Abstract: One of the primary issues in building a digital mine is to build a high-quality information network with low latency, large bandwidth, and high reliability. Traditional wireless communication technologies such as WiFi and 4G have been unable to meet the new demand of the digital transformation of mines. Starting from the demand for communication networks in digital mines, the necessity and deployment difficulties of 5G technology in underground mines are studied. It is pointed out that the underground 5G networking scheme based on centralized-radio access network (C-RAN) can effectively reduce the deployment requirements and difficulties of 5G networks in underground mines. However, two issues, the high consumption of optical fiber resources and the difficulty in managing dumb resource failures, must be addressed. A digital mine all-optical network system based on 5G C-RAN technology is proposed. The system architecture is introduced from three levels: C-RAN access network, high-speed all-optical network, and intelligent control platform. Key technologies such as semi-active optical network architecture, low-cost wavelength division multiplexing (WDM) high-speed transmission, and intelligent control platform are studied. The system uses direct inspection WDM technology to save optical fiber resources, which can reduce the number of optical fibers used by 91.67%. At the same time, based on semi-active architecture and topping operation administration and maintenance (OAM) technology, it achieves low-cost control and flexible deployment of optical fiber networks. It solves the tight optical fiber resources and optical fiber network management challenges in underground roadways. The experimental results show that the transmission optical power of 12 WDM optical modules with different wavelengths is 3.5 dBm to 5.2 dBm. The reception sensitivity is −16.9 dBm to −19.0 dBm, and the link budget capacity can reach over 21 dB, meeting application requirements. The extinction ratio ranges from 4.7 dB to 5.1 dB, and the eye pattern margin is greater than 17.5%, indicating high signal quality. At a low temperature of − 40 ℃ and a high temperature of 85 ℃, the WDM optical module has some performance degradation in both transmission optical power and reception sensitivity. But it can still meet the transmission requirements of 10 km. Field application results show that the transmission optical power of 12 WDM optical modules with different wavelengths is 3.7 dBm to 5.6 dBm, and the reception sensitivity is −17.9 dBm to −16.3 dBm. The link budget capability of the worst channel is still above 20.2 dB, meeting application requirements.