Detailed Analysis of SFP Optical Module Interface Indicators and Components

The rate of SFP+ optical module is : 10G SFP+ optical transceiver is an upgrade of SFP. SFP has been widely used in Gigabit Ethernet and 1G, 2G, 4G fiber optic channels. SFP+ designed enhanced electromagnetic shielding and signal protection characteristics to adapt to higher data rates, and formulated new electrical interface specifications.

Interface indicators of SFP optical module

• Output optical power: refers to the output optical power of the optical source of the optical module transmitter.

• Received optical power: refers to the received optical power of the optical module receiver.

• Receiver sensitivity: refers to the minimum received optical power of the optical module under certain rate and bit error rate conditions. Generally, the higher the rate, the worse the receiver sensitivity, that is, the larger the minimum received optical power, and the higher the requirements for the optical module receiver device.

• Saturation optical power, also known as optical saturation, refers to the maximum input optical power when maintaining a certain bit error rate (10-10～10-12) at a certain transmission rate.

It should be noted that under strong light irradiation, the photodetector will exhibit photovoltaic current saturation phenomenon. When this phenomenon occurs, the detector needs a certain amount of time to recover, and the receiver sensitivity will decrease. The received signal may cause errors and may cause the receiver detector to be easily damaged. In use, try to avoid exceeding its saturation optical power.

It should be noted that for long-distance optical modules, since their average output optical power is generally greater than their saturation optical power, please pay attention to the length of the fiber optic cable used by users to ensure that the real-time received optical power of the optical module is less than its saturation optical power, otherwise it may cause damage to the optical module

Components of SFP optical module

SFP optical module consists of the following components: laser: including TOSA transmitter and ROSA detector board IC. External accessories include: shell, base, PCBA, pull ring, buckle, unlock component, and rubber plug component. In addition, for easy identification, the module parameter type is generally distinguished by the color of the pull ring. For example, the black pull ring is a multimode, the wavelength is 850nm; the blue one is a module with a wavelength of 1310nm; the yellow one is a module with a wavelength of 1550nm; the purple one is a module with a wavelength of 1490nm, and so on.

Relationship between SFF, GBIC, and SFP optical modules

SFP is the abbreviation of Small Form-factor Pluggables, which is a plug-and-play optical module with a small form factor. SFP can be regarded as a plug-and-play version of SFF, and its electrical interface is a 20-pin gold finger. The data signal interface is essentially the same as the SFF module. SFP optical module also provides an I2C control interface, which is compatible with standard optical interface diagnostics. SFF and SFP do not contain parts, only provide a serial data interface, and place CDR and electronic dispersion compensation outside the module, making small size and low power consumption possible. Due to thermal limitations, SFF/SFP can only be used for short-distance, medium-distance, and long-distance applications at speeds of 2.5Gbps and below.

Now the highest speed of SFP optical module can reach 10G, mostly using LC interface. It can be simply understood as an upgraded version of GBIC. The volume of SFP optical module is half that of GBIC optical module, and can configure more than twice the number of ports on the same panel. In terms of other functions, the basic function of SFP module is the same as that of GBIC. Therefore, some switch manufacturers refer to SFP optical modules as miniaturized GBICs.