Frequency modulated continuous wave (FMCW) frequency sweep non-leaner calibration system based on closed loop control and FMCW frequency sweep non-leaner calibration method based on closed loop control

Abstract

The present invention relates to an FMCW frequency sweep non-leaner calibration system based on closed loop control. The system comprises a frequency sweep laser source, a coupler, a delay optical fiber, an acousto-optic frequency shifter, a photoelectric detector, a frequency spectrum analyzer, a digital phase frequency detector and a summator. Meanwhile, the present invention provides a calibration method of the above system. The method comprises the steps of using the frequency sweep laser source to emit the optical signals of continuous phases, wherein one optical signal is delayed by the optical fiber, and the other one optical signal is carried out the optical frequency shift by the acousto-optic frequency shifter; after the two optical signals are combined, using the balance photoelectric detector to detect a beat frequency optical signal; using the digital phase frequency detector to compare the phases of the beat frequency optical signal and a radio frequency reference signal, and feeding back an outputted error signal to a laser after signal conditioning, thereby finishing the enclosed loop control of a whole loop. According to the present invention, the non-linear output optical frequency of the frequency sweep laser source is calibrated accurately, the output optical frequency linearity is improved obviously, and the spatial resolution of a FMCW ranging system is improved substantially.

Description

technical field [0001] The present invention relates to the technical field of optical frequency modulation, in particular to an optical frequency modulation continuous wave frequency sweep nonlinear calibration system and method based on closed-loop control. Background technique [0002] Optical frequency-modulated continuous wave (FMCW) is a technology that obtains parameters such as the position and velocity of the measured target by measuring the frequency domain response of the beat frequency signal obtained by coherently transmitting the optical signal and the echo signal. Its core module is a frequency linear Modulated laser source. [0003] Among various types of laser sources, narrow-linewidth semiconductor lasers may be the most suitable, because its output frequency can be flexibly controlled by changing the injection current of the laser, however, usually due to the inherent frequency modulation effect of the semiconductor laser itself , the output frequency of ...

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Problems solved by technology

[0003] Among various types of laser sources, narrow-linewidth semiconductor lasers may be the most suitable, because its output frequency can be flexibly controlled by changing the injection current of the laser, however, usually due to the inherent frequency modulation effect of the semiconductor laser itself , the output frequency of the laser exhibits obvious nonlinearity for the modulation current

[0004] The existing method to reduce the nonlinearity of the frequency-sweeping laser source is based on the mechanism of modulating current pre-distortion. However, this method can only reduce the nonlinearity in the output frequency of the frequency-sweeping laser source to a relatively small range, but cannot be completely eliminated in principle, it is difficult to achieve high-precision and large-range linear frequency sweep with this method

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