Abstract: A compact confocal scanning laser ophthalmoscope comprising a MEMS scan mirror with a compact scan head, for use with small animal subjects. The scan head is connected to the source, detector and control electronics by flexible optical and electrical umbilicals and includes a zoom lens to provide both a wide field of view and high resolution imaging of the retina using a range of imaging modalities.

Abstract: Ingest data for virtual volumes (V) is split into segments (B1, B2, B3, B4) of a size that can be buffered in main memory. Data deduplication processing then occurs directly on the segments (B1, B2, B3, B4) in main memory, without the need for disk I/O.

Abstract: Ingest data for virtual volumes (V) is split into segments (B1, B2, B3, B4) of a size that can be buffered in main memory. Data deduplication processing then occurs directly on the segments (B1, B2, B3, B4) in main memory, without the need for disk I/O.

Abstract: A method of encrypting an optical communications signal involves determining an encryption function, filtering an electrical input signal using the encryption function to generate an encrypted electrical signal, and modulating an optical source using the encrypted electrical signal to generate a corresponding encrypted optical signal. This is then transmitted through an optical communications system. The encryption is selected such as to substantially remove symbol definition from the optical signal. This method provides digital signal processing of an electrical input signal in order to derive a signal for controlling an optical modulator in such a way that the optical signal transmitted over the link is a continuous analogue signal rather than a series of discrete symbols which alternate between well-defined signal values. This makes it difficult for a third party to derive the binary bit sequence encoded by the optical signal.

Abstract: A 3D scanning apparatus configured to image a physical entity comprises a radiation projector for projecting a plurality of radiation stripes onto the physical entity, a detector for detecting striped radiation received from the physical entity; and a data storage device for storing the received radiation as a pixellated bitmap image, the apparatus characterised in that the physical entity, the radiation projector and the detector are geometrically arranged to constrain the number of times that each received stripe is permitted to occur in a given pixel row of the bitmap, the geometrica) constraint determining a stored occlusion classification comprising a plurality of types of occlusions and the apparatus additionally comprising an occlusion type processing means configured to utilise the classification for detecting the various types of occlusions in said received image data.

Abstract: A transmitter for an optical transmission system transmits an optical sub carrier multiplexed signal comprising number of sub-carriers, onto an optical transmission path, and provides spectral shaping by different magnitudes of the sub-carriers, or different modulation formats for different sub carriers. This spectral shaping can reduce performance degradation by Kerr effect optical non linearities. This can mean higher input powers may be launched. The magnitudes can provide a signal spectrum which is lower near a center of a band of sub carriers than near an edge of the band. Such spectral shaping can be provided in the receiver either to undo the pre emphasis in the transmitter, or to reduce non linearities from components at the receiving side.

Abstract: An optical communications system has a plurality of spans between a transmitter and a receiver. The receiver has optical to electrical conversion circuitry for converting the received optical signal to an electric signal, analogue to digital conversion circuitry and digital signal processing means for analysing the electrical digital signal. The digital signal processing means derives information concerning characteristics of individual spans from the electrical digital signal. This enables parameters such as per-span variations in provisioned power, local dispersion and span loss to be measured. In-service measurements of system characteristics can be used to enable optimisation of the network operation.

Abstract: A 3D scanning apparatus configured to image a physical entity comprises a radiation projector for projecting a plurality of radiation stripes onto the physical entity, a detector for detecting striped radiation received from the physical entity; and a data storage device for storing the received radiation as a pixellated bitmap image, the apparatus characterised in that the physical entity, the radiation projector and the detector are geometrically arranged to constrain the number of times that each received stripe is permitted to occur in a given pixel row of the bitmap, the geometrica) constraint determining a stored occlusion classification comprising a plurality of types of occlusions and the apparatus additionally comprising an occlusion type processing means configured to utilise the classification for detecting the various types of occlusions in said received image data.

Abstract: An optical receiver for receiving an optical differential phase shift keyed signal has an optical component sensitive to the optical phase of the signal, such as an interferometer, a device arranged to generate a control signal by non linear limiting of an output of the optical component, such as an RF amplifier arranged to operate in a region near saturation point, and a phase controller for tuning a phase response of the optical component to the received signal according to the control signal.

Abstract: A polarization diversity receiver has an optical section for converting the received optical signal into four or five polarization diverse component optical signals that substantially represent amplitude and polarization state information of the received optical signal, by respective polarization transformations to respective points on a Poincaré sphere, the points being equally spaced apart to maximize polarization diversity, even in the worst case input polarization state. Detectors produce component electrical signals from each of the component optical signals, for electronic processing to compensate for PMD. By reducing the number of component optical signals significant cost and size reductions are enabled. The need for precise polarization tracking in the receiver can be reduced or eliminated completely. Balanced detectors can be used to reduce the number of electrical signals. The electrical processing can use sequence detection.

Abstract: An optical fiber for communications systems, the fiber being designed to ensure a compensation of Kerr effects. The fiber has a profile which ensures that changes in power produce changes in distribution of power between core and cladding, such that the phase change associated with the changed spatial distribution of the power, is equal and opposite to the phase change due to Kerr Effect.

Abstract: A transmitter for an optical transmission system transmits an optical sub carrier multiplexed signal comprising number of sub-carriers, onto an optical transmission path, and provides spectral shaping by different magnitudes of the sub-carriers, or different modulation formats for different sub carriers. This spectral shaping can reduce performance degradation by Kerr effect optical non linearities. This can mean higher input powers may be launched. The magnitudes can provide a signal spectrum which is lower near a centre of a band of sub carriers than near an edge of the band. Such spectral shaping can be provided in the receiver either to undo the pre emphasis in the transmitter, or to reduce non linearities from components at the receiving side.

Abstract: The invention provides a method of balancing the power level of an optical signal within an aggregate of optical signals in an amplified dense wavelength division multiplexing DWDM optical network, as well as power balancing apparatus therefor.

Abstract: An optical amplifier comprises a doped fiber core and a cladding layer surrounding the core. The mode field diameter of the fiber is greater than 8 ?m and the refractive index difference between the core and the cladding layer is selected such that the cut-off wavelength at which the fiber becomes single mode lies in the range 1000-1550 nm. This amplifier uses a large made field diameter fiber, which reduces the intensity for a specified output power. This results in reduced filtering of the low frequency components of the signal. The refractive index difference between the core and cladding is selected such that the fiber is multi-mode at 980 nm, which enables bend performance to be improved.

Abstract: An optical fibre for communications systems, the fibre being designed to ensure a compensation of Kerr effects. The fibre has a profile which ensures that changes in power produce changes in distribution of power between core and cladding, such that the phase change associated with the changed spatial distribution of the power, is equal and opposite to the phase change due to Kerr Effect.

Abstract: A polarization diversity receiver has an optical section for converting the received optical signal into four or five polarization diverse component optical signals that substantially represent amplitude and polarization state information of the received optical signal, by respective polarization transformations to respective points on a Poincaré sphere, the points being equally spaced apart to maximise polarization diversity, even in the worst case input polarization state. Detectors produce component electrical signals from each of the component optical signals, for electronic processing to compensate for PMD. By reducing the number of component optical signals significant cost and size reductions are enabled. The need for precise polarization tracking in the receiver can be reduced or eliminated completely. Balanced detectors can be used to reduce the number of electrical signals. The electrical processing can use sequence detection.

Abstract: The invention provides a method of balancing the power level of an optical signal within an aggregate of optical signals in an amplified dense wavelength division multiplexing DWDM optical network, as well as power balancing apparatus therefor.

Abstract: An optical dispersion compensation device includes a first optical compensation unit that applies non-linear dispersion compensation across a signal band, the first optical compensation unit being coupled to a second optical compensation unit that applies a degree of linear dispersion compensation across the signal band. The approach taken is to provide broadband dispersion compensation by applying dispersion slope compensation across the signal band to equalise residual dispersion slope and by applying a degree of linear compensation separately to affect the required linear dispersion compensation. Using these two degrees of freedom it is possible to set the desired dispersion slope and linear dispersion (whether positive or negative) to affect broadband dispersion compensation without needing to demultiplex the optical signal.

Abstract: Dispersion compensation devices are described which comprise waveguides including sampled Bragg gratings which exhibit comb-like reflectance characteristics. The profile of effective refractive index along the length of the grating is controlled to adjust the position of the teeth and/or to control the dispersion exhibited by the device (i.e. to control the chirp of the grating). The devices can thus be used to provide dispersion compensation to any one of a number of wavelength channels in a WDM system. In preferred arrangements, the effective refractive index distribution is set by a applying a temperature distribution along the length of the grating, or by setting an applied electric field.

Abstract: A hybrid optical fiber comprises a first fiber section comprising a fiber or a concatenation of fibers having first dispersion characteristics at a predetermined operating wavelength and a second fiber section coupled to the first fiber section to form the hybrid fiber. The first fiber dispersion characteristics are selected to maintain the signal dispersion within desired limits, whereas the second fiber is optimised for low loss. Dispersion compensation is provided in the first section of the fiber span where the signal intensity is highest, and therefore the region of the fiber span where these non-linearities have greatest effect. In the second section of the fiber span, the non-linear effects can be ignored, so it is optimised for low loss rather than for dispersion compensation.