Method and apparatus for reducing polarization dependent gain in Raman amplification
AssigneeTyCom (US) Inc.
InventorDmitri Foursa
Life of this patent
Estimating the term…
Abstract
A method and apparatus for providing broad band Raman amplification with reduced dependence on polarization state and wavelength. Pump beams of adjacent wavelength are perpendicularly polarized to each other. Further, the wavelength spacing between adjacent pump beams is chosen for the given fiber wavelength spectrum and distance between repeater stations such that adjacent pump beams experience the same polarization state evolution as they travel through the fiber.
Claims29
An apparatus for amplifying a plurality of optical channels, each at a respective wavelength, in an optical fiber by Raman amplification comprising:
- a plurality of pump light sources, each of said light sources producing a pump signal of a different wavelength in consecutive order to amplify light signals propagating in said fiber, said pump signal wavelengths selected such that each pump signal is within a wavelength range of its consecutively adjacent pump signal wherein each of said pump signals experience the same polarization evolution in an optical fiber as its adjacent pump signal and wherein each pump signal is perpendicularly polarized relative to its adjacent pump signal;
- and
- a gain spectrum, associated with each of said pump signals, including a gain ripple wherein the combination of said plurality of pump signals produces a total cumulative gain spectrum with a reduced gain ripple as compared with each of said gain spectra associated with each of said pump signals.
The apparatus of claimed 4 wherein each of said pump signals is within a wavelength range of its adjacent pump signal that is within 50% of δf.
A fiber optic transmission system comprising:
- an optical transmitter;
- an optical receiver;
- optical transmission fiber disposed between said transmitter and receiver;
- at least one amplifying apparatus disposed along said transmission fiber, said amplifying apparatus further comprising a plurality of pump light sources, each of said light sources producing a pump signal of a different wavelength in consecutive order to amplify light signals propagating in said fiber, said pump signal wavelengths selected such that each pump signal is within a wavelength range of its consecutively adjacent pump signal wherein each of said pump signals experience the same polarization evolution in an optical fiber as its adjacent pump signal and wherein each pump signal is perpendicularly polarized relative to its adjacent pump signal, and a gain spectrum, associated with each of said pump signals, including a gain ripple wherein the combination of said plurality of pump signals produces a total cumulative gain spectrum with a reduced gain ripple as compared with each of said gain spectra associated with each of said pump signals;
- and
- a coupler for coupling said plurality of pump signals into said optical transmission fiber.
A method for amplifying a plurality of signal beams in an optical fiber by Raman amplification, said method comprising the steps of:
- generating a pump beam comprising a plurality of wavelengths in consecutive order, said wavelengths selected so that each wavelength is within a wavelength range of its consecutively adjacent wavelength or wavelengths such that it would experience the same polarization evolution in an optical fiber as said adjacent wavelengths and wherein light of each wavelength is perpendicularly polarized relative to light of the adjacent wavelength or wavelengths;
- providing a gain spectrum, associated with each of said pump signals, including a gain ripple wherein the combination of said plurality of pump signals produces a total cumulative gain spectrum with a reduced gain ripple as compared with each of said gain spectra associated with each of said pump signals;
- and
- introducing said pump beam into said optical fiber.
A method of transmitting a plurality of wavelength multiplexed signals over an optical fiber and amplifying said signals by Raman amplification, said method comprising the steps of:
- introducing a signal beam into a first end of an optical fiber segment, said beam comprising a plurality of wavelength multiplexed signals;
- generating a pump beam comprising a plurality of wavelengths in consecutive order, said wavelengths selected such that each wavelength is within a wavelength range of its consecutively adjacent wavelength or wavelengths such that each pump wavelength would experience the same polarization evolution in said optical fiber as said consecutively adjacent wavelength or wavelengths and wherein light of each wavelength is perpendicularly polarized relative to light of the adjacent wavelength or wavelengths;
- providing a gain spectrum, associated with each of said pump signals, including a gain ripple wherein the combination of said plurality of pump signals produces a total cumulative gain spectrum with a reduced gain ripple as compared with each of said gain spectra associated with each of said pump signals;
- and
- introducing said pump beam into said fiber.
Dependencies are inferred from the claim text.