The constant intensity downstream DPSK
signal is demodulated by a 1-bit delayed interferometer (DI) and balanced photo diodes.
The BER for coherent DPSK
demodulation can be calculated as
Zhang, "A novel bidirectional RSOA based WDM-PON with downstream DPSK
and upstream re-modulated OOK data", in 11th Int.
Tucker, "Chromatic Dispersion and PMD Mitigation at 10 Gb/s using Viterbi Equalization for DPSK
and DQPSK Modulation Formats" Opt.
In the first system for optical signal modulation in all three channels differential binary phase shift keying (DPSK
) was used, in the second--the intensity modulation (IM) and in the third--polarization shift keying were used, while the fourth is a combined transmission system, where for the first channels optical signal modulation NRZ DPSK
was used, for the second channel--NRZ--OOK and third--2--POLSK.