A quad-wavelength fiber ring laser using a semiconductor optical amplifier (SOA) as a gain medium and an array waveguide grating (AWG) as a selective wavelength filter is proposed and demonstrated. The quad-wavelength fiber ring laser is capable of generating four laser wavelengths at 1531.0 nm, 1533.3 nm, 1535.7 nm, and 1538.0 nm with a peak power at -20 dBm and a channel spacing of 0.24 nm (300 GHz) corresponding to the channel spacing of the selected AWG ports. The quad-wavelength ring laser shows stable operation over time with negligible fluctuations in the peak power of the lasing wavelengths. The separation of the two lasing wavelengths can be tuned over several nanometers by changing the ports of the AWG. The proposed laser configuration has the advantage of stable quad-wavelength output at room temperature as well as a simple and compact design with many potential DWDM and sensor applications.

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The thermoluminescence (TL) provided by flat optical fibers (FF) have been proposed as the basis for a novel radiation sensor, for use in medical dosimetry for both diagnostic and radiotherapy applications. A flat optical fiber with nominal dimensions of (3.226 x 3.417 x 0.980) mm 3 and made of pure silica SiO 2 was selected for this research. The FF was annealed at 400 o C for 1 h before being irradiated. Using a linear accelerator (LINAC), delivering doses in the range 2.0-10.0 Gy, the kinetic parameters and dosimetric glow curve representing TL response of the FF were studied with respect to electron irradiation of 6 MeV, 15 MeV and 21 MeV. The TL response was read out using a TLD reader Harshaw Model 3500. The Time-Temperature-Profile (TTP) of the reader used includes; initial preheat temperature of 80 o C, maximum readout temperature of 400 o C and a heating rate of 30 o Cs -1 . The proposed FF shows excellent linear radiation response behavior within the clinical relevant dose range for all of these energies, good reproducibility, independence of radiation energy, independence of dose rate and exhibits a very low thermal fading. From these results, the proposed FF can be used as radiation dosimeter and favorably compares with the widely used LiF:MgTi dosimeter, for application in medical radiotherapy application.

A photonic crystal fiber in photonic crystal fiber (PCF-in-PCF) architecture is numerically investigated for residual dispersion compensation in optical transmission link. The optimized structure shows a flattened and high average dispersion of À457.4 ps/nm/km in the wavelength range of 1360 nm to 1690 nm. The sensitivity of the fiber dispersion properties to a AE2% variation in the optimum parameters is studied for practical conditions. Additionally, the effect of variation in the structure parameters on effective mode area is simulated to understand its relationship to light confinement.