Hiroki Ooi

40-Gb/s WDM transmission with virtually imaged phased array (VIPA) variable dispersion compensators

We have demonstrated variable dispersion compensation by using a virtually imaged phased array (VIPA) to overcome the small dispersion tolerance in 40-Gb/s dense wavelength-division multiplexing (WDM) transmission systems. By utilizing the periodical characteristics of VIPA compensators, we performed simultaneous dispersion compensation in a 1.28-Tb/s (40-Gb/s/spl times/32 ch; C band) short-haul transmission and confirmed that only two VIPA compensators and one fixed dispersion-compensating fiber are required for a large transmission range of 80 km. This performance can greatly reduce the cost, size, and number of compensator menus in a 40-Gb/s WDM short-haul transmission system. In addition, we achieved 3.5-Tb/s (43-Gb/s/spl times/88 ch; C and L bands) transmission over a 600-km nonzero dispersion-shifted fiber by using VIPA compensators. Although channel-by-channel dispersion compensation is required due to the larger residual dispersion slope in long-haul transmission, the periodical characteristics of the VIPA compensators offer the advantage of considerably reducing the number of different modules required to cover the whole C (or L) band. An adequate optical signal-to-noise ratio, which was the same for all channels, was-obtained by using distributed Raman amplification, a gain equalizer, and a preemphasis technique. We achieved a Q-factor of more than 11.8 dB; (BER<10/sup -17/ with forward-error correction) for all 88 channels.

Polarization-mode dispersion sensitivity and monitoring in 40-Gbit/s OTDM and 10-Gbit/s NRZ transmission experiments

Summary form only given. We established guidelines for the 40-Gbit/s system design with optimum dispersion compensation and optical power against chromatic dispersion and self-phase modulation (SPM). The signal distortion due to PMD remains a major limitation on transmission distance. This paper describes our experimental evaluation of PMD sensitivity in 40-Gbit/s OTDM transmission using a PMD emulator. We also found that the 40-GHz frequency component in the baseband signal is sensitive to waveform distortion due to PMD, and can be used for PMD monitoring. We also investigated PMD sensitivity and monitoring in 10-Gbit/s nonreturn to zero (NRZ) transmission experiments.

Automatic polarization-mode dispersion compensation in 40-Gbit/s transmission

We believe we demonstrated automatic polarization-mode dispersion (PMD) compensation in 40-Gbit/s NRZ transmission for the first time. By the feedback control of an optical PMD compensator to maximize the 20-GHz intensity of received baseband signals, we more than doubled the allowable PMD from 11 to 23 ps.

3.5-Tbit/s (43-Gbit/s /spl times/ 88 ch) transmission over 600-km NZDSF with VIPA variable dispersion compensators

Summary form only given. We performed 3.5-Tbit/s (43-Gbit/s /spl times/ 88 ch) 600 km transmission in the C- and L-bands by using virtually imaged phased array (VIPA) variable dispersion compensators. An adequate OSNR, which was the same for all the channels, was obtained by using distributed Raman amplification (DRA), a gain equalizer (GEQ), and a pre-emphasis technique. VIPA variable dispersion compensators can thus effectively overcome the small dispersion tolerance and temporal dispersion changes of dense WDM terabit systems. We achieved a Q-factor of more than 11.8 dB (BER < 10/sup -17/ with FEC) for all 88 channels.

20 Gbit/s transmission experiments over 2040 km using OTDM and conventional TDM transmitter schemes

Summary form only given. In this paper, we demonstrate the 20-Gbit/s transmission experiments over 2040 km of dispersion-shifted fiber using two kinds of transmitter schemes; optical-time-division multiplexing (OTDM) and conventional TDM.

Statistical characteristics of higher-order PMD and its impact on transmission systems

In this paper, the characteristics of higher-order PMD up to third order and its impact on transmission systems are mainly studied. Based on the concept of second order principal states of polarization (PSPs) put forward in the paper, the covered ranges of higher-order PMD parameters with the increasing instantaneous differential group delay (DGD) value are investigated by simulation. It shows that the upper covered range of PSP rotation rate decreases rapidly with increasing instantaneous DGD until the DGD reaches the PMD value of the fiber, and then continues to slowly decrease. This may cause serious signal distortion due to fast PSP rotation rate even DGD at the low value. Furthermore, to that of the second order PSP rotation rate and that of second order PMD vector magnitude, they increase simultaneously with increasing instantaneous DGD until the DGD reaches about 2 times PMD value of the fiber, then turn to decrease. This may has an impact on the performance of higher-order PMD compensators. At the same time, the simulation results show that higher-order PMD parameters can impose serious signal distortion on 40 Gbit/s systems and the higher PMD value, the higher higher-order PMD influence on signal distortion.

Evaluation of higher-order PMD-emulator for 40-Gbit/s systems

An effective way to evaluate the performance of PMD compensation, which uses a proposed polarization-mode dispersion (PMD) emulator, has been studied recently. In this paper, we first present a theoretical analysis on a special model of PMD-emulator (PMDE), then explain the first and second-order PMD effects, which are very useful to value the impact of high-order PMD on pulse. Numerical and experimental results show that PMDE can emulate the statistics property and cover the range of high-order parameter of the real fiber successfully. The impact of second-order PMD on pulse for 40Gbit/s optical fiber communication is also presented as the simulation results.

Combined effects of SPM, GVD, and PMD on 40-Gbit/s NRZ and RZ modulation formats

We demonstrate the combined effects of SPM, GVD, and PMD-induced eye-diagram penalties by means of numerical simulations for 40Gbit/s NRZ and RZ modulation formats. Considering all orders of PMD, we choose a fixed state of input polarization (SOIP) and do the simulation 1000 times for each input average power, and then get the Q-penalty of eye-diagram by exponential extrapolation method for cumulative probability 10-5. When input average power is less than 0dBm, SPM effect is very weak and GVD is compensated completely, only PMD takes effect in this power area. The Q-penalties are constants for NRZ and RZ with different PMD values. As input average power increasing, SPM takes effect gradually. First order PMID can suspend the SPM affection, and the higher PMD value, the more postponement is observed. The Q-penalty contributed by higher order PMID has close relation with spectrum width of signal. For NRZ signal with chirp=-0.7, the interactions between SPM and chirp can decrease spectrum width of signal; the Q-penalty contributed by higher order PMD will decrease correspondingly. For RZ with duty 0.3, the changing of the root mean square (RMS) spectrum width induced by the interactions of SPM and chirp is not obviously in this case, the Q-penalties of SPM+GVD+PMD increase consistently. When SPM effect is too strong (For example: for NRZ, average power larger than 10dBm; for RZ with duty 0.3, average power larger than 6dBm.), the interactions of SPM+GVD+PMD will cause the seriously degradation of system performance for any duty cycle and PMID value. Under our simulation conditions, the narrower pulse-width, the less Q-penalty until duty cycle decreases to 0. 1.