Abstract: A fiber optic probe system includes a fiber optic probe and a carrier cable coupled to the probe. The carrier cable includes an excitation fiber for receiving excitation light and supplying a portion of the excitation light to the fiber optic probe, a return fiber for receiving detected light from the probe, and a directional coupler coupling the excitation fiber with the return fiber. The directional coupler is situated near an end of the carrier cable which is closest to the probe. A plurality of these fiber optic probes can be multiplexed using a plurality of carrier cables, each cable having a respective excitation fiber for receiving excitation light and supplying the excitation light to a respective one of the plurality of fiber optic probes.

Abstract: An integrated optical proximity coupler comprises first and second parallel straight interaction waveguide segments. First and second end segments are connected to the input ends of the first and second straight waveguide segments, respectively, by means including first and second curved segments, respectively. The end segments are both the same predetermined size which is determined by conventional optical fibers to which they are to be connected. To make the device broad banded, one of the straight segments must be narrower than the other. To reduce device excess loss, the first straight segment and at least part of its respective curved segment are made slightly narrower than the end segments, and the second straight segment and at least part of its respective curved segment are made slightly wider than the end segments. Thus, the required .DELTA..beta. can be obtained without making the narrow path too narrow.

Abstract: The polarization dependence of optical wavelength filters is eliminated by using waveguide directional couplers. Material birefringence is used to compensate for the waveguide (electromagnetic) birefringence which is the original cause of the polarization dependence. Material birefringence is introduced in a controllable fashion by replacing bulk waveguide layers by finely layered composites, such as multiple quantum wells using III-V semiconductor materials. The filter has use in wavelength-division-multiplexed fiber optic communication systems. This filter has broad application for wavelength-tunable receivers in fiber optic communication links, which may be used for telecommunications, optical computer interconnect links, or fiber optic sensor systems. Since multiple-wavelength systems are increasingly being used for all of these applications, the filter is useable whenever a rapidly tunable, wavelength-filtering receiver is required.

Abstract: A polarization independent tunable filter/receiver for optical communications. The tunable filter, operating as a directional coupler, has three waveguides including a central, feedguide and a pair of branch waveguides. Through either electro-optic effects or free carrier injection, the TM and TE polarization modes of the central wavelength can be coupled from the feedguide to the appropriate branch guide. The separated modes can be either detected independently or reunited in phase for further processing.

Abstract: Integrated optical devices which utilize a magnetostrictively, electrostrictively or photostrictively induced stress to alter the optical properties of one or more waveguides in the device are disclosed. The integrated optical devices consist of at least one pair of optical waveguides preferably fabricated in a cladding material formed on a substrate. A stress applying material, which may be a magnetostrictive, electrostrictive or photostrictive material, is affixed to the upper surface of the cladding material near at least one of the optical waveguides. When the appropriate magnetic, electric or photonic field is applied to the stress applying material, a dimensional change tends to be induced in the stress applying material. The constrained state of the stress applying material, however, caused by its adhesion to the cladding material, causes regions of tensile and compressive stress, as well as any associated strains, to be created in the integrated optical device.

Abstract: A polarization-independent electro-optically switched directional coupler utilizing reverse differential propagation constant control comprises an electro-optic material having at least a pair of wave guide channels within an interaction region and at least a pair of electrodes for selectively producing an electric field across the wave guide channels which electro-optically alters an optical propagation constant of the wave guide channels so as to vary the effects of an optical coupling between the wave guide channels.

Abstract: A channel dropping filter includes three frequency routing devices, one which functions as an input device and two which function as output devices. The first frequency routing device has one input for receiving the input signal and at least N outputs, where N corresponds to the number of frequencies that compose the input signal. The N outputs of the first frequency routing device are each coupled to an optical switch. Each optical switch has a first output coupled in consecutive order to one of the N inputs of the first output frequency routing device and a second output coupled in consecutive order to one of the N inputs of the second output frequency routing device. A controller is employed to selectively switch the optical switches between first and second states for directing each optical frequency component demultiplexed by the first frequency routing device to the first and second output frequency routing device, respectively.

Abstract: A wavelength conversion element includes a substrate made of LiTaO.sub.3 of non-linear medium, a three-dimensional waveguide formed in the substrate and a second harmonic generation portion for defining a change in refractive index in the waveguide with a period .LAMBDA. and generating a second harmonic of a fundamental wave introduced into the wave guide, where .LAMBDA.=2 m.pi./{.beta.(2.omega.)-2.beta.(.omega.)}, m is a natural number, .omega. is a frequency of fundamental harmonic, .beta.(.omega.) is a propagation constant of the fundamental wave, and .beta.(2.omega.) is a propagation constant of second harmonic.

Abstract: In a waveguide-type optical device, two optical waveguides are formed in a substrate of LiNbO.sub.3 or LiTaO.sub.3. On the substrate and the two waveguides, a blocking layer is formed to block a diffusion of Li ions from the substrate. On the blocking layer, a buffer layer made from SiO.sub.2 is formed. Each of the electrodes, from which operation voltages are supplied, covers each coupling part of the two optical waveguides, respectively, via the blocking layer and the buffer layer.

Abstract: The present invention is directed at an all-fiber in line isolator. The basic isolator includes a monomode optical fiber, a multimode waveguide, a coil or other traditional means to generate a magnetic field, and a fiber block or other traditional means to couple the fiber to the waveguide. In one embodiment, the fiber has a core and a cladding, and maintains a circular state of light polarization. The fiber has a coupling region where the cladding is partially removed. The waveguide evanescently couples to the fiber along the coupling region. The waveguide has magneto-optical properties such that applying a magnetic field along it causes backward propagating light to transfer to the waveguide with minimal disturbance to forward propagating light. Other embodiments using birefringent optical fibers are disclosed as well.

Abstract: A method and apparatus for automatically providing for both multiplexing and independent external modulation of two or more wavelengths emitted by a multi-longitudinal mode laser. The present invention uses an integrated optics device chip to enable coupling of the dispersed wavelengths into separate electro-optic modulators which encode each of the carrier wavelengths with a different signal. Accordingly, the volume of data which can be transmitted over an optical fiber network is increased.

Abstract: A passband-flattened acousto-optic polarization converter (100) in which two acoustic waveguides (14, 20) are formed in a substrate and a separated by a small gap (18) such that the two acoustic waveguides act as a directional coupler in which acoustic power is transferred back and forth. An interdigitated transducer (12) launches a surface acoustic wave in the first acoustic waveguide, and an optical waveguide is formed in the middle of the second waveguide. A partial acoustic absorber (27) is formed over both acoustic waveguides at a crossover length at a distance from the transducer equal to the point at which the acoustic wave has transferred from the first to the second waveguides and back again. The partial absorber absorbs most of the acoustic amplitude with the attenuated acoustic amplitude being coupled back again to the second acoustic waveguide but at an opposite sign.

Abstract: A tunable optical filter device has a wavelength selective optical filter that includes a grating structure arranged in a waveguide structure. The grating structure is formed so that it comprises two controllable grating sections electrically isolated from each other and which have different grating periods.

Abstract: A three or more section reverse .DELTA..beta. directional coupler designed to operate at a number of coupling lengths (L/l) selected from a region of a corresponding switching diagram where the cross and bar state switching curves are approximately parallel to each other and to the vertical axis, the vertical axis defining numbers of coupling lengths, or from a region of corresponding process sensitivity plots for the cross and bar states where the cross and bar state voltage curves are both approximately of zero slope. A number of these directional couplers form an optical switching array and a number of arrays form a system or network for switching optical signals each of which are capable of operation with uniform cross and bar state voltages at low crosstalk levels.

Abstract: Down-sized optical directional coupler with high performance and reduction of power includes a LiTaO.sub.3 monocrystal substrate, at least two optical waveguides of a LiNbO.sub.3 monocrystalline thin film formed close to and parallel to each other, and means for changing a refractive index of the optical waveguide provided on at least one of the optical waveguides, thereby obtaining a matching of a lattice constant between the LiTaO.sub.3 monocrystal substrate and the LiNbO.sub.3 monocrystalline thin film.

Abstract: A bidirectional light transmission system comprises a transmitting station having a light source for intensity-modulating a transmission signal, a first light branching portion for branching intensity-modulated light of the light source in a predetermined ratio and a first light receiving portion, and a receiving station having a second light branching portion, a light phase-modulating portion, a light reflecting portion and a second light receiving portion.

Abstract: An integrated optical receiver/transmitter (transceiver) 8 has continuous wave (cw) light 16 that enters a Mach-Zehnder optical modulator 10 controlled by a modulator control circuit 12 that provides modulated light 30 along a waveguide 32 to an optical coupler 34 which couples a predetermined portion of the light 30 to a waveguide 44 as light 42 which then exits the transceiver from a port 46. Receive light 90 is accepted at the port 46 and travels along the waveguide 44 to the coupler 34 which couples a predetermined amount of the light 90 to a waveguide 70 as light 92 which is detected by a waveguide-integrated photodetector 72. The photodetector 72 provides a current signal on a line 74 to a receiver circuit 76 which provides a voltage signal indicative of the light 92. Alternatively, the coupler may be passive, thereby not requiring the coupler control circuit, or no coupler at all may be employed and two fibers used for communications with the transceiver 8.

Abstract: A semiconductor waveguide type all-optical switch of a simple structure which can switch at high speed with low switching energy. A waveguide is formed within a core layer made of a semiconductor for absorbing controlling light when an electric field is applied, and a pair of electrodes are formed for applying a voltage to a waveguide part where a refractive index change is to be caused. The controlling light together with controlled light is entered in the waveguide. When a voltage is applied, Franz-Keldysh effect causes the wavelength at the optical absorption spectrum edge in the refractive index change part to shift to the long wavelength side. If light of a wavelength satisfying a predetermined condition is used as the controlling light, the controlling light is absorbed only in the refractive index change part for changing the refractive index in the part, thus the controlled light is switched. Preferably, a p-i-n structure is adopted.

Abstract: A directional coupler type optical function element with a high extinction ratio, in which a junction of a 2-input/2-output directional coupler or 1-input/2-output directional coupler, formed of a semiconductor or dielectric, is formed by successively optically connecting, from the input side to the output side, a front-stage partial junction, front-stage partial junction with electrode, central partial junction, rear-stage partial junction with electrode, and rear-stage partial junction, each having a predetermined length. The connection state at the front-stage partial junction and an incidence-side lead section optically connected thereto and the connection state at the rear-stage partial junction and an emergence-side lead section optically connected thereto cancel each other, thereby equivalently providing a symmetrical connection state and preventing the extinction ratio for a cross mode from lowering.

Abstract: Optical duplexer for bidirectional optical information transmission. In the optical duplexer for bidirectional information transmission, a phase difference is produced between two optical waves reflected back to the duplexer on different optical paths for reducing a near-end crosstalk while avoiding the generation of a difference in path length between the two paths. Provided is a device for controlling the phase of an optical wave reflected back into the duplexer on one of the two paths or provided are two paths having a difference in optical wavelength produced by a difference in refractive index. In particular, it is beneficial to set or fix the phase difference between the optical waves reflected back into the duplexer on the two paths to .pi./2. The optical coupler is advantageously utilized in bidirectional information transmission.

Abstract: An integrated optical circuit for fiber-optics gyroscopes comprising two pairs of waveguide conduits each having a pair of input/output ports on each of end surfaces of a substrate opposed to each other and a pair of directional couplers each disposed between the two waveguide conduits forming each of the pairs of waveguide conduits. The pair of the directional couplers are connected to each other through a waveguide conduit in which a polarizer is disposed in its course, the other waveguide conduits connected to the directional couplers have metal coatings in their courses and non-reflective coatings on an end surface of the substrate. This integrated optical circuit is capable of preventing electromagnetic beams from being radiated into the substrate and suppressing re-entry of radiated electromagnetic beams into the waveguide conduits.

Abstract: Distortion in an optical transmission system is significantly reduced by the use of two modulatable optical sources with non-ideal transfer functions of electric signal to light. The output of the first modulator is sampled and then delayed using an optical delay line. The sampled signal is compared with the input signal to generate an electrical error signal. This error signal is then used to modulate the second optical source. The output of this second modulatable optical source is then combined with the delayed output from the first optical source in a four-port optical coupler in such a way that the departures from linearity (which form the error signal) are removed on both outputs of the coupler, giving two optical outputs which possess a linear transfer function of electric signal to light through the entire system. The first optical source is chosen to have high power and low noise. The second source is chosen to be low power, moderate noise.

Abstract: A 1-input/2-output or 2-input/2-output directional coupler type optical device comprising a junction including two optical waveguides arranged parallel to each other and each fitted with an electrode for controlling a propagation constant, the incidence end or ends of one or both of the optical waveguides being connected to curved or straight optical waveguides, thus forming an incidence-side lead section, and the respective emergence ends of the two optical waveguides being optically connected to curved or straight optical waveguides, thus forming an emergence-side lead section. An electrode for suppressing the mode coupling is mounted on each optical waveguide of the emergence- or incidence-side lead section. A high extinction ratio of 30 dB or more can be obtained in either of cross and through modes by activating a required one of the mode coupling suppressing electrodes while applying an electrical signal to each propagation constant control electrode.

Abstract: An integrated cascaded optical phase modulator for providing linearized complementary modulated light output signals consists of the successive cascade of a first phase modulator stage, first fixed optical coupler, second phase modulator stage, and second fixed optical coupler Rf modulating signals applied to each phase modulator stage are adjusted in amplitude, for compensating for errors in the coupling angles of the first and second optical couplers. The levels of DC bias voltages applied to each phase modulator stage are adjusted for compensating for asymmetric phase modulation.

Abstract: A waveguide-type optical matrix switch including as its switching element a Mach-Zehnder interferometer which includes two directional couplers and an optical phase shifter. The two directional couplers are arranged by placing two optical waveguides in close proximity at two positions on a substrate, and have an identical coupling ratio. The optical phase shifter is disposed over at least one of the two optical waveguides between the directional couplers. The two optical waveguides have an effective optical path length difference of half a wavelength of a light signal between the two directional couplers, and are intersected in the optical switch element. The waveguide-type optical matrix switch is little affected by fabrication errors in the coupling ratio of the directional couplers, and superior in the extinction ratio.

Abstract: A package configuration for the protection/packaging/encapsulation of optical fiber couplers is described. The packaging strategy exploits symmetry in geometrical design while using material with similar thermal expansion properties to minimize thermoelastic stresses in the final assembled parts. When glass fibers are fused together or spliced in a planar waveguides, a complementary, symmetrically shaped glass piece linked to the coupler device by a chemically-tethered and crosslinked polymeric matrix, provides a stress-free as-assembled package that further maintains minimal thermoelastic stresses during temperature cycling. The packaged assembly is thus exceptionally rugged, experiencing little loss and fluctuation of coupling characteristics in installation and use.

Abstract: The improved intensity modulator comprises a directional coupler with a single active coupling section with a fixed amount of coupling along with a single pair of electrodes for supplying a voltage-controlled mismatch in propagation constants. Two passively-biased coupling sections are connected in series with the active section, with the two passive sections combined being at least one coupling length long. The bias voltage of the two passive sections are independently varied to compensate for non-linearities by providing additional coupling. In an alternate embodiment, a voltage-controlled directional coupler is connected in series with a fixed Mach-Zehnder modulator and a fixed directional coupler, and linearity is obtained by varying the phase shift of the Mach-Zehnder modulator, the length of the fixed directional coupler, and the length and coupling coefficient of the active coupler.

Abstract: An optical switch with improved stability which has a flat waveguide including at least two optical waveguides which are made of a glass containing silica and arranged closely each other, at least a core part of each of the optical waveguides consisting of an amorphous material which is prepared by a sol-gel method and contains organic molecules doped and orientated in a direction of electrostatic field by the application of an electrostatic field, and means for changing an optical path through change of a refractive index of the core part by applying an external force to the core part, which means is provided near the core part.

Abstract: An optical switch with a waveguide used as a detector is disclosed. The switch can be used for circuit or packet switching. The waveguide is used to tap off a fraction of the input signal going into the switch. The waveguide then sends the tapped off signal to a local electronic control to decide if switching is necessary or not. This is determined by within the local electronic control associated with the switch. The switch is set or reset based on information in the electrical representation of the signal which reaches the local electronic control. The switch can be used with continuous input signals as well as data packet input signals. By spacing the timing of data in the header differently than in the data in the "data" portion of a signal, extremely high bandwidth available in pure optical communications can be maintained.

Abstract: Polarization independent switch or coupler including a directional coupler with extremely relaxed fabrication tolerances. The coupler includes a mono-crystalline wafer of electro-optic material with two closely adjacent light waveguides at an upper surface along with electrodes positioned adjacent the waveguides. The electrodes include a grounded, main electrode formed on one side of the waveguides and four smaller electrodes formed in a line on a side or sides of the waveguides opposite to the main electrode, each of the four smaller electrodes being supplied with a voltage. The electrodes and waveguides can be in a planar or stacked relationship to one another. When the voltages applied to the middle two electrodes have equal values and have like polarity (V.sub.c =V.sub.b) and the voltages applied to the outer electrodes have equal values and like polarity (V.sub.d =V.sub.a), the light travelling in one waveguide is barred from transferring to another waveguide.

Abstract: In electro-optic waveguide devices such as directional couplers and Mach-Zehnder interferometers having travelling-wave electrodes which overlie the waveguides, temperature sensitivity is reduced by arranging the ground plane electrode to overlie only part of the width of its associated waveguide portion. The invention has particular application to z-cut lithium niobate.

Abstract: A TE polarization absorption film is provided on an optical waveguide between an ouput end of the optical waveguide and a directional coupler composed of the optical waveguide and another optical waveguide. In accordance with the presence of the TE polarization absorption film, a difference of output light power between polarization components becomes minimized.

Abstract: An optical control device such as an optical switch includes two waveguides formed in an electrooptical substrate. Two control electrodes are preferably formed respectively above the two waveguides through a buffer layer. The optical control device is further provided with additional electrodes formed where there is no waveguide therebelow. The additional electrodes are connected with either of the two control electrodes, so that there generates an electric field not only in the direction vertical to the surface of the substrate but in the direction parallel to the surface thereof.

Abstract: An integrated optical directional coupler is formed of two strip waveguides integrated on a substrate. A strip waveguide section in a coupling section of the directional coupler is designed as a controllable strip waveguide. The strip waveguides outside of this section are passive strip waveguides. In order to guarantee a largely polarization-dependent function of this coupler and of an optical switch realized therewith, the passive waveguides comprise a defined, different strip waveguide structure than the controllable strip waveguide.

Abstract: This e.g. Z-propagating, X-cut LiNbO.sub.3 :Ti splitter comprises an alternating delta beta directional coupler (39) able to introduce, in the absence of a voltage between its electrodes, a delta beta variation between its propagation constants, which is (a) independent of the polarization state of the guided lightwave and (b) such that the representative point of the coupler on its control diagram is the center of a segment parallel to the abscissa axis of the reference frame in which the diagram is plotted, and defined by two curves respectively corresponding to parallel states and crossed states of the coupler. Application to integrated optics.

Abstract: In an optical waveguide device, a plurality of optical directional coupler switches are provided on a substrate, and light input and output terminals are also provided to be coupled to the optical directional coupler switches. Each of the optical directional coupler switches is provided with a pair of parallel waveguides. One of the optical directional coupler switches operates independently of the polarization of light having a first predetermined wavelength by defining a width of the parallel waveguides and a distance therebetween to be first predetermined values, and one of the optical directional coupler switches operates independently of the polarization of light having a second predetermined wavelength by defining a width of the parallel waveguides and a distance therebetween to be second predetermined values.

Abstract: There is provided an optical functional device having a coupling portion in which two optical waveguides formed of semiconductor material are evanescent-coupled to each other and arranged in parallel and comprising voltage application electrodes electrically connected to each other and disposed on an upstream side portion of one of the two optical waveguides and a downstream side portion of the other optical waveguide and current injection electrodes electrically connected to each other, disposed on an downstream side portion of the former one of the two optical waveguides and an upstream side portion of the other optical waveguide and electrically isolated from the voltage application electrodes; wherein N-stage (N is an integer larger than 2) electrodes of reversal .DELTA..beta.

Abstract: This polarization beam splitter for guided light is e.g. produced on Z-propagating, X-cut LiNbO.sub.3 :Ti and comprises in series a passive Y-junction (66), an active phase shifter (68) and an active directional coupler (70), independent of the polarization and able to constitute a 3 dB coupler. Thus, on supplying a light wave to the input of the Y-branch and with the coupler constituting a 3 dB coupler, the TM and TE modes of the input wave are respectively obtained at the outputs of the coupler by appropriately polarizing the phase shifter. Application to optical fiber sensors or transducers and to the coherent transmission of information by monomode optical fibers.

Abstract: A waveguide type optical circuit element having a directional coupler for converting light intensity between two waveguides, which is used as a polarity-independent optical switch or a variable optical divider for optical fiber communications and the like. The two waveguides (2), (3) have a coupling section length which is in a TE mode about three times a complete coupling length of the TE mode, and in a TM mode about one time a complete coupling length of the TM mode. Electrodes (4), (5) comprise three-part electrodes of different lengths which act as reverse .DELTA..beta. electrodes for alternately reversing a direction of an electric field. This construction promotes the light-confinement effect of the waveguides, reduces the drive voltage necessary for carrying out an optical switching operation, and realizes optimal element characteristics in accordance with a ratio of variations in the propagation coefficient in the TE mode and TM mode of the directional coupler manufactured.

Abstract: In an optical micromechanical method for changing the phase of guided waves and a measurement method for measuring very small mechanical displacements and/or mechanical forces or pressures, including the pressure of sound waves and ultrasonic waves, and/or accelerations, the distance d between a section (1') of an optical waveguide (1) in an integrated optic or fibre optic circuit and a phase-shifting element (5) separated from said section (1') by a gap (4) is varied by forces (6) or by thermal expansion due to changes in temperature. The phase of the guided wave (3) is thereby modulated, and reciprocally the changes in distance d and hence small mechanical displacements and the forces (6) which produce them are determined from the measured phase changes.

Abstract: A transparent substrate is covered with a metal layer which serves as an etch mask for forming a groove, and from which regions are formed which constitute electrodes. At least the groove and the adjacent areas of the substrate are then covered with a layer of a material having electrooptical properties, the material in the groove forming an optical waveguide.

Abstract: An integrated semiconductor device including a directional optoelectronic coupler, which coupler comprises two parallel single-mode rectilinear optical waveguides over a total length D, separated by a small distance d, which coupler also comprises four electrodes of the same conductivity type, two on each waveguide, and at least one other electrode of the opposite conductivity type, characterized in that the coupler has an operation which is independent of the transverse electrical and transverse magnetic radiation components, TE and TM, respectively, present in random proportions in the incoming signal, under the condition in which the structural parameters of the coupler render it possible to ensure that the following relations are true: ##EQU1## In which relations: Z is the dimension of each electrode on the waveguides,.phi.TM and .phi.TE are the phase mismatches provoked by the refractive-index changes in the waveguides under the influence of an electric field,L.sub.CTE and L.sub.

Abstract: An optical control device comprises optical waveguides provided on a substrate having an electrooptic effect, a buffer layer provided on the substrate to cover the optical waveguides, and control electrodes provided on the buffer layer for applying a predetermined voltage across the optical waveguides. The optical waveguides has a coupling portion, at which an interval of the optical waveguides is narrowed. In this optical control device, a distortion dispersing structure is provided in the vicinity of the control electrodes to disperse distortion locally accumulated in the vicinity of the control electrodes to the whole area of the substrate uniformly.