A label-free optical fiber biosensor based on a Mach-Zehnder interferometer for real-time bovine serum albumin (BSA) concentration detection has been proposed and experimentally demonstrated. An air microcavity has been fabricated by means of splicing a segment of microfiber between two single mode fibers (SMFs) with appropriate offset such that it acts as a microfluidic channel, where external media can directly interact with the guided light. Experimental results show a high sensitivity of -15.56 nm/(mg/mL).
A novel multi-wavelength fiber laser was achieved simultaneously tunable and switchable outputs of wavelength spacing with an Erbium-doped fiber amplifiers (EDFA) based on nonlinear polarization rotation (NPR) effect. We described and proved the tunable of wavelength spacing in detail by using different length of polarization maintaining fiber (PMF). The switchable outputs was simply realized an interchange among multi-wavelength operations by adjusting the polarization controller (PC) in the ring cavity. The tunable and switchable multi-wavelength fiber ring laser could stably operate in room temperature, and the peak power variations in each wavelength were measured to be less than 1dB.