Performance Comparison of Power Divider and Fiber Splitter in the Fiber-Based Frequency Transmission System of Solar Radio Observation

Time-frequency synchronization plays an important role in the construction of solar radio telescopes (such as heliograph and interferometry). In the development of a synchronization system, time-frequency signal is divided and transmitted to each antenna in an array, therefore, the performance of the signal splitting devices determines the quantity of the data. To address this situation, we designed a frequency transmitting system, and conducted a test to compare the phase difference among outputs (10 MHz - 1.4 GHz), and the deterioration of the frequency stability (10 MHz - 1GHz) brought by different splitting devices (fiber splitter and power divider). The following results had been obtained: 1) Phase difference introduced by both fiber splitter and power divider can be restricted in a range of ±4°, and the fiber splitter is rather stable, which indicate that a better imaging effect of heliograph can be achieved when using fiber splitters. 2) Frequency stability deterioration get better (worse) with increasing temperature for fiber splitter (power divider) in the testing frequency range for a short-time sampling (100 ms), and for a long-time sampling (10 min), the frequency stability of different devices is determined by both temperature and signal frequency. By estimating the SNR, the performance of optical splitter is found to be slightly better than power splitter. This article provides a basis for the selection and compensation of frequency transfer system components for integrated aperture heliograph, and provide a feasible solution of the construction of low-cost radioheliograph.