- Our E-2000® HRL category 0. 1 dB is a singlemode APC 8° fiber optic connector with solid-ceramic ferrule for all singlemode applications with particularly high requirements on optical transmission quality and protection of the connector ferrule, e. It ofers a spring-loaded shutter mechanism that protects the ferrule end-face from scratches and dust while also preventing potentially eye-damaging laser radiation. The connector is color-coded for easy identification and uses a push-pull locking mechanism for se ure connections. Here the key practical guidance for installation.