Abstract: A directional coupler of the present invention includes a substrate; a first waveguide layer; a second waveguide layer disposed over the first waveguide layer; a separation layer which separates the first waveguide layer and the second waveguide layer at least at one end; and an optical coupling section which is a predetermined region in which the first waveguide layer and the second waveguide layer approach or come in contact with each other. Each of the first waveguide layer and the second waveguide layer is integrally and continuously formed.

Abstract: An integrated optical switch that has a low throughput loss during the “on” pulse, and a high throughput loss during the “off” period. The optical switch includes a substrate with at least two waveguide structures suitably formed on the substrate. One of the waveguide structures is substantially straight and connects an input port to an output port. During an “on” pulse, light may be guided along the substantially straight waveguide from the input port to the output port such that there is little throughput loss. During an “off” period, a voltage is applied across control electrodes such that the waveguides are coupled so that light does not reach the output port.

Abstract: Three Mach-Zehnder interferometers 141 to 143 are connected in a series between an optical input terminal and an optical output terminal in an optical filter. Each interferometer is composed of two optical paths optical coupled at both ends by optical couplers. Only one interferometer has same optical path lengths between optical couplers. Heaters are disposed on each optical paths to allow the slope of transmission loss to change through the adjustment of the phase shift between those respective optical paths.

Abstract: A bi-directional optical coupler is provided. The bi-directional optical coupler includes a package having a first side and a second side. A forward coupler and a reverse coupler are included in the package. The forward coupler receives DC electric signals at the first side of the package and transmits DC electric signals at the second side of the package. The reverse coupler receives DC electric signals at the second side of the package and transmits DC electric signals at the first side of the package. The inclusion of two couplers within a single package means that the two couplers are subject to the same temperatures and have similar degradation. For this reason, the two couplers remain matched in terms of efficiency.

Abstract: A unique waveguide structure is provided in which the waveguide contains individual scattering elements that are capable of being tuned to provide local refractive index variations, e.g., on a micron scale—which is on the order of wavelengths typically used for communication system. According to the invention, the waveguide contains a core region, a cladding region, and a solid or liquid material having the tunable scattering elements dispersed therein, where the material is disposed within the core and/or cladding regions, and/or on the exterior of the cladding region. Useful scattering elements include, for example, liquid crystals dispersed in a polymer (polymer-dispersed liquid crystals—PDLC) or electrophoretic particles dispersed in a liquid medium.

Abstract: Optical signal delay apparatus and method may delay the progress of an optical signal through a semiconductor structure for a predetermined period of time. An optical delay device comprising a directional coupler and an optical signal loop may be used to delay optical signals. If desired, at least part of a directional coupler in an optical delay device may be formed from electro-optical materials so that the optical signals may be selectively transferred from the directional coupler to an optical Signal loop. Selective transfer may be provided through the application of a voltage. Optical signals with differing wavelengths may be differentiated by using a plurality of optical delay devices that each delay an optical signal having a different wavelength.

Abstract: A wavelength tunable optolelectronic device. Two channel waveguides are provided in an optoelectronic structure made of a ferroelectric material. The waveguides are adjacent along at least a coupling region. A periodically poled structure is provided in the coupling region, and at least one of the waveguides is untouched by this structure. An electric field is applied in the coupling region, through both waveguides, to enable coupling a light of a given wavelength between the two waveguides. The amplitude of the electric field may be selected to tune the coupling wavelength. A third waveguide or more having a coupling region in common with the second waveguide may also be added to allow the bandwidth of the resulting beam to also be tuned.

Abstract: The wavelength router comprises two flat waveguides, and these flat waveguides are connected by connecting waveguides. In each flat waveguide, optical path converters are created at connecting sections with the connecting waveguides. The optical path converters convert the light propagation direction in the flat waveguide to the light propagation direction in the connecting waveguides, or perform inverted conversion of this conversion. By this configuration, a compact element with a high wavelength resolution can be implemented.

Abstract: A device for switching an optical beam in an optical switch. In one embodiment, the disclosed optical switch includes an optical switching device disposed in a well region in a semiconductor substrate layer. In one embodiment, the well region has a higher doping concentration than the semiconductor substrate layer in which the well region is disposed. The optical switching device is optically coupled to an optical input port and an optical output port of the integrated circuit die.

Abstract: An optical wavelength tunable filter includes an optical waveguide having a first branched optical waveguide and a second branched optical waveguide merging into one piece of the optical waveguide through which optical wavelength multiplexed signals, each having a different wavelength component being incident from an end face of the first branched optical waveguide, are propagated. A comb-type electrode (or a plurality of comb-type electrodes each corresponding to each of the different wavelength-components) is mounted vertically to apropagating direction of the optical wavelength multiplexed signals leaving a specified space apart from the optical waveguide formed by a merger of the branched first branched optical waveguide with the second branched optical waveguide. A voltage applying device applies a predetermined voltage to each of the comb-type electrodes.

Abstract: An optical waveguide device wherein a substrate is fabricated from a lithium niobate (LiNbO3) substrate; at least one optical waveguide is formed in the lithium niobate substrate in such a manner that two Mach-Zehnder type directional couplers are formed, and further a phase shifter is formed in between these directional couplers; and the phase shifter is provided with an electrode of a structure including a first thin film layer being an ITO thin film containing an oxide and a second thin film layer being a chromium thin film an oxide of which is acidic, whereby an electric field produced in response to a voltage applied to the electrode is given to the optical waveguide to function as a variable optical attenuator.

Abstract: Disclosed herein is a multi-layer chip directional coupler. The multi-layer chip directional coupler has a first ground pattern, a coupling signal line, a main signal line, a second ground pattern, and a plurality of ports. The first ground pattern is formed on the upper surface of a first dielectric layer. The coupling signal line is formed of a conduction pattern on the upper surface of a second dielectric layer. The main signal line is formed of a conduction pattern on the upper surface of a third dielectric layer formed over the second dielectric layer. The second ground pattern formed on the upper surface of a fourth dielectric layer formed over the third dielectric layer. A plurality of ports is formed on the side surfaces of the first to fourth dielectric layers.

Abstract: Two right and left optical waveguides are provided so as to pass through a first directional coupler, a phase shifter, and a second directional coupler and so that directional couplers are provided in the first directional coupler portion and the second directional coupler portion. A third electrode is provided between these optical waveguides. A first electrode is provided on the left side of the left optical waveguide, and a second electrode is provided on the right side of the right optical waveguide. These electrodes are extended into the first directional coupler. Upon the application of a bias voltage, the voltage is simultaneously applied to all the first to third electrodes. By virtue of this construction, a waveguide-type optical control device can be realized which, in a directional coupler-type Mach-Zehnder (MZ) construction, can improve the extinction ratio without the complication of the construction.

Abstract: The present invention provides an active semiconductor optical switch for a 1×N interconnect switch having an input light channel, a plurality of output light channels, and a steering section coupled between the input and output channels. The steering section selectively directs an input light signal from the input light channel to an M number of the plurality of output light channels, where M ranges from one to the total number of output light channels of the plurality. The steering section includes transversely-spaced first and second elongate electrical contacts and an elongate slab waveguide extending therebetween. The slab waveguide is formed from a material having an optical refractive index responsive to a first electrical current applied to the first electrical contact and a second electrical current applied to the second electrical contact.

Abstract: An optical modulator is provided that not only can realize a suitable initial operating point without using dc voltage for control, but that has little optical loss and can obtain an excellent extinction ratio. The optical modulator comprises: a substrate having an electro-optical effect, first and second branch optical waveguides formed in a first major surface of the substrate; an optical branching structure for splitting input optical signal and supplying the split signals to the branch optical waveguides; and a 3-dB directional coupler that couples the outputs of the first and second branch optical waveguides. The ratio of nonuniformity, which is represented by the difference in propagation constants of the two optical waveguides in 3-dB directional coupler, to the coupling coefficient of the 3-dB directional coupler is 1 to at least 5, preferably 1 to at least 15, and still more preferably, 1 to at least 20.

Abstract: For the trimming of an arrayed waveguide grating (1) of an integrated optical multi-beam interferometer which is comprised of a large number (N) of waveguides (i) at least one (j) of these waveguides (i) is treated over a region (Bj) along its optical path length (Lj) only by irradiation which changes its core refractive index (nj) A defined phase shift (&Dgr;&phgr;j) of the light signal guided in this waveguide (j) results thereby which leads to a long-lasting correction of the aberration of the interference pattern in the multi-beam interferometer.

Abstract: Tunable add-drop and cross connect devices include materials with negative refractive index dependence on temperature and temperature independent coincidence between modes of an athermal ring resonator and a set of specified frequencies, e.g. for DWDM telecommunications channels. The free spectral range may be adjusted to equal a rational fraction of the specified frequency interval. The operating frequency may be selected without substantially tuning the resonator modes by a thermo-optically tuned feedback element having a waveguide pair with differential thermal response. The operating frequency may be induced to hop digitally between the specified frequencies.

Abstract: A substrate 1 having a pyroelectric effect has an optical waveguide 2 formed in it, and the optical waveguide 2 is provided with a buffer layer 3, a low resistance film 4 and an electrode 6 on it. The resistance value of the low resistance film 4 is made as small as possible or is set at a value determined according to the capacitances of the buffer layer 3 and the optical waveguide 2. The width of a part where the low resistance film 4 is in contact with the substrate 1 and the thickness of the substrate 1 also are set at a specified value. Furthermore, the specific heat and the thermal capacity of a package for housing this light control device also are set at specified values.

Abstract: A directional coupler including a substrate having a length and containing a material that exhibits electrooptic properties, the substrate being divided into a plurality of reversed polarization domains along a direction of length. At least two optical waveguides are formed in the substrate in the direction of length thereof and substantially parallel to a main surface thereof. An electrode is disposed above a portion of each optical waveguide for modulating light waves propagating through the waveguides, respectively, the electrode being divided equally by at least a portion of a boundary surface between the plurality of reversed polarization domains.

Abstract: Optical switches based on the balanced bridge interferometer design require precisely made (or half a coupling length) directional couplers to achieve minimum crosstalk for the two switch outputs. Precision 3 dB-directional couplers require the waveguide dimensions and fabrication parameters of the evanescent region to be tightly controlled making a low crosstalk switch difficult to manufacture and expensive. A new type of balanced bridge interferometer type switch is disclosed where the input and output directional couplers are asymmetrically biased to induce a certain difference in the propagation constants between the two waveguide in the directional couplers. By using the asymmetrically biased directional couplers with a certain tuning a bias voltage for the directional couplers. Low crosstalk switches can be achieved for a very wide range of directional coupler strengths, relaxing the precise half-coupling length directional couplers required in conventional design.

Abstract: An electro-absorption modulator is rendered capable of withstanding increased optical input power by one of the following means: incorporating a heat sink into the electro-absorption modulator structure to conduct heat away from the optical waveguide; incorporating a resistive member into the upper electrode of the electro-absorption modulator, producing a voltage drop that reduces absorption near the optical input end of the waveguide; making the bandgap energy of the absorbing layer of the waveguide higher at the optical input end than at the optical output end; and placing the electrode pad of the upper electrode near the optical input end.

Abstract: A waveguide element is capable of realizing acute waveguide discontinuity, such as a right angle bending, (L-shaped bending) or branching (T-shaped branching). Two single mode waveguides having the identical cross-sectional structure form a waveguide discontinuity where center axes thereof extending in the longitudinal direction intersect with each other at an angle &thgr; (0<&thgr;<90°). A leaky wave propagation region in a form of a quadrilateral shape having a length of one edge of L is located in the vicinity of a point where the center axes extended in the longitudinal directions of respective incident side and side single mode waveguides, with an effective propagation wavelength of a dominant mode there of to be cos(&thgr;/2) times of an effective propagation wavelength &lgr;G. Thus, an energy of the wave launched from an incident end of the single mode waveguide can be efficiently taken out from a end of the single mode waveguide.

Abstract: There is provided an optical circuit including a plurality of optical wave guides each composed of electro-optic crystal such as LiNbO3, or LiTaO3 and each designed to have a domain orientation different from each other. In accordance with the present invention, a portion of an optical device is inverted with respect to a domain. For instance, in an optical wave guide having a domain-inverted portion, if electric fields having the same orientation are applied to a plurality of portions which are to vary an index of refraction thereof, indexes of refraction are caused to vary in opposite polarities. Hence, it is possible to lower a voltage at which an optical device operates. For instance, if the present invention is applied to a Mach-Zehnder type phase shifter, it would be possible to accomplish push-pull operation, only if an electric field having one orientation is applied thereto.

Abstract: An optical switch that is constructed on a substrate having first and second waveguides that intersect at a gap having a predetermined width. The first and second waveguides are positioned such that light traversing the first waveguide enters the second waveguide when the gap is filled with a liquid having a first index of refraction. The gap is part of a trench in the substrate having a first region that includes the gap and a second region adjacent to the first region. The second region has a width greater than the width of the first region. A liquid having the first index of refraction is disposed in the first region. The liquid generates a gas when heated to a predetermined temperature. A first heater is disposed in the first region for heating the liquid to the predetermined temperature thereby generating a gas bubble in the liquid at the gap. Light traversing the first waveguide is reflected by the gap when the gap is filled with a gas.

Abstract: An optical coupler and method is disclosed in which a polymer material is employed to optically couple a first and second waveguide in a transfer region. In the transfer region, the first and second waveguides are positioned in parallel separated by a specific distance. The polymer material has an index of refraction which varies with temperature. The optical switch device is controlled by adjusting the temperature of the polymer material to obtain a desired index of refraction, thereby resulting in the desired transfer of an optical wave from on waveguide core to another.

Abstract: An optical device which has: a first optical waveguide disposed on a substrate having a thermo-optical effect; a second optical waveguide that, at its one end, has part which is disposed close to and in parallel with part of the first optical waveguide by a predetermined length on the substrate, and that, at the parallel part, is evanescent-coupled with light propagating through the first optical waveguide; light reflector that is disposed opposed to the end faces, at the one end, of the first and second optical waveguides and that totally reflects light emitted from the end faces; and distribution ratio altering system that heats around the evanescent-coupled parallel part of the first and second optical waveguides to alter a distribution ratio of lights emitted from the other ends of the first and second optical waveguides to which incident light supplied to the first optical waveguide at the other end is distributed.

Abstract: An optical device includes a substrate formed of an electrooptic material, a waveguide formed in the substrate, an electrically conductive film formed over at least a portion of the waveguide and a source of DC voltage electrically connected to the film for thermally inducing a change in the optical refractive index of the substrate of the optical device.

Abstract: A multilayer structure (S,1-3) is surmounted by parallel primary lines (4-1, 4-2) which define, in the regions situated below them, waveguides operating according to a first propagation mode. At least one electro-optical control means (E-1) is placed at a selected location between each pair of primary lines and, under certain conditions, enables the local existence of a second propagation mode affecting the two regions together, so that the transfer of the first mode between the two guides which enclose it can be controlled by acting on the second mode. This makes it possible to produce an energy distributor based on a so-called “cascade” architecture.

Abstract: An optical switch having a straight waveguide core with a lateral waveguide core extending therefrom. A region of polymer material is disposed in the straight waveguide core to deflect optical waves from the first waveguide core into the lateral waveguide core depending on the relative indexes of refraction between the first waveguide core and the polymer material. The temperature of the polymer material is adjusted, thereby adjusting the index of refraction of the polymer material so as to cause the deflection in a switched state, and to allow light radiation to pass through the polymer material in an un-switched state.

Abstract: Cores of an optical waveguide forming a Y-branch structured thermo-optic switch are stacked in a direction perpendicular to a substrate, and a heater is disposed on a clad right above an area where the cores overlap, thereby utilizing a large temperature gradient by the heater in the direction perpendicular to the substrate. The resulting stacked thermo-optic switch is low in power consumption and signal loss and high in extinction ratio.

Abstract: An optical device, and a method of producing the device, are disclosed. The device comprises a substrate and an optical waveguide component affixed to the substrate with a glass frit fusion seal formed and locked within a recessed void in the substrate, the glass frit fusion seal being the fused product of a low melting glass frit. The recessed void in the substrate includes a region for receiving the optical waveguide component and an intersecting region that secures the placement of the glass frit fusion seal. The optical waveguide component is affixed to the substrate in order to control temperature varying optical properties of the component.

Abstract: An optical method and apparatus particularly useful as an intensity modulation system, in which two phase modulators are placed in the loop of a Sagnac interferometer. Selective placement of the modulators, and the amplitude of any modulation signal input to the modulators, varies the bandwidth and frequency response of the system. In a preferred embodiment, the ratio of the optical distances of the modulators from interferometric midpoint, and the ratio of modulation signal amplitudes, is about 3:1, which serves to broaden and flatten the frequency response of the system.

Abstract: A digital optical switch includes an input waveguide connected to a Y-shaped branching waveguide having two legs, each of the legs being connected to an output waveguide. Each output waveguide forms one waveguide of a directional coupler, the other waveguide of which has its output dissipated into the substrate. Electrodes are connected to voltage sources such that the switch is operative between two states. In the first state, transmission of optical energy is enhanced between the input waveguide and the first output waveguide and inhibited between the input waveguide and the second output waveguide. Coupling between the first output waveguide and the other waveguide of its respective directional coupler is inhibited and coupling between the second output waveguide and the other waveguide of its respective directional coupler is enhanced.

Abstract: An optical coupler including optical fibers having gaps between first coverings and second coverings corresponding thereto. Each cladding of the two optical fibers is formed into a proper shape, with a taper of a proper thickness. The two optical fibers are then joined together, forming a joined portion which engages an engaging groove in a pair of blocks and the pair of blocks are affixed together by welding. Thereafter, the second coverings are affixed to cutouts in a retainer member. Lastly, the retainer, fitted to the blocks, is affixed thereto. Such an optical coupler is highly practical, does not allow deterioration of light dividing properties caused by changes in the length of the cladding joined portion as a result of an external stress, and prevents breakage of the joined portion.

Abstract: The invention is a method and apparatus that provides for the control of optical signals in a polarization-independent manner using birefringence. The invention includes an optical coupler connected to a birefringence element by an optical path loop. The optical coupler and optical path loop could be a Sagnac interferometer. The birefringence element affects the phase velocity of optical signals based on a control signal, and it can introduce a relative phase shift between optical signals propagating around the loop. The optical signals can be routed based on this phase shift.

Abstract: An optical device, and a method of producing the device, are disclosed. The device comprises a substrate and an optical waveguide component affixed to the z, substrate with a glass frit fusion seal formed and locked within a recessed void in the substrate, the glass frit fusion seal being the fused product of a low melting glass frit. The recessed void in the substrate includes a region for receiving the optical waveguide component and an intersecting region that secures the placement of the glass frit fusion seal. The optical waveguide component is affixed to the substrate in order to control temperature varying optical properties of the component.

Abstract: An optical circuit device is manufactured by forming an organic film formed on a substrate, and giving this organic film non-linear optical properties. An optical circuit device is formed containing an organic film formed on a substrate, wherein said film is either selectively formed on a portion of the region on a substrate or said film being formed over the entire region on a substrate, and a portion of a region of that film is either selectively formed to a thickness differing from other regions or selectively having a different structure. This optical circuit device can be manufactured to have various constitutions, and allows the formation of a multilayer optical circuit.

Abstract: The invention concerns an integrated-optical junction splitter, in particular for applications in the wavelength range of visible light, which ensures a spatial and wideband combination of light in a wavelength spectrum .DELTA..lambda. greater than 75 nm (value given applies to short-wave visible light). In the case of a usable wavelength range comprising the entire spectrum of visible light, the junction splitter is a white light junction splitter. The junction splitter consists of at least three channel waveguides, at least one of which must be a single-mode integrated-optical wideband channel waveguide (SOWCW). Two channel waveguides each have a respective input and are combined into a common SOWCW at their outputs in a coupling point, which common SOWCW features a common light output at its end.This wideband junction splitter is used as a wavelength-selective or wavelength-independent switch or modulator, in interferometric and photometric devices, sensors, and microsystem-technical solutions.

Abstract: An acousto-optical waveguide device for the wavelength selection of an optical signal comprises two polarization conversion stages, one polarization selective input element, one polarization selective output element and two intermediate polarization selective elements located at the output of the first conversion stage and at the input of the second conversion stage, respectively; the intermediate polarization selective elements have two branches connected together and two branches not connected together located on opposite sides with respect to the branches connected together.

Abstract: A method and apparatus for automatically providing for both multiplexing and independent external modulation of two or more wavelengths emitted by one or more multi-longitudinal mode laser(s) or other light source. 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. The carrier wavelengths can be transmitted over single or multi-mode optical fibers.

Abstract: A method and apparatus for tapping and distributing light propagating through a polymer optical fiber (POF). Within the polymer optical fiber, one or more mirrors are constructed. At a point in the POF where an internal mirror is constructed, light traversing the POF is efficiently diverted out of the polymer optical fiber upon striking the mirror. The light so diverted passes through a dispersing region such that only diffuse light is emitted and may be put to an advantageous use. Alternatively, a controllable shutter is placed within the polymer optical fiber such that light traversing the POF is diverted out of the polymer optical fiber upon striking the mirror when the controllable shutter so permits. The controllable shutter is variable so that variable amounts of light may be selectively emitted from the POF.

Abstract: An acoustooptical wavelength device for wavelength selection includes one substrate of a birefringent and photoelastic material on which there is formed: first and second rotation stages of the polarization plane of an optical signal in a first wavelength interval, wherein each stage comprises at least one optical waveguide traveled over by the signal; at least one optical waveguide, connecting the two stages and carrying one single polarizer consisting of an evanescent-wave polarization coupler; and at least one optical waveguide carrying one polarizer being finally provided downstream of the second stage.

Abstract: The invention provides an optical coupling switch and flat panel display including an array of such optical coupling switches. The optical coupling switch includes a light storage plate adapted to set up conditions for total internal reflection such that light injected into the plate is internally reflected. A light tap is disposed proximal to a coupling surface of the light storage plate for coupling internally reflected light out of the light storage plate and into the light tap when the light tap is brought into contact with the light storage plate coupling surface. The light tap is capable of movement in a direction perpendicular to the light storage plate in response to an applied electrostatic force. The optical coupling switch includes a scattering mechanism, such as a scattering surface or scattering medium, for scattering light in the light tap into a viewing volume.

Abstract: An optical device, and a method of producing the device, are disclosed. The device comprises a substrate having a near-zero, or negative, coefficient of thermal expansion and an optical component affixed to the substrate with a fusion seal, the seal being the fused product of a low melting glass flit having a positive CTE and a mill addition of a glass-ceramic having an effective negative CTE.

Abstract: An optical switch includes a substrate, an optical waveguide, arm waveguides, S-shaped curved waveguides, and two pairs of control electrodes. The substrate has an electro-optic effect. The optical waveguide is formed on the substrate and on which light is incident. The arm waveguides are formed on the substrate and branched from the light-incident optical waveguide into a Y shape. The S-shaped curved waveguides are formed on the substrate and continuous to the arm waveguides to form S-shaped curves. The first pair of control electrodes are formed on the arm waveguides and S-shaped curved waveguides. The second pair of control electrodes are formed on the substrate to be close to the first pair of control electrodes at predetermined gaps thereto.

Abstract: A waveguide type optical switch comprises a substrate having an electro-optical effect, a directional coupling type switch portion including two optical waveguides formed on the substrate for effecting optical switching by optical coupling. The waveguide switch includes a branched interfering portion provided on at least one of the two optical waveguides of the directional coupling switch portion, for controlling an intensity of light output from the directional coupling switch portion to obviate polarization dependency.

Abstract: A method and apparatus for tapping and distributing light propagating through a polymer optical fiber (POF). Within the polymer optical fiber, one or more mirrors are constructed. At a point in the POF where an internal mirror is constructed, light traversing the POF is efficiently diverted out of the polymer optical fiber upon striking the mirror. As such, the light which is diverted is effectively tapped off and may be put to an advantageous use.

Abstract: A semiconductor laser includes a semiconductor laser structure having an active layer. The laser structure is designed such that light in both of two polarization modes can be excited therein. First and second reflectors are provided, and at least one of them is a distributed reflector which determines first and second reflection wavelengths for the two polarization modes. A coupling unit is provided for coupling the laser structure and the first and second reflectors for either of the light of the two polarization modes at first and second coupling wavelengths, which respectively coincide with the first and second reflection wavelengths. One of the light of the two polarization modes at the first and second reflection wavelengths is selectively propagated along a cavity comprised of the laser structure and the first and second reflectors by a control unit. Thus, light oscillates in one of the two polarization modes at the first and second reflection wavelengths.

Abstract: The object is to reduce the size and losses of light transmitting/receiving modules. An optical transmitting/receiving module according to the invention comprises a light emitting element for sending out an optical signal of .lambda..sub.1 in wavelength, a first optical waveguide into which this transmit optical signal is entered, and a second optical waveguide for sending out the transmit optical signal and receiving an optical signal of .lambda..sub.2 in wavelength. Characteristically, it has a directional coupling section formed by arranging the first and second optical waveguides close to each other to be half as long as the full coupling length for a light having the wavelength of .lambda..sub.1, and at the end of the directional coupling section are arranged a filter for reflecting the transmit optical signal of .lambda..sub.1 in wavelength and transmitting the receive optical signal of .lambda..sub.

Abstract: A method and apparatus for automatically providing for both multiplexing and independent external modulation of two or more wavelengths emitted by one or more multi-longitudinal mode laser(s) or other light source. 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. The carrier wavelengths can be transmitted over single or multi-mode optical fibers.