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Atacama Large Millimeter/submillimeter Array (ALMA)

MZM Laser Synthesizer, ALMA Project
Image Credit: Derek Kubo
MZM Laser Synthesizer, ALMA Project
Internal photos of the Laser Synthesizer instrument. Left - top view of optical components including FBG assembly that houses optical filters, couplers and switch; Amonics erbium doped fiber amplifier along with other auxiliary items. Right - bottom view consisting of Centellax RF power amplifier, Sumitomo Mach Zehnder modulator, DC power supplies, and ADAM monitor & control.
This instrument, aka Alternate Laser Synthesizer, was designed to produce a low phase noise central local oscillator for the ALMA array. The development was conducted as a risk reduction effort in parallel with TeraXion’s more complex approach of using slave lasers. This LS unit produces a pair of tunable optical tones at frequencies in the 192 THz regime (1556 nm) using a relatively simple Mach Zehnder modulator device. The optical signal is distributed to the antenna where a photo-mixer produces an ultra low phase noise difference frequency ranging from 30 - 122 GHz. The difference frequency is used to lock the WCA PLL for one of ten different receiver cartridges. The mechanical packaging developed for this project consists of a commercial EMI chassis along with a custom optics bench style aluminum deck plate and has subsequently been used as our ASIAA standard for custom designs. Size, weight, and power consumption are 10 x 22 x 8.75 inch, 19.1 kg, and 58 Watts. This unit was developed as a joint effort between ASIAA (Derek Kubo - hardware/test, Ranjani Srinivasan - software/test) and NAOJ (Hitoshi Kiuchi - consultant).
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