| Compared with optical devices served in integrated optics or micro electrical-mechanical systems (MEMS), an all-fiber device is noted for its low coupling loss, compact size, and ease of packaging. In this dissertation, we investigate designs and implementations of novel tunable all-fiber devices for optical fiber communication and sensor applications. A strain-induced thermally-tuned long-period fiber grating (LPG) is demonstrated by mounting a fiber onto a periodic corrugated silicon substrate. Electrically tuning is also demonstrated by integrating the LPG with thin-film micro-heaters on the substrate. Both silicon V-groove etching and thin-film metal deposition can be realized using standard micro-fabrication technique.; A computer programmable, 32 elements polarization-mode dispersion (PMD) emulator was made using an array of polarization maintaining fiber (PMF) integrated with thin-film micro-heater on each fiber. Adjustment of the PMD is achieved by varying the temperature of the PMF using the micro-heater. The tuning efficiencies of this device versus various ambient pressures were also studied by coating a thin-film heater onto a fiber Bragg grating and measuring in a vacuum chamber.; The core to cladding mode coupling in polarization maintaining fibers is also studied in this dissertation. Acousto-optic (AO) method was used to characterize cladding modes in a PMF. A pair of periodic corrugated fixtures were employed to inspect the coupling properties of various fiber orientations. By tracking the coupling strength, it is possible to identify the birefringence axes of a PMF.; We also developed a novel on-fiber photodetector for on-line power monitoring by bonding a p-i-n photodetector directly onto the fiber using index matching UV-epoxy. This technique can monitor the out-coupled power from core to cladding modes in a fiber. This scheme can be applied on an all-fiber spectrometer.; Further improvements, such as reducing thermal crosstalk on the thermally-tuned devices, and future work to design a more sophisticated device, are also discussed in the dissertation. |
