Single-mode OS2 fibre uses a 9-micron core and laser-grade transceivers to carry signals over distances measured in kilometres with minimal attenuation — suited to campus backbones, inter-building links, and WAN connections. Multi-mode fibre (OM3: 50-micron, optimised for 10G at 300 m; OM4: 10G at 400 m; OM5 for short-wave WDM) uses LED or VCSEL sources and is more cost-effective for building risers and data-centre interconnects under 500 metres. The choice is determined by distance, bandwidth requirement, and transceiver budget — all assessed during our site survey.