[3] F. J. Mustieles, E. Ballesteros, P. Baquero. Theoretical S-bend profile for optimization of optical waveguide radiation losses [J]. IEEE Photon. Technol. Lett., 1993, 5(5):551～553

[4] Vijaya Subramaniam, Gregory N. De Brabander, David H. Naghski et al.. Measurement of mode field profiles and bending and transition losses in curved optical channel waveguides [J]. J. Lightwave Technol., 1997, 15(6):990～997

[6] Tsutomu Kitoh, Norio Takato, Mitsuho Yasu et al.. Bending loss reduction in silica-based waveguides by using lateral offsets [J]. J. Lightwave Technol., 1995, 13(4):555～561

[9] R. Baets, P. E. Lagasse. Loss calculation and design of arbitrarily curved integrated-optic waveguides [J]. J. Opt. Soc. Am., 1983, 73(2):177～182