Yamazaki, S.; Emura, K.; Shikada, M.; Yamaguchi, M.; Mito, I.; Minemura, K.: 'Long-span optical FSK heterodyne single-filter detection transmission experiment using a phase-tunable DFB laser diode', Electronics Letters, 1986, 22, (1), p. 5-7, DOI: 10.1049/el:19860004
IET Digital Library, https://digital-library.theiet.org/;jsessionid=7roqmc33ip18p.x-iet-live-01content/journals/10.1049/el_19860004