A fluorescence spectrum analyzer based on a fiber-optic $Y$-circulator

We consider a method of probe analysis employing fiber-optic a composite $Y$-circulator design for the implementation of laser-induced fluorescence (LIF) spectroscopy diagnostics. The proposed principle of the LIF analyzer is based on spatially separated directed optical beams of excitation and fluorescence radiations. Conditions of the effective $Y$-circulator operation as a passive fiber-optic switch are determined. Experimental investigation of the switched radiation losses is performed. An example of using the proposed analyzer for LIF diagnostics of biological media is presented.