There are two types of fiber optic cabling - multimode and singlemode. As most of you probably know, multimode cabling is shorter in length than singlemode cabling, so singlemode is suitable for outdoor long-distance fiber optic applications, while multimode is the main choice for data center and interior building applications.

As everyone knows, because of the original bandwidth test capability of single-mode fiber, its popularity in shorter route applications has become higher and higher, and more and more professional technicians are encountering the installation of single-mode and multi- Mode fiber problem. But it turns out that not everyone understands the process differences between the two fiber types. Let’s take a deeper look below.

What is the pattern?

In the optical fiber data transmission industry, the term "mode" is used to describe the method of propagation of an optical signal within the fiber's sandwich glass core—that is, the mode is the way light travels. Thus, in a single-mode light source, light travels in one path; in a multimode fiber, light travels in several paths.

You can imagine it like this: as you descend from the top of the water slide, you keep jumping and descending between the two partitions of the slide. Every perspective in the entire descent is a pattern. The propagation method of light in the core of a multimode fiber is the same as that described above. The light hits the laminated glass at a viewing angle, and then the reflective surface returns home, while traveling the length of the fiber core. Why is it not easy for light to go straight out of the fiber core? First, the light shines on the laminated glass with a small viewing angle, which makes the laminated glass reflect the light like a bathroom mirror. Second, there is an insulating layer outside the core. In order to better keep the light inside the fiber core, the insulating layer has different refractive index characteristics, and this performance parameter determines the amount of reflection or mapping when the light directly enters the raw material.

In contrast, in a single-mode fiber, light travels along parallel lines, and due to the small core size of a single-mode fiber (about one-tenth the core of a multimode fiber), the light does not bounce easily.

Bandwidth Limit Latency

Why is single-mode fiber suitable for higher bandwidth testing and longer distances? Pushing light in a single mode clears the differential signaling mode delay (DMD), which is a major factor in limiting the bandwidth of multimode fiber.

When propagating in multiple modes in a multimode fiber, some eyes travel along the fiber core, while other light travels close to the core insulation. Propagating modes at the edges on both sides are called higher-order modes, and those propagating near the core of the fiber are called lower-order modes. The propagation rates of high-order and low-order modes are different, and DMD is the error in propagation time.

The smaller the DMD, the lower the spread of the light single pulse over time and the higher the bandwidth. The greater the time difference between the single pulses, the more likely the signal receiver will not be able to distinguish the single pulses. DMD is immediately related to spacing - increasing with increasing fiber length. This is why multimode fiber has a much shorter spacing specification than single mode fiber, which is up to 500 meters long, while single mode fiber can be up to 10 kilometers in length.