Multimode fiber spectrometer with scalable bandwidth using space-division multiplexing

Abstract

Multimode fiber (MMF) spectrometers suffer from the resolution-bandwidth trade-off due to the limited spatial speckle information used for spectral recovery. We demonstrate a design of an MMF spectrometer with scalable bandwidth using space-division multiplexing. A multicore fiber (MCF) is used to integrate with the MMF. The spatial degrees of freedom at the input are exploited to provide the independent speckle pattern, thus multiplying the spatial information and scaling the bandwidth. We have experimentally achieved 30 nm bandwidth with 0.02nm resolution at wavelength 1550 nm, only using 3 cores of a 7-core fiber and a single MMF. An efficient algorithm is developed to reconstruct the broadband sparse and dense spectrums accurately. The approach can enhance the operating bandwidth of MMF spectrometers without sacrificing the resolution, and simultaneously ensure the system complexity and stability.