In this paper w dicus th c1sign of the two mode interference and of the di rect I ona oup1 er types mul ti /demul t I p1 exer real i zed in ion exchanged gIas waveguides. The proposed procedure takeE into account the coup ing with the fiber the effect of inputoutput tranition and how the possibility to obtain polarization independent devices also with unburied waveguide. I .

Single-mode fibers and components are increasingly being used in short distance applications. Fiber—to-the-home programs are being implemented and require high performance, low-cost single—mode components such as splitters and wavelength division multiplexers (WDMs). The work presented here is based on planar ion exchange technology. It is well adapted to producing compact devices integrating several functions. For example, single-mode achromatic lxN splitters comprised of multiple integrated Y-junctions are already available with low, wavelength-independent insertion loss (1,2). The ability of future networks to support multiple wavelengths requires the use of WDMs. Research work already has been reported on K and Cs based ion exchange WDMs (3,4). Results on low loss Tl ion exchange WDMs are presented in this paper.

A high resolution Integrated Optical Wavelength Division Multiplexer (WDM) has been successfully developed to increase optical fiber communication capacity through wavelength multiplexing/demultiplexing. The Integrated Optical WDM uses multiple gratings to deflect different wavelengths from one multiple wavelength optical input into many different directions. Each pre-recorded grating deflects one and only one wavelength to an arbitrary but pre-determined angle. The planar optical waveguide with a holographic grating was fabricated monolithically through the standard ion-exchange process. A layer of holographic material (DCG) was then spun on top of the planar waveguide. Finally a phase grating was created by interfering two Argon laser beams on the substrate''s surface. The angle (23) between the two Argon beams and the glass substrate orientation angle (4) completely determines the wavelength selection characteristic. An optical signal interacts with the holographic gratings evanescently when light is propagating in the waveguide. Due to the device geometry the light-hologram interaction length can be made very long. The long interaction length ( coupled with the large index modulation depth of DCG (En 1) will dramatically increase the wavelength selection resolution and deflection angle resolution. Presently a 7 channel WDM with 6nm channel separation and 6 angular separation has been achieved. Theoretical studies showed that hundreds of channels with extremely narrow wavelength selectivity resolution (mm) and deflection angle resolution (0. 2) are achievable with a 1mm interaction length. With an even longer interaction both number of channels and resolution can be increased by another order of magnitude.

We propose devices for wavelength-division muliplexing based on coupling between different modes in optical fiber. A mode-selective directional coupler (MSDC) couples the LP01 mode of one fiber to the LP02 mode of a second fiber with a bandwidth. -length products of about 4 nmcm an improvement of a factor of 10 over LP01 + LP01 coupling. Refractive index gratings written with UV light can also couple light from the LP01 to the LP02 mode either in a counterpropagating way (Bragg grating) or a codirectional way. Combined with the MSDC they can make efficient channel-drop filters.

Wavelength Division Multiplexers (WDM) are used to inject pump light into erbium doped optical fiber amplifiers. Ideally the WDM should couple 100 of the pump light into the amplifier without coupling away any of the signal light while maintaining low insertion loss at both wavelengths. In this paper we describe both 980/1550nm and 1480/1550nm all fiber WDM5 made with the fused biconical taper process.

The paper is concerned with a wavelength mux-demux device for multimode and monomode fibers assembled through micro-optic technique. The proposed device makes use of a 45 incidence dichroic filter as a dispersive element and of GRINrod lenses as collimating/ focusing optics. It was designed utilizing two glass prisms with isosceles triangle cross-section between which the filter is inserted while three GRIN lenses connected to the fibers are cemented on the lateral faces of the prisms thus forming a monolithic block. Two different prototypes of the device have been constructed: the first one making use of multimode fibers and the other one utilizing monomode fibers. Narrow band-pass filters centered on the working wavelengths were also inserted on the output ports so to reduce the cross-talk. A description of the two device assembling and characterization measurement are reported.

The interferornetric properties of an abrupt nonadiabatic taper in an optical fiber can be used to create an all fiber wavelength filter. To date the maximum attenuation possible from a single taper has typically been 4 to 5 dB. In this paper we report the realization of single taper filters with significantly unproved performance. Typical optical properties for 1300/1550 nm filters include as much as 30 dB attenuation at the stop wavelength and less than 0. 5 dB insertion loss at the pass wavelength. Similar filters have been built for other wavelength combinations including 980/1550 and 1480/1550 mu. The operation performance and application of these high isolation single taper filters will be presented and discussed in this paper.

Over the last few years the fused biconical taper (FBT) process has been the technology of choice for fabricating passive fiber optic couplers. The FBT couplers can be made with a wide variety of fiber types and exhibit excellent optical and envirornnental characteristics. Recently much attention has been given to the fabrication of compact MxN singlemode star couplers for future local subscriber loop applications. Some of the systems being considered utilize passive star architectures which require singlemnode star couplers to split the light to a multiple number of ports or residences. In this paper we report the fabrication of true lxN and MxN singlemnode tree and star couplers using the fused biconical taper techniques. In addition to good optical uniformity and insertion loss the fused couplers offer the same environmental stability and long term reliability that are characteristic of standard FBT couplers. A discussion of the optical and environmental data will be presented.

A CW CO2 laser is used to etch micron-scale taps in the cladding of multimode silica optical fibers. The smooth surfaces of the etched grooves directionaly radiate a small fraction of the propagating light energy which can be easily and precisely controlled via the laser parameters. The radiation pattern from the tap is in reasonably good agreement with initial theoretical calculations. This technique allows computer controlled rapid and inexpensive fabrication of high quality fiber optical taps which are needed to realize new fiber optical systems.

2 X 2 fused fiber evanescenttype couplers are analysed for distributed coupling depending on arc temperature profile. During fusion core-to-core fiber spacing and hence coupling coefficient between the two fibers varies along the interaction length. The analysis is based on the surface tensile and viscous force equilibrium during fusion. Arc current determines a particular temperature profile. Functional dependance of coupling coefficient c(z) on position z along the coupling length is derived for various arc currents. A theoretical model is developed to analysis the coupling for 2 x 2 and twin-core single -mode(SM) fiber couplers. Effective interaction length determined by arc currents and number of arcstrokes is calculated. Coupled power is finetuned by controlling initial clad thickness arc current and fusion time. The excess loss and devia tion for 2 x 2 SM fiber coupler are0. 12 and0. 04 dB respectively. The strength becomes maximum for a fusion time of 2. 5 sec. N x N couplers are proposed finally. Preservation of cores and their finite separation in a single plane reduces loss deviation and nearly preserves the state-of-polarization (SOP) of the input signal.

We study the output of a gain switched diode laser as a function of the pumping parameters. Experimentally we look at the output pulse shape height and width timing conditions and stability. Theoretically we calculate the conditions under which a gain switched diode laser is optimized with respect to the width of the injection current pump pulse. We find for both biased and unbiased operations that a current pulse of approximately 20 psec corresponds to a Dirac delta function a situation which yields the shortest most intense output pulses. A sensitivity analysis performed on an analytic distillation of the model gives us design considerations for diode lasers with improved stability.

Linewidth and frequency stability of a semiconductor laser are important parameters for coherent optical communications. Several groups have constructed optically stabilized semiconductor lasers (OSSL) using resonant optical feedback from a Fabry-Perot cavity. This technique requires active (electronic) control of the Fabry-Perot cavity to frequency lock the laser. We have developed a new OSSL incorporating a rubidium vapor cell immersed in a dc magnetic field as an optical feedback element. The OSSL optically self locks to sub-Doppler features of the rubidium spectrum without using electronic frequency control circuits.

We have developed a 1.55um superluminesent diode using a revolutionary structure. A light diffusion surface is placed diagonally on the active layer within the device to suppress the lasing action, and V—groove structure is applied to achieve high coupling efficiency into a single—mode fiber. Superluminescent diode characteristics were achieved in the range from 0 to 50C, and the coupled power into a single—mode fiber reached 0.5mW.

Directly modulated semiconductor lasers exhibit a dynamic wavelength shift arising from the gain-induced variations of the laser refractive index. It is an accepted fact that the input current pulse shape plays an important role in the frequency chirping (wavelength shift) of directly modulated semiconductor lasers. This paper gives large signal analysis of the dynamic frequency chirping due to the gain-induced variation of the laser refractive index for four different input current pulse shapes. The laser is biased above threshold for the analysis. The rate equations are solved numerically and the frequency chirping and carrier density variations for the four input current pulse shapes are compared.

The massive use of lightwave communication technology in the trunking and distribution parts of the networks brought the need for high efficiency optical fiber splicing methods. Among others arc fusion splicing is today largely used during installation and rearrangement of optical links. In this splicing method the mechanical strength around the splicing point is greatly reduce due to coating stripping. Our results with brazilian optical fiber aging tests show that the tensile strength average is 0. 55 GM/rn2 and the static fatigue of 0. 14 GN/m2is dangerous for the splicing part. Therefore the protection and the reinforcement of the splicing portion are intended to avoid optical and mechanical degradation. This paper examines the protection level given by heatshrinkable sleeves showing the results obtained from optical and mechanical measurements which are on multimode and singlemode fiber splices. The splicing characteristics were measured under normal conditions and after exposure to termal and wet adverse environments.

A new technique is presented for the recording of small holographic lenses in silver halide emulsion for replay in the near infrared region. The work described was carried out with a view to producing lenses for optical fiber interconnection for which the preferred wavelength is in the 1200-l600nm band. The sensitivity of holographic materials only to light in the visible region required that recording was at a different wavelength from replay. The effect of this wavelength shifting was to give an aberration on replay1''2''3. An emulsion was selected and assessed for its suitability for the replay requirement of the holographic optical element. The use of optical fibres to produce the recording beams led to a compact exposure geometry. The purpose of the experiment was to find out what order of fiber to fiber coupling efficiency could be obtained using an established holographic emulsion in a feasibility test. 2. Material Silver halide material for which techniques have been well established was chosen as the recording medium its easily controlled processing leading to good repeatability of results. Kodak 649-F film was readily available and because of its l7jim thickness which is large for silver halide emulsion it has an advantage in terms of the volume diffraction effect. However the high sensitivity of this film over virtually the whole of the visible region meant that recording and processing had to be carried out in

The propagation characteristics for both bound power and tunneling ray power is analysed for one practical fiber system having N number of splices. The analysis is carried out considering the quality of each splices in the transmission system. It is observed that clad power increases with the number of splices and it depends on the quality of splices and fiber parameters like numerical aperture and diameter of both transmitting and receiving fibers. Better agreement between experimental results • and theoretical analysis is obtained. It is observed experimentally that the clad power is increased by , 30% having two equal spaced splices of loss of 0.2 dB each in a fiber of distance )4.5 Km between transmitter and receiver when compared with a system having no splice losses. Experimental lower values of splice losses for the fiber having more clad power are also verified with the theoretical analysis. Clad power is measured by clad probing technique.

Special type iodan" diffractive optical coiponents for fiber sodes selection are coaputer-aided designed and generated by digital holography iethods. Kodans are able to contain artificial standards for any given single iode or aultiaodal set. A basic iatheaatical discription is provided for iultichannelled iodans that are usable in fiber couplers, connectors and sultiplexers-deiultiplexers operating under angular iode division. Theoretical aethod of generative function is presented to ensure analytic suuing over aodes with different carrier spatial frequencies. Probles of discretization due to coaputer synthesis is investigated. Special perturbation aethod is provided to evaluate odan's energetic efficiency, selective capabilities and operating accuracy versus discretization step. Two-staged optical systei with generalised sodal spatial frequency plane essential for iode filtering is discussed. It is reported about developient and experisental investigation of gray-level phase iodans .atched to Gauss-Laguerre and Gauss-lleriite iodes.

A high bit rate fiber optic chip set was implemented using a 1 0 GHz 20 GHz max silicon bipolar process. This chip set provides system designers with easy to use cost effective integrated circuits for fiber optic systems at data rates up to 1. 5 Gb/s.

All-fiber polarization splitting was demonstrated using the stress release created by side polishing in stress-induced high birefringence fibers. This technique provides a very low loss (less than 0. 1 dB) and a broad wavelength range of operation (100 nm around 1500 nm). We report here about the detailled characteristics of the component and we present statistics about the 50 polarization splitting couplers that we have manufactured so far. We also describe typical applications of such a device.

The epoxy adhesives traditionally used to bond optical fibers into connectors complicate the connector assembly process due to their limitations in shelf life pot life ease of application and cure time. 3M has developed a new high performance hotmelt adhesive fiber bonding system which overcomes the limitations of the epoxies while providing additional benefits in ease of use and reduced installed cost.