Abstract: A laser apparatus capable of emitting a laser beam upon wavelength conversion and intensity modulation, which comprises a fundamental wave resonance means comprising a light emitting part, an optical resonator comprising mirrors sandwiching the light emitting part and capable of laser resonating, and a modulation-conversion means set inside said optical resonator, said light emitting part being a semiconductor light emitting element or a laser medium, said modulation-conversion means converting, by a nonlinear optical effect, a fundamental laser resonance wavelength light, and phase modulating said light by an electro-optical effect, and a modulation part of said modulation-conversion means comprising electrodes for application of a modulation voltage.

Abstract: A multichannel acousto-optic modulator (MCAOM) is described which uses a crystal with a plurality of mounting faces for acoustic transducers. The mounting faces are oriented so that the acoustic transducers mounted thereon generate acoustic fields which intersect the incident laser beam at a common angle, i.e., the Bragg angle. A two channel MCAOM uses two transducers. Extension to any higher number of channels follows accordingly. Energizing any of the transducers causes a corresponding first order beam to be diffracted out. Since the acoustic field for each transducer intersects the incident beam with a unique orientation, each first order beam is diffracted out on a unique axis. A system utilizing an MCAOM has electronic means for controlling the driving signals to the transducers to control each channel as required by the application. Amplitude and frequency modulation of the driving signals allows the intensity and angle of the beams to be controlled.

Abstract: An optical processor for controlling a phased antenna array uses a frequency-shifted feedback cavity (FSFC), which includes a traveling-wave cavity. The FSFC incrementally delays and incrementally frequency shifts optical signals circulating in the traveling-wave cavity. Optical signals coupled out of the FSFC are separated by frequency, hence by delay, and processed to control either or both transmit and receive beam-forming operations. The FSFC provides a receiver with multiple receive signals which have incremental values of frequency. Each frequency corresponds to an incremental time sampling of optical signals input into the FSFC. Transmit signals coupled out of the FSFC have frequency and phase relationships that result in short time-domain pulses when combined. Controlling modulation and frequency of the transmit signals achieves carrier interference multiple access, a new type of spread-spectrum communications.

Abstract: An electrical signal to be frequency-modulated is branched into first and second signals. An FM laser 102 oscillates light having a wavelength .lambda.1 in a steady state condition, and outputs an optical signal obtained by converting an amplitude change in the inputted first signal into an optical intensity change and an optical frequency change. An optical detecting portion 106, to which the optical signal from the FM laser 102 and light having a wavelength .lambda.0 outputted from a local light source 104 are inputted, converts an optical intensity modulation component of the inputted optical signal as a current amplitude change by operating square-law detection characteristics, and generates a beat signal at a frequency corresponding to a difference in wavelength .DELTA..lambda. between the two inputted optical signals. A discrimination portion 110 discriminates using a threshold value generated on the basis of the second signal and converts the beat signal into the pulse signal.

Abstract: A semi-monolithic ring cavity for a second harmonic generation of laser frequency including a nonlinear crystal, an input mirror, an output mirror, a first point, at which a fundamental wave is incident onto the input mirror, a second point, at which the fundamental wave is incident onto the output mirror along with a second harmonic wave, and a third point, at which the fundamental wave reflects totally from a side surface of the nonlinear crystal. One of the input and output mirrors is coated with a dielectric and separated from the nonlinear crystal whereas the other mirror is formed on the nonlinear crystal. The fundamental wave forms a ring cavity in such a manner that the second harmonic wave is generated only along an axis extending through the first and second points. The semi-monolithic ring cavity exhibits a stable frequency characteristic and a high transform efficiency when a second-harmonic generation of continuous-wave laser frequency is carried out.

Abstract: Laser modulation control apparatus and methods which provide direct control of the transmitted optical extinction ratio of a semiconductor laser. A relatively low frequency and low amplitude pilot tone is superimposed on the signal used to drive the laser. Setting the amplitude of the pilot tone to a fixed fraction of the laser modulation current causes the transmitted optical power to vary a fixed fraction of the optical data amplitude at the pilot tone frequency. By using feedback to control the laser modulation current, the amplitude of the variation can be maintained at a desired value, which in turn maintains the transmitted optical data amplitude at a constant value, regardless of variations due to operating temperature or laser aging. A separate control loop is employed to maintain the average optical power at a fixed value. Since the optical data amplitude and the average optical power remain constant, the optical extinction ratio is also constant. Alternate embodiments are disclosed.

Abstract: An integrated laser-based light source that generates an output light beam having a controlled intensity. The light source comprises a light sensor, a laser, a convex beam-splitting surface, and a package that includes a header. The light sensor generates an electrical signal representing an intensity of light energy falling on it, and is mounted on the header. The laser has one and only one light-emitting face from which a light beam is radiated as a radiated light beam. The laser is mounted in the package adjacent the light sensor with the light-emitting face substantially parallel to the light-receiving face of the light sensor. The convex beam-splitting surface reflects a fraction of the radiated light beam towards the light sensor as a reflected light beam, and transmits the remainder of the radiated light beam as the output light beam. The convex beam-splitting surface is supported in the radiated light beam by the package.

Abstract: A laser beam generating device which, by addition of a simplified structure, can enlarge the spectral width of the laser light and lower the coherence to a moderate value. The laser light generating device includes a first laser light source 31, a second laser light source 32, phase modulation units 34, 35 for phase-modulating the beams from the light sources with a sole frequency component or plural frequency components, and an sum frequency generating unit 33 for producing a light beam of the shorter wavelength based on the wavelength of the light phase-modulated by the phase modulation units 34, 35. The fundamental wavelength laser light generated by the first laser light source 31 is phase-modulated by the phase modulation unit 34 based on a pre-set modulation amplitude and the modulation frequency so as to be enlarged in spectral width before being incident on the sum frequency generating unit 33.

Abstract: A high power laser source having a preselected broad bandwidth, including a master oscillator providing a single-mode laser beam, a resonant electro-optical modulator and a source of radio-frequency (rf) modulation voltage, to produce a modulator output beam having sidebands spaced on each side of the nominal frequency of the single-mode laser beam. The bandwidth and the number of modes may be varied by controlling the voltage applied to the modulator. At least one additional modulator in series with the first provides for the addition of other sidebands overlaying those generated with just one modulator. In another embodiment of the invention, the modulator is installed in a PC MOPA (phase conjugated master oscillator power amplifier) configuration to provide modulation only on the return path of the beam from a phase conjugation device having a stimulated Brillouin scattering (SBS) medium.

Abstract: A compact wavelength monitoring and control assembly for a laser emission source is provided comprising a narrow bandpass, wavelength selective transmission filter element, of Fabry-Perot etalon structure, through which a non-collimated beam from the laser source is directed onto two closely spaced photodetectors. For wavelength stabilization, the differential output of the two photodetectors is used in a feedback loop to stabilize the wavelength of the laser source to a desired target wavelength. Through the angular dependence of the wavelength transmission of the Fabry-Perot etalon, a wavelength variation from the source is converted to a transmission loss, which is different for the two photodetectors, so that the wavelength change is detected as a differential power change. The device functions as an optical wavelength discriminator in which the detector converts optical energy to current for a feedback loop for controlling the light source.

Abstract: A device and method for measuring a difference frequency having a simple structure and utilizing optogalvanic effect for measuring a difference frequency when carbon dioxide laser light of a single wavelength is varied in frequency by a measuring object. When a part of frequency varied laser light is mixed with an original frequency of laser light by self-mixing in a laser resonator, a strength of the laser light in the resonator is modulated to a difference frequency between the original frequency and the variation frequency. Since a current change in response to strength of light is generated by the optogalvanic effect in the laser resonator, when a frequency of optogalvanic current change is measured, the difference frequency can be measured.

Abstract: Laser annealing is performed by irradiating, while scanning, a semiconductor thin-film with laser light. The laser light that is linear on the irradiation surface is moved in its line-width direction and applied non-continuously. The laser light has, in its line-width direction, an energy density profile that assumes a step-like form in which the energy density varies in a step-like manner. In particular, the scanning pitch D and the step widths L.sub.n are so set as to satisfy a relationship L.sub.n .gtoreq.D.

Abstract: An optical communications system for transmission of optical signals using relaxation oscillation subcarrier, on-off keying modulation of the optical signals. Relaxation oscillation subcarrier on-off keying improves the signal-to-noise ratio of a receiver receiving the modulated optical signals and the data rate of the optical signal. A modulation device generates relaxation oscillations by pulsing a driving current for a transmitter between a first level below a threshold current and a second level above the threshold current. The optical communication system can further include a fiber optic link between the transmitter and the receiver. The optical communications system can further incorporate multiple frequency shift keying. The modulation device and modulation scheme can be used in all digital optical communications systems using a pulsed laser diode.

Abstract: A rare-earth doped, lithium niobate, diffusion Bragg reflector laser having a simplified structure and improved efficiency is disclosed. The laser has a pump source, a wavelength division multiplexer, a substrate of lithium niobate doped with at least one rare earth element and having a feedback element, and a grating reflector. The grating reflector is formed from portions of an optical fibre and abuts one end of the doped substrate, such that the grating reflector and the feedback element of the doped substrate form a cavity for the laser. The doped substrate may include phase or amplitude modulators for FM or AM mode-locking operation.

Abstract: The modulation bandwidth of a long-cavity semiconductor laser and a multi-frequency long-cavity semiconductor laser is increased by electronic precompensation of the modulation input. The modulation bandwidth may be further increased by having the modulated amplifier and the desired output as far apart as possible.

Abstract: The emission waveband of a data modulated laser signal is locked to the reflection waveband of a chirped Bragg grating dispersion compensator by means of a phase locked loop regulating the temperature of the laser or the magnitude of the drive current applied to it.

Abstract: A harmonic generator laser system which features a distributed Bragg reflector (DBR) or distributed feedback (DFB) tunable diode laser coupled to a quasi-phasematched (QPM) waveguide of optically nonlinear material. Tuning of the DBR laser may be achieved either thermally or via current injection, or both, halving the wavelength of a red laser into the visible blue spectral band. Thermal tuning may provide a coarse tuning adjustment, while injected current may provide fine tuning accessible to a user. Separately or in combination with current tuning, a modulation signal may be applied to the DBR laser for achieving an intensity modulated or a pulsed output. In another embodiment, modulation may be achieved by frequency modulation of the laser. A very compact tunable blue laser is formed. In yet another embodiment a double clad fiber amplifier is disposed between the tunable laser and the waveguide.

Abstract: The invention discloses a method and an apparatus for optically transmitting a narrow-band optical signal beam having a sub-carrier frequency in the 20 to 300 GHz range. The apparatus has a semiconductor laser with a lasing cavity of length L. The length L preferably ranges from less than 1 mm to 10 mm, thereby defining the round-trip resonance frequency according to the following equation c/2 nL. The apparatus has a signal source for generating an electrical modulating signal having a modulation frequency contained in a narrow band containing the round-trip resonance frequency. An in-coupling means delivers the electrical modulating signal to the semiconductor laser which produces a sub-carrier modulated signal beam whose sub-carrier modulation frequency lies within a response band and corresponds to the modulation frequency. The apparatus further includes a biasing device for providing a biasing voltage for tuning the response band and the sub-carrier modulated signal beam.

Abstract: A drive circuit drives an electronic device that converts electric power into light or heat energy. The drive circuit has a switch connected to the electronic device in series, and a control circuit for providing, in response to an input control signal, a pulse modulation signal for controlling the switch. The frequency of the pulse modulation signal is higher than the response frequency of the electronic device. Alternatively, the drive circuit may have first to fourth switches disposed on both sides of the electronic device, for passing a current in different directions through the electronic device, and a control circuit for controlling the switches to change the direction and magnitude of the average of the current flowing through the electronic device in response to an input control signal.

Abstract: A multiple-frequency-modulation mode-locked laser device which generates high-speed optical pulse trains and can be used as a high-speed optical pulse source in the fields of optical communications and optical measurement is presented, wherein the repetition frequency F.sub.rep and the pulse width .DELTA.t are able to be controlled independently with only the laser itself.A drive signal generation means is provided which generates a frequency-mixed drive signal mixed from at least two different frequencies f.sub.1 (=N.sub.1 f.sub.r), f.sub.2 (=N.sub.2 f.sub.r), . . . , which are integral multiples of the frequency spacing f.sub.r (=c/R) of the longitudinal modes of either a ring cavity or a Fabry-Perot cavity. This frequency-mixed drive signal is supplied to an optical modulation means of the cavity.

Abstract: A semiconductor laser is provided which is capable of generating a train of ultrashort light pulses with an ultrahigh repetition frequency and which is useful in optical communications and optical information processing. The semiconductor laser is a mode-locked semiconductor laser which has two resonator cavities which are formed by two facets and a distributed feedback structure between these two facets. The length of the resonator cavity formed between one facet and the distributed feedback structure is 1/m (where m is an integer) of the length of the resonator cavity formed by the other facet and the distributed feedback structure. A saturable absorption region and a high-frequency modulation region are provided within the longer of the resonator cavities. By making the high-frequency modulation frequency be equal to the round trip frequency of the light within the longer resonator cavity, mode-locked operation is achieved.

Abstract: A digital controller for an injection laser diode. The controller maintains the laser diode average and peak power levels constant in spite of temperature and/or aging effects. A pseudo-random sequence is superimposed on the `0` and/or `1` current levels to the laser diode and the optical output is detected by a back facet monitor. The detected signal is compared with preset references and a feedback signal is used to control both the bias current and the modulation current.

Abstract: A GHz-range frequency-modulated laser based on manufacturable vertical cavity surface emitting lasers (VCSELs) and arrays. The present invention exploits a saturable absorber contained within the VCSELs distributed Bragg reflector which may itself be adjusted during fabrication or in operation. Under controllable operating conditions, the saturable absorber, strategically sized and placed, will force the VCSEL to self-pulsate (in the GHz-regime) at rates related to the local intensity, absorption, lifetime, and carrier density of the saturable absorber. These conditions can be controlled in real time in one of three ways; first, by adjusting the injection current into the VCSEL itself; second, for a fixed VCSEL bias and the use of a third terminal, by modifying the carrier density within the saturable absorber via additional current injection; or third, the saturable absorber can be reverse-biased by simultaneously altering its absorption and carrier lifetime and thus carrier density.

Abstract: In an optical modulator including a laser light source emitting laser light and a modulator, a modulation signal source for applying a modulation signal to the modulator, a signal processor for producing and outputting a signal in response to a change in the modulation signal, and a driving current source for generating a driving current applied to the laser light. Wavelength chirping modulation reverse to the wavelength chirping occurring in the modulator is produced in the light emitted from the laser by modulation of the driving current whereby wavelength chirping produced by the modulator is at least partially cancelled and wavelength chirping of the light output from the modulator is reduced.

Abstract: A system for recovering a clock from an optically encoded signal uses a mode-locked laser. A modulator is connected in common with the laser cavity of the laser and a transmission path applies the input optically encoded signal to the modulator. The modulator in response to the optically encoded signal modulates the phase and/or amplitude of light in the laser cavity thereby locking the phase and frequency of an output pulse stream to the timing wave of the optically encoded signal. In a preferred example, the modulator is a non-linear optical modulator used for cross-phase modulation (XPM) of the light in the laser cavity.

Abstract: A gas laser 1 such as a .sup.13 CO.sub.2 -laser emits at two different wavelengths (.lambda..sub.1, .lambda..sub.2) with a sine-shaped adjustment of a resonator mirror or a grating 13 such as a Littrow grating. The gas laser emits radiation at the two desired wavelengths (.lambda..sub.1, .lambda..sub.2) in two mutually adjacent intervals of the resonator length L because of a suitable dimensioning of the grating 13 with respect to grating structure and angle position, the outcoupling factor of the outcoupling mirror 12, the resonator length L and the composition of the gas of the laser. The laser emission is inhibited at the crossover between the two intervals and the sine-shaped modulation (for example with a piezo element) of the resonator length L is essentially symmetrical about this crossover. The invention is also directed to an arrangement for detecting a substance such as NH.sub.3 in a flue gas.

Abstract: A process for the transposition of a modulation of an adjustable wavelength. A semiconductor amplifier is relooped through a feedback loop including a filter set to a first wavelength. An incident beam set at a second wavelength which is amplitude modulated is injected into the semiconductor amplifier laser. The incident beam is either extinguished or allows self-oscillation to be established in the loop. Thus, the modulation is transposed from the second wavelength to the first wavelength.

Abstract: An improved high average power, high brightness laser system. The laser system comprises an XeCI excimer amplifier, an XeCI excimer preamplifier, a means for generating a picosecond seed pulse tailored for the XeCI preamplifier and the XeCI amplifier and a means for focusing the output pulse laser beam onto a spot smaller in area than 100.times.10.sup.-6 cm.sup.2. We first produce a seed laser beam consisting of a series of bunches of short duration pulses with a bunch frequency in excess of 100 pulses per second. These seed laser pulses are produced by a Nd:YAG pumped dye laser oscillator with a cavity dumper. The pulses in the beam are preamplified in a multipass preamplifier and the pulses are then multiplexed in a pulse train generator into a larger number of lower power pulses.

Abstract: An optical frequency translator includes a frequency routing device formed on a semiconductive wafer between two reflective facets forming a laser cavity. Waveguides associated with the device each contain an integrated optical amplifier selectively acting as a gate preventing the flow of optical energy through a respective waveguide or as a gain-providing element which amplifies optical energy flowing through a respective waveguide. When a selective one of the optical amplifiers is activated with bias current the optical energy produced by this current operates in conjunction with the optical energy of the input signal so that lasing action occurs between the reflective facets. The lasing action occurs along a predetermined path determined by the optical amplifier or amplifiers that are activated. The lasing action in this particular path is supported at a particular selected frequency. This particular frequency is the frequency to which the input signal is to be translated.

Abstract: A laser cavity configuration employs a mode reshaping structure in a solid state waveguide. The mode reshaping may be by means of an adiabatic taper. Polarization switching may be employed in connection with the mode reshaping to obtain a high output power in a single transverse spatial mode from an integrated external cavity multiple-mode diode laser device. The structure provides stabilization and rapid tuning of the frequency of the diode laser, as well as use substantially all of the available power of the diode laser operating multimode. Various configurations and combinations are described. An advantage is that an integrated structure can provide output of the laser in a waveguide with single mode for subsequent applications. The external cavity diode laser according to the invention is consistent with a planar manufacturing process such that high volume, low cost products can be achieved.

Abstract: A semiconductor laser (10) having an external cavity used for coherent frequency and time domain reflectometry is provided. The laser (10) provides a very stable single longitudinal mode characteristic, a very narrow lasing linewidth, and a very low noise optical output. The laser (10) includes a semiconductor optical amplifier (14) emitting a coherent light beam from one facet, a phase modulator (22) receiving the coherent light beam and linearly varying an optical frequency of the laser, and an etalon (32) selecting and stabilizing one longitudinal mode of the laser cavity for lasing, narrowing the linewidth and reducing the noise. A computer-controlled and piezoelectric actuated wavelength-selective grating (58) varies the length of the laser cavity and thereby tuning the optical frequency of the selected longitudinal mode to track the transmission frequency of the etalon by maintaining maximum power intensity thereby stabilizing the selected mode.

Abstract: A laser cavity configuration employs polarization switching to obtain a high output power in a single transverse spatial mode from an integrated external cavity diode laser device. The structure provides stabilization and rapid tuning of the frequency of the diode laser. An advantage is that an integrated structure provides output of the laser in a waveguide with the correct polarization for subsequent applications while supporting optimal polarization in a solid state active medium. The external cavity diode laser according to the invention is consistent with a planar manufacturing process such that high volume, low cost products can be achieved.

Abstract: An analogue telemetry system/method provides fault location in an optical transmission system including optical fibre amplifiers. Each amplifier includes an optical fibre amplifier with an AGC loop therearound, a respective optical pump source being included in the AGC loop. In the AGC loop the spontaneous emissions from the amplifier fibre is detected and employed to drive the pump source appropriately to maintain the amplifier output at a predetermined level. A supervisory tone is applied at the transmission end of the system. At each amplifier the presence of the supervisory tone or a distress tone from a previous amplifier is looked for. If either tone is detected the signal is amplified and transmitted to the next amplifier. If neither tone is detected a respective amplifier distress tone is applied to the respective optical pump source.

Abstract: A light modulator integrated light-emitting device is provided with a light-emitting element formed on a semiconductor substrate, a light modulation element formed on the semiconductor substrate and which is optically connected to the light-emitting element, a laser electrode formed on the light-emitting element, a light modulation electrode formed on the light modulation element, and a ground electrode that is formed between the laser electrode and the light modulation electrode in an electrically isolated state with respect to these electrodes and applied with constant voltage.

Abstract: An analogue telemetry system/method provides fault location in an optical transmission system including optical fibre amplifiers. Each amplifier has a respective optical pump source including an AGC loop around the optical amplifier's fibre. Spontaneous emission from the optical fibre amplifier is detected and employed to drive the respective pump source to maintain the amplifier output at a predetermined level. A supervisory tone is applied at the transmission end of the system and its presence/absence detected at each amplifier. In the event of "absence", a respective distress tone is applied at the relevant amplifier. At the receiver end of the system, the supervisory tone is sought and in the absence, the number of distress tones, if any present, is counted and the position of the fault is thus determined.

Abstract: A tunable laser capable of high speed operation is realized by modifying a tunable laser incorporating an N.times.N wavelength grating router to have an output waveguide positioned for capturing second order diffraction optical energy from the router free-space region. The second order diffraction-optical energy is supplied as the laser output at the desired wavelength to which the laser is tuned.

Abstract: In a light transmission device operable in response to a sequence of input digital signals to produce an output light beam, a modulated light beam is produced from a laser device as a result of frequency shift keying carried out under a designed modulation index and is transmitted as the output light beam on one hand and is sent to a Fabry-Perot interferometer on the other hand to produce an optical output beam which has an output level deviated in dependence upon a variation of a modulation index relative to the designed modulation index. A feedback signal is fed back to a drive circuit which is supplied with the input signals and which is operable to control the laser device. The feedback signal serves to adjust the modulation index of the laser device to the designed modulation index. A controller may be included to control a central frequency of the output light beam by producing a bias signal which is added to the feedback signal.

Abstract: Noise and distortion due to scattering and reflection in a fiber-optic communications system are suppressed by modulating the optical frequency of (chirping) a laser light source to broaden the spectrum of the laser light output. The broader spectrum spreads the noise produced by an unchirped source over a broader band. A noise and distortion suppression system includes a chirp signal generator coupled to the signal path of an RF input signal carrying information to modulate the laser optical output. In some cases, the frequency of the chirp generating signal may result in second-order intermodulation products falling within the information band. In such cases, the RF input signal is predistorted to offset the expected distortion products.

Abstract: A polychromatic or white light laser arrangement for changing the dimensions of the pumped portions of the active medium is realized by employing an optical divider for dividing the pump radiation into at least two beamlets, and one or more lenses for focusing the pump radiation onto the active medium. In one preferred embodiment, the optical divider includes a system of mirrors and lenses, or an acousto-optic deflector.

Abstract: A photoreceiver for frequency-modulated optical signals. The photoreceiver is formed of a semiconductor laser of the FABRY-PEROT type, wherein one of the faces thereof which receives a frequency modulated light beam is given an antireflection treatment. The voltage at the laser terminals is also tapped. Such a device finds particular application to optical telecommunication systems.

Abstract: The present invention relates to the feedback control of the power output from a high-frequency generator for supplying a pulsed laser. During a pulsing operation, the power output is regulated by means of a controllable grid-leak resistor in the grid circuit of the valve tube of the high-frequency generator. An equivalent system is preselected for the feedback control in the pulse intervals and, consequently, transient reactions are minimized.

Abstract: Apparatus for producing signal frequency shifts by stimulated Brillouin scattering comprises a pair of optical fibres (112,113) or a single high birefringence fibre which are illuminated by a laser beam to generate two back-scattered signals by stimulated Brillouin scattering and a mixer (117) to combine the two back-scattered signals to produce a beat frequency from the combined signals.

Abstract: A diffraction limited working beam at a given frequency is amplified without degrading its diffraction limited quality by diverting a minor portion of the beam as a probe beam, and amplifying the remaining portion of the working beam with a high power pump beam at a different wavelength. The amplification takes place in a host medium that has a rare earth dopant with an energy transition from the pump beam's wavelength to the wavelength of the working beam. The resulting amplified working beam is non-diffraction limited. The probe beam is frequency modulated and coupled with the amplified working beam in a second host medium that also has a rare earth dopant. Energy is transferred from the amplified working beam to the modulated probe beam through a resonant energy transfer in the second host medium, producing an amplified output beam at the working beam frequency that retains the diffraction limited quality of the probe beam.

Abstract: An apparatus and method are disclosed for use in an antenna remoting system. The apparatus comprises a single source of laser light having an output characterized by two distinct polarizations and at least two closely separated frequencies, and a fiber optic communications link joined to the source and having a modulator therein which is driven by a radio frequency information signal such that said modulator produces a beat frequency output which is a function of the sum of the two closely separated frequencies.

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: A laser system (10) comprises a microchip laser (11) longitudinally pumped by a laser diode (17). Lens system (18) focusses the pump radiation onto the lasing medium (12) which is in the form of a plate carrying a mirrored surface (13) forming one of the mirrors of the laser (11). The other mirror of laser (11) is formed on a substrate (14) mounted on a piezo-electric ceramic mount (15). Part (21) of the output of the laser (11) is delivered to a cavity (23) which functions as a interferometer the output of which is opto-electric converted at (26) and demodulated at (28) to provide a phase-shifted reference frequency with respect to an oscillator (16) operating at one of the mechanical reference frequencies of the unit formed by components (14) and (15). The reference frequency signal is amplified at (29) and fed with the oscillator output through a coupler (19) to drive the mount (15) so that it is both a frequency modulating and a frequency correcting element.

Abstract: A laser modulator (10) having a low voltage assembly (12) with a plurality of low voltage modules (14) with first stage magnetic compression circuits (20) and magnetic assist inductors (28) with a common core (91), such that timing of the first stage magnetic switches (30b) is thereby synchronized. A bipolar second stage of magnetic compression (42) is coupled to the low voltage modules (14) through a bipolar pulse transformer (36) and a third stage of magnetic compression (44) is directly coupled to the second stage of magnetic compression (42). The low voltage assembly (12) includes pressurized boxes (117) for improving voltage standoff between the primary winding assemblies (34) and secondary winding (40) contained therein.

Abstract: An optical recording system having a laser for generating a light beam to write data to and read data from a storage medium, an RF modulator for modulating the laser to improve its stability, and an apparatus for driving the laser. The apparatus is comprised of a transistor coupled to the laser for supplying current to the laser. An amplifier is implemented to drive the base of the transistor according to a microprocessor. Thereby, the microprocessor effectively controls the power level of the laser. The transistor and the RF modulator are enclosed within shielding to contain the RF energy being generated by the modulator. In addition, the collector-base separation of the transistor reduces the RF energy being transmitted through the line driving the base of the transistor.

Abstract: A monolithic multi-color laser comprising a semiconductor laser formed on a substrate for lightwave generation. Means is provided for exciting the laser and means is provided on the substrate adjacent the laser to double the frequency of the lightwave emitted from the laser to produce output lightwaves having wavelengths in the photo-sensitive region of conventional silver halide photographic material. Further, an individually controllable frequency matched lightwave modulator is mounted on the substrate and is arranged to individually control the output lightwave in response to a data signal.

Abstract: An optical, transmitter with a stabilized operating point for an optical transmitter, especially for that including a Mach-Zehnder optical modulator, is disclosed. An optical modulator is provided which modulates a light beam from a light source according to a driving voltage from a drive circuit. An operating point stabilizing circuit is provided which detects a drift in the characteristic curve from the optical modulator and controls the optical modulator to bring the operating point to a specified position. Deterioration in the waveform of the output optical signal due to the operating point drift is thereby prevented without depending on the input signal. Further, by performing an operating point shift under specific conditions, deterioration in the waveform due to wavelength dispersion can be effectively prevented, whether the sign of the wavelength dispersion is positive or negative.