Digital coherent technology for optical fiber and radio-over-fiber transmission systems

The digital coherent technology is a renaissance of coherent optical communication in mid 80s, underpinned by a powerful digital signal processing (DSP) owing to the rapid progress in silicon complementary metal oxide semiconductor (CMOS) LSI technology. It can offer unprecedented capability of equalizing not statically but dynamically the impairments of optical signals as well as the frequency carrier offset between the light sources at the transmitter and the local oscillator in optical fiber transmission systems. On the other hand, the digital coherent technique has also brought a new paradigm to radio-over-fiber (RoF) transmission systems. It is particularly powerful for high bit rate millimeter-wave (MMW) and terahertz RoF systems using IQ-modulation format because signal impairments caused both in optical fiber and free-space propagation can be jointly equalized. In this talk, current status and the future perspective of digital coherent technology for optical fiber and RoF transmission systems will be reviewed. Besides, we will introduce our proposed highly resilient optical and wireless dual transmission system based upon RoF technology upon the failure of optical fiber link.