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Local Oscillator Reference Test Module, ALMA Project

Image Credit: Derek Kubo

Internal photos of LORTM instrument. Left - top view of optical components including Sumitomo Mach Zehnder modulators (x2), Centellax RF power amplifiers (x2), Amonics erbium doped fiber amplifier, fiber Bragg grating filters, along with other auxiliary items. Right - bottom view consisting of DC power supplies, ADAM monitor & control, TexaXion laser, and Miteq IF power amplifier.

This instrument was developed specifically for the East Asia Front End Integration Center (EA-FEIC) to test the dewar with its associated receiver cartridges for the ALMA project. The LORTM unit produces three tunable optical tones at frequencies F1, F2, and F3 in the 192 THz regime (1556 nm). An external pair of photo-mixers are used to produce difference frequencies of F3 - F1 (30 - 122 GHz) to lock the Warm Cartridge Assembly LO, and F2 - F1 (34 - 118 GHz) to lock the Signal Test Source. The packaging utilizes our ASIAA deck plate design for conductive thermal management in a 10 x 22 x 8.75 inch EMI chassis designed to be mounted on the FEIC tilt table located in a thermal chamber. The unit consumes 103 Watts of power and has a mass of 23.5 kg. This unit was developed as a joint effort from Johnson Han in Taipei and Derek Kubo/Ranjani Srinivasan in Hilo.