Laser system

A single arm laser system comprising:

• a first in-phase quadrature modulator (IQM), the first IQM configured to:
• receive a single frequency fibred laser beam from a frequency locked laser seed,
• generate a first single side-band frequency based on a carrier frequency of the single frequency fibred laser beam and suppress the carrier frequency, and
• output a first fibre laser beam having a single side-band suppressed carrier frequency;
• and
• a second IQM in line with the first IQM, the second IQM configured to:
• receive the first fibre laser beam from the first IQM,
• generate a second single side-band frequency based on the first single side-band frequency and maintain the first single side-band frequency as the carrier frequency, and
• output a second fibre laser beam having the first and second single side band frequencies;
• the single arm laser system being further configured to change the phase modulation of I and Q components in at least one of the first IQM and the second IQM so that at least one of the first and second single side band frequencies is changed.