A formula used to calculate the power penalty caused by optical nodes such as OADM/OXC nodes in WDM all optical networks is deduced on the base of interference between electric fields by taking the phase character of node transmission into account. To prove its correctness, we use the formula to figure out the power penalties in the case where the central frequencies of multiplexer/demultiplexer (MUX/DEMUX) stand away from the ITU-T grid, and compare them with experimental results. Both calculating and experimental results show that when central frequency of MUX/DEMUX changes from —30GHz to 40 GHz with respect to ITU-T grid, the corresponding power penalty changes up to about 6.5dB, and the maximum difference between them is 0.5dB.
A novel optical switch structure is proposed to implement the function of cross-connection, optical power control and crosstalk reduction for optical cross-connect (OXC) in wavelength division multiplexing (WDM) optical transport networks. Based on the conventional AS/AC network structure, the proposed one deploys a set of 1x2 digital optical switches (DOS) between the AS and AC modules. Thus the optical signal power can be controlled and the crosstalk can be reduced by adjusting the driving voltage of the 1x2 DOSs. Experiments with a 4x4 polymeric thermo-optical DOS demonstrate that the power control range is more than 35 dB, and the delay for 3 dB power control is within 7.5 ms in the worst case. Analytical result also shows that the crosstalk can be suppressed at least 35 dB.