Intermediate Frequency Carrier Research Articles

Измерение поля атмосферного ветра с помощью полностью волоконного лидара с длиной волны генерации 1.5 μm

In this paper, we propose a 1.5 µm all-fiber lidar system for atmospheric wind field measurements. The lidar emission source adopts the master oscillator power amplifier 1532 nm single-frequency all-fiber structure with a repetition frequency of 10 kHz. The lidar output energy is 427 µJ, and the maximum peak power is 610 W at the pulse width of 700 ns. The system utilizes Doppler wind speed coherent measurement technology, and the lidar source modulates an 80 MHz intermediate frequency carrier. The maximum longitudinal height signal distance of the lidar system is 4.5 km for atmospheric wind field, and the measurement accuracy can be within the range of 10-2 level. The lidar system can be used to detect high-altitude or long-distance high-precision wind field information. At the same time, the system can play an important role in future atmospheric environment engineering research.

16×10Gb/s symmetric WDM-FOFDM-PON realization with colorless ONUs

A novel symmetric WDM-PON scheme with colorless ONU is proposed. The baseband 4-ASK Fast-OFDM signal is upconverted by an intermediate frequency carrier, reserving a frequency gap between the FOFDM signal and the optical carrier. After distributing different wavelengths to corresponding ONU by AWG, periodic BPFs are employed to extract the optical carriers for upstream transmission, achieving colorless ONUs. A WDM-PON system with 16 colorless ONUs is established, and 10-Gb/s symmetric transmission for each ONU is also realized. Experiment shows that the system tolerance to the intrachannel crosstalk is greatly improved when the crosstalk signal locates at relatively higher frequency band.

Sensor for optically sensing air borne acoustic waves

The present invention relates to an optical sensor of air borne acoustic waves. The sensor comprises means for producing mutually coherent optical sampling and reference beams, which may be combined to form an intermediate frequency carrier, the sampling beam being exposed to the acoustic field, in which acoustic wave induced density variations occur. These density variations produce a variation in the index of refraction and thereupon a phase modulation of the sampling beam. This phase modulation may be recovered by an optical detector and a phase detector as an electrical signal representative of the acoustic signal. The invention has application to security systems.

A new multi-channel heterodyne polarimeter for plasma current and electron density measurements

A spatially-scanning phase-sensitive heterodyne far-infrared (FIR) polarimeter/interferometer for measurement of plasma current and electron densities is described. The instrument utilizes a rotating diffraction grating wheel for the dual purpose of spatially scanning the plasma cross section and providing a Doppler frequency offset for heterodyne detection purposes. Only two detectors are required to obtain accurate interferometric and polarimetric information for 15 discrete spatial chords. A novel approach to the optical processing of the initially linearly polarized probe beam allows the Faraday rotation of the vibrational ellipse to be unambiguously encoded as a phase modulation on the intermediate frequency carrier signals extracted from the two detectors. The plasma birefringence can be recovered from the corresponding amplitude modulation.