Zirconia ferrules for optical connectors were examined after aging at 85°C and 95% relative humidity. Two degradation mechanisms were the roughening and the deformation of the zirconia ferrule surface. Raman microscopy revealed that this relatively low‐temperature degradation of zirconia ferrules is caused by the tetragonal to monoclinic transformation of zirconia, and is accelerated by stress relief during polishing. The surface upheavals associated with low‐temperature aging may significantly degrade the performance of optical connectors over time.

High power lasers and amplifiers for communication networks based on cladding pump fiber operate at unprecedented power levels. The high power and unique structure of cladding pump fiber present new challenges to the optical reliability of lasers and amplifiers based on these novel fibers. In this paper we present results on the reliability of cladding pump fiber under high power both in the multimode pump waveguide and in the rare earth doped core

Over the past few years there has been a race to develop glasses with both large and small nonlinearities. A number of diverse applications such as controlling beam break-up in high-power lasers and maximizing the optical power budget in the fibre-optic based communications require low optical nonlinearities. Whereas the demonstration of alloptical devices for switching and logic requires high nonlinearity, an understanding of the nonlinear optical phenomena provides the ability to tailor the glass compositions for ultrashort-pulse generation or ultralong-distance soliton transmission. In this paper we review recent advances in the development of nonlinear glasses. We will consider the induced second order nonlinearities produced using second harmonic generation and electric field poling. We also report on high third order nonlinearities in silicate, tellurite, heavy-metal oxide, metal-doped and chalcogenide glasses. Finally recent developments In photosensitivity and fibre gratings will be discussed.

The performance of today's fiber optic communication network demands high reliability of optical fiber systems in general, and optical fiber connectors in particular. In this study we address the effects of the polishing on the surface of optical fiber and consequently on the reliability of the optical connectors. It is found that high surface stresses (compression) are produced during the optical connector endface polishing. Molecular dynamics computer simulations of silica ere performed and it was confirmed that substantial permanent densification of silica under compression at room temperature without fracture exists. Based on these simulations and previous experimental and theoretical results, it is proposed that the densified subsurface damaged layer is responsible for the increase in reflectance in optical connectors.

Discrete reflections are produced by physical discontinuities at connectors, mechanical splices, or at fiber-to-component connection points in fiber-optic systems. Even a small amount of reflected light arriving at the source laser can affect its modulation performance and increase the relative intensity noise. Consequently, the link signal-to-noise ratio deteriorates, causing a power penalty in both analog and digital systems. Multiple reflections aggravate the situation. The accepted solution is to restrict the component reflectances to below a certain maximum. This paper reports our findings on the accuracy of optical continuous wave reflectometry (OCWR) and optical time domain reflectometry (OTDR) techniques down to minus 70 dB reflectance. If the reflected power is estimated by integrating under the reflection peak, the OTDR is more accurate at low reflectances; it enables measurements down to minus 62 dB with an accuracy of plus or minus 1.0 dB or down to minus 65 dB with an accuracy of plus or minus 2.0 dB. The sensitivity of the measurements to the pulsewidth and to the characteristics of the optical lead-in fiber were also evaluated.

Tellurite glass is a good host for Tm3+ because of high quantum efficiency and good glass stability. For 1.47 μm the upper limit for Tm2O3 concentration without quenching is 0.4 wt%. For 1.88 μm, it should be 0.4 wt% in order to take advantage of the two-for-one transition.

Although optical splices are protected from fluid immersion during their service life, unanticipated exposures have occurred. For this reason, Bellcore generic requirements include a water immersion test to determine whether splices can tolerate a short-term water exposure and still perform adequately. Mechanical splice failures have been observed in the field and in laboratory experiments. Almost all mechanical splices use index-matching gel, and failures were believed to result from fluid migration along the fiber/gel interface, or fluid diffusion through the gel. We used a photographic analysis to provide direct evidence for these failure modes. We immersed simulated splices in a variety of contaminated fluids and observed that the most rapid mechanism, and the one we consider most likely to result in splice failure, was fluid migration. In addition, we measured loss and reflectance performance for actual splices immersed in contaminated fluids, correlating performance to the results of our photographic analysis. We show that immersion in contaminated water representative of the outdoor plant environment accelerates splice failures.

Tellurite glasses are examples of non-silica oxide glass hosts which are the subject of intensive materials research. Because their characteristic phonon energies are lower than those of silica glasses, praseodymium- and neodymium-doped tellurite glasses are considered for 1.3 μm fiber amplifiers. The glass formation, waveguide fabrication, optical properties and suitability for fiber drawing of sodium, zinc, tellurium oxide glasses doped with rare earth ions are described.

A single-mode Nd(3+)-doped tellurite glass fiber laser operating at 1.061 microm is described. We believe this is the first demonstration of a single-mode fiber laser in tellurite glass. A lasing threshold of 27 mW of 818-nm absorbed pump power and a slope efficiency output power versus pump power of 23% emitted from one end were observed in the fiber cavity with 11.9% Fresnel reflection at both ends.

The physical properties of R2O-ZnO-TeO2 glasses have been studied for their feasibility for fiber drawing and rare earth doping. A tellurite glass fiber with less than 1 dB/m loss has been made by the rod-in-tube method. The spectroscopic properties of rare earth ions (Pr3+, Nd3+, Er3+, and Tm3+) in tellurite glass are discussed and compared with silica, fluoride and chalcogenide glasses.

Recent successes in transporting optical power near the 1-W level via optical fiber suggest that it may be possible to operate conventional telephone station sets using electricity derived photovoltaically from light in a fiber. The authors investigate the constraints on optical powering in fiber-in-the-loop (FITL) applications and assess its applicability in terms of end-to-end efficiency, loop length, and system cost. To make this assessment, they look at several different optical-powering system architectures and components vis-a-vis their cost-versus-delivered-power capability. Related issues such as safety and reliability are discussed.

We observe guided blue and green upconversion fluorescence in an ion-exchanged waveguide that is fabricated in an erbium-ytterbium-codoped silicate laser glass. The guides are optically pumped at room temperature by using a Ti:sapphire laser with lambda = 880-980 nm; the observed fluorescence is in two bands, 480-490 and 520-560 nm, and results from multiphoton excitation.

The Raman spectra of various cation-modified sodium phosphate, sodium aluminum phosphate, and sodium silicate glasses are reported. As Ti is added to phosphate glass, these spectra indicate that it first enters into tetrahedral and then, as more is added, into octahedral sites and becomes part of the glass-forming network. Addition of Bi as well as Ti changes the Raman spectra very little, which implies that Bi does not occupy chain-forming sites. If Nb is included in addition to Ti, alterations in the spectra show that Nb also enters octahedral sites. In silicate glasses as in phosphate glasses, Ti enters tetrahedral and octahedral sites in the chain-forming network. However, in silicate glasses, the Ti-sensitive modes are dominant, whereas in the phosphate glasses doped with Ti all modes are nearly equal in intensity. This equality indicates that the polarizability of the Ti-sensitive modes in the silicate glasses is greater than those of modes involving mainly silicon and oxygen motion as compared with those involving mainly phosphorus and oxygen motion.

Moderately high refractive index titania borosilicate glasses are sputtered into glassy films. Deposition parameters are used to control the stoichiometry and optical properties of the films. Compositions unobtainable by batch melting are achieved with TiO2 levels up to 47 mol.%. The films are extremely durable with average optical intensity damage thresholds of 13.5 GW cm-2. Multilayer films have similar damage thresholds. Total optical losses at 633 nm are 8 dB cm-1 when waveguided in a 0.3 μm film on a fused quartz substrate.

The nonlinear optical properties of glass have recently become the focus of growing scientific and technological interest. Nonlinear properties include intensity-dependent refractive index, multiphoton absorption, second and third harmonic generation, stimulated Raman and Brillouin scattering, and associated phenomena such as self-focusing, self-phase modulation, optical phase conjugation, and optical bistability. We report on a large amount of work that reaches beyond simple glasses such as silica. Nonlinear optical phenomena have been investigated in materials ranging from oxide, halide, and chalcogenide glasses to glasses doped with semiconductor microcrystals, organic dyes, and metal particles and in forms varying from bulk materials to optical fibres and waveguides. We also discuss recently discovered photoinduced effects in glass fibres, which include second harmonic generation and the formation of refractive index gratings. The ability to tailor the nonlinear optical properties of glass has been utilised in such diverse applications as controlling beam breakup in high power lasers, demonstration of all-optical devices for switching and logic, ultra short-pulse generation, and ultra long distance soliton transmission.

We report the observation of spatial optical solitons due to the Kerr nonlinearity in a planar glass waveguide and present measurements of the nonlinear response obtained by placing a pinhole at the output of the waveguide. For input intensities greater than that required for the fundamental soliton, we observe breakup of the output owing to the effect of two-photon absorption.

Current interest in all-optical waveguide devices has created a need for suitable nonlinear materials and fabrication techniques. To meet this need, we have made optical waveguides using ion exchange in two glasses, which were designed both to have large optical nonlinearities and to be compatible with the ion-exchange processing. We find that the choice of alkali metal ion in the glass has a major effect on the exchange process and on the optical quality of the ensuing guides. Guides made in one of these glasses have been used for demonstrations of spatial soliton propagation, which can be used as the basis of an all-optical switch.