An alternative approach of making all fiber-based optical add and drop modulator is developed. This approach utilizes a high spatial resolution retro-reflectometric technology and the well-established optical fiber fusion splicing process to combine a pair of matched fiber Bragg gratings which are readily available with two fiber-fused 3dB couplers into a balanced Mach-Zehnder interferometer. The advantage is that the key elements in the device are all commercially available and the element integrating process is mature. Prototype devices of compact size are built and the optical performance is characterized. The device insertion loss is 0.2 approx 0.3 dB in the best case and 0.8dB in general for both the drop and pass bands. The adjacent channel isolation is >28dB for drop band and >35dB for pass band. The drop band is in flat top shape with bandwidth about 0.6 approx 0.7nm at -0.5dB with respect to the power level at center wavelength. The flat top structure enables the device to tolerate wider temperature fluctuation without significant sacrifice of device optical performance. Polarization dependent loss is less than 0.1dB for drop band and less than 0.05dB for pass band. Polarization mode dispersion is approx 0.3ps and <0.05ps for the drop and pass bands, respectively. The relatively high polarization mode dispersion for the drop band could be improved by better grating writing techniques.
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