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OwnerJulian A. Fells, Daniel A. Watley +1inventors
InventorsJulian A. Fells, Daniel A. Watley, Vernon Baker
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The present specification describes strain applicators, incorporating two actuators having different actuation characteristics acting in cooperation, and their use in adjustable optical filters and adjustable dispersion devices (such as compensators) to controllably strain fiber Bragg gratings to alter their reflectance characteristics. Preferred examples of the strain applicators are hybrids of a fast response actuator with a slower device, and provide a wide overall range of adjustment with fast response tuning within that range. The strain applicators are used to provide dither, in particular to provide both in-phase and anti-phase dither of the strains applied to FBGs in a twin-grating compensator. The in-phase dithering enables centering on an incoming signal to be performed and the out of phase dithering dithers the dispersion, enabling the compensator to track changes in dispersion rapidly, using an appropriately arranged control loop. An improved method of extracting a dispersion error signal from optical signals is also described, based on a simplified spectral analysis of data carried by the signals.
A strain applicator for applying longitudinal strain of adjustable magnitude to a length of optical fibre, the strain applicator being adapted for mechanical coupling to the length of fibre and comprising first and second actuators coupled such that the magnitude of the longitudinal strain applied to the length of fibre when mechanically coupled to the strain applicator is dependent on their combined effects, the first and second actuators being independently controllable by respective control signals to adjust the magnitude of said applied strain and being selected to provide different actuation characteristics for adjusting said magnitude.
A method of applying longitudinal strain of adjustable magnitude to a length of optical fibre, the method comprising the steps of:
A method of applying longitudinal strain of adjustable magnitude to a length of optical fibre, the method comprising the steps of:
A device exhibiting linear dispersion of adjustable magnitude, the device including first and second lengths of optical fibre provided respectively with first and second chirped Bragg reflection gratings, and being arranged to define an optical transmission path that includes reflection in both gratings, wherein each of the first and second lengths of fibre is mechanically coupled to a respective strain applicator, the strain applicators being controllable to adjust the reflectance spectra of the gratings, the device further comprising a controller arranged to control the strain applicators such that the reflectance spectra overlap and to dither the strains applied to the gratings in phase with each other to dither the position of the overlap.
A device exhibiting linear dispersion of adjustable magnitude, the device including first and second lengths of optical fibre provided respectively with first and second chirped Bragg reflection gratings, and being arranged to define an optical transmission path that includes reflection in both gratings, wherein each of the first and second lengths of fibre is mechanically coupled to a respective strain applicator, the strain applicators being controllable to adjust the reflectance spectra of the gratings, the device further comprising a controller arranged to control the strain applicators such that the reflectance spectra overlap and to dither the strains applied to the gratings in anti-phase to dither the amount of overlap.
A method of generating a dispersion signal indicative of the dispersion exhibited by an optical path along which an optical signal has been transmitted, the optical signal having been generated by a method comprising the modulation of an optical carrier with an RF data signal having frequency components across an RF data spectrum such that data is carried by the optical signal in upper and lower sidebands on either side of an optical carrier frequency, the method comprising the steps of:
Apparatus for generating a dispersion signal indicative of the dispersion exhibited by an optical path along which an optical signal has been transmitted, the optical signal having been generated by a method comprising the modulation of an optical carrier with an RF data signal having frequency components across an RF data spectrum, such that data is carried by the optical signal in upper and lower sidebands on either side of an optical carrier frequency, the apparatus comprising:
A device exhibiting adjustable reflectance characteristics to optical signals, the device comprising:
A method of providing adjustable reflectance to an optical signal, the method comprising the steps of:
Dependencies are inferred from the claim text.