FIELD: optical engineering. SUBSTANCE: multiplexer is provided with tuning waveguides used for connecting optical waveguide assembly to fiber-optic units in addition to waveguides performing desired functions, desired tuning being attained irrespective of attaining these functions. There is no need in knowing relevant performance characteristics of individual devices; therefore connecting and tuning operations are easy and fast to carry out. According to invention operating wavelength of optical waveguide assembly can be determined by recording wavelength of light emitted by each tuning waveguide. EFFECT: facilitated checkup of optical waveguide assembly for normal operation. 2 cl, 3 dwg
