Publisher Summary Photonic networks are beginning to take on an important role as a global information infrastructure for supporting economic activities, education, and mutual understanding of people. An important issue regarding hierarchical hybrid optical time-division multiplexing (TDM)/wavelength-division multiplexing (WDM) network nodes is how to realize ultrafast photonic processing, aiming for efficient and economical node realization. Photonic processing using optical fiber nonlinearity can be categorized into three functions. One is optical multiplexing, which is used in optical switches, multiplexers, and demultiplexers. The second is wavelength conversion, which is used in a variety of WDM systems. The third is phase-conjugation generation, which is used in midway optical phase conjugation (OPC) systems. In hybrid hierarchical optical time-division multiplexing wavelength-division multiplexing (OTDMWDM) networks—after grouping WDM channels as wavelength-band—the high-level traffic should be converted to terabit/s OTDM, which is cut through the low-level nodes with a guarantee of error-free transmission using single optical-carrier signal monitoring. Moreover, for the ultrahigh-speed OTDM scheme, all-optical polarization mode-dispersion (PMD) monitoring is needed to control the programmable optical circuit for PMD equalization.

OTDM and WDM for Large-Scale Photonic Networks

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.

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

We have experimentally investigated the nonlinear evolution of the basic polarization parameters. The nonlinear suppression of PMD (polarization mode dispersion) induced pulse broadening by reducing the coupling of the polarization modes is experimentally demonstrated in 10 Gbit/s RZ signal transmission.

T. Kudou

Papers

Suppression of PMD induced pulse broadening by using nonlinear evolution of polarization mode-coupling