Low noise optical link development at INRIM

At the beginning of 2009 INRIM, the Italian metrological laboratory, started a research activity in order to realize a low noise optical link. Two telecom fiber lasers at 1550nm have been locked on two independent notched ultralow expansion glass (ULE) Fabry-Pérot cavities. We present the thermal stabilization system, and report the finite-element analysis (FEA) made to precisely determinate the positions of the cavity supports. The sensitivity of optical axes length to acceleration is found to be less than 4.5 pm/g. Two different commercial lasers are stabilized by a Pound-Drever-Hall (PDH) technique and a stability of 6×10
⁻¹⁴
is achieved at 1 s. Finally, the experimental set-up for the optical link is described and a first noise cancellation result on a 25 km long fiber is reported.