Basic concept of optical module

1.Laser category

A laser is the most central component of an optical module that injects current into a semiconductor material and emits laser light through photon oscillations and gains in the cavity. At present, the most commonly used lasers are FP and DFB lasers. The difference is that the semiconductor material and the cavity structure are different. The price of the DFB laser is much more expensive than the FP laser. Optical modules with transmission distances up to 40KM generally use FP lasers; optical modules with transmission distances ≥40KM generally use DFB lasers.

2.Loss and dispersion

Loss is the loss of light energy due to the absorption and scattering of the medium and the leakage of light when the light is transmitted in the fiber. This part of the energy is dissipated at a certain rate as the transmission distance increases.The dispersion is mainly caused by the unequal speed of electromagnetic waves of different wavelengths propagating in the same medium, which causes different wavelength components of the optical signal to reach the receiving end at different times due to the accumulation of the transmission distance, resulting in pulse broadening and thus inability to distinguish signals value.These two parameters mainly affect the transmission distance of the optical module. In the actual application process, the 1310nm optical module generally calculates the link loss at 0.35dBm/km, and the 1550nm optical module generally calculates the link loss at .20dBm/km, and calculates the dispersion value. Very complicated, generally only for reference.

3.Transmitted optical power and receiving sensitivity

The transmitted optical power refers to the output optical power of the light source at the transmitting end of the optical module. The receiving sensitivity refers to the minimum received optical power of the optical module at a certain rate and bit error rate. The units of these two parameters are dBm (meaning decibel milliwatt, the logarithm of the power unit mw, the calculation formula is 10lg, 1mw is converted to 0dBm), which is mainly used to define the transmission distance of the product, different wavelengths, transmission rate and The optical module’s optical transmit power and receive sensitivity will be different, as long as the transmission distance can be ensured.

4.Optical module life

International unified standards, 50,000 hours of continuous work, 50,000 hours (equivalent to 5 years).

The SFP optical modules are all LC interfaces. The GBIC optical modules are all SC interfaces. Other interfaces include FC and ST.