Patent ID: 6559994
Filing Date: 2003-05-06
Classification: H04B,H04J,H04L

Abstract:
An optical fiber transmitter for long-distance subcarrier multiplexed (SCM) lightwave systems, the optical fiber transmitter comprising:a pre-distortion circuit, used to receive electrical subcarrier multiplexed signal; an optical modulator, receiving an output of the pre-distortion circuit; an optical signal directing device having a first port, a second port, and a third port, in which the first port receives an output of the optical modulator that is directed to the second port; a chirped fiber grating which is connected to the second port of the optical signal directing device; an output transmission path which is connected to the third port of the optical signal directing device; a first fiber optical amplifier, installed between the optical modulator and the optical signal directing device; wherein the electrical subcarrier multiplexed signals pass through the pre-distortion circuit to generate nonlinearities in advance; wherein the electrical subcarrier multiplexed signals, combined with the nonlinearities, modulate an optical carrier via the optical modulator; wherein as the output of the optical modulator is received by the optical signal directing device at the first port, the output of the optical modulator is directed to the chirped fiber grating, which is connected to the second port of the directing device, and the modulated light is reflected from the fiber grating back to the optical signal directing device through the second port, and then exported to the output transmission path from said third port; wherein the chirped fiber grating has a chromatic dispersion characteristic which is opposite to that of the output transmission path; wherein a bulk part of nonlinear distortions and carrier suppression effects caused by the accumulated optical fiber dispersion in the system is compensated by the chirped fiber grating; wherein the residual nonlinear distortions and the residual carrier suppression effects, which cannot be completely eliminated by the chirped fiber grating, are corrected by the pre-distortion circuit; wherein the residual nonlinear distortions and carrier suppression effects caused by the chirped fiber grating itself are corrected by the pre-distortion circuit as well; wherein the first optical fiber amplifier is used to compensate for the insertion loss of the optical signal directing device and the chirped fiber grating, and the transmission loss of the long distance systems.