3/14/2022, Optical Fiber Online News, OFC2022 News, on the afternoon of March 8, US Pacific Time, at OFC's Tu3F (optical transmission for 5G) session, senior expert Zhang Dezhi from China Telecom Research Institute made a presentation on "Integrated CWDM for 5G Fronthaul". Demonstration and experimentation of novel semi-active systems with circulators". The report authors also include Du Zhe, Cheng Ming, Jiang Ming from China Telecom Research Institute, Liu Xinfeng from Fiberhome and Li Xin from Etern Optoelectronics.

Zhang Dezhi pointed out in the report that considering the needs of 5G and 4G hybrid networking, in addition to the six wavelengths from 1271nm to 1371nm, the traditional solution needs to use another six CWDM wavelengths from 1511nm to 1611nm. The technical challenges of this expansion lie in high dispersion and high complexity (the introduction of EA modulated lasers), and the industrial chain behind the lasers corresponding to new wavelengths also needs to be cultivated. To this end, China Telecom Research Institute, together with Fiberhome and ETERN, designed only 6 standard CWDM wavelengths (1271nm to 1371nm), and realized a single-system 6-channel fronthaul link by inserting an optical circulator into the multiplexer and demultiplexer ability. ETERN Company provided some key components for this program.

The paper concludes by summarizing the results of the joint research and realizing a real-time CWDM semi-active system with circulators based on 6 CWDM wavelengths, supporting 25Gbps per channel. Real-time monitoring of uplink and downlink channels is achieved through system-integrated PDs, and protection switching functions are implemented based on optical switches. The laboratory and field experimental data are provided in this paper, indicating that the system can meet the reliability and operation and maintenance requirements of fronthaul applications.

The new semi-active system integrating CWDM and circulator is referred to as the CC scheme in China. It is said that the products based on this scheme have participated in the telecom centralized acquisition test. The invited report of the China Telecom Research Institute at OFC will promote the further recognition and application of the scheme on a global scale.