Electrical spectrum synthesis technique using digital pre‐processing and ultra‐broadband electrical bandwidth doubler for high‐speed optical transmitter

Abstract

Proposed is an electrical spectrum synthesis technique that converts low‐speed signals to a high‐speed signal using transmitter‐side digital signal processing (DSP) and an ultra‐broadband electrical bandwidth doubler. The transmitter‐side DSP converts a high‐speed signal to low‐speed upper and lower sideband signals, down‐ and up‐converts the low‐speed signals into baseband signals, and adds and subtracts the in‐phase and the quadrature components of the baseband signals. The digital pre‐processed low‐speed signals output from digital‐to‐analogue converters are multiplexed to the high‐speed signal by the bandwidth doubler, which consists of analogue multiplexers designed and fabricated using in‐house indium phosphide heterojunction bipolar transistor technologies. A 120 GBaud quadrature phase shift keying signal has been successfully generated by using the proposed technique as a demonstration of a high‐speed optical transmitter.