Views: 0 Author: Site Editor Publish Time: 2022-12-13 Origin: Site
2020 is the first year for 5G to be commercially available. At present, 25G optical modules have also been used in the construction of 5G signal base stations. Among them, 25G CWDM optical modules have a high market prospect in 5G forward transmission. Compared with other 25G gray light modules, 25G color optical modules can save more optical fiber resources, thus effectively saving the total cost of operators.
As early as 2019, China Telecom published the technical requirements for passive color light coarse wavelength division multiplexing equipment for 5G forward transmission. Among them, China Telecom selected the central wavelength range of the 25G coarse wave splitter module on the AUU side as 1271, 1291 and 1311 nm, and the pull ring color code was half color, while the central wavelength range of the 25G coarse wave splitter module on the DU side was 1331, 1351 and 1371 nm, and the pull ring color code was full color. Because the working environment of 5G pre transmission is relatively variable, 25G SFP28 CWDM needs to meet the temperature range of industrial grade and expansion grade.
The transmission range of 25G SFP28 CWDM optical module formulated by China Telecom is 10km and 15km, but the common 25G SFP28 CWDM is 10km. Next, we will introduce the relevant parameters of 25G CWDM SFP28.
25G SFP28 CWDM uses 1270nm-1370nm (interval 20nm) CWDM DML laser and PIN receiver, or 1470nm-1570nm (interval 20nm) CWDM EML laser and APD receiver. Its receiving and transmitting channels are equipped with CDR circuits, and the maximum rate is up to 25.78Gbps.
The core optical components of 25G SFP28 CWDM optical module are TOSA and ROSA, and the core electrical chip is CDR chip. In the design, the Driver chip and CDR chip use the same chip. MCU mainly realizes chip configuration and module working status monitoring through I2C bus. MCU adjusts the bias current by software design, and adjusts the output light by querying the temperature compensation table.
MCU acts as host and slave respectively, and realizes bus communication through I2C serial port. The average optical power is controlled by using MCU internal algorithm and loop control circuit to adjust the digital quantity. When the output light becomes stronger, the backlight current detected by the PD will become larger, and it will be compared with the initial value of the input current set by another through the internal comparator to reduce the driving current, thereby reducing the average optical power; On the contrary, if the light emission becomes weak, the backlight current becomes smaller, and after passing through the comparator, the driving current will increase, increasing the average optical power. In this way, the average optical power output by the laser is kept stable. The optical modules provided can support the digital diagnosis function (DDM), which can effectively help users monitor various parameters of the optical module in real time, such as temperature, received optical power, transmitted optical power, etc.
