Two Microwave Vector Signal Transmission on a Single Optical Carrier Based on PM-IM Conversion Using an On-Chip Optical Hilbert Transformer

A new microwave photonic link to simultaneously transmit and detect two microwave vector signals modulated on a single optical carrier based on orthogonal modulation and optical Hilbert transformation is proposed and demonstrated, for the first time to the best of our knowledge. In the proposed system, two microwave vector signals are phase and intensity modulated on a single optical carrier at a dual-parallel Mach-Zehnder modulator and transmitted over a single-mode fiber (SMF). At the receiver, the optical signal is applied directly to a photodetector (PD) to recover the microwave vector signal that is intensity modulated and the second microwave vector signal is recovered by using an on-chip optical Hilbert transformer (OHT) to perform phase-modulation to intensity-modulation conversion followed by photodetection at a second PD. An experiment is performed. The transmission of a 16QAM and a QPSK signal with a total data rate of 2.4 Gb/s over a 10-km SMF is implemented. The performance of the transmission in terms of error vector magnitude, bit error rate, and energy efficiency is evaluated.