All-fiber spectrometer based on coreless fiber

We demonstrate two types of all-fiber speckle spectrometer. One of the spectrometers is composed by cascading a coreless fiber (CLF) and an all-solid photonic crystal fiber (PCF). Using a 10 cm-long fiber with 20-segment-PCF spliced elements, the spectrometer achieves a resolution of 0.03 nm over a bandwidth from 1540 to 1560 nm. The other spectrometer is realized by using the periodically tapered CLF. A remarkable spectral resolution of 0.03 nm in the near-infrared spectrum can be achieved with a 5-cm long fiber. Our compact spectrometers based on CLF promise picometer-resolution spectroscopy in portable applications, providing a new way for miniature spectrometer systems.