Ultrahigh-speed optical transmission and signal processing utilizing nonlinear effects in fibers

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1. Achievements relating to ultrahigh-speed long-distance transmission utilizing fiber nonlinearities are as follows :(1) We have demonstrated transmission of a pair of soliton pulses with separation of 12.5ps, corresponding to a bit rate of 80Gb/s, over more than 7,000km in a densely dispersion-managed (DDM) recirculating fiber loop.(2) We have experimentally demonstrated the existence of bi-solitons, with which pulse-to-pulse interaction is eliminated, by a recirculating transmission experiment. We also examine stability of bi-solitons against variations in initial pulse parameters and applicability of bi-solitons in WDM transmission.(3) By numerical simulations we have shown that high spectral-efficiency soliton transmission can be obtained by a combined use of doubly-periodic dispersion management and soliton transmission control. We have also shown that DDM soliton transmission with filter control realizes distance more than 5,000km at 160Gb/s but with limited effectiveness of dis … More persion compensation at the receiver end.2. Achievements relating to optical signal processing utilizing fiber nonlinearities are as follows :(1) We have carried out quasi-80Gb/s recirculating transmission experiment and have shown that error-free transmission distance can be extended from 300 to 1,000km by the use of an all-optical 2R regenerator based on self-phase modulation in a fiber.(2) We have shown through a 10Gb/s transmission experiment that an all-optical limiter based on saturation of four-wave mixing in a fiber improves BER of DPSK transmission through suppression of nonlinear phase noise.(3) We have proposed signal power to pulse number conversion based on slicing of SPM-broadened spectrum by an arrayed waveguide grating and have demonstrated all-optical two-bit AD conversion. We have also proposed and demonstrated optical DA conversion using cascaded optical switches.(4) We have proposed and demonstrated all-optical variable delay method using temporal shifts produced by collisions between solitons with different wavelengths. Less