Optical systems of the present invention include a plurality of optical processing nodes in optical communication via at least one signal varying device. The signal varying devices includes an optical fiber suitable for facilitating Raman scattering/gain in a signal wavelength range and a pump energy source for providing pump energy in a plurality of pump wavelengths. The pump source provides sufficient pump energy in each pump wavelength to stimulate Raman scattering/gain in the optical fiber within the signal wavelength range. The pump wavelengths are selected such that the combined Raman gain resulting from the pump energy supplied by each pump wavelength produces a desired signal variation profile in the signal wavelength range. In addition, the pump energy supplied by at least one of the pump wavelengths can be varied to produce a controlled signal intensity variation profile over the signal wavelength range in the optical fiber.

Optical signal varying devices

An array of optical fibre sensors comprises an optical fibre structure having a series of reflective discontinuities formed by spaced fusion splices between fibre elements of different refractive indices. The structure may comprise a number of equal long lengths of fibre 4 of one refractive index joined by short lengths of fibre 5 of a different refractive index. One end of each short length is fully fusion spliced to one long fibre length (no reflective interface) whilst either the other end is partially fusion spliced or an index matching medium is disposed between the other end and the other long length in order to obtain a single reflective interface. Alternatively, alternate long lengths of fibre (6,7) with different refractive index may be partially fused together at their ends to form reflective interfaces (8). Pairs of laser pulses of slightly different frequency passing along a fibre having equally spaced reflective interfaces are partly reflected to a detector where they are heterodyned to detect phase shifts due to deformation forces (eg acoustic waves) acting on the fibre.

Optical fibre sensors

An optical system (10) including plural optical processing nodes (14) in optical communication via a plurality of signal varying devices (12). A first signal varying device including an optical fiber (30) configured to produce Raman scattering/gain in a signal wavelength range and a first signal variation profile. A first pump (12) with multiwavelengths output stimulates Raman scattering/gain within the signal wavelength range. A second signal varying device (12) having a second signal variation profile to produce a cumulative signal variation profile that differs from the first and second signal variation profiles.

Optical transmission systems including signal varying devices and methods

Optical systems of the present invention include amplifiers configured to achieve maximum signal channel in a span downstream of the transmitter and amplifier site and to decrease the interaction between the wavelengths at high signal channel powers. In addition, the system can include various types of optical fiber positioned in the network to provide for increased signal channel powers and higher gain efficiencies in the system.

Optical transmission systems including optical amplifiers, apparatuses and methods

An optical attenuator uses a segment of attenuating fiber interposed in the optical path. The attenuating fiber is produced by using a solution doping technique to introduce transition or rare earth elements into the fiber's core. The dopant reduces the transmission of the fiber. The degree of attenuation depends upon the material used as the dopant, the dopant level, and the length of the attenuation segment. In a specific embodiment, an optical attenuator is provided having a first and second signal carrying optical fibers and an attenuating fiber segment, each of which has a core, a cladding substantially coaxial with the core, and a substantially planar endface. The attenuating fiber segment is fusion spliced between the first and second signal carrying optical fibers. In a second embodiment a portion of the cladding of the attenuating fiber is chemically etched.

All fiber attenuator

A single mode optical fibre preset attenuator is made by forming a fusion splice (2) between a length of silica fibre possessing no internal waveguiding structure to a length (1) of single mode optical fibre. Then the silica fibre is cut to a predetermined length to form a short stub (3) which is fusion spliced to a second length (4) of single mode fibre. The fusion splicing equipment may subsequently be used to heat soften the central region of the stub to enable it to be shortened or lengthened to fine tune the attenuation provided.

Robertson Alexander John

Papers

Single mode optical fibre attenuators

Optical fibre attenuators