Communication Through Phase-Conjugated Optical Variants

Abstract

An optical transport system configured to transmit at least two phase-conjugated optical variants carrying the same modulated symbols, with the phase-conjugated optical variants in being different from one another in one or more of polarization of light, the time of transmission, spatial localization, optical carrier wavelength, and subcarrier frequency during transmission. The two phase-conjugated optical variants can be generated by a single polarization-diversity transmitter to be orthogonally polarized, and propagate through an optical transmission link with the same wavelength and spatial path. The optical variants are detected and processed at the receiver in a manner that enables coherent summation of the corresponding electrical signals prior to constellation de-mapping. The coherent summation tends to cancel out the deleterious effects of nonlinear distortions imparted on the individual phase-conjugated optical variants in an optical fiber transmission link because said nonlinear distortions tend to be opposite to each other.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority from U.S. Provisional Patent Application No. 61 / 535,548, filed on Sep. 16, 2011, and U.S. patent application Ser. No. 13 / 245,160, filed on Sep. 26, 2011, both entitled “PERFORMANCE ENHANCEMENT THROUGH OPTICAL VARIANTS,” which are incorporated herein by reference in its entirety.BACKGROUND[0002]1. Field[0003]The invention(s) relate to optical communication equipment and, more specifically but not exclusively, to equipment for managing data transport through a nonlinear and / or noisy optical channel.[0004]2. Description of the Related Art[0005]This section introduces aspects that may help facilitate a better understanding of the invention(s). Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.[0006]Forward error correction (FEC) uses systematically generated redundant data to reduce ...

AI Technical Summary

Benefits of technology

The patent describes a method to improve the quality of optical signals transmitted through fiber cables. The method involves using two optical signals that are designed to cancel out nonlinear distortions, which can occur during transmission. By removing the phase conjugation between the two signals and then combining them, the method effectively reduces the impact of these distortions. This can lead to better signal quality and fewer errors in the received data. The method can be used in addition to or instead of other techniques, such as FEC coding.

Problems solved by technology

The cost of this reduction is a concomitant increase in the required forward-channel bandwidth, with the latter being dependent on the overhead of the FEC code.

However, one problem with FEC coding, as applied to optical transport systems, is that the coding-gain differences among various implementable FEC codes usually do not exceed a certain maximum value, as given by Shannon's information capacity theory.

In addition, the digital signal processing (DSP) complexity for capacity-approaching FEC codes can be forbiddingly high.

The constructive summation tends to average out the deleterious effects of both linear and nonlinear noise / distortions imparted on the individual optical variants in the optical transport link because said noise / distortions are incoherent in nature.

Images