Methods and apparatus for detecting and compensating bandwidth limitation and modulation nonlinearity of coherent optical transponder

Abstract

In some embodiments, an apparatus includes a memory and a processor operatively coupled to the memory. The processor is configured to send a stimulus signal at a frequency that corresponds to a firstfrequency value to a tributary channel of a coherent optical transponder. The processor is configured to adjust an amplitude of the stimulus signal and receive a first plurality of output optical power values. The processor is configured to adjust the frequency of the stimulus signal and receive a second plurality of output optical power values. The processor is configured to determine a bandwidthlimitation and a modulation nonlinearity, and then send a first signal to a first filter to reduce the bandwidth limitation and a second signal to a second filter to reduce the modulation nonlinearity.

Description

technical field [0001] Some embodiments described herein relate generally to methods and apparatus for improving the performance of coherent optical transponders in optical communication systems. In particular, but not by way of limitation, some embodiments described herein relate to methods and apparatus for detecting and compensating for bandwidth limitations and modulation nonlinearities of coherent optical transponders in optical communication systems. Background technique [0002] With the increasing demand for optical communication systems with high data rate performance, optical quadrature amplitude modulation (QAM) signals are generated to provide high data carrying capacity and high frequency efficiency. Quadrature Amplitude Modulation (QAM) is a modulation technique in which two or three binary or multilevel electronic data signals are transmitted through in-phase (or "I" channel) and quadrature (90 degree) phase (or "Q" channel) are modulated onto a single optica...

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Problems solved by technology

In addition to bandwidth limitations, modulation nonlinearities can arise from the transfer function of the optical modulator and / or from the nonlinear amplitude response of various components within the optical repeater

[0004] Known solutions to compensate for bandwidth limitations do not yield satisfactory results for optical repeaters with high baud rates (eg >400G) or with high amplitude signals

Furthermore, known solutions often measure the coupling effects of bandwidth limitations and modulation nonlinearities, and thus compensate for the lack of precision

Known solutions to compensate for modulation nonlinearity often compensate for effects from one of the transfer function and the nonlinear amplitude response of the optical modulator, and thus lack satisfactory results

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