The JBX42439 FC/APC to FC/UPC duplex singlemode fiber patch cable represents professional-quality network infrastructure for mission-critical applications. This 40-meter cable is engineered to deliver exceptional performance in telecommunications, data centers, and high-speed networking environments where signal integrity is paramount. **Technical Excellence:** Constructed with 9/125 singlemode fiber and G.657.A1 glass composition, this cable delivers superior optical performance. The ≤0.35dB insertion loss (with typical performance at 0.15dB) ensures minimal signal degradation, while the ≥20dB return loss specification provides exceptional reflection characteristics. Attenuation rates of 0.25 dB/km at 1310 nm and 0.35 dB/km at 1550 nm comply with industry standards for long-distance signal transmission. **Construction & Durability:** The 1.8mm outer diameter provides optimal flexibility without compromising durability. OFNR (Optical Fiber Nonconductive Riser-rated) jacketing ensures compliance with building codes and fire safety requirements, making it suitable for vertical cable runs and in-wall installations. The robust plastic accessories and premium connector assemblies withstand repeated connections and environmental stressors. **Connector Configuration:** The FC/APC (angled polished connector) to FC/UPC (ultra-polished connector) configuration with Type A to B crossover polarity is the industry standard for duplex communications, enabling reliable bidirectional signal transmission. This polarity arrangement ensures proper signal routing in matched networking systems. **Compliance & Standards:** Fully TAA (Trade Agreements Act) compliant and RoHS/ELV certified, this cable meets government and environmental requirements. Manufacturing from Taiwan, US, and China facilities ensures consistent quality and availability. Attenuation testing follows ANSI/TIA/EIA-455-171-A-2001 standards, guaranteeing reliable performance verification. **Practical Advantages:** The distinctive yellow jacket aids in quick network identification and organization. Available in custom lengths for specific installation requirements. Ships from multiple US distribution centers (Danville CA, Fort Worth TX, Beaufort SC) with free standard shipping on orders exceeding $99. The 90-day limited warranty provides confidence in your investment. **Applications:** Ideal for connecting fiber optic transceivers, switches, and network equipment in data centers, telecommunications facilities, and enterprise networks. The 40-meter length accommodates medium to large facility installations while maintaining signal quality. Perfect for backbone connections, inter-switch links, and critical network infrastructure.