A novel carrier-suppressed return-to-zero frequency shift keying (CSRZFSK) transmitter that can operate at 40 Gb/s and above is proposed for the first time. The transmission characteristics of the CSRZFSK signal at 40 Gb/s compared with differential quadrature phase shift keying (DQPSK) signal and amplitude shift keying (ASK) signal are investigated under different dispersion management. Simulation results show that CSRZFSK has the best nonlinear tolerance and longest transmission distance when compared with DQPSK and ASK signals. A 40 Gb/s CSRZFSK signal gives only a 0.1 dB sensitivity penalty while DQPSK and ASK give 0.6 and 0.7 dB, respectively.
We propose a novel scheme for generation and detection of a 40 Gb/s binary frequency shift keying (FSK) signal. Multispan
transmission properties are numerically compared with return-to-zero (RZ) and differential phase shift keying
(DPSK) formats. Experimental demonstration shows that a 40 Gb/s FSK signal is transmitted over 50 km standard
single-mode fiber (SMF) with 0.8 dB penalty and over 12 dB resilience of span input power, clearly validating the
feasibility of this FSK modulation scheme. Transparent wavelength conversion for a 43Gb/s RZ-FSK signal is
successfully achieved by FWM in a SOA and in HNDSF. 2R regeneration is also to be purposefully observed in HNDSF
which results in limited over-all penalty after 100km transmission link.