Coherent Brillouin optical time-domain analysis sensing system based on phase modulation probe light

Abstract

The invention discloses a coherent Brillouin optical time-domain analysis sensing system based on phase modulation probe light. In the system, an electro-optic intensity modulator is driven by an electric pulse signal to externally modulate light carrier waves to generate pump light, the electro-optic intensity modulator working at a carrier wave inhibition point is driven by a microwave signal to externally modulate light carrier waves to generate local light, the local light is externally modulated through an electro-optic phase modulator to generate symmetric side bands as the probe light, and the electro-optic phase modulator is driven by a frequency-adjustable radio-frequency signal. Two components of the probe light scan a Brillouin gain area and a loss area of the pump light respectively at the same time, and losses of the pump light can be dynamically compensated so that non-local effects can be reduced while amplitude modulation is carried out on the pump light by a Brillouin gain spectrum. Frequency beating is carried out on the probe light and the local light through a photoelectric detector, information of the Brillouin gain spectrum is loaded to GHz high-frequency carrier waves to avoid base band noise damage, and meanwhile the signal-to-noise ration of the whole system is improved through coherent detection.

Description

technical field [0001] The invention relates to a Brillouin optical time domain analysis sensing system in the field of distributed optical fiber sensing, in particular to a Brillouin optical time domain analysis sensing system based on phase modulation detection light and capable of coherent detection system. Background technique [0002] Temperature and stress sensing based on Brillouin backscattering signals in optical fibers has attracted extensive attention in recent decades. Compared with electrical sensors and fiber grating sensors, its main advantages are longer sensing distance (up to 100km), higher spatial resolution (up to 1cm) and the use of the transmission fiber itself as a sensor. Common distributed optical fiber sensing technologies based on the Brillouin backscattering effect include Brillouin optical time domain reflection sensing technology and Brillouin optical time domain analysis sensing technology. The structure of the Brillouin optical time-domain r...

AI Technical Summary

Problems solved by technology

The first problem is that there are high requirements for the microwave source, and the second is that the signal-to-noise ratio of direct detection is low

Method 1) Using sideband light as pump light will cause non-local effects because the pump consumption cannot be dynamically compensated. Method 2) uses electro-optical phase modulator for carrier suppression modulation, which will introduce coherent noise due to low carrier suppression ratio. Multiple sidebands generated by carrier suppression can degrade system performance

Images