1. Optical module transmission rate: refers to the number of bits transmitted per second, such as 100M, Gigabit, 10GE, etc.
2. Transmitting optical power and receiving sensitivity of optical module: Transmitting optical power refers to the light intensity at the transmitting end, and receiving sensitivity refers to the light intensity that can be detected. These two important parameters affect the transmission distance. The transmission distance of the optical module is mainly limited by loss and dispersion.
Loss limitation formula: Loss limitation distance = (transmitting optical power receiving sensitivity) / light red attenuation to estimate.
The fiber attenuation is related to the actual fiber selected. Generally, the current G. 652 fiber can achieve 0.5dB/km in 1310nm band and 0.3dB/km in 1550nm band or even better. 50um multimode fiber is 4dB/km in the 850nm band and 2dB/km in the 1310nm band. For 100M and Gigabit optical modules, the dispersion limitation is far greater than the loss limitation, so it can be ignored.
3. The 10GE optical module follows the 802.3ae standard, and the transmission distance is related to the optical fiber type and optical performance of the optical module.
4. The saturated optical power value refers to the maximum optical power that can be detected at the receiving end of the optical module, which is generally -3dBm. When the received optical power is greater than the saturated optical power, it will cause bit errors.
5. Transmission distance:
The transmission distance of the optical fiber module is divided into three types: short-distance, medium-distance and long-distance. －Generally speaking, 2km and below are short distances, 10-20km are medium distances, and 30km, 40km and above are long distances. The transmission distance of the optical module is limited, mainly because the optical signal will have a certain loss and dispersion when it is transmitted in the optical fiber. Loss is the loss of light energy due to the absorption, scattering and leakage of the medium when light is transmitted in the optical fiber. This part of the energy is dissipated at a certain rate as the transmission distance increases. The generation of chromatic dispersion is mainly due to the unequal speed of electromagnetic waves of different wavelengths when propagating in the same medium, which causes the different wavelength components of the optical signal to arrive at the receiving end at different times due to the accumulation of transmission distance, resulting in pulse broadening and inability to distinguish Signal value.
Therefore, users need to select the appropriate optical module according to their actual networking situation to meet different transmission distance requirements.
6. Center wavelength
The center wavelength refers to the optical band used for optical signal transmission. At present, there are mainly three types of central wavelengths of commonly used optical modules:
850nm band, 1310nm band and 1550nm band
850nm band: mostly used for short-distance transmission
1310nm and 1550nm bands: mostly used for medium and long distance transmission
