1. Sagnac G (1913) Sur la preuve de la réalité de l’éther lumineux par l’expérience de l’interférographe tournant. Comptes Rendus 157:1410–1413 (translated as “On the proof of the reality of the luminiferous aether by the experiment with a rotating interferometer”)
2. Vali V, Shorthill RW (1976) Fiber ring interferometer. Appl Opt 15:1099–1100
3. Regarding the origin of the π/2 phase difference between the two output ports of a direction coupler, see, for example, Chap. 13.3. In: Yariv A, Yeh P (2007) Photonics, 6th edn. Oxford University Press
4. Arditty HJ, Lefèvre HC (1982) Theoretical basis of Sagnac effect in fiber gyroscope, vol 32. Series in Optical Sciences, Springer, Berlin, pp 44–51
5. Lefèvre HC, Arditty HJ (1982) Electromagnétisme des milieux diélectriques linéaires en rotation et application à la propagation d’ondes guidées. Appl Opt 21:1400–1409 in French