Optimization of wideband multimode circulators for improved multimode fiber-based sensing

Optical systems for fluorescence or spectroscopy may employ fiber optic couplers to improve the system’s robustness and sensitivity. Common limitations of multimode fiber optic couplers include back-reflections occurring at the fiber-air interfaces and auto-fluorescence, causing background noise. We present different strategies to reduce noise contribution in a Wideband Multimode Circulator (WMC) by implementing connectors with reduced back-reflections, using high-angle polishing (reduction of 21 dB) or anti-reflective coating (reduction of 16 dB), and testing a low autofluorescence packaging (reduction of 4.2 dB). These improved features allow for increased SNR.