Statistical backscatter suppression technique for a wideband hybrid lidar-radar ranging system

A radio-frequency (RF) intensity-modulated light source at 532 nm was built for underwater ranging. The intensity of a narrow-linewidth laser at 1064 nm was modulated via a Mach-Zehnder electro-optical modulator. The modulation frequency could be tuned from 10 MHz to 2.1 GHz. The intensity-modulated light was amplified via a 2-stage laser diode-pumped Yb 3+ doped large-mode-area fiber amplifier. A 15 mm long magnesium oxide doped periodically-poled lithium niobate (MgO: PPLN) nonlinear crystal was used to convert the 1064 nm light into 532 nm light via frequency doubling. The maximum output power at 532 nm was 2.56 W, the highest efficiency from the fundamental to second harmonic generation (SHG) was 22.6%. The watt level 532 nm light source was applied in underwater ranging experiments. Frequency domain reflectometry (FDR) was applied to retrieve the distances of the objects to the transmitter in a water tank. When the modulation frequency was tuned from 10 MHz to 200 MHz, we obtained ranging accuracy better than 5 cm and ranging resolution smaller than 0.5 cm at 8.6 attenuation length. Two objects spacing by 0.8 m could be resolved simultaneously. The attenuation length at which the object could be detected was limited by the sensitivity of the silicon photodetector. Moreover, we did not use the full bandwidth of the modulation since the lock-in amplifier adopted for data processing had a bandwidth of 200 MHz. Both ranging distance and resolution can be improved if a photomultiplier tube and a high-speed data sampling board were used. Nevertheless, the experimental results showed that the watt level, broadband intensity modulated light source has great potential in underwater detection in terms of ranging accuracy and resolution.

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“…Multiple objects can be detected at the same time with FDR. The unambiguous distance is determined by [17]:…”

Section: Underwater Ranging In Different Watermentioning

confidence: 99%

“…The intensity was directly modulated from 50 to 550 MHz. A photomultiplier tube was used as the receiver, they achieved a detection range of 14.4 AL (Attenuation Length) with a distance accuracy of 5.63 cm [17].…”

Section: Introductionmentioning

confidence: 99%

Application of A Frequency Chirped RF Intensity Modulated 532 nm Light Source in Underwater Ranging

Yang

Liao

et al. 2020

IEEE Photonics J.

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“…With this in mind, we are investigating blind signal separation (BSS) as a method to further suppress backscatter through signal processing [5]. Blind signal separation is a technique in which observations of several signals are separated into independent signal components based on an assumption of statistical independence [6][7].…”

Section: ି௭mentioning

confidence: 99%

Blind signal separation for underwater lidar applications

Illig¹,

Rumbaugh²,

Banavar³

et al. 2016

AIP Conference Proceedings

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Abstract. Blind signal separation (BSS) is demonstrated to improve signal-to-interference ratio (SIR) in underwater light detection and ranging (lidar) applications. Lidar systems are used for high-resolution ranging and imaging underwater. A difficult problem in this area is detecting the return from an object of interest in the presence of a strong "clutter" return caused by backscattering in low visibility water environments. The principal component analysis form of BSS is applied to separate the return into multiple subspaces, with the backscatter subspace suppressed to improve detection capability. Simulations are performed using an underwater optical channel model to simulate a challenging harbor-like environment. We show that the processing gain from BSS is increased when the correlation energy between observations is increased, for example by using closely spaced observations. The SIR gain of BSS is explored as a function of frequency, achieving substantial gain independently of carrier frequency. This result has important implications on the design of lidar systems, suggesting that BSS can be combined with low-cost, low-frequency components to achieve performance similar to systems using high-frequency components.

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“…OCMR have been well developed from visible spectra to near infrared spectra due to the mature intensity modulated light sources and photo detectors [16]- [19]. A 442 nm modulated semiconductor laser has been applied to a wideband hybrid lidar-radar modulation scheme, to achieve ranging performance out to 14.7 attenuation lengths in laboratory experiments [20]. G. Pillet used a 1.5 μm dual-frequency laser which provided a modulated beam with a modulation frequency tunable over 1 GHz.…”

Section: Introductionmentioning

confidence: 99%

Frequency Chirped Intensity Modulated Mid-Infrared Light Source Based on Optical Parametric Oscillation

Yang

Wang

et al. 2020

IEEE Photonics J.

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Optical carried microwave radar (OCMR) has better resistance to turbulence and scattering than conventional laser radar for using intensity modulated laser beam as detection medium. Intensity modulated mid-infrared source is the key to mid-infrared OCMR system. A frequency chirped intensity modulated mid-infrared light source with tunable wavelength is presented. Single frequency output from a non-planar ring oscillator (NPRO) was modulated via a Mach-Zehnder electro-optic modulator (EOM). The modulation frequency was tuned from 10 MHz-2.1 GHz. The modulated light was amplified via a two-stage ytterbium-doped fiber amplifier (YDFA). The amplified 1064 nm laser was used to pump a signal light resonance optical parametric oscillator (OPO). The nonlinear crystal was a 50 mm long magnesium oxide doped periodically-poled lithium niobite (MgO:PPLN) crystal. Single frequency oscillation was realized by adding a 0.2 mm-thick Fabry-Perot (F-P) etalon in the resonator. When the pump power was 15.2 W, the idler output power at mid-infrared was 2.16 W. The maximum pump-idler conversion efficiency was 16.5%. The wavelength of the idler light was tuned from 3.1 μm to 3.8 μm by changing the temperature of the MgO:PPLN crystal. The frequency chirping linearity with respect to time was 0.9937 on average with modulation frequency tuned from 10-350 MHz. The frequency instability was less than 1.5 Hz in 200 seconds at a modulation frequency of 300 MHz.

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Statistical backscatter suppression technique for a wideband hybrid lidar-radar ranging system

Cited by 9 publications

References 15 publications

Application of A Frequency Chirped RF Intensity Modulated 532 nm Light Source in Underwater Ranging

Application of A Frequency Chirped RF Intensity Modulated 532 nm Light Source in Underwater Ranging

Blind signal separation for underwater lidar applications

Frequency Chirped Intensity Modulated Mid-Infrared Light Source Based on Optical Parametric Oscillation

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