An optical signal transmission apparatus (1) for a rotating antenna comprising a plurality of optical modulators (6) arranged for receiving a respective plurality of analog RF signals (5) and for modulating a respective plurality of optical signals therewith to produce a plurality of modulated analog optical signals (8). A plurality of opto-electrical converters (14) each converts a respective modulated analog optical signal (13) into an analog electrical signal. The plurality of optical modulators (6) are rotationally coupled in optical communication with the plurality of opto-electrical converters (14) via an optical rotary joint (10) including a reversion prism.