| CPC H01S 5/0683 (2013.01) [G01B 9/02004 (2013.01); G01B 9/02091 (2013.01); H01S 3/1305 (2013.01); H01S 5/0064 (2013.01); H01S 5/02251 (2021.01); H01S 5/02253 (2021.01); H01S 5/02415 (2013.01); H01S 5/026 (2013.01); H01S 5/06835 (2013.01); H01S 5/142 (2013.01); H01S 5/18361 (2013.01)] | 18 Claims |

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1. A method for closed-loop controlling an absolute wavelength and an optical bandwidth of a swept-source tunable laser, wherein a closed-loop control uses timing information from a signal generated by a reference wavelength filter and an optical element that generates signal pulses corresponding to nearly equally spaced wavenumbers,
wherein said reference wavelength filter and said optical element that generates signal pulses corresponding to nearly equally spaced wavenumber comprises a fiber Bragg grating (FBG) with multiple reflection peaks,
wherein said FBG with multiple reflection peaks has one main reflection peak that is higher in amplitude than all the other reflection side peaks and serves as said wavelength reference filter, all other reflection side peaks generate said signal pulses corresponding to nearly equally spaced wavenumber.
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