Single-mode patch cables are designed for high bandwidths and long-distance applications. For example, today they're used for all long-distance telephone lines.
The BLACK BOX range of single-mode patch cables is specially developed for long-haul telecommunication and wide-area data networks. Quality is particularly important for single-mode cable as the core is only 9 µ. Its center must be very well aligned for a reliable connection.
But the most important quality measurement in a single-mode patch cable is return loss. Yesterday's standard of -40 dB loss is no longer acceptable for today's demands. A minimum of -50 dB - or -60 dB for APC finish - is required.