Book Synopsis Accuracy of Analog Fiber-Optic Links in Pulsed Radiation Environments by :
Download or read book Accuracy of Analog Fiber-Optic Links in Pulsed Radiation Environments written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Interferometric fiber-optic links used in pulsed-power experiments are evaluated for accuracy in the presence of radiation fields which alter fiber transmission. Amplitude-modulated format (e.g., Mach-Zehnder) and phase-modulated formats are compared. Historically, studies of radiation effects on optical fibers have focused on degradation and recovery of the fibers transmission properties; such work is either in the context of survivability of fibers in catastrophic conditions or suitability of fibers installed for command and control systems within an experimental facility [1], [2]. In this work, we consider links used to transmit realtime diagnostic data, and we analyze the error introduced by radiation effects during the drive pulse. The result is increased uncertainties in key parameters required to unfold the sinusoidal transfer function. Two types of modulation are considered: amplitude modulation typical of a Mach-Zehnder (M-Z) modulator [3], and phase modulation, which offers more flexible demodulation options but relies on the spatiotemporal coherence of the light in the fiber. The M-Z link is shown schematically in Fig. 1, and the phase-modulated link is shown in Fig. 2. We present data from two experimental environments: one with intense, controlled radiation fields to simulate conditions expected at the next generation of pulsed-power facilities, and the second with radiation effects below the noise level of the recording system. In the first case, we intentionally expose three types of single-mode fiber (SMF) to ionizing radiation and study the response by simultaneously monitoring phase and amplitude of the transmitted light. The phase and amplitude effects are evidently dominated by different physical phenomena, as their recovery dynamics are markedly different; both effects, though, show similar short-term behavior during exposure, integrating the dose at the dose levels studied, from 1 to 300 kRad, over the exposure times of 50 ps and 30 ns. In the second case, we present data using a state-of-the-art fiber-optic link for single-shot transmission and recording, fielded at the OMEGA laser facility on high-yield fusion experiments. Gamma reaction history data are measured with a gas Cherenkov detector (GCD) [4], [5] and transmitted by M-Z link to a 12 GHz digitizer. Since radiation effects on the fibers are not above the noise floor, the error analysis for the unfolded data is dominated by the performance of the fast digitizer, the photoreceiver, and the laser.
