Funding for this research was provided by:
National Natural Science Foundation of China (11772017, 11272023)
National Natural Science Foundation of China (11471050)
the Fundamental Research Funds for the Central Universities of China (2011BUPTYB02)
the Fund for State Key Laboratory for Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications (2017ZZ05)
Article History
Received: 21 August 2018
Revised: 4 January 2019
Accepted: 21 January 2019
First Online: 14 June 2019