Single-Multi-Single Mode Structure Based Band Pass/Stop Fiber Optic Filter With Tunable Bandwidth

We present a simple, efficient and easy to fabricate single-multi-single mode (SMS) fiber-based tunable bandwidth optical bandpass/bandstop filter. The device exploits the transmission characteristics of an SMS structure near its critical wavelength. Using both temperature and strain tuning, we show that the device can be switched between band pass to band stop modes and that the filter bandwidth in each mode can be dynamically tuned. We present a theoretical analysis of the observed behavior and obtain excellent agreement with the experimental observations.