A heterodyne balanced detection system and detection method applied to tdlas direct absorption method under low signal-to-noise ratio

Abstract

The invention discloses a heterodyne balance detection system and detection method applied to the TDLAS direct absorption method under low signal-to-noise ratio. The modulation signal output by the DFB laser is divided into the detection light and the detection light by a 1×2 single-mode fiber beam splitter. The reference light and the probe light are severely attenuated by the environment to be tested. The single-mode fiber time delayer makes the two beams of light produce a phase difference, and the probe light also passes through the multimode noise scrambler to eliminate multimode noise, and forms heterodyne interference in the 2×2 multimode fiber splitter. The signal after heterodyne interference is split 1:1 and connected to a balanced detector to obtain an amplified interference signal with reduced detector noise. In the present invention, the reference light and the detection light are interfered in the 1×2 single-mode fiber beam splitter, and the output is equally divided by the 2×2 multi-mode fiber beam splitter, so that the direct current flow of the two output signals is stable regardless of whether the detection light fluctuates Similarly, access to a balanced detector can balance the anti-noise, which significantly improves the real-time and anti-noise capabilities.

Description

Technical field: [0001] The invention relates to a heterodyne balance detection system and detection method applied to the TDLAS direct absorption method under low signal-to-noise ratio. Background technique: [0002] Tunable Diode Laser Absorption Spectroscopy (TDLAS) is a new type of optical sensor based on laser principle, which is applied to the non-contact measurement of gas concentration and temperature in various environments. Its high-speed feedback and real-time monitoring characteristics make it one of the most important measurement methods in dynamic process control systems. [0003] Direct absorption method (DAS) is a data processing method in TDLAS technology, which is applied in the environment with strong absorption intensity. The two-line exemption from calibration and the need for approximate calculations are advantages over the WMS wavelength modulation method. The biggest disadvantage of DAS is its poor anti-interference ability, low signal-to-noise rati...

AI Technical Summary

Problems solved by technology

However, in actual industrial applications, because the detection signal changes in real time and the attenuation is often greater than 1000 times, it is difficult to adjust the reference light adaptively

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