Microwave photonic link SFDR (Spurious Free Dynamic Range) enlarging method based on automatic light gain control

Abstract

The invention provides a new microwave photonic link SFDR (Spurious Free Dynamic Range) enlarging method. According to the method, an automatic light gain control function is additionally increased in front of a photodetector of a link, light power entering into the photodetector is traced and tuned, so that the total power of third-order cross modulation is less than a noise bottom, furthermore fundamental frequency item power greater than the noise bottom is ensured, and thus, the purpose of enlarging the SFDR is achieved. The automatic gain link is composed of a light beam splitter, a circulator, a fiber bragg grating, the photodetector, a voltage conversion module and a light intensity modulator, wherein the received light is split into two beams by the light beam splitter, one light beam serves as monitoring light, after carrier wave is filtered out by the grating, the monitoring light is subjected to photoelectric conversion, so that a control voltage signal is formed. The control voltage is injected into the direct current bias input port of the light intensity modulator in front of the photodetector, the intensity of the other light beam is controlled by use of the optical interference theory, and the automatic light gain control function is achieved, so that the SFDR of the whole link is enlarged.

Description

technical field [0001] The invention relates to a method for improving the stray-free dynamic range of a microwave photon link, more specifically, it relates to the combined use of electro-optical intensity modulation and optical automatic gain control. Background technique [0002] Microwave photonics is a cross-platform discipline intersecting the microwave field and photonics field. It was formally proposed in 1991. Its essence is to use photonics technology to generate, eliminate, process, and analyze microwave signals. Due to its inherent advantages such as low transmission loss of optical signals, microwave photonics has been researched and applied in many fields, such as broadband wireless access networks, satellite communications, optical signal processing, electronic warfare systems, and optical coherence tomography. In these application fields, while people are pursuing high speed, high bandwidth and large dynamic range of the system, they also have high requiremen...

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Problems solved by technology

The first scheme needs to strictly control the three DC bias voltages of the dual-parallel MZM, which is easily affected by the DC drift of the modulator, while the second scheme needs to use complex instruments to control the optical sideband phase, which greatly increases the system the cost of

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