[1] E. B. Desurvire, Journal of Lightwave Technology 24, 4697 (2006).

[2] K. Saitoh and S. Matsuo, Journal of Lightwave Technology 34, 55 (2016).

[3] M. Koshiba and K. Saitoh, IEEE Photonics Journal 4, 1987 (2012).

[4] D. Kumar and R. Ranjan, Optical Fiber Technology 41, 95 (2018).

[5] F. Ye, J. Tu, K. Saitoh and T. Morioka, Optics Express 22, 23007 (2014).

[6] A. Sano, H. Takara, T. Kobayashi and Y. Miyamoto, Journal of Lightwave Technology 32, 2771 (2014).

[7] M. Koshiba, K. Saitoh, K. Takenaga and S. Matsuo, Optics Expres 19, B102 (2011).

[8] J. Sakaguchi, W. Klaus, J. M. D. Mendinueta, B. J. Puttnam, R. S. Luís, Y. Awaji, N. Wada, T. Hayashi, T. Nakanishi, T. Watanabe, Y. Kokubun, T. Takahata and T. Kobayashi, Journal of Lightwave Technology 34, 93 (2016).

[9] T. Fujisawa, Y. Amma, Y. Sasaki, S. Matsuo, K. Aikawa, K. Saitoh and M. Koshiba, IEEE Photonics Journal 9, 7204108 (2017).

[10] D. Kumar and R. Ranjan, Quantum Electronics 49, 1045 (2019).

[11] K. Okamoto, Fundamentals of Optical Waveguides, Academic Press, San Diego, USA, 183 (2006).

[12] F. Y. M. Chan, A. P. T. Lau and Hwa-Yaw Tam, Optics Express 20, 4548 (2012).

[13] D. Kumar and R. Ranjan, Optoelectronics Letters 16, 126 (2020).

[14] T. Hayashi, T. Taru, O. Shimakawa, T. Sasaki and E. Sasaoka, Optical Express 19, 16576 (2011).

[15] D. Kumar and R. Ranjan, Optical Engineering 58, 056109 (2019).

[16] D. Kumar and R. Ranjan, Journal of Optical Communications 42, 1 (2021).