BTF Card

Dual laster Pound-Dreaver-Hall driver setup. 1550 nm DFBs. Q=10^-5. Less than 20 GHz difference

A precision two-channel controller for 1550 nm DFB butterfly lasers — a differential optical thermometer built as a 3U Eurocard instrument.

Each channel provides low-noise constant-current laser drive, a bipolar linear TEC temperature controller, RF frequency modulation, and a synchronous-demodulation Pound–Drever–Hall lock that holds the laser to the side of an optical resonance. Lasers A and B lock to their own fringe of a shared reference cavity; the beat frequency between them, Δν = S·(TB − TA) with S ≈ 2 GHz/K, is a ratiometric measurement in which slow common-mode drift cancels.