Transmission of multiplexed video signals in multimode optical fiber systems

Kennedy Space Center has the need for economical transmission of two multiplexed video signals along multimode fiberoptic systems. These systems must span unusual distances and must meet RS-250B short-haul standards after reception. Bandwidth is a major problem and studies of the installed fibers, available LEDs and PINFETs led to the choice of 100 MHz as the upper limit for the system bandwidth. Optical multiplexing and digital transmission were deemed inappropriate. Three electrical multiplexing schemes were chosen for further study. Each of the multiplexing schemes included an FM stage to help meet the stringent S/N specification. Both FM and AM frequency division multiplexing methods were investigated theoretically and these results were validated with laboratory tests. The novel application of quadrature amplitude multiplexing was also considered. Frequency division multiplexing of two wideband FM video signal appears the most promising scheme although this application requires high power highly linear LED transmitters. Futher studies are necessary to determine if LEDs of appropriate quality exist and to better quantify performance of QAM in this application

Optically generation of rapidly tunable millimeter wave subcarriers using microchip lasers

There is growing interest in applying photonic techniques to the generation of high fidelity millimeter wave signals. This thesis concerns the optical domain generation of rapidly tunable, very low noise millimeter wave subcarrier signals. Specifically, an optical transmitter employing two heterodyned electro-optically tunable microchip lasers has been designed, fabricated and characterized regarding its tuning range, speed, and noise performance. To explain the fast tuning speed observed in the experiment, a theoretical analysis of the laser dynamics during the intracavity frequency tuning process is advanced using the semi-classic Maxwell-Bloch formulation. The theoretical analysis confirms that microchip laser has a virtually unlimited tuning speed. The output of the tunable transmitter is contaminated by the optical phase noise initiating in the microchip laser. A novel phase noise control approach, coined an “optical frequency locked loop” (OFLL), is developed to achieve low noise operation. Unlike conventional techniques, this scheme utilizes a long fiber delay in place of an external reference oscillator to correct the phase error. The optical frequency locked loop outperforms conventional phased locks loops, particularly at higher millimeter wave frequencies. The tunable transmitter was successfully evaluated in the context of a broadband fiber radio downlink experiment.Ph.D., Electrical Engineering -- Drexel University, 200

NASA/ASEE Summer Faculty Fellowship Program: 1988 research reports

This contractor's report contains all sixteen final reports prepared by the participants in the 1988 Summer Faculty Fellowship Program. Reports describe research projects on a number of topics including controlled environments, robotics, cryogenic propellant storage, polymers, hydroponic culture, adaptive servocontrol, and computer aided desig