Kaoru Kinjo

A comparative study of DPSK and OOK WDM transmission over transoceanic distances and their performance degradations due to nonlinear phase noise

We have compared experimentally the transmission performance of return-to-zero differential phase-shift keying (RZ-DPSK) with RZ-ON-OFF keying (OOK), nonreturn-to-zero differential phase-shift keying (NRZ-DPSK), and NRZ-OOK for 100/spl times/10-Gb/s transmission with a spectral efficiency of 0.22 b/s/Hz over transoceanic distances. The Q degradation of the RZ-DPSK after transmission over 9180 km was 3 dB greater than that of RZ-OOK. The experimental results clearly showed the major cause of degradation for DPSK is not cross-phase modulation but self-phase modulation. The calculated nonlinear phase noise, i.e., the Gordon-Mollenauer effect, agreed with the experimental results. A distributed-Raman-amplifier assisted erbium-doped-fiber-amplified transmission line acted well in reducing the nonlinear phase noise.

Bidirectional unrepeatered 43 Gb/s WDM transmission with C/L band-separated Raman amplification

A novel wavelength arrangement using C- and L-band-separated Raman preamplification is proposed for application to bidirectional unrepeatered transmission systems operating with multiple 43 Gb/s channels. The proposed wavelength allocation makes it possible to greatly mitigate Raman gain depletion by the counter-propagating signals. The authors have achieved bidirectional unrepeatered transmission of 32 /spl times/ 43 Gb/s channels (= 1.28 Tb/s) over 200 km with Raman preamplifiers using the proposed technique. They found that the system performance of bidirectional transmission with C/L band-separated Raman preamplification is degraded by nonlinear interactions between the high power Raman pump lights and the WDM signals. The root cause can be described in terms of nondegenerate four-wave mixing induced by beating between the WDM signals and two longitudinal modes of the Raman pump light. A solution avoiding ND-FWM was demonstrated in a 32 /spl times/ 43 Gb/s transmission experiment.

A comparative study of 10 Gb/s RZ-DPSK and RZ-ASK WDM transmission over transoceanic distances

We have experimentally compared RZ-DPSK with RZ-ASK for 100/spl times/10 Gb/s transmission over transoceanic distances. The Q degradation of RZ-DPSK due to nonlinearity effects after transmission over 9180 km was 3 dB larger than that of RZ-ASK.

65 /spl times/ 22.8 Gb/s WDM transmission over 8,398 km employing symmetrically collided transmission with Aeff managed fiber

Two proposed methodologies, Aeff management and symmetrically collided transmission, were discussed for long haul transmission systems. 65 /spl times/ 22.8 Gb/s WDM transmission over 8398 km was achieved by employing these techniques.

Gordon-Mollenauer effect in DPSK transmission over transoceanic distances employing Raman/EDFA repeaters

10 Gb/s x 100-wavelength transmission experiment and theoretical analysis show that the transmission performance of DPSK is degraded mainly by the Gordon-Mollenauer effect. A Raman/EDFA hybrid repeatered transmission line acts well to reduce that effect.