Automatic bias voltage control system and method for double-parallel Mach-Zehnder modulator

Abstract

The invention discloses an automatic bias voltage control system and method for a double-parallel Mach-Zehnder modulator. The system comprises a light emitting module, a radio frequency driving module, the double-parallel Mach-Zehnder modulator and an automatic bias voltage control device; the double-parallel Mach-Zehnder modulator is used for receiving an optical signal and an radio frequency signal with polarization, and a outputting a bias voltage control signal by the bias voltage automatic control device and modulating the same; the bias voltage automatic control device is used for receiving a modulated optical signal. In the system, perturbation of sine waves of different frequencies is utilized; simultaneous regulation, control and locking of the two paths of sub-intensity modulators are achieved. A main modulator direct current phase modulation electrode bias point is locked at an orthogonal point by searching a perturbation first harmonic extreme point, and a sub-intensity modulator bias point is locked at any bias point by analyzing a perturbation first harmonic and average optical power ratio function. And a preset bias point is quickly locked through numerical calculation of the bias voltage correction value, a specific signal value is extracted after locking and compared with a reference value, and the locking effect is verified. Automatic real-time closed-loop control of bias voltage is realized by switching bias voltage control of different direct-current phase modulation electrodes.

Description

technical field [0001] The invention relates to the technical field of optical communication, in particular to an automatic control system and method for the bias voltage of a dual-parallel Mach-Zehnder modulator. Background technique [0002] At present, four-level pulse amplitude modulation (4Pulse Amplitude Modulation, PAM4) has become a mainstream modulation format for medium and short-distance optical communications. Electro-optic modulation is divided into laser direct modulation and external modulation. Mach-Zehnder modulator (MZM) is a typical external modulation device. MZM includes Y-branch optical waveguide, high-frequency electrodes, DC electrodes, etc. After the pulsed light enters the Mach-Zehnder modulator, it is divided into two beams through the Y branch. The general splitting ratio is 50:50. The light beam is coherent through the Y splitter, and the phase change generated by the electrical signal modulation is converted into a change in the intensity and...

AI Technical Summary

Problems solved by technology

[0006] Aiming at the problem that the PAM4 bias voltage control of the dual parallel Mach-Zehnder modulator is difficult, the present invention provides a dual parallel Mach-Zehnder modulator bias voltage automatic control system and method. The bias voltage automatic control device can use closed-loop analog and digital Circuit realizes automatic control of PAM4 bias voltage of dual parallel Mach-Zehnder modulators

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