Towards green optical fiber amplification: distributed parametric amplifier and its applications

Abstract

With the data explosion brought about by smartphones and tables during the past few years, how to keep these ever-increasing data in a stable, fast and green transmission and exchange environment is among the top problems for researchers in the communication field. As the backbone for the modern communication network, optical fiber communication is currently playing a key role in this on-going technology revolution. The optical amplifier is one of the most powerful tools of the optical communication system to cope with the data explosion. Distributed parametric amplification (DPA), with its potential green characteristics, i.e. noiseless, high-speed response, high power efficiency and wavelength flexibility, provides a promising amplification solution for the next generation of optical communication systems. As on specific type of optical parametric amplification (OPA), DPA is based on the combination of self-phase modulation (SPM), cross-phase modulation (XPM) and four-wave mixing (FWM) effects. DPA’s main difference from OPA lies in the amplification medium. As DPA utilizes the most commonly adopted transmission fiber, i.e. single-mode fiber (SMF) and dispersion-shifted fiber (DSF), the signal transmission can thus be fulfilled simultaneously with the parametric amplification in the same optical fiber: DPA’s configuration also brings another green feature, pump-power recycling, which further enhances the power efficiency of the communication system.

As the fundamental study on DPA, first the gain spectrum is investigated. Both single- and two-pump DPAs are presented experimentally for WDM signals. In these experiments, residual pump power recycling is enabled by a concentrated photovoltaic (CPV) cells, Moreover, through experimental comparison with another important distributed amplification technology, distributed Raman amplification (DRA), DPA’s advantages over DRA are demonstrated. When considering similar performance levels, DPA needs much lower pump power than DRA, which in return improves the system power efficiency.

The performance of DPA cannot be judged unless it is assessed in more advanced application scenarios. Thus more advanced studies on DPA are conducted. The modulation format transparency is first presented with both phase (differential phase-shift keying (DPSK)) and intensity (on-off keying (OOK)) modulation formats, and our experimental results show the superiority of DPSK over traditional OOK. Furthermore, from the perspective of wavelength flexibility, we have demonstrated, for the first time to the best of our knowledge, a DPA system at the 1.3μm telecommunication window, which provides a potentially green amplification scheme at this transmission band. All these experiments, to a certain extent, certify the feasibility of DPA to become a green optical fiber amplifier. Finally, to demonstrate DPA’s compatibility within a more complicated communication system, we propose a power–efficient UWB/DPA system for the “last mile”. After experiments on photonic UWB pulse generation and the supporting DPA system, the hybrid UWB/DPA system is demonstrated with preliminary simulation results.

My research efforts presented in this thesis all aim at the practical application of the DPA scheme into the next-generation of green communication systems. If further armed with the phase-sensitive configuration, DPA’s potential as a green amplifier will be further augmented.