Performance Analysis of Photonic Vector Modulation Techniques for Multi-Gb/s Wireless Links

Broadband access networks evolution towards 10-Gb/s user connectivity will foster the evolution of the photonic and wireless technologies needed to implement multi-Gb/s wireless links. In particular, provision of data rates in excess of 1 Gb/s using wireless technologies is limited by currently available electrical technologies due to the required bandwidths and frequencies of operation in the millimeter-wave (mm-wave) band. Microwave photonic techniques and technologies have shown a clear potential to overcome these limitations. In this paper, the detailed study of a photonic vector modulator (PVM) architecture and its performance limitations are presented. The PVM architecture is based on direct baseband modulation and dispersion induced quadrature condition. The limitation of this architecture is the presence of a local oscillator (LO) component in the generated mm-wave spectrum which limits the system dynamic range. To overcome this limitation, a third continuous-wave (CW) laser is used to remove the unwanted LO component by properly adjusting its wavelength and emitted power. After presenting the theoretical model, the LO suppression feature is demonstrated experimentally by generating a 1.25-Gb/s QPSK 41-GHz modulated carrier. The two options (with and without LO carrier) are compared in terms of relevant performance parameters.