Calibrated Fabry-Perot etalon as an absolute frequency reference for OFDM communications

Abstract

The frequency locking of a large number of lasers in OFDM applications requires an equally large number of stable references at predictable frequencies. The authors present a technique to lock a Fabry-Perot etalon on an atomic reference to provide multiple and evenly spaced absolute frequency references. Absolute etalon spacing is calibrated by matching two atomic references with two corresponding etalon modes. To maintain long-term stability in channel spacing, the etalon is locked to an atomic resonance using an electrical feedback loop to control mirror separation. This technique can be used for close spacing or coherent applications where channel separation and reproducibility is critical between transmitter and receiver.