Abstract: Tunable external cavity lasers are used in applications such as interferometry, FM spectroscopy, and optical communications equipment testing. Mode hop free high bandwidth frequency modulation operation is desired in a tunable external cavity laser. This application describes new and novel techniques for controlling the output wavelength of a tunable external cavity laser while suppressing mode hop.

Abstract: A multichannel optical amplifier having an adjustable gain set point is controlled to permit substantially constant gain tilt control during a gain set-point change so that the channel powers are maintained during system modification. To this end the amplifier comprises an erbium doped fibre (EDF) loop and associated pump amplifier for amplifying an optical signal comprising channels of different wavelengths, a variable optical attenuator (VOA) for controlling the gain of the amplifier by applying a loss profile that varies with wavelength so that the different channels are amplified in accordance with a required gain tilt, preferably a zero gain tilt, and a PI controller for applying a gain tilt adaptation profile to compensate for an inherent gain tilt to produce the required gain tilt.

Abstract: Semiconductor laser diodes, particularly high power AlGaAs-based ridge-waveguide laser diodes, are often used in opto-electronics as so-called pump laser diodes for fiber amplifiers in optical communication lines. To provide the desired high power output and stability of such a laser diode and avoid degradation during use, the present invention concerns an improved design of such a device, the improvement in particular significantly minimizing or avoiding (front) end section degradation of such a laser diode and significantly increasing long-term stability compared to prior art designs. This is achieved by establishing one or two “unpumped end sections” of the laser diode. One preferred way of providing such an unpumped end section at one of the laser facets (10, 12) is to insert an isolation layer (11, 13) of predetermined position, size, and shape between the laser diode's semiconductor material and the usually existing metallization (6).

Abstract: An improved method is provided for fabricating a polarisation rotator in a rib waveguide having a propagation axis and opposite side walls. The method includes etching a pit in the substrate surface to form a recess in one of the side walls of the waveguide, during formation of the waveguide on the substrate surface, so as to provide an asymmetric waveguide section for imparting polarisation rotation to radiation propagated along the propagation axis. Preferably the pit is formed by a wet etching step forming an upper side surface within the recess that is inclined relative the waveguide side walls, and the waveguide side walls are formed by a dry etching step to extend perpendicularly to the substrate surface. In addition the dry etching step forms a lower side surface adjoining the upper side surface within the recess and tilted relative to the upper side surface.

Abstract: A high speed optoelectronic subassembly in an optoelectronic package is disclosed that includes a dielectric support having a first electrical trace on a surface thereof and a dielectric member mounted on the surface of the support having a second electrical trace thereon. The support extends laterally a distance greater than the member to form a shelf. A dielectric step is positioned on the shelf abutting an end of the member and a laser is positioned on the shelf adjacent the step so as to be light accessible external to the subassembly. The laser and the step have surfaces equal in height and cooperate to provide a mounting platform. A resistive element is positioned on the mounting platform and electrically connected to the laser, the resistive element and laser being electrically externally accessible through the traces.

Abstract: An optical component for gain-flattening multiplexed passband signals amplified with optical pump power, comprises a launch port optical waveguide operative to communicate multiplexed passband signals in a passband wavelength range and optical pump power in a different wavelength range; a thin film demux filter oriented to receive combined multiplexed passband signals and optical pump power from the launch port optical waveguide, and operative to pass the multiplexed passband signals and to reflect the optical pump power; a bypass port optical waveguide operative and oriented to receive and carry optical pump power reflected by the demux filter; a gain-flattening filter positioned to receive from the thin film demux filter and operative to pass the multiplexed passband signals with a desired attenuation profile for gain-flattening; and an output port optical waveguide oriented to receive and operative to carry at least multiplexed passband signals passed by the gain-flattening filter.

Abstract: An optical device comprises a semiconductor structure including first and second ridge waveguides, each waveguide comprising a ridge extending across a surface of the semiconductor structure. The ridge of the first waveguide has a first height above a first region of the surface, and the ridge of the second waveguide has a second, greater, height above a second region of the surface. The semiconductor structure includes a multimode interference (MMI) region situated between the first and second ridge waveguides, which provides a transition between them. At least a part of the MMI region is tapered in width and/or at least a part of the first and/or second ridge waveguide is tapered in width in a direction extending away from the MMI region.

Abstract: The invention concerns a guided wave spatial filter (300) for receiving input radiation and outputting corresponding filtered output radiation, the filter comprising first and second waveguide sections (30, L3, L5) connected in series, the sections: (a) mutually matched for transmitting fundamental mode radiation components present in the input radiation therethrough to provide the output radiation; and (b) mutually mismatched for hindering higher-order mode radiation components present in the input radiation from propagating therethrough and contributing to the output radiation. The spatial filter (300) is implemented using rib waveguides (30) for the sections with associated relatively deeply and relatively shallowly etched structures (20, 310, 320) for imparting to the sections their radiation mode filtration characteristics.

Abstract: A second harmonic generation laser system comprising: a non-linear frequency converting medium; and an external cavity pump laser that produces optical energy at a single mode and at a single frequency and that is disposed to provide the optical energy to the non-linear frequency converting medium.

Abstract: The present invention concerns an anti-reflection coating for semiconductor lasers, in particular a coating on the laser facet with advantageous properties resulting in improved reliability and reduced probability of specific breakdowns, especially so-called catastrophic optical damages (CODs). It is a quarter-wave coating with a predetermined reflectivity, preferably between 0 and 10% and consists of or comprises SiNx:H. It is preferably applied by a Plasma-Enhanced Chemical Vapor Deposition (PE-CVD) process whose process parameters are controlled such that a desired optical thickness and refractive index of the coating are achieved. The PE-CVD process may be controlled to result in an Si/N ratio between about 0.5 and 1.5 and/or to produce a coating of essentially amorphous SiNx:H whose density approaches the density of crystalline Si3N4.

Abstract: A method and assembly for frequency stabilization of an optical signal especially from a laser, the assembly (11) comprising beam splitter (15), a passive frequency discriminator (16), and a pair of photodiodes (17 & 18). The beam splitter (15) in use receives a collimated optical beam (B) and diverts a sample beam (B1) which is directed towards the discriminator (16) which transmits a portion (B2) of said sample beam to one of the photodiodes (17) and reflects a second portion (B3) of said sample beam to the other photodiode (18). A control signal (S3) is derived from the respective intensities of the transmitted and reflected portions of the sample beam, and utilized to operate the electronic control to adjust the frequency of the laser output signal, if required, to maintain a specified frequency.

Abstract: An optical subassembly includes a substrate, a heat spreader, and a submount. The submount has a submount mounting surface and a component mounting surface with either the submount mounting surface or the component mounting surface including an angle. The submount is positioned on either the heat spreader or the substrate such that the component mounting surface is positioned at the angle relative to the substrate. An optoelectric device is positioned on the component mounting surface and coupled to interconnects on the substrate. The optoelectric device is thermally coupled to the heat spreader through the submount to provide a low thermal resistance between the optoelectric device and the heat spreader. An encapsulant structure is mounted on the substrate and hermetically encloses the optoelectric device. The encapsulant structure includes a window positioned to pass light between the optoelectric device and an externally mounted optical fiber.

Abstract: A system is provided for producing wavelength tunable laser light and a signal indicative of the wavelength of the produced laser light; a laser cavity includes an optical gain medium and a wavelength selective element disposed in a path of light emitted by the optical gain medium such that changing a position of the element changes a wavelength emitted by the medium; a position sensor that senses position of the element; position signal circuitry that produces a position signal indicative of position of the element sensed by the position sensor; a storage medium storing at least one position signal corresponding to a respective predetermined position of the element; comparison circuitry for comparing the produced position signal with the at least one stored position signal and for producing a comparison result indicative of whether the element has reached to the predetermined position; marker signal circuitry providing an external wavelength marker signal when the comparison result indicates that the element

Abstract: A tuneable laser has a gain section bounded at one end by a first reflector in the form of a distributed Bragg reflector adapted to produce a comb of reflective peaks and on the other end by a second Bragg reflector, the second Bragg reflector adapted to reflect at a plurality of wavelengths and being capable of being varied selectively through discrete segments so that one or more segments of the Bragg reflector can be tuned to a lower wavelength to reflect with a segment reflecting at that lower wavelength to enhance the reflectivity at that lower wavelength.

Abstract: Gain-flattening components for compensation of at least a portion of the spectral gain profile of an optical amplifier comprises an optical substrate having at least a first gain-flattening filter disposed on a first surface of the optical substrate and a second gain-flattening filter disposed on a second surface of the optical substrate. The first gain-flattening filter has a transmission curve with a spectral loss profile for optical signals in the optical wavelength range, and has a net insertion loss error function relative to the spectral gain profile of an optical amplifier. The spectral loss profile of the second gain-flattening filter corresponds to the net insertion error function of the first gain-flattening filter. Gain-flattening optical amplifiers comprise one or more such gain-flattening components and at least one optical signal amplifier.

Abstract: A multistage optical amplifier is controlled to compensate for the effect of amplified spontaneous emission (ASE) by a method comprising the following steps. Optical input and output signals to a first gain stage are detected, and the drive current to the first gain stage is controlled in dependence on the optical input signal to the first gain stage. Optical input and output signals to a last gain stage are detected, and the drive current to the last gain stage is controlled to maintain the output power of the last gain stage substantially constant. The effect of ASE in the first gain stage is compensated for by applying a correction factor based on the ASE of the first gain stage and the output power of the first gain stage.

Abstract: A mover assembly (16) that moves or positions an object (12) includes a mover output (226), an actuator (230), and a control system (18). The mover output (226) is connected to the object (12), and the actuator (230) causes the mover output (226) to move. The control system (18) selectively directs a drive signal to the actuator (230) in a first mode and in a second mode. In the first mode, a peak voltage and a baseline voltage are sequentially directed to the actuator (230). In the second mode an intermediate voltage is directed to the actuator (230), the intermediate voltage being intermediate the peak voltage and the baseline voltage.

Abstract: An apparatus and method for determining a physical parameter affecting an optical sensor or a number of sensors in a network. The apparatus uses a narrow linewidth source at an emission wavelength ?e and an arrangement for varying the emission wavelength ?e of the radiation. An analysis module with curve fitting is used to generate a fit to the response signal obtained from the optical sensor. The physical parameter is determined form the fit rather than from the response signal. The apparatus can be employed with Bragg gratings, etalons, Fabry Perot elements or other optical sensors.

Abstract: A modulator arrangement for modulating an optical signal using a quadrature phase shift key for use in an optical wavelength division multiplex (WDM) optical communications system comprising a laser (2) for producing an optical signal of a selected wavelength, which signal is split by a splitter (4), each part of said split signal being applied to a respective phase modulator (6, 8) each for which phase modulators is adapted to modulate the phase of the signal in dependence on a respective drive voltages. The phase of the output of at least one modulator (6) is shiftable at least in part by a phase shifter (10), the split signals being recombined by an optical recombiner (12) to form an optical phase shift key output, wherein the output power is monitored by a detector (20), the detector signal then being used to drive a feedback arrangement to control electrodes of the phase modulators (6, 8) and/or phase shifter (10).

Abstract: A tuneable laser having an active section, a phase section and a Bragg reflector comprising a plurality of discrete grating units, at least two of which gratings have a different pitch, wherein current is applicable to at least the grating having a longer pitch, such that the effective wavelength of the grating having a longer pitch can be tuned to the wavelength of the grating having a shorter pitch. A chirp grating can provide the difference in pitch.