System and Method for Transmitting Multi-Octave Telecommunication Signals by Up-Shifting into a Sub-Octave Bandwidth

摘要

A system for transporting a plurality of digital data streams over an optical fiber can include a plurality of upstream quadrature amplitude modulation (QAM) modems. Each QAM modem encodes a digital stream onto a carrier signal by modulating both the amplitude and the phase of the carrier signal. Each QAM modem also up-shifts the signal frequency, with each up-shifted signal having a frequency within a single sub-octave frequency band to suppress composite second order distortions that can occur during optical transport. The QAM signals are combined and converted to an optical signal that is transmitted over an optical fiber to a receiver. To convert the signal, a voltage source is connected with an electro-absorption modulator to provide a bias voltage for altering an optical power of the optical signal with a DC offset. The DC offset minimizes third order distortions of signals transmitted on the fiber optic.

主权项

1. A system for transmitting sub-octave telecommunication signals from an upstream end of a fiber optic to a downstream end of the fiber optic, the system comprising:
an upstream signal processor for mapping a data stream into an I-component and a Q-component; an upstream I-Q mixer for establishing the I-component as an in-phase I-signal with an RF carrier frequency f, and for phase shifting the Q-component into a quadrature-phase Q-signal with the same RF carrier frequency f and for producing an up-shifted I-signal and an up-shifted Q-signal and wherein the up-shifted I-signal and the up-shifted Q-signal are within a sub-octave broadband wherein f is between a frequency fL and a frequency fH, wherein fH<2 fL; a summer for uniting the I-signal and the Q-signal; a light source for generating a light beam having a wavelength λ; and an electrical-optical (EO) converter connected to the summer and to the light source to create an optical signal λ carrying the I-signal together with the Q-signal, for transmission over the fiber optic.