Photon noise 光子噪声

Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to noise power, often expressed in decibels. A ratio higher than 1:1 (greater than 0 dB) indicates more signal than noise.信噪比（SNR或S/N）是科学和工程中使用的一种测量方法，用于比较期望信号的水平与背景噪声的水平。信噪比定义为信号功率与噪声功率之比，通常以分贝表示。比值大于1:1（大于0db）表示信号大于噪声。
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SNR is an important parameter that affects the performance and quality of systems that process or transmit signals, such as communicat