What is the SFP module?

What is the SFP module?

With the rapid development of photo-communication,The metal medium communication such as coaxial cable and network cable is gradually being replaced by optical fiber medium in our work and life.The optical module is one of the core components of the optical fiber communication system.

The composition of the SFP module

The SFP is a general term for a variety of module categories
including: an optical transmitting module,an optical receiving module,an optical transceiver module, and an optical forwarding module.

Today, What we call the SFP usually refers to an optical transceiver module.The SFP work at the physical layer, which is the bottom layer in the OSI model.Its function is photoelectric conversion. Convert optical signals into electrical signals, and electrical signals into optical signals.The SFP usually consists of Transmitter Optical Sub-assembly,Receiver Optical Sub-assembly,Functional Circuit,Optical (electrical) interface.
                                                                         

At the transmitting terminal, the driver ic processes the original electrical signal, and then drives the LD or LED to emit modulated optical signals.

At the receiving terminal, the optical signal converted into electrical signal by the light detection diode after it come in,and the electrical signal output after passing through the preamplifier.

Basic indicators of the SFP module

The basic indicators of the SFP mainly include the following:

Output optical power

Output optical power is the power of the light source at the transmitting terminal of the SFP.It means the intensity of light, in W or mW or dBm. In communication, we usually use dBm to express optical power.The unit is W or mW or dBm.In communication, we usually use dBm to express optical power.

Maximum receiving sensitivity

Receiving sensitivity is the minimum optical receiving power of the SFP under a certain rate and bit error rate.Unit: dBm.In general,The higher the rate, the worse the receiving sensitivity,That is, the greater the minimum received optical power,and the higher the requirements for the receiving terminal device of the SFP.

Extinction ratio

Extinction ratio is one of the most important parameters used to measure the quality of the SFP.It is the ratio of the optical power P1 when the laser transmits all "1" codes to the optical power P0 when all "0" codes are transmitted.The value of the extinction ratio is not the bigger the better, but the better if the extinction ratio meets the 802.3 standard.

Light saturation

It is saturated optical power,The maximum input optical power when maintaining a certain bit error rate (10-10 ~ 10-12) at a certain transmission rate.