Research on nonlinear optics and lutra high-speed fiber-optic transmission based on the theory of integrable systems

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1.Theoretical analysis of dispersion managed solitons(a)We found that initial difference in amplitude and/or phase between neighboring dispersion managed(DM)soliton lses is effective to reduce the pulse-to-pulse interaction.(b)We discovered symmetric bi-soliton solution in DM fiber which showed extremely low pulse-to-pulse interaction.2.Transmission control of dispersion managed solitons(a)The energy of DM soliton is stabilized by inserting optical devices in transmission fiber such as optical bandpass filter and/or intensity modulator synchronously driven with the transmitting solitons. We found that the effectiveness strongly depended on the inserting position of the devices. Moreover, the pulse energy can be stabilized without optical bundpass filter if the position of the intensity modulator is properly chosen.(b)We found that the influence of channel-to-channel interaction on WDM soliton transmission can be greatly reduced by bit by bit tuning of the decision time of the receiver. … More (c)We proposed dense DM solitons where the period of the dispersion management is much shorter than the EDFA spacing for ultra-high speed(>80 Gbit/s)transmission. Dispersion slope compensation can be effectively done by inserting dispersion shifted fiber for the compensation right before EDFA's.3.Ultra short optical pulse generation and soliton transmission exeriment(a)We proposed the use of comb-like dispersion profiled fiber(CDPF)constructed by standard single mode fiber and dispersion shifted fiber for soliton transmission. The bit error rate of < 10-9 was achieved in 10 Gbit/s, 2,000 km transmission experiment in a recirculating loop, where the EDFA spacing of 80 km is twice as long as the dispersion distance.(b)We made 40 Gbit/s dense DM soliton transmission experiment with 60-km long dense DM fiber constructed by non-ro dispersion shifted fiber and observed eye pattern after 1,630 km transmission.(c)1.6ps. 160 GHz optical soliton pulses were generated by CDPF and optical pulse compression.(d)We transmitted two 3.7-ps width optical pulses with 10 ps separation in dense DM fiber and observed that the pulse separation became shorter after transmission. 2.6 ps, 87 GHz dense DM solitons were transmitted over 600 km.4.Nonlinear optical device(a)We analyzed the switching characteristics of nonlinear optical loop mirror(NOLM)where dispersion configuration of the loop is asymmetric. Both extinction ratio and switching threshold can be better than that of the conventional NOLM.(b)We analyzed timing and energy jitters included in the output optical pulses from actively mode-locked dispersion-managed fiber ring laser. Both jitters can be greatly reduced by properly choosing the position of the intensity modulator and the optical bandpass filter.(c)We proposed a new optical RZ receiver using pulse reshaping characteristics of nonlinear optical pulse propagating along normal dispersion fiber. We demonstrated that the amplitude and phase margins were greatly improved in 10 Gbit/s, 12,000 km optical soliton transmission. Less