Main aims of the Symposia Series "Optical Fibres And Their Applications" are as follows: - critical estimate of lightguide technology development in this country during a three years period (from now a two years period), - creation of suitable conditions for presentation of new scientific and technical laboratories entering this technology area.

The ternary glass forming system Si02 - B203 - K20 including small amount of refractive index makers like BaO, Zr02, Ge02, PbO, La2O3, Ta205, typical for fiber optic application, was chosen for consideration. Preparation of glasses, their properties like refractive index, coefficient of thermal expansion, transmission and thermal characteristic points are reported. The non-linear relationship between properties and composition is discussed.

A new technological method of optical fibre production (called here Multicrucible-zone--Diaphragm), being a developed version of double crucible and rod-in-tube technologies, has been presented. Monomode optical fibres with multistep - index and gradient profiles for flatened dispersion characteristics and sensors applications have been pulled and measured. Diffusion processes of modifying ions in MZD preforms have been investigated. Exemplary details of the technological process are given and debated. The major data of pulled fibres are presented.

The defects connected with the presence of phosphor in both optical and EPR spectra are examined. In the visible spectral range the color centres connected with the PO4-2 defects (POHC) were investigated. The spatial distributions of the respective bands found both for optical and EPR ranges were attributed to the lower valency phosphor defects. The thermally generated changes in both the types of spectra were recorded. The examinations of yellow luminescence (in the 500-750 nm range) connected with Ge06 and conditioned by the phosphor presence have been initiated.

In the paper the results of investigations of the distributions of: UV transmission, POHC color centers transmission after γ irradiation, blue Ge2+ luminescence, yellow Ge06 luminescence and germanium concentration vs radius r of the preform core are reported. A comparison of the said distribution with the distribution of Δn is given

A method for analyzing guided modes of doublecore step index dielectric waveguides with arbitrary cross-sectional shape and index difference between the cores is presented. It is based on the null field method and is formulated in rigorous vectorial form in terms of the transversal part of the magnetic field. A novel S-A classification of guided modes in dielectric waveguides which possess some kind of symmetry is introduced. Circular cores case as the canonical example of a fiber with the "rectangle" symmetry is worked out. It shows the accuracy and usefulness of the method and provides comprehensive characterization of S-A modes in such fibers. Analysis of the directional coupler performance in terms of introduced modes is also presented.

Single-mode fibers of pure silica core and F-doped clads exhibiting a low dispersion over a wide wavelength range are discussed and numerical results of some propagation characteristics of dispersion-compensated nulticlad fibers are presented. In computations, the very accurate numerical methods and extended precision arithmetic were used. The calculations include the propagation constant, and the dispersion coefficient versus a wavelength, cut-off frequencies of the first mode, a power and field distribution of the fundamental HE11 mode, the spot size. Tolerance of the geometry of the fiber and concentrations of the F-dopants in pure silica are analysed showing numerically what is an influence of them on a dispersion characteristic. Some results to be discussed are directly applicable to the designing of a truly single-mode F-doped silica fiber.

30 light Emitting Diodes /LED's/were used for study of their parameters. There were made such measurement as: - optical pover vs. forward current - frequency baseband response - spectral characteristics - climatic test In this paper the results of these studies are presented. Since the diodes were examined within temperature range - 40 ... + 55°C, it was possible to determine temperature coefficients of optical power and wavelength. Finally, the possibilities of domestic LED's application in transmission systems are described. There is given also an example of LED applica-tion in the experimental fiber optic line.

A three-dimensional analytical thermal model of the homojunction Burrus-type light-emitting diode is presented in this work. Boundary conditions of the thermal conduction equation are formulated on the basis of analog electrical model of the heat-spreading process within the diode structure. The heat-flux penetration into the high-resistivity region and its conduction through the dielectric film, the current-spreading between the upper contact and the active region as well as the temperature dependence of the thermal conductivity are taken into account. The Green functions method is used for solving the thermal conduction equation. Its solution enables us to analyze a relative influence of various construction parameters on temperature increases in the active region.

The three-dimensional thermal model of the homojunction Burrus-type light-emitting diode, which was presented in the previous work, is adapted to the double-heterostructure Burrus-type light-emitting diode. The dependence of the parameters of the model on the AlAs mole fraction, x, in the passive layers is taken into account to this end. It appears that from the point of view of the lowest temperature in the center of the active region, both low and high values of x are favorable and the most unfavorable value of x seems to be about 0.25. On the other hand, from the point of view of the most homogeneous temperature distribution within the active region, x should be as small as possible.

Optical coupling of a high power pulse operating heterostructure broad contact laser with an optical fiber has been investigated.The optical fiber was of a multimode gradient type with the core diameter 50 μm and 200 μm and butt-ended.The efficiency of such coupling has been found to be 12% and 44%, respectively and might vary significantly when the fiber was displaced with respect to the laser emission area.Experimental data are compared with the theoretical predictions. The high power lasers equipped with optical fiber pig tails can be useful for numerous applications in the fiber optic technology.In particular they can be recommended as a signal source in the fiber optic measurement systems.Parameters of such lasers and the output power versus current characteristics are described in the paper.

Exploitation parameters of a waveguide mostly depend on the distribution of the refractive index in it. Therefore, control over the distribution of the refractive index in the waveguide preforms out of which the waveguides are drawn is necessary in waveguide production and in working out a proper technology of preform production. Interference methods prevail in refractive index distribution measurements because of their great measurement accuracy. Observation of the preform along its axis provides us with information about the actual refractive index distribution in this preform. In order to obtain this information: it is necessary to cut a slice out of the preform and to place it in the measurement setup so that the light beam goes along the symmetry axis of the preform, slice. Owing to the fact that the refractive index does not change along the run of the beam parallel to the preform axis, this method makes it possible to determine the actual refractive index distribution. The method of three interferograms is a destructive method and it makes it possible to measure the refractive index distribution with an accuracy of 1x10-6 for a slice of 1mm thickness as well as the sample thickness distribution. Although the method presented here is simpler, it constitutes a model method for nondestructive methods. This method makes it possible to make measurements of varying accuracy whether we take into account the distribution of the thickness of the examined slice based on other measurements, or whether the slice wedge alone is considered, or whether the slice thickness is assumed as constant.

The measurement method presented in this paper is a destructive method. The refractive index distribution n(x) is calculated on the basis of the reconstructed wave front g (Figure 1.) which is created as a result of plane wave g' going through the examined preform perpendicularly to its axis. When reconstructing wave front g and calculating n(x) it is assumed that the preform and its refractive index distribution have cylindrical symmetry.

In classical interference the examined wave front interferes with the plane (model) wave front; whereas in shearing interference two wave fronts interfere with each other - one of them is, in some definite way, transformed in relation to the other. In radial shearing interference two collinear fronts with propagation direction interfere with each other - one of them is transversely magnified in relation to the other. Radial shearing interference can be realized in different systems by various optical elements. Two interferometers measuring the distribution of a refractive index of waveguide preforms are presented below.

The Interferometer Testing Preforms (ITP), which has been designed and made at the Institute of Physics, Technical University of Wroclaw, is used for very precise measurements of the refractive index in waveguide preforms. It can work in four measurement setups.

We consider the sensitivity of optical receiver used in digital fiber-optics communication link. This sensitivity is understood as the smallest optical power which must be fed to the photodiode to assure BER = 10-9. It is assumed, that the only sources of noise are the photodiode and the first stage of receiver preamplifier. Approximate expressions describing advantages of using APD over PIN diode was derived. The optical transimpedance receiver for 34 Mb/sec system was used as calculation example.

The equipment described here, developed in Institute of Telecommunications and based on the swept frequency method enables to measure amplitude - frequency response of fiber samples, field installed optical fiber lines and LED's in the frequency range up to 600 MHz. Measurements of modal dispersion in optical fibers are performed in the 850 nm band, maximum permissible fiber attenuation is 30 dB. The set - up consists of wideband frequency response analyser, modulated GaAlAs CW laser source and optical receiver with APD photodetector. Non - standard applications of set - up components are also possible, such as short optical pulses monitoring. Additionally, examples of results of measurements made on graded index fibers manufactured in Poland, optical fiber line installed in Lodz and fiber optic LED's CQYP - 06F are presented.

A TV - camera with monitor and specially designed video analyser are employed for measurements of geometry and numerical aperture (N.A.).Measurements are fully automatic, but complicated calculations still have to be made manually. This paper also discuss the solution for obtaining the optical power vs. voltage characteristics of the camera vidicon and to find the equipment resolution. The results of measurements performed at IT were confirmed at French CNET - Lannion B laboratory. The comparison showed good similarity.

There are 3 popular methods for measuring of optical fiber attenuation i.e. cut-back, backscattering and insertion loss. In field applications the last two methods are frequently used in spite of the best accuracy of the first one. The backscattering has a disadvantage of limited dynamic range in comparison with the other two, but is very easy to apply. For the whole long link attenuation measurements the insertion loss method is in popular use. It's main drawback is an error resulting from unknown connector loss. This paper presents an explanation of all these methods with error analysis as well as field tested modification of the insertion loss method aimed to eliminate errors caused by connector loss.

Results of the selective etching treatments of the optical fibres are presented. Owing to the etching rate dependence on the dopant concentration, the microstructure of the optical fibres was visualised with the aid of scanning electron microscopy /SEM /. The qualitative distribution of the Ge and Si concentration across the fibre diameter is also investigated. Multi-mode and single-mode fibres were investigated by using different etching solutions based on HF. The doped or/and undoped areas were removed and concavities or convexities were etched on the fiber faces. Investigations permitted qualitative estimations of the dopant distributions in the fibre core and to obtain information about the quality of the fibres. The results are illustrated by SEM patterns.

When light emitting diodes and semiconductor lasers are being produced, there is often a need of quick measurement of some parameters. Besides current-voltage and current-optical power characteristics we usually measure near field and far field radiation patterns and spectral characteristics. At the Telecommunications Institute of Warsaw University of Technology a number of instruments for quick measurement of these parameters have been designed. A common feature of all these instruments is the usage of TV-camera as an image converter and a TV-monitor to present the results. This permits a quick measurement of important parameters of radiating sources.

OSEE decay curves for fibre preforms made from porous silicate glasses have been measured. Six glass types being final material of different processing staged were used as specimens. A point in which the decay curve practically coincides with the slowvarying term has been determined from the decay curve distribution. The parameter seems to be characteristic for given glass structural defect types. Exponent parameters have been also calculated which describe slow-varying part of the curve. Thus it seems that OSEE may be a good method for determination of imperfection degree of fibre preforms.

In this paper FORS constracting using multimode optical fiber will be presented. Described device manufactured in our laboratory using only domestic fabricated components allowed on Sagnac effect obtaining and was initialy investigated.

The fiber-optic instrument of ability to measure roughness of surfaces has been built. It works in the range of profil mean deviation 20 nm <Ra <150 nm. Light of 0,88 μm wave length is led by the fiber to the surface and is analysed by other fiber fixed in a focal plane of the lens. The device is used to check the base plate in microelectronic semi-conductor technics.

The evaluation of state of surface roughness is indispensable in many technological processes. It is important as far as fabrication of high quality optical and mechanical surfaces is concerned. Many parameters have been introduced which are connected with characteristics of microgeometry of surfaces, however, there is no direct method of their measurement. On the other hand, there exist well known standarised characteristic values of roughness but most of the methods of their measurements have disadventages such as restrictions on their applications, exertion of pressure on surface, inspection of the area instead of a line and excessive consumption of time. Optical methods do not have all of these disadventages as they are nondestructive, they allow for quick and repetitive measurements of characteristics of two dimensional surfaces in a wide range of roughness. The main aim of the paper is to introduce a design of optoelectronic sensor for surface roughness of size larger than the wavelength of light used for measurements.

The paper presents the results of temperature measurement by using multimode two-fibres sensor. Fibres are used to light a semiconductor sample and to receive the transmitted light through the sample.Change in transmission of light passing through the semiconductor material is caused by shift of absorption edge according to the temperature variation. As a source of light and as a photodiode the typical elements of fibre-optic communication systems were used. Semiconductor plate with temperature control transmission was matched by comparison of its absorption edge to spectral characteristics of light-emiting diode.

The paper presents a laboratory model of the time-space converter made as an integrated optics device. Optical signals from a single-mode optical fiber are introduced into a planar waveguide made by titanium doping of lithium niobiate. For high efficiency of coupling from fiber to planar waveguide, directly through the edge, a system of microlenses is used. Deflection of light in the planar waveguide is obtained by an application of ultrasonic surface waves according to the Bragg configuration. Two electrode arrays work with frequencies 124 MHz and 174 MHz and they enable obtaining three positions of the light beam. Outgoing fibers are directly coupled to the edge of the planar waveguide.

The paper presents the principle of construction and work of the measuring apparatus used to record a distance of a driving element of contactor mechanism and also to record contact tilt and characteristic times when contacts are opening. In the apparatus there have been used linear fiberscopes converter for measuring displacements and a recording system coupled with microcomputer to convert digital information received from the tested object. The paper also presents generally various other applications of the measuring apparatus.

Output signal from a position sensitive detector illuminated by means of an optical fiber was measured. Light sources were light emitting diode CQYP 06W or CQDP 42 W. Linear characteristics of the signal height as a function of light spot positions were obtained. Output signal from the detector was also measured using two optical fibers with a fixed distance between them. The measured slope of the linear characteristic for one optical fiber was a1 = [10,49 ± 0,14] mV/mm and for two optical fibers: a2 = [20,07 ± 0,20] mV/mm Use of two optical fibers causes a rapid change of the output signal and results in a sudden jump of the characteristic slope. The results point to a possibility of an application of position sensitive detectors for an analysis of light spot position using one or more optical fibers.

Measurements of the cw Nd:YAG laser power transmission /up to 90 W/ through the fiber optic delivery system employing several, different fibers and observations of thermally induced damages in tested fibers are reported.

A simple practical and controllable beam expander can be constructed from a single-mode optical fibre which has been overjacketed in a capillary of lower refractive index and then tapered. The properties of such an expanded beam in a gap device are also investigated.

The authors of the paper constructed a model of an automatic spectrophotometer for measurements and registration of quickly-changing spectral destributions. In the construction of the device, fiber-optic elements of high accuracy, special geometry and a microprocessor set-up were utilized. The fiber-optic link was made of appropriate fibers produced by double crucible method from multi-component glasses.

The paper presents a conception of an optical fiber colour recognition sensor designed for applications in robotics. A theoretical model of the sensor and some results of its computer analysis are described as well as results of experimental investigations in the sensor. An example of an application of the sensor to a robot sorting coloured objects is also presented.

The paper presents a conception of an optical fiber proximity sensor designed for applications in robotics. A theoretical model of the sensor is offered as well as its computer analysis, including an examination of the effects of the sensor design parameters on its characteristics.Some results of experimental studies on the sensor are presented together with an example of the sensor's application in an industrial robot for the detection of obstacles on the robot arm's trajectory and control of their avoidance.

The prototype of equipment for service of the measuring units of power high voltage line is presented. That system is composed of the transmitter /with A/D conversion/, optical fibre data link and receiver feeding the output into the microcomputer. The application of this equipment in the automatic protection system protecting the power network against short-circuit is described.

The paper contains a review of a few of experimental optical fibre multiservice and multibranch local area networks /LANs/. Systems accomplish transmission, distribution and processing of analog or digital signals from numerous sources or measurement terminals. The authors put stress also on the possibility of combining transmission properties of fiber optic networks with fibre optic sensors. Several construction problems and chosen properties of multiport /multiterminal/ optical buses /networks/ have been considered. All examination systems of optical fibre LANs are discussed in respect of application them as telemetric, transmission, telesignaling and telecontrol systems for the power electric equipments and systems. Theoretical considerations are illustrated by multiservice system for HV power substation.

In concurrent gas and liquid flow in a channel there may occur various two-phase flow regimes, depending on the phase flux. In Fig.l are presented the flow regimes in two-phase gas-liquid flow in a vertical pipe.

This paper describes operation, design and results of laboratory tests of optical fiber transmitter and receiver for 480 channel /34 Mbit/s, third level of European hierarchy/ PCM telephone system. These units are designed to operate with multimode graded index fiber on 880 nm wavelength. In transmitter the Siemens SFH 408-880 Ga Al As laser diode is used. The receiver employes the FTL type silicon fiber optic APD, featuring a sensitivity of -49.8 dBm for BER = 10-9 and a dynamic range of 31 dB. Repeater spacing may be as long as 12 km taking into account adequate margins, which is satisfactory for urban networks.

Quality of arc fusion splices despends strongly on equipment used and proper selection of splicing process parameters, such as arc current and power, sequence and duration of splicing steps. In Institute of Telecommunications, Warsaw a FOS - 2 type optical fiber splicer was developed, featuring automatic control of 3 - step splicing process, according to a program selected by operator. Laboratory tests on fusion splicing of 50/125 μm multimode graded index silica fibers allowed to find optimal arc current and duration. Average losses of splices made in optimal conditions were below 0.05 dB.

An experiment with precise output light stabilization for analogue FO transmitters is presented.Results measured are compared with theoretically derived equations for the stabilizing loop. A considerable role of the source-photodetector spectral mismatch in the light stabilizing loop has been proved,as well as some practical improovement advice is proposed.

Jitter factor is defined as the ratio of jitter standard deviation (j.s.d) at the output of the timing circuit when to the input a correlated binary pulse train is fed, to the j.s.d. at the output of the timing circuit when pulses in the tuned circuit input train are statistically independent. It is assumed that pulses in the input train are correlated due to the line code and that the train is described by a function of Markov Chain. Assuming a simple model of timing extraction circuit, a method of evaluation of jitter factor is outlined and some examples are given.

The problem of word synchronization process for transmission codes for digital transmission systems has been studied using statistical decision theory. The theory shows that the number of observations required to take a decision for constant probe algorithm is, average, larger that the number of observations necessary to take a decision for sequential algorithm. The conclusion for constant probe word synchronizer and sequential word synchronizer was verified by experiments with digital transmission system on optical fiber.

The paper presents several useful optical instruments for performing measurements and various auxiliary technological operations in the field of optical waveguides. A technical characteristics of each instrument has been given.

The theoretical studies and experimental researches results of Bragg acoustooptic interaction in planar waveguide are presented. The graded index waveguide was obtained by the Ti diffusion into a lithium niobate single crystals. The interaction efficiency analysis was made versus acoustical power for both TE and TM modes. The wide-band 200 - 400 MHz transducer has been used. The 30 % interaction efficiency was obtained for the 0,5 W of acoustic power.

TE-TM mode conversion caused by Faraday rotation has been studied in (Y,Ca)3 (Fe,Ge)5O12 garnet films. This conversion was investigated as a function of magnetic field perpendicular to the sample plane H⊥ and in the plane H//. Magnetic domain structure (MDS) influence on the TE-TM mode conversion ratio R was found in the histeresis of R(H//). The character of dependence is connected with behaviour of domain structure. The measured for saturated sample R(H⊥, H//) dependence could be qualitatively explained by theoretical model developed for monodomain structure.

In the paper a compensatory method of measurement of planar optical waveguide attenuation has been presented. This method allows us to precise attenuations measurements. It advantage consists in the fact that the results are independent of the laser power fluctuations and efficiency of coupling between the detector and the waveguide.

Integrated-optical generalized multiple-focus Luneburg lenses have been contrasted to those with single focus. The theoretical background has been given along with the preparation details. Performance of double-focus lenses has been presented and the possible applications of the multiple-focus elements briefly outlined.

This paper presents a solution for the design problem of a planar inhomogeneous optical waveguide with the refractive-index profile which enables propapation of the N TE modes with prescribed propagation constants. Solutions of the Gelfand-Levitan equation for the case of reflectionless potentials are used to obtain formulae which determine N-parameter family of functions describing refractive-index profiles that support modes with given propagation constants. The analytical form of the solution of the problem is obtained in terms of hyperbolic functions. The formulae for the choice of N arbitrary constants which produces a symmetric refractive-index profile are given. The exact modal solutions for derived refractive-index distributions are presented. Some special cases are discussed in detail.

Light diffracted on magnetic domain structure changeable by external magnetic field can be used for fiber - optic switches. Quantitative and comfortable received information about the changeable diffracted light distribution as a function of both polar and azimuthal angles σ, γ is important for this device. Two fully automated spatial filter stations S1 and S2 were constructed for σ and γ angle light distribution analysis, respectively. The S2 station gives new opportunities for analysis of domain structures preference induced e.g. by external magnetic fields. Samples with different σ quality parameter from (Y,Sm,Bi)3 (Ge,FE)5 O12 series grown on (111) GGG substrates were investigated. The obtained results were discussed in comparison with results earlier published.

The thermooptic effects in soda-lime glass has been discussed. The behaviour of the thermooptic switch has been designed taking into consideration the change of the index of refraction and the formation of a thermally-induced lens around the miniature heater.

The report with the technology production of nonuniform holographic gratings by means of argon laser type ILA-120 manufactured by Carl Zeiss Jena GDR. The points relief phase holograms were recorded in the AZ-1350 positive photoresist. The gratings had variable period from 0,4 μm to 1 μm and were sized up to 35 mm diameter. The grating obtained in the photoresist layer was coated by Al film, aproximately 1500 Å. The hologtaphic gratings were applied in the experimental pattern of wavelenght multi and demultiplexers reguired in the WDM optical communication systems.

The most recent formulation of the geodesic lens problem is briefly discussed and proved very useful in developing novel solutions. A new family of perfectly imaging lenses is presented, which lends itself extremely well to the integrated-optical circuits. These lenses possess smooth transition between the cyllindrically-symmetric depression profile and the flat guide. Moreover, the rounded section profile is characterized by non-vanishing local curvature radius. This should minimize radiation and scattering losses by the guided modes.

In this paper theoretical and experimental investigations on the passive integrated optical components are presented. Planar waveguides were produced by the K+ ↔ Na+ or Ag+ ↔ Na+ ion exchange and waveguide couplers were made by the selective diffusion of Ag+ ions in soda-lime glass. Experimental investigations on the planar waveguide structures show the existence of certain anomalies in refractive index distribution, caused by the segregation of natural glass components. For the production of gradient microlenses, electric-field-assisted diffusion process of Ag+ ions was applied. For this purpose, the formation of three-dimensional refractive index distribution due to electrothermal ion exchange process was considered. The obtained refractive index distribution was used for the numerical solution of ray trajectory equation in gradient microlenses.