Abstract: A monolithically integrated photonic circuit combining a semiconductor source of excitation light with an optically active waveguide formed on the substrate. The optically active waveguide is preferably formed of a spin-on glass to which are added optically active materials which can enable lasing action, optical amplification, optical loss, or frequency conversion in the waveguide, depending upon the added material.

Abstract: A laser has a resonant cavity defined by a pair of mirrors (6, 10) butted to respective ends of a 3 m fluorozirconate optical fibre (14). The fibre (14) has a .DELTA.n of 0.014 and a cut-off wavelength of around 790 nm and is doped to about 500 ppm (weight) with erbium ions. An optical pump source (12) provides a pump signal at 971 nm which excites the erbium ions into the .sup.4 S.sub.3/2 energy level to provide lasing at about 546 nm. The laser may alternatively be pumped by a pump signal in the band 791 nm to 812 nm, preferably 801 nm. The pump source is preferably a high power semiconductor laser (16).

Abstract: Plural planar optical devices are simultaneously pumped by a single pumping source. Various arrangements for accomplishing such pumping are disclosed. By utilizing these arrangements, the topology and routing of integrated arrays including optical devices are simplified.

Abstract: An optical network includes an erbium-doped silica-based optical fibre having a D-shaped cross-section. The wave-guide carries information signals at 1.53 .mu.m from a signal source and provides amplification to the information signals when pumped by an optical pump source operating at 0.994 .mu.m. Optical signals are tapped from the waveguide by means of evanescent couplers. The waveguide provides amplification to at least partially restore tapping loss to the information signal due to the optical taps. The core of the optical waveguide is chosen to substantially minimize the spot size of signals at the wavelength of the pump source so as to provide preferential extraction of the information signal in order to leave the pump source substantially undisturbed to be able to pump regions of the amplifying waveguide beyond the optical tap.

Abstract: A process and apparatus for the modulation and amplification of light beams having at least one input light beam (8) supplied to at least one Fabry-Perot resonator having at least one resonance mode, and defined by two mirrors (M1,M2) and produced by stacking layers on a substrate (4). At least one of the layers form an active medium (6) able to amplify the input light beam by stimulated emission, the wavelength thereof being around the resonance of the resonator and the density of free charge carriers in the active medium being varied in such a way as to make the latter sometimes absorbent and sometimes an amplifying with respect to the input beam and thus obtain at least one output light beam (10) whose intensity is modulated and amplified relative to the input beam. Application to optical telecommunications and to optical interconnections.

Abstract: A laser device utilizes a turbojet engine to provide a stimulation source. The turbojet engine is conventional, having a compression section, a fuel injection and igniting section, and an afterburner section. A pair of mirrors are mounted adjacent the hot gaseous stream produced by the turbojet engine. One of the mirrors is fully reflective and the other is partially reflective. The mirrors face each other and are perpendicular to the flow of the gaseous stream, creating a reflection path that is transverse to the flow. The high temperature creates excited molecules in the gaseous stream. This results in photons being emitted, which when striking other excited atoms which emit photons of the same wavelength, create additional photons to combine into a laser beam travelling along a reflection path between the mirrors. A portion of the laser beam passes through the partially reflecting mirror where it strikes an inclined mirror that aims the beam toward a desired target.

Abstract: By using a non-linear guided wave optical time domain reflectometry (OTDR) technique, specific features of an optoelectronic integrated device may be probed by detecting the reflections and back-scattering of a short light pulse along a waveguide interconnect. An integrated optical correlator in the form of a second harmonic generation (SHG) waveguide and a photodetector array detects and measures ultra-short pulses for optical ranging. Used with a standard CCD camera, the direct images of the autocorrelation of compressed Nd-Yag pulses (FWHM of 5 ps) have been monitored at video rates. Used with a cooled CCD camera for OTDR, reflections from samples have been observed with an interfeature resolution of about 0.15 mm in GaAs, limited by the FWHM of the laser pulses. Appropriate signal processing can increase the positioning resolution to better than 50 .mu.m. Additional applications are demonstrated, including the monitoring of fiber lengths (to within 30 .mu.m in real time) and temperature sensing.

Abstract: A laser has a resonant cavity defined by a pair of mirrors (6, 10) butted to respective ends of a 3 m fluorozirconate optical fibre (14). The fibre (14) has a .DELTA.n of 0.014 and a cut-off wavelength of around 790 nm and is doped to about 500 ppm (weight) with erbium ions. An optical pump source (12 ) provides a pump signal at 971 nm which excites the erbium ions into the .sup.4 S.sub.3/2 energy level to provide lasing at about 546 nm. The laser may alternatively be pumped by a pump signal in the band 791 nm to 812 nm, preferably 801 nm. The pump source is preferably a high power semiconductor laser (16).

Abstract: A coherent light power source comprising an oscillator and an amplifying optical fiber, both optically excited by the same pumping source, the beam of wave length L.sub.S output by the oscillator being amplified in the optical fiber.

Abstract: A fiber-optic amplifier for use with optical communications systems includes a light waveguide piece for amplifying an optical input signal. A pump light source is coupled to the amplifying light waveguide piece and includes a semiconductor laser for generating pump light for the amplifying light waveguide piece. A control device regulates the wavelength of the pump light generated by the semiconductor laser to be within a desired wavelength range so that the pump light is maximally absorbed in the amplifying light waveguide piece.

Abstract: A diode-pumped fiber amplifier has its amplifying fiber divided into two parts so that light from both ends of a laser diode can be used for pumping. A second diode may be included for redundancy, its outputs being coupled via a pair of polarisation beam splitter/combiners.

Abstract: Method and apparatus for generating a distortion-free, frequency-modulated optical signal, whereby this signal from an optical semiconductor laser driven with a modulating voltage is distorted by the modulating voltage due to a thermally conditioned frequency transfer function of the transmitter for the modulation frequency of the modulating voltage. For generating the distortion-free, frequency-modulated optical signal, the modulating voltage and/or the distorted, frequency-modulated optical signal itself and/or a superimposition signal containing this optical signal is subjected to a distortion that entirely or partially compensates the distortion of this optical signal. This method is simple and, in combination with receivers for the frequency-modulated optical signal, avoids sensitivity losses.

Abstract: An optical amplifier is provided through which an incoming optical signal passes before entering an optical-to-electric transducer. The level of the optical signal output by the optical amplifier is controlled by a controller based on the electrical signal output by the transducer.

Abstract: A method of producing a long output pulse (SA) from a short pump pulse (P), using an elongated amplified fiber (11) having a doped core (12) that provides an amplifying medium for light of one color when driven into an excited state by light of a shorter wavelength and a surrounding cladding 13. A seed beam (S) of the longer wavelength is injected into the core (12) at one end of the fiber (11) and a pump pulse (P) of the shorter wavelength is injected into the cladding (13) at the other end of the fiber (11). The counter-propagating seed beam (S) and pump pulse (P) will produce an amplified output pulse (SA) having a time duration equal to twice the transit time of the pump pulse (P) through the fiber (11) plus the length of the pump pulse (P).

Abstract: A sub-nanosecond pulse operated semiconductor laser amplifier which admits light input for a time interval after the commencement of the electrical pulse. The duration of the said time interval is shorter than that of the said electrical pulse. Amplified light output reaches a peak value after the termination of the said electrical pulse. The pulsed operation can be repeated a few billion times per second. Applications in a fiber-optics communication system, a bar code scanner, and in a super speed camera are described.

Abstract: Novel optical fiber devices (amplifiers and lasers) are disclosed. The devices comprise one or more optical "cavities", depending on the type of device. The cavities typically are formed by means of in-line refractive index gratings in a length of silica-based optical fiber. The gratings typically have peak reflectivity of at least 98%. Use of such cavities enables CW pumping of the devices, making the devices suitable for use in optical fiber communication systems. In an exemplary embodiment the device is a Raman amplifier for 1.3 .mu.m signal radiation, and in another exemplary embodiment the device is a Raman laser having an output suitable for pumping an Er-doped fiber amplifier. An exemplary pump radiation source is a laser diode-pumped CW Nd:YAG laser.

Abstract: The IR baffles placed between the window and the electrode of a longitudinal discharge laser improve laser performance by intercepting off-axis IR radiation from the laser and in doing so reduce window heating and subsequent optical distortion of the laser beam.

Abstract: A semiconductor optical amplifier with a high speed photodetector acting as an optical tap is disclosed. The device functions simultaneously as an in-line optical amplifier and as a high-speed photodetector tap. An in-line an optical amplifier is combined with a waveguiding, high speed (low capacitance) reverse-biased photodetector that absorbs only a percentage of the amplified signal, allowing the remainder to pass through without distortion.

Abstract: In an optical fiber amplifier circuit comprising first through m-th excitation light sources generating first through m-th excitation lights, first through m-th driving circuits drive the first through the m-th excitation light sources, respectively. Each of first through m-th transducers are coupled to each of the first through the m-th excitation light sources and transduces a part of each of the first through the m-th excitation lights to first through m-th electrical signals. In response to the first through the m-th electrical signals, a control circuit supplies first through m-th control signals to the first through the m-th driving circuits to control the first through the m-th excitation light sources so that the first through the m-th excitation light sources generate the first through the m-th excitation lights having first through m-th output power ratios 1/A.sub.1 to 1/A.sub.m.

Abstract: Prior art fiber-optic amplifiers which are used in a fiber-optic link to amplify the light signals to be transmitted have the disadvantage that the semiconductor lasers employed as pump lasers are highly sensitive to feedback, so that the stability of the light-signal transmission is impaired by pump light reflected back into the pump lasers.According to the invention, the operating current for such pump lasers (4) contains a noise current, so that the pump laser emits its pump light in many modes, which makes it insensitive to feedback.To prevent the noise component of the pump light which is caused by the noise current from affecting the amplification of the light signals to be transmitted, the noise current is filtered in such a way that its spectral components have frequencies which lie above the reciprocal lifetime of that energy level of the active laser medium which causes the amplification of the light signals.

Abstract: A fiber optic amplifier is disclosed utilizing a doped fiber to provide amplification through stimulated emission. The doped fiber is simultaneously pumped by multiple pump lasers generating optical waves of differing wavelengths. The optical waves from the lasers are combined using a wavelength division multiplexer before introduction into the doped fiber. The use of multiple pump lasers decreases the power requirements of each laser, reduces the cost of the amplifier, and increases reliability without compromising the gain of the amplifier.

Abstract: An optical amplifier using either rare-earth doped optical fiber, which can amplify an optical signal when a pumping light is injected, or a laser diode amplifier, which can amplify an optical signal by injection of an electric current. The amplifiers being of simple construction and having a gain which can be maintained constant through feedback control based on the detection of spontaneous emission from the sides of either the rare-earth doped optical fiber or the laser diode. The control being performed without the need for detection of input or output optical signal of the optical amplifier.

Abstract: For a group of optical amplifiers, pump beams from an array of lasers are mixed together to form a plurality of composite pump beams. Each composite pump beam is distributed to the pump port of a particular optical amplifier. The composite pump beam improves the reliability of each optical amplifier. Rather than having catastrophic failure of an optical amplifier occasioned by the failure of its pump laser, it is now possible to maintain full operation of the group of optical amplifiers even though one or more lasers fail.

Abstract: An optical amplifying apparatus is disclosed which includes an optical amplifier for amplifying a signal light, a narrow-band optical filter for removing a spontaneous light emitted from the signal light, two photodetectors for detecting, transmitting and reflecting lights of the narrow-band optical filter, and a controller for controlling a gain of the optical amplifier by comparing intensities of the transmitting and reflecting lights in accordance with the detected signals supplied from the photodetectors.

Abstract: An optical amplifier with a semiconductor body comprising a layer structure grown on a substrate 1 with an active layer 4 situated between two cladding layers (2, 3) with a strip-shaped amplification region bounded by two end surfaces (7, 8) which form the input and output surfaces of the radiation to be amplified. The active layer comprises a number of quantum well (QW) layers 4A with direct band transition, which are separated by barrier layers 4B of a different semiconductor material. The material, the number, and the thickness of the QW layers 4A and the barrier layers 4B in combination with the length 1 of the amplification region are chosen in such a way that two optical transitions can take place in the active layer 4, maximum amplification occurring at a certain current density through the PN junction for the radiation wavelengths corresponding to these optical transitions, while the end surfaces (7, 8) are provided with an anti-reflection layer 9 which has a reflection coefficient R of at most 0.

Abstract: An optical parametric oscillator/laser system includes an optical pump source for generating pump radiation and an embedded dual optical resonator containing an optical parametric oscillator/laser crystal. The embedded dual optical resonator includes a laser resonator and an optical parametric oscillator resonator. The OPOL crystal is an optical parametric oscillator material doped with ions that exhibit lasing transitions. The pump radiation stimulates generation of laser radiation. When the laser radiation reaches the parametric threshold, optical parametric radiation is generated. In one embodiment, the laser resonator and the OPOL resonator are each defined by spaced-apart mirrors. In another embodiment, the OPOL system includes an OPOL rod having end caps at each end. Each end cap includes surfaces for internally reflecting the laser radiation and the parametric optical radiation in a closed loop path so that the OPOL rod and the end caps define an optical resonator.

Abstract: A fiber optic isolator uses only one-half the amount of costly rotator material as the prior art and an isolated laser amplifier uses only one-quarter the amount of costly rotator material. An embodiment of a fiber optic isolator includes a concave reflector and a fiber holder defining first and second fiber ports that register the respective ends of first and second fibers. A polarizer is located between the first port and the reflector, an analyzer is located between the second port and the reflector, and a Faraday rotator is disposed between the polarizer and analyzer on one side and the reflector on the other side. The polarizer and analyzer have their polarization axes at a relative angle of 45.degree. while the rotator is configured to provide a 22.5.degree. rotation.

Abstract: An optical amplifier in the 1.26 .mu.m to 1.34 .mu.m spectrum range, comprising a solid substrate of fluoride glass doped with praseodymium in which a three-dimensional monomode waveguide is formed having an index difference .DELTA.n relative to the index of the fluoride glass lying in the range 4.times.10.sup.-3 and 8.times.10.sup.-2, said waveguide being associated by coupling means to an optical pump having a wavelength equal to 1.02 .mu.m .+-.0.1 .mu.m.

Abstract: A hybrid pumping scheme for rare-earth doped fiber amplifiers is disclosed. In particular, the arrangement utilizes at least two pump sources, operating at different wavelengths, coupled to a section of doped optical fiber, such as erbium-doped optical fiber. Optical multiplexers, such as fused fiber couplers, may be used to couple the message signal desired to be amplified, as well as the pump sources, to the doped fiber section. For certain embodiments, the doped fiber may be segmented into separate components, with the length of each component determined with respect to the wavelength of the associated pump signal.

Abstract: An optical amplifier, particularly useful for optical fiber telecommunication lines, which includes an active fiber doped with a fluorescent dopant which provides light energy emission at the wavelength of the transmission signals when the latter signals are applied thereto. One section of telecommunication line is connected to one input of a dichroic coupler, the output of which is connected to one end of the active fiber and the other input of which is connected to a source of pumping energy at a wavelength lower than that of the transmission signals. The other end of the active fiber is connected to another section of the telecommunication line. In rectilinear form, the active fiber provides single-mode propagation of the energy at the signal wavelength and multi-mode propagation of energy at the pumping energy wavelength.

Abstract: A laser amplifier chain has a plurality of laser amplifiers arranged in a chain to sequentially amplify a low-power signal beam to produce a significantly higher-power output beam. Overall efficiency of such a chain is improved if high-gain, low efficiency amplifiers are placed on the upstream side of the chain where only a very small fraction of the total pumped power is received by the chain and low-gain, high-efficiency amplifiers are placed on the downstream side where a majority of pumping energy is received by the chain.

Abstract: An optical assembly is disclosed herein along with a method of operation for use in a dye lasing arrangement, for example a dye laser oscillator or a dye amplifier, in which a continuous stream of dye is caused to flow through a given zone in a cooperating dye chamber while the zone is being illuminated by light from a pumping beam which is directed into the given zone. This in turn causes the dye therein to lase and thereby produce a new dye beam in the case of a dye laser oscillator or amplify a dye beam in the case of a dye amplifier. The optical assembly so disclosed is designed to alter the pump beam such that the beam enters the dye chamber with a different cross-sectional configuration, preferably one having a more uniform intensity profile, than its initially produced cross-sectional configuration.

Abstract: A laser amplifier operable such that at the commencement of each output pulse the carrier level has recovered from depletion by the previous pulse. Under these conditions output power commensurate with a much higher carrier density than is usually available is possible. The mode of operation is especially useful as a way of providing high power pulses, for example for use in optical time domain reflectometry. Using a travelling wave amplifier in conjunction with return to zero format data pulses is also disclosed.

Abstract: An optical fiber amplifier is disclosed wherein pumping light and signal light are introduced into an optical fiber doped with a rare-earth element to directly amplify the signal light. The optical fiber amplifier of the invention comprises means constituted from a reflecting film, a fiber loop or the like for causing pumping light to pass by a plurality of times in the doped fiber. Due to the provision of the reflective film or the fiber loop, pumping light can be utilized efficiently, and the amplification factor of the optical fiber amplifier is improved.

Abstract: Conventional optical amplifiers for the amplification of optical signals propagating in an optical waveguide use a first light source for the production of pump light, by means of which an active laser substance is excited to a first energy level above its upper laser level. According to the invention, a second light source is used to excite the active laser substance to a second energy level that is above the first energy level. By doing so, spontaneous emission between the laser levels of the active laser substance is suppressed in favor of induced emission.

Abstract: An optical amplifier having a saturable absorption region is operated below the lasing threshold for the device. Non-linear effects and bistability are observable at temperatures above room temperature. A selected input wavelength .lambda..sub.i within the gain spectrum of the device is amplified and an output at the same wavelength .lambda..sub.i is produced. This is in contrast to the normal operation at threshold, where there is a wavelength shift to the lasing wavelength and, depending on the laser used for the naturable absorption device, the output may be multimode for a monomode input. Best gain is achieved by tuning the input wavelength to a peak of a Fabry-Perot mode in the gain spectrum for the amplifier.The amplifier may be used as wavelength controlled optical switch, when operated bistably, or as a regenerative amplifier when operated in the non-linear region without hysteresis effects.

Abstract: An optical fiber telecommunication line composed of a number of series connected optical cables arranged end-to-end includes an active core optical fiber amplifier for the transmitted signals between each adjacent pair of optical cables. Two pumping optical radiation sources are connected to each active core optical fiber within each of the amplifiers, one source for each end of a single active core optical fiber. One of these two sources is placed into service and the second one is kept in reserve to be placed into service if the first one fails. A microprocessing circuit causes the sources to send distinctive recognizable alarm signals indicative of the state of an associated amplifier to terminal stations at the ends of the line and to receive therefrom control signals to control and exchange the functions between the two sources as necessary.

Abstract: A side pumped, fiber optic amplifier comprises an optical fiber, having a first refractive index, formed of a laser material, such as Nd:YAG. A jacket, which surrounds the optical fiber, has a second refractive index, lower than the first refractive index. This jacket is cone shaped and tapers from a large end to a small end. High power laser diodes are mounted on the large end to introduce pump light to pump the optical fiber material. The cone-shaped jacket focuses this pump light to an interaction region at the small end, where the jacket material is quite thin, e.g. on the same order of magnitude as the diameter of the optical fiber. The focused light is absorbed by the optical fiber in this interaction region, and causes an electronic population inversion in the laser fiber material. A signal propagating through the optical fiber stimulates spontaneous emission from the optically excited laser material, thereby resulting in amplification of the signal.