Abstract:
There is described a distributed optical fiber sensor for detecting one or more physical parameters indicative of an environmental influence on a sensor optical fiber, as a function of position along the sensor fiber. The sensor uses probe light pulses of different wavelengths. At least some of the probe light pulses may also be of different pulse lengths. The relative phase bias between interferometric signals in backscattered probe light of different wavelength pulses may also be controlled.
Abstract:
A retroreflective device comprising a substantially spherical graded refractive index lens, referred to as a GRIN-sphere lens (2), a reflective part for retroreflecting (6) a radiation beam (B) passing through the graded refractive index lens and, at least partially surrounding the lens, a transparent material (4) having a substantially uniform refractive index.
Abstract:
An optical termination element for terminating an optical fiber carrying a signal of first maximum power level comprises a termination fiber which is unable to propagate a fiber fuse when the signal power is below a threshold power level which is greater than the first maximum power level. The termination fiber is designed by selecting values of the core diameter and the higher mode cutoff wavelength. The intention provides a termination component in which a fiber fuse can not be initiated at the maximum power to be provided to the termination.
Abstract:
There is disclosed a distributed optical fibre sensor arranged to deliver probe light pulses of different wavelengths into corresponding different sensing optical fibres, and to determine one or more parameters as functions of position along each of the sensing fibres from detected backscattered light of each corresponding wavelength. In another arrangement, the different wavelengths are directed in different corresponding directions around a loop of sensing optical fibre.
Abstract:
This invention relates to retroreflective devices and systems incorporating such devices; the term “retroreflective devices” as used herein being intended to encompass generally optical components used for returning radiation automatically from a remote location toward an optical source. In one aspect, an embodiment of the invention is a retroreflective device comprising a lens having a non-planar outer surface; and a liquid crystal cell having a non-planar layer comprising liquid crystal material, said non-planar layer having a shape corresponding with that of the non-planar outer surface of the lens. The device includes a reflective part arranged to retroreflect a radiation beam passing through the lens, and the liquid crystal cell is arranged to modulate one or more characteristics of said retroreflected radiation beam. Embodiments of the invention are advantageous for use in applications that require thin, transmissive modulators that are compatible with non-planar retroreflecting devices. Liquid crystals offer a useful modulation action for optical path lengths of 1 mm and less, and, since the local orientation of their molecular symmetry axes can be controlled by the fabrication process so as to vary with position, they can be made to be locally optimum over the whole of the reflecting surface of the non-planar retroreflecting device. In addition, liquid crystal devices are associated with low power requirements, which make them advantageous for use in power-limited applications.
Abstract:
Compensating for polarization mode dispersion in a birefringent optical transmission fibre is achieved by controlling the birefringence of the fibre. The difference in group velocity of the orthogonal polarization states of an optical signal transmitted over the fibre is monitored to generate an error signal representing the difference. The birefringence of the fibre is adjusted accordingly to minimize the difference and thereby provide dynamic compensation. Birefringence control may be achieved by a non-linear fibre grating written into the fibre to impose a differential time delay. The fibre may be a side hole fibre (SHF), a holey fibre (HF), a photonic crystal fibre (PCF), or any other suitable microstructure fibre. The fibre may have stressing rods, may be tapered along its length and may be controlled electrically, mechanically, acoustically or thermally by spaced heating elements.
Abstract:
An optical component for halting the propagation of a fiber fuse through a transmission fiber has a threshold power level which is greater than the transmission power level of the system for that transmission fiber. The component comprises a fiber which is selected such that it is unable to propagate a fiber fuse when the power is below the threshold power level. The component is designed by selecting values of the core diameter and the higher mode cutoff wavelength of the fiber making up the component. If power surges are experienced which exceed the transmission power level (the transmission fiber being designed to operate at the transmission power levels without fiber fuses being initiated) then the component provide a safety margin.
Abstract:
There is disclosed a distributed optical fiber sensor arranged to deliver probe light pulses of different wavelengths into corresponding different sensing optical fibers, and to determine one or more parameters as functions of position along each of the sensing fibers from detected backscattered light of each corresponding wavelength. In another arrangement, the different wavelengths are directed in different corresponding directions around a loop of sensing optical fiber.
Abstract:
There is described a distributed optical fibre sensor for detecting one or more physical parameters indicative of an environmental influence on a sensor optical fibre, as a function of position along the sensor fibre. The sensor uses probe light pulses of different wavelengths. At least some of the probe light pulses may also be of different pulse lengths. The relative phase bias between interferometric signals in backscattered probe light of different wavelength pulses may also be controlled.
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.