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Method and apparatus for algorithm on flexible square-QAM coherent detection

a coherent detection and flexible technology, applied in the field of methods and apparatuses for coherent detection of flexible square-qam, can solve the problems of not being flexible for the deployment of dynamic modulation format, not well compatible with 16qam, and not being able to apply carrier recovery

Active Publication Date: 2016-02-23
ZTE (USA) INC
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Problems solved by technology

However, CMA is not well compatible with 16QAM because high order QAM no longer presents constant symbol amplitude and equalized signal error cannot approach to zero.
The common problem is that the algorithm needs re-configuration and re-initialization so they are not flexible for the dynamic modulation format deployment.
But it is unrelated to carrier phase so that cannot be applied for carrier recovery.
Although conventional DD-LMS algorithm is compatible with all kinds of modulation formats, it is too sensitive to phase error.
Besides, carrier phase is blindly recovered simultaneously because phase error is reserved in the cost function.

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  • Method and apparatus for algorithm on flexible square-QAM coherent detection
  • Method and apparatus for algorithm on flexible square-QAM coherent detection
  • Method and apparatus for algorithm on flexible square-QAM coherent detection

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[0013]It is to be understood that the figures and descriptions provided herein may have been simplified to illustrate elements that are relevant for a clear understanding of the present invention, while eliminating, for the purpose of clarity, other elements found in typical algorithms on flexible square-QAM coherent detection systems and methods. Those of ordinary skill in the art may recognize that other elements and / or steps may be desirable and / or necessary to implement the devices, systems, and methods described herein. However, because such elements and steps are well known in the art, and because they do not facilitate a better understanding of the present invention, a discussion of such elements and steps may not be provided herein. The present disclosure is deemed to inherently include all such elements, variations, and modifications to the disclosed elements and methods that would be known to those of ordinary skill in the pertinent art of optical network operation.

II. Ope...

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Abstract

In Software defined elastic optical networks, modulation format and constellation size may be flexibly modified. As a result, digital signal processing (DSP) algorithm should be compatible with different modulation schemes or readily reconfigurable at the optical coherent receiver. Therefore we propose a novel cascaded adaptive blind equalizers based on decision-directed modified least mean square (DD-MLMS) algorithm for polarization separation and carrier phase recovery. The algorithm is square quadrature amplitude modulation (QAM) independent so that it could be applied in the elastic optical systems. The 28 Gbaud polarization multiplexing quadrature phase shift keying (PM-QPSK) and PM-16QAM back-to-back transmission is demonstrated. The results show that the performance is very close to the general algorithm but with a benefit of the reduced operation complexity. We transmit the 8×240 Gb / s PM-16QAM wavelength division multiplexing (WDM) signal over 1200 km standard single mode fiber (SSMF) based on the proposed blind equalization with a bit error ratio (BER) less than 2×10−2.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This Application claims the benefit of U.S. Provisional Application 61 / 757,991 filed on Jan. 29, 2013, the entirety of which is incorporated herein by reference.BACKGROUND OF THE INVENTIONI. Introduction[0002]For 100 Gb / s and beyond optical transmission systems, the flexible and adaptive bandwidth, known as elastic bandwidth, enables to efficiently distribute data according to the needed capacity and transmission length. Consequently the software defined elastic optical networks are becoming more and more attractive and important at present [1]-[4]. In this software defined networking (SDN), modulation format and constellation size may be flexibly modified. In that case, digital signal processing (DSP) must be compatible with different modulation schemes or readily reconfigurable at the receiver. Polarization multiplexing quadrature phase shift keying (PM-QPSK) is proposed and commercially available for 100-Gb / s optical transmission syste...

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): H03H7/30H04L27/38H04L25/03
CPCH04L27/3818H04L25/03038H04L2025/03617
Inventor YU, JIANJUNHUANG, BO
Owner ZTE (USA) INC
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