1. Aston Institute of Photonic Technologies; Aston University; Aston Triangle B4 7ET Birmingham United Kingdom
2. Key Laboratory of Specialty Fiber Optics and Optical Access Networks; Shanghai University; 200072 Shanghai China
3. Engineering Department; Al Musanna College of Technology; Muladdah Musanna, P.O. Box 191, P.C. 314 Sultanate of Oman
4. Institute of Photonics; Vienna University of Technology; Gusshausstr. 27/387 Vienna A-1040 Austria