Low-noise co-arm differential sensor for an optical frequency comb sampling an E-field test system.

Optical frequency comb (OFC) technology can realize the rapid measurement of electric fields (E-fields) with large bandwidth. However, this technology suffers from the problem of high intensity noise, resulting in low sensitivity and a blind frequency region. In order to solve the above problems, a dual-path optical E-field sensor with a common reference arm based on a lithium niobate optical waveguide is proposed. The introduction of the reference arm improves the balance of optical paths and the degree of integration. A segmented electrode is also designed to ensure the generation of reverse electrical signals on two Mach-Zehnder interferometers (MZIs). After exiting from the differential photodetector (PD), the intensity noise can be removed, and the sensitivity of the sensor can be improved. After testing, the maximum intensity noise reduction is about 37 dB, the average noise reduction is about 22.3 dB, and the blind frequency region can be eliminated with the co-arm differential optical E-field (CDOE) sensor in the process of measuring the signal. This sensor can be used in the 1 MHz-12 GHz bandwidth with a sensitivity better than 10 mV/m·âˆšHz.

Bandpass filter and frequency-time mapping method for pulse measurement with optical delay.

The pulse signal's transients and low duty cycle characteristics lead to excessive omission and erroneous amplitude measurement in signal capture. We offer a combined microwave photonics frequency-time mapping and optical delay electrical pulse measurement system. Beneficial from the true delay of a long fiber with several paths, the pulse is extended to have a more significant duty cycle so as to boost the capturing possibility. We adopt the bandpass filter to avoid sampling the low-frequency range, prevent phase noise from affecting the signal measurement, and improve the signal-to-noise ratio (SNR). This solves the phase noise issue induced by multiple optical delay paths. The proof-of-concept experiments conduct that a 25 µs pulse with a 50 µs period is stretched to a continuous wave, and the SNR is improved by 7 dB.

Study on an Animal Model of Seawater Immersion Injury Following Hemorrhagic Shock.

INTRODUCTION: To establish an animal model of delayed intravenous resuscitation following seawater immersion after hemorrhagic shock (HS). METHODS: Adult male SD rats were randomly divided into three groups: group NI (HS with no immersion), group SI (HS with skin immersion), and group VI (HS with visceral immersion). Controlled HS in rats was induced by withdrawing 45% of the calculated total blood volume within 30 min. In SI group, immediately after blood loss, 0.5 cm below the xiphoid process was immersed in artificial seawater, at (23 ± 1) °C, for 30 min. In VI group, the rats were performed by laparotomy and the abdominal organs were immersed in (23 ± 1) °C seawater for 30 min. Two hours after seawater immersion, the extractive blood and lactated Ringer's solution were delivered intravenously. The mean arterial pressure (MAP), lactate, and other biological parameters were investigated in different time points. The survival rate of 24 h after HS was recorded. RESULTS: After seawater immersion following HS, MAP and abdominal viscera blood flow decreased significantly, and the plasma levels of lactate and the organ function parameters were increased than the baseline. The above changes in VI group were more serious than those in SI and NI group, especially in myocardial and small intestine damage. The hypothermia, hypercoagulation, and metabolic acidosis were also observed after seawater immersion; the injury was more severely in VI group than that of SI group. However, the plasma levels of sodium, potassium, chlorine, and calcium in VI group were significantly higher than those before injury and in the other two groups. In the VI group, the level of plasma osmolality in instant, 2 h, and 5 h after immersion was 111%, 109%, and 108% of the SI group, respectively, all P < 0.01. The 24-h survival rate of VI group was 25%, which was significantly lower than that of SI group (50%) and NI group (70%), P < 0.05. CONCLUSIONS: The model fully simulated the key damage factors and field treatment conditions, reflected the effects of low temperature and hypertonic damage caused by seawater immersion on the severity and prognosis of naval combat wounds, and provided a practical and reliable animal model for the study of field treatment technology of marine combat shock.