Abstract: Method of laser modifying an optical fibre to form a modified region at a target location within the fibre, comprising positioning at least a portion of an optical fibre in a laser system for modification by a laser, applying a correction to an active optical element of the laser system to modify wavefront properties of the laser to counteract an effect of aberration on laser focus, and laser modifying the optical fibre at the target location using the laser with the corrected wavefront properties to produce the modified region.

Abstract: A device for modulation of light (16) having a wavelength, comprising: a first substrate (10) with a first face (81) and a second opposite face (82), and comprising a first electrode (11); a second substrate (20) adjacent to the second face (82) and defining a gap between the first and second substrate (10, 20), the second substrate (20) comprising a second electrode (21); a responsive liquid crystal layer (15) disposed in the gap, wherein the responsive liquid crystal layer (15) has a flexoelectro-optic chiral nematic phase, and is birefringent with an optic axis that tilts in response to an applied electric field between the first and second electrode (11, 21); and a mirror adjacent to the second substrate (20), the mirror configured to reflect incident circular polarised light while preserving its handedness.

Abstract: The information marked on one electronic content is compared to that marked on another electronic content in order to determine if either are unauthorised. There are a number of ways of comparing the information in order to make this determination. One way is to detect if two electronic content accessed by the same device have information associated with different users. Another way is to detect if two electronic content accessed by different devices have information associated with a single user. A further way is to use the time or sequence of access in conjunction with the information. Other ways of determining unauthorised content are disclosed.

Abstract: Systems and methods for interrogating sensing systems utilising bursts of samples. Bursts of samples correspond to optical pulses returning from optical sensors, where pulses are spaced at a period significantly longer than the pulse width, giving irregular sample spacing. The interrogation system and method processes the irregular busts of samples to recover phase information from received signals.

Abstract: Systems and methods for interrogating sensing systems utilising bursts of samples. Bursts of samples correspond to optical pulses returning from optical sensors, where pulses are spaced at a period significantly longer than the pulse width, giving irregular sample spacing. The interrogation system and method processes the irregular busts of samples to recover phase information from received signals.

Abstract: An optical sensing system, comprising a plurality of optical sensors (206 . . . 209), first (203 . . . 205) and second (215, 216) input trees, and first (210 . . . 212) and second (219, 220) output trees. The first and second input trees are configured to direct respective optical signals from a first (202) and a second (214) input to each of the sensors, and the first and second output trees are configured to direct optical signals from each of the sensors (206 . . . 209) to a first (213) and a second (221) optical output. The first and second input and/or output trees are configured to direct signals of particular wavelengths (A1 . . . D-1, A2 . . . D2) from particular sensors to the first and second input and/or output, respectively. A redundant connection system thus provided allows continued operation in the event of a fibre or cable break (300).

Abstract: Optical impairments such as dispersion and fibre nonlinearity are compensated by generating a pre-distorted electrical signal at the transmitter. This signal is modulated onto a carrier signal, so that it is upconverted in frequency. This up converted signal is then used to modulate an optical source. Generally the optical signal will have two sidebands, one of which has the correctly pre-distorted information and the other which is unwanted. Information in the unwanted optical sideband is either filtered optically or electrically. In the preferred embodiments, the transmitter uses a tunable semiconductor laser with an integrated electroabsorption modulator to modulate the light. The preferred receiver is a coherent receiver with a tunable local oscillator laser. The receiver uses an electrical filter to remove the information in the unwanted sideband.

Abstract: A method and system for mitigating effects of dispersion in an optical link. A pair of digital sample streams are synthesized representing a target optical E-field having a spectrum selected such that the convolution of the spectrum with itself yields a signal having beat terms that contain phase information of the target optical E-field. A complex optical modulator is driven in accordance with the computed orthogonal sample values.

Abstract: Optical impairments such as dispersion and fibre nonlinearity are compensated by generating a pre-distorted electrical signal at the transmitter. This signal is modulated onto a carrier signal, so that it is upconverted in frequency. This up converted signal is then used to modulate an optical source. Generally the optical signal will have two sidebands, one of which has the correctly pre-distorted information and the other which is unwanted. Information in the unwanted optical sideband is either filtered optically or electrically. In the preferred embodiments, the transmitter uses a tunable semiconductor laser with an integrated electroabsorption modulator to modulate the light. The preferred receiver is a coherent receiver with a tunable local oscillator laser. The receiver uses an electrical filter to remove the information in the unwanted sideband.

Abstract: A method and system for mitigating effects of dispersion in an optical link. A pair of digital sample streams are synthesized representing a target optical E-field having a spectrum selected such that the convolution of the spectrum with itself yields a signal having beat terms that contain phase information of the target optical E-field. A complex optical modulator is driven in accordance with the computed orthogonal sample values.

Abstract: An underwater telecommunications system has a first underwater cable for carrying data traffic, one or more underwater repeaters, and an underwater power network for supplying power to the repeaters. By providing a separate cable for some or all of the power supply, the power route may be made shorter, thus more power can be delivered, therefore more repeaters can be used, which enables more fiber pairs to be laid, and thus the capacity to be increased.

Abstract: An underwater telecommunications system has a first underwater cable for carrying data traffic, one or more underwater repeaters, and an underwater power network for supplying power to the repeaters. By providing a separate cable for some or all of the power supply, the power route may be made shorter, thus more power can be delivered, therefore more repeaters can be used, which enables more fiber pairs to be laid, and thus the capacity to be increased.

Abstract: An underwater data transmission system has a cable for carrying an optical signal to carry data, and a string of repeaters spaced apart along the cable, for transmitting the data along the cable, and is upgradeable in mid life by including an upgradeable repeater. The system may have a switchable loop to enable upgrading by adding an additional repeater to the loop and switching the loop into the data path. This enables the data capacity to be increased without needing to lift all the repeaters to the surface. This can enable the huge deployment costs of underwater systems to support several generations of advances in optical transmission systems. It makes more use of the usual twenty year design life of the physical infrastructure.