Patent ID: 8189977

Claim:
Optical device comprising: a) a light source operating at less than 1300 nm, b) a first length of optical fiber attached to the light source, the optical fiber having a core and a cladding wherein said core propagates light with a wavelength less than 1300 nm in a first mode, c) a mode converter attached to the first length of optical fiber for converting light in the first mode to light in a second, higher order, mode (HOM), d) a second length of all-solid glass optical fiber attached to the mode converter the second length of optical fiber having a core and a cladding, e) a second mode converter attached to the second length of optical fiber for converting the HOM to a lower order mode, wherein: i the effective index of the HOM is different from that of any other mode propagating in the said core by at least 0.0001, and ii the total dispersion value of said HOM over the length of the second length of optical fiber is positive and greater than zero and less than +50 ps/nm-km.