[1] X. Zhou, H. Liu, R. Urata, S. Zebian. Scaling large data center interconnects: challenges and solutions. Opt. Fiber Technol., 44, 61(2018).
[2] P. J. Winzer, R. J. Essiambre. Advanced modulation formats for high-capacity optical transport networks. J. Lightwave Technol., 24, 4711(2006).
[3] E. Lach, W. Idler. Modulation formats for 100G and beyond. Opt. Fiber Technol., 17, 377(2011).
[4] Y. Feng, H. Wen, H. Y. Zhang, X. P. Zheng. 40-Gb/s PolMux-QPSK transmission using low-voltage modulation and single-ended digital coherent detection. Chin. Opt. Lett., 8, 976(2010).
[5] S. W. Lu, Y. Zhou, F. N. Zhu, J. F. Sun, Y. Yang, R. Zhu, S. N. Hu, X. X. Zhang, X. L. Zhu, X. Hou, W. B. Chen. Digital-analog hybrid optical phase-lock loop for optical quadrature phase-shift keying. Chin. Opt. Lett., 18, 090602(2020).
[6] J. K. Perin, A. Shastri, J. M. Kahn. DSP-free coherent receivers for data center links. Proceedings of Optical Fiber Communication Conference, Tu2C.1(2018).
[7] T. Kikuchi, H. Yagi, N. Inoue, R. Masuyama, T. Katsuyama, K. Uesaka, Y. Yoneda, H. Shoji. High-responsivity of InP-based photodiodes integrated with 90° hybrid by low excess loss MMI design over wide wavelength range. Proceedings of Photonics Conference, 370(2014).
[8] M. Takechi, Y. Tateiwa, M. Kurokawa, Y. Fujimura, H. Yagi, Y. Yoneda. 64 GBaud high-bandwidth micro intradyne coherent receiver using high-efficiency and high-speed InP-based photodetector integrated with 90° hybrid. Proceedings of Optical Fiber Communication Conference, Th1A.2(2017).
[9] P. Runge, G. Zhou, T. Beckerwerth, F. Ganze, S. Keyvaninia, S. Seifert, W. Ebert, S. Mutschall, A. Seeger, M. Schell. Waveguide integrated balanced photodetectors for coherent receivers. IEEE J. Sel. Top. Quantum Electron., 24, 610037(2017).
[10] S. H. Jeong, K. Morito. Compact optical 90° hybrid employing a tapered 2 × 4 MMI coupler serially connected by a 2 × 2 MMI coupler. Opt. Express, 18, 4275(2010).
[11] Z. Wang, Y. M. Zhai, Y. Q. Lu, J. Xu, X. H. Sun, J. Wang. Compact optical 90° hybrid based on hybrid plasmonic multimode interferometer. Opt. Commun., 426, 99(2018).
[12] Z. Q. Lu, Q. Han, H. Ye, S. Wang, F. Xiao. Manufacturing tolerance analysis of deep-ridged 90° hybrid based on InP 4 × 4 MMI. Photonics, 7, 26(2020).
[13] M. Bachmann, P. A. Besse, H. Melchior. General self-imaging properties in N × N multimode interference couplers including phase relations. Appl. Opt., 33, 3905(1994).
[14] L. B. Soldano, E. C. M. Pennings. Optical multi-mode interference devices based on self-imaging: principles and applications. J. Lightwave Technol., 13, 615(1995).
[15] H. Ye, Q. Han, Q. Q. Lv, P. Pan, J. M. An, X. H. Yang. Monolithic integration of an InP-based 4 × 25 GHz photodiode array to an O-band arrayed waveguide grating demultiplexer. Opt. Laser Technol., 97, 290(2017).
[16] H. Ye, Q. Han, Q. Q. Lv, P. Pan, J. M. An, X. H. Yang, Y. B. Wang, R. R. Liu. 4 × 25 GHz uni-traveling carrier photodiode arrays monolithic with InP-based AWG demultiplexers using the selective area growth technique. Chin. Opt. Lett., 8, 082301(2017).
[17] S. Q. Liu, X. H. Yang, Y. Liu, B. Li, Q. Han. Design and fabrication of a high-performance evanescently coupled waveguide photodetector. Chin. Phys. B, 22, 108503(2013).
[18] T. Amano, H. Kishikawa, N. Goto. Simple DQPSK receiver based on format conversion from DQPSK to 4PAM by using a delay line interferometer and a photo detector. Proceedings of Opto-Electronics and Communications Conference(2020).
