The Optical Master Clock

The system optical master clock will be implemented by a 600-MHz repetition mode-locked laser (MLL). The packaging of the laser will allow having a compact and rugged system suitable for inclusion in the SOLE system rack and deployable in the test field.

The packaged laser base plate and mirror mounts are made of Al alloy. The performances of the laser are in line with the needs for the SOLE system. In Fig. 1 a), the MLL optical spectrum is plotted, whose centre wavelength is 1561.8 nm and BW 12.1 nm. Such an optical BW corresponds to a pulse duration of ~670 fs. Fig. 1 b) depicts the first line of the laser RF spectrum, around 600 MHz. Apparently, the line is very pure, since the signal-to-noise ratio (SNR) is larger than 60 dB. The laser output power (measured in free space) is 80 mW. Table 1 summarises the laser main parameters.

Fig. 1: a) optical spectrum; b) RF spectrum. FWHM: Full-width at half maximum; rbw: resolution bandwidth.
Parameter Specification
Pulse repetition rate 600 MHz
Output power 80 mW
Center wavelength 1561.8 nm
Pulse spectral width 12.1 nm
PER > 15 dB
Beam delivery Polarization maintaining fiber