Bend Radius

What is the Bend Radius?

The bend radius is the radius in which a cable can be bent without getting damaged. Here we consider the exact center of the cable, i.e. the neutral fiber. The smaller this radius, the more durable the material must be. The whole thing behaves similarly to the human body. The smaller I want to make myself, the more flexible my spine needs to be. If I go beyond my maximum bend, it hurts. Worst case scenario, something breaks. The same applies to the cables.

The minimum bend radius (Min. Bend Radius) is the radius below which a fiber cannot be bent. The radius chosen for the carrier depends on the cable with the largest diameter. It is important that users always make sure that the correct radius for the carrier is considered in the calculations. Ideally, use the largest possible radius, falling below which can quickly lead to failure.

Why Fiber Cable Bend Radius is Important?

1. Protect the Integrity of the Optical Fiber

Fiber optic cables experience bending loss when bent, resulting in a decrease in the optical signal power. If the bend radius is too small, the bending loss can increase significantly, severely impacting the signal transmission quality.

2. Ensure Reliability and Long-term Stability

Excessive bending can accelerate the fatigue process of the optical fiber, shortening the lifespan of the fiber optic cable. Adhering to the recommended bend radius helps to improve the reliability and long-term stability of the fiber optic cable.

3. Comply with International Standards

There are various international standards and requirements regarding the bend radius of fiber optic cables. Conforming to these standards helps ensure the safety and compatibility of the fiber optic cable.

4. Protect the Integrity of the Optical Fiber

The optical fiber core is the critical component of a fiber optic cable, typically only around 125 microns in diameter. An excessively small bend radius can subject the fiber core to high stress and deformation, potentially causing the fiber to break or the optical properties to degrade.

General Rules and Recommendations for Selecting the Radius

Do not exceed the manufacturer's recommended minimum radius - but the maximum radius is optimal. Basically, cables with flexible specifications that move must be supported so that the connection points are not mechanically stressed and a sharp bend is avoided. If this is achieved by a loop, the cable must be provided with a bend radius of at least 10 times the diameter of the cable. The larger the radius, the less stress is exerted on the cables, which ensures a longer service life. It should be noted that the minimum bend radius is partially based on a temperature range for the bending. Particular care should be taken when the ambient temperature reaches or exceeds this temperature for the cable.

This is especially true for cryogenic applications where thermoplastic cables tend to stiffen when exposed to cold. Rigid cables can increase the radius of the cable carrier and lead to mechanical errors. It is recommended to use a cable with a PUR or TPE jacket at low temperatures and/or to consult the manufacturer for recommendations on bend radii. For space-constrained applications, the cable carrier radius must be less than the recommended minimum bend radius for the filling pack. This is not ideal, but if it cannot be avoided, cables designed specifically for low bend radius installations should be used.

Where are Cables with a Tight Bend Radius Used?

The areas of application for cables with tight bend radii are diverse. They are particularly needed in applications where flexible and dynamic movements must be carried out in the smallest possible installation space. For example, they are used in the semiconductor and assembly industry, the automation industry, as well as in the automotive and banking sectors. New application possibilities arise in automatic doors for vehicles and trains as well as in automatic self-service food vending machines and the packaging industry.