Micro-optical cable and its development trend

Smaller, faster and better - this is the development trend of optical cable over the years. With the invention of dispersion compensation technology and people’s concern for improving the reliability of optical fiber, “faster, better” is undoubtedly the goal advocated in the 1990s.

In recent years, the industry has been focusing on reducing the space occupied by fiber optic networks. It can be said that with the development of small bend radius (RBR) fibers by fiber optic suppliers around 2005, the trend towards smaller fiber optic cables and hardware has begun to emerge. Shortly after these new fiber designs emerged, people developed an international standard to regulate, namely ITU G.657. Later, because of the increasing tolerance of macro-bending and micro-bending of optical fibers, these "knotted" fibers are beginning to allow for smaller fiber cable designs.

Macroscopic and Microscopic Effects of Small Bend Radius Fibers

Macrobending is a simple phenomenon that is easy to understand. ITU G.657 specifies special optical loss specifications at special bend radii for macrobending performance. However, some claims that the improved microbend performance comes from the main feature of a small bend radius that enables smaller, higher-performance wiring. One way to actually analyze the difference between macrobends and microbends is to imagine wrapping an optical fiber around your finger, measuring fiber loss (macrobending loss), pressing a piece of sandpaper over the fiber and measuring the corresponding The loss (microbend loss) then compares the difference between the two.

In both cases, the fundamental optical phenomena that cause signal loss are very different. When the cable is exposed to a low temperature environment, the material in the cable will tend to shrink, applying force along the length of the fiber. This force will cause microbending of the optical fiber in the cable. For example, an increase in the microbending tolerance of small bend radius fibers will undoubtedly help the cable withstand large temperature changes.

Global cable manufacturers are using this characteristic of small bend radius fibers. Their "wish" is to develop optical cables that can be used like copper cables - robust, small and practical, anyone can easily operate without damaging the fiber. In order to achieve this goal, people have also made innovations in the materials used in the manufacture of optical cables. The bending performance of the small bend radius fiber is improved, which promotes the use of new materials and new manufacturing technologies in the manufacture of the optical cable, thereby making the cable smaller in size and lighter in weight. Together these problems can be solved to create a new generation of fiber optic cables that are smaller and more flexible.

One of the primary uses of small bend radius cables is patch cords and other direct fiber optic cables. In addition to the obvious benefit of being able to install more fiber optic cables in the same space, the smaller size of the fiber optic cable can also increase the air flow because the cable takes up less space in the pipeline. With active electronics suppliers trying to miniaturize and consolidate electronic cabinets, the importance of this advantage will become even more apparent. In such electronic cabinets, heat has gradually become an important issue. Usually, people will consider the airflow along the copper cable (the copper cable itself will generate heat). However, as the equipment cabinet becomes smaller and hotter, all aspects of the airflow become very important.

The new wave of smaller, direct-attached cables and jumpers has already begun.

Smaller than your imagination

This phenomenon may not be so obvious now, but for each unit diameter reduction of a round cable, the space occupied by the cable (circular area) will be reduced accordingly. Therefore, a slight reduction in cable diameter can mean a significant reduction in space. for example:

Jumper diameter Vertical cable management space

Number of optical fibers per inch

3.0 mm 46

2.0 mm 102

1.6 mm 142

1.2 mm 285

Therefore, comparing a typical 2.0mm cable with a 1.2mm cable, it is clear that although the cable diameter is not reduced by half, the recommended number of cables that can be installed in the same space (1 square inch) is almost The original 3 times!

For a more intuitive explanation, take a bundle of optical cables with 24 jumpers as an example. As we can see, the following is the difference between the two:

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24 fiber bundles, 1.2mm diameter fiber optic cable 24 fiber bundles, 2.0mm diameter fiber optic cable

Comparison of 1.2mm and 2.0mm Bundled Fiber Cables

In the figure, you can see that in the 1.2mm diameter fiber example, the same amount of fiber takes up much less space. Similarly, even comparing a 1.6mm diameter fiber optic cable to a 1.2mm diameter fiber optic cable, the number of optical cables that can be installed in the same space is twice the difference!

At the same time stronger

The next question that everyone may ask is about the length of the smaller cable. In the latter part of the first decade of the 21st century, Telcordia issued revision 2 for the widely used GR-409 direct-attached fiber standard. Revision 2 includes a subcategory called “Small” fiber optic cable that allows the production of lower-strength fiber optic cable in accordance with the GR-409 standard. Revision 2 reduces the requirement for so-called small package mounting tensile strength, allowing the cable to withstand a 9-pound (40N) installation load instead of a 22-pound (100N) standard installation load. At the time, it was widely believed that reducing strength was necessary to produce smaller and smaller optical cables. Compared to fiber optic cables rated at 22 pounds, optical cables with a rated tensile load of 9 pounds require installation personnel to be more careful to avoid fiber optic cable damage.

However, current materials/designs/methods that are based on cables with a small bend radius are actually smaller, which exceeds the original 22-pound tensile installation load specified in GR-409.

For example, a 1.2mm direct-attached cable is now available and can support a 30-pound rated mounting load. Compared to the nominal small 2.0mm fiber optic cable, this means that the new fiber optic cable with a diameter of 1.2mm is three times stronger and only takes up one third of the space.

So, soon, data center managers and others will be able to install fiber-optic cables that are much smaller than before, and will not passively choose the small package of the GR-409, which will not reduce the cable strength. Be cautious when receiving quotes for GR-409 fiber cables to ensure that you understand the specifications of the fiber optic cable that will be purchased. Many people do not understand this difference.

What questions will you ask next? If the cable size can be reduced, the hardware size can also be reduced. It is expected that in the near future, we can see that hardware with smaller size than ever before can realize higher density and more compact wiring management while ensuring the reliability of the network.

Ryan Chappell is TE Connectivity's global business development manager responsible for fiber cable business. He started working in the optical fiber industry in 1994. Ryan has held various positions in various companies, including R&D, engineering, marketing, and sales of fiber optic cables, fiber optics, and other fiber optic components.