| In this report we investigate the theory and development of tunable all-fiber devices for optical fiber communications. With the growth of Dense Wavelength Division Multiplexing (DWDM) technology there is an increasing need for wavelength selective components for such applications as multiplexing and demultiplexing, wavelength add/drop, and laser stabilization. In particular, there is a growing need for tunable fiber devices for such applications as reconfigurable networks, tunable dispersion compensation, dynamic gain control, polarization control, and tunable lasers.; We have developed the theory of tunable all-fiber devices and demonstrated several novel all-fiber devices. A tunable fiber Bragg grating filter with a chemically etched cladding has been demonstrated. By reducing the cladding diameter of a fiber Bragg grating through etching with HF, the tension tuning force can be lowered by over an order of magnitude. We also describe a novel electrically tunable fiber Bragg grating (FBG) filter with a chemically etched cladding and an evaporated resistive layer on one side of the fiber. Wavelength tuning ranges up to 2.5nm with efficiencies greater than 8.5 nm/Watt have been demonstrated along with modulation bandwidths up to 14Hz. We have also demonstrated for the first time tuning efficiencies over 200nm/Watt for a 30μm diameter etched cladding devices tuned under moderate vacuum conditions. These tuning efficiencies are over an order of magnitude higher than any previously reported tunable FBG. The etched cladding FBG is placed in a Si V-groove that serves the multiple functions of holding the FBG during etching and evaporation, and provides a simple and compact means for scaling up to arrays of tunable all-fiber devices.; Building on our work with thermally tuned FBG devices, we also demonstrate for the first time an efficient, electrically tunable, all-fiber polarization controller fabricated with evaporated micro-heaters. Inherently low insertion loss, compatibility with low power control electronics, and potential for compact, low cost fabrication in arrayed form makes the device a potential candidate for use in polarization mode dispersion (PMD) compensation systems. Finally, we present several ideas for future work on the development of tunable all-fiber devices. |
