To address the issue of modal crosstalk, it is necessary to utilize multiple-input multiple-output digital signal processing (MIMO-DSP) at the receiver or use only a limited number of circularly symmetric modes to achieve ultra-high-speed transmission, which means there is still some way to go before this technique can be put into practical application [9; 10]. In contrast, for the CDM transmission technique, the inter-core crosstalk can be easily suppressed by designing the structure of MCFs [11]. Besides, the CDM transmission system can be made directly compatible with existing intensity modulation/direct detection (IM/DD) or coherent transceivers through fan-in/fan-out (FIFO) devices, which means it exhibits excellent implementation potential in both next-generation short-reach and long-haul optical transmission systems [12; 13; 14]. For the large-scale implementation of the CDM transmission approach in existing optical transmission networks, MCF-related maintenance techniques such as low-loss connection schemes and high-performance FIFO devices are crucial issues to be addressed. Over the past few years, multiple MCF-related maintenance techniques have witnessed remarkable progress. For low-loss connection approaches, ultra-low-loss fusion splicing techniques utilizing advanced automatic core misalignment algorithms and portable MCF connectors enabled by precise micromachining have been experimentally demonstrated, promoting the field implementation of MCFs in long-haul transmission scenarios [15; 16]. Regarding FIFO devices, a wide variety of low-loss FIFO devices have been reported by improving processing approaches such as using micro-structured preform and reduced-cladding graded index fiber, which can support CDM transmission with multiple types of MCF [16; 17; 18]. Besides, integrated multi-core erbium-doped fiber amplifiers (MC-EDFAs) with core pumping have also been reported, based on which an ultra-long-haul transmission over more than 12,000 km 4-core fiber has been achieved [19]. Real-time CDM transmission utilizing commercial 400 Gb/s optical transport network (OTN) transceivers has also been demonstrated [14]. These remarkable breakthroughs promote the maturity and field implementation of MCFs, and experimental MCF cables have also been field-deployed and trialed multiple times to further explore the application scenarios of MCFs. For example, a 114 Pbit/s-km transmission using three vendor-installed 60 km 4-core fiber spans has been reported, demonstrating the implementation feasibility of 4-core fibers in the actual outdoor environment with multiple fusion splicing and connector connections [20]. Besides, an integrated communication and sensing system over field-deployed 7-core fiber cable has also been demonstrated, which can monitor the surrounding traffic while maintaining large-capacity CDM communication [21]. Thanks to the inherent advantage of MCFs with multiple fiber core channels, various types of service, such as advanced MIMO distributed acoustic sensing (DAS) and classical/continuous variable quantum key distribution (CVQKD) co-existence transmission systems, have also been reported [22; 23]. MCFs also have the potential to be compatible with other advanced transmission technologies such as high-stability optical time and frequency transmission systems [24]. However, for implementation in long-span transmission scenarios such as unrepeated optical interconnections, unrepeated field trials over more than 100 km MCF cable utilizing commercial 800 Gb/s OTN transceivers have not been reported so far, with the main restriction being the performance of MCF cable and OTN equipment. Exploring the high-speed single-span transmission capabilities of MCFs is of great significance, especially for data center interconnections and submarine cable communication systems.