Teach you how to distinguish between single-mode and multi-mode optical fibers

Single mode fiber

Single-mode fiber has a thinner core, allowing light to be emitted directly to the center. It is recommended for longer distances.

In addition, single-mode signals lose less distance than multimode. In the first 3,000 feet, multimode fiber may lose 50% of its LED light signal strength, while single-mode only loses 6.25% of its laser signal over the same distance.

The most common determining factor for choosing multimode or singlemode in an application is distance. If it is only a few miles, multimode is preferred because the LED transmitter/receiver is much cheaper than the laser required for singlemode. If the distance is greater than 5 miles, singlemode fiber is best. Another consideration is bandwidth; if the future application may include the transmission of large bandwidth data signals, then singlemode will be the best choice.

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Multimode Fiber

Multimode fiber is a fiber in which light signals travel through multiple paths; usually recommended for distances less than a mile.

The effective distance of multimode fiber from transmitter to receiver is about 5 miles. The available tracking distance is also affected by the type and quality of the transmitting/receiving device; the stronger the light source and the more sensitive the receiver, the greater the distance. Studies have shown that the bandwidth of multimode fiber is about 4000Mb/s.

Single-mode fiber is manufactured to eliminate pulse broadening. Because the core size is very small (7-9 microns), light jumps are eliminated. Focused laser sources are used at 1310 and 1550nm wavelengths. These lasers shine directly into the tiny core and propagate to the receiver without noticeable jumps. If multimode can be compared to a hunting rifle, being able to load many pellets into the barrel at the same time, then single-mode is the rifle and the single beam is like a bullet.

Depending on the mode number of the transmission point, optical fiber can be divided into single-mode optical fiber and multi-mode optical fiber.

The so-called "mode" refers to a beam of light entering the optical fiber at a certain angular velocity.

• Single-mode fiber uses solid laser as light source
• Multimode optical fiber uses light-emitting diodes as light sources.

Multimode optical fiber allows multiple beams of light to propagate in the optical fiber at the same time, thus forming mode dispersion (because each "mode" of light enters the optical fiber at a different angle, the time they arrive at the other end is also different. This feature is called mode dispersion. Mode dispersion technology limits the bandwidth and distance of multimode optical fiber. Therefore, the core of multimode optical fiber is thick, the transmission speed is low, the distance is short, and the overall transmission performance is poor, but its cost is relatively low. It is generally used in buildings or in geographically adjacent environments. Single-mode optical fiber can only allow one beam of light to propagate, so single-mode optical fiber does not have mode dispersion characteristics. Therefore, the core of single-mode optical fiber is relatively thin, the transmission bandwidth is wide, the capacity is large, and the transmission distance is long, but because it requires a laser source, the cost is relatively high.

Optical cable jacket identification: 50/125, 62.5/125 for multi-mode, 9/125 (g652) for single-mode.

The optical fiber can be spliced ​​and then observed with a 100/200x magnifying glass. A small black dot is single-mode, and a larger one with double rings is multi-mode. The fiber core can also be distinguished in the splicer. If the center is empty on the splicer display, it is single-mode, and if it looks like a whole, it is multi-mode.

Simple usage distinction:

Multi-mode is generally used between close places within the park, while single-mode has a longer transmission distance and is generally used in the telecommunications field.

• Multimode optical fiber is the most primitive technology for optical fiber communication. This technology is a revolutionary breakthrough that enables humans to communicate through optical fiber for the first time.
• With the development of fiber optic communication technology, especially the development of laser technology and people's urgent need for long-distance, large-volume communication, people have found a better fiber optic communication technology - single-mode fiber optic communication.
• Digital optical transceivers use video uncompressed transmission technology to ensure real-time, non-delayed transmission of high-quality video signals and ensure high-definition and pure color images. This transmission method has a large amount of information data. Optical transceivers with more than 4 channels of video all use data streams of more than 1.25G bit/s for transmission. The data stream of 8 channels of video is as high as 1.5G bit/s.