A radio-on-fiber unit comprising an antenna array including a plurality of antenna elements arranged two-dimensionally and a light modulator array including a plurality of light modulators connected to the plurality of respective antenna elements via electric circuits, wherein the plurality of respective antenna elements are configured to receive a radio signal, and wherein the light modulator array is configured to receive an output of the plurality of antenna elements conveyed by an electrical connection and to receive a signal light on which modulation in accordance with the radio signal is to be performed, and wherein the light modulator array) comprises: a substrate provided in parallel with an antenna array layer where the plurality of antenna elements is provided; a light input unit to input the signal light into the substrate; an optical waveguide through which the signal light input from the light input unit propagates and which is provided in the substrate; an light output unit from which the signal light after propagating through the optical waveguide is output; and a plurality of light modulators provided in the optical waveguide, wherein the plurality of light modulators is arranged with the feeding points of the respective light modulators in corresponding positions of the plurality of antenna elements, wherein the optical waveguide comprises, among the plurality of light modulators, a plurality of linear optical waveguides along the light modulator contained in some line, and wherein the light modulator array, further comprises: a reflection unit to connect two adjacent linear waveguides, thereby the signal light input into the light input unit is output from the light output unit via each linear optical waveguide. wherein the light modulator array is configured to receive an output of the plurality of antenna elements conveyed by an electrical connection and to receive a signal light on which modulation in accordance with the radio signal is to be performed, and wherein the light modulator array) comprises: a substrate provided in parallel with an antenna array layer where the plurality of antenna elements is provided; a light input unit to input the signal light into the substrate; an optical waveguide through which the signal light input from the light input unit propagates and which is provided in the substrate; an light output unit from which the signal light after propagating through the optical waveguide is output; and a plurality of light modulators provided in the optical waveguide, wherein the plurality of light modulators is arranged with the feeding points of the respective light modulators in corresponding positions of the plurality of antenna elements, wherein the optical waveguide comprises, among the plurality of light modulators, a plurality of linear optical waveguides along the light modulator contained in some line, and wherein the light modulator array, further comprises: a reflection unit to connect two adjacent linear waveguides, thereby the signal light input into the light input unit is output from the light output unit via each linear optical waveguide. a substrate provided in parallel with an antenna array layer where the plurality of antenna elements is provided; a light input unit to input the signal light into the substrate; an optical waveguide through which the signal light input from the light input unit propagates and which is provided in the substrate; an light output unit from which the signal light after propagating through the optical waveguide is output; and a plurality of light modulators provided in the optical waveguide, wherein the plurality of light modulators is arranged with the feeding points of the respective light modulators in corresponding positions of the plurality of antenna elements, wherein the optical waveguide comprises, among the plurality of light modulators, a plurality of linear optical waveguides along the light modulator contained in some line, and wherein the light modulator array, further comprises: a reflection unit to connect two adjacent linear waveguides, thereby the signal light input into the light input unit is output from the light output unit via each linear optical waveguide.