Temporal Response of the Underwater Optical Channel for High-Bandwidth Wireless Laser Communications

Abstract

This paper describes a high-sensitivity, high-dynamic range experimental method for measuring the frequency response of the underwater optical channel in the forward direction for the purpose of wireless optical communications. Historically, there have been few experimental measurements of the frequency response of the underwater channel, particularly with regard to wireless communication systems. In this work, the frequency response is measured out to 1 GHz over a wide range of water clarities (approximately 1-20 attenuation lengths). Both spatial and temporal dispersions are measured as a function of pointing angle between the transmitter and the receiver. We also investigate the impact of scattering function and receiver field of view. The impact of these results to the link designer is also presented.

UComms: A Conference and Workshop on Underwater Communications, Channel Modeling, and Validation

“…The blue/green band emerges as a favorite based on the optical absorption properties of sea water, with both LEDs and lasers now showing considerable promise, especially with recent advances bringing down the production cost and size, while increasing power and efficiency of these devices. Cochenour et al [10] place these technologies in context with acoustic systems.…”

On received intensity for misaligned underwater wireless optical links

“…In UWOC, alignment is a key issue to have a reliable communication link in point-to-point communication systems. In practice, a precisely aligned UWOC link is hard to maintain due to the seawater turbulence and system misconfiguration, especially when remotely operated vehicles (ROVs) and autonomous underwater vehicles (AUVs) are used [1], [3]- [6]. Misalignment has a detrimental impact on received intensity and then degrades the system performance.…”

“…In [1], the authors analyzed the impact of link misalignment and asserted that sources and/or detectors array(s) may be an efficient way to decrease the sensitivity for link misalignment. Cochenour et al [6] studied the temporal dispersion with alignment or The corresponding author is Y. Dong. loose pointing/tracking and found that larger signal gains can be achieved by increasing the field-of-view (FOV).…”

Underwater optical impulse response measurement using a chaotic lidar sensor

“…Underwater impulse response measurements can quantify the effects of optical absorption and scattering, [5][6][7] which are relevant to underwater lidar systems. [8][9][10][11][12][13][14][15][16][17][18] These impulse response measurements have been made in the blue-green wavelengths using pulsed bulk lasers 8,19,20 or frequencymodulated continuous-wave (FMCW) systems based on diodes or fiber optic transmitters. 21,22 Properties such as the extinction coefficient of the water and the power spectrum of the backscatter's modulation response can be extracted from these measurements.…”