Low-cost wave characterization modules for oil spill response

Marine oil spills can be remediated by mechanical skimmers in calm waters,but performance degrades with increased wave height.We have developed and demonstrated a system that quantifies local wave characteristics with an uncertainty of four inches of heave.Our system is intended for the measurement of wave characteristics during oil spill recovery.It conveys this information to coordinators and responders in real time via WiFi and remote reporting through a satellite network.This information will allow for enhanced situational awareness during an oil spill response,assisting stakeholders and optimizing mechanical skimming operations.Our wave characterization module(WCM)uses accelerometer outputs from a very small inertial measurement unit(IMU)to generate wave statistics and calculate wave characteristics.It is configured such that a WCM can either be attached to a skimmer float or incorporated into a microbuoy.Wave height and period are transmitted via WiFi and/or a satellite-enabled mesh-grid network to a cloud-hosted geographic information system(GIS).Here,we discuss the bare-bones sensors-plus-algorithm approach we developed by using spring-mass systems to approximate the wave height and period regime of interest.We then describe open water tests carried out using that development system both mounted to a weir skimmer mockup and packaged in a microbuoy.Finally,we present controlled tests in the wave tank at Ohmsett,the National Oil Spill Response Test Facility in New Jersey,with the WCMs communicating the wave characteristics via WiFi to tankside laptops and via satellite to the cloud-based GIS.Snapshot determinations of wave height calculated using the scalar magnitude of the three-axis accelerometer in the IMU were within four inches of the benchmark wave measurement system at Ohmsett.

Characterization of Full-WDM-Band Photodiode Modules Using Raman Amplifiers in the U Band at 40 Gb/s

We present the characteristics of a full-WDM-band photodiode module in 40 Gb/s U-band operation using a Raman amplifier. This module is suitable for wide-band transmission systems with the additional new channels in the U band.

Characterizing a liquid crystal spatial light modulator at oblique incidence angles using the self-interference method

The phase modulation characteristics of a reflective liquid crystal （LC） spatial light modulator （SLM） under oblique incidence are studied by using our proposed self-interference method. The experimental setup of the method is very simple and has good robustness to mechanical vibrations. By changing the gray value of the combined grayscale loaded on the LC-SLM, different sheared fringe patterns, generated by the interference between the constant phase-modulated beam and the ＋1-order diffracted beam of the blazed grating, can be obtained. The amount of phase modulation of the LC-SLM is obtained by subtracting the phase of the two side lobes in the frequency domain. By turning the turntable where the SLM is mounted, the phase modulation characteristics at different incident angles can be measured. The experimental results show that the phase modulation curves do not change significantly with the small angle. When the angle is large （i.e. larger than 10°）, the phase modulation curves become different, especially for the high gray levels. With the increase of the incident angle, the phase modulation depth is reduced. The results indicate that the incident angle plays an important role in the performance of the phase modulation of an LC-SLM.