In order to enable optical systems to operate with a high degree of compactness and reliability it is necessary to combine large number of optical functions in small monolithic structures. A development, somewhat reminiscent of that that took place in Integrated Electronics, is now beginning to take place in optics. The initial challenge in this emerging field, known appropriately as "Integrated Optics", is to demonstrate the possibility of performing basic optical functions such as light generation, coupling, modulation, and guiding in Integrated Optical configurations. The talk will review the main theoretical and experimental developments to date in Integrated Optics. Specific topics to be discussed include: Material considerations, guiding mechanisms, modulation, coupling and mode losses. The fabrication and applications of periodic thin film structures will be discussed.

Integrated optics

We present a method for determination of the random-orientation polarimetric scattering properties of an arbitrary, nonsymmetric cluster of spheres. The method is based on calculation of the cluster T matrix, from which the orientation-averaged scattering matrix and total cross sections can be analytically obtained. An efficient numerical method is developed for the T-matrix calculation, which is faster and requires less computer memory than the alternative approach based on matrix inversion. The method also allows calculation of the random orientation scattering properties of a cluster in a fraction of the time required for numerical quadrature. Numerical results for the random orientation scattering matrix are presented for sphere ensembles in the form of densely packed clusters and linear chains.

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Calculation of the T matrix and the scattering matrix for ensembles of spheres

Using a simple approach based on the scalar finite element method, propagation characteristics of multilayer chan- nel waveguides are calculated. The effective index, modal field, confinement factor, far-field intensity pattern, and radiation angle of the far-field pattern (full width at half maximum intensity) for multilayer channel waveguides formed with multiple quantum well (MQW) materials and with the MQW materials replaced by a single homogeneous material with the root mean square value of the refractive indexes are compared. Numerical results confirm that the root-mean-square-value approximation, which has been widely used for planar MQW (two-dimensional) waveguides, is useful also for MQW channel (three-dimensional) waveguides with a large number of layers.

http://ieeexplore.ieee.org/iel1/50/7266/00293974.pdf

A Comprehensive Analysis of

Visual-assisted guidance of an ultra-thin flexible endoscope to a predetermined region of interest within a lung during a bronchoscopy procedure. The region may be an opacity-identified by non-invasive imaging methods, such as high-resolution computed tomography (HRCT) or as a malignant lung mass that was diagnosed in a previous examination. An embedded position sensor on the flexible endoscope indicates the position of the distal tip of the probe in a Cartesian coordinate system during the procedure. A visual display is continually updated, showing the present position and orientation of the marker in a 3-D graphical airway model generated from image reconstruction. The visual display also includes windows depicting a virtual fly-through perspective and real-time video images acquired at the head of the endoscope, which can be stored as data, with an audio or textual account.

Catheterscope 3D Guidance and Interface System

Fiber optic sensor technology has experienced tremendous growth since its early beginnings in the 1970's with early laboratory demonstrations of fiber optic gyros and acoustic sensors and the introduction of the first commercial intensity and spectrally based sensors. These early efforts were followed by a tremendous growth of interest in the 1980's when the number of workers in the field increased from perhaps a few hundred to thousands. The result was the introduction in the 1990's of the first mass produced fiber optic sensors that are being used to support navigation and medical applications. The number of fiber optic sensor products can be expected to grow tremendously in the years to come as rapid progress continues to be made in the related optoelectronic and communication fields. This paper provides an overview of some of the technologies being used to support fiber optic sensor development and how they are being applied.

Fiber optic smart structures

In this paper we report the fabrication of a robust, tunable single-longitudinal-mode compound-ring Er/sup 3+/-doped fiber laser. The laser is fundamentally structured on an all-fiber compound-ring resonator in which a dual-coupler fiber ring is inserted into the main cavity. When combined in tandem with a mode-restricting intracavity tunable bandpass filter, the compound-ring resonator ensures single-longitudinal-mode laser oscillation. The laser can provide up to 20 mW output power over much of its 1525 to 1570 nm wavelength tuning range. The short-term linewidth of the laser output measured is less than 5 kHz. The laser frequency is actively stabilized for a long time by exploiting the inherent filter nature of the compound-ring resonator. The reduction of an associated frequency modulation is also discussed in detail.

Stable single-mode compound-ring erbium-doped fiber laser

An all-fiber sensor capable of simultaneous measurement of temperature and strain is newly presented. The sensing head is formed by a fiber Bragg grating combined with a section of multimode fiber that acts as a Mach-Zehnder interferometer for temperature and strain discrimination. The strain and temperature coefficients of multimode fibers vary with the core sizes and materials. This feature can be used to improve the strain and temperature resolution by suitably choosing the multimode fiber. For a 10 pm wavelength resolution, a resolution of 9.21 mu epsilon in strain and 0.26 degrees C in temperature can be achieved.

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Simultaneous measurement for strain and temperature using fiber Bragg gratings and multimode fibers

A comprehensive theoretical analysis of the compound phase-shifted uniform fiber Bragg grating (FBG) filter is presented. The transmission characteristics are examined by a transfer matrix formulation. It is shown that the transmission spectrum of such a filter is significantly controlled by the ratio of the grating lengths. By suitably choosing the ratio, a quasi-flat-top spectrum may be obtained. The general condition for the optimum case is derived. This characteristic makes the compound phase-shifted uniform FBG filter particularly advantageous for applications in wavelength-multiplexed optic-fiber communication systems.

Phase-shifted Bragg grating filters with symmetrical structures

The strain and temperature sensitivities of three common commercial high-birefringent polarization-maintaining fibers (bow-tie, polarization-maintaining and absorption-reducing, and elliptical core fibers) have been measured by using a dynamic polarimetric method. The experimental setup and measuring process are described in detail. Where possible, the measuring data are compared with published data, and good agreement is obtained.

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Temperature and strain sensitivity measurements of high-birefringent polarization-maintaining fibers.

In this letter, we propose and demonstrate a simple and novel technique to get multiwavelength operation in the L-band by using an elliptical core erbium-doped fiber. The principle of operation is based on the anisotropic gain effect in a polarization-maintaining fiber. Stable multiwavelength operation is achieved at room temperatures. The lasing lines may be controlled by a polarization controller.

John W. Y. Lit

Papers

Stable single-mode compound-ring erbium-doped fiber laser

Simultaneous measurement for strain and temperature using fiber Bragg gratings and multimode fibers

Phase-shifted Bragg grating filters with symmetrical structures

Temperature and strain sensitivity measurements of high-birefringent polarization-maintaining fibers.

L-band multiwavelength fiber laser using an elliptical fiber