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Abstract-In this letter, we demonstrate a simple technique for dispersion monitoring by adding a single inband subcarrier tone to the transmitted data signal. A measurable dispersion of up to 1200 ps/nm is demonstrated in a 10-Gb/s channel using a 7-9 GHz subcarrier and the addition of the subcarrier induced a power penalty of 0.5 dB. Dynamic ranges exceeding 20 dB and resolution sensitivities better than 10 (ps/nm)/dB are shown. With an 8-GHz tone and a 15% modulation depth for 10-Gb/s signals, we show a measurement range of 975 ps/nm with a 22-dB dynamic range. We used the monitor output signal to achieve accurate tunable dispersion compensation.

We present a novel all-fiber narrow-band filter based on pump-induced saturable-gain or-absorber gratings in a loop mirror. Our design provides built-in interferometric phase alignment of the signal to the grating for optimal filtering. Notch or bandpass functionality is determined by the choice of gain or absorption and the input ports selected for the pump and signal. The loop-mirror filter has potential bandwidths from the submegahertz to beyond the gigahertz regimes, and one can tune it optically by changing the wavelength of the pump light that establishes the grating. Such filters have potential applications to wavelength-division-multiplexed optical networks and optical rf signal processing.

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