Switchable multi-wavelength fiber laser based on hybrid structure optical fiber filter

A switchable multi-wavelength fiber laser based on a novel hybrid structure optical fiber filter (HSOFF) is proposed and demonstrated. The HSOFF is consisted of single mode fiber (SMF)-few mode fiber (FMF) with two ellipsoidal structures and FMF-SMF with a core-offset splicing point. Two ellipsoidal structures can effectively excite the high-order modes, then the high-order modes interfere with fundamental mode at the core-offset splicing point. It can be demonstrated that the HSOFF has the comb filter property with the maximum extinction ratio is more than 13 dB while the insert loss is only 9.95 dB. Using HSOFF in proposed laser system, a switchable multi-wavelength fiber laser with stable dual-, triple- and quadruple wavelength lasers can be obtained by adjusting the state of polarization controller, at the same time the lasing wavelength locations also can be switched. The optical signal to noise ratio (OSNR) is larger than 30.68 dB, and this laser exhibits the excellent stability at room temperature.