title: Performance comparison of optical 8-ary differential phase-shift keying systems with different electrical decision schemes: Comment.
abstract: We summarize three electrical decision schemes that have been proposed for 8-level differential phase-shift keying, briefly discuss their performance and complexity, and comment that two of these schemes have been confused in an earlier comparison in Optics Express.
authors.forename: Erik
authors.initials: E
authors.lastname: Agrell
authors.forename: Magnus
authors.initials: M
authors.lastname: Karlsson