Definition of single-mode optical module and multi-mode optical module
The optical module is divided into single-mode optical module and multi-mode optical module according to the different types of applicable optical fibers. The optical fiber wavelength of the single-mode optical module is 1310nm, 1550nm and WDM wavelength. The fiber wavelength of the multi-mode optical module is 850nm or 1310nm, and currently the 850nm fiber wavelength is the main one.
In the optical module, single-mode and multi-mode refer to the transmission mode of the optical fiber in the optical module, so they need to be used with single-mode optical fiber and multi-mode optical fiber respectively. The diameter of single mode optical fiber is 9/125μm, multimode optical fiber is 50/125μm or 62.5/125μm
The difference between single-mode optical module and multi-mode optical module
Single-mode optical modules and multi-mode optical modules are not only different in the type of optical fiber, but also in other aspects.
Transmission distance
Single-mode optical modules are suitable for long-distance transmission, and the transmission distances of single-mode optical modules with different fiber wavelengths are also different. The single-mode optical module with a fiber wavelength of 1310nm has large loss but small dispersion during transmission, and the transmission distance is generally within 40km. The single-mode optical module with a fiber wavelength of 1550nm has small loss but large dispersion during transmission, and the transmission distance is generally more than 40km, and the farthest can be directly transmitted without a repeater to 120km. Multi-mode optical modules are suitable for short-distance transmission, and the transmission distance is generally within 300~500m.
Scope of application
Single-mode optical modules are suitable for networks with long transmission distances and high transmission rates, such as metropolitan area networks, passive optical fiber networks, etc. The multi-mode optical module is suitable for networks with shorter transmission distances and lower transmission rates, such as data center computer rooms, local area networks, etc.
Light source
The light source used by single-mode optical module and multi-mode optical module is different. The light source used by single-mode optical module is light-emitting diode or laser, while the light source used by multi-mode optical module is LD or LED.
Power consumption
The power consumption of a single-mode optical module is greater than that of a multi-mode optical module. However, the power consumption of optical modules is mainly determined by factors such as the parameters, models and brands of the optical modules, so single-mode and multi-mode optical modules with different parameters, models and brands will also have the same power consumption.
Price
Compared with multi-mode optical modules, single-mode optical modules use more components and use more expensive laser light sources, so the price of single-mode optical modules is higher than that of multi-mode optical modules.
How to choose single-mode optical module and multi-mode optical module
Single-mode optical modules and multi-mode optical modules are different in transmission distance, application range, light source, power consumption and price, so the selection needs to be based on the actual application environment. For example, a metropolitan area network with a long transmission distance should choose a single-mode optical module, and a local area network with a short transmission distance should choose a multi-mode optical module. To put it simply, multi-mode optical modules should be selected in a network environment with many nodes, many connectors, many detours, and a large amount of connectors and couplers, while single-mode optical modules should be selected in long-distance trunk lines.
Common questions in the use of single-mode optical modules and multi-mode optical modules
Can single-mode optical modules be connected to multimode optical fibers?
It can be connected for short-distance transmission. When a single-mode optical module is connected to a multimode optical fiber, the optical fiber is transmitted in a multi-mode mode in the single-mode optical module, so the dispersion is relatively large, and it can only be used for short-distance transmission, and the transmission performance cannot be guaranteed. Therefore, the single-mode optical module is best connected to a single-mode fiber, not to a multi-mode fiber.
Can a multimode optical module be connected to a single mode optical fibers?
Multimode optical modules cannot be connected to single mode optical fibers, because not only will there be a large loss, but it may even fail to communicate. Because the light divergence angle of the multi-mode optical module is large, the diameter of the single mode fiber is small, and the farther the transmission distance is, the greater the attenuation of the signal may be. The signal may have been attenuated before reaching the transmission distance.
Can single-mode optical modules and multi-mode optical modules be used together?
In theory, when the signals of single-mode optical modules and multi-mode optical modules can be received by the receiver and the optical power is within the receiving range, they can be mixed. For example, the 100M LX single-mode optical module and the 100M FX multi-mode optical module can be mixed, because they can receive signals from each other, and the received optical power is within the same range. However, this is not recommended for optical modules above 1G, because the wavelength of multimode optical modules above 1G is mainly 850nm, and there are too many things to pay attention to when using them.
Conclusion
In order to avoid link failure, when selecting single-mode optical modules and multi-mode optical modules, it still needs to be determined according to the actual application situation. More importantly, it is best not to mix single /multi mode optical fibers and single/multi mode optical modules.