Patent ID: 6888991

Claim:
Wavelength Division Multiplexed optical waveguide system providing for a â€œprimary DWDM channel setâ€ at a â€œprimary system wavelengthâ€, the said system including: a transmitter, a receiver, and optical amplifiers, together with a transmission line of optical fiber including at least one fiber span, CHARACTERIZED IN THAT a substantial length of fiber constituting such fiber span is â€œfew-modeâ€ fiber of core radius sufficient to support at least one high-order mode in addition to the fundamental mode at the primary system wavelength, in which the few-mode fiber includes a continuous stream of longitudinally spaced perturbations in value of index-of-refraction, of spacing to selectively extract high-order mode(s) by radiation, whereby the said few-mode fiber is effectively single-mode-operating, and in that provision is made for total launched power of at least 400 milliwatts (mW) into the said fiber span.