Measurement system and measurement method of short-delay laser linewidth based on photoelectric feedback

Abstract

The invention discloses an optoelectronic feedback-based short-time delay laser linewidth measurement system. According to the thought of the system, the laser is used for acquiring laser signals s(t), an optical power beam splitter converts the laser signals s(t) into two paths of laser signals, reference light signals 0.5 s(t) and measurement light signals 0.5 s(t) are obtained, a time delay optical fiber carries out phase shift on the measurement light signals 0.5 s(t), measurement light signals s1(t) after phase shift are obtained, an optical coupler carries out coupling on the s1(t) and the reference light signals 0.5 s(t) to obtain combined laser signals sc(t), an optoelectronic detector carries out optoelectronic conversion on the sc(t) to obtain combined electric signals Id(t), an amplifier amplifies the Id(t), combined electric signals Vd(t) after amplification are obtained, a low-pass filter carries out low-pass filtering on the Vd(t), combined electric signals Vf(t) after low-pass filtering are obtained, a voltage-current converter contains set preset electric signals Vpre(t), the Vf(t) and the Vpre(t) are added for conversion from voltage to current, current signals are obtained, the current signals serve as working current of the laser to be sent to the laser, phase noise of the laser signals s(t) is acquired, and thus, a 3dB linewidth of a phase noise power spectrum for the laser signals s(t) is further calculated.

Description

technical field [0001] The invention belongs to the field of optoelectronic technology, and in particular relates to a photoelectric feedback-based short-delay laser line width measurement system and a measurement method thereof, which are suitable for the design of a photoelectric closed-loop feedback mechanism and the realization of line width measurement of narrow line width lasers. Background technique [0002] In recent years, laser-based communication research has become a hot field, among which narrow-linewidth fiber lasers are widely used in optical fiber communication, optical fiber sensing, materials technology etc. [0003] The ground linewidth of early distributed feedback laser (DFB) and distributed Bragg reflection (DBR) laser is on the order of 10MHZ. After using external cavity technology to greatly narrow the spectral linewidth, the laser linewidth can reach or even be lower than the kilohertz level. ; For traditional light sources, spectrum analyzers are g...

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Problems solved by technology

[0003] The ground linewidth of early distributed feedback laser (DFB) and distributed Bragg reflection (DBR) laser is on the order of 10MHZ. After using external cavity technology to greatly narrow the spectral linewidth, the laser linewidth can reach or even be lower than the kilohertz level. ; For traditional light sources, spectrum analyzers are generally used for spectral line analysis. Spectrum analyzers use scanning diffraction gratings as frequency-selective filters. The wavelength scanning range is wide and the dynamic range is large, but the wavelength resolution is limited to only a dozen picometers ( greater than 1GHZ), so it is very difficult to use a spectrum analyzer to analyze a fiber laser with a narrow linewidth of the order of kilohertz

[0004] The two commonly used methods for measuring line width are the double-beam heterodyne method and the time-delayed self-heterodyne method. The double-beam heterodyne method requires two lasers and an acousto-optic modulator, and the experimental system is complicated; Only one light source is needed, the test environment is simple, and it has better stability. However, as the laser line width becomes narrower and narrower, the optical fiber required for delay causes the laser system to be bulky, inconvenient to use, and expensive. As the length of the fiber increases, new problems will arise in the optical path of the system where the laser is located, such as the introduction loss of the optical path, polarization, etc.

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