optical rise time
Technical term in computing and optoelectronics; refers to the time required for an optical signal to transition from a low to a high state.
The optical rise time of this fiber optic system is very short.
Compound of 光 (ひかり, 'light') + 立ち上がり (たちあがり, 'rise, rising') + 時間 (じかん, 'time'). A straightforward technical term.