Laser Radar Device Offset Frequency Stimulated Brillouin Scattering
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Solution Overview
Problem
Conventional laser radar devices face a decrease in Signal-to-Noise Ratio (SNR) due to the influence of stimulated Brillouin scattering, which limits the output power and efficiency of pulsed light beams when multiple wavelengths are used.
Innovation Solution
A laser radar device that introduces differing offset frequencies to multiple pulsed light beams, amplifies them, and uses a band pass filter to isolate signal components, thereby avoiding stimulated Brillouin scattering and enhancing SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple pulsed light beams with frequency difference larger than 100 MHz are simultaneously incident on the optical high power amplifier, then the output power of the laser radar device can be increased to N times, but the SNR decreases due to stimulated Brillouin scattering
Solution Approach 1:
The patent applies parameter changes by introducing differing offset frequencies to multiple pulsed light beams before they enter the optical high power amplifier. By adjusting the frequency parameters of each beam to be spaced more than 100 MHz apart, the system avoids stimulated Brillouin scattering while maintaining high output power. This parameter modification allows multiple beams to be amplified simultaneously without the harmful scattering effects that would normally reduce SNR.
2Reliability
If the optical power of the local oscillation light beam per wavelength is reduced to avoid saturation in the optical heterodyne receiver, then the backscattered light beams can be detected without saturation, but the SNR per wavelength decreases
Solution Approach 1:
The patent uses an intermediary approach by introducing offset frequencies as a mediator between the transmitted light beams and the detection process. The offset frequencies act as a buffer that prevents stimulated Brillouin scattering in the amplifier, which in turn prevents saturation of the optical heterodyne receiver. This intermediary mechanism allows the system to maintain high SNR without reducing the local oscillation light beam power, as the frequency spacing prevents the scattering effects that would cause saturation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively increases the SNR while preventing the negative effects of stimulated Brillouin scattering, allowing for higher output power and improved efficiency in pulsed light beam transmission and reception.
Implementation Method 1
an optical amplifier for amplifying the plurality of pulsed light beams output from the modulator
Implementation Method 2
an optical antenna for emitting the plurality of pulsed light beams amplified by the optical amplifier into space, and receiving backscattered light beams of the plurality of emitted pulsed light beams
Implementation Method 3
a receiver for detecting respective beat signals from the plurality of backscattered light beams received by the optical antenna
Implementation Method 4
a filter in which frequency bands each including a frequency of signal components included in the plurality of beat signals detected by the receiver are set as pass bands and frequency bands not including any of the frequencies of the signal components are set as cutoff bands
Data Source
AI summary
A laser radar device includes: a modulator (8) for causing a transmission seed light beam to branch, and giving different offset frequencies to a plurality of the transmission seed light beams having branched, and then modulating the plurality of transmission seed light beams into pulsed light beams and outputting the pulsed light beams, or for modulating the transmission seed light beam into a pulsed light beam, causing the pulsed light beam to branch, and giving the different offset frequencies to a plurality of the pulsed light beams having branched, and then outputting the plurality of pulsed light beams; a band pass filter (14) in which a frequency band including frequencies of signal components included in a plurality of beat signals detected by an optical heterodyne receiver (13) is set as a pass band and a frequency band not including the frequencies of the signal components is set as a cutoff band; and an ADC (15) for sampling the beat signals passing through the band pass filter (14) at a sampling frequency.