Narrow-linewidth laser phase noise measurement system

Abstract

The invention belongs to the technical field of photoelectricity, and provides a narrow-linewidth laser phase noise measurement system which comprises a direct current laser to be measured, an optical isolator, an optical coupler, a delay optical fiber, a Faraday rotating reflector, a first polarization controller, a second polarization controller, a coherent receiving module, a data acquisition module and an off-line digital signal processing module. A time delay module is used for delaying an optical signal, the coherent receiving module is used for performing coherent demodulation on local oscillation light and signal light to recover a same-direction component and an orthogonal component (I / Q) with laser phase noise information, and the off-line digital processing module is used for recovering phase noise and line width of the laser. Through cooperation of the components, the length of the delay optical fiber of a coherent detection system can be reduced, polarization stability control of an optical signal is helped to a certain extent, the phase noise and line width characteristics of a laser can be obtained at the same time, and a laser with the line width lower than 10 kHz can be measured. The system has the advantages of being simple in structure and easy to operate.

Description

technical field [0001] The invention relates to the field of optoelectronic technology, in particular to a narrow-linewidth laser phase noise measurement system—a self-homodyne optical coherent receiving system with a Faraday rotating mirror. Background technique [0002] With the rapid development of Internet applications, the society's demand for communication capacity is increasing dramatically. The introduction of high-order modulation formats and ultra-dense wavelength division multiplexing optical communication can meet the growing demand for communication capacity. The rapid development of this type of optical communication is inseparable from various high-performance optoelectronic devices, such as narrow linewidth lasers, high-speed modulators, and high-speed detectors. Among them, the narrow linewidth semiconductor laser has the excellent characteristics of narrow linewidth, low noise, high frequency stability and high coherence, and its ultra-narrow spectral linew...

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Problems solved by technology

The delay self-heterodyne method can only measure the linewidth value of the laser, and the system needs a long delay fiber to remove coherence, but too long delay fiber will cause the beat frequency signal to broaden, so it is not suitable for narrow linewidth laser linewidth measurement

[0005] To sum up, the traditional linewidth measurement method is not suitable for narrow linewidth lasers, and can only obtain the linewidth value of the laser, and cannot characterize the phase noise of the laser

However, the currently proposed system for measuring laser phase noise mainly has the following problems: the phase detection method and the frequency detection method have small measurement bandwidths, the coherent method requires long-delay optical fibers, and the polarization is not easy to control

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