Optically pumped optical waveguide amplifier

An optical amplifier for optically amplifying signals in a signal waveband, in which amplifier optical amplification is performed in an optical waveguide that guides first and second optical modes respectively possessing first and second modal field distributions, and which optical waveguide has a spatial distribution of active amplifying ion that registers with the first modal field distribution to a significantly lesser extent than with the second modal field distribution so as to provide significantly greater amplification of optical power propagating in the second mode than of that propagating in the first, and wherein the waveguide is provided with long period grating perturbations that effect resonant coupling of optical power of said signals in said waveguide from propagation in one of said first and second optical modes to propagation in the other of said first and second optical modes and back again to propagation in said one of said first and second optical modes.

In an optical transmission system having a plurality of WDM channels, a method of optically amplifying optical power propagating in said channels in a length of optically amplifying waveguide that guides first and second optical modes therein and that has a distribution of active optically amplifying ion concentration that provides, when optically pumped, significantly less gain to optical power propagating in one of said first and second optical modes than to optical power propagating in the other of said first and second optical modes, in which method optical pump power is coupled into the second mode of the waveguide, and optical power propagating in said WDM channels is launched into said optically amplifying waveguide in its first mode and is resonantly coupled by grating perturbations from said first mode into said second mode and back again to said first mode.

A method of optical amplification in which gain is provided as the result of propagation of light through an optically amplifying waveguide, the longitudinal distribution of which gain is rendered wavelength dependent by inducing, in the waveguide, resonant coupling of the light from propagation in a first mode to propagation in a second mode and back again to propagation in the first mode wherein the waveguide is provided with spatial distribution of active optically amplifying dopant that affords a greater gain per unit length to one of said first and second modes than to the other.