1. Northumbria University,Optical communications research group,Newcastle upon Tyne,United Kingdom
2. Instituto de Telecomunicações and the Departamento de Electrónica, Telecomunicações e Informática, Universidade de Aveiro,Aveiro,Portugal
3. Czech Technical University,Department of electromagnetic field,Praha,Czech Republic
4. Northumbria University,Department of Computer and Information Sciences,Newcastle upon Tyne,United Kingdom