基于InGaAs光电二极管设计了一种高灵敏度的近红外光纤光功率计。该光功率计的前置放大电路采用多档放大量程设计,外加屏蔽盒,提高了测量动态范围。采用差分放大器、差分A/D转换芯片抑制系统的共模噪声。通过温度传感器测量了环境温度,使用D/A转换芯片对前置放大电路进行动态调零,从而抑制了系统的杂散光噪声、光电探测器的暗电流噪声以及光电探测器的温度漂移。测试表明,该光功率计在光纤通信光波段的光功率测量灵敏度达到-90 dBm,测量动态范围、系统信噪比、线性度等指标均显著提高。

A high sensitivity near infrared fiber-optical power meter is designed on the basis of InGaAs photodiodes. Because the preamplifier circuit of this optical power meter is designed with a multilevel amplification range and a shielding box is added in, the measurement dynamic range is improved. In the power meter, the system common-mode noise is suppressed by a differential amplifier and a differential A/D conversion chip; the ambient temperature is measured by a temperature sensor; and the preamplifier circuit is adjusted to zero automatically by a D/A conversion chip. Thus, the stray light noise of the system, the dark current of the photoelectric detector and the temperature drift of the photoelectric detector are suppressed. The test results show that the light power measurement sensitivity of the fiber-optical power meter is up to -90 dBm in the fiber-optical communication band. Its measurement dynamic range, system signal-to-noise ratio and linearity are improved notably.