Optical transmission
AssigneeBritish Telecommunications plc
InventorDavid Cotter
Life of this patent
Estimating the term…
Abstract
Stimulated Brillouin Scattering, which occurs when light of narrow linewidth and above a threshold power is launched into a low loss optical fiber, is suppressed by time-varying the phase angle of the transmitted light waves.
Claims37
A method of transmitting coherent light along an optical fibre in an optical communication system at power levels which exceed the normally expected Stimulated Brillouin Scattering (SBS) threshold which method comprises:
- launching into the fibre a coherent optical wave having a power level in excess of the normally expected Stimulated Brillouin Scattering threshold and a phase angle which is varied with respect to time in such a manner that Stimulated Brillouin Scattering is substantially suppressed and the power level of the successfully propagated component of the optical wave is increased.
A method of optically transmitting information along light conducting fibres having increased length between required repeater amplifying stations, which method comprises:
- launching into an optical fibre at least one coherent optical wave having a power level in excess of the normally expected Stimulated Brillouin Scattering threshold and having effected phase reversals which occur more frequenly than the spontaneous acoustic dephasing time .DELTA..nu..sub.B.sup.-1 =.pi..GAMMA..sup.-1 (where .GAMMA..sup.-1 =the acoustic phonon lifetime) so as to substantially suppress stimulated Brillouin Scattering, and
- modulating at least one component of said optical wave in correspondence with the information to be transmitted.
A method of transmitting coherent light along an optical fibre, wherein the light linewidth determines a natural Stimulated Brillouin Scattering threshold power level for the fibre, the method comprising:
- generating coherent light having a predetermined linewidth in light generating means,
- introducing recurrent phase deviations in said coherent light, and
- launching said light into an optical fibre at a power level which is above the natural Stimulated Brillouin Scattering threshold power level for the fibre at said predetermined linewidth, wherein the recurrent phase deviations substantially suppress Stimulated Brillouin Scattering.
A method of transmitting and receiving information along an optical fibre comprising:
- transmitting information by launching coherent light of at least one wavelength into one end of an optical fibre, which launched light is modulated in correspondence with the information to be transmitted by a method according to claim 36, 37, 40 or 45,
- coherently detecting the transmitted light emerging from the other end of the fibre, and
- demodulating said detected light to recover said information.
An optical transmission system comprising:
- an optical fibre having a natural stimulated Brillouin scattering power threshold for a given linewidth light,
- light generating means to generate light of predetermined linewidth and at a power above the natural Stimulated Brillouin Scattering power threshold for the fibre at that linewidth,
- means to launch said generated light into the fibre at said excess power level, and
- means for introducing recurrent phase deviations in the transmitted light at a rate which is sufficiently high to substantially suppress Stimulated Brillouin Scattering.
Dependencies are inferred from the claim text.