The JBX42615 20m FC/APC to ST/UPC duplex singlemode fiber patch cable represents the professional standard in optical fiber connectivity. This robust cable assembly combines precision-engineered connectors with high-quality optical fiber to ensure reliable, low-loss signal transmission in telecommunications, data center, and enterprise network environments. **Superior Optical Performance** With a 9/125 singlemode core and G.657.A1 glass fiber specification, this cable delivers exceptional optical characteristics. The measured insertion loss of ≤0.35dB (0.15dB typical) and return loss of ≥20dB meet stringent ANSI/TIA/EIA standards for attenuation testing. Attenuation specifications of 0.25dB/km at 1310nm and 0.35dB/km at 1550nm ensure minimal signal degradation across critical wavelength ranges. **Connector Configuration** The FC/APC to ST/UPC crossover configuration (Type A to B) represents the most common duplex patch cord polarity arrangement, eliminating compatibility concerns in existing network installations. APC-angled connectors on the FC end provide superior return loss characteristics, while UPC connectors on the ST end offer flexibility in mixed-connector environments. **Safety and Compliance** TAA compliance ensures this cable meets government procurement requirements, while RoHS/ELV certification and EU directive 2002/95/EC compliance guarantee environmental responsibility. The OFNR riser-rated jacket provides fire safety ratings necessary for in-building vertical installations and plenum-area applications. **Practical Features** The bright yellow jacket aids in visual identification during complex network installations, reducing configuration errors. At 1.8mm outside diameter with durable plastic accessories, the cable remains flexible for routing through conduits and equipment cabinets. Custom length availability accommodates specific distance requirements without waste or additional splicing. **Support and Availability** Ships from multiple US locations (Danville CA, Fort Worth TX, Beaufort SC) ensuring rapid delivery. Free standard shipping applies to orders exceeding $99, with 90-day limited warranty providing purchase confidence. Available in bulk packaging (10x10x10) for large infrastructure deployments. Ideal for telecommunications professionals, data center technicians, and network engineers requiring reliable singlemode connectivity with proven connector compatibility and superior optical performance.