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All-optical updating of subcarrier multiplexed headers and the simultaneous wavelength conversion of baseband payload is demonstrated. Updating is achieved by utilizing the low-pass frequency response of wavelength conversion via cross gain modulation in semiconductor optical amplifiers to suppress the original subcarrier multiplexed header while efficiently converting the baseband payload. A new header is then inserted by optically modulating the output of the wavelength converter with the new subcarrier encoded data. Updating of a pseudorandom 100 Mb/s header coded on a 16.5-GHz microwave subcarrier is achieved with wavelength conversion of a 2.5 Gb/s pseudorandom baseband payload. Crosstalk measurements are presented to determine cascadability of this technique and indicate that subcarrier suppression of 16.9 dBe followed by 20.2-dBe remodulation overcomes degradation due to residual original subcarrier and remodulation of the baseband payload. A key feature of this technique is the preservation of all-optical baseband payload transparency up to the header subcarrier frequency.
Date of Publication: June 1997