B.J. Ainslie

A review of the fabrication and properties of erbium-doped fibers for optical amplifiers

Erbium-doped fiber has become the central component of nearly all optical amplifiers. Applications reported include repeaters, power amplifiers, preamplifiers, and distributed amplifiers. To date, nearly all the fiber used in these devices has been silica based and fabricated by variations on the major telecommunications fiber technology. Disadvantages of the silica-based host glass, such as low solubility of the rare-earth ions and narrowband fluorescence, have been carefully addressed and solutions have been found to overcome these potential drawbacks. Details of the current status of fabrication methods, matching particular fibers for specific applications, together with optimizing the fiber for high efficiency, are presented. >

Laser-trimmed four-port bandpass filter fabricated in single-mode photosensitive Ge-doped planar waveguide

A single-mode photosensitive waveguide Mach-Zehnder interferometer fabricated in Ge-doped planar silica is reported. Two-millimeter-long identical-wavelength reflection gratings using external UV beams have been written into each arm to demonstrate a four-port bandpass device for the first time using this technology. The imbalance in the arms after writing of the gratings is compensated by laser trimming of one photosensitive arm of the interferometer. A 96.8% reflection of the output port is measured, and 58.8% of the total power available at the input at 1.5558 mu m in the bandpass of 1 nm is transmitted at the second input port after laser trimming. The total fiber-to-fiber insertion loss of the device is measured to be 1.35 dB.<<ETX>>

The absorption and fluorescence spectra of rare earth ions in silica-based monomode fiber

Rare-earth ions have been systematically incorporated into the cores of silica-based optical fibers, and the absorption and fluorescence spectra have been measured. The results provide basic data for a wide range of possible future fiber-based devices. For specific telecommunications applications, ions that could be useful for sources in the 1.3- mu m and 1.5- mu m low-loss windows are identified. It is suggested that Er/sup 3+/, Nd/sup 3+/, and Tm/sup 3+/ are the most promising ions for semiconductor pumping with GaAs-based laser diodes. >

Interplay of design parameters and fabrication conditions on the performance of monomode fibers made by MCVD

An apparently undocumented loss mechanism in monomode fibers with germanium doped cores is demonstrated. This loss increases as the fiber drawing temperature and/or the germanium concentration increases. By consideration of this mechanism in the fiber design and fabrication, losses lower than previously reported have been achieved both in fiber with low germanium concentration (0.38 dB/km at 1.3 μm) and in higher doped, dispersion shifted fiber (0.37 dB/km at 1.55μm). The constraints on fiber design as a consequence of this loss mechanism are discussed.

Picosecond pump–probe interferometric measurement of optical nonlinearity in semiconductor-doped fibers

Refractive and absorptive optical nonlinearity can be distinguished using a pump-probe interferometric technique with picosecond time resolution. The method is applied to both resonant and nonresonant nonlinearities in optical fibers and reveals marked differences between the relaxation behavior of the refractive and absorptive nonlinearity in certain cases. A monomode fiber doped with CdS(x)Se(1-x) semiconductor nanocrystals exhibits a large optically induced phase shift with ~10-psec relaxation time, which is many orders faster than the relaxation of the absorptive nonlinearity under identical conditions.

The design and fabrication of monomode optical fiber

The design of monomode fibers is discussed in the context of optimizing fiber loss and dispersion simultaneously, with reference to the materials choices and limitations to preform and fiber fabrication by the MCVD technique. Two classes of monomode structure-matched cladding and depressed cladding-are considered. Ultralow attenuation has been achieved reproducibily in both classes of fiber. The control of fiber geometry and dispersion is also discussed. Matched cladding fiber suitable for systems operating at both 1.3 and 1.55 μm has been studied and mean losses of 0.45 dB/km at 1.3 μm and 0.28 dB/km at 1.55 μm have been achieved for a total of 130 km. The behavior of depressed cladding fiber is compared with predictions from the theory of propagation in W fibers. Depressed cladding fiber with stable guidance has been demonstrated with attenuation of 0.37 dB/km at 1.3 μm and 0.21 dB/km at 1.55 μm.

The fabrication, assessment and optical properties of high-concentration Nd3+- and Er3+-doped silica-based fibres

Abstract A method has been developed to fabricate and quantify silica-based fibres doped with high concentrations of Nd3+ and Er3+. These fibres are based on an Al2O3-P2O5-SiO2 core glass and are free from cluster centres, indicating their potential as components in short length devices.

The fabrication and optical properties of Nd3+ in silica-based optical fibres

Abstract We discuss the fabrication and optical properties of Nd3+-doped silica-based optical fibres as a function of core glass composition. The absorption and fluorescence spectra are shown to be very dependent on P2O5 concentration. This has resulted in multi-component host glass type optical behaviour from silica-based fibres.

Pump excited state absorption in Er3+ doped optical fibres

Abstract Ground and excited state absorption coefficients in the wavelength range 420–850 nm of Er 3+ doped optical fibres have been measured for various composition silica and fluorozirconate based fibres. Detailed results are presented for features near 650 nm and 800 nm. Excited state absorption near 800 nm is significant for all the fibres studied. Other possible pump wavelengths are discussed.

Optical and structural analysis of neodymium-doped silica-based optical fibre

Abstract Silica-based optical fibres have been doped with up to 15 wt% Nd 3+ . Time-resolved fluorescence spectra and structural analysis show that phase separation results only when Nd 3+ concentrations exceed 7 wt%.