Description of the problem

Q:

We often find in the description of the single board that the optical module is I-x or Ie-x ( x stands for different rates), which stands for intra-local communication, and it should be a multimode optical port, but the wavelength is often not 850nm but 1310nm, so what are the main differences between 1310nm single-mode optical modules and 1310nm multimode optical modules.

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Processing

A:

According to the principle of multi-mode and single-mode division, we can find that the main differences between 1310nm multi-mode optical modules and single-mode optical modules are as follows:

1, single-mode modules generally use LD or spectral lines narrower LED as a light source, coupling components size and single-mode fiber with a good match, the use of single-mode fiber optic transmission can transmit a longer distance.

2、Multi-mode modules generally use lower-priced LED as the light source, coupling parts size and multi-mode fiber with good.

3, different optical modules to send the signal wavelength is 1310nm but the optical power power is different.

4, the extinction ratio of the multi-mode optical module is larger than the single-mode optical module, the refractive index is also different.

Root cause

Multimode fiber is divided into multimode mutant fiber and multimode gradient fiber. The former core diameter is larger, more transmission modes, thus narrower bandwidth, smaller transmission capacity; the latter core in the refractive index with the increase in radius and reduce the modal dispersion can be relatively small, thus wider bandwidth, transmission capacity is larger, the latter are generally applied.

Because of the different transmission speeds of different modes of light in multimode fibers, the transmission distance of multimode fibers is very short. And single-mode fiber can then be used in relay-less optical communication.

In fiber optic communication theory, there are single-mode and multi-mode optical fibers, the difference is:

1, single-mode fiber core diameter is small (about 10m m ), allowing only one mode transmission, small dispersion, working at long wavelengths ( 1310nm and 1550nm ), and the coupling of optical devices is relatively difficult.

2, multi-mode fiber core diameter ( 62.5m m or 50m m ), allowing hundreds of modes of transmission, dispersion, working at 850nm or 1310nm, and the coupling of optical devices is relatively easy.

As for the optical module, strictly speaking, there is no single-mode or multi-mode. The so-called single-mode, multi-mode module, refers to the optical module using optical devices and what kind of fiber with the best transmission characteristics.

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