Facilities > CDL > Photonic Reference

Photonic Reference

by Eric Bryerton last modified Dec 14, 2012 by Davis Murphy

ALMA requires unprecented levels of phase stability to achieve coherent interfometry up to THz frequencies.  The optoelectronic local oscillator timing reference, distributed as the beatnote between two optical tones, is stable to within 10 fs over 15 km distances.

The development program for the ALMA photonic reference and distribution system developed several key technologies, including:

  • a tunable (30-122 GHz) photonic millimeter-wave synthesizer for generating the high-stability local oscillator reference signal
  • round-trip phase correction to maintain low phase drift over long distances of fiber

Millimeter-wave photomixing

photomixer.jpg

Laser frequency synthesis by phase locking

laser freq synthesis.jpg

Round-trip phase correction by optical interferometry

round trip phase correction.jpg

Customized low phase drift Erbium doped fiber amplifiers

fiber amplifier.jpg

Eurocard standardized optoelectronics packaging

eurocard photonic module.jpg

Dense fiber distribution packaging for arrays

photonics rack 1.jpgphotonics rack 2.jpg