All-Fiber Nanosecond Gating for Time-Resolved Spectral Analysis

We demonstrate the addition of time gating to a standard optical spectrum analyzer (OSA) operating in the spectral region ~1.06μm . This is accomplished by opening for 7 ns the optical input to the OSA with an electrically driven poled fiber in a Sagnac loop. The sequential interrogation with nanosecond resolution of the reflection from three fiber Bragg gratings along a piece of fiber allows distinguishing the spectral peaks created with a minimum separation of 85 cm. The passive extinction ratio of this device is >40 dB and returns to >40 dB from >23 dB on a 35-ns time scale directly after time gating.