is exposed to cold temperatures, the materials in the cable will tend to contract, exerting forces along the length of the fiber. This force can cause microbending of the fibers within the cable. For example, improved microbend tolerance for small bend radius fiber can certainly help the cable withstand larger temperature changes.

　　Fiber optic cable manufacturers around the world are taking advantage of this property of small bend radius fiber. Their "wish" is to develop fiber optic cables that can be used like copper cables - durable, small, practical, easy for anyone to handle, and without damaging the fiber. To achieve this goal, people have also innovated the materials used in the manufacturing process of fiber optic cables. The improved bending performance of small bend radius fiber has promoted the use of new materials and new manufacturing technologies in fiber optic cable manufacturing, making the cables smaller and lighter. Solving these problems together can produce a new generation of smaller and more flexible fiber optic cables.

　　A major factor in the smaller radius of fiber optic cables is patch cords and other direct-attach cable. Besides the obvious benefit of being able to fit more cable in the same space, smaller cable size also allows for faster airflow because the cable takes up less duct space. This benefit will become even more important as suppliers of active electronic components attempt to miniaturize and consolidate electronic cabinets. Heat is becoming a significant issue in these electronic cabinets. Typically, people consider airflow along the copper cables (which themselves generate heat). But as equipment cabinets become smaller and hotter, all aspects of airflow become important.

　　A new wave of smaller direct-attach cables and patch cords has begun

　　Smaller than you think

　　This phenomenon may not be so obvious now, but for every unit reduction in the diameter of a circular cable, the space occupied by the cable (the area of ​​the circle) will be reduced accordingly. Therefore, a small reduction in the diameter of the cable may mean a significant reduction in the space occupied. For example:

　　So, comparing a typical 2.0-mm cable to a 1.2 mm diameter cable, it is clear that while the cable diameter has not been halved, the recommended amount of cable that can be installed in the same space (1 square inch) is almost 3 times as much!

For a more intuitive explanation, let's take a bundle of 24 jumper cables as an example. We can see the following differences:

　　Dimensional comparison of 1.2-mm and 2.0-mm bundled cables

　　In the image above, you can see that in the 1.2-mm diameter cable example, the same amount of fiber takes up much less space. Likewise, even when comparing a 1.6-mm diameter cable to a 1.2-mm diameter cable, more than twice as much cable can be installed in the same space!

　　Stronger

　　The next question you might ask is about the length of smaller cables. In the late 2000s, Telcordia released Revision 2 to the widely used GR-409 direct attach cable standard. Revision 2 included a sub-category called “small” cables that allowed for the production of weaker cables to the GR-409 standard. Revision 2 reduced the installation tensile strength for so-called small packages, allowing cables to withstand an installation load of 9 pounds (40N) instead of the standard installation load of 22 pounds (100N). At the time, it was widely believed that the reduction in strength was necessary to produce smaller and smaller cables. A cable rated for a 9-pound tensile load would require installers to be more cautious and careful to avoid cable damage than a cable rated for a 22-pound load.

　　However, some current cables based on small bend radius cables actually use materials/designs/methods that result in smaller cable sizes that exceed the original 22 lb tensile installation load specified in GR-409.

　　For example, 1.2-mm direct attach cables are now available that support a rated installation load of 30 lb. Compared to a small-diameter rated 2.0-mm cable, this means that the new 1.2-mm diameter cable is three times stronger and takes up only one-third the space.

　　As a result, data center managers and others will soon be able to install significantly smaller cables than ever before without having to choose the smaller package of GR-409, which compromises cable strength. Be careful when you receive a quote for GR-409 cable to make sure you understand the specifications of the cable you are purchasing. Many people are not aware of this distinction.

　　What's your next question? If the size of the optical cable can be reduced, then the size of the hardware can also be reduced. Expect that in the near future, we can see hardware with smaller size than ever before, which will enable higher density and more compact cabling management while ensuring network reliability.