A lithium niobate bandpass modulator for optical subcarrier transmission systems

A novel lithium niobate bandpass optical modulator with a three section phase reversal travelling wave coded electrode structure has been developed for optical fibre system applications. The device exhibited a switching voltage of 8.5 V at a peak response of 11.2 GHz, and an upper and lower-3 dB optical modulation response of 15 GHz and 7.1 GHz, respectively. The results obtained agreed closely with theoretical models of the modulation response of coded electrode devices. A new packaging technology has been developed which allows the bandpass modulator to be housed in a fully hermetic environment without deteriorating its intrinsic high speed performance. For applications in the 11 GHz to 14 GHz band initial studies indicate that bandpass lithium niobate modulators are superior to conventional broadband lithium niobate modulators as a result of a lower required switching voltage and therefore lower required RF drive power