The Hybrid Sensor Bus is a space-borne temperature monitoring system for telecommunication satellites combin- ing electrical and fiber-optical Fiber Bragg Grating (FBG) sensors. Currently, there is no alternative method for testing the functionality and robustness of the system without setting up an actual sensor-network implementing numerous FBG sensors in which each must be heated and cooled individually.
The HSB system acquires the temperature data over the reflection of the single-ended FBG sensor-network. As a novel verification method for the HSB system, an FBG-emulator is implemented to emulate the necessary FBG sensors. It is capable to emulate any given FBG spectrum, thus any temperature immediately. The concept provides advantages such as emulating different kinds of FBGs with any peak shape, variable Bragg-wavelength λB, maximal-reflectivity rmax, spectral-width, and degradation characteristics. Further, the emulator facilitates an efficient evaluation of different interrogator peak-finding algorithms and the capability of emulating up to 10000 sample points per second.
This paper, different concepts for an emulator and material selection regarding the Variable Optical Attenuator (VOA) as the main actuator are discussed. In order to implement a fast opto-ceramic VOA, issues like high temperature dependencies, high control voltages, and capacitive load have to be overcome. These issues are resolved by a custom designed precise temperature controller, and an HV amplifier end-stage providing up to 200 V. Furthermore, a self-calibration procedure mitigates problems like attenuation losses and long-term drifts. A dual-LuT memory handling method enables the emulator to operate at high rates without any interruption. Finally, the emulator’s functionality and its performance are verified over long and short term measurements.