OPTICAL MULTI-LEVEL TRANSMISSION SYSTEM

摘要

A multi-level encoder circuit (230) in an optical multi-level transmitter (200) assigns 6QAM modulation to an information signal (201), and a photoelectric field modulator (211) converts the signal to a 6QAM optical multi-level signal (231) and outputs thereof. An optical multi-level signal (232) transmitted along an optical fiber transmission path (214) is received by a noncoherent multi-level receiver (220). A demodulated received electric field (116) calculated in the noncoherent multi-level receiver (220) has noise distribution larger in a phase direction than in an amplitude direction. A symbol judgment circuit (223) using an amplitude weight non-Euclidean distance has a phase judgment area larger in the phase direction; thereby errors in symbol judgment of the demodulated received electric field (116) are reduced to improve reception sensitivity.