What is the optical module?
The optical module is composed of optoelectronic devices, functional circuits and optical interfaces, etc. Optical modules are divided into single mode and multimode modules.
The function of optical module is photoelectric conversion. The transmitter converts electrical signals into optical signals, and the receiver converts optical signals into electrical signals. For example, the HDMI over fiber extender we use in life needs to be used with modules.
What is the difference between single mode and multimode?
The wavelength of multimode light is 850nm, and the wavelength of single mode light is mainly 1310nm and 1550nm.
Multimode optical modules can only be used for short-distance transmission (SR) because of the serious inter-mode dispersion.
2. Application scope
Multimode optical modules are mainly used in networks with low transmission rates and short transmission distances, such as lans.
Single mode optical modules are used for long transmission distances and relatively high transmission rates, such as long-distance trunk transmission and man construction.
3. Optical fiber types
The single mode of an optical module refers only to the type of optical fibers. According to the transmission mode of the optical module in the optical fiber, single mode optical fiber and multimode optical fiber can be classified.
Multimode fiber, called MMF, has a fiber diameter of 50/125μm or 62.5/125μm.
Single mode fiber, called SMF, has a fiber diameter of 9/125μm.
4. Light sources
The light source of multimode optical module is light-emitting diode or laser, while the light source of single mode optical module is LD or LED with narrow spectral line.
A single mode optical module uses twice as many components as a multimode optical module. Therefore, the overall cost of a single mode optical module is much higher than that of a multi-mode optical module.
6. Transmission distance
Single mode optical modules are used for long-distance transmission, with the transmission distance reaching 150 to 200km. Multimode optical modules are used for short distance transmission , with the transmission distance up to 5km.
What should you use？
In safety applications, the most common determinant of multimode or single mode is distance. If only a few hundred meters, multimode is preferred because the LED transmitter/receiver is much cheaper than the laser required for single-mode. If the distance is greater than 10km, single mode fiber is the best. Another issue to consider is bandwidth; if future applications may include the transmission of large-bandwidth data signals, then single mode will be the best choice.