DIN EN 61753-091-3:2005
纤维光学互连器件和无源元件性能标准.第091-3部分:U类单模纤维光学有抽头的循环器.非受控环境
Fibre optic interconnecting devices and passive components performance standard - Part 091-3: Single-mode fibre optic pigtailed style circulators for category U - Uncontrolled environment (IEC 61753-091-3:2004); German version EN 61753-091-3:2004