PURPOSE: To reduce the loss, that means, the attenuation of signal light caused at compound optical functional parts and to reduce a cost by thinning the thickness of a polarizer being one of the parts constituting the compound optical functional parts.

CONSTITUTION: As for the compound optical functional parts provided with a polarization multiplier (polarizing beam splitter) 3 coupling first exciting light H2 and second exciting light H3 whose polarizing directions are mutually orthogonally crossed, a short wavelength transmitting filter 2 transmitting and reflecting the exciting light and a signal wave and an optical isolator 8 provided between the filter 2 and an optical fiber 11 outputting the signal light: an optical path provided with the isolator 8 is made to be a convergence and divergence system by providing a lens 12 between the isolator 8 and the filter 2 and the optical paths other than it are made to be a collimator system.