In-situ investigation of coupling between a fibre and a slab waveguide

The mode coupling between a fibre and a slab waveguide was experimentally investigated during the formation of the slab. A thin film has been deposited on a polished fibre close to the core-clad interface. By monitoring the optical transmittance of the fibre during the film deposition the coupling efficiency between the formed slab and the fibre has been studied as a function of the film thickness. Strong attenuation in the fibre output has been observed for thickness values at which the propagation constants of the optical mode in the fibre match those of the slab waveguide.<>     

OH-ion distribution profiles in rod preforms of high-silica optical waveguide

To investigate the OH-contamination mechanism in high-silica optical waveguide, we have measured optically OH-ion distribution profiles in rod preforms prepared by the c.v.d. technique. The contamination due to OH diffusion from the supporting silica tube was clarified in relation to the deposited barrier-glass-layer thickness.     

Direct dispersion measurement of highly-erbium-doped optical amplifiers using a low coherence reflectometer coupled with dispersive fourier spectroscopy

The group delay and dispersion, including the erbium ion contributions, of the highly erbium-doped silica planar waveguide amplifier and multicomponent glass fibre amplifiers are directly measured at different pump powers using a low coherence reflectometer and dispersive Fourier spectroscopy. This method derives the refractive index spectra of these amplifiers directly from the produced reflectograms without any physical or mathematical assumptions. The dispersion of the planar waveguide amplifier at 500 mW pumping changes between +300 and -200 ps/km/nm with a 0.4 wt.% erbium concentration.<>     

Splicing losses between dissimilar optical waveguides

A simple computational formalism has been derived for the analysis of splicing and return losses between different optical waveguides. It has been found that the splicing loss can be approximated by the overlap integral method as long as total reflectance is negligible. The reciprocity of splicing loss between two single-mode waveguide is theoretically confirmed while return loss is found nonreciprocal. The return loss can be tolerably approximated by simple Fresnel formula except near the resonance. When close to the resonance, the deviation from Fresnel approximation is found to be strongly dependent on the structure of the waveguide and the refractive index difference between the core and clad     

Spot-size converter using vertical ridge taper for low fibre-coupling loss in 2.5%-/spl Delta/ silica waveguides

A novel spot-size converter based on a vertical ridge waveguide taper for super-high-/spl Delta/ silica waveguides is demonstrated. This structure can be formed with a simple fabrication process. The coupling loss between a singlemode fibre and a 2.5%-/spl Delta/ silica waveguide was reduced to 0.31 dB/point compared to 2.7 dB/point for conventional straight waveguides.     

Multimode deposited silica waveguide and its application to an optical branching circuit

A fabrication procedure has been developed for multimode deposited silica waveguide (DS guide), consisting of uniform and thick glass layer formation for core and cladding, and amorphous Si mask film for reactive sputter etching. The embedded multimode DS guide with a square core cross section has a transmission loss of 1.3 dB/cm at 633 nm wavelength. Waveguide parameters, such as core dimension, refractive index, and index difference, are similar to those of a multi-mode silica fiber. A multimode optical branching circuit with eight output ports was demonstrated by the above fabrication procedure. Excess insertion loss was 2 dB.     

Elasto-optic loss modulation on side-polished fibre

A thin silica rod is pressed piezoelectrically against the face of a side-polished fibre. In the contact region a local waveguide is induced elasto-optically in close proximity to the fibre core. Coupling to that waveguide attenuates the guided optical power by up to 6 dB. The observed modulation response is flat up to ~12 kHz     

Low-loss fiber-matched low-temperature PECVD waveguides with small-core dimensions for optical communication systems

Plasma-enhanced chemical vapor deposition (PECVD) offers a simple way of fabricating (doped) silica layers on silicon. A new design of the waveguide core allows low-loss fiber matched waveguides with low birefringence without high-temperature annealing. The increased loss of doped plasma deposited silica due to hydrogen incorporation is overcome by reducing the core dimensions and increasing the refractive index contrast. The waveguides can easily be fabricated using standard PECVD technologies and resist masked reactive ion etching (RIE) etching. Integrated optical devices such as 1/spl times/8 power splitters, 1300/1550-nm wavelength multiplexers and thermooptical switches were successfully fabricated and tested.     

Fibre splices with `perfect fibre? strengths of 5.5 GPa, v<0.01

Splices of single-mode fused silica fibre having strengths equivalent to that of the as-drawn fibre of ~800 ksi (5.5 GPa) with a coefficient of variation v of <0.01 are produced by fusion splicing with an H2-Cl2-O2 flame. These results demonstrate that fused silica fibre can be reheated to fusion temperatures and retain original high strength. The results are statistically analysed with respect to variations in breaking load, fibre and splice diameter, and relative humidity.     

Demonstration of a semiconductor external cavity laser using a UVwritten grating in a planar silica waveguide

The authors report the first demonstration of a semiconductor external cavity waveguide laser, modulated at 2.5 Gbit/s over 100 km of standard optical fibre using a UV written grating in a planar silica waveguide as the feedback element     

A guided-wave optical arbiter circuit

An optical waveguide circuit which can be used as an arbiter for priority allocation in data communication system is proposed. The waveguide circuit was fabricated by silica deposition and its basic performance as an arbiter was measured. The average insertion loss and the crosstalk level for a 10-port circuit was measured to be 9.8 and -26.8 dB, respectively. In obtaining a large number of fan-out on a compact substrate, it is important to provide large refractive-index difference between the core and cladding to allow for a sharp bend and to decrease the excess branching loss. The number of fan-out of about 250 is expected on a 50-mm-square substrate.     

Measurement of linear electro-optic effect intemperature/electric-field poled optical fibres

An electro-optic coefficient of r=0.05±0.02 pm/V is reported for a temperature/electric field poled Ge:SiO₂ fibre. The fibre was a commercial, polarisation maintaining, singlemode (633 nm) fibre with a core composition of 18 wt% Ge and a fused silica cladding. Piezoelectric effects are seen at low frequency. Comparison with the r₃₃ coefficient of bulk poled silica suggests that overlap between the nonlinear material and the guiding regions can be further optimised     

Enhanced ESI for prediction of waveguide dispersion in single-mode optical fibres

We provide an enhanced equivalent step index (EESI) approximation for the accurate prediction of waveguide dispersion on monomode optical fibres. Using a quadratic `enhancement function? the waveguide dispersion even for the triangular core profile fibre can be predicted to be between 92 and 100% of its exact value in the single-mode region.     

波导纤维中光线延迟的计算

本文提出一种计算波导纤维光线时间延迟的新方法,并给出了各种折射率分布形式纤维的计算结果.     

Novel means of detecting microwave power using optical fibres

A single-mode optical fibre positioned in a waveguide structure (2.45 GHz) is shown to sense microwave power. The effect is studied quantatively by monitoring the output of an all-fibre Mach-Zehnder interferometer, one limb of which incorporates the test fibre.     

溶胶—凝胶法制备PZT薄膜的结构和波导特性

采用溶胶－凝胶方法制备了ＰＺＴ（５０／５０）薄膜，用椭偏仪和透射光谱分别测量并计算了年鉴备在Ｓｉ（１１１）、石英玻璃基片上薄膜的折射率、研究了薄膜的相结构与折射率之间的关系以及折射率和消光系数的色散关系。用棱镜耦合的方法测量了薄膜的波导损耗，并给出了波导损耗与工艺过程的关系。     

Pulse response and microbending losses of an optical glass-fibre waveguide with a bump in its index profile

It is shown that a short light pulse is split into two separate output pulses when transmitted through a graded-index fibre with a refractive-index bump in its centre. For the fibre investigated, the bump acts as a monomode waveguide. This monomode waveguide turned out to be much less sensitive to microbending than the multimode graded-index waveguide, which is in agreement with existing theories.     

Vibration-induced polarisation modulation of light guided in single-mode optical fibres

The polarisation state of the HE11-mode in a single-mode optical fibre with a fused silica core was varied by mechanical vibrations of the fibre. The accompanying amplitude modulation is suppressed in the experimental arrangement. The influence of the plane of the incident polarisation on the signal modulation is discussed. The measurements were made with both reflecting and nonreflecting fibre endfaces.     

Novel core alignment method for low-loss splicing of single-mode fibres utilising uv-excited fluorescence of Ge-doped silica core

A novel core alignment method for single-mode fibre low-loss splicing without optical power monitoring is proposed. The method is based on the fluorescence of a Ge-doped silica core excited by ultraviolet light. The efficiency of the novel core alignment is investigated.     

Effective Silicon Oxide Formation on Silica‐on‐Silicon Platforms for Optical Hybrid Integration

This paper describes an effective method for forming silicon oxide on silica‐on‐silicon platforms, which results in excellent characteristics for hybrid integration. Among the many processes involved in fabricating silica‐on‐silicon platforms with planar lightwave circuits (PLCs), the process for forming silicon oxide on an etched silicon substrate is very important for obtaining transparent silica film because it determines the compatibility at the interface between the silicon and the silica film. To investigate the effects of the formation process of the silicon oxide on the characteristics of the silica PLC platform, we compared two silicon oxide formation processes: thermal oxidation and plasma‐enhanced chemical vapor deposition (PECVD). Thermal oxidation in fabricating silica platforms generates defects and a cristobalite crystal phase, which results in deterioration of the optical waveguide characteristics. On the other hand, a silica platform with the silicon oxide layer deposited by PECVD has a transparent planar optical waveguide because the crystal growth of the silica has been suppressed. We confirm that the PECVD method is an effective process for silicon oxide formation for a silica platform with excellent characteristics.