Abstract: A method of transmitting a plurality n data streams comprises modulating an optical carrier using differential M-ary phase shift key (DMPSK) signaling in which M=2n. Advantageously the method comprises using differential quaternary phase shift keying in which n=2. A particular advantage of the method of the present invention is that since the data is differentially encoded in the form of phase changes rather than absolute phase values this enables the modulated optical carrier to be demodulated using direct detection without requiring a phase-locked local optical oscillator. The invention is particularly applicable to WDM communication systems.

Abstract: Semiconductor laser diodes, particularly broad area single emitter (BASE) laser diodes of high light output power, are commonly used in opto-electronics. Light output power and stability of such laser diodes are of crucial interest and any degradation during normal use is a significant disadvantage. The present invention concerns an improved design of such laser diodes, the improvement in particular significantly minimizing or avoiding degradation of such laser diodes at very high light output powers by controlling the current flow in the laser diode in a defined way. The minimization or avoidance of (front) end section degradation of such laser diodes significantly increases long-term stability compared to prior art designs. This is achieved by controlling the carrier injection into the laser diode in the vicinity of its facets in such a way that abrupt injection current peaks are avoided.

Abstract: A micro-optic dual beam-splitter assembly comprises at least two beam-splitter optical filters and at least one photoreceptor. Each of the beam-splitter optical filters comprises an optical substrate having at least a coated or uncoated optical tap surface and a filter surface carrying a thin-film optical filter. The thin-film optical filters are substantially normal to the optical path from an optical signal source. Each of the optical tap surfaces is operative as an optical beam splitter to tap off an optical tap signal. The one or more photoreceptors are arranged to receive both or at least one of the optical tap signals. The tap signals comprise a portion of the optical signals passed along the optical path to the optical filter chips. The filter chips are cooperatively transmissive to an optical signal output port of a selected set of wavelengths received from the optical signal source along the optical path, and are reflective of other wavelengths.

Abstract: Semiconductor laser diodes, particularly broad area single emitter (BASE) laser diodes of high light output powers are commonly used in opto-electronics. Light output power and stability of such laser diodes are of crucial interest and any degradation during normal use is a significant disadvantage. The present invention concerns an improved design of such laser diodes, the improvement in particular significantly minimizing or avoiding (front) end section degradation at very high light output powers by controlling the current flow in the laser diode in a defined way. This is achieved by controlling the carrier injection, i.e. the injection current, into the laser diode in a novel way by creating single current injection points along the laser diode's longitudinal extension, e.g. along the waveguide. Further, the supply current/voltage of each single or group of current injection point(s) may be separately regulated, further enhancing controllability of the carrier injection.

Abstract: An optical signal is produced from a direct modulation resonant cavity device, such as directly-modulated diode laser having an electrode divided into multiple sections. Each section is driven with an electrical waveform such that a time delay is introduced between sections so as to ensure that the different sections reach their peaks at slightly different times.

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 method of transmitting a plurality n data streams comprises modulating an optical carrier using differential M-ary phase shift key (DMPSK) signalling in which M=2n. Advantageously the method comprises using differential quaternary phase shift keying in which n=2. A particular advantage of the method of the present invention is that since the data is differentially encoded in the form of phase changes rather than absolute phase values this enables the modulated optical carrier to be demodulated using direct detection without requiring a phase-locked local optical oscillator. The invention is particularly applicable to WDM communication systems.

Abstract: A method of controlling a laser is provided for generating an optical output. The method includes the step of making a change to an electrical input to the laser so as to move the optical output of the laser towards a target frequency, and also includes the step of changing the temperature of the laser in relation to the change in the electrical input or the movement of the optical output. The method further includes the step of making further changes to the electrical input as the temperature of the laser is changed so as to maintain the optical output of the laser at the target frequency.

Abstract: An automatic bias controller for an optical modulator is provided. The automatic bias controller comprises a driver for providing an electrical data signal to the modulator and a bias voltage source for providing a bias voltage to the modulator. A microprocessor provides a low frequency digital modulation signal, which is converted to an analogue modulation signal by a digital to analogue converter. The analogue modulation signal is applied to the bias voltage source (so as to modulate the bias voltage) or to the driver (so as to modulate the amplitude of the data signal). Intensity detectors for detecting the intensity of light emitted by the modulator are provided, and an analogue to digital converter converts the output of the intensity detectors to a digital intensity signal which is passed to the microprocessor. The digital intensity signal is analysed, and the bias voltage source instructed to adjust the bias voltage on the basis of the analysed signal.

Abstract: A method of transmitting a plurality n data streams comprises modulating an optical carrier using differential M-ary phase shift key (DMPSK) signalling in which M=2n. Advantageously the method comprises using differential quaternary phase shift keying in which n=2. A particular advantage of the method of the present invention is that since the the data is differentially encoded in the form of phase changes rather than absolute phase values this enables the modulated optical carrier to be demolutated using direct detection without requiring a phase-locked local optical oscillator. The invention is particularly applicable to WDM communication systems.

Abstract: An optical amplifier comprises an optical fibre, a pump laser for optically pumping the optical fibre to amplify an optical signal, a TEC 1 for cooling the pump laser on receipt of a cooling current, a temperature sensor 2 for monitoring the temperature of the amplifier housing; and a control circuit 3 for controlling the cooling current in dependence on a sensing output from the temperature sensor 2, so as to maintain the temperature of the pump laser at a temperature set point. The control circuit 3 is configured (i) to maintain the temperature of the pump laser at a first temperature set point within a predetermined temperature range of the amplifier, and (ii) to maintain the temperature of the pump laser at a second temperature set point, higher than the first temperature set point, when the sensing output from the temperature sensor 2 exceeds a threshold value.

Abstract: A tuneable laser includes a gain section (50) bounded by two mirrors (51 and 52) at least one mirror being a chirp grating. At least one of the mirrors includes a plurality of selectable electrodes (59 to 65) to enable the grating to be selectively activated to produce a selective reflection at a predetermined wavelength.

Abstract: In a light (optical) beam steering/sampling system, a matrix inversion control technique is used to decouple the operation of the actuators which drive the steering mirrors. The control technique uses two virtual variables, each having an associated independent feedback loop operating in a non-cross-coupled manner, each variable being associated with one of the two steering mirrors.

Abstract: A high power laser source comprises a bar of laser diodes, a submount onto which said laser bar is affixed, and a cooler onto which said submount is affixed. The laser bar has a first coefficient of thermal expansion (CTEbar), the submount has a second coefficient of thermal expansion (CTEsub), and the cooler has a third coefficient of thermal expansion (CTEcool) the third coefficient (CTEcool) being higher than both said first coefficient (CTEbar) and said second coefficient (CTEsub). Contrary to the usual approach with a CTEsub matching the CTEbar, the second coefficient (CTEsub) is selected lower than both said first coefficient (CTEbar) and said third coefficient (CTEcool) according to the invention. A preferred range is CTEsub=k*CTEbar, with 0.4<k<0.9. The submount may consist of or comprise two or more layers of different materials having different CTEs, e.g.

Abstract: A device assembly (216) for positioning a device (222) in a precision apparatus (10) includes a first housing (224), a second housing (226), a movement ball joint (229), and a locking ball joint (249). The first housing (224) retains the device (222). The second housing (226) is coupled to an apparatus frame (12). The movement ball joint (229) facilitates movement of the first housing (224) relative to the second housing (226). The locking ball joint (249) facilitates locking of the first housing (224) to the second housing (226). The movement ball joint (229) can guide movement of the first housing (224) relative to the second housing (226). For example, the first housing (224) can include a first guide surface (230) and the second housing (226) can include a second guide surface (232). In this embodiment, the guide surfaces (230) (232) cooperate to form the movement ball joint (229). Additionally, each of the guide surfaces (230) (232) can form a portion of a sphere.

Abstract: According to one example a linear translation stage is provided. The linear stage includes a first portion (e.g., a base portion) and a second portion (e.g., a stage portion) configured for relative translation with respect to each other. One of the first portion or the second portion has a coil associated therewith and the other of the first portion or the second portion has a magnetic source associated therewith. The magnetic source may include one or more magnets to produce a magnetic field that generally encompasses the coil such that current through the coil causes a force on the coil, thereby causing translation of the first portion relative to the second portion.

Abstract: A fiber clamp (220) for clamping an optical fiber (16) includes a first clamp section (228) and a second clamp section (230) that flexibly urges the optical fiber (16) against the first clamp section (228). The second clamp section (230) can include a retainer housing (244) and a pair of spaced apart flexible members (246) that extend from the retainer housing (244). The flexible members (246) flexibly urge the optical fiber (16) against the first clamp section (228). A fastener assembly (232) can be used to urge the clamp sections (228) (230) directly together.

Abstract: An optical assembly (16) for a precision apparatus (10) includes an optical element (234) and a housing (230) that defines a housing cavity (244). The housing (230) includes a body section (238), a removable section (240) and a fastener assembly (242). The body section (238) is secured to an apparatus frame (12) of the precision apparatus (10). The removable section (240) retains the optical element (234) with the optical element (234) positioned in the housing cavity (244). The fastener assembly (242) selective secures the removable section (240) to the body section (238). With this design, the removable section (240) can be selectively removed to repair or replace the optical element (234) and the optical element (234) is supported by a rigid mechanical housing (230) so that the optical element (234) is less susceptible to long term or operating misalignments.

Abstract: A printed circuit board (18) for electrically connecting to an optical subassembly (16) includes a board base (230), a conductive trace (232), and a board conductor (234). The optical subassembly (16) includes at least one component pad (346). The board base (230) is made of a substantially nonconductive material. Further, the board base (230) defines a recessed region (238) that is sized and shaped to receive a portion of the optical subassembly (16). The conductive trace (232) is secured to the board base (230). The board conductor (234) is positioned near the receiver region (238). Further, the board conductor (234) is positioned near the component pad (346) when the optical subassembly (16) is positioned in the receiver region (238). Moreover, the board conductor (234) is electrically connected to the conductive trace (232).

Abstract: A beam modulator (14) for modulating a beam (20) includes a modulator element (26) and a housing assembly (24). The modulator element (26) is positioned in the path of the beam (20). The housing assembly (24) retains the modulator element (26). The housing assembly (24) can include a housing (234), a first retainer assembly (342), and a second retainer assembly (344). The first retainer assembly (342) flexibly secures the modulator element (26) to the housing (24) and the second retainer assembly (344) fixedly secures the modulator element (26) to the housing (234) with the modulator element (26) positioned between the retainer assemblies (342) (344). With this design, the retainer assemblies (342) (344) can cooperate to retain the modulator element (26) in a fashion that applies a substantially uniform and small pressure across the modulator element (26).