Numerical Aperture (NA) is a measurement that expresses the light-gathering ability of an optical fiber. It is related to the acceptance angle, which is the maximum angle to the fiber axis at which light will be accepted and propagated through the fiber. In other words, it is the sine of half the angle over which a fiber can accept light. In relation to cables, the NA of a fiber will determine how much of the light from the source is being transmitted through the cable.
For example, if the NA of a fiber is 0.2, that means that the fiber will only accept light from angles within 0.2 radians of the fiber axis. This is because the sine of 0.2 is about 0.2. Therefore, the higher the NA of a cable, the better the performance of the cable in terms of light transmission. This is because a higher NA means that the fiber can accept light from a greater angle, which in turn means that more of the light from the source is being transmitted through the cable.
In addition, the NA of a fiber is also directly related to the fiber’s core diameter. Generally, the larger the core diameter, the higher the NA. This is because a larger core diameter means that the fiber can accept light from a wider angle. Therefore, if you are looking for a cable with good light transmission, you should look for a cable with a larger core diameter and a higher NA.
Overall, NA is an important factor to consider when selecting a cable for your application. It is related to the acceptance angle of the fiber, which in turn is related to the core diameter. The higher the NA, the better the performance of the cable in terms of light transmission.