Improving extinction radio in few-mode fiber interferometer with small-mode-area single mode fiber

The comb filters consist of few mode fiber and standard single mode fiber suffer from low extinction radio. Replacing standard single mode fiber with small-mode-area fiber can better the balance excitation in few mode fiber, thus improve the extinction radio. A lab-made small-mode-area single mode fiber was utilized to a commercial few mode fiber and increase the extinction radio from 2.5dB to 6.5dB. The effect of repeat fusion is also presented.