FIG. 4 illustrates, by way of example, a diagram of an embodiment of beat generator circuitry 120. The beat generation circuitry generates a beat tone, such as based on an optical frequency comb. The beat generation circuitry 120 is configured to receive an optical frequency comb using a first port 420 of the optical circulator 121. The optical frequency comb is transmitted to a sensor (e.g., Fiber Bragg grating 122) using a second port 421 of the optical circulator 121. The Fiber Bragg grating 122 may be configured to return a single tooth of the optical frequency comb using the second port 421 of the optical circulator 121. The single tooth of the optical frequency comb is provided to an optical coupler 123 using a third port 423 of the optical circulator 121. The optical coupler 123 optically mixes the single tooth of the optical frequency comb with an optical signal 422 of a frequency stabilized laser 412 to provide a mixed optical signal 424. The mixed optical signal 424 is received by the photodiode 124 and converted into an electrical signal 425. The electrical signal 425 is the beat tone mixed with the carrier envelope offset of FIG. 1 and FIG. 2.