An Alternative Scheme of Round-Trip Phase Correction Abstract
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ALMA Memo # 519
An Alternative Scheme of Round-Trip Phase
Correction
Hitoshi KIUCHIa and Masoto ISHIGURO
Abstract:
In photonic LO (Local) system, a two-wavelength optical beatnote is transmitted by optical fiber from the AOS technical building to antennas. At an antenna, a photo mixer converts the optical beatnote into a microwave-signal which works as a reference signal for the Worm Multiplier Assembly (WMA). The compensation of instability of transmission line is essential for interferometer to obtain fringes, and is an indispensable process for keeping signal coherence. However, it is delicate to measure an optical cable length delay, because the measured delay includes polarization mode dispersion (PMD). In order to accomplish the phase compensation on the optical fiber, we consider a double-difference method with a polarization alignment servo system.
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