Patent ID: 9166695
Filing Date: 2015-10-20
Classification: H01S,H04B

Abstract:
1. An optical frequency locking method for tuning each of a plurality of narrow-band optical channel transmit signals to a respective dedicated optical channel frequency, the channel transmit signals having arbitrary channel frequency spacings, the method comprising, for each channel transmit signal, the steps of: (a) tapping-off a portion of the optical power of the channel transmit signal to be tuned and filtering the tapped-off channel transmit signal using at least one optical filter device having a periodic transfer function, at least one of the channel frequency spacings of the channel transmit signals being unequal to the periodicity of the transfer function; (b) monitoring, as an optical input signal, the optical power of the channel transmit signal supplied to the at least one optical filter device, and monitoring, as an optical output signal, the optical power of the filtered channel transmit signal; and (c) tuning, within a predetermined locking range for the dedicated optical channel frequency, the optical frequency of the respective channel transmit signal such that a predetermined value for a target ratio is reached, the target ratio comprising the ratio of the optical output signal and the optical input signal corresponding to the respective dedicated optical channel frequency, wherein the predetermined locking range is defined by, (i) determining a first spectral distance between the respective dedicated channel frequency and a first neighboring point at a lower frequency having the same value of the ratio of the optical output and input signal as the predetermined value of the target ratio and determining a second spectral distance between the respective dedicated channel frequency and a second neighboring point at a higher frequency having the same value of the ratio of the optical output and input signal as the predetermined value of the target ratio, and (ii) using as the locking range either the whole range between the first and second neighboring points, or the range between the frequencies defined by the respective dedicated optical channel frequency plus and minus the smaller one of the first and second spectral distance.